ReaxFF Molecular Dynamics Simulation and Experimental Validation of the Oxidation Mechanism of the C-Face of 6H-SiC Wafers under Different Hydroxyl Radical Concentrations

The oxidation behavior of the C-face of 6H-SiC wafers under varying hydroxyl radical ( • OH) concentrations was investigated through a combined approach of oxidation experiments and reactive force field molecular dynamics (ReaxFF-MD) simulations, aiming to provide theoretical and experimental support for the chemical mechanical polishing (CMP) and interface engineering optimization of 6H-SiC. The • OH concentrations generated under three distinct conditions (Electrochemical, Fenton, and Electro-Fenton reactions) were quantified, and oxidation experiments were performed on the C-face of 6H-SiC wafers. The resulting oxidation products were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Concurrently, to elucidate the oxidation mechanism of • OH on the C-face of 6H-SiC wafers, a ReaxFF-MD simulation was conducted on a 3 Å-roughened C-face model under • OH numbers of 90, 180, and 270. The experimental results show that • OH generation progressively increases across the Electrochemical, Fenton, and Electro-Fenton systems, leading to a gradual enhancement in the oxidation degree of the C-face of the 6H-SiC wafer. The surface oxidation layer evolves from sparse to dense, accompanied by a decrease in C content and an increase in O content, with the Electro-Fenton system exhibiting the most pronounced oxidation effect. The ReaxFF-MD results indicate that increasing the • OH concentration promotes continuous Si–C bond cleavage and progressive accumulation of Si–O bonds and O–Si–O structures, together with increased oxidation-layer thickness and density, C–C enrichment, and the formation of carbon-containing oxides. The rough surface further accelerates oxidation by providing additional active sites and synergistically interacting with • OH. The agreement between experiments and simulations confirms that higher • OH levels lead to more pronounced oxidation and clarifies the synergistic oxidation mechanism of surface roughness and • OH on the C-face of 6H-SiC.