Deciphering the Reaction Cycle Mechanisms and Key Reaction Factors of Monochlorosilane by Disproportionation of Dichlorosilane via Experiments and Density Functional Theory

Monochlorosilane (MCS) is an important silicon-based precursor for the fabrication of semiconductors and integrated circuits. The MCS production partly depends on the catalytic disproportionation of dichlorosilane (DCS). The DCS disproportionation has been critical yet challenging due to the involvement of multiple reversible reactions and other byproducts, often resulting in suboptimal yields of MCS. This investigation explored the sensitive conditions and key controlling factors affecting MCS yield in DCS disproportionation using gas chromatography-mass spectrometry (GC-MS). With increasing feed rates, the temperature requirement for DCS disproportionation gradually increased, and the sensitivity became significantly enhanced at high pressures. The optimal reaction conditions were 0.2 kg/h, 323.15 K, and 0.3 MPa. More importantly, density functional theory (DFT) calculations revealed the complete reaction cycle pathways of MCS generation. In these pathways, DCS dehydrogenation was identified as the rate-determining step, exhibiting the antagonistic effect with MCS disproportionation. The SiHCl₃-SiH₂Cl^- species, acting as the key intermediate, decomposed after promoting chlorine transfer to produce MCS and trichlorosilane (TCS). Furthermore, chloride ions, as byproducts, not only removed reactants but also acted as the chlorine source. This study provides significant theoretical guidance for the precise control of chlorosilane disproportionation reactions and the design of related catalysts.