Controlling diffusion profiles in spaced junction device - esp thyristor by oxide growth and out diffusion

摘要

A number of spaced p-n junctions is formed in a mono-crystalline Si wafer by (a) forming a diffusion mask having at least one window on the outer surface of the wafer, (b) loading the wafer into a diffusion furnace with a measured mass of III-V intermetallic cpd. and a measured mass of gp. III or V metal and (c) heating to a diffusion temp. and forming, in a single diffusion cycle, a p-type region beneath the mask and an n-type region beneath the window, with the p-n junction extending to and terminating at the outer surface of the wafer, the impurity concn. of both the III and V impurities is varied within the wafer by (d) stripping and redepositing an oxide coating over the entire wafer and (e) heating to cause the concn. variation. A desired diffusion profile and undamaged surface are provided.