Making semiconductor bodies from molten material using a free-standing interposer sheet

Abstract

An interposer sheet can be used for making semiconductor bodies, such as of silicon, such as for solar cell use. It is free-standing, very thin, flexible, porous and able to withstand the chemical and thermal environment of molten semiconductor without degradation. It is typically of a ceramic material, such as silica, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbide, silicon carbonitride, silicon oxycarbonitride and others. It is provided between a forming surface of a mold sheet, and the molten material from which a semiconductor body will be formed. It may be secured to the forming surface or deposited upon the melt. The interposer sheet suppresses grain nucleation, and limits heat flow from the melt. It promotes separation of the semiconductor body from the forming surface. It can be fabricated before its use. Because free-standing and not adhered to the forming surface, problems of mismatch of CTE are minimized. The interposer sheet and semiconductor body are free to expand and contract relatively independently of the forming surface.