Tunable Diode Laser Absorption Spectroscopy of the Pyrolysis of Methylsilazane
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Sun,
Y.W.
Bae
,
SPIECTROCOPY O' TM
E.A. Whittaker,
and B.
PYROLYSIB OF
Gallois
Department of Physics and Engineering Physics *Department of Materials Science and Engineering Stevens Institute of Technology, Hoboken, NJ 07030 Abstract 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 Tunable composition and the microstructure of the solid product. diode laser absorption spectroscopy provides a means to precisely monitor specific bond rupture in the precursor during pyrolysis. Nethylsilazane [CH3SiHNH],, a precursor to silicon-based ceramic thin films, was used to investigate the potential of this technique. Below the decomposition te.•perature, the intensity of the absorption line at 871.6±0.1 cm 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 , orders of magnitude narrower than would be observable The absorption line was using conventional infrared techniques. detectable over a pressure range from less than 1 Pa to 10 kPa.
introduction There has been an increasing interest in novel synthetic routes of thin films by the pyrolysis of organometallic precursors. Netalorganic chemical vapor deposition (MOCVD) provides a means of low-temperature processing of pure metals and alloys, metal and metalloid carbides, borides, nitrides, silicides, and related thin films which has both important technical and economical implications for structural and microelectronic device applications. is little Despite the demonstrated potential utilities, known of the chemical processes by which organometallic compounds This stems are converted to solid thin films upon pyrolysis. from the nature of the complex molecular structures that serve as precursors, and the even more complex and intractable structures Optimization that are intermediates in the pyrolysis process. of deposition conditions are, thus, usually made by experimentally varying the numerous process parameters until acceptable As the need to design novel organometaldeposits are obtained. precursors rises and control of composition and microstruclic ture of pyrolytic products becomes more demanding, studies aimed at understanding of the chemical processes which arise during the film formation pose a formidable challenge.
Mat. Res. Soc. Symp. Proc. Vol. 250. D1992 Materials Research Society
108
In an attempt to understand the chemical reactions in detail we have implemented high-resolution tunable diode laser spectroscopy (TDLAS) as a chemically selective, high sensitivity diagnostic. Individual diodes., commercially1 ailable with center frequencies between 300 cm and 3000 cm , are chosen to match the IR absorption spectrum of the species and vibrational transitions of interest. Measurement of t
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