Abstract:
A positioning apparatus is disclosed. The positioning apparatus comprises first and second bases, and two moving elements which are guided by the first and second bases to move on the first and second bases. A distance is ensured between the first and second bases. When the two moving elements move between the first and second bases, both of a guide surface of the first base and a guide surface of the second bases are used.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a positioning apparatus for positioning two moving elements, an exposure apparatus into which the positioning apparatus is built, and a device manufacturing method which uses the exposure apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the manufacture of various types of devices such as semiconductor devices, an exposure apparatus which forms a latent pattern on a photosensitive agent applied to a substrate is used. The latent pattern is patterned in a later developing step. One of the important factors in the exposure apparatus can include an exposure processing ability, i.e., the throughput.  
         [0003]     As a scheme that greatly improves the throughput, a scheme is available which simultaneously performs an alignment process (a measurement process for alignment) and an exposure process (a process of forming a latent pattern on a substrate while positioning the substrate on the basis of information obtained by the alignment process). According to this scheme, two stages are provided. The alignment process is performed for a substrate on the stage in an alignment process area, and the exposure process is performed for a substrate on the stage in an exposure process area. When the simultaneous processes are ended, the stage which holds the aligned substrate is moved from the alignment process area into the exposure process area, and the stage which holds the exposed substrate is moved from the exposure process area into the alignment process area.  
         [0004]     According to this scheme, the two stages must be swapped between the alignment process area and exposure process area. An exposure apparatus is available which moves two stages on one stage base in order to swap them. If the two stages are arranged on one stage base, when the alignment process and exposure process are to be performed simultaneously, vibration which can be caused by a reaction force generated upon driving one stage adversely affects driving and positioning of the other stage. More specifically, the reaction force which accompanies driving of one stage can decrease the positioning accuracy of the other stage or prolong the settling time during positioning.  
         [0005]     Japanese Patent Laid-Open No. 2001-203140 discloses the following exposure apparatus. Two stage bases are arranged-on a base plate. A stage main body which is movable in X and Y directions is arranged on each stage base. Wafer tables are held by the convey arm mechanisms of convey mechanisms and are swapped between the two stage main bodies. In the exposure apparatus disclosed in this reference, vibration that can be generated by one stage main body is prevented from being transmitted to the other stage main body.  
         [0006]     With the wafer table swapping scheme disclosed in this reference, in addition to wafer or wafer table positioning mechanisms, to swap the two wafer tables, the convey mechanisms that drive the two wafer tables two-dimensionally are indispensable. The convey mechanisms do not share components with the wafer or wafer table positioning mechanisms but are completely independent, making the structure of the exposure apparatus complicated.  
         [0007]     The convey mechanisms for swapping the wafer tables disclosed in Japanese Patent Laid-Open No. 2001-203140 cannot swap the positions of the two convey arm mechanisms that respectively hold the wafer tables. Therefore, while the two convey arm mechanisms respectively hold the wafer tables, the two wafer tables cannot be simultaneously swapped between the two stage main bodies. Accordingly, the convey mechanisms for swapping the wafer tables disclosed in this reference require a long period of time for swapping the wafer tables.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been made in view of the above background, and has as its object to provide a technique that can easily simplify the apparatus structure while enabling positioning of, e.g., two moving elements independently of each other at high speed and high accuracy.  
         [0009]     According to the present invention, there is provided a positioning apparatus comprising first and second bases, and two moving elements which are guided by the first and second bases to move on the first and second bases, wherein a distance is ensured between the first and second bases, and when the two moving elements move between the first and second bases, both of a guide surface of the first base and a guide surface of the second bases are used.  
         [0010]     According to a preferred embodiment of the present invention, preferably, the apparatus further comprises a base driving mechanism which changes the distance between the first and second bases, wherein the base driving mechanism ensures a predetermined distance between the first and second bases when one of the two moving elements moves on the first base and the other one of the two moving elements moves on the second base, and moves the first and second bases close to each other, when the two moving elements move between the first and second bases, such that the distance between the first and second bases is smaller than the predetermined distance.  
         [0011]     According to a preferred embodiment of the present invention, preferably, when the one moving element moves from the first base onto the second base, the other moving element moves from the second base onto the first base simultaneously.  
         [0012]     According to another preferred embodiment of the present invention, the moving elements are moved by, e.g., an electromagnetic force that acts between the bases and moving elements. Furthermore, the moving elements can be moved between the first and second bases by an electromagnetic force that acts between the first and second bases and the moving elements.  
         [0013]     According to still another preferred embodiment of the present invention, the positioning apparatus can further comprise a first driving mechanism which is connected to one of the two moving elements on the first base to move the one moving element, and a second driving mechanism which is connected to the other moving element on the second base to move the remaining moving element, and the two moving elements are driven by the first and second driving mechanisms to move on and between the first and second bases.  
