- International Workshops on Piezoelectric MEMS

Transcription

. 2nd Interna*onal Workshop on Piezoelectric MEMS Materials ‐ Processes ‐ Tools ‐ Devices September 6‐7, 2011 EPFL ‐ Lausanne ‐ Switzerland Sponsored by 2nd Interna*onal Workshop on Piezoelectric MEMS Materials ‐ Processes ‐ Tools ‐ Devices We observe an increasing world wide interest in piezoelectric thin film MEMS devices. S;ll great efforts are needed to establish reproducible processing routes, reliable integra;on, op;mal poling procedures, standards in characteriza;on methods, op;mal device design, and reproducible opera;on condi;ons. A@er the success of the first workshop in 2010 at Aachen, we aim at bringing together again researchers and engineers from industry and academia to report and discuss on progress in in the field, and s;mulate exchange on experience and possible coopera;on. A combina;on of presenta;ons and discussions will give experts and researchers the chance to boost this promising and quickly developing market. The program includes many interes;ng and exci;ng talks on synthesis of piezoelectric thin films, on integra;on, on tes;ng and instrumenta;on, and on some of the many applica;ons that are foreseeable for piezoelectric MEMS. We hope this workshop is a great opportunity for companies working in thin film processing, microfabrica;on and MEMS to learn about the state of the art in piezoelectric MEMS based on ferroelectric and non‐
ferroelectric piezoelectric thin films. On behalf of the organizing commiLee Paul Muralt Chair (i) Workshop Organizers: Chair: P. Muralt Swiss Federal Ins;tute of Technology EPFL (Switzerland) Interna;onal advisory board and program commiLee: T. Matsushima Panasonic (Japan) T. Metzger
EPCOS (Germany) R. Polcawich US Army Labs (USA) H. Raeder SINTEF (Norway) S. Tiedke Aixacct (Germany) S. Trolier‐McKinstry Pennstate University (USA) K. Udayakumar
Texas Instruments (USA) Organizing commiLee: P. Muralt P. Ulrich (Sciprom) S. Tiedke (Aixacct) Local arrangements: L. Jin N. Chidambaran A. Mazzalai R. Matloub (ii) Invited Speakers Srowthi Bharadwaja, Roland Kessels, Takakiyo Harigai, Gilles Moulard,
Tuomas Pensala, Gianlucca Piazza, Ron Polcawich, Guus Rijnders, Frode Tyholdt, PennState University AIXACCT Panasonic TDK‐ECOS VTT University of Pennsylvania US Army Laboratories University Twente SINTEF Exhibitors aixACCT Systems GmbH SolMateS YOUTEC / DJK Europe (iii) September 6-7, 2011
2nd International Workshop on Piezoelectric MEMS
Materials - Processes - Tools - Devices
Program
Tuesday Morning
Time
Speaker
Title
0800-0900
0900
6 September
Registration
P. Muralt,
Welcome
EPFL
Chair: S. Trolier-McKinstry
0930
T. Harigai,
Piezoelectric Thin Films and Their Applications
inv
Panasonic Corporation
1005
M. Klee,
Piezoelectric thin films: A Technology platform for thin film
ultrasound transducer arrays
Philips Research
1025
1045
BREAK with exhibition and posters
Polcawich,
PiezoMEMS Technology for Enabling mm-Scale Robotics
US Army Research Lab.
1120
M. Schreiter,
Siemens
Corp.Techn.
1140
R. Vullers,
IMEC Holst Center
1200
P. Janphuang,
IMT-EPFL
1215
D. Remiens,
AG,
Piezoelectric MEMS based energy harvesting module for
wireless tire pressure monitoring
AlN and PZT Thin Films: Essential Ingredients for
Piezoelectric Energy Harvesters
MEMS Based Piezoelectric Harvesters: From Thick Sheet to
Thin Film Epitaxial Piezoelectric Materials
Performance of piezoelectric nanostructures
IEMN-CNRS
1230-1400
LUNCH with exhibition and posters
inv
Tuesday Afternoon
Time
Speaker
6 September
Title
Chair: T. Metzger
1400
G. Piazza,
Univ. of Pennsylvania
1435
1450
V. Felmetsger
Laterally Vibrating Micro and Nanomechanical Piezoelectric inv
Aluminum resonators for RF Communication and Chemical
Sensing
OEM Group, Inc.
Sputter Deposition of Piezoelectric AlN Thin Films on
Vertical Walls of Micromechanical Devices
G. Moulard,
Piezo-MEMS for RF applications
inv
TDK-EPC
1520-1545
1545
T. Pensala,
Piezo-actuated AlN-Si MEMS resonators and sensors
inv
VTT
1615
R. Matloub
Sc doped AlN thin films and their properties
LC-EPFL
1630
T. Baron
FEMTO-CNRS
FBAR filters for space application based on LiNbO3
membrane
1645
Piorra, A.
Lead
Free
Laser
Deposited
Thin
0.5(Ba0.7Ca0.3TiO3)–0.5(Ba(Zr0.2Ti0.8)O3)
University of Kiel
1700
S. Trolier-McKinstry
Microcontact Printing of PZT Films for MEMS
PennState University
1720
Adjourn
1900
DINNER at Beau Rivage (Ouchy)
Films
Of
POSTERS
Author
P1
P2
Title
T. Baron
FEMTO-CNRS
HBAR and their applications
N. Chidambaram
PZT thin film growth on insulators for interdigitated
electrode applications
EPFL-IMX
P3
6 & 7 September
V. Felmetsger,
OEM group
Reactive Magnetron Sputtering of Ultrathin Piezoelectric
S.Y. Kang
Samsung Elec.-Mech.
Influence of Temperature and O2 Flow Rate on the Structure
and Ferroelectric Properties of PZT Films Deposited by RF
Magnetron Sputtering
P5
A. Mathewson
Tyndall National Institute
Influences of Titanium Underlayer on (002) Oriented
Aluminium Nitride
P6
A. Mazzalai
EPFL-IMX
Conception of interdigitated electrodes based cantilever for
piezoelectric energy harvesting
E. Milyutin
Local polarity control of AlN thin films
P4
P7
EPFL-IMX
P8
P9
P10
M. Pham-Thi
Thales Research
Hyper Frequency properties of “3 inches-frozen capacitive
MEMS” with PZT thin films processed by sol-gel
T. Verdot
FEMTO
Active damping with a piezoelectric MEMS device
A. Vogl
SINTEF
Modelling of piezoelectric micromachined
transducers (pMUT) for medical use.
ultrasound
Wednesday Morning
Time
Speaker
7th September
Title
Chair: T. Matsushima
0840
G. Rijnders,
University of Twente
0910
A. Janssens,
All Oxide PiezoMEMS devices by Pulsed laser Deposition: inv
Properties of Clamped Piezoelectric Epitaxial PZT Thin
Films
SoLMateS
Introduction of new manufacturing technology for Piezo
(PZT) MEMS production
0930
S. Gariglio
University of Geneva
Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3 Thin Films on
Silicon:Growth and Physical Properties
0945
M. Kratzer,
Oerlikon PVD production solution for in-situ large scale
deposition of PZT films
Oerlikon Balzers
1000-1020
1020
R. Kessels,
Qualification and Quantification of piezoelectric MEMS
inv
AIXACCT
1050
Le Rhun, G.
CEA-LETI
1105
T. Kijima,
YOUTEC
1120
K.-A. Bui-Thi
Thales Research
1135
B. Malic
Josef Stefan Inst.
1150
S. S. N. Bharadwaja,
Pennstate University
1220-1400
Direct And Indirect Piezoelectric Characterization of PZT
Thin Films for MEMS Applications
Spin-Coat Technology of KNN Film Deposition with Oxygen
Pressurizing RTA
Properties of PMN-PT 65/35 thin film oriented -<011> at
radio frequency measured by coplanar waveguide
Influence of Solution Synthesis Conditions on Crystallization
and Properties of Functional Oxide Thin Films
Low Temperature Laser Processing of Ferroelectric Thin inv
Films
LUNCH with exhibition and posters
Wednesday Afternoon
Time
Speaker
7th September
Title
Chair: S. Tiedke
1400
F. Tyholdt,
SINTEF
1430
J. Phair
Polight
1445
S. Han
Samsung Electr.Mech.
1500
V. Cauda
Italian Inst.Techn.
1515
E. Mounier,
Yole Development
1530
1600
FP7 piezoVolume - High Volume Piezoelectric Thin Film inv
Production Process For Microsystems
Manufacture of Minature Tuneable Autofocus Lenses (TLens)
using Piezo MEMS
Wafer Level Poling of PZT thin films for MEMS Sensor
Devices
Effects of Nanoscale Confiment on Ferroelectric Properties:
Research Activity at the Center for Space Human Robotics
2010-2015 Market Analysis of PiezoMEMS
S. Trolier-McKinstry
Round table discussion:
PennState University
1650
1700
P. Muralt
Closing remarks
END
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Part I
T 6, S
O 
2nd International Workshop on Piezoelectric MEMS 2011
3
Takakiyo Harigai1 , Kazuki Komaki2 , Osamu Watanabe3 , Satoru Fujii1 , Yoshiaki Tanaka1 , Michihito
Ueda1 , Hideaki Adachi1 and Eiji Fujii1
1 Panasonic
Corporation, Japan
Elecronic Devices Co., LTD, Japan
3 Panasonic System Networks Co., LTD, Japan
2 Panasonic
Piezoelectric materials have been used for many kinds of devices such as actuators for inkjet printer
heads and sensors for angular velocity detection. Piezoelectric thin films formed on a Si substrate can
be processed into arbitrary configurations by standard micro-electro-mechanical systems (MEMS) processes. Performance enhancement and miniaturization are easier for a device with piezoelectric MEMS
than for a normal Si-MEMS device. The importance of the piezoelectric thin films is set to increase in
the future.
We developed a technique to form piezoelectric materials with perovskite structure on various substrates (MgO, Si, SUS). We grew Pb(Zr,Ti)O3 (PZT), Pb(Mg,Nb)O3 -Pb(Zr,Ti)O3 (PMN-PZT), and leadfree (Na,Bi)TiO3 -BaTiO3 (NBT-BT) thin films with the thickness of 3.0 µm by RF magnetron sputtering.
The growth of these thin films on MgO substrates was epitaxial, and the films on the Si or SUS were
oriented in (001) single direction. The piezoelectric coefficients d31 of these films were -150 pm/V for
PZT/Si, −225 pm/V for PMN-PZT/Si, and −155 pm/V for NBT-BT(100)/MgO.
The PZT films were applied to the sensor for angular velocity detection and the actuator of the ink
jet printer head. In the angular velocity sensor, PZT/Si was processed into a tuning fork configuration by
Si deep etching. This configuration by itself can vibrate the tuning fork and detect the angular velocity
at the same time. Thus, we succeeded in downsizing to 1/100 in volume compared with the conventional
product in which bulk PZT or quartz were arranged for three dimensions. This PZT/Si sensor is now
widely used for a position sensing in a car navigation system, and for shake compensation of a digital
camera. The ink jet head for industrial on-demand printers was also miniaturized by MEMS processing,
and realized printing resolution of 1, 200 dpi, and printing speed of 120 m/min.
The material properties of NBT-BT/MgO films with (001), (110), and (111) orientation were evaluated. From X-ray diffraction analyses, (001)-films had a tetragonal structure, and (111)-films had a
rhombohedral structure with no dependence on BT content. The maximum piezoelectric coefficients of
(001)- and (111)-films were obtained around morphotropic phase boundary (MPB) compositon of the
bulk. On the other hand, (110)-films were distorted to orthorhombic structure which does not form in
bulk state. The piezoelectric coefficient d31 of h110i directions was only −9 pm/V whereas d31 of h001i
directions was as high as −221 pm/V, comparable to PMN-PZT/Si. This work is promising to open an
important avenue for the improvement of piezoelectricity larger than that of the original material, and to
actual electromechanical devices using lead-free piezoelectric films.
4
Piezoelectric Thin Films: A Technology Platform for Thin Film
Ultrasound Transducer Arrays
M. Klee1 , R. Mauczok1 , C. van Heesch1 , H. Boots1 , W. Keur1 , M. de Wild1 and B. Op het Veld1
1 Philips
Research, Eindhoven
Piezoelectric thin film technologies get more and more relevance for miniaturized and integrated
actuators and transducers. Applications of miniaturized piezoelectric thin film devices are for example
sensors for proximity sensing or ultrasound transducer arrays for imaging.
A piezoelectric thin film technology platform has been developed, which processes lead based perovskite piezoelectric thin films by spin-on processing on thin film membranes. Making use of lithographic patterning, piezoelectric thin film ultrasound transducers have been realized, which are operating
in the d33 mode.
With the piezoelectric thin film platform, piezoelectric thin film ultrasound transducer arrays have
been realized, which dependent on the design are operating at frequencies of 50 KHz up to >10 MHz.
The piezoelectric thin film ultrasound transducer arrays are tested with respect to their performance.
The piezoelectric thin film membrane transducer arrays operating at 4 MHz and above show a very good
acoustic matching to water. This results in a bandwidth of the transducer arrays, which is equal or even
larger than 100%. The output pressure of the thin film piezoelectric ultrasound transducer arrays is linear
dependent from the applied voltage. These piezoelectric thin film ultrasound transducer arrays, due to
their similar operation conditions as traditional ceramic or single crystal ultrasound transducer, can be
operated with standard ultrasound machines. With the piezoelectric thin film ultrasound transducer
arrays with 32−42 elements ultrasound images of e.g. nylon wires with 0.12 mm diameter in a water
tank have been demonstrated.
The technology platform has also developed to realise ultrasound transducers operating at 50−100 KHz,
which have been successfully applied for proximity sensing.
