US20010023927A1

US20010023927A1 - Reaction force isolation system for a planar motor

Info

Publication number: US20010023927A1
Application number: US09/870,518
Authority: US
Inventors: Andrew Hazelton
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 1998-08-14
Filing date: 2001-06-01
Publication date: 2001-09-27
Also published as: EP1105780A4; WO2000010058A9; US6252234B1; JP2002522914A; US20010020684A1; AU5674399A; WO2000010058A1; EP1105780A1

Abstract

The present invention provides a structure for isolating the reaction forces generated by a planar motor. Specifically, the fixed portion of the reaction motor, which is subject to reaction forces, is structurally isolated from the rest of the system in which the planar motor is deployed. In accordance with one embodiment of the present invention, the fixed portion of the planar motor is separated from the rest of the system and coupled to ground. The rest of the system is isolated from ground by deploying vibration isolation means. Alternatively or in addition, the fixed portion of the planar motor may be structured to move (e.g., on bearings) in the presence of reaction forces, so as to absorb the reaction forces with its inertia. In a further embodiment of the present invention, the fixed portion of the planar motor and the article to be moved are supported by the same frame, with the fixed portion of the planar motor movable on bearings.

Description

BACKGROUND OF THE INVENTION

This is a continuation-in-part of U.S. patent application Ser. No. 09/134,278, filed Aug. 14, 1998.

1. Field of the Invention

The present invention relates, in general, to planar motor driven positioning systems, and more particularly to such method and apparatus for positioning and aligning a wafer in a photolithographic system using a planar motor and isolating the system from the reaction forces of the planar motor.

2. Related Background Art

Various support and positioning structures are available for positioning an article for precision processing. For example in semiconductor manufacturing operations, a wafer is precisely positioned with respect to a photolithographic apparatus. In the past, planar motors have been advantageously utilized to position and align a wafer stage for exposure in the photolithographic apparatus. For example, U.S. Pat. Nos. 4,535,278 and 4,555,650 to Asakawa describe the use of planar motors in a semiconductor manufacturing apparatus.

A semiconductor device is typically produced by overlaying or superimposing a plurality of layers of circuit patterns on the wafer. The layers of circuit patterns must be precisely aligned. Several factors may cause alignment errors. Vibrations of the structures within the photolithographic system could cause misalignment of the wafer. The reaction forces between the moving portion and fixed portion of the planar motor are known to induce vibrations in the system.

As the semiconductor manufacturing industry continues to try to obtain increasingly tighter overlays due to smaller overlay budgets and finer conductor widths, the importance of alignment has been magnified. Precise alignment of the overlays is imperative for high resolution semiconductor manufacturing. It is therefore desirable to develop a means to reduce the effect of vibrations caused by the planar motor.

SUMMARY OF THE INVENTION

The present invention provides a structure for isolating the vibrations induced by reaction forces generated by a planar motor. Specifically, the fixed portion of the reaction motor, which is subject to reaction forces, is structurally isolated from the rest of the system in which the planar motor is deployed. This can be done in a number of ways.

In accordance with one embodiment of the present invention, the fixed portion of the planar motor is separated from the rest of the system and coupled to ground. The rest of the system is isolated from ground by deploying a vibration isolation system. Alternatively or in addition, the fixed portion of the planar motor may be structured to move (e.g., on bearings) in the presence of reaction forces, so as to absorb the reaction forces with its inertia.

In a further embodiment of the present invention, the fixed portion of the planar motor and the article to be moved are supported by the same frame, with the fixed portion of the planar motor movable on bearings.

In another aspect of the present invention, a reaction force isolation system is structured more specifically for a two-sided planar motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a planar motor driven scanning type exposure system that implements a reaction force isolation system in accordance with one embodiment of the present invention. [0012]
FIG. 2 is a schematic exploded view of one embodiment of the planar motor adopted in the system in FIG. 1. [0013]
FIG. 3 is a schematic representation of the projection exposure system that implements another embodiment of planar motor reaction force isolation system in which the coil array is supported on bearings. [0014]
FIG. 4 is a schematic representation of the projection exposure system that implements yet another embodiment of the reaction force isolation system of the present invention in which the top plate of the planar motor is supported by a frame. [0015]
FIG. 5 is a schematic representation of the projection exposure system in which the reaction force isolation system is a variation of the embodiment in FIG. 4. [0016]
FIG. 6 is a schematic representation of the projection exposure system that implements a reaction force isolation system in which the top plate of the planar motor and the coil array that rides on a bearing are supported on a common support frame. [0017]
FIG. 7 is a schematic representation of a further embodiment of the reaction force isolation system of the present invention which also shows a wafer leveling stage and the planar motor is cooled by coolant. [0018]
FIG. 8 is a schematic representation of a two-sided planar motor driven scanning type exposure system that implements a reaction force isolation system in accordance with another embodiment of the present invention, in which the plate and coil assembly is supported on bearings. [0019]
FIG. 9 is a schematic perspective view of the two-sided planar motor adopted in the system in FIG. 8. [0020]
FIG. 10 is a schematic exploded view of the two-sided planar motor in FIG. 9. [0021]
FIG. 11 is a schematic side view of the two-sided planar motor in FIG. 9. [0022]
FIG. 12 is a schematic representation of the exposure system that implements another embodiment of the reaction force isolation system for a two-sided planar motor, in which the coil and plate assembly is attached to ground. [0023]

