Patent Publication Number: US-2006017908-A1

Title: Exposure apparatus and semiconductor device manufacturing method

Description:
FIELD OF THE INVENTION  
      The present invention relates to an exposure apparatus and a semiconductor device manufacturing method which utilizes the same and, more particularly, to an exposure apparatus having a mechanism which effectively suppresses vibration generated by driving a stage device, and a semiconductor device manufacturing method which utilizes the exposure apparatus.  
     BACKGROUND OF THE INVENTION  
      As the accuracy of a semiconductor exposure apparatus increases, a higher-performance vibration-damping, vibration control technique is sought for. This is because when vibration occurs in a structure that forms an exposure stage or exposure apparatus main body, it adversely affects exposure. Therefore, a technique is required which insulates the exposure apparatus main body from vibration outside the exposure apparatus, e.g., from an apparatus installation pedestal, and effectively and quickly decreases vibration generated by the operation of a device which includes a driving means, e.g., a stage device, mounted on the exposure apparatus main body.  
      The semiconductor exposure apparatus drives a stage device, where a reticle as the original of a pattern or a substrate such as a silicon wafer to be exposed with the pattern is mounted, with an intermittent operation pattern such as step &amp; repeat or step &amp; scan. When the stage device is driven with this operation pattern, a reaction force is generated. This reaction force should not cause vibration in the exposure apparatus main body. This is because if vibration occurs in the exposure apparatus main body, it adversely affects the performance of the stage device as well as that of an optical system and measurement system which are mounted on the same base and vibration-damping bed where the stage device is mounted.  
      In order to meet this demand, in the semiconductor exposure apparatus, an active vibration-damping device has been developed and employed widely. According to the active vibration-damping device, vibration and position information of the base where the exposure apparatus main body is mounted are detected by sensors. The detection signals are compensated for and fed back to an actuator which applies a control force to the base. A signal from a device including a driving means, e.g., the stage device, mounted on the vibration-damping bed is compensated for and fed forward to the actuator. Thus, vibration of the base and vibration-damping bed is suppressed actively to control their positions and postures.  
      Japanese Patent Laid-Open No. 11-294520 discloses such an active vibration-damping device and an example in which the active vibration-damping device is applied to a semiconductor exposure apparatus. Japanese Patent Laid-Open No. 11-294520 discloses the following active vibration-damping device and a semiconductor exposure apparatus which uses the same. Pneumatic springs which support a vibration-damping bed on an apparatus installation pedestal are utilized as air actuators. An electromagnetic driving linear motor is also employed which is arranged dynamically parallel to the pneumatic spring and applies a control force between the vibration-damping bed and apparatus installation pedestal. Thus, vibration of the vibration-damping bed is decreased and suppressed.  
      According to this exposure apparatus, the position information (displacement), acceleration information, and the like of the vibration-damping bed are detected by sensors and compensated for to obtain a signal. Also, a signal from a device having a driving means, e.g., a stage device, mounted on the vibration-damping bed is compensated for to obtain a signal. Each actuator is controlled on the basis of the two obtained signals and the like.  
      In particular, an active vibration-damping device on which a base where a stage device having a driving unit is mounted is placed, the following control scheme is employed as in exposure apparatuses disclosed in Japanese Patent Laid-Open Nos. 11-294520 and 10-311364. A signal corresponding to the driving reaction force of the stage device mounted on the base is fed forward to actuators which apply a control force to the base of the active vibration-damping device, to quickly decrease and attenuate the vibration.  
      Recently, an exposure apparatus has been developed in which the driving reaction force of a stage device is canceled by a counter mass system to suppress a force acting on a base where the stage device is mounted, so that the base will not be vibrated.  FIG. 8  is a view for explaining the operation of a stage system which uses a counter mass system.  
      The stage system shown in  FIG. 8  is driven by a linear motor. The stage system includes a stage device  31  on which a placing target is to be mounted, and counter masses  32   a  and  32   b . The stage device  31  is connected to the movable element of the linear motor and operates together with the movable element of the linear motor. The counter masses  32   a  and  32   b  are connected to the stator of the linear motor. The stator of the linear motor forms part of the counter masses  32   a  and  32   b . The counter masses  32   a  and  32   b  are supported on a base  1  ( 1   a  and  1   b ) where the stage device  31  is mounted through a structure which includes pneumatic pads or the like and is movable with low friction along a guide bearing, and move in the direction of substantially the same degree of freedom as that of the movable element of the linear motor.  
      In a conventional stage device, the stator of a linear motor is firmly connected to a base on which the entire stage device is mounted. In the above counter mass system, the stator of the linear motor is supported on the base  1  where the stage device  31  is mounted through the movable structure.  
      In this stage device, when the linear motor is driven to operate the stage, the energy and momentum of the stage driving reaction force form the kinetic energy and momentum of the counter masses which include the stator and load mass of the linear motor. In an ideal state, the force is not transmitted to the base.  
      In the stage device  31  shown in  FIG. 8 , a signal obtained by a position sensor  33  ( 33   a  and  33   b ) which detects the position information of the stage device  31  is compensated for by a compensator (not shown), and the linear motor is driven on the basis of the obtained signal, so that the stage device  31  is controlled. Upon driving the stage device  31 , if an acceleration occurs in the stage device  31  in a direction of an arrow a, the driving reaction force of the stage device  31  generates accelerations in the counter masses  32   a  and  32   b  in directions of arrows Aa and Ab shown in  FIG. 8 .  
      In this manner, the energy and momentum of the stage driving reaction force form the kinetic energy and momentum of the counter masses  32   a  and  32   b  which include the linear motor stator and load mass to suppress any force from acting on the base  1 . In an ideal state, the force is not transmitted to the base  1 . Consequently, the base  1  where the stage device  31  including these constituent elements is mounted does not vibrate largely. The stage device  31  which employs the counter masses  32   a  and  32   b  in this manner can be suitably used in a semiconductor exposure apparatus.  
      The stage system shown in  FIG. 8  is described as one which functions in the moving direction of one degree of freedom. A stage device, e.g., an X-Y stage, which has two degrees of kinetic freedom can similarly form a stage system which uses counter masses.  FIG. 9  is a view showing an example of the arrangement of a counter mass system on an X-Y stage which is a stage device having two degrees of kinetic freedom.  
      In the X-Y stage shown in  FIG. 9 , a stage device  41  on which a placing target is to be mounted is a structure which can move in the directions of two degrees of freedom, e.g., X and Y directions, and can be moved in the X direction by an X-direction moving member  42  and in the Y direction by a Y-direction moving member  43 . The stage device  41  is horizontally supported on a crossbar structure formed of the X-direction moving member  42  and Y-direction moving member  43  which do not restrict the operations of each other, and can move in both the X and Y directions.  
      An X-direction linear motor applies a thrust between the X-direction moving member  42  and X-direction counter masses  44   a  and  44   b . In this case, the X-direction moving member  42  serves as a movable element, and the X-direction counter masses  44   a  and  44   b  serve as stators. Similarly, a Y-direction linear motor applies a thrust between the Y-direction moving member  43  and Y-direction counter masses  45   a  and  45   b . In this case, the Y-direction moving member  43  serves as a movable element, and the Y-direction counter masses  45   a  and  45   b  serve as stators. The X-direction counter masses  44   a  and  44   b  and Y-direction counter masses  45   a  and  45   b  are supported on the base  3  where an X-Y stage is mounted through structures that can respectively move in the X and Y directions.  
      In a conventional X-Y stage, the stators of the linear motors are firmly connected to a base on which the entire stage device is mounted. In the counter mass system, the counter masses which are firmly connected to the stators of the linear motors are supported on the base where the stage device is mounted through the movable structure.  
      In this stage device, when the linear motors are driven to operate the X-Y stage, the energy and momentum of the stage driving reaction force form the kinetic energy and momentum of the counter masses which include the linear motor stators and load masses in both the X and Y directions. Accordingly, in an ideal state, the force is not transmitted to the base, and consequently the base where the stage device including these constituent elements is mounted is not vibrated largely.  
      In the stage system shown in  FIG. 9 , signals obtained by position sensors  46  ( 46   a  and  46   b ) and  47  ( 47   a  and  47   b ) which detect the position information of the stage device  41  are compensated for by a compensator (not shown), and the linear motors are driven on the basis of the obtained signals, so that the stage device  41  is controlled. Upon driving the stage device  41 , if an acceleration occurs in the stage device  41  and X-direction moving member  42  in a direction of an arrow a, the driving reaction forces of the stage device  41  and X-direction moving member  42  generate accelerations in the X-direction counter masses  44   a  and  44   b  in directions of arrows Aa and Ab shown in  FIG. 9 . If an acceleration occurs in the stage device  41  and Y-direction moving member  43  in a direction of an arrow b, the driving reaction forces of the stage device  41  and Y-direction moving member  43  generate accelerations in the Y-direction counter masses  45   a  and  45   b  in directions of arrows Ba and Bb in  FIG. 9 .  
      In this manner, the energies and momenta of the stage driving reaction forces form the kinetic energies and momenta of the counter masses which include the linear motor stators and load masses to suppress any force from acting on a base  3 . In an ideal state, the force is not transmitted to the base. Consequently, the base  3  where the stage device including these constituent elements is mounted does not vibrate largely. Hence, a stage device which employs such counter masses in this manner can be suitably used in a semiconductor exposure apparatus.  
