Cluster I
Texture :- Chetankumara K
Diffusion :- Sneha B
LDSE :- Gagan K S
Emitter Annealing :- Swati B
Texturing Process in TOPCON
Solar Cells
By:Chethankumara K
Cell Process
EPPPL, Bengaluru
Outline
• Safety
• Objectives
• Texturing Area
• Texturing Machine
• SIPOC
• Process Flow Diagram
• Texturing Defects
• Process control parameters
• Process Measurement tools
Safety
Personal Protective Equipment (PPE)
• Wear clean room dress in Safety Glass Full Body Apron
gowning area.
• Always wear the full body
Mask
apron.
• Take the air shower, Do not by
pass the air shower.
• Do not enter the clean room Hand gloves
without clean room dress
Shoo cover
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Chemical suit
• Always wear chemical suit during the chemical handling
Chemical resistive boot Face Shield Chemical Suit
Chemical resistive gloves Chemical respiratory mask
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Objectives
• Saw Damage Removal(SDR): To get clean and smooth surface.
• Texturing: to reduce reflection of the surface by the formation of
Pyramids.
Texturing Area
source: ©EMMVEE
Texturing Machine View
source: ©RENA Technologies
SIPOC
Suppliers Input Process Output Customers
Raw wafers(GCL & Raw Wafers To remove the Saw Textured Wafer, Boron
longi) Chemicals: KOH, DI damage . Exhaust gas, Waste trichloride(BCL3)
Chemical suppliers water, Ozone, HF, Making pyramid Chemical Diffusion
Gas (LINDE) Additives Formation to reduce
Utilities Power. the reflection
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Loading
Process Flow Diagram
SDR PSC-1 Rinse-1 Texturing-1
HF Clean DI and O3 Rinse-2 Texturing-2
HWD WAD-1 WAD-2 WAD-3
Unloading
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Loading
Wafer loading Cassette
source: ©EMMVEE
Loading Automation
source: ©EMMVEE
Carrier Loaded with Wafer
source: ©google
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Saw Damage Removal (SDR)
• In this Process we remove the surface scratches
and Saw marks on the wafer surface using
Potassium hydroxide(KOH) and Deionized(DI) water.
source: ©EMMVEE
source: ©fraunhofer
Source: © Nakamura Choukou Co.,Ltd.
13
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Saw Damage Removal
Wafer Surface + Etchant Water Soluble product + Gas
Standard condition Alkaline
Concentration of KOH 2 wt.%
Process Duration 3 minutes
Bath Temperature 80 degrees
source: © RENA
KOH + H2O 2(OH)- + K+
(Potassium hydroxide) (Hydroxide) Removed
Si(surface) + 2(OH)- SI(OH)+2 + 4e- through
exhaust
(silicon hydroxide)
Si(OH)+2 + 4e- + H2O Si(OH)-6 + 2H2
(Hexahydroxy silisic acid) Soluble in
water
Si(OH)-6 + 2K+ Si(OH)2K2(aq.)
(
Pre Standard Cleaning (PSC-1)
• In this process to remove the metallic and
organic contaminants by using KOH and H2O2
and DI water
Standard condition Alkaline
Process Duration 3 minutes
Bath Temperature 60° C
Concentration of KOH and H2O2 KOH: 1Wt.%
H2O2: 1 vol.%
source: © RENA
13 December 2024
source: ©EMMVEE 15
Rinse-1
• In this process we are using only DI water for
cleaning the chemicals in Rinse bath.
• Other wise chemicals will react with each
other.
• Chemicals:
Deionized (DI) water
source: ©EMMVEE
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Texturing-1 and-2
❖Purpose: To reduce the reflection by the formation of pyramid structure
source: © RENA
source: ©EMMVEE
Si(surface) + 2 KOH+ H 2O K2SiO3 + 2 H2
(Potassium silicate)
Texturing
❖Additive: in this process we use Additive, For Homogeneous & uniform
Texturing.
❖Process Parameters
Standard Condition
Duration 6 minutes
Bath Temperature 85 0C
Concentration of KOH and Monotex KOH :1.7 wt.%
Monotex: 0.7 wt.%
source: © RENA
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Rinse-2
• In this process we are using only
DI water for cleaning the
chemicals in Rinse bath.
• Other wise chemicals will react
with each other.
13 December 2024 source: ©EMMVEE 19
Deionized Water and Ozone Clean-( DI water and O3)
• O3 °
O2+O
• RH °
R-O oxidized the Organic
radicals
source: ©EMMVEE
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Deionized Water and Ozone Clean-( DI water and O3)
• Process Control Parameters
Standard condition
Duration 2 min
Bath Temperature 40° C
source: © RENA
High Eta (HE) Clean
• SiO2+ 4HF SiF4 + 2H2O
Hydrogen fluoride Silicon Tetrafluoride
• SiO2 + 4Hcl SiCl4 + 2H2O
Hydrochloric acid Silicon tetrachloride
13 December 2024 source: ©EMMVEE 22
High Eta (HE) Clean
• Process Control Parameters
standard condition
Duration 3 min
Bath Temperature 50° C
Concentration of HF and HCl HF:3 vol.%
HCl : 2.5 vol.%
source: © RENA
Hot Water Dryer (HWD)
• In this Process to remove the stain marks and clean
the wafer.
standard condition
Duration 3 min
Bath Temperature 60° C
source: © RENA
source: ©EMMVEE
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Warm Air Dryer (HAD)
• They are three warm Air Dryer are there due
to Increase the production and reduce the
cycle time.
• In this Process remove the moisturing content
and Dry the wafer surface in Hot Air
standard condition
Duration 7 min
Bath Air Temperature 90° C
source: © RENA
13 December 2024 source: ©EMMVEE 25
Unloading Automation
source: ©EMMVEE
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Texturing Defects
• Defect:-Colour Variation
• Causes:-
• Incoming wafer quality
• chemical concentration is low
• Solution:-
• Validate the incoming wafer quality
• Ensure bath chemical concentration
Defect:-Saw Marks
Cause:-
Incoming wafer quality
Solution:-
Validate the wafer quality
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Texturing Defects
• Defect:- Finger Mark
• Causes:-
• Touch the wafer with broken/ contaminated gloves
• Action:-
• Provide Training /TBT to working person
Defect :- White Spot
Cause:-
The solution mixed unevenly /Contamination in
bath/K2SiO3(waste chemicals) residue
Solution:-
Stirring enough before texturing /clean texturing Bath/refill Bath
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Process Control Parameters
• Temperature
Temperature increases Etching rate increases
Temperature Decreases Etching rate Decreases
• Process Duration
Process Duration increases Etching rate increases
Process Duration Decrease s Etching rate Decreases
• Chemical Concentration
Concentration increases s Etching rate decreases
Concentration increases Etching rate Decreases
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Process Control Parameters
• Etching weight: 0.30-0.4 Grams
• Etch depth 2-3 micron,
Initial Weight – Final Weight
Etch Depth =
Silicon Density * Area of the cell
Reflectivity
source:©Zhejiang Dongshuo New Energy
Before Etching 30-35%
After Etching 9-10%
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Process Measurement Tools
• Reflectivity Measurement tools:-
Spectrophotometer
Spectrophotometer
source: ©fraunhofer
• Pyramid size Measurement tools:- 3D
Microscope
3D Microscope
source:©Olympus Microscope
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