DETAIL DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. [0024]
To illustrate the principles of the present invention, the isolation of vibrations induced by reaction forces generated by a planar motor is described in reference to a scanning-type photolithography system for substrate processing. However, it is understood that the present invention may be easily adapted for use in other types of exposure systems for substrate processing (e.g., projection-type photolithography system or electron-beam (EB) photolithography system disclosed in U.S. Pat. No. 5,773,837) or other types of systems (e.g. pattern position measurement system disclosed in U.S. Pat. No. 5,539,521, wafer inspection equipment, machine tools, electron beam, microscope) for processing other articles in which the reduction of vibrations induced by reaction forces generated in a planar motor is desirable without departing from the scope and spirit of the present invention. [0025]
FIG. 1 is a schematic representation of a scanning-[0026] type exposure system 10 for processing a substrate, such as a wafer 12, which implements the present invention. In an illumination system 14, light beams emitted from an extra-high pressure mercury lamp are converged, collimated and filtered into substantially parallel light beams having a wavelength needed for a desired exposure (e.g., exposure of the photoresist on the wafer 12). Of course, in place of the mercury lamp, g-line (436 nm), i-line (365 nm), Krf (248 nm), Arf (193 nm) or F2 (157 nm) excimer laser can be used. (Glass material that transmit far ultra-violet rays of the excimer laser, such as quartz and fluorite, should be used. For F2 laser, the optical system should be either catadioptric or refractive, and the reticle should be a reflective type.)
The light beams from the [0027] illumination system 14 illuminates a pattern on a reticle 16 that is mounted on a reticle stage 18. The reticle stage 18 is movable in several (e.g., three to six) degrees of freedom by servomotors or linear motor (not shown) under precision control by a driver 20 and a system controller 22. The structure of the reticle stage 18 is disclosed in U.S. application Ser. No. 08/698,827. The light beams penetrating the reticle 16 are projected on the wafer 12 via projection optics 24.
The [0028] wafer 12 is held by vacuum suction on a wafer holder (not shown) that is supported on a wafer stage 26 under the projection optics 24. The wafer stage 26 is structured so that it can be moved in several (e.g., three to six) degrees of freedom by a planar motor 30 (see also FIG. 2) under precision control by the driver 32 and system controller 22, to position the wafer 12 at a desired position and orientation, and to move the wafer 12 relative to the projection optics 24. The driver 32 may provide the user with information relating to X, Y and Z positions as well as the angular positions of the wafer 12 and the driver 20 may provide user with information relating to the position of the reticle 16.
For precise positional information, [0029] interferometers 34 and 36 and mirrors 35 and 37 are provided for detecting the actual positions of the reticle and wafer, respectively, as schematically shown in FIG. 1. For either or each of the wafer stage and reticle stage, a set of three interferometers may be provided for detecting the and X, Y and θ positions of the wafer stage and/or reticle stage, so as to provide positional information that can be used to drive the wafer stage and/or reticle stage in the X, Y and θ directions. Furthermore, it is also acceptable to install interferometers at three locations for detecting the position of either the wafer stage or the reticle stage and drive the wafer stage or the reticle stage in three directions (e.g., X, Y, and 0) in accordance with the output from each of the interferometers.
In the scanning-type exposure apparatus, the [0030] reticle 16 and the wafer 12 are scanned and exposed synchronously (in accordance with the image reduction in place) with respect to an illumination area defined by a slit having a predetermined geometry (e.g., a rectangular, hexagonal, trapezoidal or arc shaped slit). This allows a pattern larger than the slit-like illumination area to be transferred to a shot area on the wafer 12. After the first shot area has been completed, the wafer 12 is stepped by the planar motor 30 to position the following shot area to a scanning start position. This system of repeating the stepping and scanning exposure is called a step-and-scan system. The scan-type exposure method is especially useful for imaging large reticle patterns and/or large image fields on the substrate, as the exposure area of the reticle and the image field on the wafer are effectively enlarged by the scanning process.
It is again noted that the configuration of the [0031] exposure system 10 described above generally corresponds to a step-and-scan exposure system that is known in the art. Further detail of the components within a scanning-type exposure apparatus may be referenced from U.S. Pat. No. 5,477,304 to Nishi and U.S. Pat. No. 5,715,037 to Saiki et al. (assigned to the assignee of the present invention, which are fully incorporated by reference herein. It is to be understood that the present invention disclosed herein is not to be limited to wafer processing systems, and specifically to step-and-scan exposure systems for wafer processing. The general reference to a step-and-scan exposure system is purely for illustrating an embodiment of an environment in which the concept of isolation of planar motor reaction forces to reduce system vibration may be advantageously adopted.
