The role of fluorine-containing ultra-thin layer in controlling boron thermal diffusion into silicon

Abstract

We have investigated the influence of silicon dioxide reactive ion etching (RIE) parameters on the composition of the polymer layer that is formed during this process on top of the etched layer, and finally, the role of this layer in high- temperature thermal diffusion of boron into silicon. The polymeric layer formed on the etched surface appeared to consist of fluorine and silicon fluoride (SiOF and SiF). Concentration of these components changes depending on the parameters of RIE process, i.e., rf power, gas pressure and etching time. The composition of this polymeric layer affects, in turn, boron thermal diffusion into silicon. With increasing rf power, the depth of boron junction is increased, while increasing time of etching process reduces boron diffusion into silicon.

Keywords

• fluorine
• reactive ion etching
• silicon fluoride
• boron thermal diffusion
• fluorocarbon plasma