Carbon-Cap for Ohmic Contacts on Ion-Implanted 4H–SiC

Abstract

A pyrolyzed photoresist film is commonly used as a protective cap of the surface of ion-implanted wafers during the postimplantation 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 postimplantation annealing and before any other processing step of the SiC wafer. Here, we show that this C-cap is a continuous, hard, black, mirrorlike, and planar thin film that can be patterned by a reactive ion etching -based plasma for the fabrication of ohmic contact pads on both - and -implanted . This C-cap material has an electrical resistivity of and a good resistance against scratch. Al (1% Si) wires can be ultrasonically bonded on the C-cap pads. Such a bonding and the C-cap adhesion to the implanted surface are stable for electrical characterizations in vacuum between room temperature and . The measured specific contact resistance of the C-cap on a -implanted is at room temperature. Micro-Raman characterizations show that this C-cap is formed of a nanocrystalline graphitic phase.