Dry etch development of W/WSi short Gate MESFETs

摘要

The use of refractory metal thin films in the fabrication of high-speed, high-density GaAs field effect transistors (FETs) are prominent with applications as interconnects, via plugs, and ohmic and Schottky contacts. Tungsten and tungsten silicide can be used in a self-aligned gate process as the ion implantation mask during the formation of source and drain regions for metal-semiconductor FETs (MESFETs). The gate etch must be highly anisotropic to accurately define the implant region. Reactive ion etch (RIE) techniques have been used to etch W and WSi films in fluorine-based discharges. The etch mechanism tends to be very chemical and often results in severe undercutting of the feature due to the lateral attack of the refractory metal. The undercut is often so severe that critical dimensions are not maintained and gate profiles do not properly align to the implant region resulting in poor device characteristics. As device design rules shrink, the etch requirements and patterning techniques become even more critical.