JP2016092366A - Optical device, projection optical system, exposure device, and manufacturing method of article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device advantageous for effectively performing deformation of a reflection surface of a mirror, and correction of a position and posture of the mirror.SOLUTION: An optical device for deforming a reflection surface of a mirror comprises: a base plate; a plurality of actuators that are arranged between the base plate and the mirror, and apply a force to a plurality of positions of the mirror; a detection part that detects an amount of deviation of a position and posture of the mirror from a reference state; and a control part that controls each of the plurality of actuators. The control part determines a shape difference between a shape of the reflection surface in the reference state and a target shape, and determines a composite amount of deviation by composing the amount of deviation detected by the detection part with the shape difference. The control part decides a command value for causing the plurality of actuators to generate the force to be applied to each of the plurality of positions of the mirror, based on information indicating an amount by which the reflection surface deforms when each of the actuators is driven in a unit amount and the composite amount of deviation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical device that deforms a reflecting surface of a mirror, a projection optical system using the optical device, an exposure device, and an article manufacturing method.

  In order to improve the resolution of an exposure apparatus used for manufacturing a semiconductor device or the like, it is required to correct the optical aberration of the projection optical system in the exposure apparatus. Patent Documents 1 and 2 propose an optical device that corrects optical aberrations of a projection optical system by deforming a reflecting surface of a mirror included in the projection optical system.

  In an optical device, the position and posture of the mirror may deviate from the reference state over time due to aging or thermal deformation. For this reason, in the optical device, it is preferable to correct the position and orientation of the mirror in addition to deforming the reflecting surface of the mirror so that the optical aberration of the projection optical system is corrected. In the optical device described in Patent Document 1, in addition to the actuator for deforming the reflecting surface of the mirror, an actuator for correcting the position and orientation of the mirror by applying a force to the base plate that supports the mirror is provided. Yes. In the optical device described in Patent Document 2, both the deformation of the reflecting surface of the mirror and the correction of the mirror position and orientation are performed by controlling a plurality of actuators arranged between the mirror and the base plate.

Special table 2007-523485 gazette Japanese Patent No. 4817702

  Since the optical device described in Patent Document 1 includes an actuator for driving the base plate in addition to the actuator for deforming the reflecting surface of the mirror, the size of the device can be increased and the device cost can be disadvantageous.

  The optical device described in Patent Document 2 separately determines the force generated by each actuator to deform the reflecting surface of the mirror and the force generated by each actuator to correct the position and orientation of the mirror. To do. Then, the determined two forces are added for each actuator to obtain a command value for driving each actuator, a simulation based on the obtained command value is performed, and a command value is sent to each actuator based on the simulation result. For example, it is determined whether an error in the position and orientation of the mirror and a shape error in the simulation result are within allowable values. When these errors are within the allowable values, the command value is sent to each actuator, and when the errors are not within the allowable value, the simulation in which the distribution ratio to each actuator is changed is repeated. In changing the distribution ratio to each actuator, optimization control using a genetic algorithm is performed. However, in order to reduce the calculation load for obtaining the command value of each actuator, it is preferable to reduce the number of steps for determining the force generated by each actuator.

  Accordingly, an object of the present invention is to provide an optical device that is advantageous for efficiently performing the deformation of the reflecting surface of the mirror and the correction of the position and orientation of the mirror.

  In order to achieve the above object, an optical device according to one aspect of the present invention is an optical device that deforms a reflecting surface of a mirror, and is disposed between a base plate, the base plate, and the mirror. A plurality of actuators for applying a force to each of a plurality of locations; a detection unit for detecting a deviation amount of the position and orientation of the mirror from a reference state; and a control unit for controlling each of the plurality of actuators. The unit obtains a shape difference between the shape of the reflecting surface and the target shape in the reference state, obtains a composite deviation amount by combining the deviation amount detected by the detection unit and the shape difference, and When each actuator is driven by a unit amount for a command value for generating each of the plurality of actuators with a force to be applied to each of the plurality of locations. Determined on the basis of the information and the synthesis shift amount indicating the amount of the reflection surface is deformed, characterized in that.

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

  ADVANTAGE OF THE INVENTION According to this invention, the optical apparatus advantageous in order to perform efficiently the deformation | transformation of the reflective surface of a mirror, and correction | amendment of a mirror's position and attitude | position can be provided, for example.

