Rotary kinetic fluid motors or pumps – Smooth runner surface for working fluid frictional contact
Reexamination Certificate
1999-07-06
2002-04-02
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Smooth runner surface for working fluid frictional contact
C415S111000, C417S423140
Reexamination Certificate
active
06364604
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to a vacuum pump and a vacuum apparatus equipped with the vacuum pump.
2) Description of the Related Art
In a case where dry etching, CVD, spattering, ion injection, etc. are performed in a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, etc., a vacuum pump such as a turbo molecular pump is widely used to perform vacuum processing by discharging the processing gas within a chamber.
FIG. 8
shows a typical turbo molecular pump which has been used.
As shown in
FIG. 8
, the turbo molecular pump has stator vanes and rotor vanes which are respectively disposed on a stator portion and a rotor portion in multiple stages in an axial direction, so that by rotating the rotor portion at a high speed with a motor an exhaust (vacuum) action occurs from an intake port side, i.e. the upper side in the drawing, to an exhaust port side, i.e. the left and lower side of the drawing.
FIG. 9
shows a typical vacuum apparatus in which the turbo molecular pump of this type is mounted to a chamber.
As illustrated, the vacuum apparatus has a stage
12
which is located within a chamber (container)
10
so that a sample
11
or the like can be placed on the stage
12
, and a drive mechanism
13
which is located below the stage
12
and outside the chamber
10
so as to rotate the stage
12
or perform other functions. A turbo molecular pump
15
is mounted from the outside of the chamber
10
onto an exhaust port
14
portion located at the lower surface (or side surface) of the chamber so as to discharge the gas existing within the chamber
10
.
However, if the sample
11
occupies a certain degree of area, the pressure in a side A closer to the turbo molecular pump
15
is lower, whereas the pressure in a side B farther therefrom is higher since the turbo molecular pump
15
is situated away from a center of the sample
11
. That is, non-uniform pressure distribution is created in the vicinity of the sample
11
.
Such non-uniform pressure distribution within the chamber
10
results in non-uniformity in various conditions such as a manufacturing condition, a reaction condition, a measurement condition for the sample
11
. In particular, in case of the semiconductor manufacturing process, since a wafer disposed as the sample
11
on the stage
12
has been increasing in diameter recently, a pressure difference is likely to be caused around the wafer, which hinders the manufacturing of the uniform products.
In an attempt to make the pressure within the chamber
10
uniform, vacuum apparatuses of the following arrangements have been proposed.
For example, as shown in
FIG. 10
, a plurality of exhaust ports
14
are provided (four holes are provided in the drawing) within the chamber
10
at equidistance around the stage, and the exhaust ports
14
are connected through a branch pipe
17
to a single turbo molecular pump
15
. In addition, the stage is disposed at a central position with respect to the exhaust ports
14
and the stage drive mechanism is disposed at the central portion circumscribed by the branch pipe
17
although they are not illustrated in
FIG. 10
for convenience in explaining the arrangement of the piping.
By locating the exhaust ports
14
at equidistance around the sample
11
in this manner, it is possible to make the pressure around the sample
11
uniform.
As shown in
FIG. 11
, such a vacuum apparatus is also available that a plurality of exhaust ports
14
are provided (four holes are provided in the drawing) within the chamber
10
at equidistance around the stage, and the exhaust ports
14
are connected to respective turbo molecular pumps
15
.
The vacuum apparatus thus constructed can eliminate the non-uniformity of the pressure distribution since the exhaust action is carried out by the turbo molecular pumps
15
using the plurality of exhaust ports
14
that are disposed uniformly around the sample
11
.
Further, as shown in
FIG. 12
, such a vacuum apparatus is also available that a conductance adjustment plate
18
is disposed between the stage
12
and the exhaust port
14
within the chamber
10
.
Only one exhaust port
14
is provided in this vacuum apparatus, but since the conductance adjustment plate
18
serves as a resisting plate against the exhaust or discharge flow, it is possible to suppress the non-uniformity in pressure distribution within the chamber
10
.
The vacuum apparatus shown in
FIG. 10
, however, requires the turbo molecular pump
15
to be disposed at such a position as to avoid the interference with the drive mechanism that is located in the chamber
10
. Accordingly, the branch pipe
17
is also required to be led to the turbo molecular pump
15
while avoiding the interference with the drive mechanism. This restriction in piping design is likely to cause the non-uniform conductance (exhaust resistance) of the pipe, and thus it is required to additionally install a pressure adjusting valve at a location midway of the pipe or to partially modify the length or diameter of the pipe, which results in an increase in cost.
Further, the turbo molecular pump
15
of a larger exhaust speed is required due to the conductance of the branch pipe
17
, and the entire cost for the apparatus is increased accordingly.
Moreover, although the vacuum apparatus shown in
FIG. 10
is advantageous over the vacuum apparatus shown in
FIG. 9
from the viewpoint of the uniform pressure distribution, the provision of only four exhaust ports
14
cannot solve such a pressure non-uniformity problem that a pressure difference is caused between the vicinity of each exhaust port
14
and the intermediate position between an adjacent exhaust ports
14
and
14
. The provision of the increased number of exhaust ports
14
and the pipes may solve this non-uniformity problem, but such will further increase the cost.
In the case of the vacuum apparatus shown in
FIG. 11
, since an independent turbo molecular pump
15
is installed for a respective exhaust port
14
, the apparatus is free from the increase of conductance due to the use of the branch pipe, but suffers from a problem in that the provision of the plurality of turbo molecular pumps results in the higher cost in comparison to the provision of the branch pipe. Further, similarly to the vacuum apparatus shown in
FIG. 10
, the apparatus encounters the pressure non-uniformity problem in which a pressure difference is caused between the vicinity of each exhaust port
14
and the intermediate position between the adjacent exhaust ports
14
and
14
.
In the case of the vacuum apparatus shown in
FIG. 12
, the provision of the conductance adjusting plate
18
increases the cost, and is insufficient to effectively eliminate the non-uniformity of the pressure distribution.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a vacuum pump of a novel arrangement, which can eliminate the non-uniformity of the pressure distribution around the stage.
A secondary object of the present invention is to provide a vacuum apparatus of a novel arrangement, which can eliminate the non-uniformity of the pressure distribution around the stage.
According to a first aspect of the present invention, there is provided a vacuum pump which comprises: an outer casing including an inner cylinder having a hollow portion inside thereof, the hollow portion being communicated with an atmospheric air and capable of accommodating a device therein, an outer cylinder disposed outside the inner cylinder, and a bottom surface plate closing a gap between the outer cylinder and the inner cylinder at one end side; an exhaust port disposed at the one end side of the outer casing; a rotor main body disposed between the inner cylinder and the outer cylinder; a bearing supporting the rotor main body; a motor which rotates the rotor main body, the motor being disposed between the inner cylinder and the rotor main body or between the outer cylinder and the rotor main body; and a pump mechanism which carries
Nonaka Manabu
Okada Takashi
Adams & Wilks
Look Edward K.
McAleenan James M
Seiko Instruments Inc.
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