5
R.G. Polcawich1 , J.S. Pulskamp1 , G. Smith1 , S. Bedair1 , T. Ivanov1 , R. Proie1 , R. Kaul1 , L. Sanchez1
and D. M. Potrepka1
1 US
Army Research Laboratory, Adelphi, MD, USA
Piezoelectric MEMS (PiezoMEMS) technology can enable integrated solutions for a wide variety
of applications including radio and cellular communications systems, biomedical, consumer electronics, and mm-scale robotics. Several piezoelectric materials are of interest for this technology. AlN
thin films lead the way in the front-end filtering technology with film bulk acoustic resonators (FBAR)
currently seeing heavy demand in cellular phones. Another material of keen interest is lead zirconate
titanate (PZT) especially for applications requiring low voltage, high stroke, high force actuators. As
part of an on-going research activity at the Army Research Laboratory, PiezoMEMS technology using
PZT thin films has been developed in the area of RF applications and mm-scale robotics. Specifically,
switches and relays covering a frequency space from DC to the high GHz have been demonstrated for
mechanical logic for low power embedded microcontrollers and high frequency phase shifters to enable electronically steerable antennas. PiezoMEMS actuators have also enabled two degree-of-freedom
actuators capable of matching the kinematic performance of insects at the mm-scale. These actuators
combined/integrated with low power sensors are being developed to enable mm-scale insect-inspired
robotic platforms. This presentation will focus specifically on the technologies of interest for mm-scale
robotics including advancements in actuator design, integrated sensing, integration of a mechanical logic
based microcontroller and performance will be presented with respect to bio-inspired microflight.
6
Piezoelectric MEMS Based Energy Harvesting Module for Wireless Tire
Pressure Monitoring
Matthias Schreiter1 , Dana Pitzer1 , Michael Schier1, Andreas Wolff1 , Ingo Kühne1 , Julian Seidel1 ,
Helmut Seidel2 and Alexander Frey1
1 Siemens
2 Saarland
AG, Corporate Technology, Munich, Germany
University, Chair of Micromechanics, Microfluidics/Microactuators, Saarbruecken,
Germany
Recently, MEMS-based energy harvesting systems have gained increasing importance to power
wireless sensor networks. While conventional batteries represent a simple and in many cases sufficient
power supply, dedicated energy harvesting solutions enable the implementation of sensor applications
where the operation conditions such as inaccessibility of the sensor in conjunction with long lifetime
requirements ban the usage of batteries.
This presentation gives an overview about the development of a demonstrator for a piezoelectric
MEMS based power generator for tire pressure sensors. Conventional battery driven systems are usually
mounted in the wheel rim. However, an arrangement on the inner liner of the tire would enable the
detection of additional parameters such as tire temperature, friction, wearout and side slip. This approach
implies stringent system requirements favouring an energy harvesting approach against a battery. This is
in particular a total system weight less than 7 grams and a minimum life time of 8 years. The harvesting
module needs to provide a minimum average power of 3 µW to power pressure sensor, microcontroller,
and RF-frontend. The energy harvesting module requires a system approach with adapted component
interfaces. The generator is based on a piezoelectric MEMS cantilever with a triangular shape which
enables high energy densities. Tire related forces during the tread shuffle passage are proposed to be
used for a pulsed excitation. To optimize the generator performance, piezoelectric thin films of different
materials (AlN, ZnO, and PZT) were evaluated with respect to relevant material characteristics such as
electro-mechanical coupling, dielectric constant and charge constant.
An analytical approach was implemented modeling the generator system as a whole which enables to
calculate the supplied average power and voltage depending on input parameters, cantilever geometries,
material parameters, and the interface circuit. The figure illustrates a thus obtained parameter space
for the generator design to meet requested output characteristics (generator area and piezoelectric thin
film parameters are fixed). First demonstrators were tested showing an electrical energy density of
35 nJ/mm2 .
This work is supported by the “Bundesministerium für Forschung und Entwicklung”, Germany,
and embedded in the project “ASYMOF–Autarke Mikrosysteme mit mechanischen Energiewandlern
für mobile Sicherheitsfunktionen” (reference 16SV3336).
2
International Workshop on Piezoelectric MEMS 2011
AlN and PZT Thin Films:
Essential
Ingredients
for Piezoelectric Energy Harvesters
7
Ruud Vullers, Madhusudhanan Jambunathan, Rene Elfrink, Christine de Nooijer, Rob Van Schaijk
imec/Holst
Centre
AlN and PZT Thin Films: Essential
Ingredients
for Piezoelectric Energy
Eindhoven, The Netherlands
Harvesters
The rapidly growing need for energy autonomy of wireless sensor nodes can only be well served by
1
Affiliation, Country
1 , Madhusudhanan
12 , Rene
using
various energy harvesting
technologies
in combination
energy storage
devices.1 ,The
market
Jambunathan
Elfrink1with
, Christine
de Nooijer
Rob
Van Schaijk1
Ruud Vullers
Affiliation,Country
acceptance of such solutions necessitates further cost reduction, which can be achieved by taking
advantage of MEMS
technology. Centre,
This paper
focuses onThe
the Netherlands
principle and thin film technology
1 imec/Holst
Eindhoven,
development for piezoelectric harvesting devices within imec / Holst Centre.
Aluminum nitride (AlN) was chosen as piezoelectric material for its material properties and its
The rapidly
growing
need
for energy
autonomy
ofAlN
wireless
sensor
can only with
be well
well-known
sputter
process.
For power
generation
is better
or at nodes
least comparable
otherserved by
piezoelectric
materials like,technologies
e.g. PZT [1]. in
A maximum
powerwith
of 225
µW has
been measured
an market
using various
energy harvesting
combination
energy
storage
devices.at The
acceleration of 2.5 g and a resonance frequency of 929 Hz (Fig 1a). The package of MEMS energy
acceptance of such solutions necessitates further cost reduction, which can be achieved by taking advanharvesters is essential both for reliability, in preventing excessive displacements, as well for
tage of MEMS
technology.
This
on [2].
the Therefore,
principle the
andreleased
thin film
technology
preventing
air damping
by paper
the usefocuses
of vacuum
MEMS
structuresdevelopment
are
for piezoelectric
harvesting
devices
within
imec/Holst
packaged
with a 6-inch
wafer level
process,
using twoCentre.
glass substrates with a cavity depth of 600 µm
(Fig. nitride
1b). Devices
and mass size
were fabricated
to cover properties
a 200-1200HZ
Aluminum
(AlN)with
wasdifferent
chosenbeam
as piezoelectric
material
for its material
and its wellfrequency range. The devices in vacuum have a large Q, and therefore a very narrow bandwidth of
known sputter
process.
For
power
generation
AlN
is
better
or
at
least
comparable
with
other
piezoelectric
less then 1%. This will hinder practical applications for single frequency input excitation, since it will
materials like,
e.g.difficult
PZT [1].
A maximum
powerto of
µW has
been measured
an acceleration
be very
to match
the resonance
the225
ambient
frequency.
Frequency at
tuning
is therefore of 2.5 g
essentialfrequency
[3]. This canofbe929
accomplished
adding
wing
like structures
next toenergy
the beamharvesters
(Figure 1c). In
and a resonance
Hz (Fig.by1a).
The
package
of MEMS
is essential
this case, PZT is the material of choice, for its higher piezoelectric constant compared to AlN.
both for reliability,
in preventing excessive displacements, as well for preventing air damping by the use
Modeling indicates that 10 to 20% tuning can be reached with PZT (Fig 1d). Progress in development
of vacuum of
[2].
Therefore,
thethin
released
MEMS
structures
are packaged
with
a 6-inch
waferonlevel
sputtering
of PZT
films and
the influence
of deposition
conditions,
anneal
and poling
RF process,
and pulsed
DC sputtered
willdepth
be discussed.
using two glass
substrates
with alayers
cavity
of 600 µm (Fig. 1b). Devices with different beam and mass
In case of shock
induced
vibration harvesting,
the seismic
massThe
is excited
withina mechanical
shocka large Q,
size were fabricated
to cover
a 200-1200
Hz frequency
range.
devices
vacuum have
after which the mass will “ring-down” at its natural resonance frequency [4]. During the ring-down
and therefore
a very
narrow
bandwidth
less
then 1%.
Thisfactor,
will hinder
applications
period,
whose
duration
increases of
with
increasing
quality
part of practical
the mechanical
energy isfor single
frequency input
excitation,
since
it will
be verymaxima
difficult
to amatch
the resonance
to the
ambient frequency.
harvested.
The output
power
has multiple
with
bandwidth
of about 100%
each.Therefore,
main is
advantage
of this
principle[3].
is that
the frequency
match condition by
is not
relevant.
In case
Frequency the
tuning
therefore
essential
This
can be accomplished
adding
wing
likeofstructures
application inside car tires, repetitive high amplitude shocks occurs every rotation. A high quality
next to the factor
beamharvester
(Fig. 1c).enables
In thiscontinuous
case, PZT
is the material of choice, for its higher piezoelectric constant
power generation of a few tens of µW, sufficient to power a
compared to
AlN.
Modeling
indicates
that
10
to 20% tuning can be reached with PZT (Fig. 1d). Progress
wireless sensor node.
in development of sputtering of PZT thin films and the influence of deposition conditions, anneal and
References
poling on RF
pulsed
DC
layers
will be discussed.
[1] R.and
Elfrink,
et al., conf.
proc.sputtered
PowerMEMS 2008,
p.249-252
[3] D. Zhu et al., Meas. Sci. Technol. 21 (2010)
[2] R. Elfrink, et al, IEEE IEDM2009, pp. 543-546
[4] B. Cavallier, et al, IEEE Ultrason. Symp. 2005, p.943-945
b)
c)
a)
d)
Figure 1 : a) Power output for AlN piezoelectric energy harvester b) Wafer level packaged device c) Frequency tuning design
for a piezo electric, by adding overhanging PZT 〝wings〝 (grey areas) next to the beam d) the change of the frequency that
a) Power
can beoutput
reached for AlN piezoelectric energy harvester b) Wafer level packaged device c) Frequency tuning
Fig. 1:
design for a piezo electric, by adding overhanging PZT “wings” (grey areas) next to the beam d) the change of the
frequency that can be reached
In case of shock induced vibration harvesting, the seismic mass is excited with a mechanical shock
after which the mass will “ring-down” at its natural resonance frequency [4]. During the ring-down period, whose duration increases with increasing quality factor, part of the mechanical energy is harvested.
The output power has multiple maxima with a bandwidth of about 100% each.Therefore, the main advantage of this principle is that the frequency match condition is not relevant. In case of application
inside car tires, repetitive high amplitude shocks occurs every rotation. A high quality factor harvester
enables continuous power generation of a few tens of µW, sufficient to power a wireless sensor node.
[1] R. Elfrink, et al., conf. proc. Power MEMS 2008, pp. 249-252. [2] R. Elfrink, et al., IEEE IEDM2009, pp.
543-546. [3] D. Zhu et al., Meas. Sci. Technol. 21 (2010). [4] B. Cavallier, et al., IEEE Ultrason. Symp. 2005,
pp. 943-945.
8
MEMS Based Piezoelectric Harvesters: From Thick Sheet to Thin Film
Epitaxial Piezoelectric Materials
P. Janphuang1 , D. Isarakorn1 , D. Briand1 , S.Gariglio2 , A. Sambri2 , J.-M. Triscone2 , F. Guy3 , J.W.
Reiner4 , C.H. Ahn4 and N.F. de Rooij1
1 Ecole
Polytechnique Fédérale de Lausanne (EPFL), Switzerland
2 University of Geneva, Switzerland
3 Engineering school of Geneva, Switzerland
4 Yale University, USA
nd
This work demonstrates 2MEMS
based vibration piezoelectric energy harvesters. The characteristics
and performances
of two different energy harvesting devices based on thick PZT sheet and epitaxial
References
[1] P. film
D. Mitcheson,
et al., Proceedings
of the IEEE,
96, pp. 1457-1486,
2008.
PZT thin
have been
investigated.
The vol.
harvester
made by
bonding a thick PZT sheet produced a
[2] E. E. Aktakka et al., IEE IEDM
2007, San Francisco, pp. 31.5.1-31.5.4.
3
2
power[3]density
of 2.41
µW/mm
. While with 2009,
the device
based
epitaxial PZT thin film reached a
G. A. Ardila
Rogríguez
et al.,/g
Proc.PowerMEMS
Washington
DC,on
pp.an
197-200.
3 /g2 . To compare our device performances, the Figure of Merit defined by
power[4]density
of and
85 µW/mm
S. Roundy
P.K. Wright,
Smart Mater. Struct. 13 (2004) pp. 1131-1142.
[5] S. Trolier-Mckinstry
andaccount
P. Muralt,(Table
J. Electroceramics.
12 (2004), pp. 7-17.
Mitcheson
[1] is taken into
1).
[6] D. Shen et al., J. Micromech. Microeng., 18 (2008) 055017.
1.6
1.2
1.8
1.2
0.8
0.6
0.4
0.0
0.0
1000
0
200
400
600
800
Load resistance (kΩ)
Figure 2. The output power (Prms) and output
voltage (Vrms) as a function of resistive load at
input vibration of 0.1g and 145 Hz.
Power (μW g-2)
Output power (μW)
2.4
Voltage output (Vrms)
Power (μW)
Voltage (Vrms)
16
Current (μA g-1)
2.0
3.0
Figure 4. Optical image of an epitaxial PZT
harvester (active volume of 0.153 mm3). The inset
shows the Si mass on the backside of the cantilever.
120
Voltage (V g-1)
Figure 1. Optical image of a thick PZT harvester
(active volume of 90 mm3) mounted on the shaker.
The accelerometer is used to determine the
acceleration level.
0.8
Theoretical
Experimental
12
8
4
0
5
10
15
20
25
Theoretical
Experimental
80
40
0
0
5
10
15
20
25
Theoretical
0.6
Experimental
0.4
0.2
0.0
0
160
Power (μW)
10
15
20
25
Load resistance (kΩ)
Figure 5. Theoretical and experiment power,
current, and voltage as a function of resistive load
for the epitaxial PZT harvester.
120
80
Table 1. Performances of our devices based
volume figure of merit (FoMv) proposed by
Mitcheson et al. [1].
40
0
130
5
Power @ 218 kΩ
135
140
145
Frequency (Hz)
150
155
Piezoelectric
type
Figure 3. The output power across 218 kΩ as a Thick PZT
sheet -130 µm
function of frequency at input acceleration of 1.0g
Epitaxial PZT 0.5 µm
Vol.
(mm3)
Input acc.
