Increasing Mobility in 4H-SiC MOSFETs with Deposited Oxide by In-Situ Nitridation of SiC Surface

We present the improvement of SiO 2 /4H-SiC interface quality and high field-effect (FE) mobility ( µ FE ) in 4H-SiC MOSFETs. This is achieved by introducing a nitrous oxide (N 2 O) plasma in-situ pre-treatment before gate stack formation using plasma enhanced chemical vapour deposition (PECVD) oxide followed by a post deposition anneal (PDA) in diluted N 2 O for times ranging from 30 to 120 minutes thereby creating an ultra-thin thermally grown SiO 2 layer at the SiO 2 /4H-SiC interface. MOS capacitors with SiO 2 deposited on in-situ pre-treated SiC surfaces had a lower density of interface traps ( D IT ) for all PDA durations, compared with devices having untreated PECVD oxides or control devices with 30 nm thermally grown oxide. After PDA for 90 minutes, a minimum D IT value of 1.2×10 11 cm -2 ·eV -1 was measured. A peak µ FE value reaching 94 cm 2 /(V·s) was measured in n -channel planar MOSFETs fabricated with PECVD oxide on in-situ pre-treated devices, which significantly exceeds a maximum µ FE of 6 cm 2 /(V·s) in control devices.