Electron-beam lithography in n+self-aligned GaAs MESFET fabrication

An electron-beam direct-writing technology for the fabrication of short-channel n⁺sef-aligned (SAINT) GaAs MESFET´s is discussed. A four-level multiresist which includes a thin Mo layer is developed to avoid charging in the semi-insulating GaAs substrate. The alleviation of short channel effects is experimentally demonstrated by reducing the n⁺layer depth. A ring oscillator with a 0.3-µm-long gate SAINT FET shows a minimum propagation delay time of 16.7 ps with an associated power dissipation of 7.3 mW, which is one of the fastest among room-temperature semiconductor devices.