(m/s2)
fr
(Hz)
Power FoMv
(µm)
(%)
90
0.98 (0.1g)
9.80 (1g)
145
141
2.17
157.74
0.50
3.73
0.153
0.98 (0.1g)
9.80 (1g)
2302
2302
0.13
13
9.28
92.78
9
Bulk PZT ceramics present high electromechanical coupling which is highly desirable in piezoelectric energy harvester. Several piezoelectric cantilevers based energy harvester with bulk PZT have been
proposed and investigated in recent years [2,3]. In our work, the thick PZT sheet was bonded onto silicon cantilever using a spin coated UV activated epoxy. The harvester structure was designed to have
resonant frequency lower than 200 Hz in order to be matched by the ambient vibrations in environment [4]. Fabricated thick PZT harvester (Fig.1) produced an average output power of 2.17 µW at 0.1 g
(145 Hz) (Fig. 2) and reached to 157.74 µW at 1.0 g (141 Hz) with an optimal resistive load of 218 kΩ
(Fig. 3). In order to achieve low resonant frequency structure, a high mass with a high volume is required in thick PZT harvester, resulting in low power density (2.41 µW/mm3 /g2 ). Moreover, wafer level
manufacturability is limited with the transfer of the PZT sheet and the mass onto the silicon structure.
Therefore, piezoelectric thin films are promising [5,6] to develop a low volume harvesters using wafer
level manufacturing processes.
In this matter, we are developing MEMS scavengers using an epitaxial Pb(Zr0.2 Ti0.8 )O3 thin films
grown on silicon through oxide layers. The PZT with a composition of Zr/Ti=20/80 is chosen for its
good lattice match with oxide layers and for the highest power generation figure of merit due to a high
piezoelectric coefficient and a low dielectric constant. The power generated from the epitaxial PZT
harvester (Fig. 4) measured at its resonant frequency (2.3 kHz) are 13 µW/g2 , 60 µA/g and 0.28 V/g for
an optimal resistive load of 4.7 kΩ (Fig. 5). The epitaxial PZT harvester can gererate high power and
current while maintaining low resistive load, which is favorable for impedance matching with electronic
devices.The eptixial PZT harvester still needs to be optimized by changing on the device geometry to
increase its ouput voltage to match with most of rectifying devices. An improved design included lower
resonant frequency, higher output voltage and power will be presented.
[1] P. D. Mitcheson, et al., Proceedings of the IEEE, vol. 96, pp. 1457-1486, 2008.
[2] E. E. Aktakka et al., IEE IEDM 2007, San Francisco, pp. 31.5.1-31.5.4.
[3] G. A. Ardila Rogrı́guez et al., Proc. Power MEMS 2009, Washington DC, pp. 197-200.
[4] S. Roundy and P.K. Wright, Smart Mater. Struct., 13 (2004) pp. 1131-1142.
[5] S. Trolier-Mckinstry and P. Muralt, J. Electroceramics. 12 (2004), pp. 7-17.
[6] D. Shen et al., J. Micromech. Microeng., 18 (2008) 055017.
10
Performances of Piezoelectric Nano Structures
D. Rémiens1 , J. Costecalde1 , D. Deresmes1 , D. Troadec1 and C. Soyer1
1 IEMN-UVHC-DOAE-UMR
8520, Université des Sciences et Technologies de Lille, Bat. P3, BP
60069, 59652 Villeneuve d’Ascq Cedex, France
Piezoelectric nano-structures (islands of dimensions in the lateral size range 50–500 nm) have been
fabricated by Focused Ga3+ Ion Beam (FIB) etching on PbZr0.54 Ti0.46 O3 thin films obtained by magnetron sputtering. The degradation induced by the etching process is investigated through the evolution
of electromechanical activity measured by means of local piezoelectric hysteresis loops produced by
Piezo-response Force Microscopy. The analysis of surface potential is performed by Kelvin Force Microscopy and the measurement of current-voltage curves is carried out by Conducting Atomic Force
Microscopy. Two kinds of structures, namely one based on crystallized films and the other based on
amorphous ones, were studied. In this latter case, the amorphous films are post-annealed after etching
to obtain crystallized structure. For the structures based on the crystallized and then etched films, no
piezoelectric signal was registered that evidences a serious degradation of material induced by Ga3+
ion implantation. For the structures based on the films etched in amorphous state and then crystallized
the piezo response signal was near to that of the reference films (crystallized and not etched) whatever
were the ion dose and the island dimensions. Even for very small lateral size (50 nm), no size effect was
observed. All these results will be presented at the workshop.
11
Laterally Vibrating Micro and Nanomechanical Piezoelectric Aluminum
Nitride Resonators for RF Communications and Chemical Sensing
Gianluca Piazza1
1 University
of Pennsylvania, Philadelphia, PA, USA
Miniaturized resonators capable of operating at various frequencies on the same substrate have
gained interest as emerging technologies for addressing the specific needs of next generation radio
frequency (RF) communication and sensing systems. Large scale integration of micro and nanoscale
resonant mechanical devices will yield unprecedented platforms capable of low power and dynamic reconfiguration of radio links as well as the development of portable and disposable ÒnosesÓ characterized
by very low limit of detection and high sensitivity to complex volatile organic chemical mixtures.
This talk presents the latest advancements undergoing at the University of Pennsylvania in the development of a very promising class of these micro and nanomechanical resonators, namely laterally
vibrating (contour-mode) piezoelectric aluminum nitride resonators. These devices have shown the ability to operate from few MHz up to several GHz with low motional impedances that can be readily
interfaced with electronics and mechanical quality factors in excess of 1,000 and up to 4,000 in ambient
conditions. Switchable banks of resonators and filters for frequency synthesis and low energy signal
processing have been experimentally demonstrated. The impact of these multi-frequency low phase
noise oscillators and low loss filters goes well beyond providing a miniaturized replacement for existing
components; massive parallelism of these devices will infact enable new archicetures such as congnitive
radios.
Extreme miniaturization of the thickness of these AlN devices (50-250 nm) has benefited the demonstration of highly sensitivity and low limit of detection resonant chemical sensors. The reduced mass
and large surface area in conjuction with high Q at 100 s of MHz make these AlN nanoplates the ideal
candidates for the synthesis of very low power and portable sensors. These resonators have been arrayed
and functionalied with single-stranded DNA to yield an electronically controlled nose capable of identifiying sub-part per billion (ppb) concentrations of Dinitrotoluene (DNT) and 100 s of ppb of Dimethyl
Methylphosphonate (DMMP).
In summary, this talk will offer an overview of the potentials of this miniaturized AlN resonator
technology and highlight how it will likely impact the More than Moore evolution of the semiconductor
industry.
2
12
Sputter Deposition of Piezoelectric AlN Thin Films on Vertic
2nd International Micromechanical
Workshop on Piezoelectric MEMS
2011
Devices
Valeriy Felmetsger1, Roozbeh Tabrizian2 and Farrokh Ayazi2
Sputter Deposition of Piezoelectric AlN Thin Films on Vertical Walls of
1
Micromechanical Devices
OEM Group Incorporated, USA
2
Georgia
FarrokhInstitute
Ayazi2 of Technology, USA
Valeriy Felmetsger1 , Roozbeh Tabrizian2 and
1
Group
We present a OEM
novel
AlNIncorporated,
thin film USA
processing technique that benefits from the
2 Georgia Institute of Technology, USA
piezoelectric effect as well as large transduction area provided by the sidewalls of silico
Compared to FBARs where resonance frequency of the device is mainly a function of
We present a novel AlN thin film processing technique that benefits from the efficient longitudinal
and substrate thicknesses, the resonance frequency of AlN-on-sidewall resonators is m
piezoelectric effect as well as large transduction area provided by the sidewalls of silicon microstructures
lateral dimentions of a relatively thick Si microstructure. This implies that dev
[1]. Compared to FBARs where resonance frequency of the device is mainly a function of the piezofrequencies
spreading
acrossfrequency
a wide frequency
spectrum
can beis implemented
on the
electric film and substrate
thicknesses,
the resonance
of AlN-on-sidewall
resonators
mainly
lithography.
defined by the lateral dimentions of a relatively thick Si microstructure. This implies that devices with
resonance frequencies spreading across a wide frequency spectrum can be implemented on the same
In this study, the Mo/AlN/Mo film stacks were deposited by dual-target S-gun magnetro
substrate using lithography.
structures
with
a deposited
sidewall by
height
of 20S-gun
µm patterned
Si exdevice layer of 1
In this study, theresonator
Mo/AlN/Mo
film stacks
were
dual-target
magnetronsinonto
wafers.
Pre-deposition
plasma
of the substrate
andlayer
thinofAlN
seed layer were e
perimental resonator
structures
with a sidewallrfheight
of 20etch
µm patterned
in Si device
100-mm
diameter SOI wafers.
Pre-deposition
rf plasma
etch of the substrate
and thin
AlN seeddeposited
layer were by
em-a dc powered S
growth
of smooth
and well-textured
Mo bottom
electrode
ployed to stimulate biasing.
growth of An
smooth
and well-textured
deposited by afor
dc powered
alternating
currentMo
(40bottom
kHz)electrode
S-gun magnetron
reactive sputtering en
S-gun with rf substrate
biasing.
An
alternating
current
(40
kHz)
S-gun
magnetron
for
reactive
sputtering
long-throw, low-pressure conditions with energetic particle bombardment thus en
enabled AlN growthcoverage
in long-throw,
low-pressure
with energetic
particle bombardment thus
and formation
of conditions
strong texture
in the film.
ensuring effective wall coverage and formation of strong texture in the film.
The films were characterized by x-ray dif
electron microscopy. 700-nm-thick AlN fil
of the resonator exhibited single (0002) cr
rocking curve full-width at half-maximum o
and Mo film thicknesses were approx
thicknesses and were continuous on the
sidewalls.
The efficiency of the sidewall process for tr
devices was investigated using one-port wi
silicon bulk acoustic resonators.
[1] R. Tabrizian and F. Ayazi, The Proceedings of the 16th International Conference o
Actuators and Microsystems (Transducers 2011), Beijing, China, June 2011, pp. 1520-1
The films were characterized by x-ray diffraction and scanning electron microscopy. 700-nm-thick
AlN films on the top surface of the resonator exhibited single (0002) crystal orientation with rocking
curve full-width at half-maximum of 1.65◦ . Sidewall AlN and Mo film thicknesses were approximately
half of top thicknesses and were continuous on the entire surface of the sidewalls.
The efficiency of the sidewall process for transduction of MEMS devices was investigated using
one-port width-extensional-mode silicon bulk acoustic resonators.
[1] R. Tabrizian and F. Ayazi, The Proceedings of the 16th International Conference on Solid-State Sensors,
Actuators and Microsystems (Transducers 2011), Beijing, China, June 2011, pp. 1520-1523.
13
New Trends in Piezoelectric Devices for RF Application in Mobile Phones
Moulard Gilles1 and Metzger Thomas1
1 TDK
EPC, Munich, Germany
The market requirements in the field of Mobile Phones induce a continuous improvement of piezo
material for Radio-Frequency acoustic waves devices. Currently, only RF SAW (Surface Acoustic Wave)
/ BAW (Bulk Acoustic Waves) duplexers fulfill all of the stringent customers requirements such as small
devices RF filters with large bandwidths, low insertion losses, low temperature frequency drift and low
price.
This presentation shows how the development of new SAW/BAW manufacturing process blocks
are consistent with the current and future market requirements. High quality piezoelectric material is
essential in BAW technology to achieve filter performances and especially a large bandwith in the GHz
range. But the piezoelectric and acoustic properties of the piezo layer are also largly influenced by the
choice of the electrode material. Each change in the layer stack configuration leads also to process
integration issues that have to be solved before being implemented in production.
New process blocks have been developed for SAW technology, mainly to improve the power durability and to reduce the TCF of the devices in order to fullfil the market requirements.
Today, due to the various different processes which have been developed, we are able to answer
the customer requirements for each duplexer bands. The mix process allows us to propose a hybrid
BAW/SAW duplexer which is already in mass production.
14
Piezoactuated AlN-Si MEMS Resonators and Sensors
Tuomas Pensala1
1 VTT,
Finland
MEMS resonators have been studied for a long time as a potential replacement for quartz crystals in
oscillators and timing circuits. High performance resonators have been demonstrated over the years and
finally also entered the market recently, most of the work being based on electrostatic actuation.
The drawbacks of the electrostatic actuation include the need for a large DC bias voltage and/or
very narrow gaps in the actuator structures, combined with small actuation force. Thin film piezoelectric structures have been employed by several groups to overcome the drawbacks of the electrostatic
actuation, with the cost of e.g. increase in the MEMS fabrication process complexity.
Piezoactuation is compared to electrostatic actuation from the point of view of device physics, fabrication processes, device performance, yield and repeatability etc. Obtained advantages and issues
arising from the utilization of piezoelectric actuation in resonators are discussed.
Piezoactuated wafer level packaged MEMS resonators for the >10 MHz range fabricated at VTT
are presented and a review of the state of the art is performed.
The focus of the paper is on AlN-Si based resonator devices, but a comparison is made to other
possible piezomaterials and applications of piezo-MEMS.
15
Electromechanical Properties of Al0.9 Sc0.1 N Thin Films Evaluated at
2.2 GHz: Film bulk acoustic resonators
Ramin Matloub1 , Alvaro Artieda1 , Cosmin Sandu1 , Evgeny Milyutin1 , and Paul Muralt1
1 Ceramics
Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Switzerland
Since a few years, aluminum nitride (AlN) thin films have become a standard material for RF filters
in mobile phones. It is mostly used in duplex filters working around 2 GHz composed of thin film
bulk acoustic wave resonators (TFBAR) connected in ladder type circuits. Pure AlN thin films were
found to have maximal d33,f piezoelectric coefficients of 5.3 pm/V. The coupling coefficients of TFBAR’s
amounts to maximally k2 =6.5 % considering standard materials parameters. Such a value is sufficient
for covering the needs of current filter requirements for mobile phones. However, there are other filters
types and applications that would require larger coupling factors in order to achieve larger bandwidths.
Recently it was shown that Al substitution by Sc allows for an increase of the piezoelectric response.
