JP2006070928A - Control method and exposure method for vibration control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for a vibration control device capable of stably supporting a structure even if resetting for restarting is performed after the control of the vibration control device is temporarily stopped. <P>SOLUTION: A vibration control table 35 comprises an air damper 45 in which air is supplied to support a first column 36 as the structure through a movable member 47 and a voice coil motor 50 generating a thrust by a supplied current to support the first column 36. When the first column 36 is supported again after the air in the air damper 45 is temporarily bled, the first column 36 is positioned at a target position by supplying air to the air damper 45 while imparting rigidity to the air damper 45 by generating the thrust from the voice coil motor 50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for controlling a vibration isolator used to suppress vibration of a supporting structure, and a predetermined pattern on a substrate by a system that is anti-vibrated by a vibration isolator controlled using the method. The present invention relates to an exposure method.

  Formed on a reticle (or photomask, etc.) as a mask in a lithography process, which is one of the manufacturing processes of devices such as semiconductor elements, liquid crystal display elements, imaging devices (CCD (Charge Coupled Device), etc.), thin film magnetic heads, etc. An exposure apparatus is used to transfer and expose the formed pattern onto a wafer (or a glass plate or the like) coated with a photoresist as a substrate. As the exposure apparatus, a batch exposure type (stationary exposure type) projection exposure apparatus such as a stepper or a scanning exposure type projection exposure apparatus (scanning type exposure apparatus) such as a scanning stepper is used.

  In the above exposure apparatus, in order to improve exposure accuracy such as positioning accuracy and overlay accuracy between the reticle stage holding the reticle and the wafer stage holding the wafer, it is necessary to eliminate the influence of vibration as much as possible. However, when each of the above stages moves, the reaction force during acceleration may be transmitted to the floor and the floor may vibrate. Further, since the floor vibrates due to various forces even when the related equipment in the device manufacturing factory where the exposure apparatus is installed operates, the floor constantly vibrates to some extent. Therefore, in order to prevent the vibration of the floor from being transmitted to the exposure apparatus and lowering the exposure accuracy, a vibration isolator has been conventionally provided between the exposure apparatus and the floor (installation surface).

As a conventional vibration isolator, a mechanism that supports a stage or the like with an air damper to which air is supplied so that the internal pressure is maintained substantially constant is widely used. In addition, an opportunity to use an active vibration isolator that combines this air damper and an electromagnetic actuator (electromagnetic damper) that suppresses vibration detected by an acceleration sensor arranged on a stage or the like is increasing. Furthermore, in order to improve the anti-vibration performance, the number of types of sensors that feed back information to the above-mentioned electromagnetic actuator is increased, and the pressure of the air damper is controlled using the detection result of the motion sensor provided on the stage. An active vibration isolator has also been proposed. For details of the vibration isolator, see, for example, Patent Document 1 below.
JP 2002-175122 A

  By the way, in recent years, patterns of various devices (particularly, semiconductor elements) described above are further miniaturized, and accordingly, necessary exposure accuracy is also increased. Thereby, in the exposure apparatus, it is necessary to suppress the influence of vibration more than ever. When the rigidity of the vibration isolator is increased, the vibration of the floor is easily transmitted to the exposure apparatus. Therefore, the rigidity of the vibration isolator tends to be lowered from the viewpoint of effectively suppressing the influence of the vibration.

  Even if the vibration isolator is low in rigidity, if the vibration isolator is in a steady state in which the exposure apparatus is supported at a predetermined height position, the exposure apparatus is stably supported by the vibration isolator and the vibration of the floor Is effectively suppressed by the vibration isolator. However, when the exposure apparatus is started up, a reset process for starting the control of the image stabilizing apparatus to float the exposure apparatus and support it at a predetermined height position is performed. Further, at the time of regular or irregular maintenance, the control of the image stabilizer is temporarily stopped and then the image stabilizer is started again, and the exposure apparatus is floated and reset processing for supporting the image sensor at a predetermined height position is performed. During the above reset process, the vibration isolator has low rigidity, so that there is a problem that the exposure apparatus supported by the vibration isolator falls down or shakes and becomes unstable. Since the exposure apparatus is equipped with various measuring devices that require nano-order accuracy and a projection optical system that requires high imaging performance, the exposure device is placed in an unstable state from the viewpoint of maintaining the device performance. It is necessary to prevent as much as possible.

  The present invention has been made in view of the above circumstances, and uses a method for controlling a vibration isolator capable of stably supporting a structure even when resetting the vibration isolator, and the method. An object of the present invention is to provide an exposure method for exposing a predetermined pattern on a substrate by a system which is controlled by a vibration isolation device controlled in this manner.

The present invention adopts the following configuration corresponding to each diagram shown in the embodiment. However, the reference numerals with parentheses attached to each element are merely examples of the element and do not limit each element.
In order to solve the above-described problems, a method for controlling a vibration isolator according to the present invention is provided with a vibration isolator (29, 35, 40) that includes a gas damper (45) that is supplied with gas and supports a structure (36). 51, 52), wherein the gas is supplied to the inside of the gas damper, and the structure is provided while providing rigidity to the gas damper in a support direction (Z direction) for supporting the structure. It is characterized by positioning at a target position.
According to this invention, the structure is supported by the gas damper having rigidity in the support direction and positioned at the target position.
Here, the rigidity is given to the target position until the structure exceeds the target position, and the rigidity is returned to the target position when the structure exceeds the target position. Is desirable.
Moreover, it is desirable to provide the rigidity according to a difference between the position of the structure and the target position.
Furthermore, it is preferable that the added rigidity is removed after the structure is positioned at the target position.
The exposure method of the present invention is an exposure method in which a pattern is exposed on a substrate (W) by a system that is anti-vibrated by an anti-vibration device (29, 35, 40, 51, 52). The control method of the vibration isolator is used.
According to the present invention, at the time of the reset process, the structure is supported by the gas damper having rigidity in the support direction and positioned at the target position. Further, after the structure is positioned at the target position, the applied rigidity is removed and the structure is supported by the gas damper.
In addition, in order to explain the present invention in an easy-to-understand manner, the description has been made in association with the reference numerals of the drawings representing one embodiment, but it goes without saying that the present invention is not limited to the embodiment.

According to the present invention, since the reset process is performed by giving rigidity to the gas damper, the structure can be stably supported even when the reset process is performed. For this reason, even if the gas damper has rigidity close to 0 or negative rigidity, the structure can be stably supported at the time of resetting.
Further, after the structure is positioned at the target position, the imparted rigidity is removed and the structure is supported by the low-rigidity gas damper, so that the vibration isolation performance can be improved.

  Hereinafter, a control method and an exposure method of an image stabilizer according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of functional units constituting an exposure apparatus in which a vibration isolator control method and an exposure method according to an embodiment of the present invention are used. The exposure apparatus EX shown in FIG. 1 moves the pattern formed on the reticle R to the wafer W while moving the reticle R as a mask and the wafer W as a substrate relative to the projection optical system PL in FIG. Is a step-and-scan type scanning exposure type exposure apparatus that sequentially transfers to the substrate. In FIG. 1, the illustration of the chamber that houses the exposure apparatus EX is omitted.

  In the following description, if necessary, an XYZ orthogonal coordinate system is set in the drawing, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system shown in FIG. 1 is set such that the X axis and the Y axis are included in a plane parallel to the moving surface of the wafer W, and the Z axis is set in a direction along the optical axis AX of the projection optical system PL. Yes. In this embodiment, the direction (scanning direction) in which the reticle R and the wafer W are moved synchronously is set to the Y direction.

