Formation of Low-Resistance Ohmic Contacts on Lightly Doped 4H-SiC Epitaxy without Using Ion Implantation

Abstract

The realization of silicon-carbide-based sensors usually requires lightly doped epitaxy as the functional region, which does not allow any induced defects from ion implantation. The constraint makes the formation of low-resistance ohmic contacts a challenge. This letter describes the approach of using a Ni/Ti/Ni trilayer metal stack and high-temperature annealing to form nickel-silicide compounds for a low specific contact resistivity of 6.18 mΩ·cm² on 4H-SiC epitaxy layer with a doping concentration of 2.19 × 10¹⁵/cm³. The scheme also produces titanium carbide and titanium silicon carbide, serving as the carbon diffusion barrier to secure good nickel-silicide compound formation. The influences of annealing temperature and titanium thickness on ohmic contact quality are discussed.