A first-principles investigation into the adsorption behavior and deposition mechanism of boron-containing gases on Si(100) surfaces during chemical vapor deposition

Abstract

Polysilicon serves as a primary raw material in the production of solar cells and semiconductors. However, its impurity content, particularly boron, poses significant challenges during the chemical vapor deposition (CVD) process. Therefore, it is essential to investigate the behavior of boron impurities during CVD. In this study, we conducted first-principles calculations to explore the adsorption behavior and deposition mechanism of boron-containing gases (BCl3, BHCl2, B2H6) on the Si(100) surface. We considered different adsorption sites and performed a systematic analysis of various adsorption systems' adsorption energy, charge transfer, and electronic properties. Our findings indicate that BCl3, BHCl2, and B2H6 molecules undergo dissociative chemisorption at specific adsorption sites. Moreover, charge transfer analysis confirms that each of these adsorbed molecules functions as an electron acceptor. Subsequent analyses, including total charge density (TCD), charge density difference (CDD), total density of states (TDOS), and projected density of states (PDOS), collectively underscore the robust electronic interactions between the gaseous molecules and the Si(100) surface. Through the computation of transition states and energy barriers across three potential reaction pathways, we identify a predominant sequence: BCl3→BCl2+Cl→BCl+Cl→B+Cl, that governs boron impurity formation on the Si(100) surface during CVD. Our work elucidates the underlying microscopic mechanisms of boron-containing gas adsorption and deposition in the CVD context.