The exposure apparatus EX shown in FIG. 1 includes a laser light source 1 made of a KrF excimer laser (wavelength 248 nm) or an ArF excimer laser (wavelength 193 nm) as a light source for exposure. As the laser light source 1, in addition to the above excimer laser, an ultraviolet laser light source such as an F ₂ laser light source (wavelength 157 nm), a Kr ₂ laser light source (wavelength 146 nm), an Ar ₂ laser light source (wavelength 126 nm), or a harmonic of a YAG laser. A wave generation light source, a harmonic generation device of a solid-state laser (semiconductor laser or the like), a mercury lamp (i-line or the like), or the like can also be used.

  Illumination light (exposure light) IL for exposure as an exposure beam from the laser light source 1 is a homogenizing optical system 2 composed of a lens system and a fly-eye lens system, a beam splitter 3, and variable dimming for light amount adjustment. The reticle blind mechanism 7 is irradiated with a uniform illuminance distribution through the device 4, the mirror 5, and the relay lens system 6. Illumination light IL limited in a slit shape or rectangular shape by the reticle blind 7 is irradiated onto the reticle R as a mask through the imaging lens system 8, and an image of the opening of the reticle blind 7 is formed on the reticle R. Imaged. An illumination optical system ILS is configured including the homogenizing optical system 2, the beam splitter 3, the variable dimmer 4 for adjusting the light amount, the mirror 5, the relay lens system 6, the reticle blind mechanism 7, and the imaging lens system 8. Yes.

  Of the circuit pattern region formed on the reticle R, the image of the portion irradiated by the illumination light IL is a wafer coated with a photoresist as a substrate via a projection optical system PL having a telecentric projection on both sides and a projection magnification of β. An image is projected onto W. As an example, the projection magnification β of the projection optical system PL is 1/4 or 1/5, the image-side numerical aperture NA is 0.7, and the field diameter is about 27 to 30 mm. Although the projection optical system PL is a refractive system, a catadioptric system or the like can also be used. Reticle R and wafer W can also be regarded as a first object and a second object, respectively. Note that the illumination area on the reticle R irradiated with the illumination light IL has an elongated shape in the direction along the X axis, which is the non-scanning direction.

  The reticle R arranged on the object plane side of the projection optical system PL is held on a reticle stage RST as a mask stage that moves at a constant speed in at least the Y direction via an air bearing on a reticle base (not shown) during scanning exposure. Has been. The movement coordinate position of the reticle stage RST (X-direction and Y-direction positions and rotation angles around the Z-axis) is a moving mirror 9 fixed to the reticle stage RST and a laser interferometer disposed opposite thereto. Measurement is sequentially performed with the system 10, and the movement is performed by a drive system 11 including a linear motor and a fine actuator. The moving mirror 9 and the laser interferometer system 10 actually constitute a triaxial laser interferometer having at least one axis in the X direction and two axes in the Y direction. The measurement information of the laser interferometer system 10 is supplied to the stage control unit 16, and the stage control unit 16 controls the measurement information and the control information (input) from the main control system 20 comprising a computer that controls the overall operation of the exposure apparatus EX. The operation of the drive system 11 is controlled based on the information.

  Wafer W arranged on the image plane side of projection optical system PL is held on wafer stage WST as a substrate stage via a wafer holder (not shown), and wafer stage WST moves at a constant speed in at least the Y direction during scanning exposure. It is mounted on a wafer base (not shown) via an air bearing so that it can be moved stepwise in the X and Y directions. Further, the movement coordinate position (positions in the X and Y directions and the rotation angle around the Z axis) of wafer stage WST is fixed to reference mirror 12 fixed below projection optical system PL and wafer stage WST. The moving mirror 13 and a laser interferometer system 14 arranged opposite to the moving mirror 13 are sequentially measured, and the movement is performed by a drive system 15 including an actuator such as a linear motor and a voice coil motor (VCM). .

  The movable mirror 13 and the laser interferometer system 14 actually constitute a triaxial laser interferometer having at least one axis in the X direction and two axes in the Y direction. The laser interferometer system 14 actually further includes a biaxial laser interferometer for measuring rotation angles around the X axis and the Y axis. Measurement information of the laser interferometer system 14 is supplied to the stage control unit 16, and the stage control unit 16 controls the operation of the drive system 15 based on the measurement information and control information (input information) from the main control system 20.

  Wafer stage WST is also provided with a Z leveling mechanism that controls the position (focus position) of wafer W in the Z direction and the tilt angles around the X and Y axes. Then, on the lower side surface of the projection optical system PL, the projection optical system 17a that projects the slit image onto a plurality of measurement points on the surface of the wafer W, and the reflected light from the surface is received to re-image the slit image. An oblique incidence type multi-point autofocus sensor (17 a, 17 b) composed of a light receiving optical system 17 b that detects the amount of lateral displacement of the image and supplies it to the stage control unit 16 is arranged. The stage control unit 16 calculates defocus amounts from the image plane of the projection optical system PL at the plurality of measurement points using information on the amount of misalignment of the slit image, and these defocus amounts are predetermined during scanning exposure. The Z leveling mechanism in the wafer stage WST is driven by the autofocus method so as to be within the control accuracy. The detailed configuration of the oblique incidence type multi-point autofocus sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-253603.

  The stage control unit 16 optimizes the drive system 15 based on the measurement information from the reticle interferometer system 14 and the reticle side control circuit that optimally controls the drive system 11 based on the measurement information from the laser interferometer system 10. When the reticle R and the wafer W are synchronously scanned during scanning exposure, both control circuits cooperatively control the drive systems 11 and 15. The main control system 20 exchanges commands and parameters with each control circuit in the stage control unit 16 and executes an optimum exposure process according to a program designated by the operator. For this purpose, an operation panel unit (not shown) (including an input device and a display device) that provides an interface between the operator and the main control system 20 is provided.

  Further, when the laser light source 1 is an excimer laser light source, a laser control unit 18 under the control of the main control system 20 is provided. The laser control unit 18 controls the pulse oscillation mode (one-pulse mode, burst mode, standby mode, etc.) of the laser light source 1 and adjusts the average light quantity of the emitted pulsed laser light. Control the high voltage for discharge. The light quantity control unit 19 is variably reduced so as to obtain an appropriate exposure amount based on a signal from a photoelectric detector 21 (integrator sensor) that receives a part of the illumination light IL divided by the beam splitter 3. While controlling the optical device 4, the intensity (light quantity) information of the pulse illumination light is sent to the laser control unit 18 and the main control system 20.

  In order to transfer the pattern of the reticle R to each shot area on the wafer W, it is necessary to align the reticle R and the wafer W in advance before starting the exposure operation. Therefore, the exposure apparatus EX shown in FIG. 1 includes a reticle alignment system (RA system) 22 for setting the reticle R at a predetermined position, and an off-axis alignment system 23 for detecting a mark on the wafer W. ing.

  When an exposure operation is started in the exposure apparatus EX configured as described above, the alignment between the reticle R and the wafer W using the alignment systems 22 and 23 is first performed. Next, irradiation of the reticle R with the illumination light IL is started, and the reticle stage RST is projected in a state where an image of a part of the pattern of the reticle R is projected onto one shot area on the wafer W. And the wafer stage WST, the pattern image of the reticle R is transferred to the shot area by a scanning exposure operation in which the projection magnification β of the projection optical system PL is used as a speed ratio to move (synchronously scan) in the Y direction. Thereafter, the irradiation of the illumination light IL is stopped, and the step-and-scan method is performed by repeating the operation of moving the wafer W stepwise in the X and Y directions via the wafer stage WST and the above-described scanning exposure operation. Thus, the pattern image of the reticle R is transferred to all shot areas on the wafer W.