         [0014]     According to still another preferred embodiment of the present invention, the moving elements can be supported on the first and second bases by an air bearing. When the moving elements move between the first and second bases, preferably, a pneumatic pressure of the air bearing is increased to be higher than in a case wherein the moving elements move on the first and second bases.  
         [0015]     According to still another preferred embodiment of the present invention, the positioning apparatus can comprise a sensor which detects a relative positional relationship between the first and second bases, and the base driving mechanism can be driven on the basis of an output from the sensor.  
         [0016]     According to still another preferred embodiment of the present invention, preferably, end portions of the guide surfaces of the first and second bases which oppose each other are chamfered.  
         [0017]     According to still another preferred embodiment of the present invention, the first and second bases can respectively have engaging portions, and when the first and second bases are driven by the base driving mechanism to become close to each other, the engaging portion of the first base engages with the engaging portion of the second base to position the first and second bases with respect to each other.  
         [0018]     An exposure apparatus according to the present invention is directed to an exposure apparatus which exposes a substrate coated with a photosensitive agent. The exposure apparatus comprises a positioning apparatus which has first and second stages and holds and positions substrates on the first and second stages, and a pattern forming portion which exposes the photosensitive agent on the substrate held on, of the first and second stages, a stage which is located in an exposure area, to form a latent pattern, wherein the positioning apparatus comprises a positioning apparatus according to the present invention, and the first and second moving elements respectively include the first and second stages.  
         [0019]     A device manufacturing method according to the present invention comprises a step of forming a latent pattern on a photosensitive agent applied to a substrate by using an exposure apparatus according to the present invention, and a step of developing the latent pattern.  
         [0020]     According to the present invention, a technique can be provided which facilitates simplification of the apparatus structure while enabling positioning of, e.g., two moving elements independently of each other at high speed and high accuracy.  
         [0021]     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0023]      FIG. 1  is a side view showing the schematic structure of an exposure apparatus according to a preferred embodiment of the present invention;  
         [0024]      FIG. 2  is a perspective view showing the schematic structure of a positioning apparatus according to the preferred embodiment of the present invention which is to be built into the exposure apparatus shown in  FIG. 1 ;  
         [0025]      FIG. 3  is a sectional view schematically showing the structure of a planar motor;  
         [0026]      FIG. 4  is an enlarged view of a portion A of  FIG. 3 ;  
         [0027]      FIG. 5  is a view showing the layout of planar motor coils;  
         [0028]      FIG. 6  is a view showing the structure of a planar motor coil;  
         [0029]      FIG. 7  is a view showing the structure of the planar motor coil;  
         [0030]      FIG. 8  is a view for explaining stage swapping operation;  
         [0031]      FIG. 9  is a block diagram showing an example of the structure of a control system for the positioning apparatus;  
         [0032]      FIG. 10  is a flowchart for explaining the stage swapping operation of the exposure apparatus;  
         [0033]      FIGS. 11A  to  11 F are views showing a stage swapping procedure;  
         [0034]      FIGS. 12A and 12B  are enlarged views of a portion C of  FIG. 3 ;  
         [0035]      FIGS. 13A and 13B  are enlarged views of the portion C of  FIG. 3  in the second embodiment;  
         [0036]      FIG. 14  is an enlarged view of the portion C of  FIG. 3  in the third embodiment;  
         [0037]      FIG. 15  is a view schematically showing the structure of a positioning apparatus according to the fourth embodiment;  
         [0038]      FIG. 16  is an enlarged view of a portion D of  FIG. 15 ;  
         [0039]      FIGS. 17A  to  17 D are views showing stage swapping operation in the fifth embodiment;  
         [0040]      FIG. 18  is a flowchart showing the flow of an entire semiconductor device manufacturing process; and  
         [0041]      FIG. 19  is a flowchart showing the flow of a wafer process in detail. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]     The preferred embodiments of the present invention will be described with reference to the accompanying drawings.  
       First Embodiment  
       [0043]      FIG. 1  is a side view showing the schematic structure of an exposure apparatus according to a preferred embodiment of the present invention, and  FIG. 2  is a perspective view showing the schematic structure of a positioning apparatus according to the preferred embodiment of the present invention which is to be built into the exposure apparatus shown in  FIG. 1 . A positioning apparatus  200  has first and second stages  12  and  13  which respectively hold and move wafers (substrates). An exposure apparatus  100  into which the positioning apparatus  200  is built has an exposure process area  96  (see  FIG. 5 ) where an exposure process (a process of forming a latent pattern on a photosensitive agent coated on a wafer) is performed, an alignment process area  95  (see  FIG. 5 ) where an alignment process (a process of detecting a mark position or the like on the wafer for alignment) is performed, and a swap area  16  (see  FIG. 5 ) where a stage present in the exposure process area and a stage present in the alignment process area are swapped. Part of the swap area can typically overlap part of the exposure process area and part of the alignment process area.  
