Coherent Anti-Stokes Raman Spectroscopic Study of CO2 Laser CVD of Silane

Abstract
Coherent anti-Stokes Raman spectroscopy (CARS) has been used to study gas phase processes involved in CO2 laser chemical vapor deposition of silane. SiH4 CARS spectrum exhibited a unique profile which was interpreted as arising from excitation of rotational levels following gas phase reactions. From N2 CARS thermometry, the CO2 laser beam was found to raise the temperature of the gas containing silane. Using the observed CARS results, we discuss why silicon films are deposited faster when the CO2 laser is tuned to absorption lines of silane.