      As described above, in the stage system which uses these counter masses, the stage device and counter masses are operated at accelerations and with operation strokes that match their mass ratio, so that the momenta in both the stage device and counter masses are theoretically reserved, and the forces acting on the base and vibration-damping bed where the stage device is mounted can be decreased to be very small. Also, the position of center of gravity of the entire movable object including the stage and counter masses joined together can be made substantially immovable.  
      Also, a method can also be employed which includes, in addition to the structure described above, actuators for externally applying a control force to the counter masses. The positions, velocities, and accelerations of the counter masses as well as the stage device are controlled by the actuators so that the counter masses are operated actively. In this case, since the operations of the counter masses as well as the stage device can be controlled, for example, the stroke over of the counter masses can be avoided. Thus, the exposure apparatus can run in a more appropriate state. In this case, basically, the counter masses are driven by the driving reaction force of the stage device. Thus, substantially no thrust is generated in the actuators which externally apply a control force to the counter masses.  
      In the counter mass system described above, the driving reaction force of the stage device is canceled by a mechanism that does not include a base, and vibration occurring in the base where the semiconductor exposure apparatus is mounted can be decreased. This is different from the conventional general vibration control scheme of feeding forward the driving reaction force of the stage device to the actuator of the active vibration-damping device. Therefore, the stage driving reaction force and the feed-forward force of the actuator which applies a control force to the base do not cause the structural resonance of the base or do not deform the base. The base vibration can be decreased and suppressed more preferably.  
      In the stage system employing the conventional counter mass system, sometimes the driving reaction force cannot be completely canceled. To completely cancel the driving reaction force of the stage device by using the counter mass system, ideally, two stage devices having completely the same specification and characteristics must be arranged such that their axes in which driving reaction forces occur coincide with each other completely, and the two stages must be operated under completely the same operation conditions.  
      In actual design and application of an apparatus, it is very difficult to arrange two stage devices having completely the same specifications such that their axes in which driving reaction forces occur coincide with each other completely. This is because very often the arrangement and design of the unit are spatially limited.  
      Therefore, as a stage system which employs a counter mass system, the following arrangement is a feasible embodiment. The movable elements of linear motors which drive the stage system are attached to the stage device. The stators of the linear motors are attached to counter masses. The counter masses are supported to be movable with respect to the stage device and a base where the unit of the stage device is mounted. This arrangement is described with reference to  FIGS. 8 and 9 .  
      Sometimes, however, the kinetic energy, momentum, driving reaction force, and the like of the stage device are not entirely transmitted to the counter masses due to the friction force and damping force generated in bearings (not shown in  FIGS. 8 and 9 ) and by the influence or the like of the wiring lines and pipes arranged among the base, stage device, and counter masses. In this case, the kinetic energy and momentum of the stage device do not balance with the kinetic energy and momentum of the counter masses. The difference in kinetic energy and momentum is transmitted to the base where the stage device and counter masses are both mounted. Consequently, vibration occurs in the base.  
      As described above, when the operations of the counter masses are also to be controlled actively so that the counter mass system functions, the mass ratio of the stage device to counter masses is a very important control parameter. Unless the control operation is performed to precisely reflect the mass ratio, the momentum cannot be reserved between only the stage device and counter masses, and consequently a thrust is transmitted to the base where the stage device is mounted, thus vibrating the base. In practice, the stage device and counter masses are structures having comparatively large weights, and accordingly it is difficult to obtain their masses sufficiently accurately and to reflect them in the control operation. Due to the variations in thrust characteristics of the actuators that drive the stage device and counter masses and other disturbances, sometimes the control parameters of the counter mass system need adjustment. In this case, a parameter corresponding to the mass ratio must be adjusted in a trial-and-error manner. If parameter adjustment is not performed sufficiently accurately, the counter mass system does not operate appropriately, and a thrust acts on the base to vibrate it.  
     SUMMARY OF THE INVENTION  
      The present invention has been made in view of the above problems, and has as its object to provide an apparatus and method which decrease the influence, which is caused by the driving reaction force of a stage device in a base where the stage device is mounted and which cannot be sufficiently canceled even by a counter mass system, to decrease and suppress vibration of the base.  
      According to the first aspect of the present invention, there is provided an exposure apparatus comprising a base, a stage device which is mounted on the base and moves in a predetermined direction, a counter mass which is mounted on the base and moves in a direction opposite to the predetermined direction as the stage device moves, a sensor which detects a motion physical value of each of the stage device and counter mass, and an actuator which applies a force to the base on the basis of a detection result of the sensor.  
      According to the second aspect of the present invention, there is provided a semiconductor device manufacturing method comprising an exposure step of transferring a pattern of an original onto a substrate by using an exposure apparatus described above, and a developing step of developing the substrate on which the pattern has been transferred.  
      According to the present invention, there is provided an apparatus and method which decrease the influence, which is caused by the driving reaction force of a stage device in a base where the stage device is mounted and which cannot be sufficiently canceled even by a counter mass system, to decrease and suppress the vibration of the base.  
      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  
      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.  
       FIG. 1  is a plan view showing the structure of an exposure apparatus according to the first preferred embodiment of the present invention;  
       FIG. 2  is a side view showing the structure of the exposure apparatus according to the first preferred embodiment of the present invention;  
       FIG. 3  is a block diagram showing the structure of the exposure apparatus according to the first preferred embodiment of the present invention;  
       FIG. 4  is a plan view showing the structure of an exposure apparatus according to the second preferred embodiment of the present invention;  
       FIG. 5  is a side view showing the structure of the exposure apparatus according to the second preferred embodiment of the present invention;  
       FIG. 6  is a block diagram showing the control configuration of the exposure apparatus according to the second preferred embodiment of the present invention;  
       FIG. 7  is a view showing the structure of an exposure apparatus according to a preferred embodiment of the present invention;  
       FIG. 8  is a view showing an example of a stage device including a conventional counter mass system;  
       FIG. 9  is a view showing another example of the stage device including the conventional counter mass system; and  
       FIG. 10  is a flowchart showing the flow of an entire semiconductor device manufacturing process. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Exposure apparatuses according to the preferred embodiments of the present invention will be described with reference to the accompanying drawings.  
       FIG. 7  is a view showing an example of the structure of an exposure apparatus according to a preferred embodiment of the present invention. In the apparatus shown in  FIG. 7 , a stage base  93  and a substrate stage device  94  mounted on the stage base  93  are set on an apparatus installation foundation  100  through anti-vibration support mounts  92   a . The substrate stage device  94  is used to place on it a substrate (e.g., a silicon wafer) on which a pattern is to be exposed. On the apparatus installation foundation  100 , a lens barrel base  97  which mounts a reticle stage device  95  and an optical lens system  96  is set through anti-vibration support mounts  92   b . The optical lens system  96  is used to transfer the pattern of an original called a reticle onto the substrate.  
      The anti-vibration support mounts  92   a  and  92   b  are not directly set on the apparatus installation foundation  100  but are fixed on a foundation structure  91  called a pallet or base frame. The foundation structure  91  serves as a reference to maintain the mutual positional relationship between devices respectively mounted on the anti-vibration support mounts  92   a  and  92   b  and, although not shown in  FIG. 7 , between other devices which form an exposure apparatus and are not mounted on the anti-vibration support mounts  92   a  and  92   b . The foundation structure  91  also serves as a foundation member to place the entire exposure apparatus and transport the exposure apparatus collectively.  
      The optical lens system  96  is arranged between the reticle stage device  95  and substrate stage device  94 . Exposure light from an illumination optical system  98  radiates the reticle to project and expose a pattern on the reticle onto the substrate through the optical lens system  96 .  
      Exposure apparatuses are classified into collective exposure type (stepper), scanning exposure type (scanner), and the like according to the exposure schemes. In the case of a collective exposure type exposure apparatus, while the substrate stage device  94  is driven sequentially by an intermittent operation scheme called step &amp; repeat, a certain constant exposure area, e.g., an area corresponding to one integrated circuit such as an IC, is exposed collectively. In the case of a scanning exposure type exposure apparatus, the substrate stage device  94  and reticle stage device  95  are operated in synchronism with each other to scan and expose the pattern on the reticle onto the substrate.  
      In the semiconductor exposure apparatus according to the preferred embodiment of the present invention, with the above structure, when a counter mass system as described above is applied to at least one of the substrate stage device  94  and reticle stage device  95 , the influence of the driving reaction force which is applied by the stage device  94  or  95  to the stage base  93  and lens barrel base  97  where the stage device  94  and  95  are mounted and which cannot be completely canceled by the counter mass system is decreased to decrease and suppress the vibration of the base  93  or  97 .  
     First Embodiment  
       FIGS. 1 and 2  are views for explaining the structure and operation of a unit around a stage device that forms an exposure apparatus according to the first preferred embodiment of the present invention.  FIGS. 1 and 2  show a stage device having a kinetic freedom in the direction of one degree of freedom.  FIG. 1  is a plan view of the exposure apparatus, and  FIG. 2  is a side view of the exposure apparatus. This unit corresponds to the reticle stage device  95  in the exposure apparatus shown in  FIG. 7 .  
