JP2018163261A - Image acquisition device, exposure device, and image acquisition method - Google Patents

Abstract

The present invention provides a technique capable of acquiring a highly accurate image in acquiring an image of an imaging target during movement.
An image acquisition apparatus includes: an imaging unit that captures an imaging target; and an imaging region tracking optical system provided so as to be positioned between the imaging unit and the imaging target. Changes the optical path of the light emitted from the imaging target, thereby causing the imaging area, which is an area that can be imaged by the imaging unit, to follow the movement of the imaging target.
[Selection] Figure 4

Description

  The present invention relates to an image acquisition apparatus, an exposure apparatus, and an image acquisition method.

  Japanese Patent Application Laid-Open No. 2004-228561 describes an imaging apparatus for sequentially searching for an alignment mark for each predetermined region on a sample and recognizing a region where the alignment mark exists.

Japanese Patent Laid-Open No. 10-22201

When acquiring an image of an alignment mark, it is common to measure the position of the stage that holds and moves the substrate in real time, stop the stage when it reaches a predetermined position, and take an image by turning on illumination or the like It is. In order to increase the tact of such an apparatus, it is necessary to perform imaging while moving the stage. Here, a CCD (Charge Coupled Device) camera used for imaging captures an image at a predetermined frame rate. In order to acquire an image of the alignment mark, imaging is performed by irradiating the alignment mark with light. Conventionally, an image is acquired by flashing the illumination once during one imaging period (33 [ms] in the case of 30 [fps]). However, with such a method, it is not easy to capture an image with sufficient contrast due to the recent increase in stage speed and the decrease in transmittance due to the reduction in the imaging lens. On the other hand, if an image of an alignment mark is acquired by irradiating light for a long time while moving the substrate, the image acquired due to motion blur (afterimage) is blurred, and there is a problem that adversely affects alignment. there were.

  Therefore, an object of the present invention is to provide a technique capable of reducing blurring of an acquired image in an apparatus that acquires an image of a moving imaging target.

The present invention for solving the above-described problems has the following configuration. That is, the present invention
An image acquisition device that acquires an image of a moving imaging target,
An imaging unit that images the imaging target, and an imaging region tracking optical system provided so as to be positioned between the imaging unit and the imaging target,
The imaging area tracking optical system changes an optical path of light emitted from the imaging target to cause the imaging area, which is an area where the imaging unit can capture an image, to follow the movement of the imaging target.

  According to the present invention, the relative position of the imaging target in the imaging region can be fixed by causing the imaging region to follow the movement of the imaging target during imaging of the imaging target by the imaging unit. According to this, image blur can be suppressed. As a result, highly accurate alignment can be realized.

The present invention also provides:
An illumination unit that irradiates light to the imaging region by flashing multiple times during imaging by the imaging unit;
The imaging unit may generate the image of the imaging target by synthesizing an image formed by the light reflected by the imaging target.

  As a result, the acquired image is obtained by superimposing the same image by the number of times of flash lighting. As a result, the contrast of the alignment mark in the image can be increased, and the alignment accuracy can be further increased.

In addition, the present invention can be realized with the following configuration. That is, the present invention
The imaging region following optical system includes a first optical member that is provided on the imaging unit side and can refract light, and a second optical member that is provided on the imaging target side and can refract light.
The first optical member has a first imaging unit side surface located on the imaging unit side, and a first imaging target side surface located on the imaging target side,
The second optical member is located on the imaging unit side and is parallel to the first imaging target side surface, and a second imaging unit side surface is located on the imaging target side and is parallel to the first imaging unit side surface. An imaging target side surface,
At least one of the first imaging unit side surface and the first imaging target side surface is inclined with respect to the traveling direction of the imaging target,
The optical path of the light emitted from the imaging target may be changed by moving at least one of the first optical member and the second optical member.

Furthermore, the present invention can be realized by the following configurations. That is, the present invention
The imaging area following optical system is formed by a parallel plate having a pair of parallel surfaces and capable of refracting light,
Either one of the pair of parallel surfaces is provided to face the imaging target,
The parallel plate may be capable of changing an inclination angle of the pair of parallel surfaces with respect to a traveling direction of the imaging target.

The present invention can also be specified as an exposure apparatus. That is, the present invention
An image acquisition device;
A stage for holding an exposure object to which the imaging object is attached;
An exposure unit that draws a predetermined pattern on the exposure object by emitting light to the moving exposure object;
Alignment processing for acquiring position information of the exposure object based on the image acquired by the image acquisition device, and performing alignment of the exposure object by controlling the position of the stage based on the position information And an exposure apparatus.

Furthermore, the present invention can be specified as an image acquisition method. That is, the present invention
An image acquisition method for acquiring an image of a moving imaging target,
A first step of acquiring position information of the imaging target;
A second step of determining, based on the position information, whether or not the imaging target exists within an imaging region that is an area where the imaging unit that captures the imaging target is capable of imaging; and
When the imaging target is present in the imaging region, an imaging region tracking optical system provided so as to be positioned between the imaging unit and the imaging target is configured to change an optical path of light emitted from the imaging target. The image acquisition method may include a third step of causing the imaging region to follow the movement of the imaging target by changing.

  Note that the means for solving the above-described problems can be used in appropriate combination.

  ADVANTAGE OF THE INVENTION According to this invention, in the apparatus which acquires the image of the imaging target to move, it becomes possible to reduce the blur of the acquired image.