         [0044]     In the exposure apparatus  100 , while an exposure process takes place in the exposure process area, an alignment process for a wafer which is to be exposed next takes place in the alignment process area. When the exposure process and exposure process are ended, the stage present in the exposure process area and the stage present in the alignment process area are swapped through the swap area. An aligned wafer is thus placed in the exposure process area and positioned on the basis of information (information for aligning a pattern with each shot area of the wafer) obtained by the alignment process, and a latent pattern is formed on each shot area. An exposed wafer is recovered by a convey mechanism such as a robot hand in the exposure process area, alignment process area, swap area, or another area.  
         [0045]     A reticle (original) is held by a reticle stage (original stage)  2  and illuminated by an illumination unit  1 . The pattern of the reticle is projected onto a wafer (substrate)  4 A on the stage  12  or  13  (the stage  12  in the case of  FIG. 1 ) in the exposure process area through a reduction projection lens  3  to form a latent pattern on the photosensitive agent on the wafer  4 A. The exposure apparatus  100  can employ the step &amp; repeat scheme, step &amp; scan scheme, or another scheme. When the exposure apparatus  100  employs the step &amp; scan scheme, while scanning the reticle by the reticle stage  2  and the stage that holds the wafer, the reticle pattern is transferred onto the wafer with a slit beam. The reticle and wafer are scanned with a speed ratio that matches the reduction ratio of the reduction projection lens  3 .  
         [0046]     The positioning apparatus  200  includes first and second separate stage bases (first and second bases)  4 B and  4 C as stage bases that support the first and second stages (first and second moving elements)  12  and  13 . When driving the first and second stages  12  and  13  independently of each other (that is, when performing an exposure process and alignment process simultaneously), the first and second stage bases  4 B and  4 C are arranged to be separate from each other by a predetermined distance. When swapping the positions of the first and second stages  12  and  13 , the first and second stage bases  4 B and  4 C are moved to become close to each other such that a distance between them is smaller than the predetermined distance, and typically brought into contact with each other. In performing the exposure process and alignment process simultaneously, if the first and second stage bases  4 B and  4 C are arranged to be separate from each other by the predetermined distance, when the first and second stages  12  and  13  are to be driven independently of each other, a reaction force generated by driving one stage can be prevented from adversely affecting (causing vibration, positioning error, or the like) the other stage.  
         [0047]     Each of the first and second stage bases  4 B and  4 C is supported by mounts  4 D. The mounts  4 D are typically include active mounts. The active mounts include stage base driving mechanisms which drive the stage bases. Each stage base driving mechanism is controlled to decrease the vibration on the basis of an output from a sensor, e.g., a vibration sensor, provided to the stage base or the like. The stage base driving mechanism can also be used to change the distance between the first and second stage bases  4 B and  4 C, as will be described later.  
         [0048]     The reticle stage  2 , the reduction projection lens  3 , an alignment scope  6 , interferometers  7  to  11 , and the like can be supported by an intermediate base  5 .  
         [0049]     The alignment scope  6  includes a microscope which measures the position of an alignment mark formed on the wafer in the alignment process area and the position of a reference mark  14  provided to the stage (the stage  13  in the case of  FIG. 1 ) that holds the wafer to obtain alignment information for positioning the wafer and aligning the wafer and reticle.  
         [0050]     The X interferometers  7  ( 7 A to  7 C) measure the X-direction position of the stage (the stage  12  in the case of  FIG. 1 ) in the exposure process area. The Y interferometers  8  ( 8 A to  8 D) measure the Y-direction position of the stage (the stage  12  in the case of  FIG. 1 ) in the exposure process area.  
         [0051]     The X interferometers  9  ( 9 A to  9 C) measure the X-direction position of the stage (the stage  13  in the case of  FIG. 1 ) in the alignment process area. The Y interferometers  10  ( 10  to  10 D) measure the Y-direction position of the stage (the stage  13  in the case of  FIG. 1 ) in the alignment process area.  
         [0052]     The Y interferometers  11  ( 11 A and  11 B) measure the Y-direction positions of the stages  12  and  13  in the swap area.  
         [0053]     An illuminance sensor  15  is arranged on the upper surface of each of the first and second stages  12  and  13  and can be used to measure the illuminance of the exposure light before exposure for the purpose of exposure amount correction (calibration).  
         [0054]     An example of the structure of the positioning apparatus  200  will be described with reference to FIGS.  3  to  7 . As shown in  FIG. 3 , the first stage  12  is mounted on a first slider  12 B, and the second stage  13  is mounted on a second slider  13 B. In this embodiment, the first stage  12  and slider  12 B form a first moving element, and the second stage  13  and slider  13 B form a second moving element.  
