JP2023142214A - Optical device, exposure apparatus, and exposure method - Google Patents

Abstract

To provide a technique of shifting the course of light which can adjust a shift amount while suppressing an increase of an astigmatic difference despite a simple configuration.SOLUTION: An optical device that shifts the course of input light, and outputs output light along an optical path that is parallel with but not the same as an optical path of input light comprises: a first wedge prism in which an incident angle of input light is set at an angle at which a deflection angle of emitted light becomes the minimum; a second wedge prism which has an apex angle approximately the same as the first wedge prism, and is arranged in an opposite direction to the first wedge prism in a facing manner; a shift amount adjustment mechanism which supports the first wedge prism and the second wedge prism, and changes a distance between the prisms to adjust a shift amount; and a correction optical element which is arranged in an optical path of input light or an optical path of output light, and corrects an astigmatic difference appeared in output light.SELECTED DRAWING: Figure 3

Description

The present invention relates to an optical device that can be applied to a technique of exposing a substrate, such as a printed wiring board or a glass substrate, to draw a pattern thereon.

As a technology for forming patterns such as wiring patterns on various substrates such as semiconductor substrates, printed wiring boards, and glass substrates, a light beam modulated according to drawing data is applied to a photosensitive layer formed on the surface of the substrate. Some expose layers. In this type of technology, means for shifting the incident position of the light beam on the substrate is provided on the optical path in order to perform drawing at an appropriate position while adapting to distortions, deformations, etc. of the substrate.

For example, in the technique described in Patent Document 1, a pair of wedge prisms facing each other in opposite directions are arranged on an optical path. By changing the distance between the wedge prisms, the position of the image formed on the image plane by the passing light beam can be shifted. In this technique, the angle of incidence of light onto the prisms is set so that the astigmatism difference is approximately zero when the distance between the prisms is a reference value. In order to solve the problem that the astigmatism difference increases as the distance between the prisms changes, a method has been proposed in which the angle of incidence of light is changed by rotating a pair of wedge prisms.

Japanese Patent Application Publication No. 2009-244446

In the above conventional technology, in order to change the shift amount without increasing the astigmatism difference, it is necessary to rotate the prism pair in accordance with the change in the distance between the prisms. In particular, the mechanism for supporting and moving the wedge prism pair becomes complex in that it is necessary to realize rotational movement. Furthermore, in order to speed up the shift amount changing process, it is desirable that the support and adjustment mechanism be simple. For example, it would be more desirable if the shift amount could be changed simply by changing the distance between the prisms. In these respects, there is still room for improvement in the prior art described above.

This invention has been made in view of the above-mentioned problems, and provides a technology for shifting the path of light, which has a simple configuration and can adjust the amount of shift while suppressing an increase in astigmatism. The purpose is to

One aspect of the present invention is an optical device that shifts the path of input light and outputs output light along an optical path that is parallel to, but not identical to, the optical path of the input light, the incident angle of the input light being The first wedge prism is set at an angle that minimizes the polarization angle of the emitted light, and the apex angle is approximately the same as that of the first wedge prism, and the first wedge prism is arranged opposite to the first wedge prism in the opposite direction. , a second wedge prism that emits the output light from a surface opposite to the surface facing the first wedge prism, and a distance between the first wedge prism and the second wedge prism; an optical device comprising: a shift amount adjustment mechanism that adjusts a shift amount by changing the amount of shift; and a correction optical element that is disposed in the optical path of the input light or the optical path of the output light and corrects astigmatism difference appearing in the output light. It is.

In the invention configured in this way, similar to the technology described in Patent Document 1, the optical path is shifted by a wedge prism pair that is a combination of two wedge prisms, and the shift amount is changed by changing the distance between the wedge prisms. Adjust. However, in the first wedge prism into which the input light is incident, the angle of incidence is not set to a value that minimizes the astigmatism difference as described in Patent Document 1, but is set to a value that minimizes the deflection angle. At this time, as described in Patent Document 1, the magnitude of the astigmatism difference is approximately constant regardless of the distance between the wedge prisms. On the other hand, at that time, an astigmatism difference of a size that cannot be ignored remains.

Therefore, in the present invention, a correction optical element for correcting the astigmatism difference is separately provided on the optical path. Specifically, for example, the astigmatism difference can be corrected by arranging on the optical path an optical element that produces astigmatism that cancels out the astigmatism caused by the wedge prism pair.

If the correction is realized in this way, even if the distance between the wedge prisms is changed to change the shift amount, the state in which the astigmatism difference is corrected will be maintained. In other words, there is no need to change the amount of correction of the astigmatism difference depending on the amount of shift. As a result, the mechanism supporting the wedge prism pair only needs to realize linear motion that changes the distance between the wedge prisms. Therefore, it is possible to adopt a relatively simple configuration. Furthermore, since there is no need to rotate the wedge prism pair in accordance with changes in the shift amount, it is possible to speed up the processing for adjusting the shift amount.

Another aspect of the present invention includes a stage that supports a substrate to be processed, a light beam that is modulated based on predetermined exposure data, and the modulated light beam is transmitted to the substrate through the optical device. The exposure apparatus includes an exposure section that allows the light to enter the surface of the stage, and a movement mechanism that relatively moves the stage and the exposure section.

