Tunneling Effects in NH<sub>3</sub> Annealed 4H-SiC Trench MOSFETs

Abstract

The interface between the gate oxide and silicon carbide (SiC) has a strong influence on the performance and reliability of SiC MOSFETs and thus, requires special attention. In order to reduce charge trapping at the interface, post oxidation anneals (POAs) are conventionally applied. However, these anneals do not only influence the device performance, such as mobility and on-resistance, but also the gate oxide reliability. We study the oxide tunneling mechanisms of NH3 annealed 4H-SiC trench MOSFET test structures and compare them to devices which received a NO POA. We show that 3 different mechanisms, namely trap assisted tunneling (TAT), Fowler-Nordheim (FN) tunneling and charge trapping are found for NH3 annealed MOS structures whereas only FN-tunneling is observed in NO annealed devices.The tunneling barrier suggest a trap level with an effective activation energy of 382 meV to enable TAT.