GaAs Metal Insulator Semiconductor Field Effect Transistor with Oxi-Nitrided Gate Film Formed by New Process Utilizing Al Layer as Resist Film for Selective Etching, Oxi-Nitridation and Lift-Off

Abstract

We have reported that the oxi-nitridation of GaAs forms an insulator–semiconductor interface without deteriorating the crystallographic order of GaAs, and is applicable to the fabrication of compound semiconductor devices with metal–insulator–semiconductor (MIS) gates. A problem with oxi-nitridation is that nitrogen plasma ashes and thins the photoresist and hence restricts the possible nitrogen processing times even if a long nitridation is desirable for a better interface quality. To counteract this restriction, we developed a new processing technique utilizing an 0.3-µm-thick Al layer as a mask for selective etching, oxi-nitridation and lift-off. A high transconductance (185 mS/mm) and sharp pinch-off were obtained by a long (8 h) nitridation.