Thermodynamic Assessment of the Possibility of the Deposition of Silicon Borides from Their Halogenides

Abstract

The results of the predictive calculation of thermodynamic properties (enthalpy, entropy, and heat capacity) of boron silicide required for a thermodynamic analysis of the Si–B–Cl–H system performed with the help of the TERRA software complex are presented. Cases of the formation of condensed phases SiB₄ and SiB₆ in the reaction mixture are considered. To evaluate process parameters (temperature, pressure, and ratio of initial reagents) of deposition from the gas phase of silicon borides, thermodynamic calculations of the Si B–Cl–H system formed by SiCl₄, BCl₃, and H₂ for a temperature range of 1000–2200 K and pressure range of 0.00001–0.1 MPa are performed. It is shown that the thermodynamic stability of higher chlorides in the Si–B–Cl system drops with a decrease in pressure and the fraction of lower chlorides increases; i.e., initial silicon and boron chlorides destruct. However, no condensed phases SiB₄ and SiB₆ is formed, because their formation requires the introduction of hydrogen. It is determined that, varying the parameters of chemical deposition from the gas phase, it is possible to fabricate both single-phase and multiphase coatings. The results found in this study are of scientific and practical interest for developers of various production processes (gas-phase, liquid-phase, etc.) of silicon borides.