TWI631430B - Optical device, projection optical system, exposure device, and article manufacturing method - Google Patents

Abstract

The present invention provides an optical device, a projection optical system, an exposure device, and an article manufacturing method. The invention reduces the temperature distribution generated on the mirror when the shape of the mirror is deformed. The optical device includes a mirror having a reflecting surface and a back surface opposite to the reflecting surface; a base plate; a fixing member fixed to a part of the back surface to fix the mirror on the base plate; and a plurality of actuators, A force is applied to the rear surface to change the shape of the reflective surface. Wherein, the plurality of actuators include: a plurality of first actuators respectively applying a force to a first region in the back surface, the first region surrounding the fixing portion of the mirror fixed by the fixing structure; and Each of the second actuators applies a force to a second region surrounding the first region in the back surface. The efficiency of the thrust generation of the first actuator is higher than the efficiency of the thrust generation of the second actuator.

Description

Optical device, projection optical system, exposure device, and article manufacturing method

The present invention relates to an optical device including a deformable mirror, a projection optical system, an exposure device, and an article manufacturing method.

An optical device including a deformable mirror for correcting wavefront errors and image distortion is particularly applied to a semiconductor exposure device, a liquid crystal exposure device, a astronomical telescope, or the like. In recent years, the requirements for the resolution in the exposure apparatus have become stricter, and therefore, the requirements for the exposure aberration have become stricter. Therefore, in order to correct exposure aberrations, a device configuration including a deformable mirror in an exposure device has been proposed. In addition, in the field of astronomy, in order to suppress the influence of air fluctuations on telescopes installed on the ground, deformable mirrors have also been used.

Japanese Patent No. 4777702 discloses an optical device provided with a plurality of actuators that hold a center portion of a deformable mirror and make an area outside the center portion of the mirror The surface shape is distorted. In addition, Japanese Patent Laid-Open No. 2015-70214 discloses a hybrid vehicle equipped with a high-rigidity actuator and a low-rigidity actuator. An optical device that raises the natural frequency of the mirror.

When the deformable mirror is held at the center, the rigidity of the area near the center of the mirror is higher than that of the peripheral area far from the center. Therefore, the area closer to the center portion of the mirror surface is more difficult to deform, and a large driving force is often required. The inventors of the present invention have found that if a plurality of voice coil motors (VCMs) having the same thrust constant are used as force actuators in order to change the surface shape of a mirror, the area near the center of the mirror and the peripheral area There is a large amount of heat generated between them. Since the central part of the mirror is fixed on the substrate, the VCM in the vicinity of the central part can output a larger force than the VCM in the peripheral area, and the amount of heat generated becomes larger.

The inventors of the present invention obtained the heat generation distributions in the central region and the peripheral region near the center of the mirror when a plurality of VCMs having the same thrust constant are equally provided. Figure 3 shows the results of the calorific value distribution. As shown in FIG. 3, the mirror is divided into a central region and a peripheral region in a concentric circle shape. If the area ratio of the central area to the surrounding area is divided into 3%: 97%, the heat generation amount in the central area having an area of 3% accounts for 60% of the total heat generation amount. In this case, the ratio of the calorific value per unit area between the central area and the peripheral area is 49: 1. If the area ratio between the central area and the surrounding area is divided into 8%: 92%, the calorific value in the central area with an area of 8% accounts for 67% of the total calorific value, and the heat per unit area between the central area and the surrounding area is heat The ratio of the amounts is 23: 1. If the central area and the surrounding area The area ratio is divided into 32%: 68%, then the calorific value in the central area of 32% accounts for 74% of the total calorific value, and the ratio of the calorific value per unit area between the central area and the surrounding area is 6: 1 . As described above, the amount of heat generated in the central region of the mirror dominates. As a result, it is found that a large temperature distribution occurs between the central region near the central portion of the mirror and the peripheral region, and thermal deformation of the mirror occurs.

The present invention provides an optical device which is advantageous in terms of reducing a temperature distribution generated on a mirror when the shape of the mirror is deformed.

