Melt dumping in string stabilized ribbon growth
OwnerEmanuel M. Sachsinventor
Life of this patent
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Abstract
A method and apparatus for stabilizing the edge positions of a ribbon drawn from a melt includes the use of wettable strings drawn in parallel up through the melt surface, the ribbon being grown between the strings. A furnace and various features of the crucible used therein permit continuous automatic growth of flat ribbons without close temperature control or the need for visual inspection.
Claims8
In a process in which a ribbon of crystal is grown from a body of melt at a growth interface, with string stabilization being employed at the edges of said ribbon, a method for minimizing the introduction of impurities from said melt to said crystal grown therefrom comprising:
- reducing build-up of impurities in the body of the melt due to impurity segregation at the growth interface during crystal growth by continually replenishing the melt with new raw material, and dumping and completely removing a fraction of molten material from said body of melt continually during the crystal growth process, said fraction being removed at a rate less than the rate of addition of new raw material such that the concentration of impurities in said body of melt and therefore in the growth crystal is reduced during crystal growth, in an open loop process.
A method for minimizing the introduction of impurities into a ribbon of crystalline material formed, with the aid of strings to stabilize the edges of said ribbon, in a crystal-growing process from a melt at a growth interface located at the melt surface, comprising the following steps:
- maintaining a flow of melt in the vicinity of the growth interface, to disperse and remove from the growth interface impurities left at said interface during said crystal growing process;
- dumping and discarding impurity-containing melt material continually from the body of said melt;
- and
- continually replenishing with fresh melt material the melt material removed from the body of the melt by said dumping step and by said crystal growing process;
- said dumping and replenishing steps serving to continually reduce the concentration of impurities in said melt, reducing impurity build-up in the melt as a result of impurity segregation during crystal growth.
Dependencies are inferred from the claim text.