Fabrication of insulated gate gallium arsenide fet with self-aligned

Abstract

Disclosed is a process for forming a high-speed, self-aligned GaAs-gate field effect transistor with submicron channel length. Starting with a semi-insulating GaAs substrate having a thin gate insulator layer of undoped AlGaAs and a comparatively thick highly doped GaAs layer, a metal contacting the doped GaAs layer is controllably formed by sidewall image transfer and planarization etchback technique. The thickness and width of the metal strip are in the low submicron range. Using the metal strip as a mask, the doped GaAs is patterned into a GaAs gate for the FET having the characteristics of submicron width (i.e., the dimension of the gate measured along the source-drain), substantially vertical walls and contacted on the top thereof in a self-aligned relationship by the metal strip. Next, a submicron wide insulator sidewall is formed on the vertical walls of the gate. By ion implanation across the AlGaAs layer using the gate structure and a patterned photoresist as a mask, source and drain are formed in the substrate in self-aligned relation with the gate. Contact metallization is formed to electrically contact the source, drain and the gate.