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

Abstract

By formation of an intermediate semiconductor layer (ISL) with a narrow band gap at the metallic contact/SiC interface, this paper realises a new method to fabricate the low-resistance Ohmic contacts for SiC. An array of transfer length method (TLM) test patterns is formed on N-wells created by P+ ion implantation into Si-faced p-type 4H-SiC epilayer. The ISL of nickel-metal Ohmic contacts to n-type 4H-SiC could be formed by using Germanium ion implantation into SiC. The specific contact resistance ρc as low as 4.23 × 10−5 Ωcm2 is achieved after annealing in N2 at 800 °C for 3 min, which is much lower than that (> 900 °C) in the typical SiC metallisation process. The sheet resistance Rsh of the implanted layers is 1.5 kΩ/□. The technique for converting photoresist into nanocrystalline graphite is used to protect the SiC surface in the annealing after Ge+ ion implantations.