         [0055]      FIG. 4  is an enlarged view of a portion A of  FIG. 3 . The first stage base  4 B has a coil (planar motor coil)  12 A which forms a planar motor. The planar motor coil  12 A is arranged to cover the moving range of the first slider  12 B within the exposure process area. The first slider  12 B has a magnet (planar motor magnet)  12 C which forms a planar motor. When a driving current is applied to the planar motor coil  12 A, the Lorentz force (electromagnetic force) is exerted on the planar motor magnet  12 C to move the first slider  12 B in an X-Y plane.  
         [0056]     Similarly, the second stage  13  has a planar motor coil  13 A, and the second slider  13 B has a planar motor magnet. When a driving current is applied to the planar motor coil  13 A of the second stage  13 , the Lorentz force (electromagnetic force) is exerted on the planar motor magnet of the second slider  13 B to move the second slider  13 B in the X-Y plane.  
         [0057]     An air bearing (not shown) is arranged between the first and second sliders  12 B and  13 B and the first and second-stage bases  4 B and  4 C. The first and second sliders  12 B and  13 B are levitated with respect to the guide surfaces of the first and second stage bases  4 B and  4 C and move in noncontact with them.  
         [0058]     As shown in  FIGS. 6 and 7 , the planar motor coil  12 A includes first and second single-wire coils perpendicular to each other. Each single-wire coil is turned back at the peripheral portion of the area where it is arranged and runs parallel to its pre-turn portion. The first coil has coil terminals  12 D and  12 E, and the second coil has coil terminals  12 F and  12 G. The planar motor coil  13 A also has the same structure as that of the planar motor coil  12 A.  
         [0059]     The principle of the planar motor will be described. As shown in  FIG. 7 , when driving currents  12 H and  12 I are applied to the planar motor coil  12 A in directions indicated by arrows, the Lorentz forces (electromagnetic forces) act in two directions on the planar coil magnet of the first slider  12 B (or second slider  13 B) due to the magnetic fields generated by the two perpendicular coils, and the resultant force drives the first slider  12 B (or second slider  13 B) in a −X direction. Based on this principle, when the directions of the driving currents to be applied to the two coils that form the planar motor coil are changed, the slider can be driven in the X and Y directions.  
         [0060]     As shown in  FIG. 5 , the first stage base  4 B has, in addition to the simultaneous processing (or independent driving) planar motor coils which drive the stage (the stage  12  in the case of  FIG. 5 ) in the exposure process and alignment process, swapping planar motor coils  16 A 1  and  16 B 1  which drive the stages during swapping. Similarly, the first stage base  4 B has, in addition to the simultaneous processing (or independent driving) planar motor coils which drive the stage (the stage  13  in the case of  FIG. 5 ) in the exposure process and alignment process, swapping planar motor coils  16 A 2  and  16 B 2  which drive the stages during swapping.  
         [0061]     The swapping planar motor coils  16 A 1  and  16 B 1  overlap the area where the simultaneous processing planar motor coil  12 A is arranged, so that the area where the stage can be driven by the simultaneous processing planar motor coil  12 A overlaps the area where the stage can be driven by the swapping planar motors coil  16 A 1  and  16 B 1 . Similarly, the swapping planar motor coils  16 A 2  and  16 B 2  overlap the area where the simultaneous processing planar motor coil  13 A is arranged, so that the area where the stage can be driven by the simultaneous processing planar motor coil  13 A overlaps the area where the stage can be driven by the swapping planar motor coils  16 A 2  and  16 B 2 . With this structure, the stages  12  and  13 , which are driven by the simultaneous processing planar motor coils  12 A and  13 B in the exposure process and alignment process which are to be performed simultaneously, can be swapped by the swapping planar motor coils  16 A 1 ,  16 A 2 ,  16 B 1 , and  16 B 2 .  
         [0062]     As shown in  FIG. 8 , in the swap area  16 , in order to swap the position of the first slider  12 B on which the first stage  12  is mounted and the position of the second slider  13 B on which the second stage  13  is mounted, the first and second sliders  12 B and  13 B are temporarily positioned in the swap area  16 , as indicated by arrows. After that, the swapping planar motor coils  16 A 1 ,  16 A 2 ,  16 B 1 , and  16 B 2  are driven to swap the positions of the first and second sliders  12 B and  13 B.  
         [0063]      FIG. 9  is a view showing an example of the structure of a control system for the positioning apparatus  200 . An exposure stage X-Y interferometer system  17  measures the position in the X-Y plane of the stage (the stage  12  in the case of  FIG. 9 ) located in the exposure process area  96  by using the X and Y interferometers  7  and  8  described above. The measurement result is provided to a stage control system  19 .  
