JP2018066958A - Optical device, projection optical system, exposure apparatus and production method of article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device advantageous for suppressing vibrations in a rotation direction around the optical axis of a mirror as a rotation axis, and an exposure apparatus for exposing a substrate.SOLUTION: An optical device OA includes a base 4, a support part 2 disposed on the base 4 and supporting a mirror 1 at the center portion on the back surface of the mirror 1, and a control part D for applying force on a side face of the mirror 1 to suppress vibrations in a rotation direction around the optical axis of the mirror 1 as a rotation axis.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical apparatus, a projection optical system, an exposure apparatus, and an article manufacturing method.

  2. Description of the Related Art An optical system having a variable mirror that can correct optical aberration, focal position, field curvature, etc. by deforming a mirror (reflection surface thereof) into an arbitrary shape is generally known. In the astronomical field, when recognizing stars, the resolution of the image decreases due to atmospheric fluctuations, so the technology that reduces the effects of atmospheric fluctuations by measuring the wavefront at high speed and correcting it with a variable mirror. Exists. In addition, in an exposure apparatus used for manufacturing semiconductor devices, there is a technique for correcting aberration by using a mirror included in an optical system as a variable mirror in order to cope with a change in aberration due to a temperature change during exposure. .

  Some variable mirrors with a large aperture (for example, 200 mm or more) form a reflecting surface of an arbitrary shape by driving the back surface of the mirror in the out-of-plane direction of the reflecting surface by an actuator. There are 100 or more actuators May be arranged. With regard to such a technique, a method of fastening the back surface of the mirror and the mover of the actuator, a method of arranging (joining) a magnet on the back surface of the mirror, and a method of arranging a coil at a position having a minute interval from the magnet, etc. Has been proposed.

  In the former method, when a piezo element is used as an actuator, it is necessary to assemble the mirror in a state where a large number of actuators are aligned when mechanically fastening the back surface of the mirror and the mover of the actuator. In this case, since it is difficult to manage the position of each actuator, it is very difficult to assemble the actuator without deforming the mirror.

  In the latter method, since it is not necessary to fasten the back surface of the mirror and a large number of actuators, the risk of breaking the initial shape of the mirror is reduced. Although it is possible to realize a variable mirror by arranging a coil on the back surface of the mirror and arranging the magnet on the fixed side, in this case, it is necessary to mount electrical wiring on the mirror that forms an arbitrary shape, Not realistic.

  Regarding the support (fixation) of the mirror, a configuration has been proposed in which the center of the back surface of the mirror is one (see Patent Document 1). By supporting the mirror at one central position on the back surface of the mirror, over-constraining of the mirror can be avoided and the mirror can be supported without being distorted.

  Therefore, as a configuration for realizing the variable mirror, a configuration in which the mirror is supported at one center of the back surface of the mirror, a magnet is disposed on the back surface of the mirror, and a coil is disposed at a position facing the magnet is preferable. . The mirror should be fixed by adhesion. This is because, since the mirror is supported at one place (small region), when mechanically fastened, a force is locally applied to the mirror by the fastening force, and the shape of the mirror is deformed. On the other hand, in the case of adhesion, even if the back surface of the mirror (the shape) and the support surface of the support member (the shape) do not completely match, the adhesive is interposed, so the shape of the mirror is maintained. It can be attached to the support member as it is.

Japanese Patent No. 4817702

  However, the configuration of the variable mirror described above has a drawback in that the mirror is easily swayed by disturbance such as floor vibration because the rigidity between the back surface of the mirror and the support member is low. In particular, there is a problem that vibration in the rotational direction around the optical axis of the mirror occurs.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an optical device that is advantageous for suppressing vibration in the rotation direction with the optical axis of the mirror as the rotation axis.

  In order to achieve the above object, an optical device according to one aspect of the present invention includes a base, a support provided on the base and supporting a mirror at the center of the back surface of the mirror, and a side surface of the mirror. And a suppression unit that applies a force to suppress vibration in the rotation direction about the optical axis of the mirror as a rotation axis.