We prepared polycrystalline (001)-textured Al0.88 Sc0.12 N thin films by reactive, pulsed, direct current
magnetron sputtering to measure all relevant properties for TFABR resonators. The target was a 200 mm
diameter, 6 mm thick plate of an Al0.9 Sc0.1 alloy of 99.9% purity and exact composition Al/Sc of 89.76
at. %/10.23 at. %. Selected area electron diffraction calibrated with the XRD (002) peak yielded a and c
lattice parameters of 3.11 and 5.01 Å, respectively. The c/a ratio decreased to 1.575 from 1.601 of pure
AlN. The unit cell volume increased by 5%. Energy dispersive analysis of x-ray emission in the TEM
revealed that 12 at. % of Al atoms were substituted by Sc, indicating a higher sputter or transfer yield for
Sc. The microstructure of the films as investigated by means of TEM is very close to the known picture
of fiber-type T-zone growth of good AlN thin films for TFBAR’s. The clamped piezoelectric coefficient
d33,f as measured by double side interferometry increases to 7.7 to 8.0 pm/V. TFBAR resonators with
fundamental resonance at 2.2 GHz have been fabricated and characterized. The sound velocity in AlScN
was derived by means of 2d finite element modeling of the layer stack, allowing for discrimination of
loading effects by the electrodes. The value of 10’300 m/s is clearly lower than in pure AlN (11’000 m/s).
A parasitic resistance was taken into consideration through application of an equivalent circuit model.
As a result of these procedures we obtained k2 to 11 % and Q factor of 270 for the complete resonator,
furthermore a dielectric constant of 12, and a dielectric loss tangent of 0.5% (both @2.2 GHz). The
E
stiffness constants cD
33 and c33 were derived as 345 and 320 GPa. The resonance frequency temperature
drift of 26.1 ppm/K was found to be about the same as for pure AlN. The evolution of piezoelectric
constant e33 , the dielectric constant, and the stiffness constant cE33 were found to be close to the values
predicted by ab-inito calculations.
16
FBAR Filters for Space Application Based on LiNbO3 Membrane
T. Baron1 , M. Chatras2 , S. Ballandras1
1 FEMTO-ST
UMR 6174 CNRS-UFC-ENSMM-UTBM, ENSMM, 26 Chemin de l’Epitaphe, 25030
Besançon Cedex
2 Xlim, UMR 6172 CNRS-Université de Limoges, Limoges, France
Film bulk acoustic resonator (FBAR) usually use for filter application, can be used to address
aerospace filter application which need large band. Then, it needs to use piezoelectric material with
high electromechanical coupling coefficient. So we use LiNbO3 cut YXl/36 which have coupling coefficient for longitudinal mode of 37.5%.
Conception of this kind of large band filter is based on ladder architecture with three FBAR resonators. Firstly, we compute thickness of LiNbO3 with our own software to achieve frequency required
for elementary resonator. Secondly, we compute and optimise the ladder filter. The ladder filter shows a
widthband of 22% at 300 MHz.
Conception of such devices needs to have membrane of LiNbO3 with bottom and top electrode. To
achieve this structure, we based our process fabrication on gold bonding silicon and LiNbO3 wafer and
lapping/polishing step of LiNbO3 wafer, as described previously last year [1,2]. Contrary to previous
works, we add different steps of process before the bonding step to structure the bot-tom electrode
on titanium and membrane. The bonding step is achieve with deep structured silicon wafer, bottom
electrode on LiNbO3 and structured gold in both wafer. We achieve a membrane on LiNbO3 of 11 µm
as showed in Fig. 1.
Fig. 1: Resonator with 11 µm thickness of LiNbO3 .
Electrical characterization shows filter behaviour of FBAR devices. Packaging of these devices allows us to test power, thermal behaviour.
[1] T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping” EFTF April 2010, Noordwijk.
[2] T. Baron et al., “Temperature compensated Radio-Frequency Harmonic Bulk Acoustic Resonators Pressure
Sensors”, IUS October 2010, San Diego.
17
Lead Free Laser Deposited Thin Films of
0.5(Ba0.7 Ca0.3 TiO3 )-0.5(Ba(Zr0.2 Ti0.8 )O3 )
André Piorra1 , Viktor Hrkac1 , Lorenz Kienle1 and Eckhard Quandt1
1 Institute
for Material Science, Faculty of Engineering, University Kiel, Germany
The materials of choice for piezoelectric applications and so far best investigated piezoelectric materials are bulk or thin film ceramics based on lead zirconate titanate (PZT). However, there is an increasing and strong interest in lead-free ferroelectric materials due to the toxicity of lead. A promising composition with piezoelectric properties comparable to PZT were found in 0.5(Ba0.7 Ca0.3 TiO3 )0.5(Ba(Zr0.2 Ti0.8 )O3 ) (BCZT).
In this work ferroelectric lead-free BCZT thin films of this composition were successfully deposited by pulsed laser deposition (PLD) on Pt/TiO2 /SiO2 /Si substrates using a ceramic BCZT target
prepared by conventional solid state reaction. The target material itself showed a piezoelectric coefficient d33 =600 pm/V. The (111) textured up to 1800 nm thick films exhibited a clamped piezoelectric
response up to 90 pm/V and a dielectric coefficient of εr = 2000 at room temperature and are among the
highest reported for lead-free piezoelectric thin films. In this presentation, the piezo- and ferroelectric
properties of BCZT thin films will be discussed in the framework of PLD deposition parameters, the
influence of the used substrates and its resulting microstructure.
Funding via the DFG Collaborative Research Center SFB 855 “Magnetoelectric Composites–Future
Biomagnetic Interfaces” is gratefully acknowledged.
18
Aaron Welsh1 , Michael Hickner1 and Susan Trolier-McKinstry1
1 Department
of Materials Science and Engineering, The Pennsylvania State University
The ability to pattern piezoelectric thin films without damage is crucial for the development of
microelectromechanical systems (MEMS). Many patterning techniques change the crystallinity or stoichiometry, which degrades the dielectric and piezoelectric properties of the material, with potential
long-term consequences in reliability. This research is focused on shifting the paradigm away from
subtractive patterning techniques by exploring direct patterning of complex oxides through microcontact printing. This process utilizes an elastomeric stamp to transfer a chemical solution precursor of a
piezoelectric material directly onto a substrate in a desired pattern. Subsequent heat treatment is used to
crystallize the material.
One key factor that governs the quality of the patterned shape is the wetting of the PbZr0.52 Ti0.48 O3
(PZT) solution “inked” onto the surface of the elastomeric stamp. The most commonly used stamp material for microcontact printing is polydimethylsiloxane (PDMS). This material has excellent mechanical
properties for this application. However PDMS has a hydrophobic surface, while the 2-methoxyethanol
(2-MOE) based PZT solution is a polar solvent. Therefore poor wetting between the solution and the
stamp leads to poor pattern transfer. Two routes are being explored to improve this. The first is subjecting the PDMS stamps to an oxygen plasma ashing treatment which converts the surface of the stamp to
a temporary hydrophilic surface. The second is to use a polyurethane (PU) composite stamp that has an
inherently hydrophilic surface.
It was found that oxygen plasma ashing the surface of the PDMS stamps leads to well defined pattern
transfer of a single 125 nm layer of PZT solution. Similarly, PU stamps enable both excellent pattern
transfer and multiple printing cycles without degradation in definition of the features. Lateral feature
sizes of the patterned PZT varied from 500 µm to 5 µm. On crystallization, the patterned features formed
perovskite PZT without deleterious second phases. The patterned features have comparable electrical
properties to those of continuous PZT films of similar thicknesses, with permittivities of >1000 for
thicknesses above 400 nm. The hysteresis loops are well formed, without pinching of the minor loop.
The piezoelectric response of the patterned features produced an e31,f of −5 to −7 C/m2 . This indicates
that the microcontact printing process does not adversely affect the PZT crystallization.
Part II
T 6, S
P
21
HBAR and Their Applications
T. Baron1 , E. Lebrasseur1 , G. Martin1 , B. François1 , V. Petrini1 , S. Ballandras1
1 FEMTO-ST
UMR 6174 CNRS-UFC-ENSMM-UTBM, ENSMM, 26 Chemin de l’Epitaphe, 25030
Besançon Cedex
High-overtone Bulk Acoustic Resonators (HBAR) have received a strong interest for many years.
Various developments have been particularly achieved using Quartz and AlN materials. With the devel2nd materials
Internationalwhich
Workshop
on Piezoelectric
2011 electromechanical coefficient, new applications
opments of new
present
higherMEMS
coupling
can be address. The fabrication of the proposed HBAR is based on bonding and lapping of two wafers.
Thin piezoelectric film presentes strong coupling coefficient, as described previously [1,2]. This fabrication method
allows us to choose material for piezoelectric layer and substrat layer to address differents
T. Baron1, E. Lebrasseur1, G. Martin1, B. François1, V. Petrini1, S. Ballandras1
applications.
1
For exemple,
one possibility
to control the Temperature Coefficient of Frequency (TCF) of HBAR.
FEMTO-ST
UMR 6174 is
CNRS-UFC-ENSMM-UTBM
ENSMM,
26
Chemin
de
l'Epitaphe,
25030
Cedex
The famous Campbell & Jones method
[3] Besançon
has been
used here for predicting the TCF of any mode
of aBulk
given
HBAR
and hence
to have
determine
of many
material
which this parameter can be
High-overtone
Acoustic
Resonators
(HBAR)
receivedconfigurations
a strong interest for
years.for
Various
developments
have
been
particularly
achieved
using
Quartz
and
AlN
materials.
With
the
developments
magnified or minimized. By this way, we can address applications which ofneed intrinsic temperature
new materials which present higher coupling electromechanical coefficient, new applications can be address.
compensation
or on
theiscontrary
ofwafers.
temperature.
The fabrication
of the proposed
HBAR
based on maximum
bonding and sensibility
lapping of two
Thin piezoelectric
film
presentes
strong
coupling
coefficient, as described previously 1,2.
This fabrication method allows us to
choose material for piezoelectric layer
and substrat layer to address differents
applications.
For exemple, one possibility is to
control the Temperature Coefficient of
Frequency (TCF) of HBAR. The
famous Campbell&Jones method 3 has
been used here for predicting the TCF
of any mode of a given HBAR and
hence to determine configurations of
material for which this parameter can be
magnified or minimized. By this way,
we can address applications which need
intrinsic temperature compensation or
on the contrary maximum sensibility of
Fig. 1: Experimental measurements of a mode of a HBAR
temperature.
◦ LiNbO on (YXlt)/34◦ /90◦ Quartz
built on
on (YXlt)/34°/90°
The possibility
to
combine
various
3 built
Fig. 1: Experimental measurements
of a(YXl)/163°
mode of aLiNbO
HBAR
on (YXl)/163Quartz
3
located in the ISM band
materials and to include manufacturing
located
in
the
ISM
band.
steps before and after bonding and
lapping process, allow us to target
4
1
various applications
as oscillator
pressure sensor
, temperature
sensor,
and so on.manufacturing steps before and after
Thesuch
possibility
to , combine
various
materials
andfilter,
to include
1
T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping” Proc.of the IEEE EFTF April 2010
2
bonding
and lapping
process,
allow us toharmonic
target various
applications
asthe
oscillator [4], pressure senT. Baron et
al., Temperature
compensated
radio-frequency
bulk acoustic
resonators,such
Proc.of
IEEE IFCS,sor
pp. [1],
652 –temperature
655, 2010
sensor, filter, and so on.
[1] T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping”, Proc.of the IEEE EFTF April 2010.
[2] T. Baron et al., “Temperature compensated radio-frequency harmonic bulk acoustic resonators”, Proc.of the
IEEE IFCS, pp. 652-655, 2010.
[3] J.J. Campbell, W.R. Jones, “A method for estimating crystals cuts and propagation direction for excitation of
piezoelectric surface waves”, IEEE Trans. On Sonics and Ultrasonics, Vol. 15, pp. 209-217, 1968.
[4] T. Baron et al., “RF oscillators stabilized by temperature compensated HBARs based on LiNbO3 /Quartz
combination”, Proc.of the IEEE IFCS-EFTF, 2011.
Effective piezoelectric coefficients of PZT thin films for energy harvesting with interdigitated electrodes 2nd International
Workshop on Piezoelectric MEMS 2011
Ɨ
Nachiappan Chidambaram , Andrea MazzalaiƗ & Paul MuraltƗ Ɨ
Laboratoire de Céramique Effective Piezoelectric Coefficients
of PZT Thin Films for Energy
Ecole Polytechnique Fédérale de Lausanne, EPFL Harvesting with
Interdigitated Electrodes
Lausanne, Switzerland. Mazzalai1 , Paul Muralt1
Nachiappan Chidambaram1 , Andrea
August 24, 2011 1 Ceramics Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Switzerland
Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) (figure 1 (a)) thin films play Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) (figure 1 (a)) thin films
an increasingly important role for two reasons: first, such a configuration generates higher voltages play an increasingly important role for two reasons: first, such a configuration generates higher voltages
than parallel plate capacitor type electrode (PPE) structures, and second, the application of an than parallel plate capacitor type electrode (PPE) structures, and second, the application of an electric
electric field leads to a compressive stress component, contrary to PPE structure, which results in field leads to a compressive stress component, contrary to PPE structure, which results in tensile stress.
tensile stress. Ceramics tend to crack at relatively moderate tensile stresses and this means that with Ceramics tend to crack at relatively moderate tensile stresses and this means that with IDEs one can
IDEs one the
can crack
decrease the these
crack reasons,
risk. For these are ideal for ofenergy harvesting decrease
risk. For
IDEs
arereasons, ideal for IDEs energy
harvesting
vibration
energy, of vibration energy, as well as for actuators. Systematic investigations of PZT films with IDE systems are as well as for actuators. Systematic investigations of PZT films with IDE systems are still missing to
still date. this work we on
present results on the in-plane
evaluation of the in‐plane piezoelectric date.missing In thisto work
weIn present
results
the evaluation
of the
piezoelectric
coefficients
with
coefficients with IDE systems. Idealized effective coefficients e
and h
are derived, showing its IDE
IDE
IDE systems. Idealized effective coefficients
e
and
h
are
derived,
showing
its
composite
nature
IDE
IDE
rd
rd
composite nature with about 1/3
contribution with about 1/3rd contribution of the contribution of the transverse effect, and about 2/3
transverse effect, and about 2/3rd contribution of the longitudinal
of the longitudinal effect in case of a PZT film deposited on a (100)‐oriented silicon wafer with the in‐
effect in case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric field
plane electric field along one of the <011> directions. Randomly oriented, 1 µm thick PZT 53/47 film along one of the ¡011¿ directions. Randomly oriented, 1 µm thick PZT 53/47 film deposited by a soldeposited by a sol‐gel technique (figure 1 (b)), were evaluated and yielded an effective coefficient, gel technique (figure 1 (b)), were evaluated and yielded an effective coefficient, eIDE of 15 C/m2 . We
epropose
C/m2. We propose measurable of merit for structures
thin film energy harvester IDE of 15 a measurable
figure of a merit
(FOM) forfigure thin film
energy(FOM) harvester
as the product
structures as the product between effective ‘e’ and ‘h’ coefficient representing twice the electrical between effective ‘e’ and ‘h’ coefficient representing twice the electrical energy density stored in
the
energy density stored in the piezoelectric film per unit strain deformation. Assuming homogeneous piezoelectric film per unit strain deformation. Assuming homogeneous fields between the fingers, and
fields between the fingers, and below
neglecting the contribution electrode fingers, neglecting
the contribution
from
the electrode
fingers, the from FOM below for IDEthe structures
is derived
to the FOM for IDE structures is derived to be twice as large as for PPE structures for PZT‐5H properties. The be twice as large as for PPE structures for PZT-5H properties. The experiments yielded a maximal FOM
9
experiments yielded a maximal FOM of the IDE structures of 7.5 x 10
J/m3. of the IDE structures of 7.5×109 J/m3 .
a 22
b c Figure 1: (a) schematic illustration PZT film with IDE, showing the polarization pattern and charge Figure
1: (a) schematic illustration PZT film with IDE, showing the polarization pattern and charge collected in
collected in the IDE (+q), (b) shows the SEM cross section and (c) shows the optical top view of IDE the IDE (+q), (b) shows the SEM cross section and (c)pattern shows the optical top view of IDE pattern.
