A DUV-Defined-Negative Resist/EB-Defined-Positive Resist Two-Layer Resist System for the Fabrication of T-Shaped Gate

We have developed a DUV-defined-negative resist/EB-defined-positive resist two-layer resist system to fabricate T-shaped gates of GaAs MESFET devices. In this resist system, the head of the T-shaped gate is fabricated in the top layer negative resist using a deep-UV exposure and the foot of the T-shaped gate is fabricated in the bottom layer positive resist using an e-beam exposure. Resist profiles are easily controlled because exposures and developments of the top and bottom layers are completely separated. A sub quarter-micron T-shaped gate with the head of the width of more than one micron was successfully fabricated by using this two-layer resist system. This two-layer resist system has wide applicablity for the fabrication of GaAs MESFET devices.