Low-temperature, high-concentration laser doping of 4H-SiC for low contact resistance

Abstract

We propose low-temperature and high-concentration doping of 4H-silicon carbide (4H-SiC)(0001) by KrF excimer laser irradiation of source films on a 4H-SiC substrate, in which a dopant atom is included. In n-type doping, a SiN x film with a thickness of 100 nm was deposited on an n-type 4H-SiC(0001) substrate by chemical vapor deposition. A gas supply nozzle for ambient environment control was installed to prevent oxidation of the SiC surface. High-concentration nitrogen doping (~1 × 10 21 /cm 3 at the surface) was achieved by laser ablation of the SiN x film. Al/Ti electrodes were formed on the doped area at a room temperature, and a contact resistance of 2.2 × 10 -5 Ω･cm 2 was obtained, which is sufficiently small for the backside contact resistance of Schottky barrier diodes. In p-type doping, an Al film with a thickness of 240 nm was deposited on a 4H-SiC substrate by sputtering deposition. After laser irradiation of the Al film in ambient Ar, high-concentration Al doping (~1 × 10 21 /cm 3 at the surface) was achieved. Al/Ti electrodes were formed on the doped area at a low temperature of 600 °C, and a contact resistance 1.9 × 10 -4 Ω･cm 2 was obtained. We conclude that low-temperature and high-concentration doping of 4H-SiC for low contact resistance can be achieved by laser ablation of the source films on the 4H-SiC substrate.