MBMS studies of gas-phase kinetics in diamond chemical vapor deposition
- Stanford Univ., CA (United States)
- IBM San Jose, CA (United States)
- Sandia National Labs., Livermore, CA (United States); and others
A molecular beam mass spectrometer system (MBMS) has been used to determine the near-surface gaseous composition involved in the low pressure chemical vapor deposition of diamond. With this system, radical and stable species can be detected with a sensitivity better than 10 ppm. Threshold ionization techniques have been employed to distinguish between radical species in the deposition environment from radical species generated by parent molecule cracking. An extensive calibration procedure was used to enable the quantitative determination of H-atom and CH{sub 3} radical mole fractions. Using the MBMS system, the gaseous composition involved in LPCVD of diamond has been measured for a wide variety of deposition conditions, including hot-filament gas activation, microwave-plasma gas activation, and a variety of precursor feed mixtures (ex: CH{sub 4}/H{sub 2}, C{sub 2}H{sub 2}/H{sub 2}). For microwave-plasma activation (MPCVD), the radical concentrations (H-atom and CH{sub 3} radicals) are independent of the identity of the precursor feed gas provided the input carbon mole fraction is constant. However, in hot-filament diamond deposition (HFCVD), the atomic hydrogen concentration decreased by an order of magnitude as the mole fraction of carbon in the precursor mixture is increased to .07; this sharp reduction has been attributed to filament poisoning of the catalytic tungsten surface via hydrocarbon deposition. Additionally, the authors find that the H-atom concentration is independent of the substrate temperature for both hot-filament and microwave plasma deposition; radial H-atom diffusion is invoked to explain this observation.
- Research Organization:
- National Renewable Energy Lab., Golden, CO (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 110846
- Report Number(s):
- NREL/CP--433-7748; CONF-9410343--; ON: DE95004052
- Country of Publication:
- United States
- Language:
- English
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