1 is a side view of an exposure apparatus according to a first embodiment. 1 is a top view of an exposure apparatus according to a first embodiment. It is the schematic of the exposure unit which concerns on 1st Embodiment. 1 is a schematic diagram of an image acquisition device according to a first embodiment. It is a figure which shows the imaging area tracking optical system which concerns on 1st Embodiment. It is a figure which shows the holding member which concerns on 1st Embodiment. It is a figure which shows an optical path in case an imaging area tracking optical system is a 1st attitude | position. It is a figure which shows an optical path in case an imaging area tracking optical system is a 2nd attitude | position. It is a block diagram which shows the control apparatus which concerns on 1st Embodiment. It is a figure which shows an example of an alignment mark. It is a figure which shows the procedure of the alignment method which concerns on 1st Embodiment. It is a figure which shows the procedure of the image acquisition method of the alignment mark which concerns on 1st Embodiment. It is a figure for demonstrating operation | movement of the image acquisition apparatus in the image acquisition of the alignment mark which concerns on 1st Embodiment. It is a figure which shows the image acquired by the image acquisition method of the alignment mark which concerns on 1st Embodiment. It is a figure which shows the image acquired by the image acquisition method of the alignment mark which concerns on a comparative example. It is a figure which shows the modification of the imaging area tracking optical system which concerns on 1st Embodiment. It is a figure which shows the imaging area tracking optical system which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiment described below is one aspect of the present invention and does not limit the technical scope of the present invention.

<First Embodiment>
FIG. 1 is a side view of an exposure apparatus 100 according to the first embodiment. FIG. 2 is a top view of the exposure apparatus 100 according to the first embodiment. The arrows in the figure indicate the X direction, the Y direction, and the Z direction that are orthogonal to each other.

  The exposure apparatus 100 irradiates the upper surface of a substrate W (photosensitive material) on which a layer of a photosensitive material such as a resist is formed with pattern light (drawing light) that is spatially modulated according to CAD data or the like, to form a pattern (for example, It is an apparatus for exposing (drawing) a circuit pattern. The exposure apparatus 100 is also called a drawing apparatus or a direct drawing apparatus.

The substrate W to be processed by the exposure apparatus 100 is, for example, a substrate for a color filter provided in a semiconductor substrate, a printed board, a liquid crystal display device, etc., for a flat panel display provided in a liquid crystal display device, a plasma display device, or the like. Glass substrates, magnetic disk substrates, optical disk substrates, solar cell panels, and the like. In the present embodiment, it is assumed that the substrate W has a substantially rectangular shape. The substrate W is an example of an “exposure target” according to the present invention. Further, as shown in FIG. 9, cross-shaped alignment marks M used for alignment, which will be described later, are formed at the four corners of the upper surface of the substrate W. However, the alignment mark M can have any shape. The alignment mark M only needs to form a predetermined mark by causing contrast in the region when it is used as an image. The alignment mark M may be circular, for example. Further, the alignment mark M may be formed by a hole penetrating the substrate W. The alignment mark M is an example of the “imaging target” according to the present invention.

  As shown in FIG. 1, the exposure apparatus 100 includes a base 1, a support frame 2, a stage 3, a stage drive mechanism 4, an exposure unit 5, an image acquisition device 10, and a control device 9. The support frame 2 is formed in a gate shape that traverses the base 1 in the X-axis direction, and supports the exposure unit 5 and the image acquisition device 10 above the stage 3 (Z direction). Hereinafter, the stage 3, the stage drive mechanism 4, the exposure unit 5, the image acquisition device 10, and the control device 9 will be described.

<Stage 3>
The stage 3 is disposed on the stage driving mechanism 4 and places and holds the substrate W in a horizontal posture on the upper surface thereof. The stage 3 has a substantially flat plate shape. A plurality of suction holes (not shown) are formed on the upper surface of the stage 3. By applying a negative pressure (suction pressure) to the suction holes, the substrate W is attracted to the upper surface of the stage 3. Further, the upper surface of the stage 3 is included in a stage plane S that is a plane parallel to the XY plane. The substrate W and the alignment mark M move in the stage plane S as the stage 3 moves.

<Stage drive mechanism 4>
The stage drive mechanism 4 is disposed on the base 1 and moves the stage 3 relative to the base 1. The stage driving mechanism 4 includes a rotation mechanism 41 that rotates the stage 3 around an axis A (θ direction) parallel to the Z axis, a sub scanning mechanism 43 that moves the stage 3 in the sub scanning direction (X axis direction), and a main scanning direction ( And a main scanning mechanism 42 that moves in the Y-axis direction). The stage driving mechanism 4 outputs position information of the stage 3 to the control device 9 based on an output signal of an encoder disposed on the stage 3 and the like.

<Exposure unit 5>
The exposure unit 5 is an optical device that forms pattern light in accordance with control by the control device 9 and irradiates the pattern light onto the substrate W. As shown in FIG. 2, the exposure unit 5 includes nine exposure units 50. However, the number of exposure units 50 mounted on the exposure unit 5 is not particularly limited, and may be one.

<Exposure unit 50>
The exposure unit 50 is supported by the support frame 2. Specifically, the exposure unit 50 is accommodated in an accommodation box (not shown) that extends to the + Z side and the + Y side of the support frame 2. FIG. 3 is a schematic diagram showing a configuration relating to the exposure unit 50 of the present embodiment. The exposure unit 50 further includes a light source unit 51 and an exposure head 52. In the plurality of exposure units 50, the exposure heads 52 are accommodated in an accommodation box in a state of being arranged in a plurality of rows in the X-axis direction (see FIG. 2).

