CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a U.S. continuation application which is filed under 35 USC 111(a) and claims the benefit under 35 USC 120 and 365(c) of International Application No. PCT/JP2005/004757, filed on Mar. 17, 2005, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to a stage device, and more particularly to a stage device which is moved with high accuracy in a X-Y direction and a rotating direction by using a planar motor.  
         [0004]     2. Description of the Related Art  
         [0005]     Concerning ultra-precision machining devices and semiconductor devices which are the basis of information processing technology, the demand for high-accuracy positioning and high-speed processing of stage devices, used for these devices, is increasing. For example, for the stage device which is a key component of a semiconductor exposure device, the positioning accuracy on the order of 10 nm and the movement range of several hundreds of millimeter are needed. And, in order to aim at improvement in the productivity of semiconductor devices, it is necessary to move the stage on which a work piece is mounted to the processing position at a high speed. For this reason, it is desirable to implement the stage device which solves all of the above-mentioned problems.  
         [0006]     For example, in various semiconductor manufacturing devices used in semiconductor manufacturing processes, the stage device is provided so that the wafer used as a movable body is carried on the stage device and the wafer carried on the stage device is moved therein. The stage device includes a drive unit which drives the movement of the stage on which the wafer is carried to the base, and a position measuring device which measures the position of the stage to the base.  
         [0007]     A stack type stage device is known as a conventional drive unit, in which the stage which is moved in the X direction only and the stage which is moved in the Y direction only are accumulated. Since it is necessary for the stack type stage device to have a high-horizontal rigidity, and there is a problem that the weight of the device itself becomes heavy and a large error of the position in the perpendicular direction may occur due to the influence of the weight.  
         [0008]     A SAWYER motor is known as a drive unit which is devised in order to solve the above problem. The SAWYER motor is one of planar motors, and can move freely the stage in the X-Y direction and in the rotating direction.  
         [0009]     The planar motor in the present specification is meant such that the structural part of the motor is provided in the stage, and, in association with the convex part provided in the base, the planar motor is able to lift the stage over the base and able to move the stage to a desired position directly, without using the X-direction and Y-direction shafts. For example, refer to Japanese Laid-Open Patent Application No. 05-328702.  
         [0010]     Next, the stage device which uses the SAWYER motor will be explained with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  is a schematic diagram of the stage device which uses the SAWYER motor, and  FIG. 2  is a plan view of the structure of the stage device corresponding to the area A indicated in  FIG. 1 .  
         [0011]     The stage device  200  generally includes a base  211 , a pair of X-direction actuators  213 , a pair of Y-direction actuators  214 , a tilt actuator  216 , a movable stage part  217 , a fixed stage part  219 , a chuck  221 , a mirror  222 , and a laser measuring instrument  223 . The planar motor is constituted by the pair of X-direction actuators  213 , and the pair of Y-direction actuators  214 .  
         [0012]     A plurality of convex parts  212  are provided on the top surface of the base  211  at intervals of a predetermined distance. The X-direction actuator  213  is constituted by,a plurality of coil-parts  215  and a plurality of air bearings  224 .  
         [0013]     By applying the current to the coil parts  215 , the driving force is generated to move the movable stage part  217 . The Y-direction actuators  214  are constituted by the plurality of coil parts  215  and the pair of air bearings  224 . By applying the current to the coil parts  215 , the driving force is generated in the X-direction actuator  213  and the Y-direction actuator  214 , and the movable stage part  217  is moved.  
         [0014]     The tilt actuator  216  is provided for adjusting the horizontal attitude of the movable stage part  217 . The fixed stage part  219  is arranged integrally with the movable stage part  217 . On the fixed stage part  219 , the chuck  221  for mounting the work piece (the movable body) is arranged integrally with the fixed stage part  219 .  
         [0015]     The mirror  222  is arranged on the movable stage part  217 . This mirror  222  is provided for reflecting the laser beam which is emitted by the light source. The laser beam is reflected to a laser measuring instrument  223  by the mirror  222 , so that the position of the movable stage part  217  is measured by the laser measuring instrument  223 .  
         [0016]     In this position measuring device that determines the position in the X-Y direction using the laser interference displacement gauge  223 , two displacement gauges are combined with a highly precise straightedge which covers the movement range perpendicular to the displacement measuring direction and has the guaranteed shape accuracy, and thereby performing the position detection.  
         [0017]     Among other conventional position measuring devices, there are known position measuring devices which have the structure in which a given number of measuring devices, such as rotary encoders and linear encoders, are arranged for a given number of degrees of freedom. For example, when performing two-dimensional positioning, one of the position measuring devices having such structure may be configured so that the stage which is moved in the X-direction and the stage which is moved in the Y-direction are accumulated independently of each other. Another of the position measuring device having such structure may be configured so that the peripheral scale and the one-axial stage are combined, and a rotational position and a radial position are measured independently, and positioning is performed.  
         [0018]     Conventionally, when detecting the position equivalent to pitching and yawing angles of a moving body, the autocollimator has been used. This autocollimator is adapted to measure the pitching and yawing angles of the moving body simultaneously with respect to movement in the straight line direction along one axis, but it requires the highly precise straightedge to measure the position of the moving body in the X-Y direction thereof.  
         [0019]     Moreover, the level vial is known as the device which measures the rolling angle of a moving body. However, the level vial has a problem in the response speed and measurement accuracy, and it is unsuitable for a high accuracy measuring device.  
