Fracture Analysis and Distribution of Surface Cracks in Multicrystalline Silicon Wafers

Solar silicon wafers are mainly produced through multiwire sawing. The sawing process induces micro cracks on the wafer surface, which are responsible for brittle fracture. Hence, it is important to scrutinize the crack geometries most commonly generated in silicon wafer sawing or handling process and link the surface crack to the fracture of wafers. The fracture of a large number of multicrystalline silicon wafers has been investigated by means of 4-point bending and twisting tests and a failure probability function is presented. By neglecting the material property variation and assuming that one surface crack is dominating the wafer breakage, 3D finite element models with various crack sizes (depth, length, and orientation) have been analyzed to identify the distribution of surface crack geometries by fitting the failure probability from the experiments. With respect to the 63% probability, the existing surface cracks in the wafers studied appear to have depth and length ratios less than 0.042 and 0.19, respectively. Furthermore, it has been shown that the surface cracks with depth in the range from 10 to 20 μm, length up to 10 mm and angles in the range of 30 deg–60 deg, can be considered as the most common crack geometries in wafers we tested. Finally, it has been found that the mechanical strength of the wafers tested parallel to the sawing direction is approximately 15 MPa smaller than those tested perpendicular to the sawing direction.

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Analysis of Handling Stresses in Thin Solar Silicon Wafers Generated by a Rigid Vacuum Gripper

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4030763 ◽

2015 ◽

Vol 138 (3) ◽

Cited By ~ 2

Author(s):

Hao Wu ◽

Shreyes N. Melkote

Keyword(s):

Stress Distribution ◽

Dominant Role ◽

High Stress ◽

Surface Profile ◽

Silicon Wafers ◽

Wafer Surface ◽

Initial Surface ◽

Fe Modeling ◽

Solar Silicon ◽

Surface Profiles

Breakage of thin solar silicon wafers during handling and transport depends on the stresses imposed on the wafer by the handling/transport device. In this paper, the stresses generated in solar silicon wafers by a rigid vacuum gripper are analyzed via a combination of experiments and numerical modeling. Specifically, stresses produced in monocrystalline (Cz) and multicrystalline (Cast) silicon wafers of different thicknesses when handled by a vacuum gripper are analyzed using the finite element (FE) method. With the measured surface profiles of the wafer and the gripper as input, the handling process is simulated using FE modeling and the stress distribution obtained. The FE modeling results are validated by experimental data of wafer surface profile during handling. The results show that while the vacuum level does not have significant impact on the stress distribution, the initial surface profiles of the thin wafer and gripper play a dominant role in producing regions of high stress in the wafer.

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Modeling the Tensile Strength and Crack Length of Wire-Sawn Silicon Wafers

Journal of Solar Energy Engineering ◽

10.1115/1.3028048 ◽

2009 ◽

Vol 131 (1) ◽

Cited By ~ 13

Author(s):

Claudia Funke ◽

Susann Wolf ◽

Dietrich Stoyan

Keyword(s):

Stress Distribution ◽

Crack Length ◽

Fracture Stress ◽

Quantitative Description ◽

Silicon Wafers ◽

Wafer Surface ◽

Truncation Parameter ◽

Solar Silicon ◽

Intensity Functions ◽

The Impact

Solar silicon wafers are mainly produced through multiwire-sawing. This sawing implies microcracks on the wafer surface, which are responsible for brittle fracture. In order to reduce the sawing-induced cracks, the wafers are damage etched after sawing. This paper develops a model for the impact of crack length manipulation on fracture stress distribution. It investigates the effect of damage-etching on the mechanical properties of solar silicon wafers. The main idea is to transform the fracture stress distribution into a crack length intensity function and to model the effect of etching in terms of crack lengths. The fracture stress distribution is determined statistically by fracture tests of wire-sawn and sawn and etched wafers. The Griffith criterion then enables the transition to crack lengths and crack length intensity functions. Two numerical parameters, called truncation parameter and scaling parameter, determine this relationship and enable a quantitative description of the effect of etching. They turn out to be dependent on etchant and geometry of load and thus tested crack population.

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Strength of Multicrystalline Silicon Wafers for Various Surface Conditions

MRS Proceedings ◽

10.1557/proc-1210-q05-07 ◽

2009 ◽

Vol 1210 ◽

Author(s):

Przemyslaw Rupnowski ◽

Bhushan Sopori ◽

Dan Armentrout ◽

Ethan Good

Keyword(s):

Solar Cells ◽

Surface Treatment ◽

Silicon Wafers ◽

Multicrystalline Silicon ◽

Wafer Surface ◽

Fracture Properties ◽

Surface Conditions ◽

Loading Fixture

AbstractThis study focuses on fracture properties of silicon wafers used by the photovoltaic (PV) industry as substrates for solar cells. In the first part, we numerically model three fixtures that are often used to test the strength of PV wafers. In the second part, we employ our previously developed model to predict strength of the wafers as a function of loading fixture and surface treatment. Surface treatment is simulated by removing damage from the wafer surface.

