JP6881954B2 - Optical equipment, projection optics, exposure equipment, and article manufacturing methods - Google Patents

Description

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

With the recent miniaturization of line widths in semiconductor devices, liquid crystal display devices, and the like, there is a demand for higher definition exposure devices. In order to realize this high definition, it has been proposed to mount a variable mirror device in the exposure apparatus. The variable mirror device is an optical system that changes the mirror shape to correct aberrations, and is used as a technique for suppressing a decrease in image resolution due to atmospheric fluctuations when observing stars in the astronomical field, for example. The variable mirror device typically includes a mirror that is a variable mirror, an actuator, a base that holds the actuator, a sensor that detects the amount of deformation, and the like, and deforms the mirror shape by driving the back surface of the mirror with the actuator. ..

In Patent Document 1, a variable mirror device is applied to an exposure device, the amount of deviation from a target shape is measured, and a command is issued from a control unit to a plurality of actuators based on the measured value to deform the mirror. Discloses a configuration for correcting the image plane. It is expected that the imaging performance will be improved by installing the variable mirror device, but since the coil of the actuator generates heat when the mirror is driven, it is necessary to deal with it. The heat generated by the coil is transferred to the mirror and base, and the temperature of the mirror and the air temperature around it rises. As a countermeasure against such a temperature rise, Non-Patent Document 1 discloses a configuration in which a coil is provided at the end of a copper rod coupled to a cooling plate and the heat generated by the coil is recovered by the copper rod.

Further, in order to realize high definition of the exposure apparatus, there is also a technique for controlling the temperature of the exposure space. In an exposure apparatus, when the exposure process takes a long time, the optical element inside the projection optical system absorbs a part of the exposure light, and the energy of the absorbed light is converted into heat, and the optical element and the optical element are converted into heat. The temperature of the holding members and the gas surrounding them gradually rises. When the temperature of the gas on the optical path rises, the refractive index of the space changes, which affects the imaging performance.

In order to reduce the influence of the gas temperature, a technique for circulating a temperature-controlled gas in the internal space of the chamber accommodating the projection optical system has been proposed. For example, Patent Document 2 discloses a projection optical device that reduces thermal changes due to absorption of exposure energy by air-cooling the surfaces of a plurality of optical elements configured in the projection optical system.

Japanese Unexamined Patent Publication No. 2016-09230 Japanese Unexamined Patent Publication No. 60-79358

VLT Deformable Secondary Mirror: integration and electromechanical tests results, SPIE 8447, Adaptive Optics Systems III, 84472G (September 13, 2012)

When mounting the variable mirror device in a temperature-controlled space, it is necessary to suppress the adverse effect on the space due to the heat generated by the variable mirror device. Generally, the heat generated by the actuator of the variable mirror device is recovered by water cooling or the like, but cannot be completely removed, and the remaining heat is released into the space. The heat may flow out into a temperature-controlled space, changing the refractive index of that space and affecting imaging performance.

An object of the present invention is to provide an advantageous technique in terms of heat recovery performance generated when the reflecting surface of a mirror is deformed.

According to one aspect of the present invention, a mirror having a reflecting surface that reflects light and a back surface on the opposite side of the reflecting surface, and a first surface of the mirror facing the back surface and a second surface on the opposite side of the first surface. A base having two surfaces, a fixing member for fixing a part of the back surface to a part of the first surface, and a reflecting surface provided between the mirror and the base and applying a force to the back surface to deform the reflecting surface. An actuator for accommodating the mirror and a chamber for accommodating the mirror, an air supply port formed at a position on the reflection surface side of the mirror, and an exhaust formed at a position on the second surface side of the base. It has a chamber provided with a port, an attraction portion that attracts the gas on the reflection surface side, and the gas in the space formed by the back surface, the first surface, and the fixing member to the exhaust port. An optical device characterized by the above is provided.

According to the present invention, there is provided an advantageous technique in terms of the ability to recover heat generated when the reflecting surface of the mirror is deformed.

