Buried WSi/sub x/ SOI structures

Tungsten silicide is a well know material used widely in the semiconductor industry, particularly for reducing the conductivity of polysilicon layers. A similar concept has been proposed for the reduction of buried layer resistance in bipolar and smart power circuits. This paper examines in detail the stability of a buried CVD WSi/sub x/ SOI structure and discusses the silicon microstructure as a function of temperature and doping of the layer, SIMS analysis of the silicon layer on top of the silicide layer, and etchability of the silicide layer. It is found that the silicide layer is stable to high temperature and remains intact. In addition it is shown that the SOI layer is not contaminated by the silicide layer. Electrical contact between the silicide layer is also established. Finally a trench etch process is presented which can pattern the film in a single step.