Coating apparatus – Gas or vapor deposition
Patent
1992-05-21
1994-04-19
Chaudhuri, Olik
Coating apparatus
Gas or vapor deposition
437107, 437126, 437132, 156610, 156611, 156612, 156613, 118720, 4272481, C23C 1600
Patent
active
053042476
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to compound semiconductors produced by using a metal organic vapor phase epitaxy (MOVPE), which is a chemical vapor deposition (CVD) process. The invention particularly relates to a method and apparatus for depositing a III-V compound semiconductor crystal.
DESCRIPTION OF THE RELATED ART
Recently, as structure, properties and so forth of devices such as electronic or optical devices have become more advanced, a precise uniformity of the film thickness and composition, etc., of a semiconductor epitaxial growth film, which is a base of such a device, have been required.
Compound semiconductor crystals have hitherto been formed by a liquid epitaxial growth method, but this growth method is hard to control due to a high growth rate, and thus it has been difficult to satisfy recent, advanced requirements.
For this reason, attention is directed to an MOVPE process in which a semiconductor crystal is grown by pyrolyzing an organometallic compound and a hydride in a vapor phase, as a technique for epitaxially growing a uniform compound semiconductor crystal on a large area substrate or a plurality of substrates, for the liquid epitaxial growth process.
The furnaces of the MOVPE crystal growth are roughly classified into a horizontal CVD furnace and a vertical CVD furnace.
FIGS. 1 to 3 are illustrations showing the principal horizontal furnaces; in the drawings, 1 is a gas injector serving as an introducing port for introducing a deposition gas, 2 is a reaction tube, 3 is a substrate for deposition, 4 is a susceptor supporting the substrate 3, and 5 is a gas exhaust port.
FIG. 1 shows a typical horizontal CVD furnace.
In the horizontal furnace of this drawing, a substrate 3 is horizontally placed on a susceptor 4 installed on a reaction tube 2, and a deposition gas containing raw materials for deposition is substantially horizontally supplied to the substrate 3.
FIG. 2 shows a barrel-type furnace, as a further example of the horizontal CVD furnaces.
In the horizontal furnace of this drawing, a plurality of substrates 3 are placed on the side faces of a susceptor 4 provided in a reaction tube 2, and a deposition gas is supplied from above the reaction tube 2 substantially in parallel to the substrates 3. The susceptor 4 is then rotated so that variations among the crystals deposited on the substrates 3 do not occur. The individual substrates 3 are also rotated, to produce a uniform deposition on a surface of the substrate.
FIG. 3 shows a planetary-type furnace, as another of the horizontal CVD furnaces.
In the horizontal furnace of this drawing, a plurality of substrates 3 are placed on a susceptor 4 horizontally provided in a reaction tube 2, and a deposition gas introduced from the top of the reaction tube 2 is allowed to flow horizontally along the susceptor 4, from substantially the center of the susceptor 4 and radially outwardly, and thereby is supplied to the substrates 3.
These horizontal furnaces are commonly used when epitaxially growing GaAs for high speed devices and AlGaAs/GaAs systems for short wavelength optical devices by an MOVPE process, as the gas flow is relatively simple and the deposition on a large area substrate or a plurality of substrates is facilitated due to the respective structures thereof.
Nevertheless, the horizontal furnaces have the following three major problems:
First, since the deposition gas flows unidirectionally along the substrate surface, the horizontal furnaces have a problem with the growth of crystals on the substrate surface, i.e., due to the consumption of the deposition gas along the flow path, the concentration of the deposition gas becomes weaker in the upstream to downstream direction of the gas flow and, as a result, the crystal deposition rate on the surface of the deposition substrate becomes slower (i.e., gradually reduces) in that same upstream to downstream direction of the gas flow.
Second, a problem arises in that the deposition gas introduced into the horizontal furnace undergoes a temperature distribution in
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Kondo Makoto
Sekiguchi Hiroshi
Chaudhuri Olik
Fujitsu Limited
Paladugu Ramamohan Rao
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