      In this manner, the reticle stage device  95  is a stage device which has one degree of kinetic freedom. Actually, the stage device sometimes has not only one degree of freedom in a Y direction shown in  FIG. 1  but also a kinetic freedom in X, θz, or the like for reticle alignment. Note that a comparatively large driving reaction force is generated in one degree of freedom, i.e., in the Y direction in which the reticle stage device  95  is scanned.  
      As the substrate stage device  94 , a stage device having two degrees of freedom directions, e.g., an X-Y stage, is employed to repeatedly expose the pattern on the reticle in order to print a plurality of patterns onto the substrate. This will be described later.  
      A stage device having a kinetic freedom in a direction of one degree of freedom will be described. As shown in  FIGS. 1 and 2 , the semiconductor exposure apparatus according to the first preferred embodiment of the present invention schematically has the following constituent elements. More specifically, the semiconductor exposure apparatus according to this embodiment includes a stage device  51  which places on it a placing target such as a reticle and accurately positions the placing target, and counter masses  52   a  and  52   b  serving as inertia masses which operate in the direction of the same degree of freedom as the stage device  51 .  
      The stage device  51  is supported by a structure on which a placing object such as a reticle is mounted and which can move in the direction of one predetermined degree of freedom (the Y direction in  FIGS. 1 and 2 ) determined on a base  1  ( 1   a  and  1   b ). The stage device  51  is driven by a linear motor. The stage device  51  is connected to the movable element of the linear motor, and operates together with the movable element of the linear motor. The counter masses  52   a  and  52   b  are connected to the stator of the linear motor. The counter masses  52   a  and  52   b  are supported on the base  1  where the stage device  51  is mounted through a structure which includes pneumatic pads or the like and is movable with low friction along a guide bearing, and operate in the direction of the same degree of freedom as that of the movable element of the linear motor.  
      In this stage system, when the stage device  51  is driven by the linear motor, its driving reaction force acts on the counter masses  52   a  and  52   b  to operate in the direction of the same degree of freedom as that of the stage device  51  but in the opposite direction. The stator of the linear motor which drives the stage device  51  is supported on the base where the stage device  51  is mounted through the movable structure. Even when the linear motor is driven to operate the stage device, the energy and momentum of the stage driving reaction force form the kinetic energy and momentum of the counter masses including the linear motor stators and load masses. Consequently, in an ideal state, the force is not transmitted to the base, and the stage can be operated without largely vibrating the base where the stage system including these constituent elements is mounted.  
      In the semiconductor exposure apparatus according to this embodiment, sensors are employed for the stage device  51 , having the above structure, and the counter masses  52   a  and  52   b  to detect their motion physical values. More specifically, the stage device  51  includes a position sensor  61  ( 61   a  and  61   b ) which detects and outputs the position information of the stage device  51 , a velocity sensor  62  which detects and outputs the velocity information of the stage device  51 , and an acceleration sensor  63  which detects and outputs the acceleration information of the stage device  51 . The position sensor  61 , velocity sensor  62 , and acceleration sensor  63  respectively detect the motion physical values, i.e., the position information, velocity information, and acceleration information in the operating direction of the stage device  51 .  
      The counter masses  52   a  and  52   b  respectively include position sensors  64   a  and  64   b  which detect and output the position information of the corresponding counter masses, velocity sensors  65   a  and  65   b  which detect and output the velocity information of the corresponding counter masses, and acceleration sensors  66   a  and  66   b  which detect and output the acceleration information of the corresponding counter masses. The position sensors  64   a  and  64   b , velocity sensors  65   a  and  65   b , and acceleration sensors  66   a  and  66   b  respectively detect the motion physical values, i.e., the position information, velocity information, and acceleration information in the operating direction of the counter masses  52   a  and  52   b.    
      As the position sensor  61  which detects and outputs the position information of the stage device  51 , a laser interferometer which is widely used in this field because of the requirements in accuracy or the like can be used. As the velocity sensor  62  which detects and outputs the velocity information of the stage device  51 , a geophone sensor or another velocity sensor can be used. As the acceleration sensor  63  which detects and outputs the acceleration information of the stage device  51 , various types of servo or piezoelectric accelerometers can be used.  
      When a laser interferometer is used as the position sensor  61 , in place of using the velocity sensor  62  and acceleration sensor  63 , even if the motion physical values of the output signals of the laser interferometer are converted appropriately to calculate the velocity and acceleration, good operation can be performed.  
      Similarly, as the position sensors  64   a  and  64   b  which detect and output the position information of the respective counter masses  52   a  and  52   b , various types of position sensors such as laser interferometers or encoders can be used.  
      As the velocity sensors  65   a  and  65   b  which detect and output the velocity information of the counter masses  52   a  and  52   b , geophone sensors or another type of velocity sensors can be used. As the acceleration sensors  66   a  and  66   b  which detect and output the acceleration information of the counter masses  52   a  and  52   b , various types of servo or piezoelectric accelerometers can be used.  
      When laser interferometers are used as the position sensors  64   a  and  64   b , in place of using the velocity sensors  65   a  and  65   b  and acceleration sensors  66   a  and  66   b , even if the motion physical values of the output signals from the laser interferometers are converted appropriately to calculate velocities and accelerations, good operation can be performed.  
      In employing a control scheme to be described later, assume that the apparatus operates without any problem when at least one of the sensors is omitted. In this case, at least one of the position sensors  61 ,  64   a , and  64   b , at least one of the velocity sensors  62 ,  65   a , and  65   b , and at least one of the acceleration sensors  63 ,  66   a , and  66   b  may be omitted.  
      The stage system which includes the stage device  51  and counter masses  52   a  and  52   b  described above is mounted on the base  1 . The base  1  is supported in an anti-vibration manner on a foundation structure  7  set on an apparatus installation foundation by anti-vibration supports  2 . In the structure shown in  FIGS. 1 and 2 , the base  1  includes the two structures  1   a  and  1   b  which are firmly connected to each other through support members  8 . Alternatively, the base  1  may be an integral structure. In  FIG. 2 , the stage device  51  is assumed to be a reticle stage device to form an optical lens system  9  of the exposure apparatus.  
      The base  1  includes actuators  11  ( 11   a  to  11   h ) which apply a control force to the base  1 . The thrust generated by the actuators  11  ( 11   a  to  11   h ) is controlled on the basis of signals obtained by a compensator  6  shown in  FIG. 3 .  
      As shown in  FIG. 3 , output signals from the position sensor  61 , velocity sensor  62 , acceleration sensor  63 , position sensors  64   a  and  64   b , velocity sensors  65   a  and  65   b , and acceleration sensors  66   a  and  66   b  are input to the compensator  6  and compensated. The actuators  11  ( 11   a  to  11   h ) are driven by a driving circuit  10  on the basis of the operation results obtained by the compensator  6 .  
      In FIGS.  1  to  3 , the actuators  11  include the eight actuators  11   a  to  11   h . The number of actuators  11  is not limited to eight as far as it is sufficient to realize a required control performance.  
      As shown in  FIGS. 1 and 2 , the actuators  11  ( 11   a  to  11   h ) which apply the control force to the base  1  include at least either the actuators ( 11   a  to  11   d ) which apply a control force to the base  1  in the vertical direction or the actuators ( 11   e  to  11   h ) which apply a control force to the base  1  in the horizontal direction. Because of the control arrangement to be described later, if substantially no control force need be applied, some of the actuators  11  ( 11   a  to  11   h ) may be omitted. As the actuators  11  which apply the control force to the base  1 , electromagnetic driving linear motors or the like are desirably used.  
      As the anti-vibration supports  2  which support the base  1  in an anti-vibration manner, it is desirable to use one having a pneumatic driving actuator including a pneumatic spring and an electropneumatic proportional valve or the like which adjusts the internal pressure of the pneumatic spring. In this case, a position sensor which detects and outputs a displacement amount (position information) of the base  1  from a reference position and a vibration sensor which detects and outputs the velocity information or acceleration information of the base  1  are desirably arranged. A base vibration compensator is desirably formed which performs compensation to decrease the vibration of the base on the basis of at least one of the output signal from the position sensor and the output signal from the vibration sensor. The pneumatic driving actuator is desirably controlled on the basis of the compensation result obtained by the base vibration compensator, so that the control operation is performed to decrease the vibration of the base  1 . More specifically, an active vibration-damping device is desirably formed which maintains the position and posture of the base  1  in a predetermined state by using the position sensor, vibration sensor, base vibration compensator, pneumatic driving actuator, and the like, and actively controls the vibration of the base  1 .  
      When the active vibration-damping device is used as the anti-vibration supports  2 , the actuators  11  ( 11   a  to  11   h ) may be used as the actuators that control the vibration of the base  1  on the basis of an output signal from a base vibration sensor. When such an active vibration-damping device is employed, the vibration of the base  1  which is caused by a disturbance transmitted to the base  1  can be decreased quickly and appropriately.  
      The semiconductor exposure apparatus according to this embodiment includes the constituent elements described above. The operation of the semiconductor exposure apparatus according to this embodiment will be described in detail.  
