Formation of the intermediate semiconductor larger for the Ohmic contact to silicon carbide using Germanium implantation

By formation of an intermediate semiconductor layer (ISL) with anarrow band gap at the metallic contact/SiC interface, this paperrealises a new method to fabricate the low-resistance Ohmic contactsfor SiC. An array of transfer length method (TLM) test patterns isformed on N-wells created by P⁺ ion implantation intoSi-faced p-type 4H-SiC epilayer. The ISL of nickel-metal Ohmiccontacts to n-type 4H-SiC could be formed by using Germanium ionimplantation into SiC. The specific contact resistance ρ_c as low as 4.23× 10^-5~Ωega cdotcm² isachieved after annealing in N₂ at 800~°C for 3~min,which is much lower than that (>900~°C) in the typical SiCmetallisation process. The sheet resistance R_sh of theimplanted layers is 1.5~kΩega /Box. The technique forconverting photoresist into nanocrystalline graphite is used toprotect the SiC surface in the annealing after Ge⁺ ionimplantations.