  Next, an example of the installation state of the exposure apparatus EX in a semiconductor device manufacturing factory will be described. FIG. 2 is a partially cutaway view showing a state where the exposure apparatus EX is installed on the floor. In FIG. 2, a thick flat plate pedestal 32 is installed on the floor FL of the manufacturing plant as a base member when installing the exposure apparatus EX via a plurality of (for example, four or more) columns 31 made of H-shaped steel. A rectangular thin flat base plate 33 for installing the exposure apparatus EX is fixed on the pedestal 32.

  A first column 36 (structure) is placed on the base plate 33 via three or four active vibration isolation tables 35, and the projection optical system PL is held in the central opening of the first column 36. ing. As will be described in detail later, the vibration isolator 35 includes an air damper (a gas damper) and an electromagnetic damper including a voice coil motor and the like, and includes a set of acceleration sensors 40 and a set of sensors installed in the first column 36. By controlling the pressure in the air damper and the thrust of the electromagnetic damper based on detection information with a position sensor (not shown), vibration isolation of the first column 36 (and the member supported thereby) is actively performed. Done. In this case, vibration isolation in a relatively low frequency range is performed by the air damper, and vibration isolation in a relatively high frequency range is performed by the electromagnetic damper. Further, the anti-vibration table 35 is of low rigidity so as to improve the vibration isolation performance. The details of the structure in which the vibration isolator 35 has low rigidity will be described later.

  As the acceleration sensor 40, a piezoelectric acceleration sensor that detects a voltage generated in a piezoelectric element (piezo element or the like), a semiconductor type that utilizes the fact that the logical threshold voltage of a CMOS converter changes according to the magnitude of strain. Acceleration sensors or the like can be used. Moreover, as said position sensor (or displacement sensor), an eddy current displacement sensor can be used, for example. In this eddy current displacement sensor, for example, an alternating current is applied to a coil wound around an insulator, and the coil is brought close to a measurement object made of a conductor. An eddy current is generated in the conductor by an alternating magnetic field created by the coil. Take advantage of what you do. That is, the magnetic field due to the eddy current is in the opposite direction to the magnetic field due to the current of the coil, and the intensity and phase of the current flowing through the coil changes as these two magnetic fields overlap. Since this change becomes larger as the measurement object is closer to the coil, the position or displacement of the measurement object can be detected in a non-contact manner by detecting a signal corresponding to the current flowing through the coil. Other position sensors include a capacitive non-contact displacement sensor that detects the distance in a non-contact manner by utilizing the fact that the capacitance is inversely proportional to the distance between the sensor electrode and the measurement object, and a light beam from the measurement object. It is possible to use an optical sensor or the like that detects the position of the sensor using a PSD (semiconductor position detector). A speed sensor may be used instead of the acceleration sensor.

  A reticle base 37 is fixed to the upper portion of the first column 36, a second column 38 is fixed so as to cover the reticle base 37, and the illumination optical system ILS of FIG. The illumination system subchamber 39 is fixed. The laser light source 1 of FIG. 1 is installed on the floor FL outside the pedestal 32 of FIG. 2 as an example, and the illumination light IL emitted from the laser light source 1 is illumination optics via a beam transmission system (not shown). Guided to the system ILS. The reticle stage RST that holds the reticle R is placed on the reticle base 37. In FIG. 2, a column structure CL is constituted by a first column 36, a reticle base 37, and a second column 38. The column structure CL holds the projection optical system PL, the reticle stage RST, and the illumination optical system ILS while being supported on the upper surface of the base plate 33 via a plurality of active vibration isolation tables 35. A part of the illumination optical system ILS may be arranged separately from the column structure CL.

The set of acceleration sensors 40 includes, for example, three Z-axis acceleration sensors that measure the acceleration in the Z direction at three locations that are not substantially on the same straight line in the XY plane, and the X direction at two locations that are separated in the Y direction. Are comprised of two X-axis acceleration sensors that measure the acceleration in the Y direction, and two Y-axis acceleration sensors that measure the acceleration in the Y direction at two locations separated in the X direction. The set of acceleration sensors 40 measures the acceleration in the X direction, the Y direction, and the Z direction of the column structure CL, and the rotational acceleration [rad / s ² ] around the X axis, the Y axis, and the Z axis. The Similarly, the position of the column structure CL in the X direction, the Y direction, and the Z direction, and the rotation angles around the X axis, the Y axis, and the Z axis are measured by the pair of position sensors (not shown). Is done. Based on these measured values, the air dampers and electromagnetic dampers in the plurality of vibration isolation tables 35 are configured so that the vibration of the column structure CL is kept small, the inclination angle of the column structure CL, and the height in the Z direction. Acts to maintain a constant value. Further, when the column structure CL is levitated and supported at a predetermined height position (target position), the pressure in the air damper or the thrust of the electromagnetic damper is controlled to give the air damper rigidity in the Z direction. Details of this control will be described later.

  Further, three or four active vibration isolation tables 41 are provided on a region surrounded by a plurality of support members (not shown) provided on the base plate 33 on the pedestal 32 and the active vibration isolation table 35. The wafer base 42 is supported via the. On wafer base 42, wafer stage WST for holding wafer W is movably mounted. The anti-vibration table 41 includes small air dampers and electromagnetic dampers having the same configuration as the anti-vibration table 35, and the anti-vibration table 41 supports the wafer stage WST (substrate stage) on the upper surface of the base plate 33. The anti-vibration table 41 actively suppresses vibrations of the wafer base 42 and the wafer stage WST based on measurement information from an acceleration sensor and a position sensor (not shown) on the wafer base 42.

  The above-described anti-vibration tables 35 and 41 and their control systems (described later) each constitute an anti-vibration device. Each of these vibration isolators can also be called an AVIS (Active Vibration Isolation System) which is an active vibration isolation system. In the configuration shown in FIG. 2, the anti-vibration table 35 supports the reticle stage RST and the projection optical system PL via the column structure CL, whereas the anti-vibration table 41 supports the wafer via the wafer base 42. Only stage WST is supported. Further, the scanning speed of reticle stage RST during scanning exposure is higher than the scanning speed of wafer stage WST by a reciprocal number (for example, 4 times) the projection magnification β. For this reason, the column structure CL is more susceptible to vibration than the wafer base 42. Therefore, the vibration isolation performance of the vibration isolation table 35 can be set higher than the vibration isolation performance of the vibration isolation table 41. In this case, for example, the rigidity of the anti-vibration table 35 is set lower than that of the anti-vibration table 41, or the air damper provided on the anti-vibration table 41 is set so that the position of the wafer base 42 in the Z direction is substantially constant. It is only necessary to control.

  In addition to the configuration shown in FIG. 2, for example, the wafer base 42 and the wafer stage WST may be suspended from the bottom surface of the first column 36 holding the projection optical system PL. In such a configuration, reticle stage RST, projection optical system PL, and wafer stage WST are all supported by a plurality of anti-vibration bases 35. Further, the column that supports the projection optical system PL and the wafer stage WST and the column that supports the reticle stage RST are separated, and these are supported via the vibration isolation table similar to the vibration isolation table 35, respectively. Also good. Further, the reticle stage RST, the projection optical system PL, and the wafer stage WST may be supported independently of each other via a vibration isolation table similar to the vibration isolation table 35.

