Characterization of sputtered titanium silicide ohmic contacts on n-type 6H-silicon carbide

Titanium silicide (TiSiX) contacts sputter deposited onto p-type SiC-wafers carrying a 5μm thick nitrogen-doped n-type (ND−NA=5.1018 cm−3) epitaxial layer have been electrically characterized. While the as-deposited contacts have revealed rectifying behavior, the current–voltage characteristic has became ohmic after sample treatment by rapid thermal annealing (RTA) in argon at temperatures above or equal to 1000°C. To determine the specific contact resistance ρC, the common linear transmission line model (TLM) has been used. However, the ρc values measured with the TLM method may be subject to systematic errors because the TLM is based on a simplified model of the metal–semiconductor contact. To quantify these errors, three-dimensional finite element models of TLM-structures with various geometries have been studied with the FEM-software ANSYS®. By comparing the simulation results with experimental data, ρc for annealed TiSiX contacts has been found to be ≤8·10−6 Ω cm2. This agrees very well with the best results published in the literature (J. Crofton et al.; Phys. Stat. Sol. B202 (1997) 581–603). Secondary neutral mass spectrometry has been used to examine the reaction between TiSiX and SiC during RTA showing that for high temperature annealing (1180°C) the ternary phase Ti3SiC2 is formed at the interface between a TiSi2 overlayer and the SiC substrate.