Hydrogen-dominated plasma, due to silane depletion, for microcrystalline silicon deposition
- Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015 (Switzerland)
Plasma conditions for microcrystalline silicon deposition generally require a high flux of atomic hydrogen, relative to SiH{sub {alpha}=0{yields}3} radicals, on the growing film. The necessary dominant partial pressure of hydrogen in the plasma is conventionally obtained by hydrogen dilution of silane in the inlet flow. However, a hydrogen-dominated plasma environment can also be obtained due to plasma depletion of the silane in the gas mixture, even up to the limit of pure silane inlet flow, provided that the silane depletion is strong enough. At first sight, it may seem surprising that the composition of a strongly depleted pure silane plasma consists principally of molecular hydrogen, without significant contribution from the partial pressure of silane radicals. The aim here is to bring some physical insight by means of a zero-dimensional, analytical plasma chemistry model. The model is appropriate for uniform large-area showerhead reactors, as shown by comparison with a three-dimensional numerical simulations. The SiH{sub {alpha}} densities remain very low because of their rapid diffusion and surface reactivity, contributing to film growth which is the desired scenario for efficient silane utilization. Significant SiH{sub {alpha}} densities due to poor design of reactor and gas flow, on the other hand, would result in powder formation wasting silane. Conversely, hydrogen atoms are not deposited, but recombine on the film surface and reappear as molecular hydrogen in the plasma. Therefore, in the limit of extremely high silane depletion fraction (>99.9%), the silane density falls below the low SiH{sub {alpha}} densities, but only the H radical can eventually reach significant concentrations in the hydrogen-dominated plasma.
- OSTI ID:
- 22053750
- Journal Information:
- Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 28, Issue 4; Other Information: (c) 2010 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CRYSTAL GROWTH
DENSITY
DIFFUSION
DILUTION
GAS FLOW
HYDROGEN
MICROSTRUCTURE
NUMERICAL ANALYSIS
PARTIAL PRESSURE
PLASMA
POWDERS
REACTIVITY
SILANES
SILICON
SURFACE PROPERTIES
THIN FILMS
THREE-DIMENSIONAL CALCULATIONS