Chemical and Structural Characterization of the Ni-Ti Alloy/6H-SiC Contacts

Abstract

AbstractNi-Ti alloy is a promising candidate for high-temperature contact metallization for SiC electronic devices. In the present study Ni-Ti alloy thin films (100 nm) of two different compositions (Ni90Ti10 and Ni50Ti50) were coevaporated on 6H-SiC substrate. Interfacial reactions, microstructure, compositional changes, and phase formation were investigated as functions of heat-treatments in the range of 400–800 °C. The study was carried out using Auger electron spectroscopy, x-ray diffraction, and analytical transmission electron microscopy. In the case of the Ni90Ti10 alloy the interaction was found to begin at 450 °C. Ni and C are the dominant diffusing species. The reaction zone is divided into three layers. In the first layer, adjacent to the SiC substrate, the presence of a Ni-rich silicide, Ni2Si, and C precipitates, was observed. The second layer is composed mainly of TiC, while the third - of Ni2 Si. In the case of the Ni50 Ti50 alloy the interaction began at 800 °C. Carbon is the dominant diffusant. The reaction zone is divided into two layers. The first, next to the substrate layer is composed of epitaxially grown TiC and the second - of Ni3Ti2Si compound. A thin (∼5 nm) amorphous discontinuous layer was found at the TiC/SiC interface. Factors controlling phase formation in the Ni-Ti/SiC system are discussed.