  The light source unit 51 receives a signal from the control device 9 and outputs laser light, and a laser control system 512 that converts light (spot beam) output from the laser oscillator 511 into light having a uniform intensity distribution. And comprising. The light output from the light source unit 51 is input to the exposure head 52. In addition, it is good also as a structure which divides | segments a laser beam from one light source part 51, and inputs it into the some exposure head 52. FIG.

  The exposure head 52 forms pattern light by spatially modulating light output from the light source unit 51, and irradiates the formed pattern light toward the substrate W on the stage.

<Image Acquisition Device 10>
The image acquisition device 10 acquires an image of the alignment mark M (see FIG. 9) formed on the substrate W in pattern drawing to be described later. FIG. 4 is a schematic diagram of the image acquisition device 10. As shown in FIG. 4, the image acquisition apparatus 10 includes an imaging unit 6, an imaging area following optical system (hereinafter, optical system) 7, and a position measurement unit 8.

  The imaging unit 6 has a function of imaging the stage, and is fixed to the support frame 2 so as to be positioned on the + Y side with respect to the exposure unit 5. However, the imaging unit 6 may be located on the −Y side with respect to the exposure unit 5. The imaging unit 6 includes a CCD (Charge Coupled Device) camera 61 provided so as to face the stage 3, and an illumination unit 62.

  The CCD camera 61 is provided so that the optical axis A1 is parallel to the Z axis. That is, the optical axis A1 is perpendicular to the stage plane S. The CCD camera 61 forms an image of light emitted from an object located within a predetermined angle of view on a light receiving surface 61a of an internal image sensor (CCD) by a lens (not shown), and charges the light and darkness of the image with light. The object to be imaged is picked up by photoelectrically converting it into an amount, and sequentially reading it and converting it into an electrical signal. This imaging by the CCD camera 61 is executed at a predetermined frame rate corresponding to the shutter speed. The frame rate of the CCD camera 61 is, for example, 30 [fps]. In this case, if one imaging period is T, T = 1/30 [fps] = 33 [ms]. However, the imaging cycle of the CCD camera 61 is not limited to the above. The CCD camera 61 is in a state where the shutter is open during the imaging period. That is, the light receiving element is exposed throughout the imaging period. The CCD camera 61 generates an image by synthesizing an image formed on the light receiving surface 61a of the light receiving element during the imaging period. Further, the CCD camera 61 forms a predetermined range of the imaging region F on the stage plane S according to the angle of view. The imaging target on the stage is imaged by the CCD camera 61 when it is within the imaging area F. The number of CCD cameras 61 provided in the imaging unit 6 is not limited, and two CCD cameras 61 may be provided, for example. The CCD camera 61 corresponds to the “imaging unit” of the present invention.

  The illumination unit 62 is illumination that flashes in accordance with the control of the control device 9. The illumination unit 62 is, for example, LED illumination that irradiates the imaging region F by turning on the LED light source. The illuminating unit 62 irradiates the imaging area F with light by being controlled by the optical system 7 described later. Thereby, the imaging object in the imaging area F reflects light. The flash is turned on when the illumination unit 62 is lit for a very short time. The flash lighting time is, for example, 1 [μs].

  The imaging unit 6 operates the CCD camera 61 and the illumination unit 62 using the position information of the stage 3 output from the control device 9 as a trigger. The imaging unit 6 flashes the illumination unit 62 for a short time within the imaging period of the CCD camera 61. Then, the CCD camera 61 images the imaging target by causing the light reflected by the imaging target in the imaging area F to form an image on the light receiving surface 61a of the light receiving element. Accordingly, the image generated by the imaging unit 6 is a composite of images formed while the illumination unit 62 is lit during the imaging period.

  The optical system 7 controls the light reflected from the imaging target and the light emitted from the illumination unit 62, so that the imaging area F of the CCD camera 61 is applied to the alignment mark M that is the imaging target attached on the substrate W. Has a function to follow. The optical system 7 also has a function of causing the area irradiated with light from the illumination unit 62 to follow the imaging area F. The optical system 7 is fixed to the support frame 2 so as to be positioned between the CCD camera 61 and the stage 3 in the Z direction. That is, the optical system 7 is disposed above the stage 3 and below the CCD camera 61. Furthermore, the optical system 7 is disposed on the optical axis A1 of the CCD camera 61.

FIG. 5 is a cross-sectional view of the optical system 7 in a plane parallel to the YZ plane. As shown in FIG. 5, the optical system 7 includes a first optical member 71 and a second optical member 72 that are spaced apart in the Z direction, and the first optical member 71 with respect to the second optical member 72 in the Y direction. And a holding member 74 (to be described later) that is slidably held on the head. The first optical member 71 and the second optical member 72 are optical prisms formed of a glass material, have the same shape, and the refractive index of both is the same. In addition, the material of the 1st optical member 71 and the 2nd optical member 72 is not limited to a glass material, The resin material with the high transmittance | permeability used for a general lens component etc. may be sufficient.

