Method of selectively diffusing aluminium into a silicon semiconductor substrate

摘要

A method of diffusing selectively aluminium into a single crystal silicon semiconductor substrate for fabricating a semiconductor device comprises the steps of forming a diffusion source layer of aluminium having a predetermined thickness on at least one of the major surfaces of the substrate in a predetermined pattern, forming an oxide film of a predetermined thickness through oxidation over the surface of the diffusion source layer and the exposed surface of the substrate, and heating the substrate inclusive of the exposed surface thereof and the diffusion source layer thereby to diffuse aluminium into the substrate. The thickness of the oxide film is so selected as to suppress vaporization of the aluminium and at the same time to be used as a diffusion mask without giving rise to crystallization into a cristobalite structure. The method allows the pattern of boundary between the diffused regions and non-diffused regions as well as concentration profile of the diffused region to be controlled in a desired manner with a high accuracy.