Abstract:
Interposer sheet for making silicon solar semiconductor bodies. Interposer is free-standing, thin, flexible, porous and withstands chemical/thermal environment of molten semiconductor without degradation. Interposer is of ceramic material, such as silica, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbide, silicon carbonitride, silicon oxycarbonitride and others. Provided between a forming surface of a mold sheet, and the molten material from which a semiconductor body will be formed. Secured to the forming surface or deposited upon the melt. Interposer suppresses grain nucleation, and limits heat flow from the melt, promotes separation of the semiconductor body from the forming surface, prefabricated before use. Because free-standing and not adhered to the forming surface, problems of mismatch of CTE are minimized. Interposer and semiconductor body are free to expand and contract relatively independently of the forming surface.
Abstract:
A pressure differential is applied across a mold sheet and a semiconductor (e.g. silicon) wafer is formed thereon. Relaxation of the pressure differential allows release of the wafer. The mold sheet may be cooler than the melt. Heat is extracted almost exclusively through the thickness of the forming wafer. The liquid and solid interface is substantially parallel to the mold sheet. The temperature of the solidifying body is substantially uniform across its width, resulting in low stresses and dislocation density and higher crystallographic quality. The mold sheet must allow flow of gas through it. The melt can be introduced to the sheet by: full area contact with the top of a melt; traversing a partial area contact of melt with the mold sheet, whether horizontal or vertical, or in between; and by dipping the mold into a melt. The grain size can be controlled by many means.