Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-02-16
2001-07-10
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06259174
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a positioning apparatus for positioning without contact a movable body on which an object to be positioned, for example a semiconductor wafer or the like is mounted, a drive unit, and an exposure apparatus incorporating this positioning apparatus.
BACKGROUND ART
Conventionally, in a photolithography process for producing a semiconductor device, an image sensing device (CCD or the like), a liquid crystal display device, a thin-film magnetic head or the like, a projection exposure apparatus has been used, such as a stepper or the like for transferring a pattern in a reticle serving as a mask onto each shot area on a wafer (or a glass plate or the like) serving as a substrate, via a projection optical system. With such a projection optical system, it is necessary to position the wafer on an exposure position with high precision. Hence, the wafer is held by a wafer holder by means of vacuum attachment or the like, and conventionally this wafer holder has been fixed on a wafer stage which can be positioned with high precision.
On the contrary, to position a wafer with high precision and at a high speed without being affected by the precision of the mechanical guide face or the like, recently a development of a positioning apparatus for positioning a wafer by lifting a flat table on which the wafer is mounted in a non-contact state has been under way. For example, in U.S. Pat. No. 5,196,745, there is proposed a positioning apparatus in which a permanent magnet with the outside being a N-pole and a permanent magnet with the outside being a S-pole are alternately and two-dimensionally disposed on the upper and lower faces of a table on which a wafer is mounted, and a polyphase coil train corresponding to these permanent magnets is arranged on a fixed body side where the table is housed. With this positioning apparatus, by utilizing the fact that the thrust in the horizontal direction occurs in the polyphase coil where the magnetic flux of the permanent magnets is perpendicular to the table, and the thrust in the vertical direction occurs in the polyphase coil where the magnetic flux is horizontal, the table is positioned in a non-contact state in the directions of six degrees of freedom.
With such a conventional non-contact type positioning apparatus, a plurality of permanent magnets in which the polarity is alternately reversed are attached on the upper and lower faces of the table serving as a movable body. Therefore, the table becomes large, and the weight also becomes heavy. Moreover, the thrust in the vertical direction by means of the polyphase coils is very small, and it has in practice been difficult to lift a table having a large weight only by the vertical thrust.
Moreover, the positioning apparatus requires a coil train having a size twice as large as the moving stroke of the table. Hence there is a problem in that the apparatus becomes large.
DISCLOSURE OF THE INVENTION
A first object of the present invention is to provide a positioning apparatus which can stably support a movable body on which an object to be positioned such as a wafer or the like is mounted, and precisely position the movable body.
A second object of the present invention is to provide a positioning apparatus which can position a movable body in a non-contact state without making a drive mechanism too large compared to the moving stroke of the movable body.
Another object of the present invention is to provide a drive unit which can be used in such a positioning apparatus, and an exposure apparatus which incorporates such a positioning apparatus and which can produce a semiconductor device or the like with high throughput and high accuracy.
To achieve these objects, the positioning apparatus according to the present invention is a positioning apparatus for positioning a movable body on which an object to be positioned is mounted, the positioning apparatus having a basic construction in that it comprises; a magnetism generation body incorporated in the movable body, a magnetic member formed so as to have the magnetism generation body therebetween, and a drive unit disposed between the magnetism generation body and the magnetic member, for driving the magnetism generation body, and the movable body is positioned by means of the magnetic member and the drive unit.
Under this basic construction, with a (first) positioning apparatus of the present invention, the magnetism generation body (
8
) (for example, one or a plurality of flat plates) generates a magnetic flux directed toward one direction perpendicular to a moving plane of the movable body (
6
), the magnetic member (
10
,
15
A to
15
C,
16
) forms a magnetic circuit together with the magnetism generation body (
8
), and the drive unit incorporates a lifting coil (
14
) which is wound so as to generate a variable thrust in a direction perpendicular to the moving plane, with respect to the magnetism generation body (
8
), and the movable body (
6
) is positioned in a non-contact state by means of the magnetic member (
10
, etc.) and the drive unit (
11
).
According to such a (first) positioning apparatus, a movable table (
6
,
8
) comprising the movable body (
6
) and the magnetism generation body (
8
) can be made thin and lightweight. At this time, the magnetism generation body (
8
) may work as the movable body (
6
). Moreover, with the present invention, principally two magnetic circuits are formed. The first magnetic circuit is a magnetic circuit in which the magnetic flux coming out from the N-pole of the magnetism generation body (
8
) returns to the S-pole of the magnetism generation body (
8
) via the magnetic member on the upper face or the bottom face and the magnetic member facing this. The second magnetic circuit is a magnetic circuit in which the magnetic flux coming out from the N-pole of the magnetism generation body (
8
) leaks into space, and returns to the S-pole, for example through the magnetic member on the upper face.
The first and the second magnetic circuits generate attraction to the magnetic member on the upper face and the bottom face with respect to the movable table (
6
,
8
), respectively, and by magnetically controlling the attraction, a lifting force is generated in the movable table. Hence the movable table can support the deadweight. As a result, the lifting coil (
14
) of the drive unit (
11
) has only to adjust the repulsion or the attraction within a predetermined range. Hence the heat generation thereof becomes minimum. To magnetically control the attraction, the height of the movable table may be adjusted, or the size of the coil in the drive unit (
11
) may be adjusted, or the permeance of the magnetic member may be adjusted.
By controlling the repulsion or the attraction in the lifting coils, of for example three or more drive units (
11
), the height of the movable table and the inclination around two axes can be controlled. That is to say, positioning in the height direction can be accurately performed.
With an other (second) positioning apparatus according to the present invention, the magnetism generation body (
8
) generates a magnetic flux directed toward one direction perpendicular to a moving plane of the movable body (
6
), the magnetic member (
10
,
15
A to
15
C,
16
) forms a magnetic circuit together with the magnetism generation body (
8
), and the drive unit (
11
) incorporates: a core member (
20
) which passes the magnetic flux within the magnetic circuit; a first thrust generation coil (
12
A) wound around the core member so as to generate a thrust consisting of a Lorentz force in a first direction within the moving plane, with respect to the magnetism generation body (
8
); and a second thrust generation coil (
13
A) wound around the core member so as to generate a thrust consisting of a Lorentz force in a second direction crossing the first direction within the moving plane, with respect to the magnetism generation body (
8
).
According to the (second) positioning apparatus, by the reaction force to the Lorentz force generated by the ele
Nikon Corporation
Oliff & Berridg,e PLC
Waks Joseph
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