In the invention configured in this way, the above-described optical device is provided in the optical path of the light beam when exposing the surface of the substrate with the modulated light beam. Therefore, when it is necessary to adjust the incident position of the light beam in response to, for example, deformation of the substrate or positional shift on the stage, it is possible to utilize the shift of light by the optical device. The optical device of the present invention has a small astigmatism difference regardless of the amount of shift, and is therefore particularly suitable for such uses.

Another aspect of the present invention is an exposure method in which a light beam modulated based on predetermined exposure data is made incident on the surface of a substrate to expose the substrate. In this invention, the above optical device having a correction amount adjustment mechanism is disposed on the optical path of the light beam, and the correction amount adjustment mechanism is activated in advance so that the astigmatism difference appearing in the output light is minimized. The correction amount is optimized in advance. Then, when operating the shift amount adjustment mechanism to change the shift amount, there is no need to change the correction amount by the correction amount adjustment mechanism.

Even in the invention configured in this way, by arranging the optical device of the invention on the optical path, it is possible to adjust the incident position of the light beam onto the substrate. If the astigmatism difference is adjusted in advance to be the minimum (ideally zero), the astigmatism difference will not increase even if the shift amount is changed thereafter. Furthermore, the shift amount can be changed simply by changing the distance between the wedge prisms, and high-speed adjustment processing is possible.

As described above, in the present invention, when shifting light using two wedge prisms, the incident angle of the light is set to a condition that minimizes the declination angle, and the remaining astigmatism difference is corrected by a correction optical element. . Therefore, an optical device capable of changing the shift amount without increasing the astigmatism difference can be realized with a relatively simple configuration.

FIG. 2 is a diagram schematically showing a first configuration example of an exposure apparatus. It is a figure which shows typically the 2nd structural example of an exposure apparatus. FIG. 2 is a diagram showing the configuration of an image position adjustment device. It is a figure which shows the relationship between shift amount and astigmatism difference. FIG. 2 is a diagram illustrating a device configuration for adjusting the amount of correction of astigmatism difference. 7 is a flowchart illustrating processing for adjusting the amount of correction. 3 is a flowchart showing an exposure operation. It is a figure which shows the modification of a correction|amendment optical element. 2 is a diagram showing a modification of the exposure apparatus of FIG. 1. FIG.

Hereinafter, specific aspects of the optical device according to the present invention will be described by showing several embodiments. Here, an embodiment will be described in which an optical device according to the present invention is applied to an exposure apparatus that exposes a substrate with a modulated light beam to draw images. This exposure device draws a pattern on a photosensitive material by irradiating a substrate on which a layer of photosensitive material such as a resist is formed with laser light in a predetermined pattern. As the substrate to be exposed, various substrates such as printed wiring boards, glass substrates for various display devices, and semiconductor substrates can be used.

First, two configuration examples of exposure apparatuses to which the optical apparatus according to the present invention can be applied will be explained, and then details of the optical apparatuses applied to these exposure apparatuses will be explained.

<Exposure apparatus of first configuration example>
FIG. 1 is a diagram schematically showing a first configuration example of an exposure apparatus including an optical device according to the present invention. The basic configuration of this exposure apparatus 2 is the same as that described as "optical apparatus 2" in Patent Document 1. Therefore, the explanation of the principle, basic configuration, etc. that can be understood by referring to Patent Document 1 will be omitted, and the reference numerals will be shared as much as possible, and the outline of the device configuration will be briefly described here.

For the following explanation, an XYZ orthogonal coordinate system is defined as shown in FIG. FIG. 1 is a side view of the exposure apparatus 2, with the direction horizontal and perpendicular to the plane of FIG. 1 as the X direction, and the direction perpendicular to this, horizontal and along the plane of FIG. 1, as the Y direction. Further, the vertically downward direction is defined as the Z direction.

The exposure apparatus 2 includes a movable stage 20, an exposure head 21, and a control section 22. The movable stage 20 holds a substrate 9 to be exposed in a horizontal position, and an exposure head 21 makes a modulated light beam incident on the substrate 9, thereby drawing a fine pattern on the substrate 9. The control unit 22 implements predetermined operations by executing a control program prepared in advance and controlling each part of the apparatus.

Although not shown, a stage drive mechanism 201 is connected to the movable stage 20. The stage drive mechanism 201 includes a main scanning drive mechanism that moves the movable stage 20 in the Y direction, a sub-scanning drive mechanism that moves the movable stage 20 in the X direction, and an elevating mechanism that moves the movable stage 20 in the Z direction. For example, a linear motor can be used as a drive source for such a mechanism. Thereby, the exposure apparatus 2 can perform drawing by making the exposure beam emitted from the exposure head 21 enter any position on the substrate 9.

The exposure head 21 includes a light source 23, an illumination optical system 24, a spatial light modulation device 25, and an imaging optical system 26. The light source 23 is, for example, a lamp that emits light that becomes an exposure beam. Illumination optical system 24 guides the light emitted from light source 23 to spatial light modulation device 25 . The spatial light modulation device 25 modulates the light guided by the illumination optical system 24 based on predetermined drawing data to generate a modulated light beam.

The illumination optical system 24 includes optical elements such as a mirror 240, a lens 241, an optical filter 242, a rod integrator 243, a lens 244, and mirrors 245 and 246. By the action of these optical elements, the light from the light source 23 is shaped into a beam and guided to the spatial light modulation device 25 at a predetermined angle of incidence.

