DEVELOPMENT OF A 100-NM GATE POWER HEMT USING 4-LAYER RESIST AND FLEXIBLE E-BEAM EXPOSURE STRATEGIES

A 100 nm gate length power HEMT has been fabricated, which can be appl ied in power amplifiers throughout the millimeter-wave spectrum, as we ll 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 vo ltage (V-bdg > 10 V) Excellent uniformity is assured using a dry etch gate recess. In order to reduce the resistance of the gate, a ''mushro om'' (T-gate) structure is needed for the 100 nm gate, which is made b y lift-off using a four-layer PMMA (with MAA) resist and e-beam exposu res. By using our Beamwriter User Modifiable Programming Shell (BUMPS) for the EBPG (Philips-Leica 4V-HR), existing layouts can easily be ad apted for simultaneous variation (on one wafer) of T-gate central expo sure dose, side exposure dose, side exposure width and central-to-side -exposure distance. Combination of the experimental results with. expo sure and development computer simulations, resulted in an optimized ex posure strategy.