| 摘要 |
A method of forming a thermally stable tungsten silicide layer. The method includes sequentially forming a polysilicon layer and a tungsten silicide layer over a semiconductor substrate. Then, the semiconductor substrate is exposed to nitrogen (N2) plasma at room temperature so that a nitridation reaction can be initiated, thereby forming a thin tungsten nitride layer over the tungsten silicide layer. Thereafter, a silicon nitride layer is formed over the tungsten nitride layer. Since the thermal stability of a tungsten nitride layer is higher, the probability of re-crystallization in the tungsten silicide layer when the silicon nitride layer is subsequently deposited is reduced. Moreover, tungsten nitride is able to fill the voids and crevices at the grain boundaries of the tungsten silicide layer after the tungsten silicide layer is re-crystallized. Finally, photolithographic and etching operations are carried out to form a gate structure over the semiconductor substrate.
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