Simulation of correlated diffusion of Si and B in thermally grown SiO ₂

Simultaneous diffusion of Si and B in thermally grown SiO₂ is modeled taking into account the effect of SiO molecules generated at the Si/SiO₂ interface and diffusing into SiO₂ to enhance both Si and B diffusion. Based on the model, we simulated experimental profiles of coimplanted ³⁰Si and B in ²⁸SiO₂, which showed increasing diffusivities with decreasing distance from the interface. The simulation results show that the SiO diffusion is so slow that the SiO concentration at the near-surface region critically depends on the distance from the interface. In addition, the simulation explains that the diffusivities of both Si and B increase with longer annealing times because more SiO molecules arrive from the interface. Furthermore, we examined the effect of high-concentration B on the diffusivities of Si and B in SiO₂, both of which increase with higher B concentration. The experimental results were simulated assuming that the diffusivity of SiO, which enhances the diffusivities of Si and B, increases with higher B concentration. The present results indicate that Si and B diffusion in SiO₂ are correlated via SiO molecules; namely, the enhancement of SiO diffusion at high B concentrations also causes enhanced diffusion of both Si and B.