Impact of Oxygen Plasma Pre‐Treatment on Thermal Oxidation and Reliability of SiO ₂ on 4H‐SiC

ABSTRACT Although thermal oxidation represents an essential method for growing high‐quality SiO ₂ on 4H‐SiC, it suffers from low growth rates and high thermal budgets, limiting its industrial relevance compared to deposited oxides such as TEOS‐based oxides. In this study, we investigate how oxygen plasma pre‐treatment affects the subsequent thermal oxidation and electrical performance of SiO ₂ layers on 4H‐SiC. A substantial enhancement in oxide growth rate (up to 84%) is observed, which we attribute to plasma‐induced surface modification that facilitates oxygen diffusion. However, this acceleration comes at the cost of reduced dielectric breakdown strength (∼18% lower) and a broadened transition region at the interface. Electrical measurements indicate that leakage is governed by Schottky and Poole‐Frenkel conduction mechanisms. Capacitance–voltage and conductance‐voltage analysis reveal lower interface state density (D _it ) for samples with oxygen plasma pre‐treatment, indicating plasma‐induced modification of the SiO ₂ /SiC interfacial defect structure. These findings suggest that plasma pre‐treatment introduces structural damage that promotes oxidation but degrades dielectric reliability. This work highlights both the potential and limitations of plasma‐enhanced oxidation for SiC‐based dielectrics and motivates further studies to optimise process parameters and mitigate reliability trade‐offs.