      In the semiconductor exposure apparatus according to this embodiment, when the stage device  51  shown in  FIG. 1  is driven in a direction of an arrow a shown in  FIG. 1  on the basis of a drive command signal obtained by compensating the position detection signal from the position sensor  61 , the counter masses  52   a  and  52   b  operate in directions of arrows Aa and Ab shown in  FIG. 1 , i.e., in the direction of the same degree of freedom as that of the stage device  51  but in the opposite direction.  
      This operation takes place when a thrust generated between the movable element of the stage driving linear motor attached to the stage device  51  and the stator of the stage driving linear motor attached to the counter masses  52   a  and  52   b  is exerted on the stage device  51  and counter masses  52   a  and  52   b  which are both supported movably.  
      In the stage system having this structure, the reaction force of the driving force which is generated when the stage device  51  is driven is transmitted not to the base  1  where the stage system is mounted but to the counter masses  52   a  and  52   b . Thus, the energy of the driving reaction force is converted into the kinetic energies of the counter masses  52   a  and  52   b . The force acting on the base  1  can be greatly reduced than in the conventional stage device in which the stator of the stage driving linear motor is fixed to the base. As a result, the vibration of the base  1  can be suppressed small.  
      Ideally, the stage device  51  having the above structure desirably operates such that its kinetic energy and momentum are entirely transmitted to the counter masses  52   a  and  52   b  while a force caused by stage driving is not transmitted to the base  1  at all. Then, no disturbance acts on the base  1 , and no vibration is caused by disturbance.  
      Sometimes, however, the kinetic energy, momentum, driving reaction force, and the like of the stage device  51  are not entirely transmitted to the counter masses  52   a  and  52   b  due to the friction force and damping force generated in the bearings (not shown) of the stage device  51  and counter masses  52   a  and  52   b  and by forces or the like which are generated when the wiring lines and pipes extending from the base  1  to the stage device  51  and counter masses  52   a  and  52   b  serve as springs. In this case, the kinetic energy and momentum of the stage device  51  do not balance with the kinetic energy and momentum of the counter masses  52   a  and  52   b . The difference in kinetic energy and momentum is transmitted to the base  1  where both the stage device  51  and counter masses  52   a  and  52   b  are mounted. Consequently, vibration occurs in the base  1 .  
      In the exposure apparatus according to this embodiment, the kinetic energy, momentum, and driving reaction force that cannot be completely canceled between the stage device  51  and counter masses  52   a  and  52   b  are estimated from the motion physical values such as position information (displacement), velocity information, and acceleration information of the stage device  51  and counter masses  52   a  and  52   b . The actuators which apply the control force to the base  1  are controlled on the basis of the estimated signals to decrease the vibration of the base  1 .  
      The practical control operation of the exposure apparatus according to this embodiment will be described. First, a device which performs the control operation by estimating the thrust, momentum, and the like transmitted to the base  1  on the basis of the acceleration signals of the stage device  51  and counter masses  52   a  and  52   b , and a control method for the device will be described.  
      The stage device  51  shown in  FIG. 1  is driven by the drive command signal in accordance with a predetermined driving pattern. The counter masses  52   a  and  52   b  are operated by the driving reaction force of the stage device  51  in a direction opposite to the driving direction of the stage device  51 . At this time, the acceleration information of the stage device  51  and counter masses  52   a  and  52   b  is detected by the acceleration sensors  63 ,  66   a , and  66   b . The output signals from the acceleration sensors are input to the compensator  6 . The compensator  6  estimates the driving reaction force of the stage device  51  which cannot be canceled by the operation of the counter masses  52   a  and  52   b.    
      In the case of a stage device which is driven in the direction of one degree of freedom, the driving reaction force acts in the stage driving direction with one translational degree of freedom and directions of two rotational degrees of freedom about two axes perpendicular to the stage driving direction. Accordingly, the relationship between the thrust and momentum of the stage device and those of the counter masses is formulated concerning the kinetic directions of the three degrees of freedom.  
      Regarding the thrust and momentum components of the stage device and counter masses which are proportional to the accelerations, the following equation of motion is established:  
               [         fy           Mqx           Mqz         ]     =       [         m       M1       M2             m   ×   1   ⁢   z0           M1   ×   1   ⁢   z1           M2   ×   1   ⁢   z2               m   ×   1   ⁢   x0           M1   ×   1   ⁢   x1           M2   ×   1   ⁢   x2           ]     ⁡     [         ay           aY1           aY2         ]               (   1   )             
 
 where m, M 1 , and M 2  are the masses of the stage device  51  and counter masses  52   a  and  52   b , respectively, ay, aY1, and aY2 are the acceleration information of the stage device  51  and counter masses  52   a  and  52   b , respectively, lz0 to lz2 are the Z-coordinates of the positions of centers of gravity of the stage device  51  and counter masses  52   a  and  52   b  with reference to the position of center of gravity of the base  1  as the origin point, and lx0 to lx2 are the X-coordinates of the positions of centers of gravity of the stage device  51  and counter masses  52   a  and  52   b  with reference to the position of center of gravity of the base  1  as the origin point. lz0 to lz2 and lx0 to lx2 can be obtained from the mechanical design information and the like of the stage device  51  and counter masses  52   a  and  52   b . In the XYZ coordinate system, as shown in  FIGS. 1 and 2 , the operating direction (direction of horizontal one degree of freedom) of the stage device  51  and counter masses  52   a  and  52   b  is defined as the Y-axis, a horizontal axis perpendicular to the Y-axis is defined as the X-axis, and the vertical axis is defined as the Z-axis. Also, the rotational directions about the X-, Y-, and Z-axes are respectively defined as θx, θy, and θz. 
 
      fy, Mqx, and Mqz in the left member are the thrust and moment in the Y, θx, and θz directions which are left without being canceled by the operation of the stage device  51  and the operations of the counter masses  52   a  and  52   b . In other words, fy, Mqx, and Mqz are the differences in operation between the stage device and counter masses. If fy, Mqx, and Mqz are not zero, the thrust and moment are not canceled between the stage device and counter masses but leak to another portion, i.e., the base  1 .  
      When the control force is distributed among the actuators  11  ( 11   a  to  11   h ) to cancel the thrust corresponding to the left member of the equation, even if the stage driving reaction forces are not canceled between the stage device and counter masses and leaking forces are input to the base  1 , they can be canceled by the actuators  11  ( 11   a  to  11   h ) to decrease the vibration of the base  1 .  
      The compensator  6  estimates fy, Mqx, and Mqz in the left member in accordance with equation (1), and generates control command signals to control the actuators  11  ( 11   a  to  11   h ) which apply a control force to the base  1 , in order to cancel fy, Mqx, and Mqz. More specifically, the compensator  6  subjects estimated fy, Mqx, and Mqz to gain compensation and filtering when necessary. When the actuators  11  are high-response actuators such as electromagnetic driving linear motors, the compensator  6  can perform control calculation of mainly gain compensation on the basis of the information on fy, Mqx, and Mqz which are estimated in accordance with equation (1), and distribute the obtained control command signal among the respective actuators.  
      In this case, the thrust to be generated by the actuators  11  ( 11   a  to  11   h ) is estimated as thrusts fy, Mqx, and Mqz in the Y, θx, and θz directions. The compensator  6  calculates distributional thrusts to distribute the thrusts among the plurality of actuators  11  ( 11   a  to  11   h ), in order to generate desired thrusts and moments introduced on the basis of equation (1) in the Y, θx, and θz directions respectively. Thrust distribution equation can be formulated on the basis of the geometric arrangement of the actuators  11  ( 11   a  to  11   h ) and their arranging directions.  
      The plurality of actuators  11  ( 11   a  to  11   h ) are driven on the basis of the control command signals introduced by the compensator  6  in this manner, in order to apply a control force to the base  1 . The thrusts and moments which are generated in accordance with equation (1) and cannot be completely canceled by the stage device  51  and counter masses  52   a  and  52   b  but transmitted to the base  1  are canceled by the actuators  11  in a real-time manner. Consequently, the vibration of the base  1  can be suppressed small.  
      In an apparatus which includes the stage device  51  and counter masses  52   a  and  52   b  and decreases the stage driving reaction force by their mutual operations, the stage driving reaction force can be canceled and decreased by the mutual operations of the constituent elements, thus decreasing the vibration of the base where the constituent elements are mounted. If, however, the mutual operations cannot completely cancel the stage driving reaction force and a thrust and moment are left to be transmitted to the base where the stage device  51  and counter masses  52   a  and  52   b  are mounted, the force acting on the base must be decreased by using some means.  
      In the exposure apparatus according to this embodiment, as described above, the thrust and moment which are not completely canceled by the operations of the stage device  51  and counter masses  52   a  and  52   b  but transmitted to the base  1  are estimated on the basis of the signals from the sensors which detect the motion physical values, e.g., the acceleration information, of the stage device  51  and counter masses  52   a  and  52   b , and the actuators which apply the control force to the base  1  are controlled on the basis of the estimated thrust and moment. Thus, a higher vibration control performance that cannot be obtained by the conventional apparatus can be obtained. Consequently, the vibration of the stage device and other precision devices mounted on the base is decreased to realize an improvement in performance of the devices to be mounted on the exposure apparatus or the like.  
