Deposition and simultaneous etching of Si in the chemical vapor deposition (CVD) process: approach by the charged cluster model

Abstract

In the CVD process of selective epitaxial growth of silicon, it was reported that all the fine silicon particles, which had been deposited in the initial stage, etched away excepting one large silicon particle, which continued to grow. This phenomenon seems paradoxical since two opposite irreversible processes of deposition and etching take place simultaneously. The similar phenomenon of diamond deposition with simultaneous graphite etching, which takes place in the CVD diamond process, could be successfully explained by the charged cluster model, which assumes that the gas-phase nucleation takes place and the nuclei clusters are the deposition unit. The explanation was based on the fact that the C–H system has the retrograde solubility of carbon in the gas phase around the substrate temperature. Thermodynamic calculation of the Si–Cl–H system also indicates the retrograde solubility of silicon in the temperature range of interest. As in the case of the CVD diamond process, the assumption of the gas-phase nucleation and the deposition by the cluster unit could successfully explain the phenomenon of silicon deposition with its simultaneous etching in the CVD process.