JP2019015974A - Exposure apparatus and exposure method - Google Patents

Abstract

To provide an exposure apparatus and an exposure method by which higher efficiency and a longer service life of a spatial optical modulation element can be achieved.SOLUTION: An exposure apparatus 100 includes: a microlens array 142 in which microlenses for condensing UV light from a light source are arranged in an array; a spatial optical modulation part (digital micromirror device) 12 where a plurality of micromirrors for modulating the UV light condensed by the microlens array 142 are arranged with a gap interposed between the mirrors; a first imaging optical system 143 for imaging the UV light condensed by the microlens array 142 onto the micromirrors of the spatial optical modulation part 12 while preventing the light from entering the gap; and a second imaging optical system 16 for imaging the UV light modulated by the spatial optical modulation part 12 onto a photosensitive material.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an exposure apparatus and an exposure method for passing light modulated by a spatial light modulation element through an imaging optical system and forming an image of the light on a predetermined surface.

In recent years, light modulated using a spatial light modulator such as DMD (Digital Micromirror Device (registered trademark)) is passed through a projection optical system, and an image of this light is formed on a photosensitive layer (resist). An exposure apparatus that performs exposure is proposed. Thus, an exposure apparatus using a spatial light modulator is called a DI (direct image) exposure apparatus.
As such a DI exposure apparatus, for example, there is a technique described in Patent Document 1. The DI exposure apparatus includes a plurality of exposure heads having a spatial light modulator (DMD), a first projection optical system, a microlens array (MLA), and a second projection optical system. The DI exposure apparatus projects light modulated by DMD onto the MLA by the first projection lens, and projects light transmitted through the MLA onto a predetermined light irradiation surface by the second projection lens. Have Here, the MLA is a lens in which microlenses corresponding to the respective pixel portions of the DMD are arranged in an array in accordance with the positions of the respective pixels of the DMD.

JP 2001-305663 A

In the technique described in Patent Document 1, light from a light source is irradiated on the entire surface of the DMD. The DMD has a configuration in which micromirrors (micromirrors) are two-dimensionally arranged, and there are microscopic gaps between adjacent micromirrors. Therefore, when light is irradiated on the entire surface of the DMD, the gap is also irradiated with light. However, the light applied to the gaps between the micromirrors does not contribute to the spatial modulation, causing a reduction in element efficiency. Further, as light from the light source, for example, ultraviolet light (UV light) is used. If such UV light is irradiated onto the substrate of the DMD from the gap, it becomes a factor of reducing the lifetime of the element.
Therefore, an object of the present invention is to provide an exposure apparatus and an exposure method that can improve the efficiency and life of the spatial light modulator.

In order to solve the above problems, an aspect of the exposure apparatus according to the present invention includes a microlens array in which microlenses that collect ultraviolet light from a light source are arranged in an array, and the microlens array collects the microlens. A spatial light modulation unit in which a plurality of micromirrors that modulate ultraviolet light are arranged in an array through a gap, and the spatial light so that ultraviolet light collected by the microlens array is not incident on the gap. A first imaging optical system that forms an image on the micromirror of the modulation unit; and a second imaging optical system that forms an image of the ultraviolet light modulated by the spatial light modulation unit on a photosensitive material.
Thereby, the ultraviolet light from the light source can be condensed by the micro lens array (MLA), and the ultraviolet light condensed by the MLA can be imaged on the spatial light modulation unit without being incident on the gap between the micro mirrors. . That is, the ultraviolet light condensed by the MLA can be incident on the spatial light modulator without loss. Therefore, the efficiency of spatial modulation can be improved. Further, the ultraviolet light collected by the MLA is not irradiated onto, for example, the substrate of the spatial light modulation unit that does not contribute to the spatial modulation. Therefore, the deterioration of the element can be suppressed and the life can be extended.

In the above exposure apparatus, the spatial light modulation unit may be a digital micromirror device, and the micromirror may be a micromirror corresponding to the microlens on a one-to-one basis.
In this way, by using a digital micromirror device (DMD) with high light utilization efficiency as the spatial light modulator, ultraviolet light from the light source can be efficiently used as exposure light. Also, the DMD micromirrors are made to correspond one-to-one with the MLA microlens, and the ultraviolet light collected by the MLA is imaged on the DMD micromirror, so that crosstalk between pixels is suppressed and the extinction ratio is reduced. The decrease can be suppressed.

