Plasma Etching of Composite Silicide Gate Electrodes

To obtain the advantages of refractory metal silicide composite structures ( i.e. , silicide/polysilicon/gate oxide) for VLSI applications, these structures have to be defined with little impact on ground rules or subsequent wafer processing. This paper studies film definition using both parallel plate and barrel plasma reactors. The parallel plate system meets all criteria. Etch rates for polysilicon, WSi 2 , and SiO 2 were studied using CF 4 / O 2 plasmas. The edge profile of the defined composite structure is dependent on the etch rate ratios of the constituent layers, and these results agree with the classical model for isotropic etching. A process is defined with acceptable edge profiles. Operational IGFET devices with 1–2 μm dimensions have been produced.