High-performance 0.1 μm-self-aligned-gate GaAs MESFET technology

We report on 0.1-μm gate-length self-aligned Au/WSiN-gate GaAs MESFET technology. The FET we produced using this technology has a planar structure with a selective ion-implanted channel layer and self-aligned n⁺- layers. One of the key structural parameters affecting device performance is the offset separating the gate electrode from lightly-doped source and drain n´ layers. A 0.1-μm gate length is attained by i-line photolithography using an anti-reflection top coat film and SF₆ gas ECR plasma etching. We demonstrate FET uniformity in a 3-in wafer and excellent high-frequency performance. The standard deviation of the threshold voltages is 0.058 V with an average of about 0 V at a gate length of 0.126 μm and the current gain cutoff frequency (f_T) is 168 GHz at a gate length of 0.06 μm