  Further objects and other aspects of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, for example, it is possible to provide an optical device that is advantageous in suppressing vibration in the rotational direction with the optical axis of the mirror as the rotation axis.

It is the schematic which shows the structure of the optical apparatus in 1st Embodiment. It is the schematic which shows the structure of the suppression part in 1st Embodiment. It is the schematic which shows the structure of the suppression part in 2nd Embodiment. It is the schematic which shows the structure of the control part in 3rd Embodiment. It is the schematic which shows the structure of the optical apparatus in 4th Embodiment. It is the schematic which shows the structure of the control part in 5th Embodiment. It is the schematic which shows the structure of the exposure apparatus as 1 side surface of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

<First Embodiment>
FIG. 1A and FIG. 1B are schematic views showing the configuration of the optical device OA in the first embodiment. FIG. 1A shows a top view of the optical device OA, and FIG. 1B shows a cross-sectional (front) view of the optical device OA. The optical device OA is a variable mirror device that deforms the mirror 1, specifically, deforms the reflecting surface 1a of the mirror 1 into a desired shape. The optical device OA includes a mirror 1, a support portion 2, an adhesive layer 3, a base 4, a voice coil motor VCM, and a suppression portion D.

  The mirror 1 is a circular thin mirror. The support 2 is provided on the base 4 and supports the mirror 1 at the center of the mirror 1. The adhesive layer 3 is a layer containing an adhesive that bonds (fastens) the mirror 1 and the support portion 2. In this embodiment, the support part 2 is inserted in the hole 1c formed in the center part of the mirror 1, and is fixed with an adhesive. Therefore, a thin adhesive layer 3 is interposed between the hole 1 c of the mirror 1 and the support portion 2. The support portion 2 is fixed to a base 4 that supports the entire apparatus.

  A plurality of magnets 5 are disposed (attached) to the back surface (the surface opposite to the reflecting surface 1a) 1b of the mirror 1. A plurality of coils 6 are arranged (attached) to the base 4 so as to face each of the plurality of magnets 5 arranged on the back surface 1 b of the mirror 1. A Lorentz force is generated by passing a current through the coil 6. One voice coil motor VCM is composed of a pair of one magnet 5 and a corresponding coil 6. Since the magnet 5 and the coil 6 are not in contact with each other, the mirror 1 is supported only by the support portion 2. In such a configuration, since the mirror 1 is not over-constrained in the initial state where the voice coil motor VCM does not generate thrust, the risk of breaking the initial shape of the mirror 1 can be reduced.

  In the present embodiment, bonding is adopted for fastening the mirror 1 and the support portion 2. When the mirror 1 and the support portion 2 are mechanically fastened, they are fixed by sandwiching a narrow region at the center of the mirror 1. Therefore, a minute shape error of the contact surface between the mirror 1 and the support portion 2 is enlarged toward the outer peripheral portion of the mirror 1. In fastening by bonding, since the adhesive layer 3 absorbs the shape error between the mirror 1 and the support portion 2, such a problem does not occur.

  However, bonding has the disadvantage of low rigidity. Since the elastic modulus of the adhesive is generally smaller than the elastic modulus of metal or glass, the mirror 1 supported by the support portion 2 at one point in the central portion is likely to shake. The vibration mode in the rotational direction around the optical axis of the mirror 1 has a lower resonance frequency than when the mirror 1 is rigidly fixed. When the mirror 1 vibrates in the rotational direction around the optical axis, even if the voice coil motor VCM is driven and the reflecting surface 1a of the mirror 1 is deformed to a desired shape, the optical performance is deteriorated because the mirror 1 is displaced in the rotational direction. End up. A vibration mode in which the mirror 1 is tilted, that is, a so-called tilt mode also occurs. In this direction, a number of voice coil motors VCM for deforming the shape of the reflecting surface 1a of the mirror 1 are arranged. Control can be performed. On the other hand, the vibration in the rotation direction around the optical axis of the mirror 1, that is, the vibration in the rotation direction around the optical axis of the mirror 1 cannot be handled by the voice coil motor VCM.