As the spatial light modulation device 25, for example, a DMD (digital micromirror device), a diffraction grating type spatial light modulation element, etc. can be used. The spatial light modulation device 25 modulates the incident light beam based on drawing data. Thereby, the light beam is modulated according to the shape of the pattern to be drawn. The modulated light beam is incident on the surface of the substrate 9 via the imaging optical system 26.

The imaging optical system 26 includes optical elements such as a first imaging lens 260, a mirror 261, an image position adjustment position 1, and a second imaging lens 262, and constitutes a reduction optical system. By the action of these optical elements, an optical image corresponding to the shape of the pattern to be drawn is formed on the surface of the substrate 9. Specifically, the modulated light beam forms a primary image (intermediate image) by the first imaging lens 260, and the primary image is formed by the second imaging lens 262 on the surface of the substrate 9, which is the image plane, to form a final image. becomes.

Further, a focus drive mechanism (not shown) that moves the second imaging lens 262 in the Z direction is coupled to the imaging optical system 26. When the control unit 42 operates the focus drive mechanism, the second imaging lens 262 moves toward and away from the substrate 9 as shown by dotted arrows. Thereby, the focus of the imaging optical system 26 is adjusted so that the light beam emitted from the second imaging lens 262 is converged on the surface of the substrate 9.

The image position adjustment device 1 corresponds to an embodiment of the "optical device" according to the present invention, and has a function of shifting incident light by an arbitrary distance in the X-axis direction. When the optical device according to the present invention is applied to the exposure device 2, it has a function of shifting the position of an image formed on an image plane, and in this sense functions as an image position adjustment device. In this embodiment, the image position adjustment device 1 is arranged between the primary image and the second imaging lens 262. Its structure and operation will be described later.

<Exposure apparatus of second configuration example>
FIG. 2 is a diagram schematically showing a second configuration example of an exposure apparatus including an optical device according to the present invention. In FIG. 2 as well, an XYZ orthogonal coordinate system is defined in accordance with FIG. 1. That is, FIG. 2 is a side view of the exposure device 4, and the horizontal direction and perpendicular to the plane of FIG. 2 is the X direction, and the direction perpendicular to this, horizontal and along the plane of FIG. 2, is the Y direction. Further, the vertically downward direction is defined as the Z direction.

As shown in FIG. 2, the exposure apparatus 4 includes a movable stage 40, an exposure head 41, a control section 42, and a light source unit 43. The movable stage 40 holds the substrate 9 to be exposed in a horizontal position, and is moved by a stage drive mechanism 401 in the X direction, Y direction, and Z direction. A fine pattern is drawn on the substrate 9 by causing the exposure head 41 to make a modulated light beam incident on the substrate 9 . The control unit 42 implements predetermined operations by executing a control program prepared in advance and controlling each part of the apparatus.

The light source unit 43 includes, for example, a laser diode 431 as a laser light source, and an illumination optical system 432 including a collimating lens that shapes the emitted light from the laser diode 431 into parallel light. Make it incident.

The exposure head 41 is provided with a spatial light modulator 410 having a diffractive optical element 411. Specifically, the spatial light modulator 410 attached to the upper part of the support column 400 extending in the vertical direction (Z direction) on the exposure head 41 is configured such that the reflective surface of the diffractive optical element 411 faces downward. It is supported by a support column 400 via a movable stage 412.

In the exposure head 41 , the diffractive optical element 411 is arranged such that the normal line of its reflecting surface is inclined with respect to the optical axis of the incident light beam, and the light emitted from the light source unit 43 passes through the opening of the support column 400 . The light enters the mirror 413, is reflected by the mirror 413, and then is irradiated onto the diffractive optical element 411. Then, the state of each channel of the diffractive optical element 411 is switched by the control unit 42 according to the exposure data, and the laser beam incident on the diffractive optical element 411 is modulated.

The laser light reflected from the diffractive optical element 411 as 0th-order diffracted light enters the lens of the imaging optical system 414, while the laser light reflected from the diffractive optical element 411 as 1st-order or higher-order diffracted light enters the imaging optical system 414. It does not enter the lens of system 414. That is, basically, the configuration is such that only the 0th order diffracted light reflected by the diffractive optical element 411 enters the imaging optical system 414.

The light that has passed through the lens of the imaging optical system 414 is converged by a focusing lens 415 and guided onto the substrate 9 as an exposure beam at a predetermined magnification. The imaging optical system 414 constitutes a reduction optical system. This focusing lens 415 is attached to a focus drive mechanism 416. Then, the focus drive mechanism 416 moves the focusing lens 415 up and down along the vertical direction (Z-axis direction) in response to a control command from the control unit 42, so that the convergence position of the exposure beam emitted from the focusing lens 415 is aligned with the substrate. It is adjusted to the upper surface of 9.

In this way, the light beam is modulated according to the shape of the pattern to be drawn, and the modulated light beam is incident on the surface of the substrate 9 via the imaging optical system 414, thereby forming a predetermined pattern on the surface of the substrate 9. is drawn.

The image position adjustment device 1 is arranged on the optical path from the diffractive optical element 411 to the imaging optical system 414. The configuration and function of the image position adjustment device 1 are the same as those provided in the exposure device 2 of the first configuration example.