  Furthermore, in the above exposure apparatus, the first imaging optical system applies spot-like ultraviolet light collected by each microlens of the microlens array onto the corresponding micromirror. You may image with a spot size smaller than the size of a mirror. In this way, since ultraviolet light having a spot size smaller than the size of the micromirror is imaged on the micromirror, it is possible to reliably prevent the ultraviolet light from entering the gap formed between the micromirrors. Can do.

Furthermore, in the above exposure apparatus, the second imaging optical system may be an enlarged imaging optical system. As described above, the ultraviolet light modulated by the spatial light modulator is enlarged to form an image on the photosensitive material, so that the resolution requirement can be appropriately satisfied by adjusting the magnification. Further, the image can be enlarged while keeping the sharpness of the image projected on the photosensitive material high.
In the above exposure apparatus, the first imaging optical system may be a reduction imaging optical system. As described above, by reducing the ultraviolet light collected by the MLA and forming an image on the spatial light modulator, it is possible to employ an MLA having a relatively large condensing spot size. Therefore, manufacture of MLA becomes easy.

Furthermore, in one aspect of the exposure method according to the present invention, ultraviolet light from a light source is collected by a microlens array in which microlenses are arranged in an array, and a plurality of ultraviolet lights collected by the microlens array are collected. An image is formed on the micromirror of the spatial light modulator arranged in an array through the gap so as not to enter the gap, and the ultraviolet light modulated by the spatial light modulator is applied to the photosensitive material. To form an image.
Thereby, the ultraviolet light condensed by the MLA can be incident on the spatial light modulator without loss, and the efficiency of spatial modulation can be improved. Further, since the ultraviolet light collected by the MLA is not irradiated onto, for example, the substrate of the spatial light modulation unit that does not contribute to the spatial modulation, the deterioration of the element can be suppressed and the life can be extended.

  According to the present invention, the ultraviolet light condensed by the microlens array can be incident on the spatial light modulator without loss. Therefore, it is possible to improve the efficiency and extend the life of the spatial light modulator.

It is a schematic block diagram which shows the exposure apparatus of this embodiment. It is a figure which shows the principal part of an exposure head unit. It is the elements on larger scale which show the structure of DMD. It is a perspective view which shows schematic structure of an exposure head. It is an optical arrangement | positioning figure which shows the structure of an exposure head. It is a figure which shows the state of the spot irradiated to a DMD surface. It is an optical arrangement | positioning figure which shows the structure of the conventional exposure head. It is a figure which shows the state of the light irradiated to the conventional DMD surface. It is a figure which shows the structure of the conventional MLA surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram that shows the exposure apparatus of the present embodiment.
The exposure apparatus 100 exposes light modulated by a spatial light modulator (spatial light modulation element) through an imaging optical system and forms an image of this light on a photosensitive material (resist). Since such an exposure apparatus directly forms an image with a spatial light modulation element, no mask (or reticle) is required, and it is called a DI (direct image) exposure apparatus.

The exposure apparatus 100 includes an exposure head unit 10, a transport system 20 that transports a substrate (workpiece) W to be exposed, and a thick plate-shaped installation base 30 on which the exposure head unit 10 and the transport system 20 are installed. Here, the workpiece W is, for example, a resin printed board coated with a resist.
The exposure head unit 10 is fixed to a gate-like gate (gantry) 31 provided so as to straddle the installation table 30, and each end of the gate 31 is fixed to a side surface of the installation table 30. Further, the installation table 30 is supported by a plurality of (for example, four) leg portions 32.

  The transport system 20 includes, as an example, a flat plate-like stage 21 that sucks and holds the workpiece W by a method such as vacuum suction, two guides 22 that extend along the moving direction of the stage 21, and a moving mechanism of the stage 21. And an electromagnet 23. Here, a linear motor stage is employed as the moving mechanism. In the linear motor stage, a moving body (stage) is levitated by air on a flat platen provided with ferromagnetic convex poles in a lattice shape, and a magnetic force is applied to the moving body, so that the moving body and the platen This is a mechanism for moving the moving body (stage) by changing the magnetic force between the convex poles. As the moving mechanism, for example, a mechanism using a ball screw can be adopted.

