Kinetic Modelling of the Deposition of SiC from Methyltrichlorosilane
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KINETIC MODELLING OF THE DEPOSITION OF SiC FROM METHYLTRICHLOROSILANE Stratis V. Sotirchos and George D. Papasouliotis Department of Chemical Engineering University of Rochester Rochester, NY 14627 ABSTRACT A kinetic model is presented for the deposition of silicon carbide through decomposition of methyltrichlorosilane (MTS). The developed model includes gas phase (homogeneous) reactions that lead to formation of deposition precursors and surface (heterogeneous) reactions that lead or can lead to deposition of silicon carbide, silicon, and carbon. The kinetic model is incorporated in a transport and reaction model for a tubular hot-wall reactor, and the overall reactor model is used to obtain some preliminary results on the effects of pressure and distance in the reactor on the rate of deposition and the composition of the deposit. The results show that the model can reproduce most of the experimental observations of the literature. INTRODUCTION Because of the various chemical, mechanical, and electronic properties of silicon carbide, its study has been a subject of considerable interest. A large number of experimental studies has been conducted on the deposition of SiC films through decomposition of various precursors [1]. Deposition from methyltrichlorosilane (CH 3 SiCI 3 ) has been one of the most frequently studied and used routes for SiC deposition. However, the results of the various experimental investigations vary widely from one research group to another, indicating that the details of the deposition process (and hence, the deposition rate) are a strong function of the experimental conditions and of the experimental arrangement (reactor configuration) used to carry out the deposition process [1-3]. Our own experimental investigation of SiC deposition from MTS showed that the deposition rate depends on the distance in the reactor, suggesting, among other things, that the decomposition products may affect the deposition process and its rate [22]. Subsequent studies revealed a strongly inhibitory effect of HCl on the deposition process, in agreement with results obtained by other investigators [3]. Needless to say, any kinetic model for the deposition of silicon carbide through the decomposition of MTS should account for these experimental trends, apart from the observed dependence of the deposition rate on temperature, pressure, and flow rate. Presently, most of the published kinetic modelling studies for SiC deposition are for codeposition processes, the precursors being mixtures of silanes and hydrocarbons. In most cases, more effort was put into modelling the transport phenomena in the CVD reactor than the chemistry of the reacting system under consideration [5,6]. One of the most complete kinetic modelling studies was presented by Allendorf and Kee [4], who studied the deposition of silicon carbide from silane and propane. They combined detailed kinetic mechanisms for the decomposition of the two precursor compounds, and incorporated the homogeneous chemistry into the reaction and transport model of a ro
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