The intermediate semiconductor layer for the ohmic contact to silicon carbide by Germanium implantation

An array of TLM(transfer length method) test patterns is formed on N-wells created by P⁺ ion implantation into Si-faced p-type 4H-SiC epilayer. The Ge⁺ ion implantations are used to form the intermediate semiconductor layer (ISL) of nickel-metal ohmic contacts to n-type 4H-SiC. The specific contact resistance pc as low as 4.23 times 10^-5 Omegacm² is achieved after annealing in N₂ at 800 degC for 3 min, which is much lower than that (>900degC) in the typical SiC metallization process. The sheet resistance Rsh of the implanted layers is 1.5 kOmega/square. A graphite capping layer is used to protect the surface of SiC during post-implantation annealing.