Carbon-cap for Ohmic Contacts on Ion Implanted 4H-SiC

A pyrolyzed photo-resist film is commonly used as a protective cap of the surface of ion implanted 4H-SiC wafers during the post implantation annealing process with the aim to prevent Si sublimation and step bunching formation. Such a film that is called Carbon-cap (C-cap) is always removed after post implantation annealing and before any other processing step of the SiC wafer. Here we show that this C-cap is a continuous, hard, black colour, mirror like and planar thin film that can be patterned by a RIE O2-based plasma for the fabrication of ohmic contact pads on both Al+ and P+ implanted 4H-SiC. This C-cap material has an electrical resistivity of 1.5 x 10E3 cm and a good resistance against scratch. Al (1% Si) wires can be ultrasonic bonded on the C-cap pads. Such a bonding and the C-cap adhesion to the implanted 4H-SiC surface are stable for electrical characterizations in vacuum between room temperature and 450°C. The measured specific contact resistance of the C-cap on a 1 x 10E20 cm 3 P+ implanted 4H-SiC is 9 x 10E5 cm2 at room temperature. Micro-Raman characterizations show that this C-cap is formed of a nano-crystalline graphitic phase.