  Therefore, in the present embodiment, as shown in FIG. 1B, a function of applying a force to the side surface of the mirror 1 to suppress vibration in the rotational direction with the optical axis of the mirror 1 as a rotation axis, that is, a damping function is provided. The suppression part D which has is provided. In physics, damping is defined as generating a force in the direction opposite to the direction of vibration according to the speed of vibration, but here it is defined as suppressing vibration. Furthermore, when vibration is generated due to the same disturbance, reducing the amplitude of vibration is defined as damping.

  FIG. 2 is a schematic diagram illustrating a configuration of the suppressing unit D in the first embodiment. In FIG. 2, the suppression part D seen from the Y-axis direction is shown. In the present embodiment, the suppression unit D includes a first holding unit 101, a second holding unit 105, a measuring unit 111 including the sensor target 102 and the sensor 106, and an actuator 113 including the damping magnet 103 and the damping coil 104. Including. In addition, the suppression unit D includes an amplifier 107, a control unit 108, and a driver 109.

  The first holding unit 101 is provided (fixed) on the side surface 1 d of the mirror 1. In the present embodiment, the first holding unit 101 holds the damping magnet 103 and the sensor target 102. The second holding unit 105 is provided (fixed) on the base 4. The second holding unit 105 holds the damping coil 104 so as to face the damping magnet 103 held by the first holding unit 101. The second holding unit 105 holds the sensor 106 so as to face the sensor target 102 held by the first holding unit 101.

  The measuring unit 111 has a function of measuring a rotational speed (rotational speed around the optical axis) with the optical axis of the mirror 1 as a rotational axis. The sensor 106 includes a displacement sensor such as a capacitance sensor, for example, and always detects a distance to the sensor target 102 (a distance between the sensor target 102 and the sensor 106). By differentiating the distance (displacement) detected by the sensor 106 with respect to time, the rotational speed around the optical axis of the mirror 1 can be measured.

  The actuator 113 has a function of applying a rotational force about the optical axis of the mirror 1 to the side surface 1 d of the mirror 1. The actuator 113 is a voice coil motor that uses Lorentz force, and can generate a force with the damping magnet 103 by passing a current through the damping coil 104. In the actuator 113, it is possible to obtain a damping effect by generating a thrust proportional to the rotational speed measured by the measuring unit 111.

  The control unit 108 controls the rotational force that the actuator 113 applies to the side surface 1 d of the mirror 1 based on the measurement result of the measurement unit 111. Specifically, the output (displacement) from the sensor 106 is converted into an output such as a voltage by the amplifier 107 and sent to the control unit 108. The control unit 108 differentiates the displacement with time and converts it into a rotational speed, and multiplies the coefficient according to the rotational speed to obtain a thrust to be generated by the actuator 113. Then, the control unit 108 outputs a command value corresponding to the thrust to be generated by the actuator 113 to the driver 109. The driver 109 generates a current corresponding to the command value from the control unit 108 and supplies it to the damping coil 104. Thereby, the suppression part D can exhibit the damping effect, and can attenuate the vibration of the rotation direction which makes the optical axis of the mirror 1 a rotating shaft. Therefore, the vibration in the rotation direction with the optical axis of the mirror 1 as the rotation axis is reduced, and the deterioration of the optical performance can be suppressed.

  In the present embodiment, in the suppression portion D, the damping magnet 103 (movable portion) and the damping coil 104 (fixed portion) are not mechanically fastened (the actuator 113 is not in contact). Type actuator). Therefore, the control (surface shape control) for deforming the reflecting surface 1a of the mirror 1 into a desired shape is not affected.

  In this embodiment, in order to measure the rotational speed around the optical axis of the mirror 1, the displacement is detected using a displacement sensor as the sensor 106, and the displacement is differentiated with respect to time. However, the present invention is not limited to this. It is not something. For example, an acceleration sensor may be arranged around the mirror 1 and the rotation speed around the optical axis of the mirror 1 may be measured by integrating the acceleration detected by the acceleration sensor.

