Formation of ohmic contacts to α-SiC and their impact on devices

Abstract

The history of power electronic semiconductor devices is reviewed that leads to a discussion of new materials. The wide bandgap and good thermal conductivity of SiC permit its use at high temperatures, and the high electric field breakdown is favorable for high power devices. However, there remain a number of key problems with SiC semiconductor technology that must be solved before reliable production can begin. Difficulties with the insulator-to-SiC interface, SiC epitaxial material, passivation, doping, and stability of contacts drive viable device structures. One issue, the formation of electrical contacts, is described in more detail. In particular, the impact of SiC preparation procedures, surface roughness, and deposition conditions are discussed, e.g., variations in the chemical cleaning process affect the removal of overlayers and/or the roughneing of the SiC surface. Studies have shown that this cleaning or etching step can in turn affect device performance. At present, fabrication of the best quality contacts is interlinked with other material problems, and even to obtain adequately low resistivities, constraints are placed on the processing of devices.