Effects of dopants and excess silicon on the oxidation of TaSi2/polycrystalline silicon structures

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Abstract
The oxidation rates of tantalum disilicide/polycrystalline silicon (polysilicon) structures have been studied as a function of dopants in the polysilicon and as a function of excess silicon in the silicide. Our results indicate that the oxidation rate is significantly affected: B in the polysilicon enhances the oxidation while As retards the rate. P doping by ion implantation showed little effect, but doping by PBr3 diffusion retarded the oxidation. Excess silicon in the silicide retards the oxidation. These phenomena can be explained by a mechanism in which the kinetics is controlled by the silicon out‐diffusion through the silicide. Analogous to crystalline silicon, the oxidation rate can be enhanced by high concentration of dopants which create point defects that aid the silicon diffusion. The situation is complicated by the presence of grain boundaries. In the case of As and excess silicon, diffusion may be hindered by dopants segregated to the grain boundary, resulting in slower oxidation.

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