The The Sihcl <sub> 3 </ Sub> / H <sub> 2 </ Sub> Epitaxial Growth Of Single Crystal Silicon Reaction Mechanism Theoretical Study

Silicon vapor-phase epitaxial growth with SihCl3/H2 system on the silicon substrate is the most important technologies under atmospheric pressure for fabricating monocrystal 1 ine si 1 icon. In this paper, the mechanisms of this reaction system were investigated theoretically according to the transition state theory. The quantum chemistry was combined with molecular reaction dynamics and the density function theory was used to explore them systemically for the first time.According to the productions which had been explored in the experiment and the Chemical process for silicon epitaxial growth in a SiHCl3i/H2 system Hitoshi Habuka etc. promoted, we projected the possible reaction paths of this system that occur in the gas phase and on the substrate surface.1. The geometries of all reactants, transition states and productions have been optimized with Gaussian 98 program at B3LYP/6-311G* level. The active energy of each reaction channel was calculated.2. Analysis the mechanism of the reaction in the gas phase, the results show that the path d is the main reaction path in the gas phase. We investigated the reaction that occurs in the gas phase and on the substrate surface about its production SiCl2 further and found that the silicon was not been formed in the gas phase, but only on the substrate surface.3. Analysis the mechanism of the reaction on the substrate surface, it is found that the active energy of SiHCi< decomposition is very low and that of reaction between the decomposed production and the hydrogen is decreased with the attendant of silicon substrate. So we concluded that the substrate has the catalysis in the reaction process. In calculation, we used the Si cluster to simulate the substrate surface and concluded that the larger the cluster simulated the substrate surface, namely, the more similar to the true surface, the easier the reaction between the hydrogen and the productions which been formed after the decomposition on the substrate.4. In all, the silicon was not been formed in the gas phase, but only on the substrate surface in the SiIICl3/ll2 reaction system. This is in agreement with the experiment result. The direct decomposition of SillCl3 on the silicon substrate surface is the main path of this reaction system.5. Analysis the imaginary vibration mode of all transition states in order to test the transition states. IRC (intrinsic reaction coordinate) was made for confirming the existence of the transition states, further.6. The rate constant was calculated by TST over a wide temperature range of 600-1450K. Seen from the results, the rate constant is increasing with thetemperature increasing and the reaction of the decomposition is finished quickly, while the reaction with H2 is slower, so it is confirmed the determinable rate step of reaction.In this paper, we gave the good explanation for the experiment of the monocrystalline silicon vapor-phase epitaxial growth and the microcosmic mechanism of the reactions theoretically. It will provide the dynamical information for the experimental workers to design the experimental techniques and improve the work efficiency.