Gate-to-ohmic metal contact scheme for III-V devices

摘要

A direct shorting contact structure comprising a metal layer (18') makes ohmic contact with a source (10) and/or drain (12) region and with a gate electrode (22). The direct contact between source or drain and gate over the active region (16) reduces the area otherwise required for such contact and eliminates a second layer (24) of interconnection metallization otherwise required for such contact. The metal layer preferably comprises a first layer (18'a) of a material selected from the group consisting of gold-germanium, nickel-germanium, gold-germanium-nickel, molybdenum-germanium, and aluminum-germanium in ohmic contact with the source or drain region and with the gate electrode and a second layer (18'b) of a good electrically conductive, thermally stable, electromigration-resistant metal capable of providing good step coverage overlying the first layer. An example of the second layer is tungsten and its nitrides and silicides. Such a composite layer avoids step coverage and reliability problems which exist with other metallization schemes.