Phase composition and electrical characteristics of nickel silicide Schottky contacts formed on 4H–SiC

Abstract

4H–SiC Schottky diodes with nickel silicide contacts were formed by consecutive deposition of a titanium adhesion layer, 4 nm thick, and nickel, 100 nm thick, followed by annealing at temperatures between 600 and 750 °C. It was found that contacts with barrier heights of 1.45 eV which consist mainly of single nickel monosilicide (NiSi) phase were formed in the 600–660 °C temperature range, while annealing at around 750 °C led to the formation of Ni2Si Schottky contacts with barrier heights of 1.1 eV. Annealing at intermediate temperatures resulted in the nucleation of Ni2Si grains embedded in the NiSi film which were directly observed by micro-Raman mapping. It was shown that the thermodynamically unfavourable NiSi phase appeared in the 600–660 °C temperature range due to control of the Ni–SiC solid-state chemical reaction by nickel diffusion through the titanium diffusion barrier.