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.