The figure which shows the structure of the variable mirror apparatus which concerns on embodiment. The figure which shows the structure of the exposure apparatus equipped with the variable mirror apparatus. The figure explaining the problem of the exposure apparatus equipped with the conventional variable mirror apparatus. The figure which shows the structure of the variable mirror apparatus which has the guide part which concerns on embodiment. It is the schematic for demonstrating Embodiment 2. FIG. It is the schematic for demonstrating Embodiment 3. The figure which shows the specific configuration example of the guide part which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and the following embodiments merely show specific examples of the embodiment of the present invention. In addition, not all combinations of features described in the following embodiments are essential for solving the problems of the present invention.

<First Embodiment>
(Optical device)
FIG. 1 is a diagram showing a configuration of a variable mirror device 100 according to the present embodiment. The variable mirror device 100, which is an optical device, is configured so that the shape of the reflecting surface of the mirror 101 can be changed. The outline of the configuration is as follows.

The mirror 101 is a thin mirror and has a reflecting surface 101a that reflects light and a back surface 101b on the opposite side thereof. The base 106 has a first surface 106a facing the back surface 101b of the mirror 101 and a second surface 106b on the opposite side. A part of the back surface 101b of the mirror 101 including the center, for example, is fixed to a part of the first surface 106a of the base 106 including the center by the fixing member 102. For the mirror 101, for example, low thermal expansion optical glass may be used in order to suppress the occurrence of shape error due to thermal strain. The reflective surface 101a is coated with a coating suitable for the wavelength of light used. The base 106 supports the mirror 101 via the fixing member 102, and also holds the displacement sensor 108 and the holder 107 for fixing the actuator.

The variable mirror device 100 has an actuator 103 that is provided between the mirror 101 and the base 106 and deforms the reflecting surface 101a by applying a force to the back surface 101b of the mirror 101. The actuator 103 is, for example, a voice coil motor (VCM) composed of a magnet 104 and a coil 105. For example, the magnet 104 is arranged on the back surface 101b of the mirror 101, and the coil 105 is fixed to the base 106 by being held by the holder 107 so as to face the magnet 104. A plurality of actuators 103 may be arranged over the entire surface of the mirror 101, but the present invention is not limited to the number and arrangement of specific actuators 103. Further, the actuator 103 may be an actuator other than the voice coil motor.

A flow path 109 is formed inside the base 106 as a water cooling mechanism, and a temperature-controlled refrigerant is supplied to the flow path 10 from a temperature control device (not shown). Water may be used as the refrigerant, or other liquids may be used. As the refrigerant circulates in the flow path 109, the heat generated by the actuator 103 is cooled via the heat transfer rod 110, and the heat conduction to the mirror 101 is reduced. As a result, the temperature of the base 106 is kept constant, and the influence of the thermal strain of the mirror 101 can be reduced.

The variable mirror device 100 may include a controller 120 that controls the actuator 103. The data of the target shape of the mirror 101 for correcting the error of the optical performance is input to the controller 120. The calculation unit 121 transmits a drive command value for each actuator to the driver 122 according to the input data. The driver 122 sends the received drive command value to the corresponding actuator 103. In response to this, each actuator generates a force according to the received drive command value. As a result, the surface shape of the mirror 101 is deformed, and an error in optical performance can be corrected.

Further, the variable mirror device 100 may include a chamber that houses the mirror 101 and the base 106, as will be described later with reference to FIG.
The variable mirror device 100 described above is expected to be used in an exposure device, an astronomical telescope, and the like. Hereinafter, an embodiment in which the variable mirror device 100 is used as an exposure device will be described.