         [0064]     An alignment stage X-Y interferometer system  18  measures the position in the X-Y plane of the stage (the stage  13  in the case of  FIG. 9 ) located in the alignment process area  95  by using the X interferometers  9  and Y interferometers  10  described above, and provides the measurement result to the stage control system  19 .  
         [0065]     The stage control system  19  controls positioning of the stages  12  and  13  on the basis of the position information on the stages  12  and  13  provided from the interferometer systems  17  and  18 , and alignment between the stage and the reticle stage  2  in the exposure process area  96 .  
         [0066]     An exposure stage driver  20  determines the driving current and the target position of the stage in the exposure process area  96  in response to an instruction provided from the stage control system  19 , and applies the driving current to the planar motor coil  12 A. An alignment stage driver  21  determines the driving current and the target position of the stage in the alignment process area  95  in response to an instruction provided from the stage control system  19 , and applies the driving current to the planar motor coil  13 A.  
         [0067]     The stage swapping operation of the exposure apparatus  100  will be described with reference to  FIG. 10  and  FIGS. 11A  to  11 F.  
         [0068]     In step  101 , an alignment process for the wafer in the alignment process area is ended. In step  102 , an exposure process for the wafer in the exposure process area is ended.  
         [0069]     In step  103 , the slider  13 B, on which the stage  13  is mounted, in the alignment process area is moved from the position (the position in the alignment process area) shown in the  FIG. 11A  to the position (the position in the swap area) shown in  FIG. 13C  via the position shown in  FIG. 11B  by applying the driving current to the planar motor coil  13 A. Simultaneously with step  103 , in step  104 , the slider  12 B, on which the stage  12  is mounted, in the exposure process area is moved from the position (the position in the exposure process area) shown in  FIG. 11A  to the position (the position in the swap area) shown in  FIG. 11C  via the position shown in  FIG. 11B  by applying the driving current to the planar motor coil  12 A.  
         [0070]     In step  105 , the sliders  12 B and  13 B in the swap area  16  are moved from the positions (the positions in the swap area) shown in  FIG. 11C  to the positions (the positions in the swap area) shown in  FIG. 11D  by applying the driving currents to the swapping planar motor coils  16 A 1 ,  16 A 2 ,  16 B 1 , and  16 B 2 .  
         [0071]     In step  106 , the sliders  13 B and  12 B are driven from the positions shown in  FIG. 1I D to the positions shown in  FIG. 11F  via the positions shown in  FIG. 11E  by the simultaneous processing planar motor coils  12 A and  13 A. With the above operation, the positions of the sliders  12 B and  13 B are swapped.  
         [0072]     In step  107 , in the alignment process area, the wafer (exposed wafer) on the stage  12  mounted on the slider  12 B and a new wafer are swapped by convey mechanisms (not shown), and an alignment process for the new wafer is started. Simultaneously with step  107 , in step  108 , in the exposure process area, an exposure process (transfer of the reticle pattern) is started for the wafer (the wafer for which the alignment process (measurement for alignment) has been completed) on the stage  13  mounted on the slider  13 B.  
         [0073]     When the above operation is repeated, a plurality of wafers are continuously processed while the alignment process and exposure process are performed simultaneously in each cycle.  
         [0074]     In the series of operation described above, the interferometers for position measurement in the X-Y direction of the slider (stage) are switched in the following manner. In the layout shown in  FIG. 11A , the X-direction position of the slider  12 B is measured by the X interferometer  7 B, and its Y-direction position and rotation angle about a Z-axis are measured by the Y interferometers  8 A and  8 B. The X-direction position of the slider  13 B is measured by the X interferometer  9 B, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 C and  10 D.  
         [0075]     In the layout shown in  FIG. 11B , the X-direction position of the slider  12 B is measured by the X interferometers  7 A and  7 B, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  8 A and  8 B. The X-direction position of the slider  13 B is measured by the X interferometers  9 B and  9 C, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 C and  10 D.  
         [0076]     In the layout shown in  FIG. 11C , the X-direction position of the slider  12 B is measured by the X interferometer  7 A, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  8 B and  11 A. The X-direction position of the slider  13 B is measured by the X interferometer  9 C, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 C and  11 B.  
         [0077]     In the layout shown in  FIG. 11D , the X-direction position of the slider  12 B is measured by the X interferometer  7 A, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 A and  11 A. The X-direction position of the slider  13 B is measured by the X interferometer  9 C, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  8 D and  11 B.  
         [0078]     In the layout shown in  FIG. 11E , the X-direction position of the slider  12 B is measured by the X interferometers  9 A and  9 B, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 A and  10 B. The X-direction position of the slider  13 B is measured by the X interferometers  7 B and  7 C, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  8 C and  8 D.  
