Comparison of Ti and Pt silicon carbide Schottky rectifiers

Abstract

This paper describes the fabrication and characterization of high breakdown voltage titanium and platinum Schottky contacts to silicon carbide for high temperature and high frequency applications. Diodes fabricated with both Pt and Ti showed excellent on-state conduction characteristics with forward voltage drop of approximately 1.1 V at 100 A/cm/sup 2/ for a temperature range of 25 degrees C to 200 degrees C. The reverse I-V characteristics exhibited sharp breakdown, with breakdown voltage at 25 degrees C exceeding 400 V and 500 V for Pt and Ti diodes, respectively. The barrier height for the as-deposited Pt and Ti Schottky contacts as determined by the I-V and C-V measurements was found to be 1.05+or-0.05 eV and 0.85+or-0.05, respectively. The effects of post-metallization annealing on the electrical and material properties of the metal/SiC interface were investigated to determine the high temperature thermal stability of these devices. On isochronal annealing, these devices were found to be stable up to 500 degrees C without any significant changes in the electrical properties. After 600 degrees C anneal, Pt devices showed an increase in the forward voltage drop and barrier height, while the characteristics of the Ti devices remain unchanged. The changes in the electrical characteristics for these devices are correlated with changes in the SiC/metal interface which was analyzed using RBS and Auger spectroscopy.