As illustrated in the FIG. 1, the [0032] illumination system 14, the reticle stage 18 and the projection optics 24 are separately supported by frames 38, 40 and 42, respectively. The frames are coupled to the “ground” (or the surface on which the overall exposure system is supported). As will be noted below, the frames 38, 40 and 42 may be coupled to the ground by means of vibration isolation systems and the like.
Referring also to FIG. 2, the components of the [0033] planar motor 30 are schematically illustrated. The planar motor 30 comprises an array 50 of magnetic coils that are electrically energized under control of the driver 32. A top plate 52 is positioned above the coil array 50. The top plate 52 may be made of non-magnetic materials, for example, carbon fiber plastics, ceramics such as Zerodur ceramics, Al2O3 ceramics, and the like materials that do not impair the magnetic flux of permanent magnets 56. The wafer stage 26 rests on the top plate 52 (preferably in the presence of an air bearing). The underside of the wafer stage 26 has an array of permanent magnets 56 configured to interact with the coil array 50 to produce forces in the X, Y and θ directions to move the wafer stage 26 across the top plate 52. Consequently, a reaction force acts on the coil array 50. According to the present invention, this reaction force is isolated from the rest of the exposure system 10.
For simplicity, many details of the planar motor are omitted from the FIG. 2, as they alone do not constitute a part of the present invention. Structural details and operational principles of planar motors may be referenced to the prior art, such as the U.S. Pat. Nos. 4,535,278 and 4,555,650 to Asakawa, which are fully incorporated by reference herein. [0034]
In the embodiment shown in FIG. 1 and further illustrated in FIG. 2, the [0035] top plate 52 is supported on support posts 54 that project through clearance holes in the coil array 50. The support posts 54 rest on a base 58 to prevent it from bending. Alternately, the top plate 52 and the support posts 54 may be a unitary structure. The base 58 is coupled to the ground by damping means 60, such as air or oil dampers, voice coil motors, actuators or other known vibration isolation systems. Similarly, the frames 38, 40 and 42 may be coupled to the ground by similar damping means. The coil array 50 is separately and rigidly coupled to the ground by fixed stands 62. In this embodiment, when reaction forces are created between the coil array 50 and the wafer stage 26, the reaction forces push against the ground. Because of the large mass of the ground, there is very little movement of the coil array 50 from the reaction forces. By providing damping means 60 to couple the base 58 and the frames 38, 40 and 42 to the ground, any vibration that may be induced by the reaction forces through the ground is isolated from the rest of the system 10.
Referring to FIG. 3, instead of rigidly coupling the coil array to the ground, a bearing coupling may be used. For example, a planar (X, Y and Theta Z) journal bearing [0036] 64 may be provided at the end of the supports 66. Ball bearings and air bearings may also be used. When reaction forces are created by the coils between the wafer stage 26 and the coil array 50, both the wafer stage 26 and the coil array 50 move in opposite directions. The mass of the coil array 50 is typically substantially larger than that of the wafer stage 26. Consequently, in accordance with conservation of momentum, the movement of the coil array 50 caused by the reaction force is typically substantially smaller than the movement of the wafer stage 26 under the same reaction force. The inertia of the coil array 50 would absorb the reaction forces. It is to be understood that in the embodiment of FIG. 3, the damping means 60 may be omitted if the bearing support can effectively isolate all reaction forces that may induce vibrations in the rest of the system 10.
In another embodiment of the present invention as illustrated in FIG. 4, the [0037] coil array 50 is rigidly supported on the ground on supports 62. In this embodiment, instead of supporting the top plate 52 of the planar motor 30 on support posts 54 on the base 58 as was done in the earlier embodiments, the top plate 52 is supported by frame 42. The invention as illustrated in FIG. 4 does not have the support posts 54. Therefore the top plate 52 may be formed with a thick honeycomb structure or other types of reinforced structure to prevent it from bending. The frame 42 is isolated from vibration transmitted through the ground by damping means 60.
