Obducat NIL operating Manual

1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Obducat NIL 2.5 inch Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 March 20, 2014 • Imprint area: 65 mm in diameter • Any size and shape of substrate/stamp • SoW pressure • Uniform temperature • Liquid nitrogen cooling possibility • Substrate/stamp holding/loading arm • SoWware controlled Material Restric\ons ALLOWED NOT ALLOWED Hard substrates PMMA based (thoroughly baked) resists An\-­‐s\ck layers (ASL) Acids Bases Dusty materials Anything that outgasses anything hazardous Februari 2004
Needs for imprint
• Stamp
– Pattern profile, height, area coverage
– Anti-sticking
– Thermal expansion
– Clean
• Substrate
– Thermal expansion
– Surface properties
• Polymer
– Properties (Tg, molecular weight, flow rate, ….)
– Imprint and release Temperature
– Spin coating, thickness, uniformity
– Clean
Slide 7
Obducat, 2004, Confidential
WCAM, ObducatNIL_opera\ngprocedure.pptx 1 1550 Engineering Drive Februari 2004
Engineering Centers Building Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Madison, WI 53706 Imprint method
Process Overview: The process of transferring hard, topographical paberns to a substrate can be address in three main steps: 1.  The actual imprin\ng process, or using pressure and temperature to apply the stamp to the substrate. 2.  Ashing the stamped out areas to create window to the substrate material, where the resist masks the rest of the substrate. 3.  Etching the substrate to create the pabern topography. In this opera\ons manual, we will only discuss, in detail, the steps to carry out step 1 (above). Detailed steps for carrying out steps 2 and 3 will be highly materials dependent. General opera2on: The Obducat Nano-­‐Imprint Lithography machine uses compressed air to provide a uniform, conformal Slide 2 Obducat, 2004, Confidential
force on thin sheets of soW aluminum foil, which Soft versus hard pressing
Soft press technique
then presses down on the stamp/substrate combina\on. This allows for materials that are not perfectly flat to s\ll be uniformly imprinted. It is important that the upper substrate (stamp or substrate) be smaller than the lower substrate (stamp or substrate) because the pressure that is applied will otherwise crack the larger wafer (if the M. Efremov, A. Kiyanova, Slides (2005) larger wafer is on bobom). Stamp prepara\on: Stamps must be extremely clean and par\cle free. If the stamps are silicon, it is recommended that they be cleaned in RCA-­‐1 to remove organics and par\culates, and then coated with an An\-­‐S\ck Layer (ASL – typically some type of silane with a very long chemical name like heptadecafluorodecyltri-­‐
methoxysilane, or similar). Stamps should also have a wedged (or trapezoidal) z-­‐profile to avoid resist (top): If the substrate does not have a suppor\ng structure gefng under the stamp protrusions. underneath, the pressure from the air/aluminum foil will break 1.
1.
Pressure is applied
hydraulically without
any rigid piston
2.
2.
The result
The result
The result of hard pressing is
very sensitive to stamp/substrate
thickness variations.