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Micro Electrical Discharge Machining Thermal Effect on Micro-Cracks Generation on Silicon Material

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1047.41 ◽

2021 ◽

Vol 1047 ◽

pp. 41-49

Author(s):

Xiao Zhong Song

Keyword(s):

Electrical Discharge Machining ◽

Crystalline Silicon ◽

Local Area ◽

Silicon Wafers ◽

Adverse Side Effect ◽

Micro Edm ◽

Crystalline Orientation ◽

Surface Machining ◽

Crack Generation ◽

Micro Cracks

Various novel 3D micro machining technologies were researched and developed for silicon micro mechanical system fabrication. Micro EDM is one of them. The material removal mechanism is thermal sparking erosion and is completely independent with regards to the crystalline orientation of silicon, therefore there is no orientation constraint in processing the complex 3D geometry of silicon wafers. As thermal sparking implied, the process features local area high temperature melting and evaporating, and this characteristic has an adverse side-effect on the sparked surface integrity. One important concern is the generation of micro cracks, which would provide an adverse effect on the fatigue life of the micro feature element made of silicon. For this consideration, in this paper, with the experiment and SEM picture analysis approach, the author explored the micro crack generation characteristics on mono crystalline silicon wafers under micro EDM with available sparking energies and on the different crystal orientation surface machining. The generation of micro cracking is not only related with the sparking energy but also related with the crystalline orientation. The {100} orientation is the strongest surface to resist crack generation. For a strong-doped P type silicon wafer, there exists a maximum crack energy threshold. If single sparking energy is over this threshold, micro cracks unavoidably would be generated on any orientation surface. Two types of chemical etching post processes that can remove cracks on sparked surfaces are also tested and discussed.

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Enhanced performance in the deteriorated area of multicrystalline silicon wafers by internal gettering

Progress in Photovoltaics Research and Applications ◽

10.1002/pip.2391 ◽

2013 ◽

Vol 23 (1) ◽

pp. 30-36 ◽

Cited By ~ 5

Author(s):

Yacine Boulfrad ◽

Antti Haarahiltunen ◽

Hele Savin ◽

Eivind J. Øvrelid ◽

Lars Arnberg

Keyword(s):

Silicon Wafers ◽

Multicrystalline Silicon

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About the relevance of defect features in as-cut multicrystalline silicon wafers on solar cell performance

10.1063/1.5049330 ◽

2018 ◽

Cited By ~ 2

Author(s):

Aditya Kovvali ◽

Matthias Demant ◽

Theresa Trötschler ◽

Jonas Haunschild ◽

Stefan Rein

Keyword(s):

Solar Cell ◽

Silicon Wafers ◽

Cell Performance ◽

Multicrystalline Silicon ◽

Solar Cell Performance

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INFRARED LBIC SCAN MAPS APPLIED TO ALUMINIUM GETTERED MULTICRYSTALLINE SILICON WAFERS

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:1991637 ◽

1991 ◽

Vol 01 (C6) ◽

pp. C6-237-C6-238 ◽

Cited By ~ 1

Author(s):

J. Y. NATOLI ◽

M. PASQUINELLI ◽

F. FLORET ◽

S. MARTINUZZI

Keyword(s):

Silicon Wafers ◽

Multicrystalline Silicon

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Texturisation of multicrystalline silicon wafers for solar cells by reactive ion etching through colloidal masks

Solar Energy Materials and Solar Cells ◽

10.1016/s0927-0248(02)00214-3 ◽

2003 ◽

Vol 76 (2) ◽

pp. 155-166 ◽

Cited By ~ 52

Author(s):

W.A. Nositschka ◽

C. Beneking ◽

O. Voigt ◽

H. Kurz

Keyword(s):

Solar Cells ◽

Reactive Ion Etching ◽

Silicon Wafers ◽

Multicrystalline Silicon ◽

Ion Etching

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Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 7th International Pipeline Conference, Volume 3 ◽

10.1115/ipc2008-64658 ◽

2008 ◽

Author(s):

Gery Wilkowski ◽

David Rudland ◽

Do-Jun Shim ◽

David Horsley

Keyword(s):

Transition Temperature ◽

Surface Crack ◽

Master Curve ◽

Crack Depth ◽

Temperature Shift ◽

Transition Temperatures ◽

Surface Cracks ◽

Line Pipe ◽

Brittle To Ductile Transition ◽

Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

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