FIG. 5 illustrates another configuration in which the [0038] top plate 52 is supported by frame 42. Unlike FIG. 4 in which the top plate 52 is supported at its ends by the side members 43 of frame 42, the top plate 52 is supported to the top member 45′ of the frame 42′. The coil array 50 remains rigidly supported to the ground as in FIG. 4. The frame 42′ is mounted on the supports 47 using damping means 60′. The center of gravity of the system 10 is lower in reference to the damping means 60′. So the system 10 in FIG. 5 is less susceptible to vibration than that in FIG. 4. Additionally, in FIG. 5, frames 38′ and 40′ may be mounted on the frame 42′ to avoid the need for additional damping means, as the damping means 60′ isolates the combined structures 38′, 40′ and 42′. The damping means 60′ prevents the vibration of the ground from transmitting to the projection optics 24, the illumination system 14 and the reticle 16. The system 10 in FIG. 5 is more compact, but the center of gravity of the system 10 shifts depending on the position of the wafer stage 26. Therefore, it is preferred that the damping means 60′ includes an actuator (schematically shown at 61) that maintains the frame 42′ level so as to prevent misalignment of the optical axes of the projection optics 24 and the illumination system 14. The actuator and positional feedback scheme needed to achieve the leveling objective may be implemented using known art.
As a further variation of the embodiments of FIGS. 4 and 5, bearing supports may be utilized to support the [0039] coil array 50, for the same reasons as for the embodiment of FIG. 3.
In yet another embodiment of the present invention as illustrated in FIG. 6, both the [0040] top plate 52 and the coil array 50 are supported by the frame 42′. Specifically, the top plate 52 is attached to the mid sections of the vertical members 70 that depend from the top member 45′ of the frame 42′. A horizontal support platform 72 is attached to the ends of the vertical members 70. The coil array 50 rides on bearings 74 (e.g. an air or ball bearings) on the horizontal support platform 72. With this embodiment, the reaction forces would cause the coil array 50 to move sideways on its bearings 74, thus absorbing the reaction forces with its inertia. In FIG. 6, frames 38′ and 40′ may be mounted on the frame 42′ without additional damping means as in FIG. 5. In addition, the reaction forces can be absorbed during the exposure process, because reaction forces are very small compared to the weight of the system 10 that comprises the projection optics 24, wafer stage 26, the reticle stage 18 and the illumination system 14.
The invention of FIG. 6 uses the principle of momentum conservation, so the center of gravity of the [0041] system 10 does not shift according to the position of the wafer stage 26. Therefore damping means 60′ of this invention does not need an actuator (compared to the embodiment in FIG. 5.)
FIG. 7 shows a variation of the embodiment of FIG. 6. The [0042] planar motor 30 includes a cooling platform 76 that is supported by the horizontal support platform 72. The cooling platform 76 includes conduits 78 through which coolant 77 can pass through. Alternatively, Peltier cooling or ventilating air cooling may be deployed. The top plate 52 is supported on stands 80 that are supported on the cooling platform 76. The cooling platform 76 provides a support surface on which the coil array 50 rests on bearings 74. Further wafer stage 26 includes a leveling stage 83 that positions the wafer 12 in three additional degrees of freedom. The leveling stage 83 has at least three actuators 84, e.g. voice coil motors, which actuate in the direction of the axis of projection optics 24 in accordance with focus sensors 82 a and 82 b. The focus sensor 82 a emits a focusing beam to the wafer 12 and the focus sensor 82 b receives the reflected beam from the wafer 12. The leveling stage 83 can adjust the focal plane of the projection optics 24 to align with the surface of the wafer 12. It is preferable that the leveling stage 83 is structurally isolated (without mechanical contact) on the wafer stage 26 so that the vibration of the wafer stage 26 (e.g., caused by the air bearing) may be isolated.
The above-described embodiments are all directed to exposure systems that deploy a planar motor that is driven by magnetic interactions on one side (the bottom side as illustrated in the drawings) of the moving portion. In certain exposure systems, it is desirable to deploy a two-sided planar motor in which the moving portion is driven by magnetic interactions on both sides (top and bottom sides) of the moving portion. [0043]
FIG. 8 shows an [0044] exposure system 100 in which a two-sided planar motor 102 is deployed. As illustrated, except for the configuration of the planar motor 102 and reaction force isolation structure, the exposure system 100 is fumdamentally similar to the earlier embodiments, such as FIG. 6.
Referring to FIGS. [0045] 9 to 11, the components of the two-sided planar motor 102 are schematically illustrated. The two-sided planar motor 102 comprises two planar coil arrays 104 and 106 (hidden from view in FIGS. 8 and 9). The array 104 is supported on a bottom plate 108, and the array 106 is supported on a top plate 110. The top plate 110 and the bottom plate 108 are separated by posts 112 to define a space 115 in which the moving portion of the planar motor 102, i.e., a wafer stage 114, is free to move in a plane. The bottom and top plates 108 and 110 and the posts 112 form a rigid assembly (hereinafter referred to as the plate assembly 113). The wafer stage 114 has complimentary permanent magnet arrays 116 and 118 on the top and bottom sides of the wafer stage 114. The wafer stage 114 supports a wafer 12. The top plate 110 is provided with an opening 111 to allow illumination to be directed at the wafer 12.
