Coating apparatus – Gas or vapor deposition
Reexamination Certificate
1999-11-24
2002-05-07
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
C118S724000, C118S725000
Reexamination Certificate
active
06383300
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat treatment apparatus and a cleaning method of the same, and more particularly to a heat treatment apparatus in which reactive products are prevented from attaching thereinto and a cleaning method of the same.
2. Description of the Related Art
A silicon oxide film (SiO
2
film) or a silicon nitride film (Si
3
N
4
film) is used in various sections of a semiconductor device.
An SiO
2
film is produced by resolving alkoxysilane in a decompression CVD device, etc. An unreacted substance of alkoxysilane [(SiC
x
H
y
O
z
)
n
X=0.1 to 2, y=1 to 15, z=0.1 to 5, n>0] attaches into the CVD device in a process for producing an SiO
2
film. Such a substance comes off in a process for forming a film, and becomes particles. This process has the drawback of lowering the quality of to-be-manufactured semiconductor devices and of having a low overall yield.
An Si
3
N
4
film is produced by a reaction of, for example, ammonia (NH
3
) and dichlorosilane (SiH
2
Cl
2
) in the CVD device. While a silicon nitride filmi is being formed, ammonia chloride (NH
4
Cl) may be in a state of solidity in a low-temperature section of a reaction tube. If the ammonia chloride is sublimated when loading a semiconductor substrate and attaches to the semiconductor substrate, it becomes a source for particles to be formed on the surface of the substrate in a process for forming a film. Particles which have been formed as a result of a reaction of the sublimated ammonia chloride and moisture within the atmosphere attach onto the semiconductor substrate, resulting in a defective feature of the semiconductor device.
The temperature and the exhaust conductance of a manifold of a reaction tube, the periphery of an exhaust section and an exhaust pipe are lower than those of a film-forming area where a wafer boat is arranged. Therefore, a lot of reactive products are likely to attach into those sections.
Accordingly, the conventional heat treatment apparatus has been taken apart in order to clean its composing elements for large scale maintenance, while the operations of the apparatus are suspended for a long period of time. Therefore, only a low operational rate of the apparatus has been achieved.
In order to prevent the apparatus from being operated at a low operational rate while cleaning its composing elements, Unexamined Japanese Patent Application KOKAI Publication No. H5-214339 discloses a method of cleaning an apparatus forming silicon nitride films with using HF gas. In addition to this, Unexamined Japanese Patent Application KOKAI Publication No. H4-333570 discloses a method of cleaning an apparatus by removing nitrogen silicon therefrom with using HF gas. The references cited disclose merely a method of cleaning an apparatus by removing (SiC
x
H
y
O
z)
n
with using HF gas and by removing nitrogen silicon. In the references, no disclosure has been made to a method of forming films in a heat treatment apparatus and a method of cleaning the same The references do not even disclose a technique for preventing HF gas used for the cleaning from contaminating the environment.
In various processes for manufacturing semiconductor devices, a two-layered film, such as SiO
2
/Si
3
N
4
, etc. or three-layered film, such as SiO
2
/Si
3
N
4
/SiO
2
, etc. is used. Conventionally, an SiO
2
film and an Si
3
N
4
film have been produced in different apparatuses. Thus, when transferring a wafer from one apparatus to the other, a natural oxide film and particles obviously attach onto the surface of the wafer. This causes the problem of lowering the quality of to-be-manufactured semiconductor devices and of having a low overall yield.
Accordingly, it is preferred that an apparatus can form the SiO
2
film together with the Si
3
N
4
film. However, no proposal has yet been made for an apparatus in which particles are prevented from attaching thereinto.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in consideration of the above, in order to clean a heat treatment apparatus with efficiency.
An object of the present invention is to provide a method of efficiently cleaning an apparatus capable of producing various kinds of films.
Another object thereof is to provide a technique for cleaning a heat treatment apparatus with using HF gas while preventing the used HF gas from contaminating the environment.
In order to achieve the above objects, according to the first aspect of this invention, there is provided a heat treatment apparatus, comprising
a reaction tube which can contain an object to be heat-treated;
an exhaust pipe, one end of which is connected to the reaction tube, for exhausting gas contained in the reaction tube;
a reactant-gas supplying pipe, which is conducted into the reaction tube, for supplying reactant gas into the reaction tube;
an HF-gas supplying section which includes
an HF pipe connected to a gas source for hydrogen fluoride,
an HF valve which controls to supply hydrogen fluoride from the gas source and which is arranged in the HF pipe, and
an inlet which conducts, into the exhaust pipe and/or the reaction tube, the fluoride hydrogen supplied from the gas source through the HF pipe,
wherein the HF valve is open and the fluoride hydrogen gas is conducted from the gas source into the exhaust pipe and/or the reaction tube, thereby cleaning inside of the exhaust pipe and/or the reaction tube.
In the structure, an inlet for supplying HF gas is arranged in the reaction tube separately from the reactant-gas supplying pipe. When an HF valve is open, HF gas can be conducted into the reaction tube and/or the exhaust pipe which can then be cleaned. Therefore, the heat treatment apparatus can be cleaned with simple treatments only.
In the structure disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H5-214339, as shown in FIG. 2 included in the Publication, HF gas and reactant gas are conducted into a reaction tube from an identical gas-supplying section. Therefore, the reactant gas is fearfully contaminated in a process for forming a film.
Unexamined Japanese Patent Application KOKAI Publication No. H4-333570 suggests (1) a method for conducting HF gas into an apparatus which can form thin films and (2) a method for conducting HF gas into a cleaning apparatus by inserting the apparatus itself into the cleaning apparatus. However, no disclosure has been made to a “structure for efficiently conducting HF gas into the apparatus so as to clean the apparatus”.
The other end of the exhaust pipe may be split into a first and second vents; and
a valve may be arranged between the first and second vents, may conduct exhaust gas into the second vent when HF gas is exhausted, and conduct exhaust gas into the first vent when no HF gas is exhausted.
According to this structure, the products produced while forming a film and the HF gas used for cleaning the apparatus can separately be heat-treated. An HF gas scrubber may be used as the second vent, whereas a scrubber for any other kind of gas may be used as the first vent.
In the heat treatment apparatus, there may be arranged a plurality of traps which are arranged on the exhaust pipe and which remove a reactive product within the exhaust pipe, and
a pressure control valve which is arranged between the plurality of traps and which maintain pressure within the reaction tube and the exhaust pipe at a fixed value.
It is necessary to maintain the pressure within the reaction tube and the exhaust pipe at an appropriate value in order to form a film and clean any part of the apparatus. The pressure control valve controls the pressure by itself or together with any other device. Since the pressure control valve is arranged between the plurality of traps, the reactive products are prevented from attaching to the pressure control valve (normally, the reactive products easily attach thereto).
The reaction tube includes an inner tube, whose upper end is open, and an outer tube, which surrounds the inner tube with a predetermi
Murata Hitoshi
Saito Yukimasa
Yamamoto Hiroyuki
Baker & McKenzie
Lund Jeffrie R.
Tokyo Electron Ltd.
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