Fabrication of multigate power GaAs FET's using electron lithography

GaAs Schottky barrier FET's employing crossover technology have been fabricated using electron lithography for direct exposure on the wafer. Submicron realignments to gate structures with 2µm minimum feature sizes have been regularly achieved. Direct wafer exposure offers the advantages of high resolution, accurate alignment, flexibility in making design changes and speed in turnaround time but the processes used to pattern the substrate are different than those used with photoresist technology. The processing details as well as D.C. and R.F. results are described. At 4.4 GHz a crossover device with a gate width of 7mm produced a saturation power of 3.1 watts, a 1 db compression power of 2.5 watts and a small signal gain of 5.0 dB. Another device with a gate width of 3.5mm has produced a saturation power of 1.8 watts, a 1 dB compression power of 1.4 watts and a small signal gain of 6.0 dB.