Revealing the role of Si vacancies and interfaces in SiHCl ₃ dissociation applied in polysilicon

In the production of polysilicon, the various orientations of silicon crystal planes lead to Si vacancy and interface formation. However, the impact of these defects on the reduction of SiHCl₃ to Si is unclear. In this work, we demonstrated that Si vacancies and interfaces significantly improve the silicon deposition rate while inhibiting the formation of the by-product SiCl₄ through density functional theory calculations. Specifically, Si vacancies alter the charge distribution on the Si (111) surface, leading to an increased concentration of charges on the low-coordination Si atoms and placing Si vacancies in an electron-deficient state. In addition, Si vacancies induce charge transfer between the surface and subsurface Si atoms, which directly influences the adsorption and activation of reactive species on active sites. These findings show that the Si (111)-V surface containing Si vacancies exhibits the highest activity and selectivity for SiHCl₃ reduction to Si.