Ohmic contacts with heterojunction structure to N-type 4H-silicon carbide by N+ polysilicon film

The polysilicon ohmic contacts to n-type 4H-SiC have been fabricated. TLM (Transfer Length Method) test patterns with polysilicon structure are formed on N-wells created by phosphorus ion (P+) implantation into Si-faced p-type 4H-SiC epilayer. The polysilicon is deposited using low-pressure chemical vapor deposition (LPCVD) and doped by phosphorous ions implantation followed by diffusion to obtain a sheet resistance of 22Ω/square The specific contact resistance ρc of n+ polysilicon contact to n-type 4H-SiC as low as 3.82×10-5Ωcm2 is achieved. The result for sheet resistance Rsh of the P+ implanted layers in SiC is about 4.9kΩ/square. The mechanisms for n+ polysilicon ohmic contact to ntype SiC are discussed.