  As described above, the active vibration isolation tables 35 and 41 shown in FIG. 2 can have substantially the same configuration. Below, the structure of the anti-vibration table 35 and its control system is demonstrated typically. In the following description, a mechanism for suppressing vibration in the Z direction, which is a direction parallel to the optical axis AX of the projection optical system PL, will be described. This is a mechanism for suppressing vibration in the X direction and the Y direction. The present invention can be similarly applied to a mechanism that suppresses vibration in the rotational direction around the X axis, the Y axis, and the Z axis.

  FIG. 3 is a partially cutaway view showing one vibration isolator 35 and its control system in FIG. In FIG. 3, on a base plate 33 on the pedestal 32, a plate-shaped mount portion 43a substantially perpendicular to the Z-axis and a leg portion 43b for supporting the mount portion 43a on the base plate 33 with a predetermined interval are provided. One frame 43 is fixed. A substantially cylindrical storage member 44 having a closed bottom surface is placed on the top surface of the mount portion 43 a of the first frame 43, and an air damper 45 as a gas damper is stored in the storage member 44. A substantially cylindrical movable member 47 is mounted on the upper portion of the air damper 45 so as to be displaced in the Z direction, and the upper portion of the movable member 47 is fixed to the bottom surface of the first column 36 (structure). Yes. In this configuration, the storage member 44 and the movable member 47 correspond to a holding mechanism for the air damper 45. The movable member 47 and the first column 36 are supported by the gas pressure in the air damper 45 so that they can be displaced in the Z direction (supporting direction for supporting the first column 36) with respect to the mount portion 43a. Note that the storage member 44 and the air damper 45 can be integrally regarded as a gas damper, and the movable member 47 can be integrated with the first column 36.

  The air damper 45 is one in which air is sealed in a flexible hollow bag made of rubber or the like (or a hollow diaphragm made of rubber or the like) in a state where the pressure can be controlled. That is, the air damper 45 is passed through an opening (not shown) on the side surface of the storage member 44 through a flexible pipe 55 equipped with a servo valve 56 capable of controlling the air flow rate. The air source 54 in which the above air is accumulated is connected. A gas supply device 52 is configured including an air source 54, a part of the piping 55, and a servo valve 56. The air source 54 is provided with an intake pipe 53 for taking in air from the outside. As the air source 54, for example, an air compressor and an air cylinder filled with air pressurized by the air compressor are combined. Can be used. Further, on the side surface of the air damper 45, there is provided a pressure sensor 28 for measuring the pressure of the air in the air damper 45 through a hollow pipe passing through an opening (not shown) on the side surface of the storage member 44. The measured value (signal corresponding to the pressure information) of the force sensor 28 is supplied to the vibration isolator control system 51. As the pressure sensor 28, a sensor in which a strain gauge is fixed to a thin metal diaphragm, a sensor using deformation of a silicon substrate, or the like can be used.

  Further, a pair of flat connecting members 48a and 48b extending in the Z direction so as to sandwich the movable member 47 in the X direction are fixed, and flat plates substantially perpendicular to the Z axis are provided at the lower ends of the connecting members 48a and 48b. A shaped interlocking member 49 is fixed. The movable member 47, the connecting members 48a and 48b, and the interlocking member 49 constitute the second frame 46. 4 is a plan view of the first frame 43 as viewed from the movable member 47 side in FIG. As shown in FIG. 4, two openings 43c and 43d are formed in the upper part of the first frame 43 (mount part 43a in FIG. 3), and connecting members 48a and 48b are inserted into these openings 43c and 43d, respectively. Has been. With this configuration, the interlocking member 49 of the second frame 46 is supported in a space surrounded by the first frame 43 and the base plate 33 so as to be displaceable in the Z direction without contacting the first frame 43.

  Returning to FIG. 3, the second frame 46 is displaced in the Z direction in conjunction with the first column 36. A voice coil motor 50 as an electromagnetic damper is installed between the second frame 46 and the base plate 33. The voice coil motor 50 is fixed to the upper surface of the base plate 33 and fixed to the stator 50b in which permanent magnets are arranged at a predetermined pitch in the Z direction, and fixed to the bottom surface of the interlocking member 49 of the second frame 46, and the coil is mounted. It is comprised from the needle | mover 50a. As described above, the vibration isolation table 35 includes the first frame 43, the storage member 44, the air damper 45, the second frame 46, and the voice coil motor 50.

  Since the air damper 45 and the voice coil motor 50 are arranged in series in the Z direction (displacement direction of the first column 36), the vibration isolator 35 having the above configuration can be reduced in size. Further, since the force (pressure) by the air damper 45 and the thrust by the voice coil motor 50 act on the same straight line that is substantially parallel to the Z axis, the first column even if the air damper 45 and the voice coil motor 50 are acted simultaneously. No unnecessary force such as moment acts on 36. The air damper 45 (gas damper) and the voice coil motor 50 (electromagnetic damper) apply a force from the base plate 33 to the first column 36 substantially in parallel. Accordingly, most of the weight of the first column 36 is supported by the air damper 45, and the thrust in the Z direction of the voice coil motor 50 is mainly for suppressing the vibration of the first column 36 in the high frequency region in the Z direction. Since it can be used, vibration can be suppressed in a wide frequency range even when the weight applied to the first column 36 (structure) is large.

  As described above, the acceleration sensor 40 is fixed to the first column 36, and the acceleration sensor 40 measures acceleration information in the Z direction of the first column 36 as an example. In addition to the acceleration sensor 40, a position sensor 29 is fixed to a connecting member 48a that is integrally displaced with the first column 36, and the first column with the first frame 43 and the base plate 33 as a reference by the position sensor 29. Information on the relative position of 36 in the Z direction or relative displacement in the Z direction is measured. Although not shown, the position sensor 29 is provided at a plurality of positions with respect to one vibration isolating table 35, so that not only the position of the first column 36 in the Z direction but also the X direction and the Y direction are provided. The position in the direction and the amount of rotation around the X, Y, and Z axes can be determined. As an example, the acceleration sensor 40 is a piezoelectric acceleration sensor, and the position sensor 29 is an eddy current displacement sensor.

  The measurement values (signals corresponding to the acceleration and position) of the acceleration sensor 40 and the position sensor 29 are supplied to the anti-vibration table control system 51. The structure including the vibration isolator 35, the acceleration sensor 40, the position sensor 29, the gas supply device 52, and the vibration isolator control system 51 constitutes a vibration isolator. The anti-vibration table control system 51 controls the flow rate of the air passing through the servo valve 56 in the gas supply device 52 based on the measured values of the pressure sensor 28, the acceleration sensor 40, and the position sensor 29, and the air damper 45. Control the air pressure inside. In parallel with this operation, the anti-vibration table control system 51 controls the current flowing in the coil of the mover 50a of the voice coil motor 50 on the basis of the measurement values of the acceleration sensor 40 and the position sensor 29. The thrust in the Z direction by the voice coil motor 50 is controlled so that the position of 36 in the Z direction becomes a predetermined target position.