Second Embodiment
FIG. 3 is a schematic diagram illustrating a configuration of the suppressing unit D in the second embodiment. In FIG. 3, the suppression part D seen from the Y-axis direction is shown. In the present embodiment, the suppressing portion D includes a convex portion 201, a guide 202, a damper 204, a guide support portion 203, and a damper 204.

  The convex portion 201 is rigidly fastened to the side surface 1 d of the mirror 1. The guide 202 is a guide part that guides the mirror 1 in the horizontal direction by sandwiching both side surfaces of the convex part 201 with a ball, that is, guides the mirror 1 in the horizontal direction, and transmits a force in the horizontal direction. It has a structure that does not transmit force in the vertical direction. The damper 204 is provided (attached) to the base 4. The damper 204 is composed of an oil damper, and includes a cylinder 204a fixed to the base 4 and a piston 204b movable in the horizontal direction. The guide support portion 203 is fastened to the guide 202 and the piston 204b. The guide support portion 203 connects the guide 202 and the piston 204b, and functions as a transmission portion that transmits the force generated by the movement of the piston 204b in the horizontal direction to the guide 202.

  In the suppression part D in 2nd Embodiment, when the mirror 1 vibrates in the rotation direction which makes an optical axis a rotating shaft, the damper 204 generate | occur | produces reaction force according to the speed of this vibration. The reaction force generated by the damper 204 is transmitted to the guide 202 via the guide support portion 203 and attenuates vibration in the rotational direction with the optical axis of the mirror 1 as the rotation axis. Therefore, the vibration in the rotation direction with the optical axis of the mirror 1 as the rotation axis is reduced, and the deterioration of the optical performance can be suppressed.

<Third Embodiment>
FIG. 4A and FIG. 4B are schematic views illustrating the configuration of the suppressing unit D in the third embodiment. 4A shows the suppression unit D viewed from the Z-axis direction, and FIG. 4B illustrates the suppression unit D viewed from the Y-axis direction. In the present embodiment, the suppressing portion D includes a convex portion 301, a damper 304, a damper support portion 303, and a joint 302.

  The convex portion 301 is fixed to the side surface 1 d of the mirror 1. The damper 304 is composed of an oil damper, and includes a cylinder 304a and a piston 304b that is movable in the horizontal direction. The damper support portion 303 is provided on the base 4. The damper support portion 303 holds the damper 304 so that the damper 304 is disposed at the same height as the mirror 1. The joint 302 connects the convex portion 301 and the piston 304b. The joint 302 includes universal joints at two locations, and the universal joints are arranged at the same height as the mirror 1. As described above, even when the mirror 1 is driven along the optical axis direction, if the driving amount is very small, the force in the rotation direction with the optical axis of the mirror 1 as the rotation axis is not applied to the mirror 1. It has become. Therefore, the joint 302 transmits only the force in the rotational direction with the optical axis of the mirror 1 as the rotational axis between the mirror 1 and the damper 304.

  In the suppression part D in 3rd Embodiment, when the mirror 1 vibrates in the rotation direction which makes an optical axis a rotating shaft, the damper 304 will generate reaction force according to the speed of this vibration. The reaction force generated by the damper 304 is transmitted to the mirror 1 (the side surface 1d thereof) via the joint 302, and attenuates the vibration in the rotation direction with the optical axis of the mirror 1 as the rotation axis. Therefore, the vibration in the rotation direction with the optical axis of the mirror 1 as the rotation axis is reduced, and the deterioration of the optical performance can be suppressed.

<Fourth embodiment>
FIG. 5 is a schematic diagram showing the configuration of the optical device OA in the fourth embodiment. FIG. 5 shows a cross-sectional (front) view of the optical device OA. In this embodiment, the optical device OA is a mirror 1 having a concave reflecting surface 1a, that is, a variable mirror device that deforms a concave mirror, and basically has the same configuration as that of the first embodiment. . However, in FIG. 5, illustration of the voice coil motor VCM for deforming the shape of the reflecting surface 1 a of the mirror 1, that is, the magnet 5 and the coil 6 is omitted.

