Silicon Wafers

Fraunhofer Center for Silicon Photovoltaics CSP

© Fraunhofer CSP

More than 80 per cent of the global solar cell and photovoltaic module production is based on crystalline wafer technology. Further improvement of this technology requires increased cell efficiency as well as the usage of thinner wafers combined with a reduction of wafer and cell breakage rates. Moreover, the most important properties of the wafers such as absorption and lifetime must be positively affected during the production of wafers and solar cells.

The research activities of the »Silicon Wafers« group are focused on:

  • Development and testing of manufacturing technologies for thin silicon wafers or substrates
  • Analysis of technology processes and related consumables
  • Characterizing the mechanical properties of wafers and solar cells, especially in terms of strength and breakage
  • Development and optimization of plasma texturized surfaces having high light absorption and long carrier lifetimes
  • Development of a light-induced passivation of efficiency-limiting defect structures

The Fraunhofer CSP offers a whole process pilot line for wafering (Team Wafering):

  • Cutting ingots (multicrystalline /monocrystalline) into bricks (squaring, cropping and grinding of brick surfaces)
  • Manufacturing of wafers with multi-wire sawing technologies (slurry based processes with straight and structured wire and diamond wire processes)
  • Automatic wafer cleaning
  • Automatic final quality inspection and sorting of wafers on customer request

Additionally, the group works on topics in mechanical and microstructural analysis regarding the wafer and cell manufacturing (Team Mechanics of Wafer and Cells):

  • Microstructural analysis of sawing wires, wafers and solar cells (defects, microstructure, topography, roughness, geometry, etc.)
  • Mechanical experiments to determine - Strength (3-point- or 4-point-bending, ball-ring, ball-on-3-balls, etc.),- Elastic and plastic properties of sawing wire, - Abrasion behavior of silicon during sawing process
  • Finite element simulation for calculation of fracture stresses and stress/load analysis of processes
  • Analysis of breakage mechanisms based on mechanical tests, fractographical methods (identification of failure mechanisms and fracture origins), and/or analytical and numerical simulation models

On this page:

Publications

  • Bagdahn, J.; Gebhardt, S.; Klute, C.; Koepge, R.;Meyer, S.; Schoenfelder, S.; Schwabe, H.; Habermann, D.; Jansen, Ch.; Huber, R.; Scholze, S.; Sen, I.: Sawing and cleaning of silicon wafers for solar cell applications with diamond coated wire and wafer characterization in Proc. of SNEC PV Power Expo -Dialogue & Conference; 2012
  • Kaule, F.; Koepge, R.; Schoenfelder, S.; Damage and breakage of silicon wafers during impact loading on the wafer edge; in Proc. of the 27th European Photovoltaic Solar Energy Conference and Exhibition EU PVSEC 2012; Nowak, S.; Jäger-Waldau, A. (Hrsg.); WIP München (2012) 1179-1184; 482/2013
  • Koitzsch, M.; Lewke, D.; Kaule, F.; Oswald, M.; Schoenfelder, S.; Turek, M.; Büchel, A.; Zühlke, H.-U.; Thermal laser separation – damage-free and kerfless cutting of wafers and solar cells; in Proc. of 6th International Workshop on Crystalline Silicon for Solar Cells CSSC 2012; Institut National de L'Energie Solaire, Le Bourget du Lac, Frankreich (2012) digital; 802/2012
  • Meißner, D.; Hurka, B.; Zeh, J.; Sunder, K.; Koepge, R.; Wagner, T.; Moeller, H.-J.; Schoenfelder, S.; Anspach, O.; Loss of wire tension in the wire web: towards stable cutting conditions for all wafers; in Proc. of 6th International Workshop on Crystalline Silicon Solar Cells, CSSC6; Institut National de L'Energie Solaire, Le Bourget du Lac, Frankreich (2012) digital; 853/2012
  • Oswald, M.; Loewenstein, T.; Schubert, G.; Schoenfelder, S.; Effect of metal-wrap-throigh holes and etching parameters on the strenght of multicrystalline; in Proc. of 6th International Workshop on Crystalline Silicon Solar Cells, CSSC6; Institut National de L'Energie Solaire, Le Bourget du Lac, Frankreich (2012) digital; 823/2012
  • Schoenfelder, S.; Bagdahn, J.; Petzold, M.: Mechanical characterisation and modelling of thin chips in Proc. of 27th European Photovoltaic Solar Energy Conference and Exhibition EU-PVSEC; Frankfurt (2012) 1179 – 1184
  • Schoenfelder, S.; Bagdahn, J.; Ebert, M.; Petzold, M.; Bock, K.; Landesberger, C.: Investigations of strength properties of ultra-thin silicon in Proc. of 6th International Workshop on Crystalline Silicon Solar Cells CSSC; Aix-lex-Bains, Frankreich (2012)
  • Schoenfelder, S.; Breitenstein, O.; Rissland, S.; De Donno, R.; Bagdahn, J.: Glue-cleave: Kerfless wafering for silicon wafers with mMetal on glueing and removable interfacein Proc. Of 22nd Workshop on crystalline silicon cells & modules: material and processes; Sopori, B.; Sinton, R. (Eds.); (2012) 208-214; 652/2012
  • Schoenfelder, S.; Kaule, F.; Oswald, M.; Bagdahn, J.; Petzold, M.: Strength of thin silicon wafers with via holes. in Proc. Of 13th International Workshop Forum be-flexible 2012 Thin Semiconductor Devices; Fraunhofer EMFT (Hrsg.); Fraunhofer EMFT (2012); 837/2012

