Advanced direct write electron beam lithography for GaAs monolithic microwave integrated circuit production

Abstract

Direct write electron beam lithography has been used for several years to pattern submicrometer and sub-half-micrometer gates for GaAs monolithic microwave integrated circuit (MMIC) devices. The e-beam systems used at this process step have generally been vector scan Gaussian beam machines operated in a step and write exposure mode. These systems have very low throughput and are better suited to research and development environments than large volume production. In order to meet the production requirements at the new Raytheon Monolithic Microwave Center, we have sought to adapt the Perkin–Elmer advanced electron beam lithography equipment (AEBLE)-150 system for use on GaAs. Results of early usage of the AEBLE system for direct write GaAs will be presented. Eightfold improvement in throughput for typical MMIC devices compared to results obtained on an earlier model e-beam machine will be shown. Both metalized (by liftoff) and etched alignment markers have been used; alignment strategy and a comparison of these alignment marks will be discussed. Results from the AEBLE demonstrating sub-half-micrometer lighography on GaAs will be presented. System issues related to handling GaAs wafers and areas in need of improvement will be briefly discussed.