Low ohmic cobalt silicide contacts to p-type 6H-SiC

Abstract

Summary form only given, as follows. Thermally stable ohmic contacts with low specific contact resistivities is one of the key issues that needs to be addressed to enable successful fabrication of SiC power devices for commercial applications. Recent advances in epilayer growth provides highly Al-doped p-type layers which form the basis for low ohmic contacts. Most of the earlier reported ohmic contacts to p-type 6H-SiC have used Al-based metallizations yielding resistivities approximately in the 10/sup -4/-10/sup -5/ /spl Omega/cm/sup 2/ range but with poor thermal stability. The lowest resistivities were usually achieved after a burn-in around 800-1000/spl deg/C and further annealing at higher temperatures or for extended time decayed the ohmic properties. However, refractory metal silicides with their low resistivity, thermal stability and overall manufacturability look promising as contact materials to SiC for high temperature operation. In this study thermally stable CoSi/sub 2/ ohmic contacts to p-type 6H-SiC possessing low specific contact resistivity in the mid 10/sup -6/ cm/sup 2/ region are reported. TLM structures were fabricated on a 1 /spl mu/m thick Si-face Al-doped epilayer on top of an n-type substrate through a sequential electron beam evaporation of Co and Si layers followed by a two step vacuum annealing process at 500/spl deg/C and 900/spl deg/C. The specific contact resistivity is investigated as a function of operating temperature (20-200/spl deg/C), current density and ageing at 1100/spl deg/C in a vacuum furnace.