  Next, a control method for controlling the pressure in the air damper 45 by the vibration isolator control system 51 of FIG. 3 will be described. First, a dynamic model of the air damper 45 that is the controlled object will be described. FIG. 5 is a diagram illustrating a dynamic model of the air damper 45 provided in the vibration isolation table 35. In FIG. 5, the installation surface L1 corresponds to the upper surface of the base plate 33 in FIG. 3, and the structure ST corresponds to the first column 36 in FIG. More precisely, the structure ST includes the first column 36, the reticle base 37, the reticle stage RST, the second column 38, the illumination system sub-chamber 39, the illumination optical system ILS, the projection optical system PL, and the like shown in FIG. It is.

  Here, the mass of the portion supported by the air damper 45 in the structure ST is M, the viscous friction coefficient of the air damper 45 is D, and the spring constant is k. The mass M is a coefficient of resistance (inertia) according to the acceleration of the structure ST, the viscous friction coefficient D is a coefficient of low drag according to the speed of the structure ST, and the spring constant k is the position of the structure ST. It can be regarded as a coefficient of resistance according to (that is, the height of the air damper 45). In other words, the spring constant k also corresponds to the rigidity of the air damper 45. In the present embodiment, the vibration isolator 35 is made to have low rigidity by reducing the spring constant k of the air damper 45.

The spring constant k of the air damper 45 can be expressed three primary stiffness _{k a,} k f, the sum of _{k m.}
Rigidity k _a : Rigidity due to compressibility of air that is gas in the air damper 45 Rigidity k _f : Rigidity of material such as rubber constituting the air damper 45 Rigidity k _m : Rigidity depending on the structure of the holding mechanism of the air damper 45 describing stiffness _{k a, k f,} for each of the _{k m.}

(A) Rigidity k _a due to compressibility of air, which is a gas in the air damper 45
The effective pressure receiving area from the air damper 45 of the movable member 47 in FIG. 3 is A, the air pressure (absolute pressure) in the air damper 45 is P, the volume of the air damper 45 is V, and the coefficient of stiffness (polytropic index) is n. Then, the stiffness _{k a} is expressed by the following equation (1).
k _a = (n · A ² · P) / V (1)
Here, assuming that the height of the air damper 45 (the distance between the storage member 44 and the movable member 47) is H, (V = A · H), the above equation (1) is transformed into the following equation (2). can do.
k _a = (n · A · P) / H (2)

The height H corresponds to the position of the air damper 45 (gas damper) in the support direction of the structure, and the relative position in the Z direction of the connecting member 48a (first column 36) measured by the position sensor 29. (Displacement) is the height of the air damper 45 when the measured relative position is 0 (target position: this is measured in advance and stored in the storage unit in the vibration isolator control system 51). It is obtained by adding. When the equation (2) is modified and rewritten, the air pressure P in the air damper 45 is expressed by the following equation (3).
_{P = (k a · H)} / (n · A) ...... (3)

Therefore, in case of supporting the target position described above the first column 36, the value of small rigidity k _a than the conventional, and the air damper 45 obtained from the measured value of the position sensor 29 a height H, respectively (3) calculate the pressure P into equation, anti-vibration base control system 51 as the pressure P is the pressure in the air damper 45 is rigid k _a is reduced by controlling the flow rate of the servo valve 56. As a result, since the spring constant k of the air damper 45 is also reduced, the natural frequency is lowered and the vibration isolation performance is improved. For example, when the height H of the air damper 45 becomes low, the vibration isolation performance can be improved by extracting the air in the air damper 45 and reducing the pressure in the air damper 45.

(B) Rigidity k _{f of} a material such as rubber constituting the air damper 45
If the material constituting the air damper 45 is rubber, its rigidity is represented by the following equation (4) as an example. Actually, the stiffness k _f may be measured using an actual air damper 45.
k _f = about 90 [N / mm] (4)
Therefore, as the material of the air damper 45, as rigid as possible k _f smaller ones can be reduced spring constant k of the air damper 45 by use of, it is possible to vibration isolation performance improves as a result.

(C) depends on the structure of the holding mechanism of the air damper 45 the rigid _{k m}
To calculate the specific stiffness k _m, Figure 6 shows the structure of the holding mechanism of the air damper 45 shown in FIG. FIG. 6 is a cross-sectional view showing a holding mechanism for the air damper 45 provided in the vibration isolator 35. As shown in FIG. 6, the flexible air damper 45 is housed in a substantially cylindrical housing member 44 whose bottom is closed, and the air damper 45 is placed on the air damper 45 via a substantially cylindrical movable member 47. One column 36 is placed. The storage member 44 and the movable member 47 are each axially symmetric with respect to a symmetry axis SX parallel to the Z axis, and are not in contact with the opening 44a at the top of the storage member 44 in the direction of the first column 36 (in the Z direction in FIG. 3). The lower end 47a of the movable member 47 is disposed so as to be freely displaceable. The opening 44 a (inner surface) of the storage member 44 has a conical side surface shape whose radius gradually increases toward the first column 36, and the outer surface of the lower end portion 47 a of the movable member 47 facing the opening 44 a (inner surface) faces the first column 36. It has a conical side surface shape with a gradually decreasing radius, and the lower end portion 47a has an inversely tapered structure. The inclination angle (taper angle) outward of the cylindrical surface of the opening 44a formed in the storage member 44 and the inclination angle (taper angle) inward of the outer surface of the lower end portion 47a of the movable member 47 with respect to the cylindrical surface are respectively θ and θ. To do.

  Further, as indicated by a solid line in FIG. 6, a state in which the opening 44a of the storage member 44 and the lower end portion 47a of the movable member 47 face each other without being vertically shifted (Z direction) is defined as a reference state. The position in the Z direction of the first column 36 in FIG. 3 when the positional relationship between the storage member 44 and the movable member 47 is in its reference state is the design target position of the first column 36. In the reference state, the offset of the position sensor 29 is adjusted so that the relative position in the Z direction of the first column 36 measured by the position sensor 29 of FIG. As shown in FIG. 6, since there is a gap between the opening 44a of the storage member 44 and the lower end portion 47a of the movable member 47 and the air damper 45 is flexible, a part of the air damper 45 (the protruding portion 45a). ) Protrudes into the gap.

Further, since the lower end portion 47a of the movable member 47 has a reverse taper structure, the effective pressure receiving area A from the air damper 45 to the movable member 47 is the height H of the air damper 45, that is, the Z direction of the movable member 47 (first column 36). Varies depending on the position. In the present embodiment, the effective pressure receiving area A is assumed to be the area inside the circumference passing through the center of the protruding portion 45a of the air damper 45. Further, the radius from the symmetry axis SX to the center C ₀ of the protruding portion 45a when the positional relationship between the storage member 44 and the movable member 47 is in the reference state is R _0, and as shown by a two-dot chain line in FIG. Let R be the radius from the axis of symmetry SX to the center C of the protruding portion 45b when the movable member 47 is displaced toward the storage member 44 by z. At this time, since the taper angle of the inner surface of the opening 44a and the outer surface of the lower end portion 47a is θ, assuming that the radii of curvature of the protruding portions 45a and 45b are equal, it is parallel to the symmetry axis SX from the center _C0 to the center C. The direction interval δz is expressed by the following equation (5).
δz = z / 2 (5)

When the above equation (5) is used, the radius R is expressed by the following equation (6).
R = R ₀ −δz · tan θ = R ₀ − (z · 2) · tan θ (6)
At this time, if the displacement z is small, the effective pressure receiving area A can be approximated by the following equation (7).
A≈θ (R ₀ ² −R ₀ · tan θ) (7)
Moreover, the use of the pressure P of the air in the air damper 45, the stiffness k _m force F of the air damper 45 acting on the first column 36 depends next P · A, the structure of the holding mechanism of the air damper 45, the mosquito F It is a differentiation with respect to displacement z. Therefore, from equation (7), the stiffness _{k m} is expressed by the following equation (8).
_{k m = dF / dz ≒ -P} · θ · R 0 · tanθ ...... (8)