(Exposure device)
FIG. 2 is a diagram showing a configuration of an exposure apparatus 200 equipped with the variable mirror apparatus 100. The exposure apparatus 200 is an apparatus that forms a latent image corresponding to the pattern of the mask on the resist by exposing the resist on the substrate through a mask (original plate). As the exposure method, there are a step-and-scan method and a step-and-repeat method, but here, the step-and-scan method is adopted. However, the present invention is not limited to a specific exposure method. The exposure apparatus 200 includes an illumination optical system 201, an alignment microscope 202, a mask stage 203 that holds a mask M on which a pattern is formed, a projection optical system 204, and a substrate that holds a substrate W (for example, a glass plate). It may be equipped with a stage 205. Further, the exposure apparatus 200 may include a control device 230 that controls the exposure process in an integrated manner.

The illumination optical system 201 has a light source and irradiates the mask M held on the mask stage 203 with exposure light. The alignment microscope 202 is an optical system for observing alignment marks formed on the mask M and the substrate W. The exposure apparatus 200 can transfer the pattern on the mask M onto the resist-coated substrate W by performing scanning exposure in synchronization with the mask M and the substrate W.

The projection optical system 204 is an optical system that projects an image of a pattern formed on the mask M onto the substrate W held on the substrate stage 205, and includes the variable mirror device 100 described above. Here, the mirror 101 of the variable mirror device 100 constitutes a concave mirror. The exposure light emitted from the illumination optical system 201 and transmitted through the mask M has an optical path bent by the plane mirror 207 and is incident on the reflecting surface 101a of the mirror 101 which is a concave mirror. The exposure light reflected by the reflecting surface 101a of the mirror 101 is reflected by the convex mirror 208 and is incident on the reflecting surface 101a of the mirror 101 again. The exposure light reflected by the reflecting surface 101a of the mirror 101 is formed on the substrate W by bending the optical path by the plane mirror 207. Here, the control device 230 in the exposure device 200 may be configured to include a controller 120 for controlling the actuator 103 in the variable mirror device 100.

By deforming the reflecting surface 101a of the mirror 101, it is possible to change the imaging position of the projection optical system 204. For example, by driving the actuator 103 according to the unevenness of the substrate W and changing the imaging position, high imaging performance can be maintained regardless of the shape of the substrate W.

As described above, the variable mirror device 100 may include a chamber accommodating the mirror 101 and the base 106, but in the present embodiment, this chamber is realized as a chamber 210 accommodating the projection optical system 204. An air supply port 210a and an exhaust port 210b are formed on the reflection surface side of the mirror 101 and near the top and bottom of the mirror 101 in the housing of the chamber 210. An air supply mechanism 211 and an exhaust mechanism 212 for stabilizing the temperature in the chamber 210 may be connected to the air supply port 210a and the exhaust port 210b, respectively. The gas (for example, air) temperature-controlled by the air conditioner 213 is sent into the chamber 210 by the air supply mechanism 211 via the air supply port 210a, and is exhausted through the exhaust port 210b by the exhaust mechanism 212. At the time of exposure, each optical element generates heat due to the exposure light, and the intake and exhaust can keep the internal space of the chamber 210 at an appropriate temperature.

FIG. 3A is a diagram illustrating the flow of heat and airflow in a conventional exposure apparatus. The air temperature-controlled by the air conditioner 213 by the air supply mechanism 211 is supplied to the surrounding space of the variable mirror device 100 through the air supply port 210a, and is exhausted by the exhaust mechanism 212 through the exhaust port 210b. In the conventional example of FIG. 3A, both the air supply port 210a and the exhaust port 210b are formed on the reflection surface side of the mirror 101 and near the top and bottom of the mirror 101 in the housing of the chamber 210.

At the time of exposure, the mirror 101 is irradiated with the exposure light 301. A reflective film is formed on the mirror 101, and most of the exposure light 301 is reflected, but the remaining slight exposure light is absorbed and converted into heat. The air 302 whose temperature has been raised by the heat of the mirror 101 rides on the flow of air supplied through the air supply port 210a by the air supply mechanism 211, and is exhausted through the exhaust port 210b by the exhaust mechanism 212. ..

