Tunable Diode Laser Absorption Spectroscopy of the Pyrolysis of Methylsilazane

An understanding of the chemical processes occurring in the gas phase during metalorganic chemical vapor deposition is needed to design novel precursors and for the subsequent control of the composition and the microstructure of the solid product. Tunable diode laser absorption spectroscopy provides a means to precisely monitor specific bond rupture in the precursor during pyrolysis. Methylsilazane [CH3SiHNH]n,, a precursor to silicon-based ceramic thin films, was used to investigate the potential of this technique. Below the decomposition temperature, the intensity of the absorption line at 871.6±0.1 cm−1 corresponding to one of the harmonics from Si-CH3, increased linearly with the vapor pressure of methylsilazane up to 800 Pa and then decreased exponentially. The typical linewidths of the absorption line was approximately 0.006 cm−;1, orders of magnitude narrower than would be observable using conventional infrared techniques. The absorption line was detectable over a pressure range from less than 1 Pa to 10 kPa.