The Sensitivity of CVD Calculations to Physical Property Values

Abstract

A mathematical model that describes chemical vapor deposition in an impinging jet reactor has been used to assess the sensitivity of theoretical predictions to physical property values for intermediate species. Uncertainties in thermochemical data for a species have greatest impact on predicted deposition rates when the composition level of that species near the surface is comparable to the local compositions of the reactants. Under these circumstances, relatively small changes in the values of thermodynamic quantities used for the species can produce significant differences in deposition rates calculated under equilibrium conditions. Also, with the modified property values, different values of the kinetic parameters may be required to fit available experimental data, and this can lead to different interpretations of the rate-limiting steps in the process. Quantitative information for chemical vapor deposition of boron from boron trichloride and hydrogen is presented.

Chemical Vapor Deposition of Silicon from Disilane under Reduced Pressure in a Circular Impinging Jet Reactor: Simulation and Experiments

“…Nevertheless, an approximation such as the following one can be used when a small range of pressure is investigated kj = A3PBiT c~ exp (-Eaj/RT) [14] and for the corresponding reverse reaction k_~ = k/Kq [15] where A t and E~j are supposed to be constant, but differ from the classical A-factor and activation energy, the latter being defined as -R 0 in k/O(1/T). The uncertainty on the kinetic constants results from the complexity of the mechanism.…”

“…Accordingly, the classical A-factor as well as the activation energy of the Arrhenius expression of a reaction vary with both pressure and temperature. Nevertheless, an approximation such as the following one can be used when a small range of pressure is investigated kj = A3PBiT c~ exp (-Eaj/RT) [14] and for the corresponding reverse reaction k_~ = k/Kq [15] where A t and E~j are supposed to be constant, but differ from the classical A-factor and activation energy, the latter being defined as -R 0 in k/O(1/T). The corresponding parameters for the forward reactions are listed in Table II.…”