ELECTRON-BEAM RESIST TECHNOLOGY FOR GaAs MICROWAVE DEVICE FABRICATION

摘要

Monolithic microwave integrated circuits (MMICs) utilizing high-gain, low-noise HEMT (high electron-mobility transistor) devices are finding increasingly wide usage in satellite communication and other applications. To achieve the desired performance, the HEMT gate electrode is fabricated with a 'mushroom' cross-section, which allows both a low gate stripe resistance and a short gate length. The development of a multi-layer electron resist process to achieve this objective is described in detail. This technology, based on methacrylate polymer and co-polymer resists, has been optimized to provide an excellent yield of Ti/Pt/Au gates fabricated by a lift-off metallization procedure. The use of a single developer, based on a mixture of isopropyl alcohol and water, is a novel feature of the process described here, and has significant benefits in terms of cleanliness, non-toxicity and process latitude. Some applications of this technology are outlined.