FIG. 3 is a diagram showing the configuration of the image position adjustment device. This image position adjustment device 1 shifts a light beam in the X direction by a combination of a pair of two wedge prisms, that is, a first wedge prism 13 and a second wedge prism 14. The basic principle and specific design method are described in Patent Document 1, and the same concept can be adopted in this embodiment. Therefore, the principle and structure of light shifting by the wedge prism pair 10 will be briefly explained here.

The first wedge prism 13 and the second wedge prism 14 constituting the wedge prism pair 10 have substantially the same structure (for example, the apex angle α and the refractive index n are the same), and are arranged in opposite directions. , and are arranged with a predetermined gap in between so that the opposing surfaces are parallel to each other. As will be described later, the gap is variable and is used to adjust the shift amount.

The first wedge prism 13 is fixedly supported by a support portion 130 on a suitable housing. On the other hand, the second wedge prism 14 is supported via a support section 140 having a linear motion mechanism 141. As the linear motion mechanism 140, for example, a combination of a rotary motor controlled by the control unit 42 and a ball screw mechanism, a linear motor, or the like can be used.

The linear motion mechanism 141 moves the second wedge prism 14 in the vertical direction (Z direction) in response to a control command from the control unit 42 . As a result, the second wedge prism 14 moves toward and away from the first wedge prism 13 within a predetermined movable range, as shown by dotted arrows. As a result, the relative distance D1 between the two changes.

Input light Li traveling in the (+Z) direction is incident on the wedge prism pair 10. Specifically, the upper surface of the first wedge prism 13 on the upper side (-Z) side of the two wedge prisms (the non-opposing surface 13a on the opposite side to the opposing surface 13b facing the second wedge prism 14) Input light Li is incident on. The angle of incidence on the first wedge prism 13 at this time will be represented by the symbol φi.

The light incident on the first wedge prism 13 is refracted by the non-opposing surface 13a and the opposing surface 13b of the first wedge prism 13, and is emitted from the opposing surface 13b at an angle of deviation θ with respect to the straight direction of the light shown by the dotted line. . The light is further refracted by the opposing surface 14a and the non-opposing surface 14b of the second wedge prism 14, and is emitted downward as output light Lo.

The traveling direction of this output light Lo is the same (+Z) direction as the input light Li. Therefore, it is parallel to the light Loa that would be output if the input light Li went straight without being refracted, and its optical path is shifted in the (-X) direction by a distance D2 from the optical path of the light Loa. In other words, this wedge prism pair 10 has a function of outputting output light Lo obtained by shifting input light Li in the (-X) direction. As a result, the position of the image finally projected onto the substrate 9 changes in the X direction.

In the wedge prism pair 10, light enters and exits each of the two wedge prisms. Therefore, in this specification, to avoid confusion, the light that is primarily incident on the wedge prism pair 10 from the outside is referred to as "input light," and the light that is finally emitted from the wedge prism pair 10 is referred to as "output light." It is called.

As is clear from FIG. 3, the larger the distance D1 between the first wedge prism 13 and the second wedge prism 14, the larger the shift amount D2 becomes. That is, by moving the second wedge prism 14 and changing the distance D1, the shift amount D2 can be changed. By controlling the amount of movement of the second wedge prism 14 by the linear motion mechanism 141 by the control unit 42, an arbitrary shift amount can be realized.

Here, while the light passing through the wedge prism pair 10 is bent in the X direction due to refraction, the traveling direction remains unchanged in the Y direction. Due to such anisotropy, an astigmatism difference appears in the output light Lo. Therefore, as will be described below, when the light beam is finally focused on the surface of the substrate 9, there will be a difference in the focal position with respect to the image plane in the X direction and the Y direction, which may cause a deterioration in drawing quality.

FIG. 4 is a diagram showing the relationship between the shift amount and the astigmatism difference. More specifically, FIG. 4(a) is a graph schematically showing a change in astigmatism difference when the shift amount is changed. As described in Patent Document 1, and as plotted with a plurality of broken lines in FIG. 4(a), astigmatism occurs when the distance D1 between the wedge prisms is changed and the shift amount D2 is changed. The behavior of the distance difference differs depending on the incident angle φi.

In the technique described in Patent Document 1, a plot Pb is adopted in which the center of the shift amount variable range is set as a reference value (shift amount zero) and the astigmatism difference becomes zero when the shift amount is set to the reference value. was. In this case, the farther the shift amount is from the reference value, the larger the astigmatism difference becomes.To avoid this, rotating the wedge prism pair has been proposed as a method of changing the incident angle φi according to the shift amount. There is.

On the other hand, in this embodiment, a plot Pa is adopted in which the astigmatism difference does not change even if the shift amount is changed. It is known that when the angle of incidence is set so that the angle of argument θ becomes the minimum in the relationship between the angle of incidence φi and the angle of argument θ, such fluctuations in the astigmatism difference do not occur. However, at this time, regardless of the setting of the shift amount S, an astigmatism difference Da that is not necessarily small remains. In this embodiment, an attempt is made to make the astigmatism difference zero regardless of the shift amount S based on the following idea.

FIG. 4(b) is a diagram schematically showing changes in the focal position of the imaging optical system when the distance D1 between the wedge prisms is changed. Since the effective optical path length changes when the distance D1 between the wedge prisms changes, the imaging optical system for the image plane (imaging optical system 26 in the first configuration example, imaging optical system 414 in the second configuration example ) changes in focus position. Further, when there is an astigmatism difference, the focus position is different between the X direction and the Y direction.