      In the above description, for the sake of descriptive simplicity, the thrust to be transmitted to the base  1  is only a term proportional to the acceleration. In fact, however, exchange of a force and moment which cannot be expressed by only a term proportional to the acceleration are not sometimes negligible, e.g., friction in pneumatic bearings to movably support the stage device  51  and counter masses  52   a  and  52   b , or resistance caused by a counter electromotive force generated between the movable portion and stationary portion of the linear motor which forms the stage device. In this case, the thrust and moment transmitted to the base  1  can be estimated by adding a term proportional to the velocity and a term proportional to the position. The thrust and moment transmitted to the base  1  can be estimated by the following equation. Regarding the term proportional to the velocity in the following equation, not only the velocities of the stage device and counter masses with respect to the base  1 , but also the relative velocity between the stage device and counter masses is considered.  
               [         fy           Mqx           Mqz         ]     =         [         m       M1       M2             m   ×   1   ⁢   z0           M1   ×   1   ⁢   z1           M2   ×   1   ⁢   z2               m   ×   1   ⁢   x0           M1   ×   1   ⁢   x1           M2   ×   1   ⁢   x2           ]     ⁡     [         ay           aY1           aY2         ]       +               [         d11       d12       d13           d21       d22       d23           d31       d32       d33         ]     ⁡     [         vy           vY1           vY2         ]       +       [         k11       k12       k13           k21       k22       k23           k31       k32       k33         ]     ⁡     [         py           pY1           pY2         ]                     (   2   )             
 
      In equation (2), the same symbols as in equation (1) represent the same parameters. Also, vy, vY1, and vY2 are the velocities of the stage device  51  and counter masses  52   a  and  52   b , respectively, py, pY1, and pY2 are the positions (displacements) of the stage devices  51  and counter masses  52   a  and  52   b , respectively, and dij and kij (i, j=1, 2, 3) are a term proportional to the velocity and a term proportional to the position, respectively.  
      The term proportional to the velocity and the term proportional to the position may be experimentally estimated by, e.g., fixing any two of the stage device  51  and counter masses  52   a  and  52   b  immobile, applying a control force to the linear motor, and measuring the response characteristics of the respective motion physical values (ay, aY1, aY2, vy, vY1, vY2, py, pY1, and pY2).  
      In equations (1) and (2), as the term proportional to the acceleration, the mass m of the stage device  51  and the masses M 1  and M 2  of the counter masses  52   a  and  52   b  are used. When the values of the masses m, M 1 , and M 2  are not clearly known, they may be experimentally obtained in the same manner.  
      The structure for controlling the actuators on the basis of the thrusts and moments estimated by the above equation (2) to decrease and suppress the vibration of the base is the same as that described above, and a description thereof will be omitted.  
      When the term proportional to the velocity and the term proportional to the position are considered in this manner, the thrust and moment to be transmitted from the stage system to the base  1  can be estimated more accurately, and the vibration of the base  1  can be suppressed and decreased more effectively.  
      In actual control operation, not all the motion physical values of the position information (displacement), velocity information, and acceleration information of the stage device  51  and counter masses  52   a  and  52   b  need be used for control. As far as a sufficient effect can be obtained, a structure which uses at least one of the position information (displacement), velocity information, and acceleration information is also included in the present invention. Naturally, a control operation may be performed in which only a term proportional to the acceleration is considered as in equation (1). In this case, sensors which detect motion physical values that are not to be used may be omitted. Such control operation may be performed not for all of the Y, θx, and θz directions but for at least one of them when necessary.  
      As apparent from equation (2), fy, Mqx, and Mqz can also be determined by the values of vx, vY1, and vY2. The motion physical values concerning these velocity information may be obtained not by using a velocity sensor as in the above description, but output signals from relative velocity sensors which are the relative velocities (vx−vY1) and (vx−vY2) between the stage device and counter masses may be used as the motion physical values.  
      Means for obtaining the position information (displacement), velocity information, and acceleration information of the stage device and counter masses are not limited to sensors which detect their motion physical values. For example, the position information (displacement), velocity information, and acceleration information can naturally be obtained on the basis of the drive profile information on the stage device and counter masses.  
     Second Embodiment  
      In the first embodiment, the stage device operates in the direction of one degree of freedom. This stage device corresponds to the reticle stage device  95  in the exposure apparatus described with reference to  FIG. 7 . The structure of the present invention can also be applied to a stage device, e.g., a substrate stage, which moves in the directions of two degrees of freedom. In a stage system including a stage device which operates in the directions of two degrees freedom and counter masses configured to cancel the driving reaction force of the stage device, a device will be described in which a thrust and moment which are not completely canceled by the mutual operations of the stage device and counter masses but transmitted to a base where the stage device and counter masses are mounted are estimated, and actuators which apply a control force to the base are controlled on the basis of estimation signals to decrease and suppress the vibration of the base.  
       FIGS. 4 and 5  are views for explaining the structure and operation of a unit around a stage device that forms an exposure apparatus according to the second preferred embodiment of the present invention.  FIGS. 4 and 5  show a stage device having a kinetic freedom in the directions of two degrees of freedom.  FIG. 4  is a plan view of the exposure apparatus, and  FIG. 5  is a side view of the exposure apparatus. This unit corresponds to the substrate stage device  94  in the exposure apparatus shown in  FIG. 7 . As the substrate stage device  94 , a stage device having a kinetic freedom in directions of two degrees of freedom, e.g., an X-Y stage, is employed which repeatedly exposes the pattern on the reticle to print a plurality of patterns onto the substrate.  
      As shown in  FIGS. 4 and 5 , the exposure apparatus according to the second preferred embodiment of the present invention includes the following constituent elements. More specifically, in the apparatus according to this embodiment, a stage device  71  on which a placing target such as a substrate is to be mounted is a structure which can move in the directions of two degrees of freedom, e.g., X and Y directions, and can be moved in the X direction by an X-direction moving member  72  and in the Y direction by a Y-direction moving member  73 . The X-Y stage  71  is supported on a crossbar structure formed of the X-direction moving member  72  and Y-direction moving member  73  which do not restrict the operations of each other, and can move in both the X and Y directions. In the coordinate system, the two orthogonal horizontal axes form X- and Y-axes, the vertical axis forms the Z-axis, and rotational directions about the X-, Y-, and Z-axes form θx, θy, and θz axes, respectively.  
      The stage device  71  includes X-direction counter masses  74   a  and  74   b  serving as load masses supported by a structure movable in the X direction, and Y-direction counter masses  75   a  and  75   b  serving as load masses supported by a structure movable in the Y direction.  
      An X-direction linear motor applies a thrust between the X-direction moving member  72  and X-direction counter masses  74   a  and  74   b . In this case, the X-direction moving member  72  serves as a movable element, and the X-direction counter masses  74   a  and  74   b  serve as stators. Similarly, a Y-direction linear motor applies a thrust between the Y-direction moving member  73  and Y-direction counter masses  75   a  and  75   b . In this case, the Y-direction moving member  73  serves as a movable element, and the Y-direction counter masses  75   a  and  75   b  serve as stators. The X-direction moving member  72  and Y-direction moving member  73  are driven by these linear motors to drive the stage device  71  in the X and Y directions.  
      In this stage system, when the stage device  71  is driven by the linear motor through the X-direction moving member  72  and Y-direction moving member  73 , its driving reaction force acts on the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  to operate in the same directions in which the driving reaction force of the stage device  71  acts. The stator of the linear motor which drives the stage device  71  is supported on a base  3  where the stage device  71  is mounted through a movable structure. Even when the linear motor is driven to operate the stage, the energy and momentum of the stage driving reaction force form the kinetic energy and momentum of the counter masses including the linear motor stators and load masses. In an ideal state, the force is not transmitted to the base  3 , and the stage can be operated without largely vibrating the base  3  where the stage system including these constituent elements is mounted.  
      In the semiconductor exposure apparatus according to this embodiment, sensors are employed for the stage device  71  having the above structure and the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  to detect their motion physical values.  
      More specifically, the stage device  71  includes a position sensors  81   a  ( 81   a T and  81   a H) and  81   b  ( 81   b T and  81   b H) which detect and output the position information of the stage device  71  in the respective directions of the degrees of freedom, i.e., in the X and Y directions, velocity sensors  82   a  and  82   b  which detect and output the velocity information of the stage device  71  in the respective directions of the degrees of freedom, i.e., in the X and Y directions, and acceleration sensors  83   a  and  83   b  which detect and output the acceleration information of the stage device  71  in the respective directions of the degrees of freedom, i.e., the X and Y directions.  
      The X-direction counter masses  74   a  and  74   b  respectively include position sensors  84   a  and  84   b  which detect and output the position information of the corresponding counter masses, velocity sensors  85   a  and  85   b  which detect and output the velocity information of the corresponding counter masses, and acceleration sensors  86   a  and  86   b  which detect and output the acceleration information of the corresponding counter masses.  
      Similarly, the Y-direction counter masses  75   a  and  75   b  respectively include position sensors  87   a  and  87   b  which detect and output the position information of the corresponding counter masses, velocity sensors  88   a  and  88   b  which detect and output the velocity information of the corresponding counter masses, and acceleration sensors  89   a  and  89   b  which detect and output the acceleration information of the corresponding counter masses.  