  The first optical member 71 is disposed on the + Z side with respect to the second optical member 72, and is formed in a substantially triangular shape when viewed in the X-axis direction. Specifically, the first optical member 71 is located on the most + Z side in the first optical member 71 and is parallel to the stage plane S (XY plane), and the first imaging unit side surface 711 and the first imaging unit side surface 711. A first imaging target side surface 712 that extends from an end portion located on the −Y side of the first imaging target and is inclined clockwise by a predetermined angle α (0 <α <π / 2) with respect to the first imaging unit side surface 711; A first vertical surface 713 parallel to the ZX plane. Accordingly, the first imaging target side surface 712 is inclined with respect to the main scanning direction, that is, the Y direction that is the traveling direction of the alignment mark M. The first imaging unit side surface 711 is parallel to the XY plane, and is orthogonal to the optical axis A1 of the CCD camera 61.

  The second optical member 72 is the same as the first optical member 71 rotated 180 ° around the X axis. The second optical member 72 includes a second imaging unit side surface 721 that faces the first imaging target side surface 712 and is parallel to the first imaging target side surface 712, and an end on the + Y side of the second imaging unit side surface 721 (that is, the lower end). ) To the −Y side and parallel to the stage plane S (XY plane), and a second vertical plane 723 parallel to the ZX plane. The first imaging target side surface 712 and the second imaging unit side surface 721 have a positive inclination on the YZ plane.

  The first optical member 71 and the second optical member 72 are separated from each other in the Y direction and the Z direction, and each is disposed on the optical axis A1 of the CCD camera 61. Since the first optical member 71 and the second optical member 72 are separated from each other in the Y direction and the Z direction, the region sandwiched between the first imaging target side surface 712 and the second imaging unit side surface 721 is made of the atmosphere. An air layer 73 is formed.

  FIG. 6 is a view showing the holding member 74 in the optical system 7. The holding member 74 includes a slide member 741 on which the first optical member 71 is mounted, and a base member 742 that is fixed to the support frame 2 and supports the slide member 741 so as to be movable in the Y direction. The slide member 741 can be moved in the Y direction by a known technique such as a ball screw, so that the first optical member 71 is held by the holding member 74 so as to be slidable in the Y direction.

また、Ｎ＞１であることから、β＞αとなる。これにより、第１撮像対象側面７１２において光軸Ａ１に対して＋Ｙ側に屈折する。より詳細には、光Ｌ０は、第１撮像対象側面７１２を境に、光軸Ａ１に対して（β−α）分＋Ｙ側に傾斜して空気層７３を進行する。そして、光Ｌ０は、第１撮像対象側面７１２と平行な第２撮像部側面７２１に対しては入射角βで入射するため、光は屈折角αで屈折する。その結果、光Ｌ０は光軸Ａ１と平行となり、第２光学部材７２を進行する。そして、進行方向に垂直な第２撮像対象側面７２２では屈折せずに、大気中へ直進する。 7A and 7B are diagrams illustrating an example of an optical path in the image acquisition device 10. The optical system 7 is in a first posture state in which the first optical member 71 shown in FIG. 7A is positioned closest to the −Y side by translating the first optical member 71 in the Y direction during image acquisition to be described later. And the first optical member 71 shown in FIG. 7B changes its posture between the second posture where the first optical member 71 is located on the most + Y side. Here, an intersection point between the light receiving surface 61a of the CCD camera 61 and the optical axis A1 is defined as an imaging point P0. Solid lines indicated by reference signs R1 and R2 in the drawing are light rays indicating the optical path of the light L0 emitted from the imaging point P0 to the atmosphere along the optical axis A1. As shown in the light ray R1 of FIG. 7A, in the first posture, the light L0 is not refracted because it is incident on the first imaging unit side surface 711 perpendicular to the traveling direction at an incident angle of 0, and the first optical Go straight through the member 71. And since it injects with the incident angle (alpha) with respect to the 1st imaging object side surface 712 inclined (alpha) with respect to the 1st imaging part side surface 711, it refracts | refracts at the refraction angle (beta) and is radiate | emitted in air | atmosphere. Here, β depends on the refractive index N (> 1) and the angle α of the first optical member 71 and the second optical member 72 with respect to the atmosphere. The relationship between α and β is expressed by the following equation (1).

Further, since N> 1, β> α. Accordingly, the first imaging target side surface 712 is refracted to the + Y side with respect to the optical axis A1. More specifically, the light L0 travels in the air layer 73 while being inclined toward the optical axis A1 by (β−α) + Y side with respect to the first imaging target side surface 712. The light L0 is incident at the incident angle β on the second imaging unit side surface 721 parallel to the first imaging target side surface 712, and thus the light is refracted at the refraction angle α. As a result, the light L0 is parallel to the optical axis A1 and travels through the second optical member 72. Then, the second imaging target side surface 722 perpendicular to the traveling direction travels straight into the atmosphere without being refracted.

  Thus, since the first imaging unit side surface 711 and the second imaging target side surface 722 are parallel and the first imaging target side surface 712 and the second imaging unit side surface 721 are parallel, the first imaging unit side surface 722 and the second imaging unit side surface 721 are parallel. The light L0 incident on the optical system 7 is emitted to the stage plane S in parallel with the optical axis A1. Here, a point where the light L0 reaches on the stage plane S which is located on the −Z side of the second optical member 72 and parallel to the XY plane is defined as a point P1. Since the light L0 is inclined to the + Y side by (β−α) with respect to the optical axis A1 in the air layer 73, the point P1 is located on the + Y side with respect to the optical axis A1.