However, when the incident angle φi is set so that the deflection angle θ is the minimum, the distance between the in-focus position in the X direction and the in-focus position in the Y direction, that is, the astigmatism difference is the distance D1 between the wedge prisms. It is a constant value Da regardless of the Therefore, it is conceivable to eliminate the astigmatism difference by arranging an optical element that cancels the astigmatism difference as a "correction optical element" on the optical path, separately from the wedge prism pair 10.

Specifically, for example, for an astigmatism difference in which the focal position in the X direction is farther away than in the Y direction, conversely, when the focal position in the Y direction is If optical elements that cause astigmatism are placed on the optical path, it becomes possible to correct the astigmatism difference by canceling each other out. If the astigmatism difference caused by such an optical element has the opposite sign and the same absolute value as the astigmatism difference caused by the wedge prism pair 10, the astigmatism difference on the image plane can finally be set to zero. .

As such a correction optical element, for example, an asymmetric lens having different focal lengths in the X direction and the Y direction can be used. For example, a cylindrical lens arranged with the axial direction as the X direction or the Y direction has power only in a direction perpendicular to the axial direction, and is suitable for such purposes.

In this embodiment, as shown in FIG. 3, a correction lens 15 serving as a correction optical element for the purpose of correcting such astigmatism difference is provided above the first wedge prism 13. In this example, the correction lens 15 is a cylindrical lens whose axial direction is in the Y direction. According to such a configuration, the focal position of the imaging optical system with respect to the image plane can be maintained in the Y direction and brought closer to the imaging optical system side in the X direction.

In order to make it possible to reduce the astigmatic difference to zero, the correction lens 15 is supported so as to be movable up and down. Specifically, the correction lens 15 is supported by a support section 150 having a linear motion mechanism 151. The linear motion mechanism 151 can be realized, for example, by a combination of a rotary motor and a ball screw mechanism, or a linear motor. The linear motion mechanism 151 operates in response to a control command from the control unit 42 and moves the correction lens 15 in the vertical direction (Z direction). Thereby, it is possible to adjust the amount of correction for the astigmatism difference to realize a condition in which the astigmatism difference caused by the wedge prism pair 10 is completely canceled.

の関係を満たすように、第１ウェッジプリズム１３、第２ウェッジプリズム１４および支持部１４０の仕様が決定される。次に、こうして仕様が決定されたウェッジプリズム対１０に対する入力光Ｌｉの入射角φｉが、偏角θが最小となる条件を表す次式：

の関係を満たすように定められる。 The astigmatism difference correction effect according to this embodiment is obtained as follows. First, at the design stage of the device, the specifications of the first wedge prism 13 and the second wedge prism 14 are determined, and the incident angle φi of the input light Li with respect to the wedge prism pair 10 is determined accordingly. Specifically, by the method described in Patent Document 1, the apex angle α, the refractive index n, the maximum actual shift amount S required on the image plane, the movable range width d of the second wedge prism 14, and the image position adjustment. Using the magnification M of the lens after device 1, the following formula:

The specifications of the first wedge prism 13, the second wedge prism 14, and the support portion 140 are determined so as to satisfy the following relationship. Next, the following formula expresses the condition that the angle of incidence φi of the input light Li to the wedge prism pair 10 whose specifications have been determined in this way minimizes the angle of deviation θ:

It is determined to satisfy the following relationship.

In this manner, in this embodiment, once the specifications of the wedge prism pair 10 are determined, the incident angle φi of the input light thereto is also determined at the design stage. Therefore, if the incident angle φi is set with sufficient accuracy at the time of assembling the device or initial adjustment, there is basically no need to change it thereafter.

On the other hand, in order to maximize the effect of correcting the astigmatism difference (ideally reducing the astigmatism difference to zero), the radius of curvature of the cylindrical lens, which is the correction lens 15, and its position on the optical path must be appropriately set. There is a need to. More simply, the amount of correction of the astigmatism difference can be optimized by adjusting the position of the correction lens 15 as follows. Although adjustment processing using the exposure apparatus 2 of the first configuration example will be described here, the same concept can be applied to the second exposure apparatus 4 as well.

FIG. 5 is a diagram showing the configuration of an apparatus for adjusting the amount of correction of astigmatism difference. Further, FIG. 6 is a flowchart showing processing for this adjustment. As shown in FIG. 5, the process for optimizing the amount of astigmatism correction by the cylindrical lens 15 involves placing a dummy substrate 52 in place of the substrate 9 at a position corresponding to the image plane, and This is done by capturing the projected image with the observation camera 51. The observation camera 51 and the dummy substrate 52 may be provided for this purpose, but may also be provided in advance for the purpose of, for example, calibrating the autofocus mechanism in the exposure head.

In order to be positioned directly below the movable stage 20 and selectively the exposure head 21, the observation camera 51 and the dummy substrate 52 are required to move in the horizontal direction. Furthermore, it is required to move in the Z direction in order to search for a focusing position, which will be described later. For example, such a mechanism can be attached to the side of the movable stage 20 provided with a mechanism for moving in these directions.

