Kinetics of Chemical Vapor Deposition

A generalized mass transport model is developed for predicting the rate of deposition in chemical vapor deposition (CVD) systems. This combines the generalized method of obtaining equilibrium composition, with elemental flux balance expressions. This procedure avoids the usual problems encountered in calculating the rates in multicomponent systems, like writing overall reaction schemes. The dependence of multicomponent diffusivities on the fluxes is accounted in this model using an iterative procedure. The model developed is applied to the deposition of titanium carbide on cemented carbide tool bits from a gas mixture of titanium tetrachloride, toluene, and hydrogen. Experimental deposition rates were obtained using a thermogravimetric assembly. Mass transport controlled rates give an order of magnitude estimates of the observed rates.