Abstract
Mixed lithography combining a 140 keV Be ++ focussed ion beam and a 60kV electron beam has been applied to fabricate T-section structures for use as gate electrodes in GaAs MESFETs intended to operate in monolithic microwave integrated circuits. Gate metallization is formed by lift-off using a single resist layer and a single development stage, after successive electron and ion beam exposures. Aluminium T-gates with gate lengths of 0.22μm have been fabricated with resistances of 90Ω/mm. Air bridges have been fabricated using high-voltage and low-voltage electron-beam lithography on thick resist layers and lift-off in two stages; firstly to form pillars 6μm high, and secondly to join them by a span 5μm above the substrate.
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