WCAM, ObducatNIL_opera\ngprocedure.pptx the overhanging lip. (bobom) contact between the aluminum foil and the stamp will cause premature wear to the stamp surface. 2 1550 Engineering Drive Engineering Centers Building 2004
Madison, Februari
WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Imprint Equipment
Press method
It is highly recommended that the samples to be coated with the ASL be handled only by the die sides to minimize par\culate contamina\on by tweezers contac\ng the surface. The substrate to be paberned, is spin coated with a PMMA type resist with a thickness matching the stamp height. If the resist is too thin, premature wear of the stamp could result. If the resist is too thick, it may be difficult to remove the stamped resist while maintaining sufficient thickness of the masking resist. Air or Nitrogen
Februari 2004
Imprint uniformity: ±10nm
Slide 4
Obducat, 2004, Confidential
Cooling 1
pressure
Pressure chamber
O-ring
Aluminum foil
Substrate/stamper
Stamp/Substrate
Vacuum
The stamp is lightly pressed on the resist and placed into the stamping area to keep it from sliding during the loading process. The wafer is placed on a pre-­‐pressed sheet of Aluminum foil (serving as a base to keep the unit clean), and typically 1-­‐3 sheets of Aluminum foil above the samples. The redundancy serves to minimize leaks from poten\al punctures through the foil, if that should occur. Heat is applied to a temperature roughly 50 °C above the glass transi\on temperature of the resist before the pressure is applied. The pedestal will automa\cally lower itself once the required set point is achieved. Substrate
loader
Temperaturer sensor
Vacuum
Cooling 2
Solid-State Heater
Slide 6
Obducat, 2004, Confidential
 Recommendations
Right aluminum foil for imprinting should be:
- made from alloy 1xxx (contains more than 99% of aluminum);
-  annealed (suffix –O in the name of the alloy);
- clean room compatible (oil-free);
-  2 bright sides.
We use alloy 1145-O oil-free foil from Alufoil Products Co.
Note: typical shim stock aluminum foil:
- is hardened (suffix -H16, -H18, -H19);
- can be 3xxx alloy with manganese;
- is not oil-free.
M. Efremov, A. Kiyanova, NIL notes, 2005 Note: the sliding door is interlocked to the machine opera\on – if the machine does not seem to respond, please check that the door is fully closed and the interlock is func\onal. •  Stamp fabrica\on – posi\ve slopes with depth matching resist height. ASL coa\ng usually doesn’t hurt. •  Stamp cleanliness is cri\cal. Stamps may benefit from long acetone or ace\c acid ultrasonic cleanings in between uses. •  Stuck stamps may be coaxed off without breaking stamp or wafer if ASL was applied. Without ASL, stuck stamps need to be soaked in solvent otherwise the risk of breakage if high. Suitable aluminum foil in disk form (leW) from Obducat (~$2.50 per foil), and in roll form (right). 3 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Trouble shoo\ng: System does not respond to any commands. Did you close the protec\ve door to close the interlock? Plasma etch parameters for PMMA 950 C9 on PT790 (RIE only): “250W_O2” (10 mTorr, 10 sccm O2 flow, 250 W RIE) for ashing -­‐-­‐ ~0.5um/minute etch rate. “Z29_TEMP” for etching 2” (111) Silicon wafer. (0.49 um/min at DC bias : 39-­‐42 V) ASL applica\on procedure – Done at the SoW Materials Laboratory in Engineering Hall (Contact: Drs. Anna Kiyanova/Mike Efremov). The silane is vaporized under vacuum in a dessicator within a nitrogen glove box. The vapor coats everything inside the dessicator including your samples. Samples can be used mul\ple \mes with each ASL coat. Maintenance info. Leaks – the leak rate is nominally 0.03 bar/s in a well tuned system from the factory. This can increase over \me and use with the effect of having pressure oscilla\ons that are more frequent and larger in magnitude, which can affect the fidelity of the final pabern. Use of Snoop® is advised on the fifngs above the tabletop to detect leaks. Nitrogen glove box used for ASL coa\ng. Available in SoW Materials Laboratory (Contact: Dr. Anna Kiyanova) PID parameters – Previous users have men\oned that the system was either not op\mized or that the PID parameters were improperly adjusted. Obducat has told me that these sefngs should not need to be adjusted for most cases. IP informa\on: The computer should be set to an I.P. address of < . . . >, and the Obducat NIL machine should be set to < . . . > Contact at Obducat: Peter Göransson [email protected] 4 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Procedure 1.  Login to CRESS 2.  Open IMPRINT soWware 3.  Press on screen bubon to connect to NIL machine (it should say “Disconnect” aWer you press it), Press the vacuum connec\on bubon (vacuum holds the substrate to the chuck, or in our case the bobom Al foil to the chuck) to confirm connec\on to computer. 4.  Enter imprint parameters on Imprint tab, check/
validate (There is an on screen bubon you can press to do this). WCAM, ObducatNIL_opera\ngprocedure.pptx 5 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Place Al foil(s) on pedestal (without samples), lock stage in place with (giant) pin. 6.  Close glass door on protec\ve frame to ac\vate interlock. 7.  Run recipe to imprint foil(s) without samples (this is op\onal, but may minimize lateral movement between stamp and substrate during the imprin\ng process.) 8.  The hea\ng pedestal will automa\cally lower when it is done (unless you open the door early and ac\ve the interlock – in which case it won’t go down) Let system cool a bit. 9.  Place your samples (substrate & stamp(s)) on pedestal between Al foil sandwich. 10.  Lock stage in place with (giant) pin 11.  Press the “Run imprint” bubon no the screen. 12.  Remove samples aWer pedestal has lowered and has sufficiently cooled. Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 5. 