It is the schematic which shows the structure of the optical apparatus of 1st Embodiment. It is a figure which shows arrangement | positioning of the some sensor in a detection part. It is a figure which shows the mirror from which the position and attitude | position have shifted | deviated from the reference | standard state. It is the schematic which shows the structure of the optical apparatus of 2nd Embodiment. It is the schematic which shows the structural example of exposure apparatus.

  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 thru | or element, and the overlapping description is abbreviate | omitted.

<First Embodiment>
The optical device 10 according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a configuration of an optical device 10 according to the first embodiment. The optical device 10 of the first embodiment corrects optical aberrations of the projection optical system, magnification, distortion, and focus of the projection image by deforming the reflecting surface 1a of the mirror 1 included in the projection optical system of the exposure apparatus, for example. To do. The optical device 10 can include a mirror 1, a base plate 3, a detection unit 4, a plurality of actuators 5, and a control unit 8. The control unit 8 includes a CPU, a memory, and the like, and controls each of the plurality of actuators 5.

  The mirror 1 has a reflecting surface 1a that reflects light and a back surface 1b that is a surface opposite to the reflecting surface 1a, and a part of the mirror 1 including the center of the mirror 1 (hereinafter, center portion) is a fixing member. It is fixed to the base plate 3 through 2. The center part of the mirror 1 is fixed to the base plate 3 in this manner because the mirror 1 used in the projection optical system of the exposure apparatus is often not irradiated with the light at the center part of the mirror 1. This is because there is little need to deform. Here, in the first embodiment, the central portion of the mirror 1 is fixed to the base plate 3 by the fixing member 2, but any part of the mirror 1 may be fixed to the base plate 3 by the fixing member 2. In the case where a displacement actuator such as a piezoelectric element is used as each actuator 5 and the mirror 1 is supported by the base plate 3 by each actuator 5, the fixing member 2 may not be used. In the first embodiment, an example in which a circular flat mirror is used as the mirror 1 will be described. However, the present invention is not limited to this. For example, a spherical mirror or an aspherical mirror having a concave surface or a convex surface may be used as the mirror 1. Good.

  The plurality of actuators 5 are disposed between the mirror 1 and the base plate 3 and apply force to a plurality of locations on the mirror 1 (back surface 1b). As each actuator 5, for example, a non-contact type actuator including a mover 5 a and a stator 5 b that are not in contact with each other such as a voice coil meter (VCM) or a linear motor may be used. A displacement actuator may be used. When a non-contact type actuator such as a VCM is used as each actuator 5, one of the movable element 5 a and the stator 5 b in each actuator 5 is fixed to the back surface 1 b of the mirror 1 and the other is fixed to the base plate 3. In the example shown in FIG. 1, the mover 5 a (magnet) is fixed to the back surface 1 b of the mirror 1, and the stator 5 b (coil) is fixed to the base plate 3. Thereby, each actuator 5 can change the distance between the mirror 1 and the base plate 3 by applying a force to the back surface 1b of the mirror 1 by supplying a current to the coil of the stator 5b.

  In the optical apparatus, generally, the target shape of the reflecting surface of the mirror is determined so that the optical aberration of the projection optical system is corrected, that is, the wavefront aberration of the light reflected by the mirror is within an allowable range. Each actuator is controlled such that the reflecting surface of the mirror is deformed by the difference between the shape of the mirror and the target shape in the reference state (hereinafter referred to as shape difference). However, in the optical apparatus, the position and posture of the mirror may deviate from the reference state over time due to aging or thermal deformation. In this case, even if each actuator is controlled so that the reflection surface of the mirror is deformed by the shape difference, it may be difficult to make the shape of the reflection surface of the mirror a target shape. That is, in this case, the shape of the deformed reflecting surface is deviated from the target shape by the amount of deviation of the mirror position and posture from the reference shape. Therefore, in the optical device 10 of the first embodiment, the detection unit 4 that detects the amount of deviation of the position and orientation of the mirror 1 from the reference state is provided. Then, the control unit 8 determines a command value for driving each actuator 5 in consideration of the deviation amount detected by the detection unit 4. Here, the shape of the mirror 1 in the reference state means, for example, the shape of the mirror 1 in a state in which each actuator 5 is turned off, that is, in a state in which no current is supplied to the coil of the stator 5b of each actuator 5. . Further, the position of the mirror is, for example, the position of the representative point on the mirror, and the attitude of the mirror is, for example, the tilt of the mirror. The mirror position and orientation in the reference state refer to the reference position and orientation of the mirror.