In order to solve the above problems, the optical device of the present invention is characterized by comprising: a mirror having a reflecting surface and a back surface opposite to the reflecting surface; a base plate; and a fixing member fixed to a part of the back surface to fix the mirror. On the bottom plate; and a plurality of actuators, each applying a force to the back surface to change the shape of the reflecting surface, wherein the plurality of actuators include: a plurality of first actuators, respectively, into the back surface A force is applied to a first area of the first area, the first area surrounds the fixing portion of the mirror fixed by the fixed structure, and a plurality of second actuators are applied to the second area of the back surface surrounding the first area, respectively The thrust generation efficiency of the first actuator is higher than the thrust generation efficiency of the second actuator.

According to the present invention, it is possible to reduce the size of the mirror when the shape of the mirror is deformed. The resulting temperature distribution.

1‧‧‧mirror

1a‧‧‧ surface

1b‧‧‧ back

1b1‧‧‧ Zone 1

1b2‧‧‧Second Zone

2‧‧‧ fixed structure

3‧‧‧ floor

3b‧‧‧face

4‧‧‧first actuator

4a‧‧‧first magnet

4b‧‧‧first coil

5‧‧‧Second Actuator

5a‧‧‧Second magnet

5b‧‧‧Second coil

6‧‧‧Control Department

6a‧‧‧ Computing Department

6b‧‧‧Actuator driver

50‧‧‧ exposure device

51‧‧‧Control Department

52‧‧‧ flat mirror

53‧‧‧Concave mirror

54‧‧‧ convex mirror

55‧‧‧Mask

56‧‧‧ substrate

52a‧‧‧First side

52b‧‧‧Second Side

53a‧‧‧First side

53b‧‧‧Second Side

IL‧‧‧ Illumination Optical System

MS‧‧‧Mask

PO‧‧‧ Projection Optical System

WS‧‧‧ Substrate

FIG. 1 is a diagram showing an example of an optical device according to the present invention.

FIG. 2 is a diagram showing an operation principle of an optical device according to the present invention.

FIG. 3 is a diagram illustrating a problem to be solved by the present invention.

FIG. 4 is a diagram showing an example of an exposure apparatus according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like.

[Optical device]

FIG. 1 (b) illustrates an example of an optical device according to the present embodiment, and FIG. 1 (a) illustrates a rear surface of a mirror of the optical device. As shown in FIG. 1 (b), a part (for example, a central portion) of the deformable mirror 1 is fixed to the bottom plate 3 via a fixing member 2. The surface 1a of the mirror 1 is a reflecting surface. The back surface 1b of the mirror 1 on the side opposite to the reflection surface includes a central region (first region) 1b ₁ surrounding a central portion (holding region) fixed by the fixing member 2 and a peripheral region (second region) surrounding the central region 1b ₁ ) 1b ₂ . The central region 1b ₁ may be a central region having an area in which the amount of heat generation dominates, for example, 3% or less in the entire back surface 1b of the mirror 1. Alternatively, based on the data of the calorific value distribution shown in the column of the problem to be solved by the invention, the central area 1b ₁ may be a central area having an area of 8% or less of the entire back surface 1b of the mirror 1.

In the central region 1b ₁ of the mirror back surface 1b, a plurality of first magnets 4a are provided, for example, by adhesion, and in the peripheral region 1b ₂ , a plurality of second magnets 5a are provided, for example, by adhesion. The surface 3b of the bottom plate 3 facing the mirror back surface 1b includes a central region and a peripheral region corresponding to the central region 1b ₁ and the peripheral region 1b _{2 of the} mirror back surface 1b. A plurality of first coils 4b are arranged opposite to the plurality of first magnets 4a in the central region of the bottom plate 3, and a plurality of second coils are arranged opposite to the plurality of second magnets 5a in the peripheral region of the bottom plate 3. 5b. The first coil 4b and the second coil 5b are fixed to the surface 3b of the base plate 3, respectively. As shown in FIG. 1 (a), the plurality of first magnets 4 a and the plurality of second magnets 5 a can be arranged radially on the mirror back surface 1 b. In this case, similar to the plurality of first magnets 4a and the plurality of second magnets 5a, the plurality of first coils 4b and the plurality of second coils 5b are also arranged radially on the bottom plate surface 3b. However, the magnets and coils are not limited to being arranged radially. Other arrangements such as making the number of actuators per unit area the same may be used.

