Pm. Frijlink et al., DEVELOPMENT OF A 100-NM GATE POWER HEMT USING 4-LAYER RESIST AND FLEXIBLE E-BEAM EXPOSURE STRATEGIES, Microelectronic engineering, 35(1-4), 1997, pp. 313-316
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.