The stage 21 is arranged so that its longitudinal direction is directed to the stage moving direction, and is supported by the guide 22 so as to be able to reciprocate in a state where straightness is compensated.
In this specification, the moving direction of the stage 21 is defined as the X direction, the horizontal direction perpendicular to the X direction is defined as the Y direction, and the vertical direction is defined as the Z direction. The workpiece W has a square shape and is held on the stage 21 in a posture in which one side is directed in the X direction and the other side is directed in the Y direction. In the following description, the X direction may be referred to as the length direction of the workpiece W, and the Y direction may be referred to as the width direction of the workpiece W.

The moving path of the stage 21 is designed to pass directly under the exposure head unit 10, and the transport system 20 transports the workpiece W to a light irradiation position by the exposure head unit 10 and passes the irradiation position. It is configured as follows. In the process of passing, the pattern of the image formed by the exposure head unit 10 is exposed on the workpiece W.
The exposure head unit 10 is provided on one side of the gate 31 in the X direction, and a plurality of (for example, two) sensors 40 for detecting the front and rear ends of the workpiece W are provided on the other side. That is, the gate 31 provided with the exposure head unit 10 and the sensor 40 is fixedly arranged upstream of the moving path of the stage 21. The exposure head unit 10 and the sensor 40 are connected to a controller (not shown) that controls them.

As shown in FIG. 2, the exposure head unit 10 includes a plurality of (14 in FIG. 2) exposure heads 11 arranged in a substantially matrix of m rows and n columns. Each exposure head 11 incorporates the spatial light modulation element described above and irradiates light with a preset pattern. An exposure area 51 by each exposure head 11 has a rectangular shape with a short side in the sub-scanning direction. Accordingly, as the stage 21 moves, a strip-shaped exposed area 52 is formed on the work W for each exposure head 11.

  As the spatial light modulation element, for example, a digital micromirror device (DMD) 12 shown in FIG. 3 is used. The DMD 12 has a configuration in which fine mirrors (micromirrors) 122 of about 13 μm square that constitute each pixel (pixel) are two-dimensionally arranged on a memory cell (for example, SRAM cell) 121. The number of micromirrors 122 arranged is, for example, 1024 × 768. In each pixel, a rectangular micromirror 122 supported by a support column is provided at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 122. Note that a minute gap of 1 μm or less exists between adjacent micromirrors 122.

When a digital signal is written in the SRAM cell 121 of the DMD 12, each micromirror 122 supported by the support is tilted to any one of ± α degrees with respect to the substrate side on which the DMD 12 is disposed with the diagonal line as the center. Thus, by controlling the tilt of each micromirror 122, the light incident on DMD 12 is reflected in the tilt direction of each micromirror 122.
On / off control of each micromirror 122 is performed by a controller (not shown) connected to the DMD 12. The controller controls the angle of each micromirror 122 of the DMD 12 so as to form a desired pattern on the workpiece W. That is, the angle of each micro mirror 122 of the DMD 12 is selectively controlled according to the pattern of the image to be formed.

As shown in FIG. 4, the exposure head 11 includes a light source unit 13, an incident optical system 14, and a mirror 15 on the light incident side of the DMD 12.
The light source unit 13 includes a light source such as a lamp that emits laser light having a wavelength of 400 nm and a semiconductor laser (laser diode). The light source unit 13 includes an optical fiber that guides output light from the light source. Here, as the optical fiber, for example, a quartz fiber can be used. The emission end portions (light emission points) of the optical fiber are arranged in a line along a direction corresponding to the long side direction of the exposure area 51 to constitute a laser emission unit 131.
The incident optical system 14 is an optical system for causing the laser light emitted from the light source unit 13 to be incident on the DMD 12. In FIG. 4, the incident optical system 14 is schematically shown.
The mirror 15 reflects the laser beam emitted from the incident optical system 14 toward the DMD 12.
As shown in FIG. 5, the incident optical system 14 includes an illumination optical system 141, a microlens array (MLA) 142, and a first imaging optical system 143.