For simplicity, many details of the two-sided [0046] planar motor 102 are omitted from the drawings, as they alone do not constitute a part of the present invention. Structural details and operational principles of two-sided planar motors may be referenced to the copending patent application Ser. No. ______, filed ______ (docket PA0225-US); patent application Ser. No. 09/192,813, filed Nov. 16, 1998 (docket PA0162-US); and U.S. patent application Ser. No. ______ , filed ______ (docket PA0221-US), which are fully incorporated by reference herein.
In the embodiment shown in FIGS. [0047] 8 to 10, the plate assembly 113 of the planar motor 102 is supported on a bearing system supported on a base 122. (While the bearing system are schematically represented as ball bearings 120, it is understood that the bearing system may be air bearings or some other bearing technology without departing from the scope and spirit of the present invention.) Referring to FIG. 8, the base 122 is supported from a fixed body 124 of the exposure system 100 by support posts 126. The body 124 supports the projection optics 24 such as projection lenses. An appropriate opening 128 is provided on the body 124 and aligned with opening 111 on the top plate 110 to allow illumination to be directed to the wafer 12 that is supported on the wafer stage 114.
When the [0048] magnetic coil arrays 104 and 106 are energized under control of the driver 32, a magnetic force moves the wafer stage 114 about in the space 115 of the plate assembly 113 to position the wafer 12 with respect to the projection optics 24. The force on the wafer 114 causes a reaction force on the plate assembly 113. It is noted that the system illustrated in FIG. 8 consists of a fixed body 124 of the exposure system 100, and moving plate assembly 113 and wafer stage 114. Because the plate assembly 113 is free to move due to the bearing system 120, it moves in the opposite direction of the wafer stage 114 as governed by the principle of conservation of momentum. If the mass of the plate assembly 113 is significantly higher than the mass of the wafer stage 114 (which is typically the case), the travel of the plate assembly 113 due to the reaction force will be significantly less than that of the wafer stage 114. As in the earlier embodiments, because all of the momentum is conserved between the wafer stage 114 and the plate assembly 113, the body of the exposure system 100 will not move. This means that no vibrations or other forces will enter the body due to the wafer stage motion. In effect, the reaction force of the wafer stage 114 is absorbed in the inertia of the plate assembly 113.
FIG. 12 illustrates another embodiment of reaction force isolation for a two-sided planar motor in an exposure system [0049] 100 (for simplicity, many parts of the exposure system 100 have been omitted from the drawing). In this embodiment, the plate assembly 113 is attached or supported directly to ground 130 as the base. The body 124′ of the exposure system which supports the projection optics 24 is also supported to ground 130.
In this configuration, the momentum of the [0050] wafer stage 114 is conserved between it and the ground 130. Because the mass of the ground 130 is significantly higher than the mass of the wafer stage 114, the motion of the ground 130 from the reaction force of the wafer stage 114 is negligible. Higher frequency components of the wafer stage motion (e.g., vibrations), however, can be transmitted in the ground 130. To prevent these from being transmitted to the body 124′ of the exposure system, the body 124′ is isolated from the ground 130 using a vibration isolation system 132, such as the damping means 60′ in the earlier embodiments. Vibration isolation systems are commercially available, for example, from Barry Controls, Brighton, Mass.
It is appreciated that the exposure systems described in the foregoing embodiments can be built by assembling various subsystems, including the planar motor, projection optics, illumination system, positioning control system, and vibration isolation system. The subsystems are assembled in a manner that optimizes the mechanical accuracy, electrical accuracy and optical accuracy. In order to maintain various accuracy of the various subsystems, every optical system is adjusted to achieve it optical accuracy, every mechanical system is adjusted to achieve its mechanical accuracy, and every electrical system is adjusted to achieve its electrical accuracy before and after its assembly. The process of assembling each subsystem into an exposure system includes mechanical connections, electrical circuit wiring connections and air pressure plumbing connections. Each subsystem may be assembled prior to integrating the subsystems to construct the exposure system. Once the exposure system is assembled with various subsystems, overall adjustment is performed so as to optimize the individual subsystem accuracy as well as overall system accuracy. The exposure shall preferably be manufactured and assembled in a clean room environment. [0051]
