MANUFACTURE OF SOI SUBSTRATE

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a SOI substrate by which no hollow or the like is produced in a buried oxide film when the SOI substrate is treated by heat in a reducing atmosphere. SOLUTION: A first semiconductor substrate contains impurities of desired conductivity type at a first impurity density. Another semiconductor layer thicker than 0.5μand containing impurities of desired conductivity type at a second impurities density higher than the first impurity density is formed on one surface of the first semiconductor substrate. The surface of the semiconductor layer of the first semiconductor substrate is joined to a second semiconductor substrate covered with an insulating film. The first semiconductor substrate is made into a thin film from the side having no semiconductor layer to expose the semiconductor layer. The substrate adhering to the semiconductor layer is heated in a reducing atmosphere to reduce the density of the impurities in the semiconductor layer. The semiconductor layer is further made into a thin film to finish a SOI layer of a desired thickness.