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  • Bagdahn, J.; Oswald, M.; Schoenfelder, S.; Dietrich, S.; Pander, M.; Sander, M.; Ebert, M.: Crack growth in silicon and influence on reliability of crystalline silicon solar cells and modules in Proc. of 1st International Conference on Silicon Photovoltaics - Silicon PV; (2011)
  • Schoenfelder, S.; Bagdahn, J.; Baumann, S.; Kray, D.; Mayer, K.; Willeke, G.; Becker, M.;Christiansen, S.: Strength characterization of laser diced silicon for application in solar industry in Proc. of 26th European Photovoltaic Solar Energy Conference EU-PVSEC; Hamburg (2011) 2072 – 2077
  • Schoenfelder, S.; Bohne, A.; Bagdahn, J.: Comparison of test methods for strength characterization of thin solar wafer in Proc. of 37th IEEE Photovoltaic Specialists Conference IEEE; Seattle, USA (2011) 1641 - 1646
  • Schoenfelder, S.; Bohne, A.; Bagdahn, J.: Strength characterization and proof testing of thin solar wafer in Ultra-thin Chip Technology and Applications; Springer New York (2011) 195-218
  • Schoenfelder, S.; Oswald, M.; Geppert, T.; Wuetherich, T.; Krokoszinski, H.-J.; Bagdahn, J.: Mechanical strength of metal wrap through wafers in Proc. of 1st International Conference on Silicon Photovoltaics; (2011)
  • Schoenfelder, S.; Oswald, M.; Geppert, T.; Wuetherich, T.; Krokoszinski, H.-J.; Bagdahn, J.: Mechanical strength of metal wrap through wafers in Proc. of 21st Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes; (2011)
  • Schoenfelder, S.; Oswald, M.: Statistical modeling of holes regarding mechanical strength of silicon wafers in Proc. of 5th International Workshop on Crystalline Silicon Solar Cells; (2011)
  • Schoenfelder, S.: Mikrorisse in Siliziumwafern – Entstehung und Vermeidung in Proc. of 8. Workshop »Photovoltaik-Modultechnik«; (2011)
  • Schoenfelder, S.; Bagdahn, J; Oswald, M.; Dietrich, S.; Pander, M.; Sander, M.; Ebert, M.: Crack growth in silicon and influence on reliability of crystalline silicon solar cells and modules in Proc. of Freiberger Silizumtage; (2011)
  • Schoenfelder, S.; Koepge, R.: Strength and damage of wafers in handling processes in Proc. of Workshop »Handling and Automation of Solar Wafer and Cells«; (2011)
  • Oswald, M.; De Donno, R.; Schoenfelder, S.: Modeling of multicrystalline silicon wafers considering microstructural properties in Proc. of 5th International Workshop on Crystalline Silicon Solar Cells; (2011)