         [0020]     To obviate the problem, the method in which two parallel straightedges are arranged to compute a rolling angle from a difference between the distances to the straightedges has been used. Moreover, the method in which a single straightedge is arranged as a reference mirror surface to detect a rolling angle using an autocollimator has been used. See Japanese Laid-Open Patent Application No. 05-328702.  
         [0021]     However, the following problems arise in the stage device using the above-mentioned conventional position measuring device. That is, the measuring device used in the conventional position measuring device, such as a rotary encoder or a linear encoder, can perform only one-dimensional positioning. In order to perform two-dimensional positioning, it is necessary to combine at least two sets of the above-mentioned measuring devices. And the design of a moving body position measuring device has a considerable constraint in the structure thereof.  
         [0022]     Also in the case in which positioning is performed using the laser measuring instrument  223 , what can be performed is only one-dimensional positioning. In order to perform two-dimensional positioning, it is necessary to use the straightedge which is constructed with high accuracy. Consequently, when the position measuring device of this kind is provided in the stage device, there is a constraint in the structure thereof, and the manufacturing cost becomes high.  
       SUMMARY OF THE INVENTION  
       [0023]     According to one aspect of the invention, there is provided an improved stage device in which the above-mentioned problems are eliminated. According to one aspect of the invention, there is provided a stage device which can attain the miniaturization of the stage device and can perform the measurement of a position of the stage to the base with high accuracy.  
         [0024]     In an embodiment of the invention which solves or reduces one or more of the above-mentioned problems, there is provided a stage device which comprises: a base; a stage carrying a movable body and being moved over the base; a planar motor driving the stage; an air bearing acting to lift the stage over the base; a scale part disposed on the base to include an angle grating which has an angle-related characteristic varied in a two-dimensional direction in accordance with a known function; and at least one two-dimensional angle sensor disposed on the stage so that the at least one two-dimensional angle sensor emits a light beam to the angle grating of the scale part and detects a two-dimensional angle of a light beam reflected from the scale part.  
         [0025]     The present invention can provide a stage device which attains the miniaturization of the stage device and performs measurement of a position of the stage to the base with high accuracy.  
         [0026]     According to the stage device of the present invention, the scale part is provided on the base and the two-dimensional angle sensors are provided on the stage, and it is possible that two or more stages be carried on the base and the two or more stages be individually moved in the condition in which the position detection is possible.  
         [0027]     Since there is no guide structure of the shaft and the planar motor which can control the X-direction movement, the Y-direction movement and the rotational movement around the Z axis is used, it is possible that the weight of the stage device be saved and the manufacturing cost be reduced.  
         [0028]     Since the scale part is formed from the two-dimensional angle grating indicating an angle configuration, it is possible to detect a pitching angle, a rolling angle, a yawing angle, and a two-dimensional position of the stage by using the angle sensors combined with a single scale.  
         [0029]     And, by using the angle grating, the position detection of a two-dimensional coordinate position, which is represented by any of rectangular coordinates, cylindrical coordinates, polar coordinates, and free-form surface coordinates, can be attained.  
         [0030]     Since the two-dimensional angle sensors have a dead pass which is very small when compared with the conventional laser interferometer, they are unlikely to be influenced by the instrumentation error due to thermal expansion, fluctuation of air, etc. Therefore, it is possible to perform high-accuracy position and attitude measurement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a schematic diagram of a stage device which uses a SAYER motor.  
         [0032]      FIG. 2  is a plan view of the structure of the stage device corresponding to the area A indicated in  FIG. 1 .  
         [0033]      FIG. 3  is a cross-sectional diagram of a stage device in a first embodiment of the invention.  
         [0034]      FIG. 4  is a plan view of the structure of the stage device corresponding to the area B indicated in  FIG. 3 .  
         [0035]      FIG. 5A  is a diagram for explaining the relationship between the driving direction of the movable stage and the actuating force of the X-direction and Y-direction actuators.  
         [0036]      FIG. 5B  is a diagram for explaining the relationship between the driving direction of the movable stage and the actuating force of the X-direction and Y-direction actuators.  
         [0037]      FIG. 5C  is a diagram for explaining the relationship between the driving direction of the movable stage and the actuating force of the X-direction and Y-direction actuators.  
         [0038]      FIG. 5D  is a diagram for explaining the relationship between the driving direction of the movable stage and the actuating force of the X-direction and Y-direction actuators.  
         [0039]      FIG. 6  is an enlarged view of the part of the stage device corresponding to the area C indicated in  FIG. 3 .  
         [0040]      FIG. 7  is a perspective view of a scale part and a two-dimensional angle sensor.  
         [0041]      FIG. 8  is a diagram showing the composition of the scale part.  
         [0042]      FIG. 9  is a diagram showing the composition of an optical system of the two-dimensional angle sensor provided in the stage device of the first embodiment.  
         [0043]      FIG. 10  is an exploded perspective view of a stage device in a second embodiment of the invention.  
         [0044]      FIG. 11  is a partially cut-away perspective view of the stage device which is in the assembled condition.  
         [0045]      FIG. 12  is a diagram for explaining the principle of moving the stage.  
         [0046]      FIG. 13  is a diagram showing the composition of the stage device of the present embodiment.  
         [0047]      FIG. 14  is a diagram showing the composition of a modification of the stage device of the present embodiment.  