That is, as shown in FIG. 6, the sign of code positively to the rigidity k _m in the direction of the housing member 44 of the displacement z of the movable member 47 becomes negative. This means that by adopting the inverted Taber structure shown in FIG. 6, the movable member 47 is acted on by the force drawn toward the storage member 44 (−Z direction), thereby reducing the rigidity.
When the above equation (8) is rewritten, the pressure P is expressed by the following equation (9).
_{P = -k m / (θ ·} R 0 · tanθ) ...... (9)

Therefore, in case of supporting the target position described above the first column 36, the taper angle of a desired negative stiffness k _m, the value of the radius R ₀ for determining the effective pressure receiving area A of the reference state, and the holding mechanism The pressure P (positive value) is calculated by substituting θ into the above equation (9), and the anti-vibration table control system 51 controls the flow rate of the servo valve 56 so that the pressure P becomes the pressure in the air damper 45. Can be controlled. Thereby, the rigidity k _m which depends on the structure of the holding mechanism is a spring constant k of the air damper 45 is reduced by a negative value, it is possible to natural frequency is improved performance vibration isolation performance decreases.

When the first column 36 is supported at the target position described above, the control method described using the above-described equation (3) and the control method described using the above-described equation (9) are used in combination. You can also. When performing such control is based on a rigid k _m which depends on the target value of the pressure P based on the stiffness k _a by the compressibility of the air described above (3), the structure of the air damper 45 of the above-mentioned (9) What is necessary is just to control so that the target value of the pressure P is made substantially equal and the pressure in the air damper 45 becomes the target value (or the average value of both). Incidentally, as shown in equation (8), since the sign of rigidity k _m becomes negative, (2) rigidity k _a by the compressibility of air shown in the _expression of the air damper 45 shown in the above (4) stiffness k _f of the material _and the spring constant k (stiffness) of the air damper 45 which is the sum of the stiffness k _m which depends on the structure of the holding mechanism shown in equation (8) becomes a value close to 0, and negative values It may be possible.

  Here, if the vibration isolator 35 is in a steady state supporting the first column 36 at the target position, the air pressure in the air damper 45 is controlled as described above, and further in the Z direction by the voice coil motor 50. By using this thrust together with the control, the first column 36 is stably supported by the low-rigidity vibration isolation table 35, and the influence of the vibration of the floor FL is effectively suppressed by the vibration isolation table 35. However, when the exposure apparatus EX is started up, air supply to the air damper 45 is started, and a reset process for floating the first column 36 and supporting it at the target position is performed. Further, at the time of regular or irregular maintenance, after the air of the air damper 45 is once extracted, the supply of air to the air damper 45 is started again, and the first column 36 is floated and reset processing is performed to support the target position. During the reset process, the vibration isolator 35 is low in rigidity, and therefore the first column 36 supported by the vibration isolator 35 falls down or shakes and becomes unstable. For this reason, the anti-vibration table control system 51 controls the pressure of the air in the air damper 45 or the thrust in the Z direction by the voice coil motor 50 during the reset process to give the air damper 45 rigidity in the Z direction.

  FIG. 7 is a diagram for explaining a control method for imparting rigidity in the Z direction to the air damper 45 at the time of resetting. Since the low-rigidity anti-vibration table 35 has a weak force acting in a direction to return the displacement of the first column 36 (structure) from the target position, the displacement of the first column 36 tends to be maintained. That is, as shown in FIG. 7A, when the first column 36 (structure) supported by the anti-vibration table 35 is displaced from the target position downward (−Z direction) by Δz, the first column 36 remains displaced by about Δz in the downward direction. Conversely, when it is displaced upward by Δz from the target position (+ Z direction), it remains displaced by about Δz in the upward direction. Further, when the air damper 45 has negative rigidity, when the first column 36 is displaced from the target position, there is a characteristic that a force that increases the displacement acts.

  Consider a case where the first column 36 is positioned at a target position by reset processing using the vibration isolator 35 having the above characteristics. At the time when the supply of air to the air damper 45 is started, the air damper 45 is located below (−Z direction) from the target position, but the first column 36 rises and approaches the target position with the supply of air. Here, if the air damper 45 has positive rigidity, even if the first column 36 goes too far upward (+ Z direction) from the target position, the first column 36 returns to the target position and returns to the target position. Shows the behavior of convergence. However, when the air damper 45 has negative rigidity, the displacement is increased and the air damper 45 cannot be positioned at the target position.

For this reason, in this embodiment, the air pressure in the air damper 45 or the thrust in the Z direction by the voice coil motor 50 is controlled to give the air damper 45 rigidity in the Z direction. Stiffness to be imparted to the air damper 45 is a rigid above code positively stiffness k _m is negative. In other words, the rigidity imparting When _{k the add,} to impart stiffness _{k the add} the following expression (10) is satisfied. However, the stiffness k _add is a positive value.
_{k add + k m> 0 ......} (10)

Specifically, the force F shown in the following equation (11) is generated. However, in the following equation (11), Z ₀ is a coordinate in the Z direction of the target position, and z is a coordinate in the Z direction of the first column 36 (structure).
F = −k _add (z−Z ₀ ) (11)
Referring to the above equation (11), the air pressure generated in the air damper 45 or the thrust in the Z direction generated by the voice coil motor 50 depends on the difference between the target position Z ₀ and the position of the first column 36. It becomes the size.

  Specifically, when controlling the thrust in the Z direction by the voice coil motor 50, the thrust in the upward direction (+ Z direction) is applied when the first column 36 is positioned below (−Z direction) the target position. When it is positioned above the target position (+ Z direction), a downward thrust (−Z direction) is generated. In this case, the voice coil motor 50 does not directly give rigidity to the air damper 45, but as described with reference to FIG. 3, the air damper 45 and the voice coil motor 50 are separated from the base plate 33 by the first. Since a force can be applied in parallel to the column 36, the air damper 45 is substantially given rigidity in the Z direction.

  Further, when controlling the pressure of air in the air damper 45, when the first column 36 is positioned below the target position (in the −Z direction), the air in the air damper 45 is supplied and above the target position ( When it is positioned in the + Z direction), the air damper 45 is evacuated. In the case of such control, since the amount of air inside the air damper 45 is controlled, rigidity can be directly imparted to the air damper 45.

  By performing the above control, as shown in FIG. 7B, when the first column 36 does not exceed the target position and is positioned below (−Z direction) the target position, the target position is reached. A heading force F1 is generated and rigidity toward the target position is given. On the other hand, when the first column 36 is located above the target position and above the target position (+ Z direction), a force F2 for returning to the target position is generated and rigidity for returning to the target position is given. By performing the process of adding the above rigidity to the air damper 45, even if the air damper 45 itself has a negative rigidity, the first column 36 behaves to converge to the target position, and as a result, the first column 36 The column 36 can be positioned at the target position.

  After the first column 36 is positioned at the target position by the reset process, it is necessary to improve the vibration isolation performance by reducing the vibration isolation table 35 to low rigidity. For this reason, the rigidity given to the air damper 45 is removed, the control method explained using the above-described equation (3), the control method explained using the above-mentioned equation (9), or the control method using these methods in combination. Is used to control the pressure of the air in the air damper 45. Further, in addition to the control of the air pressure in the air damper 45, servo control by the voice coil motor 50 may be performed.

