| 摘要 |
PURPOSE:To diffuse impurities in one side of a semiconductor wafer without using wax, etc., by a method wherein insulating films being of different thickness are provided on both the faces of the semiconductor wafer, and an opening is formed selectively in the insulating film on the thin film side. CONSTITUTION:The oxide films 19, 20 having thickness t1, t2 are provided on the surace and on the back of the Si wafer 1, and thickness thereof is made as t2 1.5-2t1. A resist mask 21 is applied thereon, and when the film 19 is etched, the film 20 is left as t3=t2-t1. When the impurities are diffused from the opening 23 next, external diffusion of impurities from the back of the wafer 1 is not generated, and favorable selection can be attained. To form the oxide films 19, 20, when the wafers are to be accomodated in a core tube 24, pure water 30 is applied only the back of the wafer 1, and they are heated to oxidize. Water 30 is evaporated, many O2 are generated only on the back, the oxide film is made to grow rapidly on the back, and thickness thereof becomes as 1.5-2 times of thickness of the oxide film on the surface. |