         [0048]      FIG. 15  is a diagram showing the composition of another modification of the stage device of the present embodiment. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0049]     A description will be given of embodiments of the invention with reference to the accompanying drawings.  
         [0050]     First, with reference to  FIG. 3  and  FIG. 4 , the stage device  230  in the first embodiment of the invention will be explained.  
         [0051]      FIG. 3  is a cross-sectional diagram of the stage device of the first embodiment, and  FIG. 4  is a plan view of the structure of the stage device corresponding to the area B indicated in  FIG. 3 .  
         [0052]     The stage device  230  is a stage device having a SAWYER motor drive part. The stage device  230  comprises a base  231 , a stage  236 , and a surface encoder  249  as shown in  FIG. 3 . A plurality of convex parts  232  are formed on the surface of the base  231  at a predetermined pitch. This predetermined pitch is equivalent to the minimum unit of length by which a movable stage part  237  can be moved. The base  231  is made of a metal, such as iron. The stage  236  comprises a movable stage part  237 , a fixed stage part  239 , a chuck  241 , X-direction actuators  242 A and  242 B, Y-direction actuators  243 A and  243 B, and tilt actuators  245 .  
         [0053]     The movable stage part  237  is a base part which is driven by the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B.  
         [0054]     As shown in  FIG. 4 , under the movable stage,part  237 , the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B are disposed, and a certain space is provided in the center portion.  
         [0055]     Each of the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B comprises two or more coil parts  244  and two or more air bearings  238 , respectively. By supplying the current to the coil part  244 , a magnetic force is generated in the coil part  244 , so that the actuating force is exerted to actuate the movable stage part  237 .  
         [0056]     The air bearings  238  are provided for lifting the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B relative to the base  231  according to the force of air. By providing the air bearings  238 , when the movable stage part  237  is actuated in the direction of X, the direction of Y, or the direction of θ, the movement can be performed freely in any direction.  
         [0057]     The tilt actuator  245  is provided respectively between the movable stage part  237  and each of the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B. These tilt actuators  245  are provided for performing horizontal positioning of the movable stage part  237 .  
         [0058]     The fixed stage part  239  is arranged integrally on the movable stage part  237 . The fixed stage part  239  is moved to a desired position by driving the movable stage part  237  using the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B. On the fixed stage part  239 , the chuck  241  is disposed for mounting a work piece  248  (movable body).  
         [0059]     Next, a description will be given of the method of driving the movable stage part  237  with reference to  FIG. 5A  to  FIG. 5D .  
         [0060]      FIGS. 5A-5D  are diagrams for explaining the relationship between the driving direction of the movable stage and the actuating force of the X-direction and the Y-direction actuators.  
         [0061]     When moving the movable stage part  237  in the X-X direction, as shown in  FIG. 5A , the current is supplied to the coil parts  244  provided in the X-direction actuators  242 A and  242 B, so that the actuating force of the X-direction actuators  242 A and  242 B is generated in the X-X direction in which the movable stage part  237  is moved to a desired position.  
         [0062]     When moving the movable stage part  237  in the Y-direction, as shown in  FIG. 5B , the current is supplied to the coil parts  244  provided in the Y-direction actuators  243 A-and  243 B, so that the actuating force of the Y-direction actuators  243 A and  243 B is generated in the Y-direction in which the movable stage part  237  is moved to a desired position.  
         [0063]     When moving the movable stage part  237  in the direction of θ, as shown in  FIG. 5C  or  FIG. 5D , the current is supplied to the coil parts  244  provided in the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B, so that the actuating force of the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B is generated in the direction indicated by the arrow D or the arrow E.  
         [0064]     And when the fixed stage part  239  is moved to the desired position on the base  231 , the supply of the current to the coil part  244   s  is stopped and the position of the fixed stage part  239  is fixed. As described previously, the pitch of the convex parts  232  provided in the surface of the base  231  is equivalent to the minimum unit of length by which the movable stage  237  can be moved.  
         [0065]     Next, the surface encoder  249  will be explained with reference to  FIG. 3  and  FIG. 4 . The surface encoder  249  is providing for performing position measurement of the movable stage  237 . The surface encoder  249  comprises a scale unit  233  and two-dimensional angle sensors  14 A- 14 C.  
         [0066]     Next, the scale unit  233  will be explained with reference to  FIG. 6 .  FIG. 6  is an enlarged view of the part of the stage device corresponding to the area C indicated in  FIG. 3 . The scale unit  233  is disposed on the convex parts  232  provided in the base  231 . The scale unit  233  comprises a scale part  13 , an upper resin  252 , and a lower resin  253 .  
         [0067]     As shown in  FIG. 7 , the scale part  13  is provided with a number of angle gratings  40  in which the angle-related characteristic changes in the two dimensions in the directions of X and Y in accordance with a known function (which is, in this embodiment, the set of crests and troughs of a sinusoidal wave).  
         [0068]     The upper resin  252  is provided on the top surface of the scale part  13 , and the lower resin  253  is provided on the bottom surface of the scale part  13 . The upper and lower resins  252  and  253  are provided for protecting the scale part  13  from being damaged by an external force. The upper resin  252  is made of a transparent material that has a good transmission coefficient for a light beam to pass through.  
         [0069]     As shown in  FIG. 3  and  FIG. 4 , the two-dimensional angle sensors  14 A- 14 C are disposed on the bottom part of the movable stage part  237  which is surrounded by the X-direction actuators  242 A and  242 B and the Y-direction actuators  243 A and  243 B. In this embodiment, the stage device is provided with the three two-dimensional angle sensors  14 A- 14 C.  
