Submicrometer gate fabrication of GaAs MESFET by plasma etching

Dry etching is employed in the direct fabrication of the main part of semiconductor devices. A submicrometer Schottky-barrier gate is constructed for GaAs MESFET's. The gate has a double-metal-layer configuration. The Au top metal layer is first delineated by ion milling with monitoring equipment, i.e., ion microanalyzer. The metal layer in contact with the GaAs substrate is chemically etched in CF4gas plasma. Controlled side etching of the Mo metal produces the submicrometer gate, leaving a wider top metal layer of Au. The amount of side etching deviates less than 0.05 µm and the gate length is reduced to 0.1 µm. No appreciable damage to the GaAs substrate is found as a result of plasma etching. Half-micrometer gate GaAs MESFET's fabricated by this dry etching technique achieved high-gain and low-noise performance in the X-band.