  The illumination optical system 141 is configured by an integrator lens, a collimator lens, a prism, and the like, and enters the laser beam emitted from the laser emission unit 131 of the light source unit 13 into the MLA 142 as parallel light. The MLA 142 is an optical component in which a large number of minute convex lenses (microlens elements) are arranged two-dimensionally. Each microlens element has a one-to-one correspondence with each micromirror 122 of the DMD 12. The first imaging optical system 143 is a reduced imaging optical system that reduces the light collected in a spot shape by the MLA 142 and forms an image on the DMD 12, for example. That is, the DMD 12 and the MLA 142 are aligned and arranged so that the light emitted from one microlens element passes through the first imaging optical system 143 and is condensed on one specific micromirror 122. Has been.

Further, as shown in FIGS. 4 and 5, the exposure head 11 includes a second imaging optical system 16 on the light exit side of the DMD 12. The second imaging optical system 16 is an enlarged imaging optical system that magnifies the image from the DMD 12 by, for example, 5 times and projects it onto the workpiece W.
A controller (not shown) of the exposure apparatus 100 stores digital data (original data) of an image (exposure pattern) to be formed, sends a control signal to the transport system 20, and moves the stage 21 on which the workpiece W is placed. Move at a predetermined speed. At the same time, the controller sends a control signal to the DMD 12 to control the angle of each micromirror 122 at a predetermined timing and sequence so that an exposure pattern based on the original data is formed on the workpiece W. As a result, when the workpiece W coated with resist passes through the exposure area 51, an exposure pattern based on the original data is formed on the workpiece W.

  As described above, in the exposure apparatus 100 according to the present embodiment, the MLA 142 is disposed in the previous stage (light incident side) of the DMD 12 and is spot-shaped on the micromirror 122 of the DMD 12 via the first imaging optical system 143. It has the structure which condenses light. The MLA 142 divides and collects the light from the light source unit 13 that is made into parallel light by each microlens, and the first imaging optical system 143 is a spot collected by the MLA 142 as shown in FIG. Shaped light (laser beam B) is imaged on each micromirror 122 of the DMD 12. At this time, the laser beam B is focused on a diameter of about 2.4 μm on, for example, a 13 μm square micromirror 122. In this manner, since spot-like light is condensed on the micromirror 122 of the DMD 12, light loss can be suppressed and element efficiency can be improved. Hereinafter, this point will be described in detail.

  FIG. 7 is a view showing an exposure head 111 having a conventional configuration in which an MLA is arranged on the light exit side of the DMD. As shown in FIG. 7, the exposure head 111 includes a light source unit 113, an illumination optical system 114, and a mirror 115 on the light incident side of the DMD 112. The exposure head 111 includes a first imaging lens 116, an MLA 117, and a second imaging lens 118 on the light exit side of the DMD 112. Here, the light source unit 113, the illumination optical system 114, and the mirror 115 have the same configuration as the light source unit 13, the illumination optical system 141, and the mirror 15 shown in FIG. The first imaging lens 116 and the second imaging lens 118 are, for example, magnification projection lenses. The first imaging lens 116 may be an equal magnification projection lens or a reduction projection lens.

  In this exposure head 111, the illumination optical system 114 converts the light from the light source unit 113 into parallel light, which is incident on the DMD 112. That is, as shown in FIG. 8, the light from the light source (laser beam B) is irradiated on the entire surface of the DMD 112. As described above, since there is a minute gap between the adjacent micromirrors 1122, the laser beam B incident on this gap is absorbed by the substrate material of the DMD 112 and causes optical loss. Further, there is a possibility that the substrate material of the DMD 112 absorbs the laser beam B to deteriorate the element, or the temperature of the DMD 112 rises to promote the deterioration of the element.

On the other hand, in the present embodiment, as shown in FIG. 6, the laser beam B is irradiated to the gap formed between the micromirrors 122 in order to collect the spot-like light on the micromirrors 122 of the DMD 12. Never happen. Therefore, it is possible to suppress a loss due to light irradiation on the surface other than the micromirror 122 surface, and to improve the light output by the DMD 12 accordingly. Thus, the element efficiency of DMD 12 can be improved.
Furthermore, since it is possible to suppress the substrate material of the DMD 12 from absorbing the laser beam B, it is possible to suppress deterioration of the element. Therefore, the life of the DMD 12 can be extended. As a result, the replacement frequency of the DMD 12 can be reduced and the throughput can be improved.

