EFG-Wafer

SOLAR
SolarInnovativ Thüringen
Welcome to
SCHOTT Solar
Europe's largest producer of
PV solar electricity components
EFG, ein kostengünstiges
Produktionsverfahren für Si-Wafer
Dr. Ingo A. Schwirtlich
SolarInnovativ Thüringen
25. / 26. Oktober 2006
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SolarInnovativ Thüringen
The SCHOTT Synopsis
*
!
" # $% % %
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PHOTOVOLTAICS
DASA
AEG Telefunken
50%
100% NUKEM GmbH
100% TESSAG
MBB
100%
AG
Solutions
RWE
PST
ASE GmbH
NUKEM
Mobil Tyco
Solar Energy
1960
1970
1980
RWE Solar GmbH
SCHOTT
Solar GmbH
RWE SCHOTT Solar
GmbH
50%
Mobil Solar
Energy
1990
Joint Venture
RWE Solutions
SCHOTT Glas
ASE Americas Inc.
ASE Americas Inc.
1994 1996 1999
2001
2001
RWE SCHOTT
Solar Inc.
2002
2005
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SCHOTT AG
SCHOTT Solar Group
Employess: ca. 900 world-wide
Turnover: ~320 Mio. in 2006
(forecast)
SCHOTT Solar GmbH
Subsidiaries 100 %
SCHOTT Solar, Inc.
Billerica (MA) USA
Fully integrated production
of wafers, cells and modules
SCHOTT Solar Inc.
Rocklin (CA) USA
System integration
Sales of modules and
systems
RWE SCHOTT Solar CR
Valasske Mezirici, CR
Production of modules
Alzenau, Headquarters
Fully integrated production of
wafers, cells and modules
Phototronics
(PST) Putzbrunn
Production of thin film modules
Jena
Buildup of a 30 MW production
line of ASI thin film modules
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SmartSolarFab® - Alzenau
OEM Zellenfertigung
Heilbronn, D
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The Value Chain of the SCHOTT Solar Group
Modules
Cells
Wafer
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24% (15)
17%
18 %
poly Si
Wafer
26% (25)
14 % (20)
10 %
Cell
25 %
Module
36% (40)
Increasingly important
is the industry to produce
manufacturing equipment
and materials for the
whole value chain.
100 % (100)
15 %
BOS
15 %
Installation
100 %
Today's 2005 Value Added Chain for
grid-connected PV Systems
(2004 in brackets)
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Relative Module Manufacturing cost as Function of
Efficiency
relative module cost (%)
130
mc = 1
120
CZ/Ga = 1.5
mc
110
100
EFG = 0.7 mc
90
CZ/B = 1.35
mc
80
70
10
12
14
16
18
20
22
24
Efficiency [%]
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Advantages of ribbon technologies
Energy Pay-Back Time [a]
5
4
BOS
frame
laminate
3
2
1
0
ribbon ribbon
S-Eur. M-Eur.
multi multi
S-Eur. M-Eur.
mono mono
S-Eur. M-Eur.
From: E. Alsema et al. 20th EUPVSEC 2005
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Estimated reduction of silicon consumption
16
14
g Si/Wp
12
10
mono / multi - Si
15 % EFG
85 % mono / multi - Si
8
6
EFG
4
2
0
2005
2010
2015
2020
2025
Specific feed stock consumption per Wp for different wafer technologies
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Si - Blockguß
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Blockguß-Anlage
Deutsche Solar Freiberg
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Silicium - Block
Abmessungen:
66 cm x 66 cm
Gewicht:
ca. 250 kg
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Säulenherstellung
Deutsche Solar Freiberg
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Drahtsägetechnik
slurry & abrasive
ingot
main drive
slave drive
wire web
Typische Sägeparameter
Drahtdurchmesser
150 - 250 µm
Öl- oder Glykol-basierte Slurry
Drahtgeschwindigkeit
SiC Vol. Anteil
5 - 15 m/s
30 - 60%
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Multikristalline Silicium - Scheiben
Multikristalliner Wafer aus dem
EFG-Wafer nach dem Folienziehverfahren
Blockgußverfahren
von SCHOTT
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SmartSolarFab® - Wafer Production
EFG-Wafer Production
(Edge-defined Film-fed
Growth)
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Productivity Increase and Cost Reduction for c-Si
Wafers
1990
Actual
2003
1. Step
2. Step
3. Step
Long-Term
450
300
200
150
100
50 (-83%)
Tube circumference [dm]
9x0,5
4,5
8x1
8
8x1,25
10
12x1,25
15
12x1,5
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Productivity
Material add-on
Personnel
Depr/Interest
0,6
2
1,5
1,5
1(norm.)
