RENA+GmbH+硅片制绒清洗机


New innovative acid and alkaline texturing process for silicon wafers
Michael Michel, Jens Krümberg, Stefan Mathijssen, Michael Schmidt, Ihor Melnyk, Ludger Heiliger, Julian Pr?l?, Simon Braun, Olaf Rogge, Hartmut Nussbaumer, Jennifer Wu, Colin Ying

SNEC (2009) 3rd International PV Power Generation Conference

New innovative acid and alkaline texturing process for silicon wafers ? Survey texture ? Acid texture ? Improved acid texture ? Alkaline texturing ? New alkaline process

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Texture: first production step

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Survey Texture I Reduction of the reflection Light Trapping Improved collection probability of carriers Larger contact area Larger surface area Homogeneous and dark appearance of the wafer
second chance of absorbtion

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Survey Texture I Reduction of the reflection Light Trapping Improved collection probability of carriers Larger contact area Larger surface area Homogeneous and dark appearance of the wafer

light trapping

longer optical path

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Survey Texture I Reduction of the reflection Light Trapping Improved collection probability of carriers Larger contact area Larger surface area Homogeneous and dark appearance of the wafer

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Survey Texture II

Batch process vs inline process

Batch: Mono wafer Multi wafer

Inline: Mono wafer Multi wafer

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Survey Texture III

Acid process vs alkaline process
Acid process Inline: Mono wafer Multi wafer Batch: Multi wafer Alkaline process Inline: -Batch: Mono wafer

Iso-texture saw demage needed

Anisotropic etching [100] crystalI needed

acid texture

as cut wafer

Alkaline texture
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Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

Acid Texture

Acid process ? Removal of saw demage ? Creating texture ? Cleaning before diffusion

Common process: UKN – process (Patent Universit?t Konstanz) Universit? Other processes: ? UKN - like ? ECN-process
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 9

Acid Texture

UKN - process
? ? ? ? ? ? HF, HNO3 and water, “easy process ” process” No organic chemicals Etch depth (<5 ?m/side), etch time (<3 min) Low temperature process Bath lifetime ~ 500000 wafer Analytic ? ? Inline: FTNIR (GP, RENA, ThermoFischer) Offline: Ion analyser (GP, RENA, Metrohm)

Reaction: 3 Si + 4 HNO3 + 18 HF → 3 H2SiF6 + 4 NO + 8 H2O
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 10

Acid Texture

UKN – process production data
Eff. % Voc V Isc A FF %

Inline acidic texturing (InTex) POCl3 emitter diffusion P-glass etching PECVD SiNx-deposition Printing and firing of contacts Laser edge isolation

acidic textured 156 mm mono-Si wafers Average 16.65 0.627 8.147 77.89

acidic textured 156 mm multi-Si wafers Average 15.84 0.614 8.211 76.48

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Acid Texture

UKN – process production data
Eff. % Voc V Isc A FF %

Inline acidic texturing (InTex) POCl3 emitter diffusion Wet chemical edge isolation and P-glass etching (InOxSide)

Acidic textured 156 mm multi-Si wafers Average 16.21 0.623 8.071 78.31

PECVD SiN x-deposition Printing and firing of contacts

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Improved Acid Texture

Improved acid texture: InTex plus texture:
? ? HF, HNO3, sulfuric acid and water Cost of ownership (CoO) reduction (CoO CoO) (~20% for the chemicals) Increased efficiency Reduce grain boundary etching

? ?

Cooperation: Cooperation:

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Alkaline Texture

Standard KOH-IPA process
? ? ? ? ? ? ? KOH, IPA and water Etch depth (~ 10 ?m/side), Etch time (~ 30 min) Temperature ~ 80 ° C 80° Bath lifetime ~ 500 - 5000 wafer Small process window Analytic ? Inline: FTNIR (GP/ThermoFischer)

Reaction: Si + 2 KOH + H 2O → K2SiO3 + 2H 2
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 14

Alkaline Texture

Standard KOH-IPA process: Current process issues process:
Wafer from one supplier: Significant difference in texture quality wafer to wafer.

Defects leading to optical downgrade

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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New Alkaline Process

One recipe for all wafer?

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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New Alkaline Process

GP AlkaTex Plus process
? ? ? ? ? ? ? KOH, IPA, additive and water Etch depth (~ 10 ?m/side) Etch time (~ 20 min) Temperature ~ 80 ° C 80° Bath lifetime ~ 8000 - 12000 wafer Large process window Every wafer can be textured!

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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New Alkaline Process

GP AlkaTex Plus vs standard process
? Shorter process time ~ 20 min ? Fewer bath changes necessary ? Up to 3 times longer bath lifetime ? Higher throughput (up to 30%) ? Less chemical consumption (IPA, KOH, water) ? Less vulnerable to incoming wafer quality ? Increase of cell efficiency (~ 0.1%) ? Increase of optical yield ? More homogeneous texture

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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New Alkaline Process

SEM picture of AlkaTex Plus textured wafer

SEM picture 45 ° tilted view 1000x (l.) and 5000x (r.) of a GP AlkaTex plus textured 45° wafer.
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 19

New Alkaline Process

Reflectivity measurement
50 45 40 35 Reflexion (%) 30 25 20 15 10 5 0 300
std. KOH-IPA GP AlkaTex Plus

400

500

600

700 800 Wavelenght (nm)

900

1000

1100

1200

Reflectivity of standard KOH / IPA textured wafer (avg. Reflectivity = 11.7% 400-1100nm) and new GP AlkaTex Plus textured wafer (avg. Reflectivity = 10.5% 400-1100nm).
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 20

New Alkaline Process

Cost of Ownership I
350'000 700.0

300'000

600.0

250'000

500.0

Wafer/week/5 bath

200'000

400.0

150'000

Costs/ 1000W afer

300.0

100'000

200.0

50'000

100.0

0 KOH-IPA (basic user KOH-IPA (basic user min) max) KOH-IPA (adv. User min) KOH-IPA (adv. User max) GP Alkatex Plus

0.0

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

Cost ()
21

W afer /week/ tool

New Alkaline Process

Cost of Ownership II
Consumption/Week/Bath

700 KOH (l, 40%) 600 IPA (l) DIW (l) 500

7000

6000

5000

400

4000

IPA, KOH [l]

300

3000

200

2000

100

1000

0 KOH-IPA (basic user min) KOH-IPA (basic user max) KOH-IPA (adv. User min) KOH-IPA (adv. User max) GP A lkatex Plus

0

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

DI water [ l] 22

New Alkaline Process

New batch tool: RENA BatchType TEX HP tool:

Cooperation: Cooperation:
Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers 23

New Alkaline Process

AlkaTex Plus – process data
Eff. % Voc V Isc A FF %

AlkaTex Plus texturing POCl3 emitter diffusion P-glass etching PECVD SiNx-deposition Printing and firing of contacts Laser edge isolation

AlkaTex Plus textured 156 mm mono-Si wafers, labscale Average 17.30 0.619 8.63 77.90

Processed with: GP AlkaTex Plus BASF Isopropanol Selectipur? BASF Potassium Hydroxide 50 % Selectipur?

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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Summary

Survey texture Acid texture InTex plus process

KOH-IPA texture New AlkaTex Plus process

Dr. Michael Michel: New innovative acid and alkaline texturing process for silicon wafers

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