Forming silicon@ wafers by spin-casting on rotating table - by forming melt of polycrystalline silicon@ granules and recrystallising using embedded seed-crystal

摘要

A melt container (12), pref. made of quartz and formed in a U-shape, filled with molten Si (17) above which a container (11) for granular polycrystallne Si (14) is placed to replenish the melt. The melt container is heated (13) to form the melt (17) and maintain its temp. (19) near the opening (25), from which it is poured to form Si wafers. The exit opening (25) is pref at the opposite end of the container from the filler opening (11). The granules container (11) is pref. a drum, pref. made of quartz, which can be rotated and contains a slit opening (15) through which it can be filled and emptied when the drum is in an appropriate position. A friction-less coating is used between the drum and the filler-opening of the melt container to provide a hermetic seal and allow easy rotation of the drum. A gas-inlet opening (24) allows an inert gas ambient to be used to force the melt out of the opening (25) to pour the wafers. The process consists of forming a melt, which is held inside the container by the pressure of the ambient gas, and pouring it onto a spinning plate (30). A method for recrystallisation is also claimed. USE/ADVANTAGE - Faster formation of single crystalline Si wafers compared with the conventional Czochralski crystal bar pulling. Avoids lengthy wafer-cutting process currently used. The method allows very much purer polycrystalline Si to be used and causes much less contamination since it is used quickly as it is poured into the melt container. The recrsytallistion has been modified to minimise contamination of the wafers. Avoidance of wafer sawing also reduces Si waste.