Impurity doping method with diffusion source of boron-silicide film

Abstract

A solid phase diffusion process using boron silicide film as diffusion source to improve controllability of diffusion of boron impurity into a silicon substrate in order to achieve a shallow junction. The process includes: cleaning the surface of a Si substrate by removing the native oxide film thereof to expose an active surface; treating the active surface to form thereon a boron silicide film as an impurity source; and introducing boron impurity from the boron silicide film into the Si substrate to form a boron diffusion layer. In this manner, a boron diffusion layer having a high surface concentration and a shallow junction can be formed because the boron silicide film is formed directly on the surface of the Si substrate. Because the boron silicide film is chemically and physically stable, an improved diffusion controllability is obtained. The diffusion controllability is further improved by accurately evaluating the impurity film optically during the fabrication process. A structure composed of a boron diffusion layer and a boron silicide region provides a high speed, highly integrated, and highly reliable semiconductor device, particularly when the boron silicide region is disposed between an impurity region and an electrode metal.