HOT WIRE CHEMICAL VAPOR DEPOSTION (HWCVD) WITH CARBIDE FILAMENTS
A hot wire chemical vapor deposition apparatus for use in depositing thin films such as amorphous or epitaxial silicon upon a surface of a wafer or substrate by cracking a source or precursor gas such as silane. The apparatus includes a vacuum chamber and a source of precursor gas operable to inject the precursor gas into the chamber. The HWCVD apparatus also includes a heater with a support surface exposed to the deposition chamber, and the heater is operable to heat a substrate positioned upon the support surface. The apparatus includes a catalytic decomposition assembly with a filament positioned between the heater and the precursor gas inlet for selectively passing a current through the filament to resistively heat material of the filament. The filament material may be carbide such as tantalum carbide, which may be coated on a graphite core.
1 . A hot wire chemical vapor deposition (HWCVD) apparatus, comprising:
a deposition chamber operable at vacuum;
a source of precursor gas including a gas inlet for injecting a volume of the precursor gas into the deposition chamber;
a heater with a support surface exposed to the deposition chamber, the heater operable to heat a substrate positioned upon the support surface; and
a catalytic decomposition assembly comprising a filament positioned between the support surface of the heater and the precursor gas inlet and further comprising a power source for selectively passing a current through the filament to resistively heat material of the filament, wherein the filament material comprises a carbide.
2 . The apparatus of claim 1 , wherein the carbide comprises tantalum carbide.
3 . The apparatus of claim 2 , wherein the tantalum carbide is provided as an outer layer that coats a carbon source core.
4 . The apparatus of claim 3 , wherein the carbon source core comprises graphite.
5 . The apparatus of claim 1 , wherein the filament is heated to a temperature of at least about 2000° C. during operation of the power source.
6 . The apparatus of claim 1 , wherein the precursor gas comprises silane, SiCl 4 , SiF 4 , HSiCl 3 , methane, or GeH 4 and the carbide is a coating over a graphite core, the carbide coating comprising an alloy of carbon and a metallic or semi-metallic element.
7 . The apparatus of claim 1 , wherein the carbide comprises an alloy of carbon and at least one of tantalum, tungsten, molybdenum, niobium, scandium, yttrium, zirconium, silicon, and vanadium.
8 . A deposition assembly for use in fabricating a device with a thin film of material by cracking a source gas, comprising:
a vacuum chamber configured to receive the source gas;
a mounting surface within the vacuum chamber for supporting a wafer; and
a filament assembly comprising a filament with an outer surface formed of carbide and electrical contacts for applying a current to the filament, wherein the filament is heated to a temperature of at least 1400° C. when the current is applied.
9 . The assembly of claim 8 , wherein the filament comprises a sheet of interwoven filament elements each comprising at least a carbide coating with a plurality of pores among the filament elements through which the source gas flows to contact a wafer on the mounting surface.
10 . The assembly of claim 8 , wherein the carbide outer surface comprises a thickness of an alloy of carbon and at least one of tantalum, tungsten, molybdenum, niobium, scandium, yttrium, zirconium, silicon, and vanadium.
11 . The assembly of claim 10 , wherein the carbide outer surface comprises tantalum carbide and has a thickness of at least about 10 microns.
12 . The assembly of claim 8 , wherein the filament comprises a core formed of graphite.
13 . The assembly of claim 12 , wherein the filament comprises at least one stress relief section configured structurally to expand and contract with temperature changes.
14 . The assembly of claim 8 , wherein the mounting surface is a portion of a heater and is heated to a temperature of at least 500° C. and wherein the filament is heated to a temperature of at least 2000° C. by the current.
15 . The assembly of claim 14 , the substrate comprises silicon, wherein the source gas comprises silane, and wherein the carbide comprises tantalum carbide.
16 . A thin film deposition method, comprising:
positioning a resistive heater filament within a deposition chamber, the resistive heater filament comprising a carbide material;
mounting a substrate on a surface of a heater facing into the deposition chamber;
with the heater, heating the substrate to an initial deposition temperature;
passing electric current through the resistive heater filament to heat the carbide material to a cracking temperature; and
flowing a deposition source gas into the chamber to flow over the resistive heater filament.
17 . The method claim 16 , wherein the resistive heater filament further includes a graphite core and the carbide material is provided as an outer coating covering the graphite core.
18 . The method of claim 17 , wherein the carbide material is an alloy of carbon and at least one of tantalum, tungsten, molybdenum, niobium, scandium, yttrium, zirconium, silicon, and vanadium.
19 . The method of claim 16 , wherein the cracking temperature is greater than about 2000° C. and the initial deposition temperature is greater than about 500° C.
20 . The method of claim 19 , wherein the deposition source gas is silane, wherein the substrate comprises silicon, and wherein the carbide material comprises tantalum or tungsten carbide.