23
Reactive Magnetron Sputtering of Ultrathin Piezoelectric Aluminum
Nitride Films
Valeriy Felmetsger1 , Pavel Laptev2 and Roger Graham3
1 OEM
Group Incorporated, USA
Micro Technology
3 NanoTEM Analytics Incorporated, USA
2 Innovative
One of today’s challenges is to develop electroacoustic devices operating at higher frequencies. As
the resonance frequency of the resonator is determined by the thickness of the AlN layer, there is essential interest of using ultrathin 100-200 nm films to extend the current FBAR technology from 1-2 to
10-20 GHz range. 100-nm and thinner AlN films with precisely controllable in-plain stress as well as
stress gradient through the film thickness are required for a new class of vertically deflecting piezoelectric nanoelectromechanical (P-NEM) actuators recently implemented for low power logic applications.
However, it is challenging to deposit such thin films with acceptable piezoelectric coefficients due to
their drastically downward crystallinity compared to 500-2000 nm thick films currently employed in
mass production.
In this study, technological solutions for reactive magnetron sputtering of higly textured nanoscale
AlN films (having thicknesses as low as 200 down to 25 nm) have been proposed, their microstructure,
crystal orientation, and features of stress control have been investigated.
To promote the nucleation of small size grains preferably oriented by nitrogen basal plain on top, a
two-step reactive sputtering process by an ac (40 kHz) powered S-gun magnetron was employed. In the
first stage, a higher substrate temperature (400-450 ◦ C) and a higher nitrogen concentration in Ar-N2 gas
mixture are used during growth of the first 20 nm thick film. In the second stage, the remaining film is
deposited at an ambient temperature of about 300 ◦ C, while the N2 flux is reduced to the value enabling
the magnetron discharge to remain in a poison mode but at the work point located closer to a transition
zone between a poison and a metallic mode on the hysteresis curve. Regulation of the flux of charged
species, substrate temperature, and gas content during deposition enabled formation of the films with
low and controllable stress gradient as well as in-plane stress. The two-step AlN processing combined
with the capability to deposit smooth and highly textured Mo bottom electrodes has demonstrated high
efficiency in producing very thin piezoelectric AlN films exhibiting superior crystallinity with FWHM
from 1.8◦ (200 nm) to 3.1◦ (25 nm) on Mo electrodes.
HRTEM results have confirmed that the 25-100 nm thick films have a fine columnar texture and a
continuous lattice microstructure within a single grain from interface with the Mo layer through to the
AlN surface. Although the grains were found slightly rotated relative to one another about the c-axis,
the (0001)-type planes parallel to the interface with the Mo substrate were observed in all samples,
confirming the presence of a strong orientation even in the 25 nm thick film.
24
Influence of Temperature and O2 Flow Rate on the Structure and
Ferroelectric Properties of PZT Films Deposited by RF Magnetron
Sputtering
Yun Sung Kang1 , Sang Jin Kim1 , Seung Hun Han1 , Min Kyu Choi1 , Sung Min Cho2 and Jung Won
Lee1
1 AMD
2 Micro
Lab. Samsung Electro-Mechanics,314 Maetan-Dong, Suwon 443-743, Korea
Fab. Samsung Electro-Mechanics,314 Maetan-Dong, Suwon 443-743, Korea
Pb(Zr,Ti)O3 (PZT)films have attracted considerable attention for potential micro-electronics and
electro-mechanical applications due to their excellent ferroelectric and piezoelectric properties. PZT
films in thickness range of 2-2.5 mm were deposited on Pt/TiOx /SiO2 /Si multilayered substrates by radio
frequency magnetron sputtering. The influence of deposition temperature (560-620 ◦ C) and O2 flow rate
(0.5-2 sccm) on the structural, electrical, ferroelectric and piezoelectric properties of the PZT films was
systematically evaluated. According to this study, the deposition temperature has a strong influence on
the evolution and texture of the ferroelectric perovskite phase and microstructure of the films.
25
Influences of Titanium Underlayer on (002) Oriented Aluminium Nitride
Nathan Jackson1 , Robert O’Leary1 , Rosemary O’Keeffe1 , Mary White1 , Mike O’Neill2 , Finbarr
Waldron1 and Alan Mathewson1
1 Tyndall
National Institute, University College Cork, Ireland
2 Analog Devices Inc., Ireland
Recently, aluminium nitride (AlN) has become a highly researched piezoelectric material because of
its unique properties. Piezoelectric AlN films have been used as resonators, actuators, transducers, and
energy harvesting devices. AlN is CMOS compatible, which makes it easier to integrate into an IC chip
design. Moreover, it is not a ferroelectric material, so poling is not required to obtain a piezoelectric
effect. However, the crystal orientation of the material is critical in order to optimise the piezoelectric
properties. AlN has been deposited using various methods and on numerous materials. AlN deposited
on metals such as Pt, Ti, and Mo have shown the highest orientation of (002) c-axis AlN films.
The authors have investigated the influences of using Ti and various deposition parameters on the
(002) crystal orientation of AlN. Various DC sputtered Ti and AlN films were investigated using AFM,
SEM, and XRD in order to determine the affects of the underlying layers on the (002) orientation of
AlN. Ti was deposited onto Si and Si/SiO2 substrates, followed by a DC sputtered AlN film. Variations
included, Ti thickness, AlN thickness, continous deposition of AlN or multiple breaks, and with or without a SiO2 isolation layer. Full width half maximum (FWHM) values obtained from the XRD rocking
curve of both the Ti and AlN layers were used to determine the influences of the varying parameters on
the (002) AlN films.
The results show that all of the varied parameters had a significant affect on the RMS surface roughness. The thinner films along with multiple depositions of AlN and no oxide gave the lowest surface
roughness values. SEM cross section images show good columnar c-axis (002) oriention of the AlN
film. The FWHM results of the (002) AlN film show a strong correlation with quality of the (002) Ti
oriented film. The highest quality film had a FWHM of 1.5◦ (AlN) and 1.8◦ (Ti).
In conclusion, optimising the quality of the underlying layers is critical in order to obtain the highest
quality (002) oriented AlN film.
26
Interdigitated Electrodes Based Cantilevers for Piezoelectric Energy
Harvesting
A. Mazzalai1 , N. Chidambaram1 , P. Muralt1
1 Ceramics
Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Switzerland
We report on conception, simulation, fabrication, and characterization of PZT thin film structures
for piezoelectric vibration energy harvesting (EH). We investigated specifically interdigitated electrode
configurations (IDE), which in theory, allow for a better exploitation of the capabilities of lead zirconate
titanate (PZT) as an active material in terms of output voltage and output power. The overall efficiency
of a MEMS energy harvester is analyzed and also compared to versions with parallel plate structures.
The IDE arrangement decouples the electrode gap from the thin film thickness, allowing to reduce
the capacitance of the active layer and therefore to increase the output voltage, which is very important
for any diode-based rectification and charge pumping circuit. The product of the effective piezoelectric
coefficients eeff and heff constitutes an easy to measure relevant figure of merit for thin film based EH
structures. From the constitutive equations of piezoelectricity we conclude that IDE harvesters can also
carry about twice the energy density with respect to parallel plate electrodes (PPE) devices with the
same active volume.
The results of finite element modeling (FEM) investigations for both IDE and PPE are presented and
compared with simplified analytical calculations. We studied the harvesting efficiency as a function of
the power input in the form of elastic beam bending. Due to its higher coupling coefficient, PZT thin
film based systems with IDE’s can harvest a given amount of stored elastic energy much faster than PZT
PPE and AlN PPE structures. Based on these results, an EH design for broadband devices applications
is proposed and discussed also in its critical aspects of stress compensation and capacitive coupling.
The micro fabrication route of the PZT laminated beams is presented. Deposition of PZT thin films
was investigated with both magnetron sputtering and chemical solution routes. Silicon cantilevers coated
with 2 µm thick PZT 53/47 thin films with mainly (100)-orientation were fabricated and characterized.
27
Local Polarity Control of (001)AlN Thin Films
E. Milyutin1 , S. Harada1 , D. Martin2 , J. F. Carlin2 , N. Grandjean2 , V. Savu3 , O. Vaszques-Mena3 , J.
Brugger3 and P. Muralt1
1 Ceramics
Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland
of Advanced Semiconductors for Photonics and Electronics, Ecole Polytechnique
Fédérale de Lausanne EPFL, Lausanne, Switzerland
3 Microsystems Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland
2 Laboratory
We report on the ability to control the polarity of sputter deposited AlN(001) thin films using seed
layers. Reactive sputter deposition leads to N-polarity on any substrate hitherto applied, i.e. Si(111),
sapphire, SiO2 , polycrystalline metals such as Pt(111), Mo(110), W(110), etc. A site-controlled polarity
allows for an efficient excitation of shear modes of surface, bulk, and Lamb waves by interdigitated
electrodes. We were able to introduce the Al-polarity through a MOCVD seed layer. By subsequently
patterning the substrate surface it was possible to define the desired film polarity of sputter deposited
AlN film. Polarities were determined by selective etching with KOH solutions and by piezoresponse
force microscopy (PFM).
28
Hyper Frequency Properties of “3 Inches-frozen Capacitive MEMS” with
PZT Thin Films Processed by Sol-gel
M. Pham Thi1 , P. Martins1 , A.Leuliet1 , M. Pate1 and A. Ziaei1
1 Thales
Research Technology France, 1 Avenue A. Fresnel, 91676 Palaiseau Cedex France
e-mail: [email protected]
RF-MEMS have a crucial role to play in future wireless systems through the development of filters, high-Q inductors, high-density capacitors and low loss switches to enable novel and improved RF
transceiver front-ends. Compared with FETs or PIN diodes, RF MEMS present lower insertion loss in
the “on state” and better isolation in the “off state”. Most of capacitive RF MEMS use Si3 N4 as dielectric
layer. Its low dielectric constant (7@few GHz) limits the performance of device at low frequency.
PZT exhibiting high-k dielectrics constant were investigated in capacitive MEMS to lower the
switching bandwidth up to 2 GHz. A frozen capacitive MEMS switch, that simulates a MEMS in it
“on state” consists of coplanar lines shunted by a dielectric patch. Gold electrodes were deposited by
evaporation and PZT or derived PZT thin films were obtained by spin coating onto 3 inch Silicon substrates. Crystallization of PZT thin film was optimized about 500 ◦ C in order to limit the diffusion of Au
electrode. At this temperature pure perovskite thin films exhibiting a dielectric constant of 500-1000@
2-7 GHz were observed. The increase of dielectric constant with thin film thickness is consistent with
data in the literature and reveals the presence of dead layer at electrode/PZT interface thin film. The
variation of the dielectric constant versus frequency, measured for three capacitance dimensions exhibits
a circuit resonance from 4 GHz to 9 GHz for the value of capacitance from 82 pF to 22 pF. These resonances perturb dielectric constant determination and imply the right choice of capacitance dimension
versus frequency. Influence of bias on dielectric properties were measured in order to evaluate PZT
behaviour during switching.
HF measurements were done from 1 GHz to 20 GHz. The reflection coefficients are high, between
−0.5 and −0.6 dB for most lines. At 10 GHz all the shunted lines have high attenuation, better than
−39 dB. These data are promising and implementation of PZT and derived PZT thin film in MEMS
process is in progress.
29
Active Damping with A Piezoelectric MEMS Device
Thierry Verdot1 , Paul Muralt2 and Manuel Collet1
1 Femto-st
2 Ecole
institute, Département de Mécanique appliquée, France
Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Céramique (LC), Switzerland
Active stabilization strategies offer interesting prospects for the protection of embedded MEMS devices against accelerations generated by their vibrating support. Moreover, downscaling operated in
microtechnology brings substantial benefits. First, the reduced amount of mass to control lowers drastically the energy required for the active stabilization. Then, the large variety of coupling mechanisms,
mature in microengineering, offers facilities for the integration of actuators and sensors required for control implementation. The device presented at the 2nd International Workshop on piezoelectric MEMS is
a piezoelectric Micro Active Suspension prototype dedicated to the application of a stabilization strategy
called Integral estimated-Force Feedback. Basically, it is a mechanical suspension etched in a siliconon-insulator wafer and equipped with an actuator/sensor pair integrated via a Pb(Zr0.53 ,Ti0.47 )O3 thin
film deposited by gradient free sol-gel route. Obtained ferroelectric transducers exhibit high transverse
piezoelectric coefficient in the linear domain restricted to ±2 V. Their remarkable authority on suspension dynamic combined to a weak electrical “cross-talking” enables the implementation of the controller
by using a restricted number of electronic analog low-voltage components. The transfer functions of
the closed-loop system, recorded during experimental test conducted on a vibrating table, emphazise
sky-hook damping actively introduced that stabilizes suspension dynamic while preserving isolation
performances above its cutoff frequency.
