Development of a 100 nm gate power HEMT using four-layer resist and flexible e-beam exposure strategies

Abstract

A 100 nm gate length power HEMT has been fabricated, which can be applied in power amplifiers throughout the millimeter-wave spectrum, as well as in very low noise amplifiers. This process permits amplification up to the W-band. The transistors are made using a double recess and an optimized epitaxial structure in order to maximize the breakdown voltage (Vbdg > 10 V). Excellent uniformity is assured using a dry etch gate recess. In order to reduce the resistance of the gate, a “mushroom” (T-gate) structure is needed for the 100 nm gate, which is made by lift-off using a four-layer PMMA (with MAA) resist and e-beam exposures. By using our Beamwriter User Modifiable Programming Shell (BUMPS) for the EBPG (Philips-Leica 4V-HR), existing layouts can easily be adapted for simultaneous variation (on one wafer) of T-gate central exposure dose, side exposure dose, side exposure width and central-to-side-exposure distance. Combination of the experimental results with exposure and development computer simulations, resulted in an optimized exposure strategy.