The first magnet 4a and the first coil 4b arranged in the central regions of the mirror back surface 1b and the bottom plate surface 3b constitute the first actuator 4. By causing a current to flow through the first coil 4b, a force proportional to the current is generated between the first magnet 4a and the first coil 4b, so that the shape of the central region of the mirror 1 can be changed. The second magnet 5 a and the second coil 5 b arranged in the peripheral areas of the mirror back surface 1 b and the bottom plate surface 3 b constitute a second actuator 5. By passing a current through the second coil 5b, a force proportional to the current is generated between the second magnet 5a and the second coil 5b, so that the peripheral area of the mirror 1 can be made. Shape change.

In this embodiment, a low-cost voice coil motor (VCM) using Lorentz force as one of the non-contact force actuators is used as the first actuator 4 and the second actuator 5. However, other force actuators other than VCM may be used as the first actuator 4 and the second actuator 5.

Assuming that the thrust constant (efficiency of thrust generation) of VCM is K _r , the resistance value of the coil is R, and the current flowing through the coil is I, the generated force F is expressed by formula (1). The calorific value P generated when the force F is generated is expressed by the formula (2).

F = K _f × I‧‧‧ (1)

P = I ² R = (F / K _f ) ² × R‧‧‧ (2)

According to formula (1), the larger the thrust constant K _f is, the smaller the current value I required to generate the same force F is. According to formula (2), the amount of heat generation is proportional to the square of the current and proportional to the resistance of the coil. Equation (2) means that to reduce the amount of heat generated by the VCM when the same force is generated, the most effective is to reduce the current value, and the second is to reduce the resistance of the coil. Therefore, by using an actuator having a large thrust constant, the necessary driving current can be reduced, and the amount of heat generation can be effectively reduced. Of course, reducing the resistance of the coil can also reduce the amount of heat generated by the actuator.

Therefore, in the present embodiment, as the first actuators 4 that deform the central region of the mirror 1, a larger thrust constant than the second actuators 5 that deform the peripheral region of the mirror 1 is used. Actuator. In the present embodiment, the plurality of first actuators 4 have the same thrust constant as each other, and the plurality of second actuators 5 have the thrust constants smaller than the thrust constant of the first actuator 4 and are the same as each other. However, the plurality of first actuators 4 and the plurality of first actuators 4 The two actuators 5 may be configured such that the smaller the distance between the arrangement position and the center portion of the mirror 1, the larger the thrust constant. In the present embodiment, a configuration for reducing the amount of heat generated in the central region of the mirror 1 has been proposed. However, a temperature control method for cooling the bottom plate 3 may be used in combination. Alternatively, a method of collectively cooling the central region of the bottom plate 3 may be used in combination.

Next, the operation principle of the optical device according to this embodiment will be described using FIG. 2. As shown in FIG. 2, the optical device includes a control unit 6 that controls a plurality of first actuators 4 and a plurality of second actuators 5. The control section 6 may include a calculation section 6 a and an actuator driver 6 b. In order to correct the error in the optical performance, the shape desired to be formed by the mirror 1 is sent to the arithmetic unit 6 a of the control unit 6 as a target shape. The computing unit 6a calculates a driving command value to be output by the actuator driver 6b, and sends the value to the actuator driver 6b. The actuator driver 6b sends the driving command values calculated by the computing unit 6a to the plurality of first actuators 4 and the second actuators 5, respectively. Each actuator generates a necessary force to deform the surface shape of the mirror 1, thereby correcting an error in optical performance. An example of the system shown in FIG. 2 is not limited to this.

[Exposure device]

The exposure apparatus according to this embodiment will be described with reference to FIG. 4. The exposure apparatus 50 of this embodiment may include an illumination optical system IL, a projection optical system PO, a mask stage MS capable of holding and moving a mask (prototype), and a substrate stage WS capable of holding and moving the substrate 56. The exposure device 50 may include a control unit 51 that controls a process of exposing the substrate 56.

Light emitted from a light source (not shown) included in the illumination optical system IL can be formed on the mask 55 through a slit (not shown) included in the illumination optical system IL, for example, which is longer in the Y direction. Arc-shaped exposure area. The mask 55 and the substrate 56 are held by a mask stage MS and a substrate stage WS, respectively, and are arranged at positions that are substantially conjugated optically (positions of the object plane and image plane of the projection optical system PO) via the projection optical system PO. The projection optical system PO has a predetermined projection magnification (for example, 1/2 times), and projects a pattern formed on the mask 55 onto the substrate 56. In addition, the mask stage MS and the substrate stage WS are scanned at a speed ratio corresponding to the projection magnification of the projection optical system PO in a direction (for example, the X direction) parallel to the object plane of the projection optical system PO. Accordingly, the pattern formed on the mask 55 can be transferred to the substrate 56.