1
1
1
1,2
1,2
1
1
1,9
1,7
1,1
1,1
2,2
2
1,2
1,2
circle ∅ 1,3m
40
5
4 (-20%)
1,3 (-74%)
1,3 (-74%)
Si-Material
Wafer Thickness [µm]
EFG-Wafer
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EFG history
v. Gompertz 1922: Growth of metal wires from a wetted
capillary.
LaBelle 1971: EFG of sapphire tubes.
Ciszek 1972: EFG of silicon ribbons.
Taylor 1981: EFG of polygonal silicon tubes (nonagons
with 50 mm faces).
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EFG of silicon octagons
Wald 1985 (Mobil Solar Energy):
production of silicon octagons
EFG
with 100 mm faces.
RWE SCHOTT Solar 2003:
production of silicon octagons
faces.
EFG
with 125 mm
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Edge-defined film-fed growth (EFG)
vs
Crystal thickness t = f(vs, T, h, wetting angles)
Fixed: h, wetting angles
Control parameters: vs, Tmelt
t
crystal
1412 °C
T
wetting
angles
h
die
melt (Tmelt)
T
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EFG crystal growth: schematic
Silicon Tube
Octagonal Die
Molten Silicon
Induction Heater
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125 mm EFG: scales
7m
0.3 mm
125 mm
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100 mm and 125 mm octagons
Increase of throughput by more than
25 %.
No loss of materials quality.
No increase of wafer thickness.
0
10
20
30 cm
Increase in productivity by growing 125 mm wide faced octagons instead of 100 mm
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Cutting of tubes by laser
for wafer production
Several tubes per day and furnace
up to 7 m length.
Less than 10 % silicon loss at cutting
step.
Wafers are immediately processed
after light etch.
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6x150mm growth
First 150x150mm samples
100x100
125x125
150 x 150
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EG wafer properties:
carrier lifetime distribution
As grown lifetimes up to 10 µs.
The distribution mainly correlates to dislocation density variations.
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Access
Buckling
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Advanced process modeling:
3D stress and strain
v
45 MPa
tensile
stress
-45
MPa
compressive
Non-uniform cooling of edges and faces
can result in tube deformation during
growth.
Danger of remaining deformations by
residual stress, creep and plastic
deformation.
interface
In collaboration of ACCESS e.V., Aachen
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Latest stage of development:
Dodekagons
Oktagon 125 mm
Dodekagon 125 mm
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200 micron thin EFG silicon wafers
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EFG wafer properties: mechanical strength
100
Failure rate [%]
90
80
70
60
50
40
mc - Si as grown
mc - Si damage etched
EFG as etched
30
20
10
0
0
100
200
300
400
500
600
700
800
900
1000
1100
Fracture strength [MPa]
Biaxial test: fracture strength of 550 MPa
(60% failure rate value) for EFG.
As-grown surface is free of serious damage.
In collaboration with TU Freiberg
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Wafer breakage?
Elaborated crack free edge design and stress free volume
is required to minimize breakage of thin wafers.
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EFG wafer properties:
wafer edge
As cut, 4 min Sirtl etched
Standard etched
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PHOTOVOLTAICS
SmartSolarFab® - Cell Production
EFG-Zelle
EFG-Zelle
2
2
100 x 100 mm 125 x 125 mm
MAIN-Zelle
MAIN-Zelle
2
2
100 x 100 mm 125 x 125 mm
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PHOTOVOLTAICS
Process sequence for the fabrication
of EFG solar cells
Wafer cleaning
P - doping
Rear side metallisation
Solder pads
Al-contact
Oxide-etching
Front side contact
& Firing
ARC-deposition
Final inspection
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PHOTOVOLTAICS
SmartSolarFab® - Module Production
High Quality
Modules
ASE-275-DG-FT
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SolarInnovativ Thüringen
Many thanks for your attention
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