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research article

Hydrogen-dominated plasma, due to silane depletion, for microcrystalline silicon deposition

Howling, A. A.  
•
Sobbia, R.  
•
Hollenstein, Ch.  
2010
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Plasma conditions for microcrystalline silicon deposition generally require a high flux of atomic hydrogen, relative to SiH alpha=0 -> 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 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 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 si lane depletion fraction (>99.9%), the silane density falls below the low SiH alpha densities, but only the H radical can eventually reach significant concentrations in the hydrogen-dominated plasma. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3328824]

  • Details
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Type
research article
DOI
10.1116/1.3328824
Web of Science ID

WOS:000280479700093

Author(s)
Howling, A. A.  
Sobbia, R.  
Hollenstein, Ch.  
Date Issued

2010

Publisher

American Vacuum Society

Published in
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
Volume

28

Issue

4

Start page

989

Subjects

Electron-Cyclotron-Resonance

•

Area Showerhead Reactors

•

A-Si-H

•

Discharges

•

Uniformity

•

Chemistry

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
CRPP  
SPC  
Available on Infoscience
March 9, 2011
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/65209
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