Further, the heat of the actuator 103 that cannot be completely removed by the water cooling mechanism is released from the base 106 of the variable mirror device 100. The air 303 whose temperature has been raised by the heat of the base 106 travels toward the exhaust mechanism 212, crosses the exposure light 301, and is exhausted through the exhaust port 210b. At this time, the refractive index of the exposure light 301 may change due to the influence of the air 303 whose temperature has been raised by the heat of the base 106. In the case of an exposure apparatus not equipped with the variable mirror device 100, only the heat from the concave mirror was affected, but by mounting the variable mirror device 100, the heat of the base 106 is also affected. .. As a result, the imaging position of the projection optical system 204 changes unintentionally, which makes it difficult to maintain stable performance.

On the other hand, in FIG. 3B, the exhaust port 210b is formed at a position facing the second surface 106b of the base 106 (also referred to as “the position on the back surface side of the base 106”) in the housing of the chamber 210. However, a conventional example in which the exhaust mechanism 212 is arranged there is shown. In FIG. 3B, a plurality of exhaust ports 210b and exhaust mechanisms 212 are arranged. By providing the exhaust mechanism 212 at a position on the back surface side of the base 106, the air 303 whose temperature has been raised by the heat of the base 106 can be effectively exhausted.

On the other hand, the air 302 whose temperature has been raised by the heat of the mirror 101 tends to stay in the space near the exposure light 301 because the flow velocity becomes slow because the air 302 is far from the exhaust mechanism 212. The refractive index of the exposure light 301 can change due to the influence of the stagnant high-temperature air 302. As a result, the imaging position of the projection optical system 204 changes, so that it is still difficult to maintain stable performance.

FIG. 4 shows a configuration example of the present embodiment with respect to this. In FIG. 4, the space on the reflection surface side of the mirror 101 in the internal space of the chamber 210 is referred to as the first space S1. The space between the back surface 101b of the mirror 101 and the first surface 106a of the base 106 is referred to as a second space S2. Further, the space between the second surface 106b of the base 106 and the housing of the chamber 210 facing the second surface 106b is referred to as a third space S3. In the present embodiment, first, as in FIG. 3B, an exhaust port 210b is formed at a position facing the second surface 106b of the base 106 in the housing of the chamber 210, and the exhaust mechanism 212 is installed there. Further, a flow path 401 for communicating the first space S1 and the second space S2 with the third space S3 is provided.

The flow path 401 is formed by a flow path forming member as described later. The flow path forming member forms an opening 402 along the outer peripheral portion of the mirror 101. The cross-sectional area of the opening 402 shall be smaller than the cross-sectional area of other parts of the flow path 401. In general, the air existing in the exposure apparatus can be considered as an incompressible fluid, so that the cross-sectional area and the flow velocity are inversely proportional to each other. Therefore, the opening 402 functions as an orifice for attracting gas in the first space S1 and the second space S2, and the flow velocity temporarily increases at the opening 402. As a result, the air 302 whose temperature has been raised by the heat of the mirror 101 is collected in the flow path 401 through the opening 402 and flows to the exhaust port 210b. This prevents the air 302 whose temperature has been raised by the heat of the mirror 101 from staying in the vicinity of the optical path of the exposure light 301. Therefore, it is possible to reduce the influence of the air 302 whose temperature has been increased by the heat of the mirror 101 and the air 303 whose temperature has been increased by the heat of the base 106 on the space through which the exposure light 301 passes. In this way, it becomes possible to stably maintain the imaging performance of the exposure apparatus.

