Impact of ALD Oxidant and Deposition Temperature on Electrical Characteristics of Al2O3/SiO2/SiC MOS-Capacitors

The increased demand for SiC power MOSFETs requires gate dielectrics with low defect densities and high reliability under high electric field and temperature conditions. In this work, we examine how oxidant chemistry and deposition temperature affect the electrical properties of Al 2 O 3 /SiO 2 bilayer dielectrics formed in n-type 4H-SiC MOS capacitors. These structures consist of a thin SiO 2 interfacial layer, over which Al 2 O 3 is deposited via ALD using three different oxidants at a temperature of 150–350°C. C–V and temperature-dependent I–V (25–150°C) measurements show that the choice of oxidant influences the flat band voltage shift and leakage current density, with a process-dependent trade-off between optimizing each parameter. These findings highlight that precise control of oxidant chemistry during ALD is essential for balancing flat band voltage stability with leakage suppression, and that multilayer-specific conduction models are critical for accurately predicting high electric field leakage characteristics in advanced SiC gate stacks.