The specific processing is as follows. First, a dummy substrate 52 and an observation camera 51 are placed in place of the movable stage 20 at a position that hits the image plane of the exposure beam (step S101). Further, the correction lens 15 is temporarily set at an appropriate reference position (step S102). Although the position of the second wedge prism 14 at this time is arbitrary, it can be set as a reference position, for example.

In this state, the exposure head 21 projects a predetermined reference pattern onto the surface of the dummy substrate 52 on the image plane (step S103). This reference pattern is for individually measuring the focal position in the X direction and the Y direction, and for example, a combination of lines in the X direction and lines in the Y direction can be used. The reference pattern may be projected by modulating the exposure beam with the spatial light modulation device 25, or by placing an adjustment mask on the optical path.

In this way, the astigmatism difference is determined using the reference pattern projected onto the surface of the dummy substrate 52. Specifically, the observation camera 51 images the reference pattern, and the image data is given to the control unit 22. The control unit 22 moves the observation camera 51 and the dummy substrate 52 integrally in the Z direction, and determines the position where the reference pattern in the X direction is most clearly projected onto the image plane, that is, when it is focused on the image plane. and the position when the reference pattern in the Y direction is focused on the image plane (step S104), and the difference between them is calculated and used as an astigmatism difference (step S105).

If the obtained astigmatism difference is less than or equal to the predetermined tolerance value (YES in step S106), the adjustment process can be ended because the astigmatism difference correction is functioning effectively. On the other hand, if the astigmatism difference exceeds the predetermined tolerance (NO in step S106), the amount of movement of the correction lens 15 is calculated based on the magnitude and sign, and correction is made according to the amount of movement. The lens 15 is moved in the Z direction (step S107). As the amount of movement of the correction lens 15, for example, a value obtained by dividing the value of the astigmatism difference calculated on the image plane by the square of the magnification of the optical system between the image position adjustment device 1 and the image plane is used. be able to.

Then, the evaluation of the astigmatism difference in steps S104 to S106 is performed again. By repeating this, it is possible to drive the correction lens 15 to the optimum position for minimizing the astigmatism difference (ideally zero).

The correction of the astigmatism difference optimized in this way functions effectively even when the position of the second wedge prism 14 is changed. In other words, in order to make this possible, the incident angle φi of the input light Li with respect to the wedge prism pair 10 is selected to a value that minimizes the deviation angle θ. Therefore, even if the position of the second wedge prism 14 is changed in order to change the shift amount in a subsequent exposure operation, there is no need to change the position of the correction lens 15.

It is sufficient that this adjustment process is executed at a timing such as when starting up the apparatus, during regular maintenance, during the operating time of the apparatus, or when the number of processed substrates reaches a predetermined value. Furthermore, for example, if the device is placed in a stable environment with few temperature changes, it may be sufficient to make adjustments only at the time of installation. In any case, the frequency of execution is not so high, and there is no need to perform it particularly during execution of the exposure operation described below.

FIG. 7 is a flowchart showing the exposure operation. After the above-described adjustment processing has been performed, the substrate 9 to be subjected to exposure processing is carried into the apparatus and placed on the movable stage 20 (step S201). Next, an alignment adjustment is performed in which the positional relationship between the substrate 9 on the movable stage 20 and the exposure head 21 is grasped, and the position is adjusted as necessary (step S202). Since a known technique can be applied to the alignment adjustment, a description thereof will be omitted.

Then, the movable stage 20 is moved to a predetermined exposure position (step S203), and the amount of image shift required to accommodate the positional deviation of the substrate 9 detected in the alignment adjustment is calculated (step S204). The amount of movement required in the second wedge prism 14 is determined according to the amount of shift required on the image plane (step S205). Specifically, the amount of movement of the second wedge prism 14 is determined from the amount of shift required on the image plane and the magnification of the imaging optical system. Based on the result, the second wedge prism 14 is moved to a new position (step S206). At this time, fluctuations in astigmatism due to the second wedge prism 14 do not occur. Therefore, there is no need to move the correction lens 15.

From the relationship shown in FIG. 4(b), changing the distance D1 in the wedge prism pair 10 causes a change in the focal position of the imaging optical system 26. Therefore, depending on the new position of the second wedge prism 14, the Z-direction position of the imaging lens, specifically the second imaging lens 262, is changed by the focus drive mechanism (step S207).

In this state, the surface of the substrate 9 is exposed by being irradiated with an exposure beam modulated according to the drawing data from the exposure head 21 (step S208), and a predetermined pattern is drawn. The processes of steps S203 to S208 are continuously executed until the drawing on the substrate 9 is completed (step S209). This completes the exposure operation for one substrate 9.

As described above, in the image position adjustment device 1 of this embodiment provided in the exposure devices 2 and 4, the wedge prism pair 10 realizes a shift of the image position in the X direction. The astigmatic difference caused by the wedge prism pair 10 is corrected by providing a correction lens 15 having different powers in the X direction and the Y direction. Since the incident angle φi of light to the wedge prism pair 10 is set so that the deviation angle θ is the minimum, the astigmatism difference does not change even if the distance between the wedge prisms is changed. Therefore, the correction effect of the astigmatism difference by the correction lens 15 is effective regardless of the distance between the wedge prisms, and the amount of shift can be changed only by linear motion of the wedge prisms, and an increase in the astigmatism difference occurs. do not have.

