No abstract

Amorphous silicon oxynitride films were prepared by chemical vapor deposition on silicon (100) substrates from gas mixtures of methylsilazane, [CH7SiHNH], ammonia, and nitrous oxide in the temperature range of 650 to 825°C at a pressure of 760 Torr. Oxynitride films with a wide range of compositions were formed by varying the concentration of nitrous oxide in the gas mixture. A stable SiON9:H phase constituted the main chemical structure in the films. Controllable deposition conditions were found which permit tailoring of the refractive index between 1.54 and 1.85, suggesting possible application in gradient index optics.

By applying both low-frequency wavelength modulation and high-frequency phase modulation to a laser diode, we develop a sensitive, high-bandwidth chemical diagnostic tool that is applicable to a variety of gas-phase processing environments. Specific chemical species are identified and monitored through their infrared absorption spectra, and the modulation methods allow for sensitive detection that is free of window and other reflection-driven interference fringes. Absorbance limits of 5.3 x 10(-8) and 1.9 x 10(-7) are obtained for an AlGaAs diode laser and a lead-salt diode laser, respectively. We discuss applications to plasma etching and chemical vapor deposition.

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.