AN EDGE-DEFINED TECHNIQUE FOR FABRICATING SUBMICRON METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR GATES

A new technique has been developed to fabricate submicron gates in GaAs metal-semiconductor field effect transistors (MESFETs) using simple contact lithography. The technique employs a multiple layer resist structure and angle evaporation to define a conformal aluminum mask above the wafer surface. The gate length of the aluminum mask is well controlled by an evaporation angle and a resist thickness. The pattern transfer to the wafer surface is compatible with a recessed gate technology. In a production environment, the process is capable of producing quarter-micron MESFETs with less than +/- 150-angstrom-(1-sigma)-gate length variation across a 2-in. wafer.