<Modified example>
FIG. 8 is a diagram showing a modification of the correction optical element. FIG. 8A shows a modification in which a parallel plane plate 16 (a pair of parallel plane plates 16a, 16b) is used as a correction optical element in place of the cylindrical lens. It is known that astigmatism occurs when a parallel plane plate is arranged at an angle with respect to the optical path, and by utilizing this fact, it is possible to correct the astigmatism difference caused by the wedge prism pair 10. . In this case, whether the parallel plane plate 16a is tilted around the X axis or around the Y axis is determined depending on which of the focal positions in the X direction or the Y direction is farthest. On the other hand, the parallel plane plate 16b is tilted in the opposite direction of the same axis as the parallel plane plate 16a. As a result, the parallel plane plates 16a and 16b assume a so-called V-shaped posture in which they are tilted by the same amount in opposite directions from the parallel state, and the parallel shift of the input light Li caused by the parallel plane plate 16a is transferred to the parallel plane plate 16b. cancels out. Here, tilting around the X-axis means tilting so that the normal vector of the main surface of the parallel plane plate 16a has a component in the Y direction and no component in the X direction. Tilting means the opposite. Further, by providing a drive mechanism 161 for changing the magnitude of the inclination, it becomes possible to adjust the amount of correction for the astigmatism difference.

Moreover, FIG. 8(b) shows a modification in which a variable curvature mirror 17 is used as a correction optical element in place of the cylindrical lens. Furthermore, a folding mirror 171 may be provided as appropriate to fold back the optical path of the input light. Even in such an embodiment, by using the variable curvature mirror 17 whose curvature (power) can be changed without moving the position, it is possible to correct the astigmatism difference caused by the wedge prism pair 10. It is possible.

In this sense, by making the mirror 246 in the exposure apparatus 2 of FIG. 1 a variable curvature mirror as described above, it is also possible to make it function as a correction optical element. In this case, there is no need to provide a correction optical element within the image position adjustment device 1. In other words, the correction optical element constituting the image position adjustment device 1 is provided inside the illumination optical system 24.

FIG. 9 is a diagram showing a modification of the exposure apparatus shown in FIG. In the exposure apparatus 2a of this modification, the mirror 246 in the exposure apparatus 2 of FIG. is provided. In this way, the correction optical element does not need to be provided immediately before the wedge prism pair 10, and can be placed at an appropriate position on the optical path.

In this case, since the correction lens 15a also has a function as a focus lens for the spatial light modulation device 25, the "reference position" in step S102 in the adjustment process of FIG. This is the position where the modulation device 25 is focused.

As explained above, in the above embodiment, the image position adjustment device 1 functions as the "optical device" of the present invention, and the correction lens 15, the parallel plane plate 16, the variable curvature mirror 17, etc. function as the "optical device" of the present invention. It functions as a "corrective optical element." Moreover, the support parts 130 and 140 function as a "shift amount adjustment mechanism" of the present invention. On the other hand, the support portion 150 and the drive mechanism 161 function as a "correction amount adjustment mechanism" of the present invention.

Furthermore, in the exposure apparatuses 2 and 4 of the embodiments described above, the movable stages 20 and 40 function as the "stage" of the present invention, and the stage drive mechanisms 201 and 401 function as the "moving mechanism" of the present invention. Further, the exposure heads 21 and 41 function as the "exposure section" of the present invention.

Further, in the above embodiment, the X direction, which is the direction in which the light is shifted, corresponds to the "first direction" of the present invention, and the Y direction perpendicular to this corresponds to the "second direction" of the present invention. Here, in the above explanation, the final emission direction of the exposure beam is the vertical Z direction, and the image shift direction is the X direction, so the operation explanation is based on the XYZ coordinate system. . However, essentially, there is no necessity to relate it to the vertical direction, and the discussion should be made based on the traveling direction of input light (or output light). In that case, among the directions perpendicular to the incident direction of the input light, the direction parallel to the shift direction of the output light and the direction perpendicular thereto can be considered as the "first direction" and "second direction" of the present invention, respectively. Can be done.

Note that the present invention is not limited to the embodiments described above, and various changes other than those described above can be made without departing from the spirit thereof. For example, in the embodiment described above, the correction lens 15 and the like as the correction optical element are arranged in front of the wedge prism pair 10 in the light traveling direction, that is, on the optical path of the input light Li. However, a correction optical element may be arranged behind the wedge prism pair 10, that is, on the optical path of the output light Lo. However, as in this embodiment, by arranging the correction optical element on the optical path before the image is shifted, the light incident range is limited, and thus the design of the optical element becomes easier.

Further, in the above embodiment, the correction lens 15 as a correction optical element is a single cylindrical lens, but for example, the focal length is different from that of a cylindrical lens whose axial direction is in the X direction, and whose axial direction is in the Y direction. A correction optical element may be configured in combination with a cylindrical lens. Further, the correction optical element may also have the functions of a lens or the like provided in the illumination optical system or the imaging optical system. Further, for example, a concave lens, a convex mirror, or the like may be used as the correction optical element.

Furthermore, in the adjustment process of the embodiment described above, the correction of the astigmatism difference by the correction optical element is aimed at making the astigmatism difference less than or equal to a predetermined tolerance value. However, it may be aimed that the astigmatism difference after correction becomes zero, and naturally, the most ideal state is that the astigmatism difference is zero and there is no fluctuation.

