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ISSN Imprimer: 2151-4798
ISSN En ligne: 2151-562X
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SIMULATION OF A CHEMICAL VAPOR DEPOSITION: MOBILE AND IMMOBILE ZONES AND HOMOGENEOUS LAYERS
RÉSUMÉ
This paper describes how we model chemical vapor deposition for metallic bipolar plates and optimization to deposit a homogeneous layer. Constraint on the deposition process are very low pressure (nearly vacuum) and low temperature (∼400 K). These constraints need catalytic process, and our apparatus deals with a plasma source and precursor gases [see Dobkin, M. K. and Zuraw, D. M. (Principles of Chemical Vapor Deposition, 1st ed., Springer, NY, 2003)]. Such a plasma has the advantage of accelerating the vaporization process [see Lieberman, M. A. and Lichtenberg, A. J. (Principle of Plasma Discharges and Materials Processing, 2st ed., Wiley-Interscience, Hoboken, NJ, 2005)], and of bringing the solid materials to a gaseous phase. Nevertheless, there are also some drawbacks, in that retardation and adsorption processes can hinder the direct transport to the target [see Lieberman and Lichtenberg (2005)]. Here, we present a mesoscopic model, which reflects the retardation, transport, and reaction of the gaseous species through homogeneous media in the chamber. The models include immobile gaseous phases, where the transport of the mobile gaseous species is hindered. Furthermore, the models include the conservation of mass and the porous media are in accordance with Darcy's law, which is an assumption for the flow processes of the gaseous phase. The transport through the stationary and ionized plasma field is treated as a diffusion-dominated flow with mobile and immobile zones [see Gobbert, M. K. and Ringhofer, C. A. (SIAM J. Appl. Math., vol. 58, pp. 737-752,1998) and Lieberman and Lichtenberg (2005)], where the metallic deposit and the gas chamber look like porous media [Rouch, H., (Proc. of the COMSOL Users Conf., Paris, pp. 1-7, 2006) and Cao, G. Z., Brinkman, H., Meijerink, J., DeVries, K. J., and Burggraaf A. J. (J. Mater. Chem.), vol. 3, no. 12, pp. 1307-1311, 1993)]. We choose porous ceramic membranes and gas catalysts like argon (Ar), (Cao et al., 1993) and apply our experience in simulating gaseous flow and modeling the penetration of such porous media [see Jin, S. and Wang, X. (J. Comput. Phys., vol. 179, no. 2, pp. 557-577, 2002)]. Numerical methods are developed to solve such multiscale and multiphase models. We have taken into account combined spatial discretization methods, based on finite volume methods and analytical test functions. Although implicit in time, discretized parts are solved with Runge-Kutta methods and iterative solvers coupled with mobile and immobile equation parts. The numerical experiments validate the modified discretization methods respecting their higher order results and their efficiencies. In real-life simulations of physical experiments, we discuss the validation of our model and the assumed deposition rates.