  Below, the structure of the detection part 4 and the method by which the control part 8 determines the command value of each actuator 5 are demonstrated. First, the configuration of the detection unit 4 will be described. The detection unit 4 detects the amount of deviation of the position and orientation of the mirror 1 from the reference state by measuring the displacement of each of a plurality of locations located in the peripheral part of the reflection surface 1 a of the mirror 1. For example, the detection unit 4 includes a plurality of sensors 4a and a processing unit 4b as shown in FIG. In the detection unit 4 of the first embodiment, three sensors 4a are used and can be arranged as shown in FIG. 2, for example. FIG. 2 is a diagram illustrating an arrangement of a plurality of sensors 4 a in the detection unit 4. Each of the plurality of sensors 4a measures a displacement (for example, displacement in the X direction, Y direction, and Z direction) from a reference state (reference position) of one place in the mirror 1. As each sensor, for example, a capacitance sensor, an eddy current displacement sensor, a laser displacement meter, a strain gauge, or the like can be used. Further, the processing unit 4b obtains the amount of deviation of the position and orientation of the mirror 1 from the reference state using the measurement results obtained by the sensors 4a. The shift amount can include, for example, a shift amount and a tilt amount from the reference state of the mirror 1. Here, the detection part 4 of 1st Embodiment measures each location in the reflective surface 1a of the mirror 1 with each sensor 4a, and the deviation | shift amount from the reference | standard state of the position and attitude | position of the mirror 1 using the measurement result However, it is not limited to that. For example, a sensor that measures the position and orientation of the base plate 3 may be included, and the amount of deviation may be obtained using a measurement result by the sensor.

  Next, a method in which the control unit 8 determines a command value for each actuator 5 will be described. The control unit 8 can include, for example, a first calculation unit 8a, a second calculation unit 8b, a determination unit 8c, a storage unit 8d, and a driver 8e. The first computing unit 8a acquires information representing the wavefront aberration (optical aberration of the projection optical system) of the light reflected by the reflecting surface 1a of the mirror 1, and is reflected by the reflecting surface 1a based on the acquired information. The target shape of the reflecting surface 1a of the mirror 1 is determined so that the wavefront aberration of light falls within the allowable range. The second calculation unit 8b obtains a shape difference between the shape of the reflecting surface 1a of the mirror 1 in the reference state and the target shape, and combines the deviation amount detected by the detection unit 4 and the shape difference to obtain a combined deviation amount. Ask. For example, the second calculation unit 8b can obtain the difference between the shift amount detected by the detection unit 4 and the shape difference as a combined shift amount.

  The determining unit 8c determines the force that each actuator 5 should apply to a plurality of locations of the mirror 1 so that the reflecting surface 1a is deformed by the combined deviation amount according to the combined deviation amount obtained by the second arithmetic unit 8b. Then, the determination unit 8c determines a command value to be generated by each actuator 5 based on the force that each actuator 5 should apply to a plurality of locations of the mirror 1 respectively. For example, the storage unit 8d stores information (sensitivity matrix) indicating the amount of deformation of the reflecting surface 1a of the mirror 1 when each actuator is driven by a unit amount. The determination unit 8c can determine the command value of each actuator 5 based on the information stored in the storage unit 8d and the composite deviation amount obtained by the second calculation unit 8b. The driver 8 e is, for example, a current driver that supplies a current for driving each actuator 5 to each actuator 5. The driver 8e supplies a current to the coil of the stator 5b of each actuator 5 according to the command value of each actuator 5 supplied from the determination unit 8c.

