Y-gate submicron gate length GaAs metal-semiconductor field effect transistors

Submicron GaAs field effect transistors are demonstrated using a simple low temperature SiNx deposition and etchback process with negative resist profiles produced on an optical stepper. Conformal coverage of the SiNx over the resist openings and subsequent low bias (−75 V) SF6 based plasma dry etching produces reproducible features down to 0.1 μm, from initial openings of 1–2 μm. Subsequent gate etch and lift‐off metal deposition produces a Y‐shape gate with similar characteristics to the more conventional T‐shape gates fabricated with multilevel electron‐beam resists. This is a simple technique for extending the resolution of standard optical lithography tools.