THERMODYNAMIC STUDY, COMPOSITION, AND MICROSTRUCTURE OF LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITED SILICON DIOXIDE FILMS GROWN FROM TEOS N2O MIXTURES/

A calculational thermodynamic investigation of the chemical vapor depo sition of SiO2 films from TEOS/N2O mixtures has been performed based o n the minimization of the Gibbs energy of the Si-O-C-H-N system. The r esults illustrate the influence of temperature, pressure, and initial gas composition on the formation of stable phases. SiO2 films have bee n grown in a conventional horizontal low-pressure chemical vapor depos ition reactor at 983 and 1093 K and pressure 0.3 Torr. X-ray photoelec tron spectroscopy measurements have shown that the deposited films con tained carbon impurities with concentration decreasing with the increa se of the N2O/TEOS flow ratio, in qualitative agreement with the therm odynamic calculations. X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy measurements have shown that the O/Si rat io in the films was less than 2 and that it was approaching this value for high N2O/TEOS flows. Atomic force microscopy measurements have sh own that the films exhibited a granular morphology with grain size inc reasing with the deposition temperature and the N2O/TEOS flow ratio. T he analysis of Fourier transform infrared spectra taken on the films h as shown that the absorption near 1080 cm(-1) was due to the presence of more than one oscillator, the positioning of which was related to v ariations in the O/Si ratio, the interatomic distances, and the bond a ngles in the films.