Further, in the above embodiment, the incident angle φi of the input light Li to the wedge prism pair 10 is fixed. However, this may be made variable. However, in the present invention, there is no need to change the angle of incidence during operation, so a drive mechanism for changing the angle of incidence is not required, and a mechanism for manual adjustment may be used, for example.

Further, in the embodiments described above, the optical device according to the present invention is applied to an exposure device that exposes a substrate to draw a pattern. However, the application of the optical device of the present invention is not limited to this. For example, the present invention can also be applied to a projection device such as a projector.

As described above with reference to specific embodiments, in the optical device according to the present invention, the first direction is a direction perpendicular to the direction of incidence of input light and parallel to the shift direction of output light with respect to input light. When the direction perpendicular to the incident direction and the first direction is the second direction, the correction optical element may be an optical element that produces astigmatism between the first direction and the second direction. By using an optical element whose characteristics are asymmetric in two orthogonal directions, that is, having anisotropy, the astigmatism difference that occurs between the first and second directions due to the wedge prism can be canceled. This makes it possible to perform corrections such as:

Here, as the correction optical element, for example, a lens having different focal lengths in the first direction and the second direction can be used. Alternatively, a variable curvature mirror whose curvature can be changed between a cross section including the first direction and a cross section including the second direction may be used as the correction optical element. In any of these methods, astigmatism can be corrected by selecting and using an optical element having appropriate optical characteristics.

Further, a correction amount adjustment mechanism may be further provided that adjusts the amount of correction of the astigmatism difference by moving a lens serving as a correction optical element in a direction along the optical path. By making the correction amount adjustable in this manner, the conditions required for optical specification of the correction optical element are relaxed.

Further, for example, the correction optical element may be a parallel plane plate tilted with respect to the optical path so that the normal vector of the main surface has a component in either the first direction or the second direction. Even with such a configuration, it is possible to correct the astigmatism difference by appropriately setting the thickness, refractive index, magnitude of inclination, etc. Also in this case, a correction amount adjustment mechanism may be further provided that adjusts the amount of correction of the astigmatism difference by changing the inclination of the correction optical element.

The present invention can be used to shift the position of a light beam or an image formed by it by a predetermined amount in a predetermined direction. Suitable for technical fields that involve exposure to light.

1 Image position adjustment device (optical device)
2, 4 Exposure device 9 Substrate 10 Wedge prism pair 13 First wedge prism 14 Second wedge prism 15 Correction lens (correction optical element)
16 (16a, 16b) Parallel plane plate (correction optical element)
17 Variable curvature mirror (correction optical element)
20,40 Movable stage (stage)
21, 41 Exposure head (exposure section)
130, 140 Support part (shift amount adjustment mechanism)
150 Support part (correction amount adjustment mechanism)
161 Drive mechanism (correction amount adjustment mechanism)
201,401 Stage drive mechanism (moving mechanism)
Li Input light Lo Output light X 1st direction Y 2nd direction

Claims (9)

An optical device that shifts the path of input light and outputs output light along an optical path that is parallel to but not identical to the optical path of the input light, the optical device comprising:
a first wedge prism in which the incident angle of the input light is set to an angle that minimizes the polarization angle of the output light;
The apex angle is approximately the same as that of the first wedge prism, the prism is arranged opposite to the first wedge prism, and the output light is emitted from a surface opposite to the surface facing the first wedge prism. a second wedge prism,
a shift amount adjustment mechanism that supports the first wedge prism and the second wedge prism and adjusts the shift amount by changing the distance between them;
An optical device comprising: a correction optical element disposed in the optical path of the input light or the optical path of the output light to correct an astigmatism difference appearing in the output light. When a direction perpendicular to the direction of incidence of the input light and parallel to a shift direction of the output light with respect to the input light is a first direction, and a direction perpendicular to the direction of incidence and the first direction is a second direction,
The optical device according to claim 1, wherein the correction optical element is an optical element that produces astigmatism between the first direction and the second direction. The optical device according to claim 2, wherein the correction optical element is a lens having different focal lengths in the first direction and the second direction. The optical device according to claim 3, further comprising a correction amount adjustment mechanism that adjusts the amount of correction of the astigmatism difference by moving the correction optical element in a direction along the optical path. The optical device according to claim 2, wherein the correction optical element is a variable curvature mirror that changes curvature between a cross section including the first direction and a cross section including the second direction. 2. The correction optical element is a parallel plane plate tilted with respect to the optical path so that the normal vector of the main surface has a component in either the first direction or the second direction. The optical device described in . The optical device according to claim 6, further comprising a correction amount adjustment mechanism that adjusts the amount of correction of the astigmatism difference by changing the inclination of the correction optical element. a stage that supports a substrate to be processed;
an exposure unit that modulates a light beam based on predetermined exposure data and causes the modulated light beam to enter the surface of the substrate via the optical device according to any one of claims 1 to 7;
An exposure apparatus, comprising: a movement mechanism that relatively moves the stage and the exposure section. An exposure method in which a light beam modulated based on predetermined exposure data is incident on a surface of a substrate to expose the substrate,
arranging the optical device according to claim 4 or 7 on the optical path of the light beam;
activating the correction amount adjustment mechanism in advance to optimize the correction amount so that the astigmatism difference appearing in the output light is minimized;
An exposure method in which the correction amount by the correction amount adjustment mechanism is not changed when the shift amount adjustment mechanism is operated to change the shift amount.

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