         [0070]     Thus, the two-dimensional angle sensors  14 A- 14 C in this embodiment are provided on the bottom part of the movable stage part  237  which is located adjacent to the scale part  13 , and they are hardly influenced by the effect of disturbance, such as fluctuation of air, as in the conventional laser interferometer. And it is possible for the two-dimensional angle sensors  14 A- 14 C to detect the exact position of the fixed stage  239 .  
         [0071]     The combination of at least three two-dimensional angle sensors  14 A- 14 C and the scale part including the two-dimensional angle gratings  40  allows the detection of the two-dimensional coordinate position, the pitching angle, the rolling angle, and the yawing angle of the moving body by the relative movement between the scale part and the angle sensors. And the distance between the scale part and the angle sensors can also be detected by giving a predetermined angle change to the angle sensors.  
         [0072]     The three two-dimensional angle sensors  14 A- 14 C are provided in this embodiment. However, in order to facilitate the following description, the structure in which only one two-dimensional angle sensor  14  is provided is assumed.  
         [0073]     The height configuration f (x, y) of the angle gratings  40  provided in the scale part  13  is represented by the following formula:
 
 f ( x, y )= Ax ·sin(2 πx/λx )+ Ay ·sin(2 πy/λy )  (1)
 
 In the above formula, Ax and Ay denote the amplitude in the X-direction and the amplitude in the Y-direction, respectively, and λx and λy denote the wavelength in the X-direction and the wavelength in the Y-direction, respectively. 
 
         [0074]     And the X-direction and Y-direction angle configurations θ (x) and ψ (y) of the angle gratings  40  (which are the outputs of the two-dimensional angle sensors  14  when the measurement is performed) are derived from the partial differentials of the configuration of the angle gratings  40 , respectively, and they are represented by the following formulas:
 
θ( x )=δ f/δx =(2 πAx/λx )·cos(2 πx/λx )  (2)
 
ψ( y )=δ f/δy =(2 πAy/λy )·cos(2 πy/λy )  (3)
 
         [0075]      FIG. 7  is a perspective view of the scale part and the two-dimensional angle sensor which are provided in the stage device in the first embodiment of the invention.  
         [0076]     As shown in  FIG. 7  and  FIG. 8 , the scale part  13  is provided on or within the surface of the base  41 . And the scale part  13  comprises the angle gratings  40  in which the angle-related characteristic changes in the two dimensions of the X-direction and the Y-direction in accordance with the known function (which is in this embodiment the set of crests and troughs of a sinusoidal wave).  
         [0077]     As shown in  FIG. 7 , a laser beam reflected from the angle gratings  40  is measured using the two-dimensional angle sensor  14  which is adapted for detecting angle changes in the two directions of X and Y. The angle output in each of the respective directions changes with a change in the position of the sloping face of the crests even if the height from the crests of the angle gratings is the same. Therefore, a two-dimensional coordinate position can be determined based on a change of the angle output.  
         [0078]     Accordingly, the scale part  13  is attached to the base  231  and the two-dimensional angle sensor  14  is attached to the movable stage part  237 , and the two-dimensional coordinates of the movable stage part  237  (or the movable body) can be detected with the relative movement of the scale part and the two-dimensional angle sensor.  
         [0079]     The angle gratings  40  in this embodiment are produced by processing a cylindrical-shape material made of aluminum. The height configuration of the angle gratings  40  can be expressed by the superposition of a sinusoidal wave with the amplitude of 0.3 micrometers and the period of 300 micrometers. The angle amplitude of the angle gratings  40  in this embodiment is ±21.6 minutes.  
         [0080]      FIG. 9  is a diagram showing the composition of the optical system of the two-dimensional angle sensor which is provided in the stage device of the first embodiment.  
         [0081]     The optical system of the two-dimensional angle sensor  14  comprises a light source  50 , reflection prisms  52 ,  53 ,  57 , and  58 , a beam splitter  54 , a ¼ wavelength plate  55 , a collimator lens  56 , and a photodiode  59 . And the laser beam  65  which is emitted by the light source  50  passes through the grid film  51 , and is reflected by the reflection prisms  52  and  53 . The p-polarized light component of the laser beam  65 , the direction of which is changed, passes through the beam splitter  54  and the ¼ wavelength plate  55 , and it is reflected upward by the reflection prism  58  and hits the scale part  13  (the angle gratings  40 ) which is attached to the base  231 .  
         [0082]     The laser beam  65  reflected by the scale part  13  (the angle gratings  40 ) passes through the ¼ wavelength plate  55  again, so that it is converted into an s-polarized light beam. And this light beam is reflected by the beam splitter  54 , so that it passes through the collimator lens  56 . The light beam from the collimator lens  56  is focused-on the photodiode  59  which is located at the focal distance from the collimator lens  56 . The photodiode  59  is divided into four division parts. In this manner, the two-dimensional angle sensor  14  detects a two-dimensional angle change according to the principle of the laser auto-collimation.  
         [0083]     In the surface encoder  249  having the above-mentioned structure, the configuration of the angle gratings  40  serves as the criteria of position detection. And, if an error is contained in the configuration, position detection accuracy will be affected by the error. If the number of the laser beams which are the probes of the two-dimensional angle sensors  14  is one, the output of the laser beam will be greatly affected by a change of the pitch of the lattices of the angle gratings  40  and an error of the configuration of the angle gratings  40 . The influences of such errors can be eliminated by emitting a plurality of laser beams to the equal-phase portions of the angle gratings  40  so that a plurality of crests in the angle gratings  40  can be always observed.  
