Coating apparatus – Gas or vapor deposition – Work support
Reexamination Certificate
2000-01-21
2001-05-22
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
Work support
C118S715000, C118S724000, C118S725000, C118S729000, C118S733000, C432S241000, C432S250000, C432S253000
Reexamination Certificate
active
06235121
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a vertical thermal treatment apparatus of a type wherein a vertical rotational shaft passes through a shaft hole and penetrates into a reaction vessel that is designed for performing a thermal treatment on a substrate to be processed, using processing gases under vacuum environment.
2. Description of Related Art
A vertical thermal treatment apparatus is known in the art as an apparatus for subjecting a batch of semiconductor wafers (hereinafter called “wafers”) to a thermal treatment, and such a vertical thermal treatment apparatus is used for procedures such as the film-formation processing called reduced-pressure CVD, oxidation, and the diffusion of impurities. In each of these apparatuses, the configuration is such that a wafer boat holding wafers in multiple layers is conveyed into a vertical reaction vessel, usually from below, and a lower aperture of the reaction vessel is closed hermetically by a lid member that supports the wafer boat.
In this type of apparatus, the wafer boat is made to rotate about a vertical shaft in order to improve the uniformity of the thermal treatment within each wafer surface, and in such a case the configuration is such that the vertical rotational shaft penetrates the lid member and the wafer boat is supported on that rotational shaft.
As shown in
FIG. 6
, a shaft support device is used for introducing a rotational shaft through a lid member and into the reaction vessel of a reduced-pressure CVD furnace.
FIG. 6
shows a state in which a lower aperture of a manifold
11
, which is provided in a lower portion of a double-walled reaction tube
10
, is closed by a lid member
12
. A vertical rotational shaft
13
penetrates within a metal cylindrical casing
14
that is provided on a lower side of the lid member
12
, with a turntable
15
attached to the upper end thereof and a pulley
16
driven by a motor (not shown in the figure) attached to the lower end thereof. A shaft bearing
17
is provided between the cylindrical casing
14
and the rotational shaft
13
, with a magnetic seal means
18
provided thereabove to form a hermetic seal between the reaction vessel (which is configured of the reaction tube
10
and the manifold
11
in this case) and the exterior.
The magnetic seal means
18
consists of a support member
18
a,
which surrounds the rotational shaft
13
, and a magnetic fluid
18
b,
with the magnetic fluid
18
b
providing a hermetic seal between the exterior and the interior space on the side of the reaction vessel of the cylindrical casing
14
. The support member
18
a
is configured of a plurality of magnetic path members that are U-shaped in vertical section and are arrayed in the vertical direction, and the magnetic fluid
18
b
provides a magnetic seal between the edge portion of each of the magnetic path members and the rotational shaft
13
.
If the film-formation gases should intrude into the shaft support device during the film-formation processing with the above described prior-art configuration, the film-formation gases will come into contact with cooled portions where reaction by-products will be generated, and these will adhere to the support member
18
a
of the magnetic seal means
18
, which will slow the rotation.
The inventors have studied the use of a common furnace for CVD and for oxidation and diffusion but the prior-art configuration raises a problem when used in common in this manner in that moisture penetrates into the shaft support device during wet oxidation and that moisture causes deterioration in the magnetic fluid
18
b
of the magnetic seal means
18
.
In that case, it could be considered to use a configuration wherein there is no through-hole in the lid member
12
and a shaft on the inner side of the lid member
12
and a shaft on the outer side thereof are linked by magnetic coupling, instead of providing the rotational shaft
13
that passes through the lid member
12
, but in this case solid members of synthetic resin are used as lubrication members in a magnetic coupling structure, which means that the load resisting characteristics thereof are poor and there is a danger of vibration in the shafts at high loads. In addition, ceramic bearings are used in a magnetic coupling structure, but such bearings expand at high temperatures and cause rubbing between adjacent bearings and there is a danger that the rubbing thereof will generate particles, so a small gap is provided in order to prevent this generation of particles, but this leads to rattling at normal temperatures.
The present invention was devised in the light of the above circumstances and the object thereof is to provide a vertical thermal treatment apparatus wherein a rotational shaft penetrates into a reaction vessel in which a film is formed under a vacuum environment, and, wherein the intrusion of gases and moisture into a shaft seal portion from the interior of the reaction vessel is restrained and adverse effects on seal materials are prevented.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a vertical thermal treatment apparatus comprising a vertical reaction vessel, a lid member for closing a bottom portion of the reaction vessel, a rotational shaft penetrating in a vertical direction upwards from below through the lid member and into the reaction vessel, a turntable provided on the rotational shaft within the reaction vessel and supporting a support member for a substrate to be processed, and a rotational drive mechanism for driving the rotational shaft in rotation to rotate the support member for a substrate to be processed, wherein the thermal treatment apparatus further comprises: a substantially cylindrical fixing member fixed to the lid member and having a shaft hole through which the rotational shaft passes; a bottomed cylindrical outer shell member having a side wall portion surrounding the fixing member, with a space opened up between the side wall portion and the fixing member, and a bottom portion fixed hermetically to an outer peripheral surface of the rotational shaft below a lower end of the fixing member, for enabling communication between a gap between the shaft hole and the rotational shaft and a space on an outer side of the fixing member; a shaft bearing provided between the fixing member and the side wall portion, at an upper position within the opened-up space between the side wall portion and the fixing member; and a seal portion provided between the fixing member and the side wall portion to form a seal between an outer wall surface of the fixing member and an inner wall surface of the side wall portion, at a lower position in the opened-up space between the side wall portion and the fixing member.
The seal portion may be a magnetic seal portion in which a magnetic fluid is used as a sealing member. A purge gas supply path may be connected to the fixing member at a position closer to the reaction vessel than the seal portion, for supplying a purge gas into the gap between the shaft hole and the rotational shaft. The configuration could be such that an annular groove is provided in an upper surface of the bottom portion of the outer shell member and an annular protruding portion is provided in a lower end of the fixing member to engage the annular groove.
The purge gas supply path is connected to an inert gas supply source and is provided with means for maintaining a pressure within the purge gas supply path to be greater than atmospheric pressure. It would be advantageous if the purge gas supply path were configured of flexible synthetic resin piping. The means for maintaining a pressure within the purge gas supply path to be greater than atmospheric pressure may be provided with a gas pressurization device within the purge gas supply path and throttle means within the purge gas supply path at a position closer to the fixing member than the gas pressurization device. It would be advantageous if the throttle means were incorporated within a pipe joint provided in the purge gas supply path.
Honma Manabu
Shimazu Tomohisa
Lund Jeffrie R.
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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