Mechanistic feature-scale profile simulation of SiO2 low-pressure chemicalvapor deposition by tetraethoxysilane pyrolysis

Simulation of chemical vapor deposition in submicron features typical of se miconductor devices has been facilitated by extending the EVOLVE [T. S. Gal e, T. H. Gandy, and G. B. Raupp, J. Vac. Sci. Technol. A 9, 524 (1991)] thi n film etch and deposition simulation code to use thermal reaction mechanis ms expressed in the Chemkin format. This allows consistent coupling between EVOLVE and reactor simulation codes that use Chemkin. In an application of a reactor-scale simulation code providing surface fluxes to a feature-scal e simulation code, a proposed reaction mechanism for tetraethoxysilane [Si( OC2H5)(4)] pyrolysis to deposit SiO2, which had been applied successfully t o reactor-scale simulation, does not correctly predict the low step coverag e over trenches observed under short reactor residence time conditions; One apparent discrepancy between the mechanism and profile-evolution observati ons is a reduced degree of sensitivity of the deposition rate to the presen ce of reaction products, i.e., the by-product inhibition effect is underpre dicted. The cause of the Proposed mechanism's insensitivity to by-product i nhibition is investigated with the combined reactor and topography simulato rs. This is done first by manipulating the surface-to-volume ratio of a sim ulated reactor and second by adjusting parameters in the proposed mechanism such as the calculated free energies of proposed surface species. The conc lusion is that simply calibrating mechanism parameters to enhance the by-pr oduct inhibition can improve the fit to profile evolution data; however, th e agreement between with reactor-scale data and simulations decreases. Addi tional surface reaction channels seem to be required to simultaneously repr oduce experimental reactor-scale growth rates and feature-scale step covera ges. (C) 2000 American Vacuum Society. [S0734-211X(00)09201-5].