         [0084]     Therefore, in this embodiment, the three two-dimensional angle sensors  14 A- 14 C are provided on the movable stage part  237 , and this allows a plurality of laser beams to be emitted to the equal-phase portions of the angle gratings  40 . By this composition, the high frequency components of variations in the configuration of the angle gratings  40  (lattice pitch) and the influences of the errors of the configuration of the angle gratings  40  are averaged. Thus, it is possible to attain improvement in measurement accuracy.  
         [0085]     Moreover, in this embodiment, the three two-dimensional angle sensors  14 A- 14 C are combined with the angle gratings  40 , and it is possible to detect a two-dimensional coordinates position, a pitching angle, a rolling angle, and a yawing angle of the moving body with the relative movement between the scale part  13  and the two-dimensional angle sensors  14 A- 14 C. Further, it is possible to detect a distance between the scale part  13  and the two-dimensional angle sensors  14 A- 14 C, by giving a predetermined angle change to the two-dimensional angle sensors  14 A- 14 C.  
         [0086]     Moreover, the two-dimensional angle sensors  14 A- 14 C have a dead pass which is very small when compared with the conventional laser interferometer, and the two-dimensional angle sensors  14 A- 14 C cannot be easily influenced by an instrumentation error due to thermal expansion, fluctuation of air, etc. Thus, it is possible to perform a high-accuracy position and attitude measurement.  
         [0087]     As described previously, in this embodiment, an angle change of the laser beam reflected from the angle gratings  40  is measured using the two-dimensional angle sensors  14 A- 14 C which are adapted for detecting angle changes in the two directions of X and Y. The angle output in each of the respective directions changes with a change in the position of the sloping face of the crests even if the height from the crests of the angle gratings is the same. A two-dimensional coordinate position can be determined based on a change of the angle output.  
         [0088]     Accordingly, the scale part  13  is attached to the base  231  and the two-dimensional angle sensors  14 A- 14 C are attached to the movable stage part  237 , which makes it possible to detect a two-dimensional coordinate position of the movable stage part  237  (or the fixed stage  239 ).  
         [0089]     As described in the foregoing, the surface encoder  249  is provided in the stage device  230  provided with the SAWYER motor drive part, and it is possible to attain the miniaturization of the stage device. With the movable stage part  237  which can be actuated to the base  231  in any of the X direction, the Y direction and the θ direction, the measurement of a position of the fixed stage part  239  (or the movable stage part  237 ) to the base  231  can be performed with high accuracy.  
         [0090]     In the case of the conventional stage device  200 , position detection of the stage is performed with the laser beam from the laser measuring instrument  223 , and if a plurality of stages are provided on the single base  211 , the laser beam may be intercepted by the stages. However, in the case of the stage device  230  of the present embodiment, position detection of the stage  236  can be performed with the stage  236  by itself, and even if a plurality of stages  236  are provided on the single base  231 , position detection of each of the plurality of stages  236  can be performed with sufficient accuracy.  
         [0091]     In the above-mentioned embodiment, the case in which the three two-dimensional angle sensors are provided has been described. However, the composition in which one two-dimensional angle sensor is provided may be used, and the same effectiveness as the above-mentioned embodiment can be acquired.  
         [0092]     Next, a description will be given of the stage device  10  in the second embodiment of the invention with reference to  FIG. 10  and  FIG. 11 .  
         [0093]      FIG. 10  is an exploded perspective view of the stage device  10  in the second embodiment of the invention, and  FIG. 11  is a partially cut-away perspective view of the stage device  10  which is in the assembled condition.  
         [0094]     The stage device  10  is provided for moving the wafer, which is a movable body in the stepper in the semiconductor manufacturing process, to a predetermined position.  
         [0095]     The stage device  10  comprises the base  11 , the stage  12 , the surface encoder  24 , the drive unit, etc. The base  11  serves as the base of the stage device  10 , and the linear motor structure parts  20 A and  25 A, the Z-direction electromagnet  30 , and the two-dimensional angle sensors  14 A- 14 C, etc. which will be described later are disposed on the base  11 .  
         [0096]     In the present embodiment, the case in which the two-dimensional angle sensors  14 A- 14 C used in the first embodiment are used will be explained.  
         [0097]     The wafer  60  and the chuck  61  which are used as a movable body are disposed on the upper part of the stage  12  (refer to  FIG. 13 ). The Z-direction magnet  19  is disposed on the lower part of the stage  12  through the magnets  15  and  16 , the yoke  17 , and the spacer  18 .  
         [0098]     The stage  12  is provided so that the X-direction movement, the Y-direction movement, and the rotational movement around the Z axis of the stage  12  to the base  11  are possible as indicated by the arrows in  FIG. 10 . The surface encoder  24  in this embodiment is essentially the same as that in the first embodiment.  
         [0099]     In the present embodiment, the three two-dimensional angle sensors  14 A- 14 C are provided. However, in order to facilitate understanding of the present invention, in the following, a description will be given of the composition in which only one two-dimensional angle sensor  14  is provided.  
         [0100]     As shown in  FIG. 10 , the scale part  13  in this embodiment is fixed to the mid gear of the back surface (or the surface which confronts the base  11 ) of the stage  12 .  