While the general process for manufacturing semiconductor devices using the exposure system of the present invention have not been described in detail, it is understood that one skilled in the art can readily apply the exposure system to the fabrication of semiconductor devices by conventional procedures, which may include the steps of designing the device functions and performance, designing the reticle, fabricating the wafer, exposing the reticle pattern on the wafer using the exposure system of the present invention, assembling the device (including dicing, bonding, and packaging processes), and inspection and quality control. [0052]
While the invention has been described with respect to the described embodiments in accordance therewith, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, in the above embodiments of FIGS. 1, 3 and [0053] 4, frames 38, 40 and 42 are separately coupled to the ground. Alternatively, frames 38 and 40 can be mounted on the frame 42 without damping means as in FIGS. 5 and 6. Conversely, the frames 38′, 40′ and 42′ in the embodiments of FIGS. 5, 6, 7 and 8 may be separately supported on damping means as in FIGS. 1, 3 and 4. The above embodiments of FIGS. 1, 3, 4 and 5 also may be implemented with focus sensors 82 and the leveling stage 83. Additionally, various combinations of damping means and bearing support may be deployed to provide the reaction force isolation function, and/or to provide redundancy in such function.
While the foregoing embodiments have been described with reference to planar motors that have a coil array on the moving portion of the planar motor and magnets on the fixed portion of the planar motor, it is to be understood that the coil array may be provided on the moving portion and the magnets may be provided on the fixed portion instead, without departing from the scope and spirit of the present invention. [0054]
The structure of the planar motor was explained as having a coil array on the fixed part side and magnets on the moving part side, but the arrangement could be other way around. In other words, magnets can be placed on the fixed part side, and the coil array can be placed on the moving part side. [0055]
Furthermore, although the wafer stage employing a planar motor was explained as an example, the present invention is also applicable to the case where a planar motor is employed in a reticle stage. In that case, an opening as shown in FIG. 8-[0056] 12 should be made in a reticle stage where a planar motor is mounted so that the illumination from the illumination system 14 can be transmitted through the reticle 16 and intercepted by the wafer 12.
In each of the embodiments, a scanning-type exposure system, where a mask and a wafer are moving synchronously to expose a mask pattern, was used as an example. However, it does not have to be limited to this. For instance, the present application is also applicable to a step-and-repeat-type exposure system, where a mask pattern is exposed while the mask and the wafer are stationary, and the wafer is stepped and moved in order of succession. [0057]
Furthermore, it is also applicable to a proximity exposure system, where a mask pattern is exposed by closely placing the mask and the wafer, without using projection optics. [0058]
The use of the exposure system does not need to be limited to semiconductor manufacturing: for instance, it can be widely applied to an LCD exposure system, where LCD pattern is exposed onto a rectangular glass plate, or an exposure system for manufacturing a thin film magnetic head. [0059]
In terms of the light source for the exposure system according to the present embodiment(s), not only the g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm), and he F2 laser (157 nm) but also charged particle beams such as the x-ray and electron beams can be used. If an electron beam is used, thermionic emission type lanthanum hexaboride (LaB6) or tantalum (Ta) can be used as an electron gun. Furthermore, when an electron beam is used, the structure could use a mask, or it could be structured such that a pattern can be formed directly onto a wafer without using a mask. [0060]
In terms of the magnification of the projection optical system, it does not have to be limited to a reduction system: it could be 1× or a magnification system as well. [0061]
With respect to the projection optical system, when far ultra-violet rays such as the excimer laser is used, glass materials that transmit far ultra-violet rays such as quartz and fluorite should be used: when the F2 laser or the x-ray is used, the optical system should be either catadioptric or refractive (the reticle should be a reflective type), and when an electron beam is used, electron optics should consist of electron lenses and deflectors. It is needless to say that the optical path for electron beams should be in vacuum. [0062]
When linear motors (see U.S. Pat. No. 5,623,853 or U.S. Pat. No. 5,528,118) are used in a reticle stage, they could be either the air levitation type using air bearings or the magnetic levitation type using the Lorentz force or reactance force. In addition, the reticle stage could move along a guide, or it could be a guideless type where no guide is installed. [0063]