  Here, a method of obtaining the composite deviation amount by the second calculation unit 8b will be described with reference to FIG. 3A and 3B are diagrams showing the mirror 1 whose position and orientation are deviated from the reference state. FIG. 3A is a view of the mirror 1 viewed from the X direction, and FIG. 3B is a view of the mirror 1 viewed from the Z direction. FIG. 3C is a view of the mirror 1 viewed from the Y direction. In FIG. 3, the solid line indicates the mirror 1 in the reference state, and the broken line indicates the mirror 1 whose position and orientation are deviated from the reference state. Further, the coordinates of a plurality of locations in the mirror 1 having the target shape are xi, yi, zi (i = 1, 2,... N), and the coordinates of the plurality of locations in the mirror 1 in the reference state are Xi, Yi, Zi. . Of the amount of deviation of the position and orientation of the mirror 1 from the reference state, the translation shift amount is Sx, Sy, Sz, and the tilt amount is θx, θy. The deviation amount can be detected by the detection unit 4. At this time, the second calculation unit 8b determines the shape difference (Xci, Yci, Zci) between the shape of the mirror 1 and the target shape in the reference state as Xci = xi-Xi, Yci = yi-Yi, Zci = zi-Zi. Can be obtained. Then, the second calculation unit can obtain the composite deviation amount (dxi, dyi, dzi) by dxi = Xci−Sx, dyi = Yci−Sy, dzi = Zci− (Sz + xi × θy + yi × θx).

  As described above, the optical device 10 according to the first embodiment obtains the combined deviation amount by combining the shape difference and the deviation amount, and then sets the command value of each actuator 5 so that the reflecting surface 1a is deformed by the synthesized deviation amount. decide. As described above, in order to reduce the calculation load for obtaining the command value of each actuator 5, it is preferable to reduce the number of steps for determining the force generated in each actuator 5. In the optical device 10 of the first embodiment, since only one distribution process is required, the deformation of the reflecting surface 1a of the mirror 1 and the correction of the position and orientation of the mirror 1 can be performed efficiently. Here, in the optical device 10 according to the first embodiment, the example in which the detection unit 4 includes the processing unit 4b that obtains the shift amount using the measurement result of each sensor 4a has been described. However, the present invention is not limited to this. The unit 8 may include the processing unit 4b.

Second Embodiment
The optical device 20 according to the second embodiment will be described with reference to FIG. FIG. 4 is a schematic diagram illustrating a configuration of the optical device 20 according to the second embodiment. The optical device of the second embodiment differs from the optical device of the first embodiment in the configuration of the detection unit 4.

  The detection unit 4 of the second embodiment obtains a deviation amount using a measuring instrument 4c such as a laser interferometer or a Shack-Hartmann sensor that measures the shape of the entire reflecting surface 1a of the mirror 1, and a measurement result by the measuring instrument 4c. And a processing unit 4b. The processing unit 4b fits the shape data of the entire reflecting surface 1a measured by the measuring instrument 4c with a Zernike polynomial, and acquires the Zernike coefficient of each term. Of the Zernike coefficients, the terms Z1, Z2 and Z3 represent the amount of shift (shift amount, tilt amount) of the position and orientation of the mirror 1 from the reference state, and from the Z4 term onwards, the shape of the reflecting surface 1a of the mirror 1 is obtained. Represents.

  At this time, in the control unit 8, the shape of the reflecting surface 1a of the mirror 1 in the reference state and the target shape of the reflecting surface 1a are each expressed by a Zernike coefficient (Zj, j = 1 to m). For example, when determining the target shape of the reflecting surface 1a, the first calculation unit a represents the target shape in the form of Zernike coefficients (Zj, j = 1 to m). The second calculation unit 8a obtains a shape difference between the shape of the reflecting surface 1a and the target shape in the reference state, each expressed in the form of a Zernike coefficient. Then, the second calculation unit 8a obtains a combined deviation amount by combining the deviation amount (Z1, Term Z2, and Z3 terms of the Zernike coefficient) obtained by the processing unit 4b and the shape difference. The processes of the determination unit 8c and the driver 8e are the same as those of the optical device 10 of the first embodiment. In addition, since the shape of the mirror 1 can be measured in this embodiment, the shape of the target shape is obtained by using the shape of the mirror 1 obtained by measurement by the measuring instrument 4c instead of the shape of the mirror 1 in the reference state. The difference may be obtained. Here, in the second embodiment, the method using the Zernike coefficient has been described. However, the method is not limited to this, and another method such as a method of fitting a surface shape using a Fourier series may be used.