  The suppression unit D includes the first holding unit 101, the second holding unit 105, the measurement unit 111, and the actuator 113, as in the first embodiment, but the measurement unit 111 is not shown. In the present embodiment, a position (height) at which a force in the rotational direction (damping force) about the optical axis of the mirror 1 is applied to the mirror 1 is defined. Specifically, each of the first holding unit 101 and the second holding unit 105 includes a damping magnet 103 and a damping coil so that the actuator 113 is disposed at the same height as the center of gravity of the shape of the mirror 1. 104 is held. Thereby, when vibration in the rotation direction with the optical axis of the mirror 1 as the rotation axis occurs, the position of the force applied from the actuator 113 to the mirror 1 to suppress such vibration is the center of gravity position of the shape of the mirror 1. Since they coincide with each other, vibration in only the rotation direction can be suppressed. On the other hand, when the position of the force applied from the actuator 113 to the mirror 1 does not coincide with the position of the center of gravity of the shape of the mirror 1, the force is applied in the direction of bending the mirror 1. Will reduce the accuracy. Therefore, in this embodiment, the actuator 113 is arranged at the same height as the position of the center of gravity of the shape of the mirror 1, thereby suppressing a decrease in the accuracy of the surface shape control of the mirror 1 and a more accurate variable mirror device. Realized.

<Fifth Embodiment>
FIG. 6 is a schematic diagram illustrating a configuration of the suppressing unit D in the fifth embodiment. In FIG. 6, the suppression part D seen from the Y-axis direction is shown. In the present embodiment, the suppression unit D basically has the same configuration as that of the second embodiment, but includes a fixing unit 504 instead of the damper 204.

  The guide support part 203 is fastened to the guide 202 and the fixed part 504. The fixing portion 504 has a function of fixing the guide support portion 203 to the base 4 and adjusting the position and angle of the guide support portion 203. For example, when the posture of the guide support portion 203 is tilted and the surface guided by the guide 202 is tilted from the optical axis direction, it becomes a resistance when the mirror 1 is deformed, and the force for deforming the mirror 1 increases. End up. Further, when the position of the guide support portion 203 is shifted, a force in the rotation direction with the optical axis of the mirror 1 as a rotation axis is always applied, and the force for deforming the mirror 1 is increased by the friction of the guide 202. Resulting in. Therefore, by adjusting the position and orientation of the guide support portion 203 with the fixing portion 504, the direction in which the guide 202 guides is matched with the optical axis direction.

  In the suppression unit D in the fifth embodiment, since the rigidity in the rotation direction with the optical axis of the mirror 1 as the rotation axis is improved, when vibration due to disturbance occurs in the mirror 1, such vibration can be suppressed. . However, since the rigidity in the direction of deforming the mirror 1 is not changed, the force for deforming the mirror 1 does not increase.

  With reference to FIG. 7, an exposure apparatus 50 according to one aspect of the present invention will be described. The exposure apparatus 50 is a lithography apparatus that exposes the substrate 56. The exposure apparatus 50 includes an illumination optical system IL, a projection optical system PO, a mask stage MS that moves while holding a mask 55, and a substrate stage WS that moves while holding a substrate 56. The exposure apparatus 50 includes a control unit 51 that includes a CPU, a memory, and the like, and controls the entire exposure apparatus 50.

  Light from a light source (not shown) forms, for example, an arcuate illumination region that is long in the Y-axis direction on the mask through a slit (not shown) included in the illumination optical system IL. The mask 55 and the substrate 56 are respectively held by the mask stage MS and the substrate stage WS, and are optically conjugate positions (positions of the object plane and the image plane of the projection optical system PO) via the projection optical system PO. Has been placed. The projection optical system PO has a predetermined projection magnification (for example, ½ times), and projects the pattern formed on the mask 55 onto the substrate 56. Then, the mask stage MS and the substrate stage WS are scanned in a direction parallel to the object plane of the projection optical system PO (for example, the X-axis direction in FIG. 7) at a speed ratio corresponding to the projection magnification of the projection optical system PO. Thereby, the pattern formed on the mask 55 can be transferred to the substrate 56.

