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Stage system, exposure apparatus, and device manufacturing methodStage system, exposure apparatus, and device manufacturing method description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060082755, Stage system, exposure apparatus, and device manufacturing method. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a divisional application of copending U.S. patent application Ser. No. 10/862,383, filed on Jun. 8, 2004. FIELD OF THE INVENTION AND RELATED ART [0002] This invention relates to a stage system to be used in various measuring instruments, or in a projection exposure apparatus, for a semiconductor lithography process, for moving and positioning a substrate, such as a wafer, at a high speed and with a high precision. The stage system of the present invention is best suited for a stage system particularly to be used in an electron beam exposure apparatus, in which an electron beam is used to perform pattern drawing for direct patterning of a wafer or reticle exposure, or in an EUV (extreme ultraviolet) exposure apparatus using EUV light as exposure light in which the stage system is used in a vacuum ambience. [0003] The manufacture of devices such as semiconductor devices, for example, is based on lithography technology in which various patterns formed on a mask are transferred to a wafer in a reduced scale, by use of light. Extremely high precision is required in relation to the mask pattern to be used in such lithography technology, and an electron beam exposure apparatus is used to make such a mask. Further, an electron beam exposure apparatus is used also in a case wherein a pattern is to be directly formed on a wafer without using a mask. [0004] As regards such an electron beam exposure apparatus, there is a point beam type apparatus wherein an electron beam to be used is shaped into a spot-like shape, and a variable rectangle-beam type apparatus wherein an electron beam has a rectangular section of various size, for example. In these types of exposure apparatus, however, generally, the apparatus comprises an electron gun unit for producing an electron beam, an electron optical system for directing the produced electron beam to a sample, a stage system for scanningly moving the whole surface of the sample with respect to the electron beam, and an objective deflector for positioning the electron beam upon the sample very precisely. [0005] The region that can be positioned by use of an objective deflector has only a small size of about a few millimeters, to suppress the aberration of the electron optical system as much as possible. To the contrary, as regards the size of the sample, for a silicon wafer, it is about 200-300 mm in diameter, and for a glass substrate to be used as a mask, it is about 150 mm square. So, the electron beam exposure apparatuses include a stage system by which the whole surface of the sample can be scanned with the electron beam. [0006] In electron beam exposure apparatuses, since the positioning response of the electron beam is extraordinarily high, generally, they use a system in which the attitude of the stage or a positional deviation thereof is measured and the measured value is fed back to the positioning of the electron beam through the deflector, rather than attempting to improve the mechanical control characteristic of the stage. Also, since the stage is disposed in a vacuum chamber and, furthermore, there is a restriction that a change in a magnetic field that may influence the positioning precision of the electron beam must be avoided, generally, the stage is disposed by use of a limited element of a contact type, such as rolling guides or ball screw actuators. [0007] Such contact type elements involve a problem of lubrication and dust creation, for example. Japanese Laid-Open Patent Application No. 2002-252166 shows a countermeasure therefor, and FIG. 10 illustrates it, that is, a stage having two freedoms of movement in a planar direction, using vacuum air guides and linear motors. In the example of FIG. 10, very smooth acceleration can be accomplished and, yet, with respect to the positioning direction, external disturbance from the guide is very small. In the illustrated example, the stage comprises an X slider, a Y slider and an X-Y slider, wherein the X slider and the Y slider are confined with respect to rotation about the Z axis, by means of radial bearings. [0008] FIG. 11 shows an example of a stage, to be used in an atmosphere, corresponding to a stage disclosed in Japanese Laid-Open Patent Application No. 2002-8971. In the example of FIG. 11, like the example of FIG. 10, the stage comprises an X slider (X guide bar 28), a Y slider (Y guide bar 29), and an X-Y slider, but the X slider and the Y slider are not confined with respect to rotation about the Z axis. [0009] As regards the election beam exposure apparatus, there is a known example disclosed in Japanese Laid-Open Patent Application No. H09-330867. In the apparatus of this document, a plurality of electron beams are projected upon the surface of a sample along design coordinates and the electron beams are deflected along the design coordinates to thereby scan the sample surface. Additionally, in accordance with a pattern to be drawn, the electron beams are individually turned on and off to thereby draw the pattern. In such a multiple electron-beam type exposure apparatus, a desired