         [0079]     In the layout shown in  FIG. 11F , the X-direction position of the slider  12 B is measured by the X interferometer  9 B, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  10 A and  10 B. The X-direction position of the slider  13 B is measured by the X interferometer  7 B, and its Y-direction position and rotation angle about the Z-axis are measured by the Y interferometers  8 C and  8 D.  
         [0080]     When the measuring interferometers are switched in the above manner such that the measurement results for the respective axes are not intermittent, the two stages can be swapped by the planar motors between the exposure process area and alignment process area.  
         [0081]     As described above, the stage base which supports the first and second stages  12  and  13  is separated into the first and second stage bases  4 B and  4 C.  FIGS. 12A and 12B  are enlarged views of a portion C of  FIG. 3 . As shown in  FIG. 12A , when the first and second stages  12  and  13  are to be driven independently of each other (that is, when an exposure process and alignment process are to be performed simultaneously), the first and second stage bases  4 B and  4 C are arranged sufficiently separate from each other so they are not brought into contact with each other by reaction forces which are generated when the sliders on which the stages are mounted are driven. When the positions of the first and second stages  12  and  13  are to be swapped, the first and second stage bases  4 B and  4 C are moved close to each other typically into contact with each other. In performing the exposure process and alignment process simultaneously, if the first and second stage bases  4 B and  4 C are arranged to be separate from each other by the predetermined distance, when the first and second stages  12  and  13  are driven independently of each other, a reaction force which is generated by driving one stage can be prevented from adversely affecting (transmission of vibration, increase in positioning error, increase in settling time, and the like) the other stage. The mutual positional relationship between the first and second stage bases  4 B and  4 C can be realized by driving the first stage base  4 B and/or second stage base  4 C by the mounts  4 D including the stage base driving mechanisms.  
         [0082]     In the structure examples shown in  FIGS. 12A and 12B , relative position sensors  22 A and  22 B which detect the positions (e.g., in an X, Y, and Z directions) of the stage bases  4 B and  4 C relative to each other are provided. In the stage control system  19  shown in  FIG. 9 , when the positions of the stages  12  and  13  are to be swapped, or when swapping is ended and an alignment process and exposure process are to be started, the driving mechanisms provided to the mounts  4 D are controlled on the basis of outputs from the relative position sensors  22 A and  22 B to adjust the distance between the stage bases  4 B and  4 C.  
         [0083]     According to this embodiment, the first and second stage bases  4 B and  4 C are positioned relative to each other by the mounts  4 D on the basis of the measurement results of the relative position sensors  22 A and  22 B. Thus, when the stages  12  and  13  are to be swapped between the first and second stage bases  4 B and  4 C, they can be smoothly moved between the first and second stage bases  4 B and  4 C while the first and second sliders  12 B and  13 B, on which the stages  12  and  13  are respectively mounted, are supported by the air bearing.  
         [0084]     When the stages  12  and  13  are to be swapped, the pneumatic pressure of the air bearing between the first and second sliders  12 B and  13 B and the first and second stage bases  4 B and  4 C is preferably increased to be higher than in a case wherein the alignment process and exposure process are performed simultaneously (when swapping is not to be performed). Then, the levitating amount (the gap between the stage bases and sliders) of the sliders levitated by the air bearing can be increased. Even when the first or second stage base  4 B or  4 C is vibrated by a disturbance or the like, the collision of the slider against the corner of the stage base can be prevented.  
       Second Embodiment  
       [0085]     The second embodiment provides a modification of the first embodiment. Matters that are not particularly referred to herein can follow the first embodiment.  FIGS. 13A and 13B  are enlarged views of the portion C of  FIG. 3 .  
         [0086]     A stage base which supports first and second stages  12  and  13  is separated into first and second stage bases  4 B and  4 C, in the same manner as in the first embodiment. When the first and second stages  12  and  13  are to be driven independently of each other (that is, when an exposure process and alignment process are to be performed simultaneously), as shown in  FIG. 13A , the first and second stage bases  4 B and  4 C are arranged sufficiently separate from each other so they are not brought into contact with each other by reaction forces which are generated when the sliders on which the stages are mounted are driven. When the positions of the first and second stages  12  and  13  are to be swapped, the first and second stage bases  4 B and  4 C are moved close to each other. In performing the exposure process and alignment process simultaneously, if the first and second stage bases  4 B and  4 C are arranged to be separate from each other, when the first and second stages  12  and  13  are driven independently of each other, a reaction force which is generated by driving one stage can be prevented from adversely affecting the other stage. The mutual positional relationship between the first and second stage bases  4 B and  4 C can be realized by driving the first stage base  4 B and/or second stage base  4 C by the mounts  4 D including the stage base driving mechanisms.  
