Oxidation of tantalum disilicide on polycrystalline silicon

Publisher Website
Google Scholar
Abstract
Oxidationcharacteristics of the tantalum disilicide films have been investigated in the temperature range of 900°–1050 °C in dry oxygen and steam ambients. The silicide does not oxidize in dry oxygen and oxidizes in steam at a rate lower than that of dopedpolycrystallinesiliconfilms as long as there is a polycrystallinesilicon layer between the silicide and the gate oxide. Under these circumstances, the silicide retains its electrical and mechanical characteristics. The oxide on the silicide has an etch rate (in buffered hydrofluoric acid) similar to that of thermal SiO2 on silicon. Electrical characteristics of the oxide appear to be similar to those of the wet oxide on polycrystallinesilicon. In the absence of polycrystallinesilicon, between the silicide and the gate oxide, oxidation leads to a loss in the conductivity of the silicide and eventually to a mechanical instability of the film. An oxidation mechanism, which assumes silicon diffusion by substitution through the silicide, has been proposed.