Process for the preparation of polycrystalline silicon ingot

Details Process for the preparation of polycrystalline silicon ingot Process for the preparation of polycrystalline silicon ingot

1993-01-12

1995-07-11

Derrington, James

Plastic and nonmetallic article shaping or treating: processes

Utilizing special inert gaseous atmosphere or flushing mold...

264 25, 264338, B29C 3356

Patent

active

054318696

ABSTRACT:
This invention relates to a process for the preparation of polycrystalline silicon ingots by providing a first layer of coating on the inside walls of a mold with a slurry of silicon nitride powder in an organic binder dissolved in a solvent; charging the said coated mold with silicon pieces along with calcium chloride or/and calcium fluoride; heating the mold to a temperature in the range of 1420.degree.-1500.degree. C. so as to melt the silicon, by keeping the mold inside the furnace; bringing down the temperature of the mold to a temperature 5.degree.-10.degree. C. above the melting point of silicon; withdrawing the mold containing the melt downwardly and slowly from the hot zone of the furnace so that the solidification of the melt starts from the bottom of the mold and proceeds towards the top as the withdrawal continues till all the melt solidifies; cooling the mold to the room temperature under inert atmosphere and removing the polycrystalline silicon ingot from the mold.

REFERENCES:
patent: 4243471 (1981-01-01), Ciszek et al.
patent: 4264052 (1981-04-01), Radtke
Article entitled "Growth of Silicon Ingots by Hem For Photovoltaic Applications" by C. P. Khattak and F. Schmid, pp. 153 to 183, Silicon Processing For Photovoltaics II, Elsevier Science Publishers B.V., 1987.
Article entitled "Polycrystalline Silicon For Solar Cell By The Technique of Directional Solidification" by A. Z. Lin, et al. of General Research Institute of Non-Ferrous Metals, Bejing, China, pp. 1375-1380.
Article entitled "A Reusable Mold in Directional Solidification For Silicon Solar Cells" by Takeshi Saito, et al. of Microelectronics Research Lab. NEC Corporation, Japan, pp. 337 to 345.
Article entitled "Directionally Solidified Solar-Grade Silicon Using Carbon Crucibles" by T. F. Ciszek, et al., Journal of Crystal Growth 46 (1979) pp. 527-533.
Article entitled "Selection of A Crucible Material In Contact With Molten Silicon" by G. Revel, et al. Proceedings of 5th EC Photovoltaic Solar Energy Conference (1983) pp. 1037-1042.
Article entitled "Liquid Encapsulated Bridgman (LEB) Method for Directional Solidification of Silicon Using Calcium Chloride" by P. S. Ravishankar, Journal of Crystal Growth 94 (1989) pp. 62-68.
Article entitled "Molding and Directional Solidification of Solar-Grade Silicon Using An Insulating Molten Salt" by O. Minster J. Granier et al. Journal of Crystal Growth 82 (1987) pp. 155-161.
"Progress in Ingot and Foil Casting of Silicon", D. Helmreich & E. Sirtl, Journal of Crystal Growth, vol. 79 (1986), pp. 562-571.
"Silicon Processing for Photovoltaic", vol. 2, edited by C. P. Khattak and K. V. Ravi (Elsevier Science Publ. Ltd., B.V. 1987), p. 153.
Article entitled "Advances in Solid State Physics" by B. Authier, pp. pp. 1-17 from Lectures of the German Physical Society, Freudenstadt.

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