         [0087]     According to this embodiment, the first and second stage bases  4 B and  4 C are respectively provided with engaging portions which serve as mechanisms to position the first and second stage bases  4 B and  4 C with respect to each other. In the example shown in  FIGS. 13A and 13B , the first stage base  4 B has a positioning pin  23 A as the engaging portion, and the second stage base  4 C has a recess  23 B as the engaging portion. When swapping the positions of the first and second stages  12  and  13 , a stage control system  19  controls the driving mechanisms provided to mounts  4 D to move the first and second stage bases  4 B and  4 C close to each other. Thus, the positioning pin  23 A engages with the recess  23 B, and the first and second stage bases  4 B and  4 C are positioned with respect to each other such that they establish a predetermined positional relationship in the X, Y, and Z directions. The predetermined positional relationship means, regarding the Z direction, that the guide surface (the surface which guides the slider) of the first stage base  4 B and the guide surface of the second stage base  4 C are leveled with each other, and regarding the X and Y directions, a positional relationship that allows the stages  12  and  13  to be swapped between the first and second stage bases  4 B and  4 C.  
         [0088]     According to this embodiment, the first and second stage bases  4 B and  4 C are positioned with respect to each other by the engaging portions such as the positioning pin  23 A and recess  23 B. When the stages  12  and  13  are to be swapped between the first and second stage bases  4 B and  4 C, they can be smoothly moved between the first and second stage bases  4 B and  4 C while the first and second sliders  12 B and  13 B, on which the stages  12  and  13  are respectively mounted, are supported by the air bearing.  
       Third Embodiment  
       [0089]     The third embodiment provides a modification of the first or second embodiment. Matters that are not particularly referred to herein can follow the first or second embodiment.  FIG. 14  is an enlarged view of the portion C of  FIG. 3 .  
         [0090]     According to this embodiment, chamfered portions  4 E are formed on those ends of the guide surfaces of first and second stage bases  4 B and  4 C which correspond to the opposing portions of the first and second stage bases  4 B and  4 C. The chamfered portions  4 E may be flat surfaces as shown in  FIG. 14 , or may be smooth surfaces such as curved structures. When the chamfered portions  4 E are respectively formed on the first and second stage bases  4 B and  4 C, even if a positioning error exists between the first and second stage bases  4 B and  4 C, or the height difference between the first and second stage bases  4 B and  4 C exceeds the levitating amount (the gap between the stage bases and sliders) of the sliders produced by the air bearing, as in a case wherein the first and second stage bases  4 B and  4 C are vibrated by a disturbance or the like, the sliders can be prevented from strongly colliding against the corners of the stage bases to damage the sliders and stage bases.  
       Fourth Embodiment  
       [0091]     The fourth embodiment provides another driving scheme for the planar motors in the first to third embodiments. Matters that are not particularly referred to herein can follow the first to third embodiments.  
         [0092]     This embodiment provides an application to a Sawyer scheme planar pulse motor which is also useful just like the Lorentz driving scheme in the first to third embodiments. As shown in  FIG. 15 , the first and second sliders  12 B and  13 B of the first to third embodiments are replaced by first and second planar pulse motor sliders  32 B and  33 B, and the first and second stage bases  4 B and  4 C of the first to third embodiments are replaced by first and second stage bases  34 B and  34 C respectively having first and second planar pulse motor platens  32 A and  33 A.  
         [0093]      FIG. 16  is an enlarged view of a portion D of  FIG. 15 . A yoke  32 D is excited by a driving coil  32 C of the planar pulse motor slider  32 B. The finger-like yoke of the yoke  32 D is subjected to three-phase attracting force control (not shown) with respect to the finger-like pure-iron base of the planar pulse motor platen  32 A arranged on the upper surface of the stage base  34 B to generate an attracting force continuously. Then, the planar pulse motor slider  32 B moves with respect to the planar pulse motor platen  32 A.  
         [0094]     In this planar pulse motor scheme as well, when first and second stages  12  and  13  are to be driven independently of each other (that is, when an exposure process and alignment process are to be performed simultaneously), the first and second separate stage bases  34 B and  34 C are moved apart. When the positions of the first and second stages  12  and  13  are to be swapped, the first and second stage bases  34 B and  34 C are moved close to each other or brought into tight contact with each other, so that the first and second stages  12  and  13  are moved smoothly between the first and second stage bases  34 B and  34 C.  
       Fifth Embodiment  
       [0095]     In the first to fourth embodiments, two stages are driven by planar pulse motors. In the fifth embodiment, two stages are driven by linear driving mechanisms. The fifth embodiment also includes two stage bases and stage base driving mechanisms (e.g., mounts equivalent to those described above) which drive the stage bases. When the two stages are to be driven independently of each other (that is, when an exposure process and alignment process are to be performed simultaneously), the two stage bases are moved apart. When the positions of the two stages are to be swapped, the two stage bases are moved close to each other or brought into tight contact with each other, so that the two stages are moved smoothly between the two stage bases.  
         [0096]     Matters that are not particularly referred to herein can follow the first to fourth embodiments.  