Reaction force generated by the reticle stage motion can be mechanically released to the ground by using a frame member, as described in JP Hei 8-330224 published patent (U.S. Ser. No. 08/416,558). [0064]
As described above, the exposure system according to the embodiments of the present application can be built by assembling various subsystems, including the elements listed in the claims of the present application, in the manner that prescribed mechanical accuracy electrical accuracy and optical accuracy are maintained. In order to maintain various accuracy of various subsystems, every optical system is adjusted to achieve its optical accuracy, every mechanical system is adjusted to achieve its mechanical accuracy and every electrical system is adjusted to achieve its electrical accuracy before and after its assembly. The process of assembling each subsystem into an exposure system includes mechanical interface, electrical circuits' wiring connections and air pressure plumbing connections. It is needless to say that there is a process where each subsystem is assembled prior to assembling the exposure system from various subsystems. Once the exposure system is assembled with various subsystems, total adjustment is performed so as to make sure that every accuracy is maintained in the total system. Incidentally, it is desirable to manufacture an exposure system in a clean room where the temperature and the cleanliness are controlled. [0065]
Semiconductor devices are fabricated by going through the following steps: the step where the device's function and performance are designed; the step where a reticle is designed according to the previous designing step; the step where a wafer is made from a silicon material; the step where the reticle pattern is exposed on a wafer by the exposure system in the aforementioned embodiments; the step where device is assembled (including the dicing process, bonding process and packaging process); and the inspection step, etc. [0066]
The planar motors described above may also be implemented for actuation of the reticle stage. For example, for the embodiments of FIGS. [0067] 8-12, a suitable opening is provided in the two-sided planar motor installed in the reticle stage so that illumination from the illumination system 14 can transmit through the reticle 16 to be projected onto the wafer 12. When linear motors (see U.S. Pat. No. 5,623,853 and U.S. Pat. No. 5,528,118) are used in a reticle stage, they could be based on air levitation by air bearings or magnetic levitation by Lorentz force or reactance force. In addition, the reticle stage could move along a guide or without a guide. Reaction force generated by the reticle stage motion can be mechanically released to the ground by using a frame member, as described in published JP patent applicatioin JP Hei 8-330224.
Further, the present invention is not limited to scanning type exposure system. For example, the present invention may be adopted in other types of exposure apparatus, such as a step-and-repeat type exposure system in which a pattern is exposed in successive sections of the mask and the wafer remain stationary. Instead of applying to a reduction projection optical system, the present invention may also be applied to a magnification projection optical system, including a 1× magnification system. The present invention may also be adopted in a proximity exposure system, in which a mask closely positioned with the wafer is exposed without using projection optics. [0068]
The present invention is not limited to semiconductor manufacturing. The present invention may be applicable to other types of processing systems in which precision positioning utilizing a planar motor is desired. For example, it may be applied to exposure systems for the manufacture of LCD panels, in which a pattern is exposed onto a rectangular glass plate. It may also be applied to exposure systems for the manufacture of thin film magnetic heads. [0069]
Exposure systems not using illumination may also take advantage of the present invention. For example, the present invention may be applied to systems that use charged particle beams such as X-ray beams and electron beams. If an electron beam is used, thermionic emission type lanthanum hexaboride (LaB[0070] ₆) or tantalum (Ta) can be used as the source of an electron beam. Furthermore, when an electron beam is used, the exposure system could use a mask, or it could be structured such that a pattern can be formed directly onto a wafer without using a mask. Electron optics for the exposure system should consist of electron lenses and deflectors. The optical path for the electron beams should be contained a vacuum environment. If a X-ray beam is used, the optical system should be either catadioptric or refractive (the reticle should be a reflective type).
While the described embodiment illustrates planar motors used in an X-Y plane, planar motors used in other orientations and having more or less dimensions may be implemented with the present invention. [0071]
Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims. [0072]

