Fabrication of self-aligned, t-gate hemt

Abstract

A generally T-shaped gate is formed by electron beam irradiation of a multilevel resist structure on a substrate. The resist structure has an upper layer which is more sensitive to the electron beam than a lower layer thereof. A generally T-shaped opening is formed in the resist structure by etching of the irradiated areas. An electrically conductive metal is deposited to fill the opening and thereby form a T-shaped gate on the substrate. After the resist layer structure and metal deposited thereon is removed, a masking layer is formed on the substrate around the gate, having an opening therethrough which is aligned with and wider than the cross section of the gate, and defining first and second lateral spacings between opposite extremities of the cross section and adjacent edges of the opening. Deposition of an electrically conductive metal forms source and drain metallizations on the substrate on areas underlying the first and lateral spacings respectively. The metallizations are self-aligned to the gate and separated therefrom by the masking effect of the gate during the metal deposition. The gate may have an asymmetrical top section which provides a larger spacing between the gate and drain metallization than between the gate and source metallization to increase the breakdown voltage of the device. Insulative oxide sidewalls may be formed on the gate.