  Further, in the case where the MLA 117 is arranged on the light emitting side of the DMD 112 as in the exposure head 111 shown in FIG. 7, high accuracy is required for alignment between the DMD 112 and the MLA 117. This is because the micromirrors constituting the DMD 112 and the microlenses constituting the MLA 117 are in a one-to-one relationship, and the reflected light of one micromirror must be accurately incident on one corresponding microlens. . When light from one micromirror is incident on a plurality of microlenses, the resolution performance is lowered and the extinction ratio is lowered.

  In contrast, in the present embodiment, as described above, the light that has passed through one microlens is condensed to a diameter of about 2.4 μm and imaged on the 13 μm-square micromirror 122. Therefore, the required accuracy in alignment between the DMD 12 and the MLA 142 is lower than that in the conventional configuration described above, and the alignment work is facilitated. In addition, unlike the above-described conventional configuration, there is no possibility that light from one micromirror is incident on a plurality of microlenses, so that it is possible to prevent degradation in resolution performance and improve the extinction ratio.

  By the way, the MLA has a configuration in which a plurality of microlenses are arranged, but light incident on a joint portion with an adjacent microlens can become stray light. Therefore, in order to prevent this, for example, as shown in FIG. 9, it is considered that a light blocking member 117a is provided on the light incident side of the MLA 117 to block the incidence of light on the joint. Here, as the light shielding member 117a, for example, a light shielding film containing a chromium-based material can be used. That is, only the light that has passed through the opening formed by the light shielding member 117a is incident on the MLA 117 so as to contribute to the exposure. In this case, in order not to reduce the efficiency of the optical system, it is necessary to shield only the range where the light condensing performance of the MLA 117 is not sufficient, such as the above-described joint, and set the opening as large as possible.

  However, in the case of a configuration in which light from each micromirror of the DMD 112 is incident on a corresponding microlens of the MLA 117 as in the exposure head 111 shown in FIG. 7, if the opening is enlarged, crosstalk occurs between adjacent pixels. May occur. Since the alignment accuracy between the DMD 112 and the MLA 117 is limited, the opening cannot be made larger than a certain extent. That is, as shown in FIG. 9, the light effective area A, which is an area of light that passes through the opening formed by the light blocking member 117a and passes through the microlens, is made narrower than the light transmissive area B of the microlens. I must. Therefore, light loss occurs in the MLA 117. For example, when the cell size of the microlens is 39.73 μm square and the size of the opening is 37 μm square, 30% or more of the light in the area ratio is absorbed by the light shielding member, which directly becomes a light loss.

  On the other hand, in the present embodiment, since spot-like light condensed by the MLA 142 is imaged on the micromirror of the DMD 12, occurrence of crosstalk between adjacent pixels can be suppressed. In addition, light from the light source is incident on the entire surface of the MLA 142. That is, the light is not selectively incident on each microlens of the MLA 142. Therefore, it is not necessary to provide the MLA 142 with a light shielding member corresponding to the above-described light shielding member 117a, or use a light shielding member that shields light only in a range where the light condensing performance of the MLA 142 is insufficient and sets the opening as large as possible. it can. When the light shielding member is eliminated, the output can be improved by about 40%.

  As described above, in the conventional configuration in which the MLA 117 is disposed on the light exit side of the DMD 112, light is kicked by the MLA 117 and the DMD 112, resulting in a significant light loss. On the other hand, in the present embodiment, by arranging the MLA 142 on the light incident side of the DMD 12, light loss due to kicking can be prevented and the efficiency of the optical system can be increased. Therefore, it is possible to increase the light intensity on the exposure surface and improve the throughput.

  Further, in this embodiment, since the loss of light can be reduced, when the light intensity on the exposure surface is equivalent to that of the conventional apparatus shown in FIG. 7, the light intensity from the light source is weakened compared to the conventional apparatus. be able to. That is, the intensity of light incident on the DMD can be weaker than that of the conventional device. Therefore, it is possible to reduce the load on the DMD surface, the DMD hinge, and the like, and to mitigate the temperature rise in the DMD part. Therefore, degradation of DMD can be suppressed. As a result, the DMD replacement frequency can be reduced and the maintenance cost can be reduced.