A specific configuration example of the flow path 401 will be described with reference to FIGS. 4 and 7. FIG. 7 is a perspective view of the mirror 101 around the variable mirror device 100 as viewed from the back surface side. The flow path 401 is formed by a partition wall 401a and a plate 401b, which are flow path forming members. The partition wall 401a is arranged in the chamber 210 so as to partition the first space S1 in a direction crossing the optical path of the light incident on the reflection surface 101a. The partition wall 401a is formed with an opening K equal to or larger than the diameter of the mirror 101 for passing light incident on the reflecting surface 101a. Here, the mirror 101 is installed at a predetermined distance (for example, several hundred mm) from the partition wall 401a on the back surface side of the base 106 so that a gap is formed between the mirror 101 and the partition wall 401a. A plurality of plates 401b are arranged along the side surface 106c connecting the first surface 106a and the second surface 106b of the base 106. The plurality of plates 401b are coupled to, for example, the partition wall 401a. The opening 402 that functions as an orifice can be formed by partially closing the gap between the mirror 101 and the partition wall 401a described above with a plurality of plates 401b.

In this embodiment, the base 106 can be supported by a plurality of (for example, three) support members 703 extending along the side surface 106c of the base 106. Here, the plurality of support members 703 are each coupled to the partition wall 401a. However, instead of such a dedicated support member, a plurality of plates 401b may be used to support the base 106.

The air supplied from the air supply port 211 passes through the opening 402 and is collected by the exhaust mechanism 212. As described above, since the flow velocity of this air temporarily increases as it passes through the opening 402, the flow velocity around the mirror 101 increases, and the effect of recovering heat is enhanced.

The opening 402 that functions as an orifice is formed, for example, in the first space, that is, on the optical path side of the position of the reflection surface 101a of the mirror 101. The inventor has confirmed by simulation that the exhaust effect around the mirror 101 is higher when the opening 402 is formed in the first space than when it is provided on the second space side.

<Second Embodiment>
In the first embodiment, the exhaust efficiency is promoted by the flow path 401 formed by the partition wall 401a and the plate 401b. On the other hand, in the second embodiment, the exhaust efficiency is promoted by utilizing the Coanda effect. As shown in FIG. 5, at the inlet of the flow path 401 in the first space S1, instead of the partition wall 401a, a nozzle 501 for ejecting compressed gas to the exhaust mechanism 212 side is provided. The compressed gas is supplied from a compressed gas supply device (not shown) via a pipe 502. The present invention is not limited to the specific type and number of nozzles 501 to be installed. By ejecting the compressed gas from the nozzle 501 to the exhaust mechanism 212 side, the coanda effect that attracts the gas in the first space S1 and the second space S2 entrains the gas at a flow rate several times the flow rate of the ejected compressed gas. It can be sent to the exhaust mechanism 212.

<Third Embodiment>
In the first embodiment, the flow path 401 is formed by the partition wall 401a and the plate 401b, but instead, as shown in FIG. 6, a through hole 601 penetrating the front and back surfaces of the base 106 may be provided. The cross-sectional area of the through hole 601 is widened so that the flow velocity of the air passing through the through hole 601 temporarily increases. Here, the partition wall 401a and the plate 401b are installed so as to fill the gap between the base 106 and the chamber 210. The air supplied from the air supply mechanism 211 passes through the through hole 601 and is collected by the exhaust mechanism 212. Since the through hole 601 has a small cross-sectional area and a high flow velocity, the air 302 whose temperature has increased due to the heat of the mirror 101 can also be recovered.

<Embodiment of Article Manufacturing Method>
The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing articles such as microdevices such as semiconductor devices and elements having a fine structure, for example. In the article manufacturing method of the present embodiment, a latent image pattern is formed on a photosensitive agent applied to a substrate by using the above-mentioned exposure apparatus (a step of exposing the substrate), and a latent image pattern is formed in such a step. Includes the process of developing the substrate. Further, such a manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, flattening, etching, resist peeling, dicing, bonding, packaging, etc.). The article manufacturing method of 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.

