Bearings – Linear bearing – Fluid bearing
Reexamination Certificate
2000-08-15
2001-12-11
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Fluid bearing
Reexamination Certificate
active
06328473
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a static air-bearing which provides a gas layer between two relatively movable parts (fixed part and movable part) and a predetermined clearance between the two parts, to a stage apparatus using the air-bearing, and to an optical apparatus using the state apparatus.
2. Description of the Related Art
In the process for producing semiconductor devices, to project a circuitry pattern onto a wafer, a mask or reticle (hereinafter “reticle”) forming the circuitry pattern to be projected thereon is used. During the process to manufacture the intended semiconductor wafer, an inspection apparatus is used to inspect whether the circuitry pattern to be projected has been accurately formed on the wafer in accordance with a circuitry design.
The inspection apparatus is designed to be able to inspect the whole surface of the wafer to be inspected by moving the wafer using a stage apparatus. A static air-bearing is used in the stage apparatus accommodated in the inspection apparatus, because high positioning accuracy is required.
Referring to
FIG. 10
, such stage apparatus using a static air-bearing will be explained.
FIG. 10
is a sectional view of a stage apparatus. In
FIG. 10
, an X-axis and a Y-axis, perpendicular to each other, are set in a plane parallel to a installation floor G; and, a Z-axis is set perpendicular to the installation floor G.
This stage apparatus has a stage
102
which mounts a wafer
101
to be inspected on it. The stage
102
is connected to a movable part
103
of a static air-bearing (
103
,
104
). The movable part
103
has a rectangular sectional profile. A fixed part
104
is disposed so that the three surfaces of the −X side end portion of the movable part
103
and of the +X side end portion of the movable part
103
are surrounded by this fixed part
104
. Further, the fixed part
104
is fixed on the installation floor G via a fixing part
105
.
Bearing pads
104
a
which blows air from a air supply (not shown) into the space between the fixed part
104
and the movable part
103
, are disposed at each surface of the fixed part
104
facing the movable part
103
. Further, air exhaust grooves
104
b
which temporarily store the air blown out of the bearing pads
104
a
are formed around the bearing pads
104
a
to exhaust the air; and, air exhaust ports
104
c
which are connected to a vacuum pump (not shown) are provided with the air exhaust grooves
104
b.
In the static air-bearing (
103
,
104
), the air is continuously blown into the space between the movable part
103
and the fixed part
104
, and the blown up air is temporarily stored in the air exhaust grooves
104
b
and then exhausted through the air exhaust ports
104
c.
Therefore, an air layer of approximately constant pressure is formed in the space between the movable part
103
and the fixed part
104
, and the movable part
103
and the fixed part
104
will be kept apart at a predetermined clearance.
A movable piece
106
of a linear motor (
106
,
107
) is connected to the movable part
103
, and the movable piece
106
is disposed so that the movable piece
106
faces a stator
107
leaving a space. The linear motor (
106
,
107
) can move the movable piece
106
in the Y-direction along the stator
107
.
Referring now further to
FIG. 11A
, the static air-bearing of the stage apparatus will be explained.
FIG. 11A
is a sectional view of the movable part
103
and the fixed part
104
, illustrated in
FIG. 10
, taken on line A—A in
FIG. 10
, and is attached with a similar coordinate system.
In this static air-bearing, the length of the movable part
103
must be longer than the length of the fixed part
104
by approximately the moving stroke, because the bearing pads
104
a
on the fixed part
104
and movable part
103
need to face each other during the movement of the movable part
103
. The movable part
103
moves up to the position indicated by the dashed lines in the Figure.
Thus, relative to this static air-bearing, approximately two times the length of the moving stroke over the fixed part
104
is to be secured to satisfy the free movement of the movable part
103
with respect to the Y-direction, which yields a problem that this bearing becomes large sized.
Accordingly, another problem that a stage apparatus which uses this static air-bearing also becomes large sized arises. Also, an inspection device which accommodates this stage apparatus become large sized. Those problems also occur, not only with respect to the inspection device, but also with respect to other optical apparatuses which accommodate similar stage apparatuses, e.g., exposure apparatuses that are used in the lithography process for producing semiconductor or LCD elements, electron microscopes, or electron beam apparatuses that transfer or form circuitry patterns on substrates by irradiating electron beams onto substrates.
By contrast, in such static air-bearing as shown in
FIG. 11B
in which bearing pads and air exhaust ports are disposed on a movable part, the movable part needs only to move up to the position indicated by the dashed lines in the
FIG. 11B
while this air-bearing is configured to realize a similar moving stroke as is realized by the air-bearing shown in the above FIG.
11
A. Thus, the adoption of this air-bearing makes the length to be secured with respect to the Y-direction shorter.
However, in the static air-bearing disposing the bearing pads and the air exhaustion ports on the movable part as shown in
FIG. 11B
, a problem that arrangement of pipes relayed to the air exhaustion ports becomes very difficult arises. That is, the pipes for air exhaustion are generally made of metallic, elastic bellows so that the pipes do not crush due to sucking force caused by air suction by means of a vacuum pump and still follow the movement of the movable part. While a certain force is necessary to give the metallic bellows telescopic motion, it is difficult to give the metallic bellows smooth telescopic motion following the movement of the movable part.
For example, in the configuration in which force being executed on the movable part also gives the bellows the telescopic motion, reaction force from the bellows executes on the movable part, so that a proper clearance between the fixed part and the movable part might not be maintained or accurate movement of the movable part might be influenced.
An object of the present invention is to provide a static air-bearing which can limit its size and can make pipe arrangement easy, a stage apparatus using the air-bearing, and an optical apparatus using the stage apparatus.
SUMMARY OF THE INVENTION
Referring to and associating with
FIGS. 1-9
showing embodiments of the present invention, the above object is accomplished by a static air-bearing having a fixed part (
4
,
32
) and a movable part (
3
,
31
) which is movably disposed among the fixed part (
4
,
32
), and providing a predetermined clearance between the fixed part (
4
,
32
) and the movable part (
3
,
31
) with an air layer, the static air-bearing being characterized in that the movable part (
3
,
31
) has an air blow portion (
3
a
) which blows air into the air layer between the fixed part (
4
,
32
) and the movable part and has an air exhaust groove (
3
c,
11
a,
21
a,
31
a,
31
b
) which exhausts the air blown out of the air blow portion (
3
a
) and in that the fixed part (
4
,
32
) has an air exhaust port (
4
a,
32
a,
32
b
) which is disposed at a position facing the air exhaust groove (
3
c,
11
a,
21
a,
31
a,
31
b
).
Further, in a static air-bearing embodiment of the present invention, the air exhaust groove (
3
c,
11
a,
21
a,
31
a,
31
b
) is characterized in that it is disposed so as to surround the air blow portion (
3
a
). In addition, in a static air-bearing embodiment of the present invention, the air exhaust port (
4
a,
32
a,
32
b
) is characterized in that it is disposed, with respect to movement direction of the movable part (
3
,
31
), approximately on the ce
Okubo Yukiharu
Shimoda Toshimasa
Tokushima Shinobu
Hannon Thomas R.
Nikon Corporation
Oliff & Berridg,e PLC
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