      The position sensors  84   a  and  84   b , and  87   a  and  87   b , velocity sensors  85   a  and  85   b , and  88   a  and  88   b , and acceleration sensors  86   a  and  86   b , and  89   a  and  89   b  respectively detect the motion physical values, i.e., the position information, velocity information, and acceleration information in the operating directions of the X-direction counter masses  74   a  and  74  and Y-direction counter masses  75   a  and  75   b.    
      As the position sensor  81  ( 81   a  and  81   b ) which detects and outputs the position information of the stage device  71 , a laser interferometer which is widely used in this field because of the requirements in accuracy or the like is preferably used.  
      As the velocity sensor  82  ( 82   a  and  82   b ) which detects and outputs the velocity information of the stage device  71 , a geophone sensor or another type of velocity sensor can be used. As the acceleration sensor  83  ( 83   a  and  83   b ) which detects and outputs the acceleration information of the stage device  71 , various types of servo or piezoelectric accelerometers can be used.  
      When a laser interferometer is used as the position sensor  81 , in place of using the velocity sensor  82  and acceleration sensor  83 , the motion physical values of the output signals of the laser interferometer may be converted appropriately to calculate the velocity and acceleration.  
      Similarly, as the position sensors  84   a  and  84   b , and  87   a  and  87   b  which detect and output the position information of the respective X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b , various types of position sensors such as laser interferometers or encoders can be used.  
      As the velocity sensors  85   a  and  85   b , and  88   a  and  88   b  which detect and output the velocity information of the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b , geophone sensors or another type of velocity sensors can be used. As the acceleration sensors  86   a  and  86   b , and  89   a  and  89   b  which detect and output the acceleration information of the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b , various types of servo or piezoelectric accelerometers can be used.  
      When laser interferometers are used as the position sensors  84   a ,  84   b ,  87   a , and  87   b , in place of using the velocity sensors  85   a ,  85   b ,  88   a , and  88   b  and acceleration sensors  86   a ,  86   b ,  89   a , and  89   b , the motion physical values of the output signals from the laser interferometers may be converted appropriately to calculate the velocities and accelerations.  
      In employing a control scheme to be described later, assume that the apparatus operates without any problem when at least one of the sensors is omitted. In this case, at least one of the position sensors  81   a ,  81   b ,  84   a ,  84   b ,  87   a , and  87   b , at least one of the velocity sensors  82   a ,  82   b ,  85   a ,  85   b ,  88   a , and  88   b , and at least one of the acceleration sensors  83   a ,  83   b ,  86   a ,  86   b ,  89   a , and  89   b  may be omitted.  
      The stage system which includes the stage device  71 , X-direction counter masses  74   a  and  74   b , and Y-direction counter masses  75   a  and  75   b  described above is mounted on the base  3 . The base  3  is supported on a foundation structure  4  set on an apparatus installation foundation by anti-vibration supports  5  in an anti-vibration manner. The base  3  includes actuators  21  ( 21   a  to  21   h ) which apply a control force to the base  3 . The thrusts generated by the actuators  21  ( 21   a  to  21   h ) are controlled on the basis of signals obtained by a compensator  6   b.    
      Output signals from the position sensors  81   a  and  81   b , velocity sensors  82   a  and  82   b , acceleration sensors  83   a  and  83   b , position sensors  84   a ,  84   b ,  87   a , and  87   b , velocity sensors  85   a ,  85   b ,  88   a , and  88   b , and acceleration sensors  86   a ,  86   b ,  89   a , and  89   b  are input to the compensator  6   b  and compensated, as shown in  FIG. 6 . The actuators  21  ( 21   a  to  21   h ) are driven through a driving circuit  20  on the basis of the operation results obtained by the compensator  6   b.    
      In FIGS.  4  to  6 , the actuators  21  include the eight actuators  21   a  to  21   h . The number of actuators  21  is not limited to eight as far as it is sufficient to realize a required control performance.  
      As shown in  FIGS. 4 and 5 , the actuators  21  ( 21   a  to  21   h ) which apply the control force to the base  3  include actuators ( 21   a  to  21   d ) which apply a control force to the base  3  in the vertical direction and actuators ( 21   e  to  21   h ) which apply a control force to the base  3  in the horizontal direction. Because of the control arrangement to be described later, if substantially no control force need be applied, at least one of the actuators can be omitted. As the actuators  21  which apply the control force to the base  3 , electromagnetic driving linear motors or the like can be suitably used.  
      As the anti-vibration supports  5 , those which are identical to those described in the first embodiment can be used. Naturally, active vibration-damping devices having the same structure as that described in detail in the first embodiment can also be used as the anti-vibration supports  5 . In a precision device such as an exposure apparatus, the necessity of accurately controlling the position and vibration of the base  3  where the devices are mounted is high. Accordingly, as the anti-vibration supports  5 , it is desirable to employ active vibration-damping devices.  
      The semiconductor exposure apparatus according to this embodiment includes the constituent elements described above. The operation of the semiconductor exposure apparatus according to this embodiment will be described in detail.  
      In the semiconductor exposure apparatus according to this embodiment, when the stage device  71  and X-direction moving member  72  operate in the direction (X direction) of the arrow a shown in  FIG. 4  on the basis of a drive command signal from the controller of the exposure apparatus, the X-direction counter masses  74   a  and  74   b  operate in the directions of arrows Aa and Ab shown in  FIG. 4 , i.e., in the direction of the same degree of freedom as that of the stage device  71  but in the opposite direction. When the stage device  71  and Y-direction moving member  73  operate in the direction (Y direction) of the arrow b shown in  FIG. 4  on the basis of a drive command signal from the controller of the exposure apparatus, the Y-direction counter masses  75   a  and  75   b  operate in the directions of arrows Ba and Bb shown in  FIG. 4 , i.e., in the direction of the same degree of freedom as that of the stage device  71  but in the opposite direction. This operation takes place when a thrust generated between the movable elements of the stage driving linear motors attached to the X-direction moving member  72  and Y-direction moving member  73  and the stators of the stage driving linear motors attached to the X- and Y-direction counter masses  74   a  and  74   b  and  75   a  and  75   b  is exerted on the stage device  71 , X-direction moving member  72 , and Y-direction moving member  73 , and the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  which are supported movably.  
      In the stage system having this structure, the reaction force of the driving force which is generated when the stage device  71  is driven is transmitted not to the base  3  where the stage system is mounted but to the X- and Y-direction counter masses. Thus, the energy of the driving reaction force is converted into the kinetic energies and momenta of not the base  3  but of the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b . The force acting on the base  3  can be greatly reduced as compared with the conventional stage device in which the stator of the stage driving linear motor is fixed to the base. As a result, the vibration of the base  3  can be suppressed small.  
      Ideally, the stage device  71  having the above structure desirably operates such that the kinetic energies and momenta of the stage device  71 , X-direction moving member  72 , and Y-direction moving member  73  are entirely transmitted to the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  while a force and moment caused by stage driving are not transmitted to the base  3  at all. Then, no disturbance acts on the base  3 , and no vibration is caused by disturbance.  
      Assume that the kinetic energies, momenta, driving reaction forces, and the like of the stage device  71 , X-direction moving member  72 , and Y-direction moving member  73  are not entirely transmitted to the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  due to the friction force and damping force generated in the bearings (not shown) and influences and the like which are generated when the wiring lines and pipes extending from the base  3  to the stage device  71 , X-direction moving member  72 , Y-direction moving member  73 , and X- and Y-direction counter masses serve as springs. In this case, the kinetic energies and momenta of the stage device  71 , X-direction moving member  72 , and Y-direction moving member  73  do not balance with the kinetic energies and momenta of the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b . The difference in kinetic energy and momentum is transmitted to the base  3  where both the stage device  71  are mounted. Consequently, vibration occurs in the base  3 .  
      In the semiconductor exposure apparatus according to this embodiment, the kinetic energy, momentum, and driving reaction force that cannot be completely canceled between the stage device  71  and the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  are estimated from the motion physical values such as position information (displacement), velocity information, and acceleration information of the stage device and counter masses. The actuators which apply the control force to the base  3  are controlled on the basis of the estimated signals to decrease the vibration of the base  3 .  
      The practical control operation of the semiconductor exposure apparatus according to this embodiment will be described. First, a device which performs the control operation by estimating the thrust, momentum, and the like transmitted to the base  3  on the basis of the acceleration signals of the stage device  71  and counter masses  74   a ,  74   b ,  75   a , and  75   b , and a control method for the device will be described.  
      The stage device  71  is driven by the drive command signal in accordance with a predetermined driving pattern. The X-direction counter masses  74   a  and  74   b  and the Y-direction counter masses  75   a  and  75   b  are operated by the X- and Y-direction driving reaction forces, respectively, of the stage device  71  in a direction opposite to the driving direction of the stage device  71 . At this time, the X-direction acceleration information and Y-direction acceleration information of the stage device  71 , the pieces of the X-direction acceleration information of the X-direction counter masses  74   a  and  74   b , and the pieces of the Y-direction acceleration information of the Y-direction counter masses  75   a  and  75   b  are detected by the acceleration sensors  83   a ,  83   b ,  86   a ,  86   b ,  89   a , and  89   b . The output signals from the acceleration sensors are input to the compensator  6   b.    