  The projection optical system PO includes, for example, a plane mirror 52, a concave mirror 53, and a convex mirror 54 as shown in FIG. The light emitted from the illumination optical system IL and passing through the mask 55 is reflected by the first surface 52 a of the flat mirror 52 and enters the first surface 53 a of the concave mirror 53. The light reflected by the first surface 53 a of the concave mirror 53 is reflected by the convex mirror 54 and enters the second surface 53 b of the concave mirror 53. The light reflected by the second surface 53b of the concave mirror 53 is reflected by the second surface 52b of the flat mirror 52 and forms an image on the substrate. In the projection optical system PO, the convex mirror 54 becomes an optical pupil.

  In the exposure apparatus 50, the optical apparatus OA in the above-described embodiment is used, for example, as a variable mirror apparatus that deforms the reflecting surface of the concave mirror 53 into an arbitrary shape (that is, the concave mirror 53 is the mirror 1). Thereby, the vibration of the rotation direction which makes the optical axis of the concave mirror 53 a rotating shaft is reduced, and the fall of optical performance can be suppressed. Here, the control unit 51 in the exposure apparatus 50 may be configured to include the control unit 108 in the optical device OA (the suppression unit D) in the first embodiment described above.

  The method for manufacturing an article according to an embodiment of the present invention is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure. In the method of manufacturing an article according to the present embodiment, a latent image pattern is formed on the photosensitive agent applied to the substrate using the exposure apparatus 50 (step of exposing the substrate), and the latent image pattern is formed in this step. Developing the substrate. Further, the manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

  As mentioned above, although preferable embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, in the above-described embodiment, the oil damper is described as an example of the damper that configures the suppressing unit having the damping function. However, the damper is not limited to the oil damper. For example, if it is a passive damper, the same effect can be acquired even with a damper using rubber or a damper using air.

OA: Optical device D: Suppression part 1: Mirror 2: Support part 3: Adhesive layer 4: Base 5: Magnet 6: Coil

Claims (9)

Base and
A support provided on the base and supporting the mirror at the center of the back surface of the mirror;
A suppressor that applies a force to a side surface of the mirror to suppress vibration in a rotation direction with the optical axis of the mirror as a rotation axis;
An optical device comprising: The suppressor is
An actuator that includes a magnet and a coil and applies a force in the rotational direction to a side surface of the mirror;
A first holding part that is provided on a side surface of the mirror and holds the magnet;
A second holding portion that is provided on the base and holds the coil so as to face the magnet held by the first holding portion;
A measuring unit for measuring the speed of the mirror in the rotation direction;
Based on the measurement result of the measurement unit, a control unit that controls the rotational force applied by the actuator to the side surface of the mirror;
The optical apparatus according to claim 1, comprising: The suppressor is
A convex portion provided on a side surface of the mirror;
A guide part for horizontally guiding the mirror with the convex part interposed therebetween;
A damper including a cylinder provided on the base and a piston movable in the horizontal direction;
A transmission unit for connecting the guide unit and the piston, and transmitting a force generated by movement of the piston to the guide unit;
The optical apparatus according to claim 1, comprising: The suppressor is
A convex portion provided on a side surface of the mirror;
A guide part for horizontally guiding the mirror with the convex part interposed therebetween;
A holding part fixed to the base and holding the guide part;
The optical apparatus according to claim 1, comprising: The suppressor is
A convex portion provided on a side surface of the mirror;
A damper including a cylinder and a horizontally movable piston;
A holding portion that is provided on the base and holds the damper so that the damper is disposed at the same height as the mirror;
A joint connecting the convex part and the piston;
The optical apparatus according to claim 1, comprising: The mirror is a concave mirror;
Each of the first holding part and the second holding part holds the magnet and the coil so that the actuator is disposed at the same height as the center of gravity of the shape of the mirror. The optical device according to claim 2. A projection optical system for projecting a mask pattern onto a substrate,
A projection optical system comprising the optical device according to claim 1. An exposure apparatus for exposing a substrate,
An exposure apparatus comprising the projection optical system according to claim 7. Exposing the substrate using the exposure apparatus according to claim 8;
Developing the exposed substrate;
A method for producing an article comprising:

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