Energy efficient method for growing polycrystalline silicon
AssigneeAdvanced Silicon Materials LLC
InventorsLyle C. Winterton, John P. Hill
Life of this patent
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Abstract
Polysilicon dendrites are grown by depositing silicon on a polysilicon rod or other substrate. Surface temperature is increased to a temperature at which needle-like dendrites develop due to the deposition of silicon from silicon-containing molecules in the surrounding reactor atmosphere. Thereafter, the surface temperature is gradually reduced so that silicon that deposits on the needle-like dendrites causes the dendrites to grow and assume a generally flared shape.
Claims39
A method for producing polycrystalline silicon comprising:
- heating a surface of a substrate;
- exposing the heated surface to an atmosphere that contains at least one silicon-containing compound under conditions that cause a silicon-containing compound in the atmosphere to decompose and deposit needle-like dendrites of silicon on the surface;
- and
- gradually reducing the surface temperature of the needle-like dendrites while exposing the needle-like dendrites to an atmosphere that contains at least one silicon-containing compound such that silicon deposits on the surfaces of the needle-like dendrites and forms multiple larger dendrites.
A method for producing polycrystalline silicon comprising:
- providing an elongated polycrystalline silicon core rod;
- exposing the surface of the core rod to an atmosphere that contains at least one silicon-containing compound while maintaining the surface temperature of the core rod below the melting point of silicon and sufficiently high that a silicon-containing compound in the atmosphere pyrolytically decomposes and deposits silicon on the surface to provide a rod encrusted with needle-like dendritic formations;
- and
- gradually reducing the surface temperature of the rod encrusted with needle-like dendritic formations while continuing to expose the needle-like dendritic formations to an atmosphere that contains at least one silicon-containing compound such that silicon deposits on the needle-like dendritic formations and forms a rod encrusted with multiple larger silicon dendrites.
A method for producing polycrystalline silicon comprising:
- providing an elongated polycrystalline silicon filament;
- depositing a generally cylindrical layer of polycrystalline silicon on the filament to form a core rod;
- exposing the surface of the core rod to an atmosphere that comprises silane (SiH4) while maintaining the rod surface a temperature in a range such that the temperature is at least 875° C. and is below the melting point of silicon, during which silane in the gas pyrolytically decomposes and deposits silicon on the surface in needle-like dendritic formations and produces a rod encrusted with needle-like dendrites;
- and
- gradually reducing the surface temperature of the rod encrusted with needle-like dendrites while exposing the needle-like dendrites to an atmosphere that contains silane, the surface temperature being reduced at a rate such that silicon deposits on the needle-like dendritic formations and forms multiple larger silicon dendrites distributed over substantially the entire heated surface of the rod encrusted with needle-like dendrites, at least some of which larger dendrites have a surface that flares outwardly from the core rod;
- and
- separating the larger dendrites from the core rod.
A method for forming single crystal silicon ingots comprising:
- growing multiple polycrystalline silicon dendrites on a substrate;
- separating the dendrites from the substrate;
- charging the crucible of a crystal-growing furnace with dendrites separated from the substrate;
- melting the dendrites in the crucible;
- and
- pulling a single crystal ingot from molten silicon in the crucible.
A body of polysilicon comprising:
- a substrate;
- and
- multiple silicon dendrites extending from a surface of the substrate, at least some of the dendrites having a surface that flares outwardly from the substrate.
A rod of polysilicon comprising:
- an elongated filament;
- a growth layer of silicon surrounding the filament;
- and
- multiple silicon dendrites extending radially from the growth layer, at least some of the dendrites having a surface that flares outwardly from the growth layer.
A polycrystalline silicon dendrite comprising:
- at least one needle-shaped body of polycrystalline silicon having a surface that tapers to a point;
- and
- a growth layer of polycrystalline silicon on the surface of the at least one needle-shaped body, the growth layer having a surface that flares in the same general direction as the at least one needle-shaped body tapers.
A batch of polycrystalline silicon material suitable for use as a raw material in the crucible of a crystal-growing furnace, the batch comprising:
- a plurality of chunks of a broken cylindrical polycrystalline core rod that comprises an elongated filament and a growth layer of silicon surrounding the filament;
- and
- multiple polycrystalline silicon dendrites that were grown on and broken away from the surface of a core rod.
Dependencies are inferred from the claim text.