  In the second posture, the first optical member 71 translates to the + Y side, so that the first imaging target side surface 712 and the second imaging unit side surface 721 are in the Y direction and They are separated in the Z direction. In this state, the light L0 travels like a light ray R2 shown in FIG. 7B. Even in the second posture, the inclination angle of the first imaging target side surface 712 and the second imaging unit side surface 721 is α, which is the same as in the first posture, so that the light L0 is parallel to the optical axis A1. And emitted from the optical system 7. As shown in FIG. 7B, in the second posture, the first imaging target side surface 712 and the second imaging unit side surface 721 are moved in parallel to the + Y side than in the first posture. Is greater than the distance D1 in the first posture. Therefore, the distance that the light L0 travels in the air layer 73 in the second posture, that is, the distance that the light L0 travels by tilting to the -Y side by (β−α) relative to the optical axis A1 is the first. It is larger than the posture. As a result, the light L0 reaches a point P2 that is further offset to the + Y side from the point P1.

  As described above, the optical system 7 translates the first optical member 71 in the Y direction because the first imaging target side surface 712 and the second imaging unit side surface 721 that are parallel to each other are inclined with respect to the Y direction. Thus, the position where the light L0 reaches can be moved in the Y direction. In the optical system 7, the first optical member 71 and the second optical member 72 do not have to be separated from each other in the first posture. That is, in the first posture, the first imaging target side surface 712 and the second imaging unit side surface 721 may be in contact with each other.

  Here, as shown by the light rays R1 and R2, the light emitted from the point P1 in parallel with the optical axis A1 in the first posture and the light emitted from the point P2 along the optical axis A1 in the second posture. Both lights reach the image point P0. Thereby, when in the first posture, the vicinity of the point P1 becomes the imaging region F, and when in the second posture, the vicinity of the point P2 becomes the imaging region F. That is, the optical system 7 can move the imaging region F in the Y direction by moving the first optical member 71 to change the optical path of the light emitted from the imaging target.

Further, as indicated by the light ray R3 in FIG. 4, the image acquisition device 10 causes the light emitted from the illumination unit 62 to enter the first optical member 71 along the optical axis A1. Therefore, the light emitted from the illumination unit 62 is irradiated to the same position as the light L0 emitted from the imaging point P. Thereby, the image acquisition device 10 can irradiate the imaging region F regardless of the posture of the optical system 7.

<Position measuring unit 8>
The position measuring unit 8 measures the position of the first optical member 71. As shown in FIG. 4, the position measuring unit 8 includes a spot beam light source 81 and an analog position sensor 82. The position measuring unit 8 emits laser light from the spot beam light source 81 toward the optical system 7, receives light refracted by the first optical member 71 by the analog position sensor 82, and receives a light receiving position (specifically, the refracted light). Specifically, the position of the first optical member 71 is measured by measuring the Y position along the main scanning direction. The position information of the first optical member 71 is output to the control unit.

<Control device 9>
The control device 9 controls the stage driving mechanism 4, the exposure unit 5, and the image acquisition device 10 to scan the irradiation light from the exposure head 52 on the surface of the substrate W supported by the stage 3, and pattern the surface of the substrate W. Execute operations to form The control device 9 is connected to the components of the exposure apparatus 100 such as the stage drive mechanism 4, the exposure unit 5, and the image acquisition device 10 by bus wiring, a network line or a serial communication line, and the operation of each of these components is controlled. Control.

  FIG. 8 is a block diagram showing the control device 9 of the present embodiment. As shown in FIG. 8, the control device 9 includes a CPU 91 that functions as an arithmetic circuit, a read-only ROM 92, and a storage unit 93 that is a nonvolatile recording medium.

  The CPU 91 is a computer that performs calculations on various data stored in the storage unit 93 by reading and executing a program stored in the ROM 92. The drawing control unit 911, the image acquisition control unit 912, and the alignment processing unit 913 are functions realized by the CPU 91 operating according to a program. However, some or all of these elements may be realized by a logic circuit or the like.

  The drawing control unit 911 moves the rotation mechanism 41, the sub-scanning mechanism 43, and the main scanning mechanism 42 based on the pattern data stored in the storage unit 93 and the position information of the stage 3 output from the stage driving mechanism 4. While controlling, the pattern light modulated according to the position of the substrate W is output from the exposure head 52, thereby forming a drawing pattern on the substrate W.

  The image acquisition control unit 912 is stored in the storage unit 93 and the position information of the stage 3 output from the stage drive mechanism 4, the position information of the first optical member 71 output from the optical system 7 and the position measurement unit 8. The image of the alignment mark M is acquired by controlling the image acquisition device 10 based on the position information of the alignment mark M.

  The alignment processing unit 913 performs alignment processing described later based on the position information of the alignment mark M stored in the storage unit 93 and the image of the alignment mark M acquired by the image acquisition device 10. The alignment processing unit 913 corresponds to the “alignment processing unit” of the present invention.

As described above, the storage unit 93 stores pattern data indicating a pattern to be drawn on the substrate W and position information of the alignment mark M on the substrate W. For example, the pattern data is obtained by converting image data generated by CAD (computer aided design) or the like into data indicating a drawing pattern.

In the present embodiment, the pattern data may be a single image (an image indicating a pattern to be formed on the entire surface of the substrate W). For example, the exposure head 52 is obtained from the pattern data indicating the single image. An image of a part in which each is responsible for drawing may be individually generated for each exposure head 52.