  In addition, the exposure apparatus 100 in the present embodiment includes a first imaging optical system 143 in order to form an image of the light collected by the MLA 142 on the DMD 12. Since the first imaging optical system 143 is a reduction imaging optical system, the light condensed by the MLA 142 is reduced and imaged on the DMD 12. Therefore, it is possible to employ the MLA 142 having a relatively large condensing spot size, and the MLA 142 can be easily manufactured.

  Furthermore, the exposure apparatus 100 according to the present embodiment includes a second imaging optical system 16 in order to image light modulated by the DMD 12 on the exposure surface. Since the second imaging optical system 16 is an enlargement imaging optical system, the light modulated by the DMD 12 is enlarged and imaged on the exposure surface. The light collected on the micro mirror 122 of the DMD 12 to a diameter of about 2.4 μm, for example, is modulated by the DMD 12 and then magnified, for example, five times by the second imaging optical system 16, and has a diameter of 12 μm on the exposure surface. Become a spot. At this time, the spot size on the exposure surface can be adjusted by adjusting the magnification of the second imaging optical system. Therefore, the resolution requirement can be appropriately satisfied.

(Modification)
In the above embodiment, the case where the DMD 12 which is a reflective spatial light modulation element is used as the spatial light modulation element has been described. However, for example, a transmissive spatial light modulation element using liquid crystal can also be used. However, it is preferable to use a DMD having high light use efficiency as a spatial light modulation element because light from a light source can be efficiently used as exposure light.
In the above embodiment, the case where the reduced imaging optical system is used as the first imaging optical system has been described. However, the first imaging optical system may be a unity imaging optical system, An enlarged imaging optical system may be used. Further, the case where the magnification imaging optical system is used as the second imaging optical system has been described. However, the second imaging optical system may be an equal magnification imaging optical system or a reduction imaging optical system. There may be.

  DESCRIPTION OF SYMBOLS 100 ... Exposure apparatus, 10 ... Exposure head unit, 11 ... Exposure head, 12 ... DMD, 121 ... SRAM cell (memory cell), 122 ... Micromirror, 13 ... Light source, 14 ... Incident optical system, 141 ... Illumination optical system, 142: microlens array (MLA), 143: first imaging optical system, 15: mirror, 16 ... second imaging optical system, 20 ... transport system, 21 ... stage, 22 ... guide, 23 ... electromagnet, 30 ... Installation table, 31 ... Gate (gantry), 32 ... Leg, 51 ... Exposed area, 52 ... Exposed area, W ... Workpiece

Claims (6)

A microlens array in which microlenses that collect ultraviolet light from a light source are arranged in an array; and
A spatial light modulation unit in which a plurality of micromirrors that modulate ultraviolet light collected by the microlens array are arranged in an array via a gap;
A first imaging optical system that images the ultraviolet light collected by the microlens array onto the micromirror of the spatial light modulator so as not to enter the gap;
An exposure apparatus comprising: a second imaging optical system that images the ultraviolet light modulated by the spatial light modulator on a photosensitive material. The spatial light modulator is a digital micromirror device,
The exposure apparatus according to claim 1, wherein the micro mirror is a micro mirror corresponding to the micro lens on a one-to-one basis.   In the first imaging optical system, spot-like ultraviolet light collected by each microlens of the microlens array is spotted on the corresponding micromirror with a spot size smaller than the size of the micromirror. The exposure apparatus according to claim 2, wherein an image is formed.   The exposure apparatus according to claim 1, wherein the second imaging optical system is an enlarged imaging optical system.   The exposure apparatus according to claim 1, wherein the first imaging optical system is a reduction imaging optical system.   Ultraviolet light from the light source is collected by a microlens array in which microlenses are arranged in an array, and the ultraviolet light collected by the microlens array is arranged in an array via a gap. An exposure method characterized in that an image is formed on the micromirror of the spatial light modulator so as not to enter the gap, and the ultraviolet light modulated by the spatial light modulator is imaged on a photosensitive material.

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