Film quality in relation to deposition conditions of {ital a}-SI:H films deposited by the {open_quote}{open_quote}hot wire{close_quote}{close_quote} method using highly diluted silane
- National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)
- Joint Institute for Laboratory Astrophysics, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)
The deposition parameter space has been extensively explored using the hot wire technique with 1{percent} SiH{sub 4} in He as a source gas. To achieve reasonable deposition rates despite the high dilution, the filament was positioned at 1{endash}2 cm from the substrate. This short distance introduced a large nonuniformity across the substrate in deposition rate as well as in film properties. These spatial variations were used to analyze which factors in the deposition determine film quality. Radiation from the filament as well as deposition rate cannot explain the large variation in film properties, leaving gas-phase reactions of Si and H from the hot filament as the primary cause. It is clear that radicals evaporated from the filament must undergo gas-phase reactions with SiH{sub 4} before deposition in order to produce high-quality material. Thus, conditions such as increasing the chamber pressure or going to a heavier carrier gas increase the fraction of radicals that can react before reaching the substrate and, therefore, improve the film quality. However, such conditions also enhance multiple radical reactions before such radicals reach the substrate and this can have a negative effect on film quality: this is attributed to gas-phase nucleation with incorporation of conglomerates. The gas-phase chemistry is quite different from that of plasma-enhanced decomposition in that no disilane or trisilane is formed in significant quantities. This, and the dependence on pressure, indicates that the pathway for formation of these heavier particles is radical{endash}radical reactions. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- DOE Contract Number:
- AC36-83CH10093
- OSTI ID:
- 283347
- Journal Information:
- Journal of Applied Physics, Vol. 79, Issue 9; Other Information: PBD: May 1996
- Country of Publication:
- United States
- Language:
- English
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