Failure Analysis on TiAl Metallization Process for Ohmic Contact on 4H-SiC pMOSFET

Abstract

SiC is suitable for high-power and high-temperature applications due to its' wide energy bandgap and high thermal conductivity. Most literature focus on SiC nMOSFET due to higher electron mobility than hole. In this work, we fabricated 4H-SiC pMOSFET using TiAl alloy as contact metal to reduce the contact resistivity. However, ultrahigh leakage current was measured among all terminals of the pMOSFET. By comparing with different contact schemes, the failure mechanism is attributed to Al spiking into the underneath poly-Si and SiO2 during the metallization process. Using suitable blocking layer such as LPCVD Si3N4 (300 nm) or PECVD Si3N4 (100 nm) on SiO2 (200 nm) can avoid Al spiking so that conventional pattern topology and TiAl metallization process can be used on device fabrication.