Low pressure chemical vapor deposition from TEOS-NH3 mixtures: thermochemical study of the process considering kinetic data

A calculational thermodynamic investigation of the chemical vapor deposition (CVD) of SiO2 films from TEOS/ NH-i mixtures has been performed, by minimizing the Gibbs energy of the C-H-N-O-Si chemical system. Calculations are based on an upgraded thermodynamic data bank which includes silicon containing complex gaseous compounds. The obtained results illustrate the influence of temperature, of pressure, and of initial gas composition on the formation of stable phases. Partial equilibrium calculations were also performed, in order to investigate the predominant mechanisms for deposition. These calculations have been conducted (a) by excluding the solid phases from the calculations, and (b) by assuming a partial striping and elimination of the ethoxy ligands in the gas phase before reaching the growing surface. Finally, the supersaturation of the gas phase relative to silicon dioxide and the corresponding driving force for the deposition have been evaluated in different processing conditions. A direct relation between driving force and the growth rate of the deposits has thus been evidenced. The aim of this research is to contribute to the definition of optimum conditions for the processing of materials which can be used as dielectrics in integrated circuits, and as waveguides in optoelectronics