Ohmic contact formation on n-type 6H-SiC using polysilicon and silicides

Silicon carbide with its wide bandgap, high thermal conductivity, and high breakdown electric field is an attractive material to be used for applications in high power, and high temperature semiconductor devices. For such applications, it is extremely important to be able to form stable ohmic contacts that can withstand high temperature operations. Various metals have been attempted to form ohmic contacts on SiC such as Ni, Ti, and Al. However it has been observed that these metallization schemes exhibit degraded performance due to carbon accumulation by forming carbides at the interface. In this study, polycide (polysilicon with silicide) based metallizations have been investigated, using NiSi₂ and TiSi₂. Silicides of Ni and Ti have been synthesized employing a layer of heavily doped polysilicon to prevent any form of reaction between the metal and the carbon at the SiC interface. Using a 0.5cm² n-type 6H-SiC samples with various doping concentrations, the electrical and structural properties of NiSi₂ and TiSi₂ have been examined by fabricating linear transmission line model (TLM) structures. I-V characterizations have been carried out to determine the specific contact resistivity