Application Of Vector Scan E-Beam Lithography In Fabrication Of Gaas Devices

The growing interest in the use of Gallium Arsenide semiconductor materials has presented many opportunities for device operational speed improvements but has also presented many problems for the device maker. In particular a whole new range of processing techniques have been needed which are significantly different to those used routinely in Silicon processing. In addition, to obtain the best operational characteristics, device feature dimensions, linewidth tolerance and overlay accuracies are significantly more demanding than current silicon practices require. This "lithographic challenge" is at its most extreme where microwave active components like MESFET transistors are required. Present day routine devices require 0.5 to 0.25 micron gate lengths whilst leading edge devices need 0.1 micron or below complicated by the need for fabrication in three dimensions for "T" section structures. These are necessary to provide adequate gate conductivity and power handling whilst maintaining the narrow gate length contact.