100: Variable mirror device, 101: Mirror, 102: Fixing member, 103: Actuator, 106: Base

Claims (14)

A mirror having a reflecting surface that reflects light and a back surface opposite the reflecting surface,
A base having a first surface facing the back surface of the mirror and a second surface opposite to the first surface,
A fixing member that fixes a part of the back surface to a part of the first surface,
An actuator provided between the mirror and the base and applying a force to the back surface to deform the reflecting surface.
A chamber that houses the mirror and the base, and includes an air supply port formed at a position on the reflection surface side of the mirror and an exhaust port formed at a position on the second surface side of the base. With the chamber
An attracting member that attracts the gas on the reflecting surface side and the gas in the space formed by the back surface, the first surface, and the fixing member to the exhaust port.
An optical device characterized by having. The exhaust port is formed on the first wall surface of the chamber facing the second surface, and the air supply port is formed on the second wall surface of the chamber orthogonal to the first wall surface. The optical device according to claim 1. The optical device according to claim 1 or 2, wherein the attracting member forms an orifice. The attracting member is
A partition wall arranged on the reflecting surface side of the mirror and partitioning in a direction crossing an optical path of light incident on the reflecting surface of the mirror, and an opening for passing light incident on the reflecting surface of the mirror. With the formed partition wall
A plurality of plates, each arranged along the side surface of the base,
Including
The optical device according to claim 3, wherein the orifice is formed by partially closing a gap between the mirror and the partition wall with the plurality of plates. The optical device according to claim 4, wherein each of the optical devices is coupled to the partition wall, extends along the side surface of the base, and further has a plurality of support members for supporting the base. The attractant member,
A plurality of plates which are disposed along their respective said base sides,
In addition to the gas on the reflection surface side of the mirror, a nozzle for attracting gas between the back surface and the first surface of the mirror to the exhaust port, and
The optical device according to claim 1 or 2, wherein the optical device comprises. The sixth aspect of claim 6, wherein the gas on the reflection surface side of the mirror and the gas between the back surface and the first surface of the mirror are attracted to the exhaust port by the Coanda effect. Optical device. The optical device according to claim 6 or 7, wherein the nozzle is arranged between the chamber and the plate. The attracting member is a plurality of plates, each of which is arranged along the side surface of the base.
The optical device according to claim 1 or 2, wherein the base is provided with a through hole penetrating the first surface and the second surface. A mirror having a reflecting surface that reflects light and a back surface opposite the reflecting surface,
A base having a first surface facing the back surface of the mirror and a second surface opposite to the first surface,
An actuator provided between the mirror and the base and applying a force to the back surface to deform the reflecting surface.
A chamber that houses the mirror and the base, and includes an air supply port formed at a position on the reflection surface side of the mirror and an exhaust port formed at a position on the second surface side of the base. With the chamber
An attracting member that attracts gas on the reflective surface side of the mirror to the exhaust port,
Have,
The attracting member is
A plurality of plates, each arranged along the side surface of the base,
In addition to the gas on the reflection surface side of the mirror, a nozzle for attracting gas between the back surface and the first surface of the mirror to the exhaust port, and
An optical device comprising. A mirror having a reflecting surface that reflects light and a back surface opposite the reflecting surface,
A base having a first surface facing the back surface of the mirror and a second surface opposite to the first surface,
An actuator provided between the mirror and the base and applying a force to the back surface to deform the reflecting surface.
A chamber that houses the mirror and the base, and includes an air supply port formed at a position on the reflection surface side of the mirror and an exhaust port formed at a position on the second surface side of the base. With the chamber
An attracting member that attracts gas on the reflective surface side of the mirror to the exhaust port,
Have,
The attracting member is a plurality of plates, each of which is arranged along the side surface of the base.
The base is provided with through holes penetrating the first surface and the second surface.
An optical device characterized by that. An image of a pattern formed on a mask to a projection optical system for projecting the substrate,
A projection optical system comprising the optical device according to any one of claims 1 to 11. An exposure device that exposes a substrate
Exposure apparatus comprising a projection optical system according to claim 1 2. A step of exposing a substrate using an exposure apparatus according to claim 1 3,
Including a step of developing the substrate exposed in the step.
A method for producing an article, which comprises producing an article from the developed substrate.

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