      The compensator  6   b  estimates the driving reaction force of the stage device  71  which cannot be canceled by the operations of the X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b.    
      In the case of a stage device which is driven in the directions of two degrees of freedom as described herein, the driving reaction force acts in the stage driving directions with two translational degrees of freedom and directions of three rotational degrees of freedom about axes perpendicular to the stage driving direction. Accordingly, the relationship between the thrust and momentum of the stage device and those of the counter masses can be formulated concerning the kinetic directions of the five degrees of freedom.  
      Regarding the thrust and momentum components of the stage device and counter masses which are proportional to the accelerations, the following equation of motion is established:  
               [         fx           fy           Mqx           Mqy           Mqz         ]     =             [         mx       0       M1       M2       0       0           0       my       0       0       M3       M4           0         m   ×   1   ⁢   z0         0       0         M3   ×   1   ⁢   z3           M4   ×   1   ⁢   z4               m   ×   1   ⁢   z0         0         M1   ×   1   ⁢   z1           M1   ×   1   ⁢   z2         0       0             m   ×   1   ⁢   y0           m   ×   1   ⁢   x0           M1   ×   1   ⁢   y1           M2   ×   1   ⁢   y2           M3   ×   1   ⁢   x3           M4   ×   1   ⁢   x4           ]     ⁢           [         ax           ay           aX1           aX2           aY1           aY2         ]                   (   3   )             
 
 where mx is the sum of the masses of the stage device  71  and X-direction moving member  72 , my is the sum of the masses of the stage device  71  and Y-direction moving member  73 , M 1 , M 2 , M 3 , and M 4  are the masses of the X-direction counter mass  74   a , X-direction counter mass  74   b , Y-direction counter mass  75   a , and Y-direction counter mass  75   b , respectively, ax and ay are the X- and Y-direction accelerations, respectively, of the stage device  71 , aX1 and aX2 are the X-direction accelerations of the X-direction counter masses  74   a  and  74   b , respectively, aY1 and aY2 are the Y-direction accelerations of the Y-direction counter masses  75   a  and  75   b , respectively, lz0 to lz4 are the Z-coordinates of the positions of centers of gravity of the stage device  71  and X- and Y-direction counter masses  74   a  and  74   b , and  75   a  and  75   b , respectively, with reference to the position of center of gravity of the base  3  as the origin point, ly0 to ly2 are the Y-coordinates of the positions of centers of gravity of the stage device  71  and X-direction counter masses  74   a  and  74   b  with reference to the position of center of gravity of the base  3  as the origin point, and lx0, lx3, and lx4 are the X-coordinates of the positions of centers of gravity of the stage device  71  and Y-direction counter masses  75   a  and  75   b  with reference to the position of center of gravity of the base  3  as the origin point. In this case, lz0 to lz4, ly0 to ly2, lx0, lx3, and lx4 can be obtained from the mechanical design information and the like of the stage device  71  and counter masses  74   a ,  74   b ,  75   a , and  75   b.  
 
      Thrusts and moments fx, fy, Mqx, Mqy, and Mqz in the left-hand side are left in the X, Y, θx, θy, and θz directions without being canceled by the operation of the stage device  71  and the operations of the X- and Y-direction counter masses  74   a  and  74   b , and  75   a  and  75   b . In other words, fx, fy, Mqx, Mqy, and Mqz are the differences in operation between the stage device and counter masses. If fx, fy, Mqx, Mqy, and Mqz are not zero, the thrusts and moments are not canceled between the stage device and counter masses but leak to another portion, i.e., the base  3 .  
      When the thrust corresponding to the left member of this equation is distributed among the actuators  21  ( 21   a  to  21   h ), even if the stage driving reaction forces are not canceled between the stage device and counter masses and leaking forces are input to the base  3 , the leaking forces can be canceled by the actuators  21  ( 21   a  to  21   h ) to decrease the vibration of the base  3 .  
      The compensator  6   b  estimates fx: fy, Mqx, Mqy, and Mqz in the left member in accordance with equation (3), and generates control command signals to control the actuators  21  ( 21   a  to  21   h ) which apply a control force to the base  3 , in order to cancel fx, fy, Mqx, Mqy, and Mqz. More specifically, the compensator  6   b  performs gain compensation and filtering to estimated fx, fy, Mqx, Mqy, and Mqz when necessary. When the actuators  21  are high-response actuators such as electromagnetic driving linear motors, the compensator  6   b  can perform control calculation of mainly gain compensation on the basis of the information on fx, fy, Mqx, Mqy, and Mqz which are estimated in accordance with equation (3), and distribute the obtained control command signal among the respective actuators. In this case, the thrust to be generated by the actuators  21  ( 21   a  to  21   h ) is given as thrusts and moments fx, fy, Mqx, Mqy, and Mqz in the X, Y, θx, θy, and θz directions. The compensator  6   b  calculates distributional thrusts to generate desired thrusts and moments introduced on the basis of equation (3) in the X, Y, θx, θy, and θz directions respectively, and to distribute the thrusts among the plurality of actuators  21  ( 21   a  to  21   h ). Thrust distribution equation can be formulated on the basis of the geometric arrangement of the actuators  21  ( 21   a  to  21   h ) and their arranging directions.  
      The plurality of actuators  21  ( 21   a  to  21   h ) are driven through the driving circuit  20  on the basis of the control command signals introduced by the compensator  6   b  in this manner, in order to apply a control force to the base. The thrusts and moments which are inevitably generated in accordance with equation (3) and cannot be completely canceled by the stage device  71  and X-direction counter masses  74   a  and  74   b  and Y-direction counter masses  75   a  and  75   b  but transmitted to the base  3  are canceled by the actuators  21  in a real-time manner. Consequently, the vibration of the base  3  can be suppressed small.  
      In an apparatus which includes the stage device  71 , X-direction counter masses  74   a  and  74   b , Y-direction counter masses  75   a  and  75   b , and the like and decreases the stage driving reaction force by their mutual operations, the stage driving reaction force can be canceled and decreased by the mutual operations of the constituent elements, thus decreasing the vibration of the base where the constituent elements are mounted. If, however, the mutual operations cannot completely cancel the stage driving reaction force and a thrust and moment are left to be transmitted to the base where the stage device  71  and counter masses  74   a ,  74   b ,  75   a , and  75   b  are mounted, the force acting on the base must be decreased by using some auxiliary means.  
      In the semiconductor exposure apparatus according to this embodiment, as described above, the thrust and moment which are not completely canceled by the operations of the stage device and X- and Y-direction counter masses but transmitted to the base are estimated on the basis of the signals from the sensors which detect the motion physical values, e.g., the acceleration information and the like, of the stage device and X- and Y-direction counter masses, and the actuators which apply the control force to the base are controlled on the basis of the estimated thrust and moment. Thus, a higher vibration control performance that cannot be obtained by the conventional apparatus can be obtained. Consequently, the vibration of the stage device and other precision devices mounted on the base is decreased to realize an improvement in performance of the devices to be mounted on the exposure apparatus or the like.  
      In the above description, for the sake of descriptive simplicity, the thrust to be transmitted to the base is only a term proportional to the acceleration. In fact, however, the relationship between a force and moment which cannot be expressed by only a term proportional to the acceleration are not sometimes negligible, e.g., friction in bearings to movably support the stage device and counter masses, resistance caused by a counter electromotive force generated between the movable portion and stationary portion of the linear motor which forms the stage device, or an influence generated when a wiring line or pipe acts as a spring among the stage device, counter masses, and base. In this case, the thrust and moment transmitted to the base  3  can be estimated by adding a term proportional to the velocity and a term proportional to the position. The thrust and moment transmitted to the base  3  can be estimated by the following equation (4). Regarding the term proportional to the velocity in the following equation, not only the velocities of the stage device and counter masses with respect to the base  3 , but also the relative velocity between the stage device and counter masses is considered. Equation (4) is given as an equation having five degrees of freedom, since the stage device as the target is a system having two degrees of freedom. The basic idea of equation (4) is the same as that of equation (2).  
