Published online by Cambridge University Press: 21 February 2011
Various laser-based deposition methods for preparation of silicon films have been reviewed briefly with emphasis on laser chemical vapor deposition (CVD). The main body of this paper is concerned with CO2 laser CVD of silane. This is interesting because the observed dependence of deposition rates on laser wavelengths indicates that gas-phase reactions are involved in deposition processes and therefore we can apply a powerful new diagnostic means, coherent anti-Stokes Raman spectroscopy (CARS), to examine gas-phase dynamics. From N2 CARS thermometry the CO2 laser beams were found to raise the temperature of the gas containing silane, when they were tuned to absorption lines of SiH4. Silane CARS spectra were characterized by a complicated profile with double peaks. We interpreted the shape of the spectra as arising from excitation of rotational levels following gas-phase reactions. Applying this interpretation, we can judge how SiH4 molecules are disturbed differently according to CO2 laser wavelengths and a distance from a substrate.