Revealing the Chemical Reaction Properties of a SiHCl₃ Pyrolysis System by the ReaxFF Molecular Dynamics Method

The pyrolysis kinetics of SiHCl₃ and its reaction mechanism are essential for the chemical vapor deposition process in polysilicon industries. However, due to the high temperature and lack of in situ experimental detection technology, it is difficult to carry out experimental research on the pyrolysis kinetics of SiHCl₃. In this work, reactive force field molecular dynamics simulations of SiHCl₃ pyrolysis were performed to investigate the effect of temperature on the pyrolysis kinetics of SiHCl₃ at the atomistic scale in a wide temperature range (1000-2000 K). The lumped Si clusters containing more than five Si atoms tended to appear at the later period of the reaction under a temperature lower than 1300 K, some of which even possessed polycyclic structures; nevertheless, small ones with less than two Si atoms such as SiHCl₂ and HCl tended to emerge under a high temperature. The changes of partial energy terms with time evolution under various temperatures were proved to be rooted in the distribution of intermediates based on the momentary simulation period. In general, the reaction network at a low temperature was more complicated than that at a high temperature, resulting from the fact that more chemical events and intermediates came into existence, and the maximum number of Si atoms in one single molecule/radical was observed under a low temperature than that under a high temperature. As to the variation of SiHCl₃ with the progress of the reaction, the linear fitting tendency disappeared under the temperature above 1300 K, which changed in fluctuation with the further elevation of temperature, elucidating the fact that SiHCl₃ can act as a product and not just as a reactant to participate in elementary chemical events frequently.