On the Mechanism of Homogeneous Decomposition of the Chlorinated Silanes. Chain Reactions Propagated by Divalent Silicon Species

Abstract

A mechanism for the homogeneous gas-phase decomposition of SiHCl 3 , SiH 2 Cl 2 , and SiH 3 Cl in hydrogen is derived from the results of ab initio molecular-orbital studies. It consists of 39 reversible elementary reactions among 25 species, including pressure-dependent unimolecular decomposition of the chlorinated silanes and secondary chemistry due to reactions of SiH 2 , SiHCl, and SiCl 2 with one another and with the chlorinated silanes. Rate parameters in the mechanism have been calculated based on results of ab initio studies using transition-state theory and unimolecular rate theories. This allows us to construct a reasonably complete mechanism that provides qualitative explanations for several features of dichlorosilane decomposition that have been presented in the literature, including observations on the presence and concentrations of SiCl 2 , SiHCl, and Si atoms. Several chain reactions in which the chain carriers are divalent silicon species have been identified.

On the Mechanism of the Disproportionation of Chlorinated Silanes under the Influence of Lewis Bases

“…For each of the various possible homogeneous decompositions of chlorinated disilanes into silylenes and monosilanes, Swihart and Carr [29,30] found transition structures which resemble the transition structure shown in scheme I, figure a. Transition states possessing a similar geometry as scheme I, figure b were found only for the insertion reaction of SiH 2 but not for the insertion of SiHCl and SiCl 2 into Si±H or Si±Cl bonds.…”

“…Schlegel and coworker studied the decomposition of fluorinated or chlorinated monosilanes [22±27] as well as the decomposition of fluorinated disilanes [28]. The homogeneous decomposition of chlorinated disilanes was studied by Swihart and Carr [29,30]. Hay [31] and Nachtigall et al [32] studied the reliability of the density functional theory (DFT) for the description of the thermochemistry and of the reactions of Si±H and Si±H±Cl compounds.…”

Cluster Kinetics of Phase Transitions: Applications to Innovative Technologies

“…An accurate kinetic model for SiHCl 3 decomposition needs to be coupled with the above-described transport model for silicon epitaxy. There is considerable information available regarding intrinsic kinetic and thermochemical processes associated with gas phase (Swihart and Carr, 1998), surface chemistry (Walker et al, 1998), and reaction mechanism (Ho et al, 1985) of SiHCl 3 . The comprehensive model described in this work includes nucleation, crystal growth, condensation, and aggregation and can be coupled with intrinsic kinetic models available in the literature and can thus potentially be applied to model CVD processes.…”

High‐temperature kinetics of some Si‐ and Cl‐containing ceramic precursors

“…At temperatures 1500 ≤ T ≤ 3300 K and pressures 0.8 ≤ p ≤ 4.0 bar Cl-and Si-atoms were simultaneously measured together with H-absorptions at the L ␣ -line in mixtures of 0.5-5.0 ppm SiHCl 3 /Ar. In theoretical and experimental studies [14][15][16][17] …”