First-Principles Study of the Effect of Surface Heteroatoms on Silane Dissociation

With the rapid development of renewable energy and semiconductor industries, the preparation of high-quality polysilicon has received more and more attention. Chemical vapor deposition (CVD) is one of the most important methods for high-quality polysilicon fabrication. In this paper, density-functional theory (DFT) is employed to investigate the effect of surface heteroatoms on the growth of polysilicon prepared by CVD. The dissociation activation energy of silane and the migration energy barrier of surface silicon atoms are calculated on three types of silicon (111) surfaces, including a clean silicon surface, a silicon surface with oxygen, and a silicon surface with hydrogen. The calculation results reveal that the activation energy of silane dissociation on the clean silicon surface is 1.71 eV, higher than 1.04 eV on oxidized silicon surfaces and similar to 1.74 eV on silicon surfaces with hydrogen. Therefore, on a partially oxidized silicon substrate silicon deposition would preferentially occur in the oxidized region. On a hydrogenated silicon substrate, silicon deposition would uniformly take place over the entire surface. Furthermore, surface migration barriers of silicon atoms are calculated, with values of 0.27 0.24, and 0.05 eV on clean, oxidized, and hydrogenated surfaces, respectively. The lower migration barriers on the hydrogenated substrate indicate more uniform silicon deposition. Subsequently, this finding is confirmed by experimental evidence. This study provides a theoretical basis for the preparation of high-quality polysilicon and serves as valuable operational guidance for industry-level production of uniform and dense polysilicon rods.