WCAM, ObducatNIL_opera\ngprocedure.pptx Al foil disc aWer imprin\ng Interlock sensor – door has to be lowered or system does not respond 6 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Sample Recipies (2014): For crea\ng large paberns: S1811 resist paberned on Si (111) wafer Unaxis790 recipe For Si etching on (111) 2” wafer – Z29TEMP.PRC etches Si about 2.25 um/min For Ashing of PMMA, I used 250W_O2 (3.5-­‐4.0 minutes seems to be good for removing the pressed PMMA C9 (nominally ~2.5-­‐3.0 um thick before pressing) Pirahna-­‐HF-­‐RCA1 clean Spin coat of PMMA950 C9 (2.0-­‐2.5 um thickness, could be thicker because spinner not currently programmed to spin sufficiently long (> 30 s)) Bake 180C/1 min on hotplate NIL process: Stamps on top of baked PMMA 1 foil below, 3 above WCAM, ObducatNIL_opera\ngprocedure.pptx 7 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Pressure&troubleshooting&
To#analyze#if#there#is#a#leakage#in#the#pressure#chamber#in#the#top#we#have#to#do#a#test.#The#
test#is#to#remove#the#pressure#hose#(that#goes#to#the#top,#see#picture#below)#and#see#if#the#pressure#
problem#still#exists.#
#(The#pictures#and#the#components#can#sometimes#be#a#little#different#from#your#imprinter#
depending#what#version#there#is,#the#procedure#is#still#the#same).#
#
#
Remove#left#side#door.#The#tube#in#the#red#ring#goes#up#to#the#pressure#chamber.#Remove#the#
hose#and#plug#it.#
#
#
Now#the#pressure#is#blocked#to#the#chamber.#
When#this#is#done#please#run#an#imprint.##
For#example:#Set#30#degree#and#70#bars#60#seconds.##
If#the#process#goes#well#(stable#pressure)#then#you#have#a#leak#in#the#pressure#chamber.#
&
&
&
WCAM, ObducatNIL_opera\ngprocedure.pptx 8 1550 Engineering Drive Engineering Centers Building Madison, WI 53706 Phone: (608)262-­‐6877 FAX: (608) 265-­‐2614 Pressure&chamber&leak&troubleshooting&
&
1. Make'sure'to'use'new'membranes'(poly'foil/alu'foils)'during'imprint'process,'sometimes'the'
sheets'can'be'cut'due'to'sharp'edges'on'the'samples'
'
2. Change'OAring'
a. Test'pressure'
'
3. Check'UVAquartzAglass'
a. Glass'must'be'solid.'No'cracks'are'allowed.'
b. Test'pressure'
'
4. Check'pressure'connection'
a. Remove'pressure'hose'
b. Tighten'coupling'
c. Reattach'hose'
d. Test'pressure'
'
Pressure'hose'
5. Use'gas'leak'spray'(or'water)'
a. Apply'high'pressure'(40'bar)'
b. Spray'coupling'
c. Spray'around'OAring'
d. Spray'around'UV'base'
'
Coupling'
'
'
UV'base'
9