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Graphite chuck having a hydrogen impervious outer coating layer

  • US 5,284,640 A
  • Filed: 09/17/1992
  • Issued: 02/08/1994
  • Est. Priority Date: 12/26/1989
  • Status: Expired due to Term
First Claim
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1. A method for making substantially carbon-free polycrystalline silicon which comprises pyrolyzing a gaseous silicon compound on a heated starter filament that consists essentially of silicon, tungsten, or tantalum, and that is mounted on a graphite chuck, said heated starter filament being maintained at a temperature sufficient to effect decomposition of the gaseous silicon compound to form polycrystalline silicon which is deposited thereon and by-product hydrogen, wherein the said graphite chuck is provided with a hydrogen impervious outer coating layer to prevent the by-product hydrogen from reacting with the graphite to form methane which decomposes as carbon on the deposited polycrystalline silicon.

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