Novel high-yield trilayer resist process for 0.1 μm T-gate fabrication

By utilizing a novel ZEP/PMGI/ZEP trilayer resist process, GaInAs/AlInAs T-gate modulation-doped field effect transistors on InP with 0.1 μm gate lengths have been demonstrated. The trilayer resist requires only a single exposure. An overhang structure for liftoff, with a 0.1 μm footprint, is created by a sequence of infinitely selective developments for each layer. Linewidths as narrow as 65 nm have been obtained. Devices with a maximum current of 860 mA/mm, extrinsic transconductances of 658 mS/mm, and a current-gain-cutoff frequency ft of as high as 203 GHz have been fabricated. Yields as high as 96% and a threshold voltage uniformity of 34 mV (1 sigma) have been achieved on a 2 in. wafer.