Comparison of FTIR Transmission Spectra of Thermally and LPCVD SiO[sub 2] Films Grown by TEOS Pyrolysis

Dispersion analysis of Fourier transform infrared (FTIR) spectra taken on thermally grown films developed in dry oxygen and low pressure chemically vapor deposited (LPCVD) from tetraethylorthosilicate vapors was performed. LPCVD was carried out at temperatures of 635, 650, 710, and 820°C while thermally grown samples were prepared at 950, 1050, and 1150°C. The thickness of all films was approximately 100 nm. Transmission spectra within the range were analyzed using four Lorentzian oscillators located near 1060 (1), 1089 (2), 1165 (3), and the last two being much weaker than the first two, so the study was limited to oscillators 1 and 2. It was found that the increase of the temperature of growth implies a shift of central frequencies of both oscillators toward higher wavenumbers and the oscillator strength of 1 increases while that of 2 decreases. The damping coefficient, γ, of both oscillators initially increases and above 950°C decreases and the Gaussian width of central frequencies, δ, for 1 increases toward while that of 2, above 950°C, saturates near It was suggested that oscillators 1 and 2 correspond to different Si-O-Si bridges in which angles distribute in different ways. Bridges associated with oscillator 1 are located in the bulk of the films and those with oscillator 2 appear near interfaces and grain boundaries.