Graphite chuck having a hydrogen impervious outer coating layer
First Claim
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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Accused Products
Abstract
The present invention is directed to a method for making substantially carbon-free polycrystalline silicon which comprises pyrolyzing a gaseous silicon compound on a heated starter filament 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 and form methane which decomposes as carbon on the deposited polycrystalline silicon.
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Citations
22 Claims
- 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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14. A method for making substantially carbon-free polycrystalline silicon by pyrolyzing a gaseous silicon compound on a heated starter filament mounted inside a reactor vessel on an electrode which supplies current to heat the starter filament, the 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, the method comprising:
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providing a graphite chuck having a hydrogen impervious outer coating layer; mounting the coated chuck onto an electrode of a polycrystalline silicon reactor vessel such that the chuck supports a starter filament that consists essentially of silicon, tungsten, or tantalum, and passing electrical current through the electrode, chuck and starter filament in the presence of a gaseous silicon compound, the hydrogen impervious coating preventing by-product hydrogen inside the vessel from reacting with the graphite to form methane which would decompose as carbon on polycrystalline silicon being deposited on the starter filament. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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Specification