<Embodiment of exposure apparatus>
The exposure apparatus of this embodiment will be described with reference to FIG. The exposure apparatus 50 of this embodiment includes an illumination optical system IL, a projection optical system PO, a mask stage MS that can move while holding a mask 55, and a substrate stage WS that can move while holding a substrate 56. sell. In addition, the exposure apparatus 50 can include a control unit 51 that controls processing for exposing the substrate 56.

  Light emitted from a light source (not shown) included in the illumination optical system IL forms, for example, an arc-shaped illumination region that is long in the Y direction on the mask 55 by a slit (not shown) included in the illumination optical system IL. can do. The mask 55 and the substrate 56 are respectively held by a mask stage MS and a 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. Be placed. The projection optical system PO has a predetermined projection magnification (for example, 1/2 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 direction in FIG. 5) 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 can be configured to include a plane mirror 52, a concave mirror 53, and a convex mirror 54, as shown in FIG. The exposure light emitted from the illumination optical system IL and transmitted through the mask 55 has its optical path bent by the first surface 52 a of the plane mirror 52 and is incident on the first surface 53 a of the concave mirror 53. The exposure 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 exposure light reflected by the second surface 53b of the concave mirror 53 is bent on the optical path by the second surface 52b of the plane mirror 52 and forms an image on the substrate. In the projection optical system PO configured in this way, the surface of the convex mirror 54 becomes an optical pupil.

  In the configuration of the exposure apparatus 50 described above, the optical apparatus according to the above-described embodiment can be used as an apparatus that deforms the reflecting surface of the concave mirror 53 as the mirror 1, for example. By using the optical apparatus according to the above-described embodiment for the exposure apparatus 50, the reflecting surfaces (the first surface 53a and the second surface 53b) of the concave mirror 53 can be deformed at high speed and with high accuracy. Optical aberrations can be corrected with high accuracy in real time. Here, the control unit 51 in the exposure apparatus 50 may be configured to include a control unit 8 for controlling the actuator 5 in the optical apparatus according to the above-described embodiment. When the optical device according to the above-described embodiment is used as a device that deforms the reflecting surface of the concave mirror 53, the X direction, the Y direction, and the Z direction in FIG. 5 are the −Z direction and the Y direction in FIGS. And X direction, respectively.

<Embodiment of Method for Manufacturing Article>
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 for manufacturing an article according to the present embodiment, a latent image pattern is formed on the photosensitive agent applied to the substrate using the above-described exposure apparatus (a 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 preferred 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.

1: mirror, 3: base plate, 4: detection unit, 5: actuator, 8: control unit, 10: optical device

Claims (10)

An optical device for deforming a reflecting surface of a mirror,
A base plate;
A plurality of actuators disposed between the base plate and the mirror, each applying force to a plurality of locations of the mirror;
A detecting unit for detecting a deviation amount from a reference state of the position and orientation of the mirror;
A control unit for controlling each of the plurality of actuators;
Including
The control unit obtains a combined deviation amount by synthesizing a shape difference between the shape of the reflecting surface and the target shape in the reference state and the deviation amount detected by the detection unit, A command value for generating a force to be applied to each of the plurality of actuators is based on information indicating the amount of deformation of the reflecting surface when each actuator is driven by a unit amount and the composite deviation amount. An optical device characterized by determining.   The optical device according to claim 1, wherein the detection unit detects the shift amount by measuring a displacement of each of a plurality of locations on the reflection surface.   The optical device according to claim 2, wherein each of the plurality of locations is located in a peripheral portion of the reflecting surface.   The optical device according to claim 1, wherein the detection unit obtains the shift amount using measurement results of the position and orientation of the base plate.   5. The optical according to claim 1, wherein the control unit obtains a difference between the shift amount detected by the detection unit and the shape difference as the combined shift amount. apparatus.   6. The optical according to claim 1, wherein the control unit determines the target shape so that a wavefront aberration of light reflected by the reflecting surface falls within an allowable range. apparatus. A fixing member for fixing a part of the mirror including the center of the mirror to the base plate;
The optical device according to claim 1, wherein each actuator includes a stator and a mover that do not contact each other. 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 8. Exposing the substrate using the exposure apparatus according to claim 9;
Developing the substrate exposed in the step;
A method for producing an article comprising:

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