Defect Formation and Electrical Transformation in SiO₂ Thin Films via Ti-Induced Interdiffusion

Metal diffusion during thermal annealing and its impact on the electrical properties of insulating films is a critical issue in semiconductor processing. In this study, we investigate the thermally induced electrical and chemical transformations of SiO₂ thin films with thicknesses ranging from 50 nm to 300 nm, initiated at the Ti/SiO₂ interface. High-temperature annealing between 500 °C and 600 °C, depending on the SiO₂ deposition method, facilitates the interdiffusion of Ti, Si, and O species across the interface. As diffusion progresses, the capacitance of the Ti/SiO₂/p⁺-Si structure increases, while the breakdown voltage decreases. Continued annealing ultimately leads to a transition of SiO₂ into a highly conductive state when the film thickness falls below the diffusion length. The vulnerability to thermal degradation strongly depends on the fabrication method of the SiO₂ thin film. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal the formation of reduced Ti and Si species, which generate interfacial states and extended hole traps within the SiO₂ layer. These findings provide fundamental insights into the mechanisms underlying the electrical transformation of SiO₂ and offer guidance for the design of oxide-based charge-trap materials in next-generation memory technologies.