30
Modelling of Piezoelectric Micromachined Ultrasound Transducers
(pMUT) for Medical Use
Andreas Vogl1 and Dag T. Wang1
1 1SINTEF
ICT, Department of Microsystems and Nanotechnology, Oslo, Norway
PiezoMEMS transducers consist often of multilayered thin-film structures which are difficult to
model with finite element modelling (FEM) tools due to high aspect ratio of the geometry. Therefore, a
set of analytical models for different variables in the transfer function of the pMUT has been developed
as a checking point for the multiphysics FEM simulations.
The transfer function for the frequency f of the circular, membrane based ultrasound transducer in
bending mode can be written as the quotient of amplitudes of average deflection and applied voltage to
the structure:
2 ln Rm
kM(V
)R
0
in
Rin
y0
H( f ) ≡
=
.
V0 2Dm [k + j2π f Z( f ) − m(2π f )2 ]
Here we use the spring constant k, the piezoelectric bending moment due to the voltage M(V ), the radii
Rin (inner radius of the actuation electrode) and Rm (membrane radius), the flexural rigidity Dm , the
acoustic impedance Z( f ) (defined as in [1]) and the membrane effective mass m.
The results of the analytical modelling and a FEM model in COMSOL multiphysics regarding the
first eigenfrequency and centre displacement for a pMUT in water were compared and showed only
minor deviations. A combination of both modelling types has been used for the modelling of pMUTS
which are currently under manufacturing at SINTEF. This approach allows for a quick exploration of the
design space with the analytical models for this multiphyscis problem and providing a check point for
the time consuming optimal meshing of the high-aspect ration geometries for FEM. At the same time
important design parameters can also be identified. The multiphysics FEM simulations give additional
qualitative and quantitave information e.g. higher order eigenmodes close to the first one.
[1] Kinsler, L.E., Fundamentals of acoustics. 4th ed. 2000, New York ; Chichester: Wiley. xii, 548 p.
[2] Muralt P., Kholkin M., Kohli M., Maeder T, 1996, Piezoelectric actuation of PZT thin-film diaphragms at static
and resonant conditions, Sensors and Actuators A53, 398-404
31
Piezoelectric MEMS Fabrication Integrating Thermally and
Mechanically Incompatible Materials
P.B. Kirby1 and R.V.Wright1
1 Cranfield
University,UK
In common with a number of other technologically important thin film materials high temperatures
are required for the growth of high quality piezoelectric films either for film deposition itself or during
a subsequent anneal which can make them difficult to integrate with conventional e.g. CMOS devices.
Also with the advent of plastic electronics mechanical constraints are now becoming important: the mechanical strain in flexible circuits for example can reach ∼3% which is well above the breaking strain
of many inorganic piezoelectric materials. It is possible with some materials to overcome thermal incompatibilities by reducing film growth temperature a good example of which is sol-gel deposited PZT,
which can be grown at temperatures as low as 500 ◦ C, but an attractive option which has recently been
developed is transfer bonding in which the piezoelectric layer is deposited on a separate wafer, then
bonded to the low temperature substrate and finally removed from its original substrate by mechanical
grinding and/or chemical etching or if the substrate is uv transparent by excimer laser ablation. Strategies to deal with mechanical incompatibility include use of a temporary rigid backing to enable planar
processing and strain relief measures such as buckled interconnecting beams and strain isolating layers.
In the present work some of these approaches have been applied to a range of piezoelectric devices to
overcome thermal and mechanical constraints. Thin film PZT actuated DC contact RF MEMS switches
have been fabricated using two types of transfer bonding technique one in which stud bonding is combined with laser ablation for selective device transfer and another which employs adhesive bonding for
full wafer device transfer. Good switching performance has been achieved with both. A simple process
for the transfer of thin film PZT structures onto polydimethylsiloxane (PDMS) for energy harvesting applications has also been demonstrated in which a Si substrate containing the structures is pressed against
a separate PDMS coated substrate and then etched away by deep reactive ion etching. The transferred
structures appear well bonded but some reduction in their ferroelectric, and hence piezoelectric, properties following transfer has been observed. ZnO based thin film bulk acoustic resonators (FBARs) have
been fabricated directly onto a flexible liquid crystal polymer by pre-bonding the flexible substrate to
a rigid backing wafer to enable conventional planar processing and lowering the ZnO growth temperature to 200 ◦ C. A high effective electromechanical coupling constant (k2 ) has been achieved ∼6.7% but
the low growth temperature and consequent non-optimum grain structure is believed to have led to the
limited series and parallel Q values that are observed (126 and 78 respectively).
Part III
W 7, S
O 
35
All-oxide PiezoMEMS Devices by Pulsed Laser Deposition: Properties of
Clamped Epitaxial PZT Thin Films
Guus Rijnders1
1 MESA+
Institute for Nanotechnology, University of Twente, POBox 217,7500AE, Enschede,
Netherlands
Ferroelectric oxides, such as Pb(Zr,Ti)O3 (PZT), are very useful for electronic and photonic devices,
as well as piezomechanical actuators and sensors. The ferro- and piezoelectric properties are strongly
related to the crystal orientation as well as the strain state of the PZT layer. Successful integration of
these devices into silicon technology is therefore not only dependent on the ability of epitaxial growth
on silicon substrates, but also the control of the crystallographic orientation and the residual strain state
of the deposited PZT thin film.
A study will be presented on the effects of the residual strain in PZT thin films on the ferroelectric
and piezoelectric properties. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between
SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations
by pulsed laser deposition. All the PZT films show ferroelectric behavior that is consistent with the
single domain ferroelectric r-phase. Compressive or tensile stress caused by the difference in thermal
expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. Their
dependences on this misfit strain are in good correspondence with theoretical predictions. We conclude
that clamped (001) oriented single domain Pb(Zr0.52 Ti0.48 )O3 thin films strained by the substrate always
show rotation of the polarization vector.
In this contribution, I will furthermore highlight the recent progress on the fabrication of all-oxide
piezo-MEMS devices by pulsed laser deposition.
36
Introduction of New Manufacturing Technology for Piezo (PZT) MEMS
Production
Janssens, Arjen1
1 CEO
SolMateS, Netherlands
[email protected]
The MEMS market is growing fast of which PiezoMEMS applications are showing high market
potential. Many companies are working on Piezo actuated MEMS, trying to get their application from
development towards production. One of the major challenges in this process is the reliable integration
of the Piezo material (PZT) on the silicon wafer. The deposition of PZT on silicon wafers is not straightforward as the optimal material performance; yield and stability are hard to achieve using traditional
deposition technologies. For this reason SolMateS offers the PiezoFlare 1200 to deposit PZT thin films
on 6" and 8" wafers.
This thin film platform uses laser deposition to deposit PZT and oxide electrodes in the same reactor.
Due to its modular configuration we have a solution from research till production. The PiezoFlare 1200
is designed to manufacture reliable PZT thin films. Measurements show high and homogeneous piezo
performance on each wafer, and stable values from wafer to wafer. The PiezoFlare 1200 enables reliable
production capability for PZT thin film deposition.
After the PZT thin films (1-3 µm) are deposited no poling and RTA is required. Wafer mapping
using DBLI (AixaCCT systems) show uniform d33 values across the wafer with values of 180 pm/Volt
or higher for a 1mm2 pad size and 2 µm PZT thin films. From cantilever tip displacement measurements
d31 values of 120 pm/V and higher are calculated. Furthermore measurements show stable membrane
and cantilever actuation till 1010 cycles.
37
Epitaxial Ferroelectric Pb(Zr0.2 Ti0.8 )O3 Thin Films on Silicon: Growth
and Physical Properties
S. Gariglio1 , A. Sambri1 , P.Janphuang2 , D. Isarakorn2 , D. Briand2 , J.W. Reiner3 , A. Torres Pardo4 , O.
Stéphan4 , C.H. Ahn3 , N.F. de Rooij2 and J.-M. Triscone1
1 University
2 Ecole
of Geneva, Switzerland
Polytechnique Fédérale de Lausanne (EPFL), Switzerland
3 Yale University, USA
4 Université Paris-Sud, France
This work discusses the growth and properties of epitaxial ferroelectric layers on silicon for piezoelectric MEMS devices. Nowadays it is possible to control the growth of epitaxial thin films of perovskite structure on silicon substrates using a SrTiO3 layer as a chemical and structural buffer. The
integration of this crystalline oxide layer on silicon requires a complex multi-step procedure achieved
by molecular beam epitaxy. The successive bottom electrode SrRuO3 and ferroelectric Pb(Zr0.2 Ti0.8 )O3
thin films are grown by reactive magnetron sputtering. We currently master this process on 3 inch silicon
substrates.
The structural analysis performed by transmission electron microscopy and x-ray diffraction reveals
a full epitaxial relation between the layers. Polarization-voltage loops, measured at room temperature
on 100×100 µm2 Cr/Au top electrodes, reveal a remnant polarization and a coercive field of about
70 µC/cm2 and 250 kV/cm, respectively. Piezo-force microscopy yields an estimation of the piezoelectric d33 coefficient of 50 pm/V.
As for ferroelectric materials it is well known that the mechanical boundary conditions affect substantially the ferroelectric properties through the strain-polarization coupling, we have investigated the
effect of the epitaxial strain on the critical temperature of the paraelectric-ferroelectric phase transition.
A. Sambri et al., Appl. Phys. Lett. 98, 012903 (2011).
38
Oerlikon PVD Production Solution for in-situ Large Scale Deposition of
PZT Films
Kratzer M.1 , Kaden D.2 , Quenzer H J.2 , Castaldi L.1 , Heinz B.1 , Harada S.3 , Mazzalai A.3 and Muralt P.3
1 Oerlikon
Balzers, Liechtenstein
ISIT, Germany
3 EPFL, Switzerland
2 Fraunhofer
The direct growth of piezoelectric PZT films by RF sputtering (PVD) is considered as the deposition
method particularly suitable to satisfy the increasing demand for this material type driven by various
applications like sensors, energy harvesting devices, ink-jet printing heads and other active components.
This is because of the remarkable advantage of the PVD deposition method to grow high quality films
in a single process step (in-situ) without post annealing.
One prerequisite for the in-situ growth of the correct crystalline perovskite structure is the tight
temperature control of the substrate in the range of 500 ◦ C during film deposition. Challenges arise
because of the required temperature uniformity especially for the large wafer size of 200 mm. Further
on the sputter equipment has to be optimized to enable a deposition process at a high throughput which
is a key factor for minimized cost of ownership for PZT volume production.
The status of the tool development for in-situ deposition of PZT films by sputtering will be presented.
The hardware capabilities will be shown and their influence on the PZT film properties will be discussed.
As a result high quality PZT films were deposited on 8" wafer showing a considerable piezoelectric
performance with highest piezoelectric coefficients d33,f of 120 pm/V and e31,f of −13.8 C/m2 on 200 mm
substrate size.
39
Measurements of Electrical and Electromechanical Characteristics of
Piezoelectric Thin Films and Optimization of Poling
Stephan Tiedke1 , Roland Kessels1 , Thorsten Schmitz-Kempen1 , Gwenaël Le Rhun3 , Dirk Kaden4 and
Paul Muralt5
1 aixACCT
Systems GmbH, Germany
France
4 Fraunhofer Institut für Siliziumtechnologie, Germany
5 Swiss Federal Institute of Technology EPFL, Switzerland
3 CEA-LETI,
The first mass-products of Micro-Electro-Mechanical Systems (MEMS) based on piezoelectric thin
films have been introduced into the market. A broad range of new applications are currently being
developed e.g. energy harvester for autonomous devices, new ink-jet printer heads, RF-switches and
tilted mirror arrays. With more products under development the need of accurate and standardized
characterization of piezoelectric films is increasing.
The characterization of the piezoelectric film properties is essential for device design as well as
device simulation and critical for process qualification. Different measurement methods for the investigation of the piezoelectric thin film properties will be presented.
The first method presented uses the Double Beam Laser Interferometer (DBLI) to measure the effective longitudinal (d33,f ) coefficient of piezoelectric thin films on wafer level up to 8 inch. Resolution and
long-term repeatability were verified by an x-cut quartz sample and 8 inch wafers with AlN thin films as
a stable reference piezoelectric material.
The second method focuses on thin film samples on silicon substrates where the electrode layout is
adapted to our 4-point bending setup for measurement of the transversal piezoelectric (e31,f ) coefficient
under well-defined homogeneous mechanical strain. Stress and corresponding strain distributions in
the film were verified by Finite Element simulations. Repeatability was also verified on AlN thin film
samples. This combination of setups allows fast and accurate measurements of both coefficients on
Pb(Zr,Ti)O3 (PZT) thin films.
In the second part of the presentation it will be shown that careful poling of Pb(Zr,Ti)O3 (PZT) thin
films under elevated temperature and different excitation signals can significantly increase the piezoelectric coefficients. In some cases the e31,f coefficient could be increased by 50% or more. Optimizations
of the poling condition will be presented and the results will be summarized.
40
Direct And Indirect Piezoelectric Characterization of PZT Thin Films for
MEMS Applications
Abergel, J.1 , Cueff, M.1 , Michaud, H.1 , Allain, M.1 , Ricart, T.1 , Dieppedale, C.1 , Suhm, A.1 , Kessels,
R.2 , Tiedke, S.2 , Le Rhun, G.1 , Fanget, S.1 , Aı̈d, M.1 and Defaÿ, E.
1 CEA
2 AixACCT
LETI Minatec Campus, 38054 Grenoble, France
Systems GmbH Dennewartstr. 25, D-52068 Aachen, Germany
Pb(Zr,Ti)O3 (PZT) thin films have been extensively studied during the last 20 years because of their
outstanding ferroelectric, dielectric and piezoelectric properties. However, it appears that there is still a
large discrepancy between the communicated piezoelectric coefficients. This is closely related to the fact
that thin films are clamped to their subtrates. Thus, only effective piezoelectric coefficients, which are a
combination of purely piezoelectric coefficients and elastic constants, can be extracted. Moreover, thin
films elastic constants are not well known: that increases the difficulty to determine pure piezoelectric
coefficients.
In this study, we propose to implement a direct and indirect piezoelectric characterization of PZT
films in order to provide a clear assessment of the transverse piezoelectric coefficients. Those characterizations give the opportunity to eventually determine e31 , d31 and the Young modulus of these
PZT thin films. (100)-oriented sol-gel 2 µm-thick Pb(Zr0.52 ,Ti0.48 )O3 films were deposited on 200 mm
SOI wafers. The final stack was Si substrate/0.5 µm-SiO2 (BOX)/5 µm Si (SOI)/0.5 µm-SiO2 /0.1 µm
Pt/2 µm-PZT/0.1 µm Ru. Two types of piezoelectric characterizations were performed on these films.
