Layered metal and highly doped MBE Si contacts for 4H-SiC power devices

Abstract

This paper presents two contacting methods for 4H-SiC power devices: layered metal and highly doped molecular beam epitaxy (MBE) silicon (Si) contacts. Layered metallic contacts are based on nickel (Ni), aluminium (Al) and titanium (Ti), displaying low specific contact resistivities to p-type 4 H-SiC in the range of 10-4 -10-6 Ω cm2 . Ti based contacts display the lowest specific contact resistivity of 5.02 × 10-6 Ω cm2 . X-ray diffraction (XRD) scans point to enhanced silicide formation for Al-Ti(Ti3SiC2) and Al-Ni(NixSi) contacts that displayed ohmicity. The second contacting method presents the electrical and physical characteristics of highly doped MBE Si layers above 4H-SiC. This form of Si/SiC heterojunction contact presents significant SiC processing advantages for the semiconductor industry, eliminating high temperature annealing steps. Electrical measurements have been performed and highlight the Schottky-type rectifying properties displayed by Si/SiC heterojunctions. A scanning electron microscope (SEM) was employed to examine the surface morphology of the MBE Si layers. Smoother surfaces with less island formation have been correlated to low temperature (500°C) MBE Si growth.