Method for producing large surface plate or disc-shaped Si crystals with columnar structure

Claim 1

In a method of producing a relatively large surface silicon crystal plate-shaped body having a columnar crystalline structure and which is useful for manufacture of solar cells, said body being produced through a directional solidification of molten silicon in a silicon melting tank, the improvement comprising: arranging a cooling gas system comprised of a controllable cooling gas source interconnected with a plurality of gas nozzles in working relation with said silicon melting tank; positioning said gas nozzles a relatively short distance above a silicon melt surface in said melting tank and arranging said nozzles relative to one another so that spacing between one nozzle center and an adjacent nozzle center corresponds to the diameter of crystallites forming the desired columnar structure; directing a plurality of cooling gas streams from said cooling gas source through said nozzles and onto the silicon melt surface below such nozzles for a period of time sufficient to attain a desired thickness for said silicon body whereby a substantial spontaneous seed crystal formation occurs in the melt surface in the region thereof lying directly opposite such streams and the area of the melt surface below such streams solidifies about such seed crystals to form columnar crystallite structure; and removing the thus-formed silicon body from said melt surface.