On one hand, the effective direct transverse coefficient e31,eff was extracted by using the 4-points bending
method provided by Aixacct [1]. On the other hand, the indirect transverse coefficient d31 was extracted
from measuring the deflection with a WYCO interferometer of a processed membrane actuated by the
PZT film. PZT membranes were released by a back-side etching process. Thanks to the SOI processed
substrates, the cavity length is very well-controlled. That consequently makes these devices particularly
suitable for d31 measurements. d31 was fitted by using a Finite Element Model (Comsol).
The extracted e31,eff value is −15.95 C/m2 . It is worth noting that e31,eff does not require PZT’s
Young Modulus EPZT to be determined. The extracted d31 value is −150 pm/V. In this case, EPZT plays a
minor role on the mechanical behaviour of the membrane which is mainly influenced by the 5 µm thick
SOI Si layer. Moreover, e31,eff , d31 and the Young modulus E are linked by d31 =e31,eff (1-ν)/E, where
ν is the Poisson ratio. By using ν=0.3, the evaluated E is 74 GPa, which fits with PZT bulk ceramics
values reported in the literature for PZT in morphotropic phase [2]. Therefore, a careful characterization of direct and indirect piezoelectric coefficients of PZT films gives consistent data with the typical
following values: e31,eff =−15.95 C/m2 , d31 =−150pm/V and EPZT =74 GPa.
[1] K. Prume, P. Muralt, F. Calame, T. Schmitz-Kempen, and S. Tiedke, “Piezoelectric thin film: evaluation of
electrical and electromechanical characteristics for MEMS devices,” IEEE Trans. Ultrason., Ferroelectr., Freq.
Control, vol. 54, no. 1, pp. 8-14, 2007.
[2] A. K. Singh, S. K. R. Mishra, D. Pandey, S. Yoon, S. Baik, and N. Shin, “Origin of high piezoelectric response
of Pb(Zrx Ti1−x )O3 at the morphotropic phase boundary: Role of elastic instability,” Appl. Phys. Lett, vol. 92,
no.2. art. no. 022910, 2008.
2
nd
41
Spin-Coat Technology
of Technology
KNN Film of
Deposition
Oxygen Pressurizing
Spin-Coat
KNN Filmwith
Deposition
with Oxygen RTA
Pressurizing RTA
1 , Takekazu Shigenai1 and Yuji Honda1
Takeshi
Kijima
Takeshi
Kijima,
Takekazu Shigenai and Yuji Honda
1 Youtec
Japan
Youtec Co.,Ltd.
Co.,Ltd. Japan
Recently,
KNNKNN
ceramics
is expected
to next
generation
piezoelectric
material
as lead-free.
However
there
Recently,
ceramics
is expected
to next
generation
piezoelectric
material
as lead-free.
However
are
only
several
reports
of
the
KNN
film
deposition
by
PVD
as
thin
film.
This
study
reports
a
success
in
the
there are only several reports of the KNN film deposition by PVD as thin film. This study reports
KNN film deposition by Spin-Coat Technology with the Oxygen Pressurizing RTA. Spin-Coat technology is
a success in the KNN film deposition by Spin-Coat Technology with the Oxygen Pressurizing RTA.
suitable for industrial production more than PVD concerning its cost.
Spin-Coat
technology
is suitable
for industrial
moreprocess.
than PVD
concerning
its cost.
We
developed
an original
KNN sol-gel
solution production
and deposition
High
concentration
KNN solution
We developed
original
KNN
sol-gel
solution
and and
deposition
process.
High(about
concentration
KNN
(25 weight
%) is a an
feature
of our
original
sol-gel
solution
high pressure
oxygen
10 atm) during
solution
(25 weight
%) isofa our
feature
of our
original process.
sol-gel solution
andhigh
highpressure
pressureoxygen
oxygenand
(about
RTA
process
is a feature
original
deposition
Combining
high
10 atm) duringKNN
RTAsolution
process provides
is a feature
our original
deposition
process.
Combining
concentration
the of
highest
KNN crystal
growth
rate without
help high
of a pressure
substrate
orientation.
consider
that chemical
kinetics is
applied the
to the
KNNKNN
crystal
growth.
The rate
KNNwithout
crystal
oxygen andWe
high
concentration
KNN solution
provides
highest
crystal
growth
growth
prvided
from
an
upper
surface
of
an
amorphous
KNN
film
is
fastest
growth.
A
crystallization
help of a substrate orientation. We consider that chemical kinetics is applied to the KNN crystal growth.
direction
an ingredient
is the
strongest
likesurface
a KNNof
bulk.
The KNNofcrystal
growth(110)
prvided
from
an upper
an amorphous KNN film is fastest growth. A
Very thin piezofilms are deposited on the KNN film to cap it and spun it before RTA process. This cap layer
crystallization
direction
of
an
ingredient
(110)
is
the
strongest
like a KNN bulk.
prevents an alkaline metal from evaporating and assists a crystallization of the KNN film from the upper
Very
thin
piezofilms
are
deposited
on
the
KNN
film
to
cap
it and in
spun
it before
RTAofprocess.
This
surface. Now we have developed that the KNN film may be crystallized
a (110)
direction
a polarization
cap layer prevents an alkaline metal from evaporating and assists a crystallization of the KNN film from
axis.
the uppershows
surface.
Nowsection
we have
that the
may
be with
crystallized
a (110)surface
direction
Figure.1
a cross
of developed
the KNN film.
2umKNN
thickfilm
KNN
film
flat and in
smooth
was
obtained.
The
cap
layer
was
not
obtained.
of a polarization axis.
Figure.2 shows XRD of the KNN film. This film has single layer with (110).
Figure.3 shows C-V carve of KNN. 2Pr is 30uC/cm2 at 100V.
Fig.1
Fig.2
Fig.3
Fig. 1 shows a cross section of the KNN film. 2 µm thick KNN film with flat and smooth surface was
obtained. The cap layer was not obtained.
Fig. 2 shows XRD of the KNN film. This film has single layer with (110).
Fig. 3 shows C-V carve of KNN. 2Pr is 30 µC/cm2 at 100 V.
42
Properties of PMN-PT 65/35 thin film oriented -h011i at radio frequency
measured by coplanar waveguide
Kim-Anh Bui-Thi1,2 , Mai Pham-Thi1 , Gui Garry1 , Aude Leuliet1 , Michel Pate1 , Paolo Martins1 ,
Afshin Ziaei1 and Philippe Lecoeur2
Research & Technology, Palaiseau, France
d’Electronique Fondamentale, Orsay, France
1 Thales
2 Institut
In capacitive MEMS (micro-electro-mechanics systems) applications, the dielectric constant decides
usually the working frequency of the device. Communly used dielectrics like Si3 3 N4 , SiO2 , ZrO2 ...
allow good isolation at high frequency (30 GHz). In order to adapt the component for the radar applications (10 GHz) and telecommunication (500 MHz-3 GHz), one has to increase the capacitace of the
device by replacing these dielectrics by a high-k dielectric or by modifying the capacitance dimensions
and the thin film thickness. The latters are not very effective since they can increase only a few times the
capacitance while changing the dielectric can increase the capacitance sometimes a factor of 100. That
is the reason why high-k dielectric becomes the best choice to optimize the working frequency.
Well known as a very good material for MEMS actuators and sensors, PMN-PT has been studied
since a long time mainly to optimize its electro-mechanical response. In order to obtain high-k dielectric
for radiofrequency micro-electro-mechanics systems, we have concentrated recently on PMN-PT 65/35
because of its actractive permittivity. A lack of knowledge of this PMN-PT thin film at radio frequency
leads us to characterize these properties with a coplanar waveguide.
We have succeeded to grow PMN-PT thin film oriented h011i by Pulsed Laser Deposition on metalized silicon substrate. The very small remnant polarization of the PMN-PT oriented h011i is much
more advantageous than the usual h001i and h111i orientation for the functioning of the rapide MEMS
Switch applications. Our coplanar waveguide short-circuit (the coplanar waveguide isolated with a
blocked transversal metal line by a PMN-PT thin film) shows a good agreement between the simulation
with High Frequency Simulation Software and the RF measurement (the isolation S12 in both cases is
−40 dB around 10 GHz). The simulation considers the variation of the material permittivity in frequency using Debye relaxation model. The RF measurement has been carried on different capacitance
dimensions to make sure of the accuracy of the results. The working frequency range of our MEMS
Switch test using PMN-PT is very large: from 500MHz up to 20 GHz. This encouraging result shows
that it is possible to use this material for both applications in radars and telecommunication.
43
Influence of Solution Synthesis Conditions on Crystallization and
Properties of Functional Oxide Thin Films
Barbara Malic1,2 , Sebastjan Glinsek1,2 , Alja Kupec1 , Brigita Kužnik1,2 , Elena Tchernychova1,2 and
Marija Kosec1
1 Jožef
2 Centre
Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
of Excellence SPACE.SI, VESOLJE.SI, Aškerčeva 12, 1000 Ljubljana, Slovenia
Ceramic functional-oxide thin films with enhanced functional properties, such as dielectric permittivity, voltage tunability, remanent polarisation, piezoelectric properties, or electrocaloric effect, to
name only a few, have been studied for different microelectronic and microelectromechanical applications, including thin film capacitors, memories, sensors, actuators, tunable microwave devices or micro
heating/cooling devices.
Thin film microstructure critically influences the functional properties. In case of Chemical Solution Deposition (CSD), the crystallisation and evolution of the film microstructure depend on, and may
therefore be tailored by the chemistry of the sol, the choice of the substrate, and by the processing
conditions, mainly by the temperatures and times of the individual heat treatment steps - drying, pyrolysis and annealing. For example, the dielectric permittivity and voltage tunability of solution-derived
Ba0.3 Sr0.7 TiO3 (BST) thin films were almost doubled, namely from 345 and 1.47, to 722 and 1.93, as
the grain size was increased from 40 nm to 80 nm. (B. Malic et al., J. Europ. Ceram. Soc. 27 (2007)
2945.) In solution-derived PbZr0.3 Ti0.7 O3 (PZT) thin films, the design of microstructure and preferential
orientation of the perovskite phase with consequent changes of dielectric permittivity and ferroelectric
properties could be achieved by the choice of the reagents and the deposition-heating sequence. (B.
Malic et al., Integr. Ferroel., 100 (2008) 285.)
The contribution addresses the design of microstructure of selected ferroelectric complex perovskite
thin films based on lead-free perovskites: incipient ferroelectric potassium tantalate, potassium tantalateniobate, and potassium sodium niobate; which has been, in the bulk ceramic form, extensively studied
as the lead-free piezoelectric, with properties of some modified compositions comparable to those of
lead-based perovskites.
The correlation between the film microstructure and respective functional properties and the details
of the solution syntheisis of individual material compositons are discussed.
The work was supported by the Slovenian Research Agency (program P2-0105; young researcher
program, contract number: 10000-07-3100068) and by the European Union and Ministry of Higher
Education, Science and Technology of Slovenia.
44
Low Temperature Laser Processing of Ferroelectric Thin Films
S. S. N. Bharadwaja1 , F. Griggio1 , W. Qu1 , J. Kulik1 , T. Clark1 , H. Beratan2 and S. Trolier-McKinstry1
1 Materials
Research Institute, The Pennsylvania State University, University Park, PA 16802
2 Bridge Semiconductor Corporation, Pittsburgh, PA 15235
Low thermal budgets for processing of ferroelectric films are important for nonvolatile memories,
pyroelectric detectors, miniaturized piezoelectric transducers, and embedded dielectrics. Most complementary metal oxide semiconductor (CMOS) based read-out circuits can withstand processing temperatures less than 450 ◦ C; however large thermal budgets (>500 ◦ C) are required to crystallize ferroelectric
thin films such as Pb(Zr,Ti)O3 and BaTiO3 . Using KrF excimer laser annealing and oxidation, the substrate temperatures can be reduced below 400 ◦ C.
In this presentation, three main topics will be discussed:
(i) Crystallization kinetics of Pb(Zr,Ti)O3 thin films within the framework of rate dependent Avrami
theory under non-isothermal conditions. The resultant electrical properties of laser annealed films are
comparable to those of rapid thermally annealed Pb(Zr,Ti)O3 thin films.
(ii) Orientation control in laser annealed Pb(Zr,Ti)O3 52/48 thin films using a bottom template layer
at substrate temperatures below 400 ◦ C. Both {111} and {100} orientations were achieved in ∼200300 nm thick PZT layers on (111) Pt and 001 PbTiO3 surfaces. The measured average remanent polarization and coercive fields are 31 µC/cm2 and 86 kV/cm for 001 PZT films and 23.6 µC/cm2 and 64 kV/cm
for {111} oriented PZT thin films respectively. The maximum e31,f coefficients are ∼ −9.0 C/m2 for
{001} and ∼ −8.5 C/m2 for {111} PZT thin films respectively.
(iii) Oxidation kinetics of ∼200 nm thick BaTiO3 thin films on Ni foils in O2 /O3 (90/10) at substrate
temperature below 400 ◦ C for base metal capacitor applications. The resultant films have small signal
dielectric permittivities ∼ 1100 with <4% loss values between 0.1-1 kHz. Well-controlled interfaces
between the BaTiO3 and the Ni foil, without indication of a NiO reaction layer are confirmed from electron energy loss spectroscopy (EELS) and high resolution transmission electron microscopy (HRTEM)
studies.
