Method for making silicon rods

Claim 1

A method for making silicon rods having a columnar structure made of monocrystalline crystal zones having a preferential crystallographic orientation, comprising the steps of: feeding silicon from a silicon reservoir into a crystallization chamber having an interior horizontal dimension corresponding to at least to the cross-sectional dimension of the rod to be made and having a vertically movable support base on which said silicon fed to said chamber rests; providing an intermediate protective melt between the silicon and the inner wall of said crystallization chamber so as to avoid direct contact therebetween, said protective melt being made of alkaline earth fluorides in an admixture with 30 to 90 mole percent alkaline earth silicates, said protective melt having a melting point below the melting point of silicon; and effecting the solidification of said silicon in said crystallization chamber by subjecting the same to a vertical temperature gradient which produces an oriented crystal growth in the solidifying silicon, said silicon being fed to said chamber in such a quantity that a molten deposit is maintained above the solidifying silicon during its crystal growth under the influence of said temperature gradient, the weight quantity of said molten deposit being maintained at 0.1 to 5 times that of the silicon which crystallizes in a downward direction per minute.

Claim 2

A method for making silicon rods having a columnar structure made of monocrystalline crystal zones having a preferential crystallographic orientation, comprising the steps of: feeding silicon from a silicon reservoir into a crystallization chamber having an interior horizontal dimension corresponding to at least to the cross-sectional dimension of the rod to be made and having a vertically movable support base on which said silicon fed to said chamber rests; providing an intermediate protective melt between the silicon and the inner wall of said crystallization chamber so as to avoid direct contact therebetween, said protective melt being made of alkaline earth fluorides in an admixture with 30 to 90 mole percent alkaline earth silicates, said protective melt having a melting point below the melting point of silicon; and effecting the solidification of said silicon in said crystallization chamber by subjecting the same to a vertical temperature gradient which produces an oriented crystal growth in the solidifying silicon, said silicon being fed to said chamber in such a quantity that a molten deposit is maintained above the solidifying silicon during its crystal growth under the influence of said temperature gradient, the weight quantity of said molten deposit being maintained at 0.1 to 5 times that of the silicon which crystallizes in a downward direction per minute.