         [0097]     A first slider  43 A on which a stage for holding a wafer is mounted, a Y driving mechanism  43 B which drives the first slider  43 A in a Y direction, an X driving mechanism  43 C which drives the Y driving mechanism  43 B in the X direction to drive the first slider  43 A in the X direction, and a first stage base  43 D which supports the first slider  43 A to be movable in an X-Y plane are arranged in an exposure process area.  
         [0098]     A second slider  42 A on which a stage for holding a wafer is mounted, a Y driving mechanism  42 B which drives the second slider  42 A in the Y direction, an X driving mechanism  42 C which drives the Y driving mechanism  42 B in the X direction to drive the second slider  42 A in the X direction, and a second stage base  42 D which supports the second slider  42 A to be movable in the X-Y plane are arranged in an alignment process area.  
         [0099]     In the above structure, while an exposure process takes place in the exposure process area and an alignment process takes place in the alignment process area, the first and second stage bases  43 D and  42 D are supported by mounts (corresponding to the mounts  4 D described above) while they are spaced apart from each other, as shown in  FIG. 17A . A reaction force and vibration which are generated when the two stages accelerate or decelerate are not transmitted between the two stages, and the two stages can be operated in atmospheres completely independent of each other.  
         [0100]     When a wafer for which an alignment process (a process of detecting a mark position on the wafer for the purpose of alignment) has been ended in the alignment process area is to be moved to the exposure process area and when the wafer for which the exposure process has been ended in the exposure process area is to be recovered (assume that the wafer is recovered in the alignment process area), the positions of the two stages (sliders) must be swapped.  
         [0101]      FIGS. 17B  to  17 D exemplify the swapping sequence of the two stages. First, as shown in  FIG. 17B , the sliders  43 A and  42 A are moved to swap preparation positions, and the stage bases  43 D and  42 D are moved close to each other or brought into tight contact with each other by the mounts including the stage base driving mechanisms. In this case, position control and positioning of the stage bases  43 D and  42 D can follow the first to fourth embodiments.  
         [0102]     Subsequently, as shown in  FIG. 17C , while the stage bases  43 D and  42 D are close to each other or in tight contact with each other, the slider  42 A is disconnected from the Y driving mechanism  42 B, and the slider  43 A is disconnected from the Y driving mechanism  43 B. The slider  43 A is connected to the Y driving mechanism  43 B, and the slider  43 A is connected to the Y driving mechanism  42 B. Thus, the sliders are swapped between the Y driving mechanisms  42 B and  43 B.  
         [0103]     As shown in  FIG. 17D , the slider  42 A is positioned in the exposure process area by the Y driving mechanism  43 B and X driving mechanism  43 C, and the slider  43 A is positioned in the alignment process area by the Y driving mechanism  42 B and X driving mechanism  42 C. After that, an alignment process and exposure process are performed simultaneously.  
         [0000]     [Device Manufacturing Method] 
         [0104]     A semiconductor device manufacturing process which uses the above exposure apparatus will be described hereinafter.  FIG. 18  is a flowchart showing the flow of the entire semiconductor device manufacturing process. In step  1  (circuit design), the circuit of a semiconductor device is designed. In step  2  (mask fabrication), a mask is fabricated on the basis of the designed circuit pattern. In step  3  (wafer manufacture), a wafer is manufactured using a material such as silicon. In step  4  (wafer process) called a preprocess, an actual circuit is formed on the wafer in accordance with lithography using the mask and wafer described above. In step  5  (assembly) called a post-process, a semiconductor chip is formed from the wafer fabricated in step  4 . This step includes processes such as assembly (dicing and bonding) and packaging (chip encapsulation). In step  6  (inspection), inspections such as operation check test and durability test of the semiconductor device fabricated in step  5  are performed. A semiconductor device is finished with these steps and shipped (step  7 ).  
         [0105]      FIG. 19  is a flowchart showing the flow of the above wafer process in detail. In step  11  (oxidation), the surface of the wafer is oxidized. In step  12  (CVD), an insulating film is formed on the wafer surface. In step  13  (electrode formation), an electrode is formed on the wafer by deposition. In step  14  (ion implantation), ions are implanted in the wafer. In step  15  (resist process), a photosensitive agent is applied to the wafer. In step  16  (exposure), a latent image of the circuit pattern is formed on the photosensitive agent on the wafer by the exposure apparatus described above. In step  17  (development), the exposed wafer is developed. In step  18  (etching), portions other than the developed resist image are removed. In step  19  (resist removal), any unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer.  
         [0106]     As many apparent widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.  
       CLAIM OF PRIORITY  
       [0107]     This application claims priority from Japanese Patent Application No. 2004-146639 filed on May 17, 2004, the entire contents of which are hereby incorporated by reference herein.