         [0101]     On the other hand, the two-dimensional angle sensors  14  are in the structure disposed in the base  11 .  
         [0102]     Next, the drive unit will be explained with reference to  FIG. 10  and  FIG. 11 .  
         [0103]     The drive unit has the X-direction movement, the Y-direction movement, and the rotational movement around the Z-axis of the stage  12  to the base  11 .  
         [0104]     The X-direction linear motor structure parts  20 A and  20 B by which this drive unit is disposed on the base  11 , the Y-direction linear motor structure parts  25 A and  25 B, and the Z-direction electromagnet  30 , it is constituted by the X-direction magnet  15  disposed on the stage  12 , the Y-direction magnet  16 , and the Z-direction magnet  19 .  
         [0105]     The X-direction linear motor structure part  20 A is disposed on the base  11 , and it is constituted by the pair of X-direction coils  21 A- 1  and  21 A- 2  (both sides are packed and unacquainted it is called coil  21 A for the directions of X), and core  22 A for the directions of X.  
         [0106]     The pair of the X-direction coils  21 A- 1  and  21 A- 2  are arranged side by side in the X-direction as indicated by the arrow, and it is in the structure which can supply the current independently, respectively.  
         [0107]     The X-direction linear motor structure part  20 B is in the same structure as the X-direction linear motor structure part  20 A, and is constituted by coil  21 B (although a code does not give, constituted by the coil for the directions of X of the pair) for the directions of X, and core  22 B for the directions of X.  
         [0108]     The X-direction linear motor structure part  20 A and the X-direction linear motor structure part  20 B face across the arranging position of the above mentioned two-dimensional angle sensors  14 A- 14 C, and are in the structure estranged and arranged in the Y direction as indicated by the arrow.  
         [0109]     On the other hand, the Y-direction linear motor structure part  25 A and the Y-direction linear motor structure part  25 B are also in the same structure as the above mentioned X-direction linear motor structure part  20 A. That is, the Y-direction linear motor structure part  25 A is constituted by the Y-direction coils  26 A and the Y-direction core  27 A, and the Y-direction linear motor structure part  25 B is constituted by the Y-direction coils  26 B and the Y-direction core  27 B.  
         [0110]     The Y-direction linear motor structure part  25 A and the Y-direction linear motor structure part  25 B face across the position where the above-mentioned two-dimensional angle sensors  14 A- 14 C are disposed, and they are in the structure arranged in the X direction as indicated by the arrow.  
         [0111]     The Z-direction electromagnet  30  has the function to form a gap between the X-direction linear motor structure part  20 A,  20 B or the Y-direction linear motor structure part  25 A,  25 B provided on the base  11  and the magnet  15  or  16  provided on the stage  12 , when the stage  12  is lifted from the base  11 .  
         [0112]     The Z-direction electromagnet  30  is constituted by the Z-direction coil  31  and the Z-direction core  32 . In order to stabilize the lifting action, it is disposed in the four-corner positions of the base  11  in a rectangular shape, respectively. The mechanism for lifting the stage  12  from the base  11 , other than the magnetic unit used in this embodiment, may include a unit utilizing a compressed air, a unit supporting the base  11  with two or more balls, etc.  
         [0113]     On the other hand, as described above, the X-direction magnet  15  and the Y-direction magnet  16  are disposed on the stage  12 . Although it is not illustrated, four pairs of the magnets  15  and  16  in total are disposed, respectively. Therefore, the magnets  15  and  16  are arranged so as to form a generally square configuration on the bottom of the stage  12 .  
         [0114]     The X-direction magnet  15  is constituted by two or more magnet rows (the set of small magnets) which arranged two or more equivalent permanent magnets in the shape of a straight line so that a polarity might appear by turns. Similarly, the Y-direction magnet  16  is also constituted by two or more magnet rows which arranged two or more equivalent permanent magnets in the shape of a straight line so that a polarity might appear by turns.  
         [0115]     The yoke  17  is disposed in the upper part of each magnets  15  and  16 , and this yoke  17  does so the function which combines magnetically two or more magnets of each which constitute each magnets  15  and  16 .  
         [0116]     In the above-mentioned structure, in the condition of having equipped with the stage  12  to the base  11 , it is constituted so that one of the pair of the X-direction magnets  15  may be located on the X-direction linear motor structure part  20 A, and the other of the pair of the X-direction magnets  15  may be located on the X-direction linear motor structure part  20 B.  
         [0117]     In the condition of having equipped with the stage  12  to the base  11 , it is constituted so that one of the pair of the Y-direction magnets  16  may be located on the Y-direction linear motor structure part  25 A, and the other of the pair of the Y-direction magnets  16  may be located on the Y-direction linear motor structure part  25 B.  
         [0118]     In the condition that the stage  12  is equipped with the base  11 , and it sets in the condition that the stage  12  is lifted over the base  11  with the Z-direction electromagnet  30 . It is constituted so that it may engage with the linear motor structure parts  20 A,  20 B,  25 A, and  25 B which the surface which each magnets  15  and  16  generate confronts.  
         [0119]     In the above-mentioned wearing condition, each magnets  15  and  16  are arranged so that it may intersect perpendicularly to the winding direction of each coils  21 A,  21 B,  26 A, and  26 B established in each linear motor structure parts  20 A,  20 B,  25 A, and  25 B.  