pattern can be drawn by use of plural electron beams, and thus, the throughput can be improved. [0010] FIG. 12 illustrates a general structure of a multiple electron-beam type exposure apparatus. Denoted at 501a, 501b, and 501c are electron guns by which a plurality of electron beams can be individually turned on and off. Denoted at 100 is a reduction electron optical system for reducing and projecting the electron beams from the electron guns 501a, 501b and 501c, onto a wafer 305. Denoted at 306 is a deflector for scanning the plural electron beams projected to the wafer 305. [0011] FIG. 13 illustrates the action as a wafer is scanned with plural electron beams, in the exposure apparatus of FIG. 12. White small circles depict beam reference positions BS1, BS2 and BS3 whereat the electron beams are incident, as they are not deflected by the deflector 306. These beam reference positions BS1-BS3 are placed along a design orthogonal coordinate system (Xs, Ys). [0012] On the other hand, the electron beams are scanned (scanningly deflected) also along a design orthogonal coordinate system (Xs, Ys) while taking the beam reference positions as a reference, to scan associated exposure fields EF1, EF2 and EF3, respectively. In this stage, the stage which carries the wafer 350 thereon is scanningly moved mainly in the Y direction, as denoted at 200 in FIG. 13, to perform sequential exposures of zones of the wafer. SUMMARY OF THE INVENTION [0013] Enlargement of the wafer diameter has been required in lithography, and thus, the stroke of the apparatus should be enlarged. In the example of FIG. 10, there is a difficulty in setting the orthogonality of confining axes for confining each of the X and Y sliders at opposite sides. This leads to a difficulty in improvement of the precision or enlargement of the stroke. [0014] In the example of FIG. 11, on the other hand, if there is a tilt of a base table, for example, it may cause unwanted motion in the X or Y direction. Furthermore, the arrangement itself cannot be used in a vacuum ambience. [0015] It is accordingly an object of the present invention to provide a high-precision stage system that can meet enlargement of the stroke. [0016] In accordance with an aspect of the present invention, to achieve this object, there is provided a stage system, comprising a first fixed guide having a first guide surface being parallel to or approximately parallel to a first direction and a second direction being orthogonal to or approximately orthogonal to the first direction, a first movable guide to be guided by the first fixed guide and having three freedoms of movement of straight motions in the first and second directions and a motion in a rotational direction about a third direction being orthogonal to or approximately orthogonal to the first and second directions, the first movable guide having a first guide extending in the second direction, a second fixed guide having a second guide surface being parallel to or approximately parallel to the first and second directions, a second movable guide to be guided by the second fixed guide and having three freedoms of movement of straight motions in the first and second directions and a motion in a rotational direction about the third direction, the second movable guide having a second guide extending in the first direction, and a central movable member to be guided in the first and second directions by means of the first and second guides. [0017] In accordance with another aspect of the present invention, there is provided a stage system comprising a first fixed guide having a first guide surface being parallel to or approximately parallel to a first direction and a second direction being orthogonal to or approximately orthogonal to the first direction, a first movable guide to be guided by the first fixed guide and having a first guide extending in the second direction, a second fixed guide having a second guide surface being parallel to or approximately parallel to the first and second directions, a second movable guide to be guided by the second fixed guide and having a second guide extending in the first direction, a third fixed guide having a third guide surface being parallel to or approximately parallel to the first and second guide surfaces, and a central movable member to be guided in the first and second directions by means of the first and second guides, and also to be guided by the third fixed guide in a third direction being orthogonal to or approximately orthogonal to the first and second directions, wherein the central movable member is attracted to the third fixed guide by means of a permanent magnet unit having a magnetic shield. [0018] In accordance with the present invention, a high-precision stage system that can meet enlargement of the stroke can be accomplished. Further, since the fixed guide (guide surface) is divided into plural guides, even if a magnetic preload is used, magnets can be magnetically shielded effectively. Thus, the stage system can be well incorporated into an electron beam exposure apparatus. [0019] These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0020] FIG. 1 is a schematic view of a main portion of an electron beam exposure apparatus according to an embodiment of the present invention. [0021] FIG. 2 is a perspective view of a main portion of a stage system in the FIG. 1 embodiment. 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