A 0.1-μm MHEMT millimeter-wave IC technology designed for manufacturability

Abstract We describe and discuss our approach to improved manufacturability of millimeter-wave InP-type HEMT IC technology. The main ingredients are the use of (1) GaAs (rather than InP) as substrate, with a buffer that grades the lattice constant to that of the high-mobility Ga 0.47 In 0.53 As channel; (2) low-resistance non-alloyed ohmic contacts with good reliability and reproducibility; (3) an e-beam process that produces 0.1-μm T-gate fingers with one exposure and (4) two-step selective etching of the gate trough for good uniformity. The process is compatible with standard GaAs FET IC front and back end unit processes, including backside vias. The yield, uniformity and performance of devices and circuits made on this metamorphic (MHEMT) material are consistently as good as those we get using InP substrates. The reliability of our devices, whether made on GaAs or InP substrates, is limited by impact ionization in the channel, which has also been linked to R d -degradation and burnout. At low-noise drain bias ( V d =1 V), where the impact ionization is small, we have demonstrated reliability, i.e. extrapolated MTTF at 125°C channel temperature is >10 6 h. This is as good as FETs made on InP substrates.