         [0120]     By considering the drive unit as the above-mentioned structure, the direction linear motor structure parts  20 A and  20 B of X and magnet  15  for the directions of X collaborate, and function as a linear motor which drives stage  12  in the X direction as indicated by the arrow.  
         [0121]     Similarly, the direction linear motor structure parts  25 A and  25 B of Y and magnet  16  for the directions of Y collaborate, and function as a linear motor which drives stage  12  in the Y direction as indicated by the arrow.  
         [0122]     That is, in this embodiment, it becomes the structure that  2  sets of linear motors have been arranged at X and each Y both directions, respectively.  
         [0123]     Since comparatively large space can be retained in the center portion of the device having this structure, the surface encoder  24  can be arranged in the center portion. In this embodiment, the structure which disposed scale part  13  in stage  12 , and disposed two-dimensional angle sensors  14 A- 14 C in the base  11 . This is because it is not necessary to connect wiring to scale part  13 .  
         [0124]     However, it is also possible to have structure which disposes scale part  13  in the base  11 , and forms two-dimensional angle sensors  14 A- 14 C in stage  12 .  
         [0125]     In the drive unit in the above-mentioned structure, if only the direction linear motor structure part  20 A of X and the direction linear motor structure part  20 B of X are made to drive in this direction simultaneously, translation of the stage  12  will be carried out in the X direction as indicated by the arrow.  
         [0126]     Similarly, if only the direction linear motor structure part  25 A of Y and the direction linear motor structure part  25 B of Y are made to drive in this direction simultaneously, translation of the stage  12  will be carried out in the direction indicated by the arrow Y in  FIG. 11 .  
         [0127]     The stage  12  is rotated around the Z-axis θZ indicated by the arrow in  FIG. 11 , by making a reverse direction drive each linear motor structure part  20 A which became a pair, and  20 B,  25 A and  25 B, respectively.  
         [0128]     Next, with reference to  FIG. 12 , the principle of moving the stage  12  using the drive unit will be explained.  
         [0129]     In order to simplify description, one linear motor (magnet  15  for the directions of X and the direction linear motor structure part  20 A of X) made to move in the direction of X on stage  12  shall be mentioned as an example, and shall be explained.  
         [0130]      FIG. 12  is a diagram for explaining the principle of moving the stage. When the current is supplied in the X direction by the X-direction coil  21 A- 2  as shown in  FIG. 12 (A), the X-direction magnets  15  stop in the place where the force in alignment with the X-axis arose at between the current and magnet  15  for the directions of X which confronted it, and each produced force balanced with it.  
         [0131]     When the current is supplied by the X-direction coil  21 A- 1  in this condition as shown in  FIG. 12  (B), the rightward force will arise, respectively to the X-direction magnet  15  which confronts the X-direction coil  21 A- 1 .  
         [0132]     As the X-direction magnet  15  (or the stage  12 ) starts to move, as shown in  FIG. 12  (C), according to this force, the magnet is moved to the position where the force produced to the magnet by the X-direction coil  21 A- 1  and the X-direction coil  21 A- 2  being balanced.  
         [0133]     Then, if the supply of the current to the X-direction coil  21 A- 2  is stopped, as shown in  FIG. 12  (D), it will move in the position where the force balances with the current of the X-direction coil  21 A- 1 .  
         [0134]     By the above-mentioned action shown in  FIG. 12  (A)-(D), the X-direction magnet  15  (or the stage  12 ) is moved by Δd which is equivalent to half the distance of the magnet.  
         [0135]     If the current supplied to the X-direction coils  21 A- 1  and  21 A- 2  as mentioned above is driven only in ON and OFF, only movement of every ¼ magnet can be performed. If the ratio of the magnitude of the current supplied by the X-direction coils  21 A- 1  and  21 A- 2  in the condition shown in  FIG. 12  (C) is changed, the X-direction magnet  15  is moved to the position which balanced with the magnitude of each current according to it, the magnet can be moved to an arbitrary position by half-within the limits.  
         [0136]     It can drive freely within limits in which the arrangement of the X-direction magnet  15  exists by changing the direction of the current supplied to the coil according to the polarity of the X-direction magnet  15  which confronts.  
         [0137]     Unlike the normal direct-current motor, in this embodiment, it drives in the shape of a stepping motor near the position where the force always produced on the stage  12  balances. For this reason, open-loop actuation of the stage  12  can be performed by calculating the voltage supplied to each coil  21 A- 1  and  21 A- 2 .  
         [0138]     Although one linear motor (the X-direction magnet  15  and the X-direction linear motor structure part  20 A) which is moved in the X direction on the stage  12  has been mentioned as the example and description of the above-mentioned drive unit explained it.  
         [0139]     The actuation principle of the linear motor which comprises other magnets  15  and  16 , and the X-direction linear motor structure part  20 B and the Y-direction linear motor structure parts  25 A and  25 B are also the same. It is possible to control movement of the direction of X and the direction of Y and the revolution around the Z-axis of the stage  12  by the drive unit in the above-mentioned structure with an one-step configuration.  
         [0140]     It receives for all directions and it is not necessary to have guide structure, and since stage  12  which is a final stage is the structure driven directly, the weight saving of stage device  10 , rigid improvement, and abatement of a manufacturing cost can be aimed at. It enables the servo engine performance to secure to a high frequency region also in a control side by the stage device  10  carrying out a weight saving, and being able to aim at rigid improvement.  