As shown in FIG. 4, the projection optical system PO may be configured to include, for example, a flat mirror 52, a concave mirror 53, and a convex mirror 54. The exposure light emitted from the illumination optical system IL and transmitted through the mask 55 is refracted by the first surface 52 a of the plane mirror 52 and enters the first surface 53 a of the concave mirror 53. The exposure light reflected on the first surface 53 a of the concave mirror 53 is reflected by the convex mirror 54 and is incident on the second surface 53 b of the concave mirror 53. The exposure light reflected on the second surface 53b of the concave mirror 53 is refracted by the light path of the second surface 52b of the plane mirror 52, and is imaged on the substrate. In the projection optical system PO of such a configuration, the surface of the convex mirror 54 becomes an optical pupil. In the configuration of the exposure device 50, the above-mentioned optical device can be used, for example, as a device that deforms the reflecting surface of the concave mirror 53 as the mirror 1. By using the above-mentioned optical device for the exposure device 50, the reflecting surfaces (the first surface 53a and the second surface of the concave mirror 53) can be made The surface 53b) is deformed so that the optical aberration in the projection optical system PO can be corrected with high accuracy. Here, the control section 51 in the exposure device 50 may be configured to include a control section 6 for controlling an actuator in the optical device.

[Production method of article]

The method for producing an article according to the present embodiment is suitable for producing articles such as micro devices such as semiconductor devices or elements having a fine structure. The method of manufacturing an article according to this embodiment includes a process of forming a latent image pattern on a photosensitive agent applied to a substrate (substrate exposure process) and a process of developing a substrate on which a latent image pattern is formed by using the exposure device. In addition, the manufacturing method includes other known procedures (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). Compared with the existing method, the method for manufacturing an article according to this embodiment is advantageous in at least one of performance, quality, productivity, and production cost of the article.

[Other embodiments]

The present invention can also provide a system or device with a program that realizes one or more functions of the above-mentioned embodiment via a network or a memory medium, and can be read out and executed by one or more processors in a computer of the system or device. Program processing to achieve. Alternatively, it may be implemented by a circuit (such as an ASIC) that implements one or more functions.

Although the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary implementations example. The broadest explanation should be given to the scope of the attached patent application so that it covers all these variations and equivalent structures and functions.

Claims (9)

An optical device includes: a mirror having a reflecting surface and a back surface opposite to the reflecting surface; a base plate; a fixing member fixed to a part of the back surface to fix the mirror on the base plate; and a plurality of actuations And applying a force to the back surface to change the shape of the reflecting surface, wherein the plurality of actuators include: a plurality of first actuators that respectively apply a force to a first region in the back surface, and the first And a plurality of second actuators respectively apply a force to a second region surrounding the first region in the back surface, so that the driving current is I and the thrust is At F, regarding the efficiency of thrust generation represented by F / I, the efficiency of the thrust generation of the first actuator is higher than the efficiency of the thrust generation of the second actuator. For example, the optical device according to the first patent application scope, wherein the smaller the distance between the area of the back surface to which the force is applied and the fixed portion is, the more efficient the first actuator and the second actuator are. high. For example, the optical device according to the scope of patent application, wherein the first actuator and the second actuator are voice coil motors. For example, the optical device according to claim 3, wherein the voice coil motor includes a magnet disposed on the back surface and a coil disposed on the bottom plate. For example, in the optical device according to claim 1, wherein the first area is an area of 8% or less of the back surface. For example, in the optical device according to claim 1, the first area is an area of 3% or less of the back surface. A projection optical system that projects a pattern of a mask on a substrate. The foregoing projection optical system includes an optical device according to any one of claims 1 to 6 of the scope of patent application. An exposure device for exposing a substrate, the exposure device includes a projection optical system as in item 7 of the scope of patent application. An article manufacturing method comprising: a program for exposing a substrate using an exposure device such as the item No. 8 of the scope of patent application; and a program for developing the substrate exposed in the program; and developing the substrate from the developed Create items.