EB-Writing n+self-aligned GaAs MESFETs for high-speed LSIs

Electron-beam direct writing has been applied to the fabrication of n⁺self-aligned (SAINT) GaAs MESFETs for high speed LSIs in order to achieve very short gate length below a half micrometer. In this application, position deviation due to semi-insulating substrate charge-up has been completely avoided by using a newly developed multilayer resist in which thin metal film is inserted. The short channel effects have been successfully reduced by decreasing the thickness of the n⁺-layers. As the result, an extremely fast switching speed of 16.7 ps/gate has been obtained at room temperature from a ring oscillator with 0.3 µm gate length SAINT FETs.