45
FP7 piezoVolume - High Volume Piezoelectric Thin Film Production
Process For Microsystems
Tyholdt F1 , Haavik C.1 , Mazzalai A.2 , Tiedke S.3 , Kessels R.3 , Kratzer M.4 , Kaden D.5 , Schröpfer G.6 ,
Cruau A.6 , Muffler P.7 , Herrmann R.7 , Muralt P.2
1 SINTEF,
Norway; 2 EPFL, Switzerland; 3 aixACCT, Germany; 4 Oerlikon Baltzers, Liechenstein;
5 Fraunhofer ISIT, Germany; 6 Coventor, France; 7 Solar-semi, Germany
The main goal of FP7 piezoVolume (2010−2013) (www.piezovolume.com) is to develop a platform
of integrated processes for production of piezoelectric microsystems. In this platform the processes and
procedures specific to piezoMEMS have been identified i.e.: piezoMEMS modeling and process emulation, piezoMEMS design including design rules, PZT deposition tools for production, in-line piezoelectric thin film quality monitoring and a standard fabrication process including fab integration procedures.
piezoVolume develops solutions for all the elements in this platform. Even though the current main
bottleneck is the availability of piezoelectric thin film deposition tools capable of delivering suitable
deposition rate and performance uniformity, the importance of the other piezoMEMS specific elements
should not be forgotted when establishing a piezoMEMS fab. We believe that the availability of a complete process platform will lower the threshold for industry acceptance and be a key tool to realise new
products using piezoMEMS.
The status of the ongoing developments within the separate elements of the process platform will
be presented. Some examples from using the commercial piezoMEMS CAD and process emulation
software from Coventor will be shown. Modelling of the integration of piezoMEMS and ICs is now also
possible. Regarding PZT deposition tools, very promising results from single target sputtering on 150
and 200 mm wafers have been obtained in the project by Oerlikon, EPFL and Fraunhofer ISIT. Currently,
an e31,f of −13.8 C/m2 has been obtained on 200 mm wafers. Also, the status of an automated cluster
coater for CSD of PZT from Solar-semi will be presented. In-line quality monitoring is very important
for process control in a production environment and an automated Double Beam Laser Interferometer
(aixDBLI from aixACCT) integratable with a wafer robot capable of non-destructive e31,f estimation,
will be shown.
The consortium has the aim of aciting as a contact point and compentece centre for piezoMEMS
capable of prototyping and low volume fabrication. The plans for this will be presented.
46
Manufacture of Minature Tuneable Autofocus Lenses (TLens) using Piezo
MEMS
J.W. Phair1 and Daniel Rosenfeld1
1 poLight
AS, Norway
poLight AS, a Norwegian-based start-up company, has developed the world’s first piezo-actuated
autofocus lenses without moving parts. Its proprietary technology enables the production of wafer-scale
active optic components based on deformable polymers. poLight’s TLens offers some crucial advantages to the camera module market thanks to its extremely small size (4.2 mm×4.2 mm×0.5 mm), while
achieving high optical quality (megapixel independent and HD compatible). These features, combined
with its reflow-compatible manufacturing, positions the TLens as the ideal solution for the latest camera
phone applications such as videos with continuous-autofocus. The presentation will discuss the progress
poLight is making in bringing the production of the piezo-actuated TLens from small volume to high
volume including the main technical hurdles. A discussion of piezo production for the TLens, test and
measurement, integration as well as environmental consideration during the manufacture to high volume
will also be made.
47
Wafer Level Poling of PZT thin films for MEMS Sensor Devices
Seunghun Han1 , Yunsung Kang1 , Wonkyu Jung1 , Jun Lim1 and Jungwon Lee1
1 Samsung
Electro-Mechanics, Korea
In recent decades, thin film type PZTs have been spotlighted for MEMS applications because or their
excellent piezoelectric properties. PZT thin films have to be poled along one direction to have proper
piezoelectric properties. However there might be enormous loss in process time or costs by individual
chip poling. Furthermore, most of piezo-MEMS devices cannot be operated after poling process, it
is impossible to check the performance of device without wafer level poling. For these reasons, it is
essential to develop wafer level poling process for MEMS device.
In order to overcome conduction defects problems of wafer level poling for MEMS sensor device,
two types of processes were evaluated. Non-contact poling method using corona discharge showed
insufficient remnant polarization of 15 µC/cm2 with PZT surface damages. The other method supplied
excess current to the conduction defects of the PZT thin film, conduction path was eliminated. In this
way, wafer level poling was successfully demonstrated without any breakdown or degradation of MEMS
sensor devices. Remnant polarization of the poled PZT thin films was 20 µC/cm2 .
48
Effects of Nanoscale Confiment on Ferroelectric Properties: Research
Activity at the Center for Space Human Robotics
V. Cauda1 , G. Canavese1 , S. Stassi1 , M. Lombardi1,2 , R. Gazia1 , I. Aulika1 , M. Quaglio1 , C.F. Pirri1,2
1 Center
for Space Human Robotics, Italian Institute of Technology, C.so Trento 21, Turin, 10129, Italy
Science and Chemical Engineering Department, Politecnico di Torino, Turin, Italy
2 Materials
The activities of Center for Space Human Robotics (CSHR), part of the Italian Institute of Technology (IIT), are focused on the development and prototyping of integrated systems for human robotics.
Particular interest is devoted to the design and fabrication of a hand-exoskeleton for motion support in
both space and human activity. The fabrication of a hand-exoskeleton requires the development of: i)
actuators and sensors (e.g. tactile sensors) to properly manage the interface of the exoskeleton with
both the human body and the external environment, ii) electronics to manage the entire system, and iii)
energy sources and storage systems to power it. In this scenario CSHR has focused its activity on the
effect of nanoscale confinement on the piezoelectric properties of materials analysed in its three main
forms: thin films as 1D confined
structures,
nanowires
as 2DMEMS
confined
structures and hybrid materials
2nd International
Workshop
on Piezoelectric
2011
with nanosized fillers as 3D confined structures.
Figure 1. Polarization hysteresis and displacement curves obtained as a result of 3 cycles. Inset: Scanning
electron microscopy
image
the PVDF-TrFEcurves
nanowires
after dissolution
of the
membrane,
with
Fig. 1. Polarization
hysteresis
andofdisplacement
obtained
as a result
of alumina
3 cycles.
Inset: Scanning
electron
some residues of the dissolved alumina.
microscopy image of the PVDF-TrFE nanowires after dissolution of the alumina membrane, with some residues
of the dissolved alumina.
To obtain flexible and performing materials, piezoelectric hybrids based on barium titanate nanoparticles (npBT) dispersed in a 3D polymeric network were developed. In particular electroactive polyvinylidene fluoride (PVDF) or passive (UV-cured acrylic or epoxide resins) polymers were used as matrices.
Despite the npBT slightly affected the composite mechanical properties, they were able to improve the
thermal and functional behaviour. The effect of npBT size distribution and their crystalline phase were
evaluated. Another representative example of increased piezoelectric properties upon nanoconfinement
is given by 1D polymeric nanowires.
An ease and fast wet-impregnation method from a solution of PVDF copolymer (PVDF-TrFE) lead
in one step to an array of 1D piezoelectric nanostructures distributed in an insulating matrix, i.e. 60 µm
thick porous Anodic Alumina Membranes (AAM, Whatman, av. pore size: 200 nm) [1]. The polymeric
nanowires showed a diameter of about 150 nm, several micrometers in lengths and a high filling ratio of
the alumina pores (Inset of Fig.1). X-ray diffraction and infrared spectroscopy showed that the high level
of crystallinity is induced by the confinement into the pores of the AAM and results in a pronounced
49
piezoelectric effect. Hysteresis measurements were recorded simultaneously with sample displacement
data by a Piezo Evaluation System (TFAnalyzer 2000HS, Aixacct) coupled to a single point laser vibrometer (Polytec OVF-505), showing a polarization curve typical of ferroelectric material with a Pr of
approximately 14.3 µC/m2 (Fig.1) and coercitive field of 4.3 MV/m. It is noteworthy that the averaged
d33 constant (obtained from the linear part of the piezoelectric displacement curve) is about 97 pm/V,
which is quite higher with respect to the literature values (from 5 to 20 pm/V of pre-poled thin film of
PVDF-TrFE [2]). Despite the absence of pre-poling of the PVDF-TrFE nanowires, we attribute this
higher d33 value to the higher percent of polymer crystallinity, which is due to the confinement into the
pores of alumina.
As a future outlook, these crystalline piezoelectric nanowires distributed in vertical array can be engineered in a piezoelectrical MEMS device, thus potentially addressing applications like tactile sensors
for humanoid robotics.
[1] V. Cauda, et al., Sensors & Tran. J., 2011, accepted.
[2] V. Maheshwari, et al., Angew. Chemie, Int. Ed. 2008, 47, 7808.
50
Dr Eric Mounier1
1 Yole
Développement, France
Ferroelectric materials are historically not common for semiconductor manufacturing companies
who are often reluctant to adopt these exotic materials in their fabs. But this approach has changed in
the 2000s with the adoption of ferroelectric thin films by well known companies in a variety of markets.
We have analyzed and estimated the MEMS and non MEMS applications for ferroelectric thin films.
We particularly looked at the piezo effect of ferroelectric thin films for MEMS. In 2010, we estimated
ferroelectric thin film production is about 900 k 6” wafers. It is done through two main applications:
MEMS inkjet heads and IPD ESD/EMI planar capacitors that together represent 90% of the production.
Large companies (Epson, STM, NXP) have adopted ferroelectric thin films at a large industrial scale for
the past several years.
We estimate that, until 2015, the ferroelectric thin film business will continue to grow at rate of
+7.5% / year with many current or new MEMS applications: Wafer Level Autofocus, IR sensors, RF
switches, and medical ultrasonic transducers.
In non MEMS markets, ferroelectric thin filmswill be used for IPD tunable capacitor, IPD hearing
aids, FeRAM, optical switches. These applications will represent 26% of the total ferroelectric thin film
production in 2015 which will be more than 1,000 k 6" wafers.
Our talk will review the different applications and market volume for piezoelectric MEMS.
Page No.
Author
Title
Abergel, J.
Direct and Indirect Piezoelectric Characterization of PZT Thin
Films for MEMS Applications
40
Baron, T.
21
Baron, T.
FBAR filters for space application based on LiNbO3 membrane
16
Bharadwaja, R.
44
Bui-Thi, K.-A.
Properties of PMN-PT 65/35 thin film oriented -<011> at radio
frequency measured by coplanar waveguide
42
Cauda, V.
48
Chidambarm, N
Effective piezoelectric coefficients of PZT thin films for energy
harvesting with interdigitated electrodes
22
Chidambarm, N
Interdigitated Electrodes Based Cantilevers for Piezoelectric
Energy Harvesting
26
Felmetsger, V.
Reactive Magnetron Sputtering of Ultrathin Piezoelectric
23
Felmetsger, V.
Sputter Deposition of Piezoelectric AlN Thin Films on Vertical
Walls of Micromechanical Devices
12
Gariglio, S.
8
Gariglio, S.
37
Han, S.
47
Han, S.
Ferroelectric Properties of PZT Films Deposited by RF
24
Harigai, T
3
Jackson, N.
Influences of Titanium Underlayer on (002) Oriented Aluminium
Nitride
25
Janphuang, P.
8
Janphuang, P.
35
Janssens, A.
Introduction of new manufacturing technology for Piezo (PZT)
MEMS production
36
Kaden, D.
38
Kaden, D.
Measurements of Electrical and Electromechanical
Characteristics of Piezoelectric Thin Films and Optimization of
Poling
37
Kang, S.-Y.
Ferroelectric Properties of PZT Films Deposited by RF
24
a Kang, S.-Y.
44
Kessels, R.
Poling
37
Kessels, R.
38
Kijima, T.
Kirby, P.
Spin-Coat Technology of KNN Film Deposition with Oxygen
Pressurizing RTA
Piezoelectric MEMS Fabrication Integrating Thermally and
Mechanically Incompatible Materials
41
31
Klee, M.
4
Kosec, M.
41
Kratzer, M.
38
Le Rhun, G.
Poling
39
Le Rhun, G.
40
Lombardi, M.
45
Malic, B.
43
Mathewson, A.
Influences of Titanium Underlayer on (002) Oriented Aluminium
Nitride
25
Matloub, R
Electromechanical properties of Al0.9Sc0.1N thin films evaluated
at 2.2 GHz Film bulk acoustic resonators
15
Mauczok, R.
4
Mazzalai, A.
Effective piezoelectric coefficients of PZT thin films for energy
harvesting with interdigitated electrodes
22
Mazzalai, A.
Interdigitated Electrodes Based Cantilevers for Piezoelectric
Energy Harvesting
26
Mazzalai, A.
36
Metzger, T.
New Trends in Piezoelectric Devices for RF Application in Mobile
Phones
13
Milyutin, E.
15
Milyutin, E.
Local Polarity Control of (001)AlN Thin Films
27
Moulard, G.
New Trends in Piezoelectric Devices for RF Application in Mobile
13
b Phones
Mounier, E.
Muralt, P.
15, 22, 26,
27, 29, 38,
39, 45
14
Pensala, T.
Piezoactuated AlN-Si MEMS Resonators and Sensors
Phair, J.
using Piezo MEMS
46
Pham-Thi, M.
Hyper Frequency properties of “3 inches-frozen capacitive
MEMS” with PZT thin films processed by sol-gel
28
Pham-Thi, M.
Properties of PMN-PT 65/35 thin film oriented -<011> at radio
frequency measured by coplanar waveguide
42
Piazza, G.
Laterally Vibrating Micro and Nanomechanical Piezoelectric
Aluminum Nitride Resonators for RF Communications and
Chemical Sensing
11
Piorra, A.
Lead Free Laser Deposited Thin Films Of 0.5(Ba0.7Ca0.3TiO3)–
0.5(Ba(Zr0.2Ti0.8)O3)
17
Pirri, C. F.
48
Polcawich, R.
5
Remiens, D.
Performances of Piezoelectric Nano Structures
10
Rijnders, G.
All-oxide PiezoMEMS Devices by Pulsed Laser Deposition:
Properties of Clamped Epitaxial PZT Thin Films
35
Rosenfeld, D.
using Piezo MEMS
46
Sandu, C.
15
Schreiter, M.
Thyholdt, F.
Piezoelectric MEMS based energy harvesting module for
wireless tire pressure monitoring
FP7 piezoVolume - High Volume Piezoelectric Thin Film
Production
Process For Microsystems
6
45
Tiedke, S.
Poling
39
Tiedke, S.
40
18
44
Active Damping with a piezoelectric MEMS device
29
Modelling of piezoelectric micromachined ultrasound transducers
(pMUT) for medical use
30
TrolierMcKinstry, S.
TrolierMcKinstry, S.
Verdot, T.
Vogl, A.
50
c Vullers, R.
AlN and PZT Thin Films: Essential Ingredients for Piezoelectric
Energy Harvesters
7
Welsh, A.
18
d 

- International Workshops on Piezoelectric MEMS

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