  For the rigidity given to the air damper 45 until the first column 36 is positioned at the target position, for example, an allowable value AR is set for the target position as shown in FIG. It is desirable to remove the upper limit value and the lower limit value when they fall within the allowable value AR. Further, the rigidity may be removed when the thrust generated from the voice coil motor 50 becomes a predetermined value or less. Furthermore, when the upper limit value and the lower limit value of the vibration of the vibration isolation table 35 are within the above-described allowable value AR, rigidity is given to the air damper 45, and the thrust generated from the voice coil motor 50 becomes a predetermined value or less. You may make it remove rigidity at the time.

  Next, a configuration example of the vibration isolator control system 51 in FIG. 3 will be described. FIG. 8 is a block diagram showing a control unit related to the control of the voice coil motor 50 of the vibration isolator control system 51. In addition to the control unit shown in FIG. 8, the anti-vibration table control system 51 is also provided with a control unit related to the control of the servo valve 56, but the description of this control unit is omitted. The anti-vibration table control system 51 is composed of a digital circuit including a microcomputer, but may be composed of an analog circuit. As shown in FIG. 8, the control unit related to the control of the voice coil motor 50 of the anti-vibration table control system 51 performs the first control unit 60a for performing the reset process and the first column 36 after positioning the first column 36 at the target position. A second control unit 60b for servo-controlling the shaking table 35 by the voice coil motor 50 is configured.

  The first control unit 60a includes a target value setting unit 61, a calculation unit 62, and an amplification unit 63. The target value setting unit 61 outputs a command value indicating the target position in the Z direction of the vibration isolation table 35 (first column 36) provided at three or four locations on the base plate 33 during the reset process. The calculation unit 62 calculates and outputs an error signal for each image stabilization table 35 by subtracting the measurement value of the position sensor 29 provided on the image stabilization table 35 from the command value of the target position setting unit 61. The amplifying unit 63 outputs a control signal obtained by amplifying the error signal output from the calculating unit 62 with a predetermined amplification factor.

  The second control unit 60 b includes a target value setting unit 64, a calculation unit 65, a position controller 66, a calculation unit 67, a speed controller 68, a low-pass filter 69, a high-pass filter 70, and an integrator 71. The target value setting unit 64 determines the positions of the first column 36 disposed at or near the target position in the X direction, the Y direction, and the Z direction, and the rotation amounts around the X axis, the Y axis, and the Z axis. The indicated command value is output. The calculation unit 65 calculates and outputs an error signal for each image stabilization table 35 by subtracting the measurement value of the position sensor 29 provided on the image stabilization table 35 from the command value of the target position setting unit 64. This error signal includes an error signal indicating a position error in the X direction, the Y direction, and the Z direction for each vibration isolator 35 and an error signal indicating a rotation amount error around the X axis, the Y axis, and the Z axis. . The position controller 66 generates and outputs a position control signal for controlling each position of the image stabilizer 35 based on the error signal output from the calculation unit 65.

  The computing unit 67 outputs an error signal obtained by subtracting the measurement value of the acceleration sensor 40 (signal through the high-pass filter 70 and the integrator 71) from the position control signal of the position controller 66. The speed controller 68 generates and outputs a speed control signal for controlling the speed of each of the image stabilizers 35 based on the error signal output from the calculation unit 67. The low-pass filter 69 removes the high frequency component contained in the speed control signal, passes only the low frequency component, and outputs it as a control signal. This eliminates control instability due to the high-frequency component being included in the speed control signal. The high pass filter 70 removes the low frequency component included in the measurement value output from the acceleration sensor 40 and outputs only the high frequency component. The integrator 71 integrates the signal output from the high-pass filter 70 and converts the measurement value indicating the acceleration of the vibration isolation table 35 output from the acceleration sensor 40 into a signal indicating the speed.

  In addition, a switch SW is provided for switching between the control signal generated by the first control unit 60a and the control signal generated by the second control unit 60b to control the voice coil motor 50. Yes. When the switch SW is on the terminal T1 side of the first control unit 60a, the voice coil motor 50 is controlled by the control signal generated by the first control unit 60a and is on the terminal T2 side of the second control unit 60b. The voice coil motor 50 is controlled by the control signal generated by the second controller 60b. The switch SW can be in a neutral state that is not on either side of the terminals T1 and T2.

  Next, an example of reset processing will be described. When performing the reset process, first, the switch SW is set to a neutral state. In this state, a control unit (not shown) related to the control of the servo valve 56 outputs a pressure command value, controls the flow rate of air passing through the servo valve 56 in the gas supply device 52, and connects the pipe 55 from the air source 54. The supply of air to the air damper 45 is started. Here, since the switch SW is set to the neutral state, the thrust of the voice coil motor 50 is zero. Therefore, at the start of the reset process, only the force of the air damper 45 acts on the first column 36, and the first column 36 is lifted by this force. At the time when the first column 36 starts to float, a control unit (not shown) related to the control of the servo valve 56 is positioned based on the measurement values of the position sensor 29 and the acceleration sensor 40 provided on the vibration isolation table 35. Control and speed control. At this time, the position control is preferably performed by PI (proportional, integral) control. The speed control is preferably performed by P (proportional) control.

  When the above control is performed, the first column 36 gradually rises and approaches the target position. When the upper limit value and the lower limit value of the vibration of the first column 36 fall within the allowable value AR shown in FIG. 7C, for example, the switch SW is set to the terminal T1 side and the control by the first control unit 60a is started. Is done. When this control is started, a control signal obtained by amplifying the error signal obtained by subtracting the measured value of the position sensor 29 from the command value output from the target value setting unit 61 by the amplifying unit 63 is supplied to the voice coil motor 50. The thrust shown by the above-described equation (11) is generated from the coil motor 50. Thereby, in addition to the force of the air damper 45, the thrust of the voice coil motor 50 acts on the first column 36, and the rigidity in the Z direction is substantially imparted to the air damper 45.

  As described with reference to FIG. 7B, the rigidity imparted to the air damper 45 is such that when the first column 36 is positioned below (−Z direction) the target position, the first column 36 is targeted. The first column 36 behaves closer to the target position under the control of the first control unit 60a because it is returned to the target position when it is directed to the position and positioned above the target position (+ Z direction). For example, the switch SW is set to the terminal T2 side when the thrust generated from the voice coil motor 50 becomes a predetermined value or less. As a result, the rigidity imparted to the air damper 45 is removed, and the air damper 45 has low rigidity.

  Here, it is desirable to smoothly switch the switch SW from the terminal T1 side to the terminal T2 side so that the first column 36 does not vibrate. For example, the switch SW has a gain set at a predetermined time. It is preferable to change the gain in a quadratic curve. The reset process is completed by the above control. After the reset process is completed, servo control is performed by the second control unit 60b.

  In the above example, the case where rigidity is imparted to the air damper 45 using the voice coil motor 50 has been described as an example. However, even if rigidity is imparted by controlling the pressure of the air in the air damper 45. good. Moreover, although the case where the servo control by the 2nd control part 60b was performed after a reset process was mentioned as an example, you may make only the control the pressure of the air in the air damper 45, without performing this servo control. However, in consideration of control responsiveness, it is desirable to use the voice coil motor 50 to give rigidity to the air damper 45 and to perform control after reset processing. In the above example, the first column 36 is supported only by the air damper 45 until the vibration of the first column 36 falls within the allowable value AR after the reset process is started. However, the reset process is started. After the first column 36 is lifted, the switch SW may be set to the terminal T1 side so that the first column 36 is supported by the force of the air damper 45 and the thrust of the voice coil motor 50.