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  • Ahrens, B.; Brand, S.;Büchner, T.; Darr, P.; Schoenfelder, S.; Paßlick, C.; Schweizer, S.: Mechanical properties of fluorozirconate-based glass ceramics for medical and photovoltaic applications in Proc. of 17th International Symposium on Non Oxide and New Optical Glasses (ISNOG); (2010)
  • Bohne, A.;Schoenfelder, S.; Bagdahn, J.: The influence of wire sawing process on mono- and multicrystalline silicon wafers in Proc. of 25th European Photovoltaic Solar Energy Conference EU-PVSEC; Valencia, Spanien (2010) 2578 - 2583
  • Ganapati, V.; Schoenfelder, S.; Castellanos, S.; Oener, S.; Buonassisi, T.: Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon in Proc. of 35th IEEE Photovoltaic Specialist Conference; (2010)
  • Ganapati, V.; Schoenfelder, S.; Castellanos, S.; Oener, S.; Buonassisi, T.: Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon in Proc. of E-MRS; (2010)
  • Ganapati, V.; Schoenfelder, S.; Castellanos, S; Oener, S; Koepge, R.; Sampson, A; Marcus, M. A.; Lai, B.; Morhenn, H.; Hahn, G.; Bagdahn, J.; Buonassisi, T.; Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon Journal of Applied Physics 108 (2010) 063528; M 190/2010
  • Schoenfelder, S.: Birefringence and residual stress of microstructural defects in multicrystalline silicon in Proc. of 2nd Symposium on Mechanical Issues in Manufacturing & Application of Solar Cells and Modules; (2010)
  • Schoenfelder, S.: Modeling of mechanical testing in Proc. of SINTEF; (2010)

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  • Ganapati, V.; Castellanos, S.; Schoenfelder, S.; Oener, S.; Buonassisi, T.: Stress analysis of bulk microdefects in multicrystalline silicon solar cells wafers using infrared birefringence imaging in Proc. of Material Research Society Fall Meeting; (2009)
  • Schoenfelder, S.; Bohne, A.; Bagdahn, J.: Comparison of test methods for strength characterization of thin solar wafer in Proc. of 24th European Photovoltaic Solar Energy Conference EU-PVSEC; Hamburg (2009) 977 - 980
  • Schoenfelder, S.; Bagdahn, J.: Characterizing strength of thin silicon samples in Proc. of Material Research Society Fall Meeting; (2009)

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  • Schoenfelder, S.; Sampson, A.; Ganapati, V.; Koepge, R.; Bagdahn, J.; Buonassisi, T.: Quantiative stress measurements of bulk microdefects in multicrystalline silicon in Proc. of 23rd European Photovoltaic Solar Energy Conference EU-PVSEC; Valencia, Spanien (2008) 1780 - 1784
  • Schoenfelder, S.; Oswald, M.; Fischer, C.; Zuehlke, H.-U.; Berbig, C.; Geppert, T.; Wuetherich, T.; Krokoszinski, H.-J.; Bagdahn, J.: Investigations of laser and design parameters of via holes on mechanical strength of metal wrap through solar cells in Electronic Components and Technology Conference ECTC; Lake Buena Vista, USA (2008) 1525–1531
  • Theuss, H.; Koller, A.; Kröninger, W.; Schoenfelder, S.; Petzold, M.: Assessment of a lasersingulation process for si-wafers with metallized back side and small die size in Proc. of 18th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes NREL; Vail, USA (2008) 187-190

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