Claims

1. A stage device, comprising:

a planar motor which has a fixed portion and a moving portion, wherein said moving portion supports an article for movement in a plane of the planar motor; and

a vibration isolation structure structured and configured to isolate vibration induced by a reaction force between said moving portion and said fixed portion.

2. A stage device according to

claim 1

, wherein said moving portion is supported on a stationary support, and said vibration isolation structure includes a structure in which said fixed portion is structurally independent of said stationary support.

3. A stage device according to

claim 2

, wherein said fixed portion is supported on a bearing.

4. A stage device according to

claim 3

, wherein said bearing comprises an air bearing and/or a ball bearing.

5. A stage device according to

claim 2

, wherein said vibration isolation structure further comprises a vibration isolation device that supports said stationary support.

6. A stage device according to

claim 5

, wherein said vibration isolation device includes an air damper and/or an actuator.

7. A stage device according to

claim 2

, wherein said stationary support comprises a top plate on which the moving portion is supported for movement and a base, and said fixed portion is located between said top plate and said base.

8. A stage device according to

claim 7

, wherein said fixed portion includes a coil array.

9. A stage device according to

claim 7

, wherein said top surface is made of a non-magnetic material.

10. A stage device according to

claim 7

, wherein the stationary support further comprises a support structure between said top plate and said base for keeping said top plate from bending.

11. A stage device according to

claim 2

, wherein said moving portion moves on a bearing surface.

12. A stage device according to

claim 11

, wherein said bearing surface includes an air bearing.

13. A stage device according to

claim 2

, further comprising a control device for controlling the positions of said moving portion at least in two directions.

14. A stage device according to

claim 13

, wherein said fixed portion includes a coil array, and said control device includes a driver unit for supplying a current to said coil array to move the moving portion.

15. A stage device according to

claim 13

, further comprising at least two interferometers, wherein said control devise controls the positions of said moving portion based in part on the outputs of said interferometers.

16. A stage device according to

claim 13

, further comprising at least three interferometers, wherein said control device controls the X, Y and θ positions of said movable stage based in part on the outputs of said interferometers.

17. A stage device according to

claim 1

, wherein said moving portion includes a permanent magnet.

18. A stage device according to

claim 2

, wherein said stationary support includes a platform on which the moving portion is supported for movement and a frame that supports said platform, and wherein said fixed portion is located beneath said platform.

19. A stage device according to

claim 18

, wherein said frame is supported on a damping device.

20. A stage device according to

claim 19

, wherein said damping device comprises an actuation means for maintaining the frame level against any changes induced by a change in center of gravity.

21. A stage device according to

claim 1

, wherein said fixed portion and said moving portion are supported by a same frame, and wherein the fixed portion is supported on a bearing.

22. A stage device according to

claim 21

, wherein said frame is supported on a damping device.

23. A stage device according to

claim 21

, wherein the moving portion comprises a leveling stage for leveling said article.

24. A stage device according to

claim 21

, wherein the frame comprises a platform on which the fixed portion is supported, and means for cooling said platform.

25. A stage device according to

claim 1

, wherein said fixed portion comprises a first magnetic portion and a second magnetic portion spaced apart to define a space in which said moving portion moves laterally.

26. A stage device according to

claim 25

, wherein said vibration isolation structure comprises a bearing system that supports said second magnetic portion for lateral movement in reaction to movement of said moving portion.

27. A stage device according to

claim 26

, wherein said first magnetic portion and second magnetic portion form a rigid structure resting on the bearing system.

28. A stage device according to

claim 27

, wherein at least one of said first magnetic portion and second magnetic portion comprises a magnetic coil array for effecting movement of the moving portion in said space.

29. A stage device according to

claim 25

, wherein said fixed portion is fixedly supported, and said vibration isolation structure comprises a structure in which said fixed portion is structurally independent of an external support structure.

30. A stage device according to

claim 29

, wherein said vibration isolation structure comprises a damper to damp the vibration to said external support structure induced by said reaction force interaction between said moving portion and said fixed portion.

31. An exposure apparatus, comprising:

an optical system for imaging a mask pattern onto an article;

a stage device for precise positioning of the article for imaging, said stage device comprising:

a planar motor which has a fixed portion and a moving portion, wherein said moving portion supports said article for movement in a plane of the planar motor; and

a vibration isolation structure structured and configured to isolate vibration that is induced by a reaction force between said moving portion and said fixed portion.

32. An exposure apparatus according to

claim 31

, further comprising means for scanning said mask pattern in synchronization with movement of said article.

33. An exposure apparatus according to

claim 32

, wherein said mask pattern is a circuit pattern for a semiconductor device and wherein said article to be exposed is a wafer.

34. An exposure apparatus according to

claim 31

35. An exposure apparatus according to

claim 34

, wherein said vibration isolation structure comprises a bearing system that supports said fixed portion for lateral movement in reaction to movement of said moving portion.

36. An exposure apparatus according to

claim 35

, wherein said bearing system is supported by a frame structure that supports said optical system in relation to said article.

37. An exposure apparatus according to

claim 34

, wherein said optical system is supported on a frame structure, said fixed portion is fixedly supported, and said vibration isolation structure comprises a structure in which said frame structure is structurally independent of said fixed portion.

38. A method of controlling reaction force induced vibration in a stage device, comprising the steps of:

providing a planar motor which has a fixed portion and a moving portion;

supporting an article on said moving portion for movement in a plane of the planar motor; and

providing a vibration isolation structure that is structured and configured to isolate vibration induced by a reaction force between said moving portion and said fixed portion.