Experimental study of atmospheric pressure chemical vapor deposition of silicon carbide from methyltrichlorosilane
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Experimental study of atmospheric pressure chemical vapor deposition of silicon carbide from methyltrichlorosilane George D. Papasouliotisa) Department of Chemical Engineering, University of Rochester, Rochester, New York 14627
Stratis V. Sotirchosb) Department of Chemical Engineering, University of Rochester, Rochester, New York 14627 and Institute of Chemical Engineering and High Temperature Chemical Processes, P.O. Box 1414, 26500 Patras, GREECE (Received 2 November 1998; accepted 29 April 1999)
A comprehensive study of the chemical vapor deposition of SiC from methyltrichlorosilane at atmospheric pressure was conducted in this study; its main objectives were to identify the range of operating parameters in which stoichiometric SiC could be deposited and the generation of reliable kinetic data that could be used for the design of atmospheric pressure processes of chemical vapor deposition or chemical vapor infiltration of SiC. Deposition experiments were conducted in a hot-wall, cylindrical reactor at temperature ranging from 1273 to 573 K on flat graphite substrates or thin molybdenum wires aligned with the axis of the reactor. The obtained results showed that the deposition rate and the deposit stoichiometry varied markedly with the distance from the entrance of the reactor. The deposition rate exhibited, depending on the reaction temperature, one or two pronounced maxima before the beginning of the isothermal zone of the reaction, whereas the deposit stoichiometry showed an abrupt transition from almost silicon to stoichiometric silicon carbide after the first maximum. Experiments with HCl added in the feed showed that the presence of HCl could cause complete suppression of the deposition of silicon and lead to smoother variation of the SiC deposition rate with the residence time in the reactor. It is believed that this effect could be exploited to improve the uniformity of SiC deposition in chemical vapor deposition reactors or in the interior of porous preforms.
I. INTRODUCTION
The very good mechanical, physical, and chemical (corrosion resistance, chemical stability) properties1,2 of silicon carbide have led to extensive research efforts on both its potential applications and manufacturing routes. Chemical vapor deposition (CVD) of SiC films has been conducted through the decomposition of various organic or organometallic compounds in various types of reactors, including fixed- and fluidized-bed reactor arrangements.3 Methyltrichlorosilane (MTS, CH3SiCl3) is the most commonly used single-source deposition precursor, not only for the stoichiometric presence of silicon and carbon in its molecule but for the good quality of the resulting films as well. Silicon carbide films show up in a variety of applications,4–8 such as structural components for engines and turbines, protective coatings and fission product containment vessels,9 and matrix material in fiber-reinforced ceramic matrix composites (CMCs). a)
Present address: Novellus Systems, Inc., 25 Corporate D
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