               [         fx           fy           Mqx           Mqy           Mqz         ]     =             [         mx       0       M1       M2       0       0           0       m       0       0       M3       M4           0         m   ×   1   ⁢   z0         0       0         M3   ×   1   ⁢   z3           M4   ×   1   ⁢   z4               m   ×   1   ⁢   z0         0         M1   ×   1   ⁢   z1           M1   ×   1   ⁢   z2         0       0             m   ×   1   ⁢   y0           m   ×   1   ⁢   x0           M1   ×   1   ⁢   y1           M2   ×   1   ⁢   y2           M3   ×   1   ⁢   x3           M4   ×   1   ⁢   x4           ]     ⁢             [         ax           ay           aX1           aX2           aY1           aY2         ]     +       [         d11       d12       d13       d14       d15       d16           d21       d22       d23       d24       d25       d26           d31       d32       d33       d34       d35       d36           d41       d42       d43       d44       d45       d46           d51       d52       d53       d54       d55       d56         ]     ⁢             [         vx           vy           vX1           vX2           vY1           vY2         ]     +       [         k11       k12       k13       k14       k15       k16           k21       k22       k23       k24       k25       k26           k31       k32       k33       k34       k35       k36           k41       k42       k43       k44       k45       k46           k51       k52       k53       k54       k55       k56         ]     ⁡     [         px           py           pX1           pX2           pY1           pY2         ]                             (   4   )             
 
      In equation (4), the same symbols as in equation (3) represent the same parameters. Also, vx and vy are the X- and Y-direction velocities, respectively, of the stage device  71 , vX1 and vX2 are the X-direction velocities of the counter masses  74   a  and  74   b , respectively, vY1 and vY2 are the Y-direction velocities of the counter mass  75   a  and  75   b , respectively, px and py are the X- and Y-direction positions (displacements), respectively, of the stage device  71 , pX1 and pX2 are the X-direction displacements of the counter masses  74   a  and  74   b , respectively, pY1 and pY2 are the Y-direction displacements of the counter masses  75   a  and  75   b , respectively, and dij and kij (i=1, 2, . . . , 5, j=1, 2, . . . , 6) are a term proportional to the velocity (velocity proportional gain) and a term proportional to the position (displacement proportional gain), respectively.  
      The structure for controlling the actuators on the basis of the thrusts and moments estimated by the above equation (4) to decrease and suppress the vibration of the base is the same as that described above, and a description thereof will be omitted.  
      When the term proportional to the velocity and the term proportional to the position are considered in this manner, the thrust and moment to be transmitted from the stage system to the base can be estimated more accurately, and the vibration of the base  3  can be suppressed and decreased more effectively.  
      In actual control operation, not all the motion physical values of the position information (displacement), velocity information, and acceleration information of the stage device and counter masses need be used for control. As far as a sufficient effect can be obtained, a control operation may be performed in which only a term proportional to the acceleration is considered as in equation (3). In this case, sensors which detect motion physical values that need not be used may be omitted. Such control operation may be performed not for all of the X, Y, θx, θy, and θz directions but for at least one of them when necessary.  
      In the same manner as in the first embodiment, sensors which detect the relative velocity of the stage device and counter masses may be provided, and the control may be performed by performing the above control operation by using relative velocity signals of the stage device and counter masses which are detected by the sensors. This is apparent from equation (4).  
      Means for obtaining the position information (displacement), velocity information, and acceleration information of the stage device and counter masses are not limited to sensors which detect their motion physical values. For example, the position information (displacement), velocity information, and acceleration information can naturally be obtained on the basis of the drive profile information on the stage device and counter masses.  
     Third Embodiment  
      The first and second embodiments exemplify an apparatus and structure for controlling the actuators which apply a control force to the base on the basis of the motion physical values, e.g., the position information (displacement), velocity information, and acceleration information of the stage device and counter masses. Equations (1) to (4) will be reviewed. For the sake of simplicity, equation (1) will be discussed.  
      According to the basic operation of a stage device, e.g., the stage device described in the present invention which includes counter masses, the motion physical values, e.g., position (displacement), velocity, and acceleration are transferred between the stage device and counter masses. Forces from the stage device and counter masses do not act on the base or the like where the stage device and counter masses are mounted. Considering this point, in an ideal state, for example, if the relationship of equation (5) is maintained, fy and Mqz in the left member of equation (1) become zero: 
 
 m×ay+M   1 × aY   1 + M   2 × aY   2 =0 
 
aY 1 =aY 2  
 
lx0=0 
 
 lx 1 =−x 2   (5) 
 
      In this case, for example, if the sign of lz0 and that of lz1 and lz2 are different, Mqx cannot become zero in any way. Then, the actuators are controlled on the basis of Mqx introduced in accordance with equation (1).  
      Regarding Mqx, as far as the relationship of equation (5) is almost satisfied, if the acceleration signal ay of the stage device can be observed, a necessary control force Mqx can be determined on the basis of only ay, so that an almost good vibration control performance can be obtained.  
      More specifically, depending on the mechanical design state of the stage device and counter masses and their control method, the compensator  6  can substantially estimate the acceleration information of the counter masses from the acceleration information of the stage device. When mechanical design information is added to the estimated acceleration information, the same control operation as that of the first embodiment can be realized by substantially using only the acceleration information of the stage device. The control method having this arrangement is also included in the scope of the present invention.  
      As the acceleration information of the stage device, an acceleration profile which defines the stage operation can be used. For the sake of descriptive simplicity, the present invention is directed to a control structure based on the calculation shown in equation (1). Note that the same control operation can be performed by equation (3) of the second embodiment.  
     Fourth Embodiment  
      In the structures described in the first to third embodiments, the behaviors of the stage device and counter masses in the horizontal direction are noted. In the apparatus of the present invention, variations in positions of centers of gravity of the loads, including the stage device and counter masses, on a base when the stage device and counter masses operate on the base which is supported in an anti-vibration manner, must also be noted.  
      In a stage using counter masses, as far as the kinetic energy and momentum are appropriately transferred between the stage device and counter masses, even when these loads shift, all of the positions of centers of gravity of the moving loads can be set substantially immobile. If, however, the kinetic energy and momentum cannot be completely canceled between the stage device and counter masses because of the reasons described in the first and second embodiments, the position of center of gravity of the moving loads as a whole sometimes fluctuates. If the position of center of gravity of the loads, including the stage device and counter masses, on the base fluctuates in this manner, this fluctuation spoils the moment balance of the base support system, thus inclining the base.  
      Even in this case, if motion physical value sensors of the stage device and counter masses are provided as in the apparatus of the present invention, fluctuations in center of gravity of the load on the base can be obtained in real time. In other words, the position of center of gravity of the load on the base can be estimated from the detection signals of the position information of the stage device and counter masses. When the actuators which apply a control force to the base are controlled in accordance with the fluctuation amount of the position of center of gravity, an inclination of base which is caused by the shift of the center of gravity of the loads on the base can be minimized.  
      A semiconductor exposure apparatus according to the fourth embodiment includes a compensator for operating actuators which apply a control force to a base on the basis of the detection signal of the motion physical value of at least one of the position information, velocity information, and acceleration information of the stage device, and the detection signal of the motion physical value of at least one of the position information, velocity information, and acceleration information of the counter masses. If this compensator also performs a control operation based on the shift of the center of gravity of the loads as described above, the vibration of the base can be minimized. More specifically, for example, when high-response electromagnetic driving linear motors are used as actuators, control operation may be performed on the basis of the position information of the stage device and counter masses. When low-response pneumatic driving actuators are used, control operation may be performed on the basis of velocity information which corresponds to the derivative information of the positions of the stage device and counter masses by considering the response speed of the actuators which substantially shows integral characteristics or primary delay characteristics in a necessary control band.  
      As described above, in the apparatus which includes the stage device and counter masses and cancels and decreases the stage driving reaction force by the mutual operations of the stage device and counter masses, a force which acts on the base where the stage device and counter masses are mounted can be decreased greatly. Even when the stage driving reaction force is large, the vibration of the base can be decreased effectively. When, however, the stage driving reaction force cannot be completely canceled by the mutual operations of the stage device and counter masses and a thrust and moment are transmitted to the base where the stage device and counter masses are mounted, the force acting on the base must be decreased by using some auxiliary unit.  
      With the semiconductor exposure apparatus according to this embodiment, as described above, a thrust and moment which are not completely canceled by the mutual operations of the stage device and counter masses but transmitted to the base are estimated on the basis of signals from means which measures the motion physical values such as the position information (displacement), velocity information, and acceleration information of the stage device and counter masses. The actuators which apply a control force to the base are controlled on the basis of the estimated thrust and moment. Thus, even when the stage driving reaction force cannot be completely canceled by the mutual operations of the stage device and counter masses, the thrust and moment which are transmitted to the base where the stage device and counter masses are mounted can be canceled. A higher vibration control performance that cannot be obtained with the conventional apparatus can be obtained. Consequently, the vibration of the stage device and other precision devices which are mounted on the base can be decreased to realize an improvement in performance of devices mounted on the exposure apparatus or the like.  
      [Application] 
      A semiconductor device manufacturing process which uses an exposure apparatus according to a preferred embodiment of the present invention will be described.  FIG. 10  is a flowchart showing the flow of the entire semiconductor 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 by the exposure apparatus described above in accordance with lithography using the mask and wafer described above. In the next step  5  (assembly) called a post-process, a semiconductor chip is formed using 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 in step  7 .  
      The wafer process of step  4  has the following steps, i.e., an oxidation step of oxidizing the surface of the wafer, a CVD step of forming an insulation film on the wafer surface, an electrode formation step of forming an electrode on the wafer by deposition, an ion implantation step of implanting ions in the wafer, a resist process step of applying a photosensitive agent to the wafer, an exposure step of transferring the circuit pattern to the wafer after the resist process step by the exposure apparatus described above, a developing step of developing the wafer exposed in the exposure step, an etching step of removing portions other than the resist image developed in the developing step, and a resist removal step of removing any unnecessary resist after etching. These steps are repeated to form multiple circuit patterns on the wafer.  
      As many apparently 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  
      This application claims priority from Japanese Patent Application No. 2004-211961 filed on Jul. 20, 2004, which is hereby incorporated by reference herein.