<Drawing method>
Next, a pattern drawing operation on the substrate W by the exposure apparatus 100 according to the present embodiment will be described. In pattern drawing, first, the drawing control unit 911 controls the stage driving mechanism 4 to position the stage 3 at a position (initial position) at which exposure to the substrate W is started. When the positioning is completed, the stage driving mechanism 4 starts moving the stage 3 of the drawing control unit 911 to one side (for example, + Y side) in the Y direction that is the main scanning direction. Then, each of the plurality of optical heads irradiates the surface of the substrate W moving in the main scanning direction together with the stage 3 with a pattern of light according to the drawing data. The exposure apparatus 100 forms a pattern on the substrate W without a gap by repeating pattern drawing accompanying movement in the main scanning direction and movement in the sub-scanning direction.

<Alignment method>
In the exposure apparatus 100 having such a configuration, there is a possibility that the initial position fluctuates and the optical axis shift of the exposure head 52 occurs due to insufficient reproducibility of the stage 3 during pattern drawing. Therefore, in order to form a multilayer pattern by overlapping and drawing patterns on the substrate W, it is necessary to perform alignment (position alignment) of the substrate W before starting pattern drawing or between pattern drawing. By performing alignment, it is possible to realize a highly accurate overlay of multilayer patterns.

  As described above, the alignment marks M shown in FIG. The alignment of the substrate W is executed by the alignment processing unit 913 of the control device 9 adjusting the stage position based on the image of the alignment mark M acquired by the image acquisition device 10. Hereinafter, the procedure of the alignment method according to the present embodiment will be described with reference to FIG. The alignment method described below is executed in parallel with the pattern drawing by the drawing control unit 911.

  First, the image acquisition control unit 912 causes the image acquisition device 10 to acquire an image of the alignment mark M (step S1). Next, the position coordinate of the center of the alignment mark M in the acquired image is detected (step S2). Any image processing technique can be used to detect the center position of the alignment mark M. Next, the position coordinates of the detected alignment mark M are stored in the storage unit 93 (step S3). After storing the coordinates of the alignment mark M detected in step S3, in step S4, the alignment processing unit 913 controls the stage drive mechanism 4 based on the coordinates of the alignment mark M to adjust the stage position. The substrate W is positioned (step S4). Thereby, the exposure apparatus 100 continues pattern drawing on the aligned substrate W. In step S4, the drawing pattern may be corrected in addition to the alignment by the position control of the stage 3.

[Image acquisition method]
In step S2, in order to accurately detect the position coordinates of the alignment mark M by image processing, it is preferable that the image acquired in step S1 is less blurred and the alignment mark M in the image has a high contrast. The image acquisition apparatus 10 according to the present embodiment can acquire an image with less blur and high contrast. Hereinafter, the image acquisition method in step S1 will be described with reference to FIG.

During pattern drawing, the substrate W is moved in the Y direction with respect to the imaging region F of the CCD camera 61 by the movement of the stage 3 in the Y direction. That is, the image acquisition is executed while the stage 3 is moving in the Y direction. First, the image acquisition control unit 912 acquires the position information of the substrate W based on the position information of the stage 3 (Step S11). Next, based on the position information of the substrate W and the position information of the alignment mark M on the substrate W stored in advance in the storage unit 93, the alignment mark M reaches the imaging area F of the CCD camera 61 during pattern drawing. It is determined whether or not (step S12). When it is determined that the alignment mark M has not reached the imaging region F (step S12—NO), the process returns to step S11. When it is determined that the alignment mark M has reached the imaging area F (step S12—YES), the optical system 7 is controlled to cause the imaging area F to follow the alignment mark M, and the CCD camera 61 causes the alignment mark M to be aligned. Is imaged (step S13).

  FIG. 12 is a timing chart showing the operation of the image acquisition device 10 when acquiring one image in step S13. When the image acquisition device 10 determines that the alignment mark M has reached the imaging region F based on the position information of the substrate W, the image acquisition device 10 images the alignment mark M with the CCD camera 61. As described above, the CCD camera 61 generates an image by synthesizing the image formed on the light receiving surface 61a of the light receiving element during the imaging period. The image acquisition apparatus 10 according to the present embodiment flashes the illumination unit 62 a plurality of times at regular time intervals during the imaging period. In each flash lighting, the substrate W is exposed to light for a minute time. Thereby, the light reflected by the substrate W when each flash is turned on forms an image on the light receiving element, and the images are combined to generate one image.

  In addition, the image acquisition device 10 controls the optical system 7 to cause the imaging region F to follow the alignment mark M throughout the imaging period. Specifically, the image acquisition apparatus 10 controls the position of the first optical member 71 based on the position information of the stage 3 output from the stage drive mechanism 4, and sets the imaging region F of the stage 3 during the imaging period. The stage 3 is moved in the traveling direction at the moving speed Vs.

