Plasma Etching of Refractory Gates for VLSI (Very Large Scale Integration) Applications.

摘要

The present status of plasma etching of refractory gates is reviewed in the context of high resolution patterning. Etching of various refractory metals (cf. Mo, W) and metal silicides (cf. MoSi2, WSi2, TaSi2) is particularly emphasized and discussed in terms of etch rate, anisotropy, etch selectivity over SiO2 resist, and other thin film materials. Key issues addressed include choice of etchant (cf. CF4, NF3, CCl4) additive gas (O2, Ar, He), and reactor configuration (planar plasma, RIE, flexible diode, triode). Factors influencing the control of edge profiles and single-level and composite gate structures are described. End-point detection of these plasma processes is reviewed and compared with that developed for silicon etching. Also, basic mechanisms in these processes, such as desorption of reaction products, are discussed with respect to their effect on the etching characteristics of these refractory materials.