  9 and 10 are diagrams showing examples of reset processing results, where (a) is a diagram showing a change in position of the first column 36 in the Z direction, and (b) is a change in thrust of the voice coil motor 50. FIG. FIG. 9 shows a processing result when the reset processing is performed in a relatively long time, and FIG. 10 shows a processing result when the reset processing is performed in a relatively short time. In the processing result shown in FIG. 9, the supply of air to the air damper 45 is started at time 0, the first column 36 is lifted, the voice coil motor 50 adds rigidity to the air damper 45 at time t11, and is applied at time t12. Rigidity is removed.

  As shown in FIG. 9A, when the supply of air to the air damper 45 is started at time 0, the first column 36 floats and moves upward (+ Z direction) with time. When the voice coil motor 50 starts to give rigidity to the air damper 45 at time t11, as shown in FIG. 9B, a thrust force that pushes up the first column 36 upward (+ Z direction) is generated. Between times t11 and t12, the thrust of the voice coil motor 50 gradually decreases as the first column 36 approaches the target position.

  Referring to FIG. 9 (a), it can be seen that the first column 36 does not approach the target position at a constant speed, but the rising speed changes due to the influence of the first column 36 falling or shaking, It can be seen that the thrust of the voice coil motor 50 changes according to this speed change. By such processing, the first column 36 can be stably supported. When the rigidity imparted to the air damper 45 is removed at time t12, the thrust is greatly changed according to the displacement of the first column 36 with respect to the target position thereafter, and the first column 36 is positioned at the target position. .

  Further, in the processing result shown in FIG. 10, the supply of air to the air damper 45 is started at time 0, the first column 36 is lifted, and the voice coil motor 50 provides rigidity to the air damper 45 at time t21. The rigidity given in is removed. Referring to FIG. 10A, it can be seen that the first column 36 exceeds the target position at a time before time t22 when the rigidity applied to the air damper 45 is removed. When the first column 36 exceeds the target position, a thrust is generated that pulls the first column 36 downward (in the −Z direction) as shown in FIG. 10B, and the position of the first column 36 is caused by this thrust. It can be seen that the position is changing close to the target position.

  From the above, even when the reset process is performed, the first column 36 can be stably supported, and even if the air damper 45 has negative rigidity, it can be positioned at the target position. Further, in the reset process, the reset process can be simultaneously performed on the anti-vibration bases 35 provided at three or four locations on the base plate 33, so that the time required for the reset process can be shortened.

  The vibration control device control method and the exposure method according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the above-described embodiment, the step-and-scan type exposure apparatus has been described as an example. However, a step-and-repeat type exposure apparatus (so-called stepper) that collectively transfers a reticle pattern is also used. The present invention can be applied.

  Further, the above exposure apparatus includes an exposure apparatus used for manufacturing a semiconductor element to transfer a device pattern onto a semiconductor substrate, an exposure apparatus used for manufacturing a liquid crystal display element to transfer a circuit pattern onto a glass plate, and a thin film. The present invention can also be applied to an exposure apparatus that is used for manufacturing a magnetic head and transfers a device pattern onto a ceramic wafer, and an exposure apparatus that is used to manufacture an image sensor such as a CCD. Further, in the above-described embodiment, the vibration isolator provided in the exposure apparatus has been described. However, the present invention can be applied to AVIS that is an active vibration isolation system in general.

  Further, when a semiconductor device is manufactured using the exposure apparatus of the above embodiment, the semiconductor device includes a step of designing a function / performance of the device, a step of manufacturing a reticle based on the design step, and a silicon material. The wafer W is manufactured through a step of forming the wafer W, a step of exposing the pattern of the reticle R onto the wafer W by the exposure apparatus of the above-described embodiment, a device assembly step (including a dicing process, a bonding process, and a package process), an inspection step, and the like. The

  The present invention can also be applied to an exposure apparatus using a liquid immersion method as disclosed in International Publication No. 99/49504. In the present invention, an immersion exposure apparatus that locally fills the space between the projection optical system PL and the wafer W with a liquid, a substrate to be exposed as disclosed in JP-A-6-124873, is held. An immersion exposure apparatus for moving a stage in a liquid tank, a liquid tank having a predetermined depth formed on a stage as disclosed in JP-A-10-303114, and holding a substrate in the liquid tank The present invention can be applied to any exposure apparatus of the exposure apparatus.

It is a block diagram of each functional unit which comprises the exposure apparatus in which the control method and exposure method of a vibration isolator by one Embodiment of this invention are used. It is a partially cutaway view showing a state where the exposure apparatus EX is installed on the floor. FIG. 3 is a partially cutaway view showing one vibration isolator 35 in FIG. 2 and its control system. FIG. 4 is a plan view of the first frame 43 as viewed from the movable member 47 side in FIG. 3. It is a figure which shows the dynamic model of the air damper 45 provided in the vibration isolator 35. FIG. 4 is a cross-sectional view showing a holding mechanism for an air damper 45 provided in the vibration isolation table 35. FIG. It is a figure for demonstrating the control method which provides the rigidity of a Z direction to the air damper 45 at the time of reset. It is a block diagram which shows the control part which concerns on control of the voice coil motor 50 of the vibration isolator control system 51. FIG. It is a figure which shows an example of a reset process result. It is a figure which shows the other example of a reset process result.

Explanation of symbols

29 Position sensor (anti-vibration device)
35 Anti-vibration stand (anti-vibration device)
36 First column (structure)
40 Acceleration sensor (anti-vibration device)
45 Gas damper (air damper)
51 Anti-vibration table control system (vibration isolator)
52 Gas supply device (vibration isolation device)
PL projection optical system R reticle (mask)
RST reticle stage (mask stage)
W wafer (substrate)
WST Wafer stage (substrate stage)

Claims (8)

A control method of a vibration isolator provided with a gas damper that is supplied with gas and supports a structure,
A control of a vibration isolator that supplies the gas to the inside of the gas damper and positions the structure at a target position while imparting rigidity to the gas damper in a supporting direction for supporting the structure. Method.   Rigidity is given to the target position until the structure exceeds the target position, and rigidity is given to return to the target position when the structure exceeds the target position. The method of controlling a vibration isolator according to claim 1.   The method for controlling a vibration isolator according to claim 1 or 2, wherein the rigidity is given according to a difference between a position of the structure and the target position.   The method for controlling a vibration isolator according to any one of claims 1 to 3, wherein the imparting of the rigidity is performed by an actuator different from the gas damper.   The method of controlling a vibration isolator according to any one of claims 1 to 3, wherein the rigidity is imparted by controlling an amount of gas inside the gas damper.   The method for controlling a vibration isolator according to any one of claims 1 to 5, wherein the imparted rigidity is removed after the structure is positioned at the target position. In an exposure method for exposing a pattern to a substrate by a system that is anti-vibrated by a vibration isolator,
An exposure method using the method for controlling an image stabilizer according to claim 1 as the method for controlling the image stabilizer. The system includes at least one of a mask stage that holds a mask on which the pattern is formed, a projection optical system that projects the pattern onto the substrate, and a substrate stage that holds the substrate. The exposure method according to claim 7.

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