Structural and electrical characterisation of titanium and nickel silicide contacts on silicon carbide

Abstract

The interfacial reaction and phase formation as a function of the annealing temperature (600–1000°C) and time were investigated on both titanium and nickel thin films evaporated on n-type 6H-SiC (0001) substrate. The study was carried out employing a combination of Rutherford backscattering spectrometry, X-ray diffraction, transmission electron microscopy and sheet resistance measurements. A correlation has been found between the annealing process and the electrical measurements on transmission line method (TLM) structures and Schottky diodes. In the case of titanium, the formation of different phases in the analysed temperature ranges significantly changes the electrical properties. In fact, while a double layer of TiC and Ti 5Si 3 was formed at 900 and 950°C, the ternary phase Ti 3SiC 2 was observed only at 1000°C. With this high temperature process the specific contact resistance decreases from 10 −4 to 6.7×10 −5 Ωcm 2. In the case of nickel silicide the only phase that has been observed between 600 and 950°C was the Ni 2Si. The carbon of the consumed silicon carbide layer has been dissolved in the silicide film, during the reaction, forming carbon precipitates. The specific contact resistance reaches the lowest value (3.6×10 −5 Ωcm 2) after the highest temperature anneal. The Ni 2Si/SiC Schottky diodes show almost ideal characteristics ( n=1.07) and a barrier height of ∼1.3 eV. From the electrical characterisation, a non-uniform Schottky barrier height seems to be formed.