High speed gaas mesfet having refractory contacts and a self-aligned

Abstract

Disclosed is a process fo fabrication of a MESFET in which starting with a GaAs substrate having a shallow N- layer covered with nitride, a submicron-wide dummy gate mask consisting of upper and lower portions made of dissimilar materials is formed. Multilayer organic and sidewall image transfer techniques are employed for forming the mask. The nitride is etched using the gate mask. N+ source/drain are formed by ion implantation. The lower portion of the gate mask is etched to expose the periphery of the nitride. Refractory metal for source/drain contacts is deposited. An oxide laeyr is deposited to passivate the source/drain contacts and to fully cover the exposed nitride periphery. The gate mask is removed. High temperature anneal is accomplished to simultaneously activate the N+ regions and anneal the contact metal. By RIE the exposed nitride removed leaving submicron spacers thereof. Gate metal is deposited in the gate region. Excess gate metal is removed to obtain a gate which has a planar top and has little lapping over the source/drain contacts.