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Title: Wafer screening device and methods for wafer screening

Abstract

Wafer breakage is a serious problem in the photovoltaic industry because a large fraction of wafers (between 5 and 10%) break during solar cell/module fabrication. The major cause of this excessive wafer breakage is that these wafers have residual microcracks--microcracks that were not completely etched. Additional propensity for breakage is caused by texture etching and incomplete edge grinding. To eliminate the cost of processing the wafers that break, it is best to remove them prior to cell fabrication. Some attempts have been made to develop optical techniques to detect microcracks. Unfortunately, it is very difficult to detect microcracks that are embedded within the roughness/texture of the wafers. Furthermore, even if such detection is successful, it is not straightforward to relate them to wafer breakage. We believe that the best way to isolate the wafers with fatal microcracks is to apply a stress to wafers--a stress that mimics the highest stress during cell/module processing. If a wafer survives this stress, it has a high probability of surviving without breakage during cell/module fabrication. Based on this, we have developed a high throughput, noncontact method for applying a predetermined stress to a wafer. The wafers are carried on a belt through a chambermore » that illuminates the wafer with an intense light of a predetermined intensity distribution that can be varied by changing the power to the light source. As the wafers move under the light source, each wafer undergoes a dynamic temperature profile that produces a preset elastic stress. If this stress exceeds the wafer strength, the wafer will break. The broken wafers are separated early, eliminating cost of processing into cell/module. We will describe details of the system and show comparison of breakage statistics with the breakage on a production line.« less

Inventors:
;
Issue Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1143680
Patent Number(s):
8,780,343
Application Number:
13/146,111
Assignee:
Alliance for Sustainable Energy, LLC (Golden, CO)
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY

Citation Formats

Sopori, Bhushan, and Rupnowski, Przemyslaw. Wafer screening device and methods for wafer screening. United States: N. p., 2014. Web.
Sopori, Bhushan, & Rupnowski, Przemyslaw. Wafer screening device and methods for wafer screening. United States.
Sopori, Bhushan, and Rupnowski, Przemyslaw. Tue . "Wafer screening device and methods for wafer screening". United States. https://www.osti.gov/servlets/purl/1143680.
@article{osti_1143680,
title = {Wafer screening device and methods for wafer screening},
author = {Sopori, Bhushan and Rupnowski, Przemyslaw},
abstractNote = {Wafer breakage is a serious problem in the photovoltaic industry because a large fraction of wafers (between 5 and 10%) break during solar cell/module fabrication. The major cause of this excessive wafer breakage is that these wafers have residual microcracks--microcracks that were not completely etched. Additional propensity for breakage is caused by texture etching and incomplete edge grinding. To eliminate the cost of processing the wafers that break, it is best to remove them prior to cell fabrication. Some attempts have been made to develop optical techniques to detect microcracks. Unfortunately, it is very difficult to detect microcracks that are embedded within the roughness/texture of the wafers. Furthermore, even if such detection is successful, it is not straightforward to relate them to wafer breakage. We believe that the best way to isolate the wafers with fatal microcracks is to apply a stress to wafers--a stress that mimics the highest stress during cell/module processing. If a wafer survives this stress, it has a high probability of surviving without breakage during cell/module fabrication. Based on this, we have developed a high throughput, noncontact method for applying a predetermined stress to a wafer. The wafers are carried on a belt through a chamber that illuminates the wafer with an intense light of a predetermined intensity distribution that can be varied by changing the power to the light source. As the wafers move under the light source, each wafer undergoes a dynamic temperature profile that produces a preset elastic stress. If this stress exceeds the wafer strength, the wafer will break. The broken wafers are separated early, eliminating cost of processing into cell/module. We will describe details of the system and show comparison of breakage statistics with the breakage on a production line.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2014},
month = {7}
}

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Works referenced in this record:

Graphic script provides quick classification of GaAs wafers
journal, March 2000


Non-destructive optical methods for assessing defects in production of Si or SiGe materials
journal, July 2004

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