Profile Controlled Etching for Mo/WSix Double Layers

Reactive ion etching for Mo/WSi x ( x 0.6) double layers has been investigated to fabricate a T-shaped gate electrode for self-aligned GaAs MESFETs. CF 4 +O 2 , SF 6 +O 2 , and SF 6 +H 2 gas mixtures are used as etching gases. The etch rates for Mo and WSi x layers are measured as functions of the partial pressures of O 2 and H 2 gases. A highly anisotropic etching of WSi x layer and high etch rate selectivity of WSi x to Mo are found for the SF 6 +O 2 mixture and the SF 6 +H 2 mixture, respectively. A T-shaped Mo/WSi x gate electrode is obtained by combining these two etching methods.