         [0141]     Next, a modification of the above-mentioned stage device  10  will be explained.  FIG. 14  is a diagram showing the composition of a modification of the stage device  10 A in the present embodiment.  
         [0142]     In  FIG. 14  and  FIG. 15 , the same code shall be attached about the same structure as the structure of stage device  10 , and the description shall be omitted. The stage device  10 A of this modification considers the chuck  61 A holding the wafer  60  as the structure which can be detached and attached to the stage  12 A, and it is in the structure in which the scale part  13  is disposed on the chuck  61 A.  
         [0143]     The mounting part  62  is provided in the stage  12 A, and, specifically, the chuck  61 A is in the structure in which insertion or removal is possible in the mounting part  62 .  
         [0144]     Thereby, the chuck  61 A is in the structure which can be detached and attached to the stage  12 A. In the condition that the stage  12 A is equipped, the base of the chuck  61 A is constituted so that it may expose from the base of the stage  12 A.  
         [0145]     The scale part  13  is disposed in the base of the chuck  61 A. Therefore, in the condition of having equipped the stage  12 A with the chuck  61 A, it exposes from the base of the stage  12 A, and the scale part  13  will be in the condition of having confronted with the two-dimensional angle sensors  14  provided in the base  11 .  
         [0146]     Thereby, the two-dimensional angle sensors  14  outputs the laser beam  65  to the scale part  13  and they become possible entering the emitted light beam, they become possible performing position measurement of the stage  12 A. Since the scale part  13  is provided in the wafer  60  and the chuck  61 A dealt with in one in this modification, even if an error arises between the chuck  61 A and the stage  12 A, it is lost that this affects the test result of the surface encoder  24 , and, therefore, highly precise position instrumentation can be performed.  
         [0147]      FIG. 15  is a diagram showing the composition of another modification of the stage device  10 B of the present embodiment. In this modification, it is characterized by allocating the scale part  13  in the tooth-back side of the wafer  60  used as a movable body directly.  
         [0148]     The transparent part  63  is provided in the scale part  13  of the stage  12 B, and the area which confronts so that the laser beam  65  irradiated from two-dimensional angle sensors  14  may be irradiated by the scale part  13 , so that scale part  13  disposed in the tooth-back side of wafer  60  can be checked with the two-dimensional angle sensors  14 .  
         [0149]     The scale part  13  may be the structure provided in one by fixing by sticking on the wafer  60  etc., and the processing wafer  60  directly. Thereby, the scale part  13  serves as structure united with the wafer  60 .  
         [0150]     The transparent part  63  is made of, for example, a glass or transparent resin inserted in the stage  12 B. In this modification, the scale part  13  is disposed on the wafer  60  the very thing used as a movable body, occurrence of an error between the chuck  61 A and the scale part  13  with a possibility of generating with the structure concerning the above-mentioned modification can be prevented, and highly precise position instrumentation can be performed.  
         [0151]     The two-dimensional angle sensors  14  of the stage  12 B, and the area (set up carry out movement range rear-spring-supporter opposite) which confronts even if the scale part  13  is disposed by the wafer  60 , and the transparent part  63  for irradiating the scale part  13   65  is provided, position instrumentation of the stage  12  (or the wafer  60 ) can be ensured.  
         [0152]     The above-mentioned stage device of the invention can be widely applied to not only semiconductor manufacturing devices but also the field of art which needs micro fabrication, such as micromachines, optical communication parts for information technology, etc. That is, many of the current micromachine manufacturing techniques use semiconductor manufacturing technology, and the use of the stage device of the invention will make it possible to manufacture various smaller micromachines. Moreover, in the field of laser beam machining, it is demanded that the stage is moved by a submicron accuracy at a very high speed.  
         [0153]     Furthermore, in order to process a complicated configuration, a stage device having a large number of degrees of freedom is demanded. Although none of the conventional stage devices meets such demands, it is possible for the stage device of the invention to meet the demands of a high level of accuracy, a high speed and a large number of degrees of freedom. The stage device of the invention can be used also as a stage device for laser beam machining.  
         [0154]     Moreover, the stage device of the invention is applicable to not only the above-mentioned fields but also the assembly processes of electronic parts, such as super-precision mechanical devices, super-precision measuring devices or mounters, inspection devices, and other devices in the office automation field.  
         [0155]     The present invention is not limited to the above-described embodiment, and variations and modifications may be made without departing from the scope of the present invention. In the above-described embodiments, the stage device in which the three two-dimensional angle sensors are provided has been explained. However, the present invention is not limited to the specific number of two-dimensional angle sensors in the above-described embodiments. For example, the composition in which only one two-dimensional angle sensor is provided may be sufficient to solve the above-mentioned problems of the related art.  
         [0156]     The present invention is applicable to a stage device which can attain the miniaturization of the stage device and can perform measurement of a position of the stage to the base with high accuracy.  
         [0157]     The disclosure of Japanese Patent Application No. 2004-80603, filed on Mar. 19, 2004, including the specification, drawings and claims, is incorporated herein by reference in its entirety.
This invention relates to a stage device which is moved with high accuracy in an X-Y direction and a rotating direction using a planar motor. The invention is aimed at reducing the size of the stage device and at performing accurately measurement of a position of the stage to the base. The stage device comprises a scale unit having a scale part on the entire plane of the base, and three two-dimensional angle sensors disposed on a bottom surface of a movable stage part. The scale unit and the two-dimensional angle sensors form a surface encode. A position of the movable stage part is measured by the surface encoder.