  For example, when the stage 3 and the alignment mark M are moved in the + Y direction, the image acquisition apparatus 10 causes the imaging region F to follow the alignment mark M by moving the first optical member 71 in the + Y direction. Note that the moving speed of the first optical member 71 at this time depends on the angle α, the refractive index N, and the moving speed Vs of the stage 3. Thereby, since the movement of the substrate W and the movement of the imaging region F are synchronized, the imaging region F can be made to follow the alignment mark M. Here, if the imaging period is T, the distance that the stage 3 moves in the + Y direction during the imaging period is Vs · Tf because the moving speed of the stage 3 is Vs. The image acquisition apparatus 10 moves the imaging region F in the + Y direction by a distance of Vs · T at a speed of Vs during the imaging period. In this way, the relative position and orientation of the alignment mark M in the imaging region F can be fixed throughout the imaging period.

  FIG. 13 is a diagram showing an image of the alignment mark M acquired in step S13. As described above, the relative position and orientation of the alignment mark M in the imaging region F are fixed throughout the imaging period. Therefore, the same image is formed when each flash is turned on. As a result, the acquired image is obtained by superimposing the same image by the number of times of flash lighting. As a result, a high-contrast image with less image blur as shown in FIG. 13 can be obtained. Thereby, since the detection accuracy of the center position of the alignment mark M is enhanced in the image processing in step S2, highly accurate alignment can be realized. Further, the image acquisition control unit 912 feedback-controls the position of the first optical member 71 based on the position information of the first optical member 71 output from the position measurement unit 8, thereby determining the position of the imaging region F in real time. Correct with. Thereby, the precision of the synchronization of the imaging region F and the alignment mark M can be improved. As a result, it is possible to further reduce blurring of the acquired image.

[Action / Effect]
As described above, the image acquisition device 10 according to the present embodiment changes the optical path of the light emitted from the alignment mark M by the optical system 7 when acquiring an image of the moving alignment mark M, thereby capturing the imaging region. F can follow the movement of the alignment mark M. Thereby, it is possible to suitably suppress the image blur of the alignment mark M. As a result, the detection accuracy of the position coordinates of the alignment mark M can be increased, and highly accurate alignment can be realized.

  Furthermore, the image acquisition apparatus 10 according to the present embodiment causes the illumination unit 62 to flash light a plurality of times during the imaging period of the CCD camera 61, and images the light reflected by the alignment mark M during each flash lighting. By synthesizing, an image of the alignment mark M is generated. As a result, the generated image is obtained by superimposing the same image by the number of times of flash lighting. As a result, the contrast of the alignment mark M in the image can be increased, and the alignment accuracy can be further increased.

  The image acquisition device 10 can acquire an image while the stage 3 is driven and the substrate W is moved. Therefore, according to the exposure apparatus 100 including the image acquisition apparatus 10 according to the present embodiment, the time required for alignment can be shortened.

  In the optical system 7, the first imaging unit side surface 711 and the second imaging target side surface 722 are parallel, and the first imaging target side surface 712 and the second imaging unit side surface 721 are parallel, whereby the optical axis A <b> 1. The light L0 incident on the optical system 7 in parallel with the light is emitted to the stage plane S in parallel with the optical axis A1. As a result, the acquired image can be prevented from being distorted by the optical system 7.

  The optical system 7 may move the first optical member 71 in the Z direction. Thereby, since the distance between the first imaging target side surface 712 and the second imaging unit side surface 721 changes, the imaging region F can be moved.

  Further, the optical system 7 may be configured such that at least one of the first optical member 71 and the second optical member 72 can be moved. Thereby, the optical path of the light emitted from the alignment mark M can be changed. The optical system 7 may move the second optical member 72 instead of the first optical member 71, or may move both the first optical member 71 and the second optical member 72. When the second optical member 72 is movable, the imaging region F can be made to follow the alignment mark M by moving the second optical member 72 in a direction opposite to the traveling direction of the stage 3.

  The optical system 7 includes an alignment mark M at least one of the first imaging unit side surface 711 (and the second imaging target side surface 722) and the first imaging target side surface 712 (and the second imaging unit side surface 721). What is necessary is just to incline with respect to the advancing direction. Thereby, the imaging region F can be moved in the traveling direction of the alignment mark M. FIG. 15 is a diagram illustrating a modification of the optical system 7. In the optical system 7, for example, as illustrated in FIG. 15, the first imaging unit side surface 711 and the second imaging target side surface 722 that are parallel to each other may be inclined with respect to the traveling direction of the alignment mark M.

Further, the present invention is not limited to the first optical member 71 and the second optical member 72 having the same shape. As long as the imaging region F can follow the alignment mark M, the first optical member 71 and the second optical member 72 may have different shapes. Further, the optical characteristics of the first optical member 71 and the second optical member 72 are not limited to the same, and may be appropriately changed.
[Comparative example]
FIG. 14 is a diagram illustrating an image of the alignment mark M acquired by the image acquisition method according to the comparative example. In the comparative example, the control of the optical system 7 is not performed, and the position of the imaging region F is fixed. That is, in the comparative example, an image is acquired without causing the imaging region F to follow the alignment mark M. Here, assuming that the time interval during which the illumination unit 62 lights the flash is Tf, the distance that the stage 3 moves in the + Y direction during the flash lighting is Vs · Tf because the moving speed of the stage 3 is Vs. Therefore, in each flash lighting, the alignment mark M is imaged with a shift of Vs · Tf. As a result, as shown in the figure, the image acquired in the comparative example is displayed with the alignment mark M shifted. In such an image, it is difficult to accurately detect the center position of the alignment mark M.

  On the other hand, if the flash is turned on only once during the imaging period in order to avoid image shift, sufficient contrast cannot be obtained. Further, if the illumination is turned on for a long time during the imaging period in order to obtain contrast, motion blur may occur and the image may be blurred. As a result, in any of the above cases, it is difficult to accurately detect the center position of the alignment mark M. On the other hand, according to the image acquisition device 10 according to the present embodiment, it is possible to suppress image shift and blur and to increase the contrast of the alignment mark M in the image.

Second Embodiment
Note that the imaging region following optical system according to the present invention may be configured by a parallel plate 75 as shown in FIG. The parallel plate 75 constituting the optical system 7A according to the second embodiment is formed of a glass material and is rotatably supported by the support frame 2. The parallel plate 75 is opposite to the imaging target and has a third imaging target side surface 752 that is a surface on which light emitted from the imaging target is incident, and light incident from the third imaging target side surface 752 is emitted to the outside of the parallel plate 75. And a third imaging unit side surface 751 that is a surface to be operated. The third imaging target side surface 752 and the third imaging unit side surface 751 are formed in parallel to each other.

  As illustrated in FIG. 16, the optical system 7A according to the second embodiment rotates the parallel plate 75 around the X axis, and thereby advances the alignment mark M on the third imaging target side surface 752 and the third imaging unit side surface 751. The arrival point of the light L0 that reaches the stage plane S from the image formation point P of the CCD camera 61 can be moved by changing the degree of inclination with respect to the direction. The amount of movement of the arrival point of the light L0 changes according to the amount of rotation of the parallel plate 75. Thereby, by adjusting the rotation amount and rotation speed of the parallel plate 75 according to the position information of the stage 3, the imaging region F can be made to follow the alignment mark M with a simpler configuration than in the first embodiment. .

  In the present invention, the direction in which the imaging region F follows is not limited to the main scanning direction. The direction in which the imaging region F follows may be the traveling direction of the alignment mark M.

  Further, the image acquisition device 10 according to the present invention can be applied as long as the alignment mark M moves relative to the imaging unit 6. For example, the image acquisition apparatus 10 can be suitably used in an exposure apparatus that performs pattern drawing by moving the exposure unit 5 and the imaging unit 6 with respect to the fixed stage 3.

<Others>
The contents described in the above embodiments and modifications can be implemented in combination as much as possible.

DESCRIPTION OF SYMBOLS 100 ... Exposure apparatus 5 ... Exposure part 10 ... Image acquisition apparatus 6 ... Imaging unit 61 ... CCD camera (imaging part)
62... Illumination unit 7... Imaging region tracking optical system 71... First optical member 711... First imaging unit side surface 712. ... Second imaging unit side surface 722 ... Second imaging target side surface 73 ... Air layer 8 ... Position measurement unit 9 ... Control device 91 ... CPU
911: Drawing control unit 912 ... Image acquisition control unit 913 ... Alignment processing unit W ... Substrate (exposure target)
M: Alignment mark (imaging target)

Claims (6)

An image acquisition device that acquires an image of a moving imaging target,
An imaging unit that images the imaging target, and an imaging region tracking optical system provided so as to be positioned between the imaging unit and the imaging target,
The imaging area tracking optical system changes an optical path of light emitted from the imaging target, thereby causing an imaging area, which is an area where the imaging unit can capture an image, to follow the movement of the imaging target.
Image acquisition device. An illumination unit that irradiates light to the imaging region by flashing multiple times during imaging by the imaging unit;
The imaging unit generates an image of the imaging target by synthesizing an image formed by the light reflected by the imaging target.
The image acquisition apparatus according to claim 1. The imaging region following optical system includes a first optical member that is provided on the imaging unit side and can refract light, and a second optical member that is provided on the imaging target side and can refract light.
The first optical member has a first imaging unit side surface located on the imaging unit side, and a first imaging target side surface located on the imaging target side,
The second optical member is located on the imaging unit side and is parallel to the first imaging target side surface, and a second imaging unit side surface is located on the imaging target side and is parallel to the first imaging unit side surface. An imaging target side surface,
At least one of the first imaging unit side surface and the first imaging target side surface is inclined with respect to the traveling direction of the imaging target,
By changing at least one of the first optical member and the second optical member, the optical path of the light emitted from the imaging target is changed.
The image acquisition device according to claim 1. The imaging area following optical system is formed by a parallel plate having a pair of parallel surfaces and capable of refracting light,
Either one of the pair of parallel surfaces is provided to face the imaging target,
The parallel plate can change an inclination angle of the parallel pair of surfaces with respect to a traveling direction of the imaging target.
The image acquisition device according to claim 1. The image acquisition device according to any one of claims 1 to 4,
A stage for holding an exposure object to which the imaging object is attached;
An exposure unit that draws a predetermined pattern on the exposure object by emitting light to the moving exposure object;
Alignment processing for acquiring position information of the exposure object based on the image acquired by the image acquisition device, and performing alignment of the exposure object by controlling the position of the stage based on the position information Means,
Exposure device. An image acquisition method for acquiring an image of a moving imaging target,
A first step of acquiring position information of the imaging target;
A second step of determining, based on the position information, whether or not the imaging target exists within an imaging region that is an area where the imaging unit that captures the imaging target is capable of imaging; and
When the imaging target is present in the imaging region, an imaging region tracking optical system provided so as to be positioned between the imaging unit and the imaging target is configured to change an optical path of light emitted from the imaging target. Changing the imaging region to follow the movement of the imaging target by changing, and
Image acquisition method.

Images