JP2013021164A - Alignment mark detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a work alignment mark (work mark) even when appearance thereof varies.SOLUTION: An operator sets illumination means 10c, which is dark-field illumination means, at a height where a work mark is clearly visible, takes an image of a work mark WAM on a work-piece W with an alignment microscope 10, and registers the work mark WAM as a registered pattern in a memory unit 11b of a controller 11. When the work mark is detected, an alignment mark detection unit 11c of the controller 11 searches the work-piece W with the alignment microscope 10 while changing the height of the illumination means 10c with illumination-means moving means 5, and obtains a degree of matching by comparing a pattern on the work-piece W and the registered pattern. When a pattern with a high matching degree is detected, the alignment mark detection unit 11c detects this pattern as the work mark. An alignment control unit 11e aligns a mask M and the work-piece W by using this work mark.

Description

  The present invention detects a mask alignment mark (mask mark) formed on a mask and a work alignment mark (work mark) formed on a workpiece so that the two are in a preset positional relationship. The present invention relates to an apparatus for detecting a work alignment mark, which is used in an exposure apparatus that performs alignment (alignment) and irradiates light onto a work through a mask.

An exposure apparatus is used in a process of manufacturing a pattern of a semiconductor element, a printed circuit board, a liquid crystal substrate or the like by photolithography. The exposure apparatus aligns the mask on which the mask pattern is formed and the work to which the pattern is transferred in a predetermined positional relationship, and then irradiates light including exposure light through the mask. As a result, the mask pattern is transferred (exposed) to the workpiece.
The alignment of the mask and the workpiece in the exposure apparatus is generally performed as follows (see, for example, Patent Document 1).
A mask mark formed on the mask and a work mark formed on the workpiece are detected by an alignment microscope. The detection data is subjected to image processing, the respective position coordinates are obtained, and the mask or workpiece is moved so that the positions of the two are in a preset positional relationship. The mask and workpiece must be aligned in two directions (X direction and Y direction) and in the rotational direction (θ direction) in the plane. Therefore, two or more mask marks and work marks are formed.

FIG. 10 shows a schematic configuration of an alignment microscope 10 that detects a workpiece mark. As described above, two or more mask marks and work marks are formed, and accordingly, two or more alignment microscopes 10 are provided accordingly. In the figure, only one (one) is shown. ing. The alignment microscope 10 includes a half mirror 10a, lenses L1 and L2, and a CCD camera 10b.
Reference numeral 11 denotes a control unit that performs image processing and the like, 12 denotes a monitor, and W denotes a work on which a work mark WAM is formed.
In the figure, the work mark WAM is detected (pattern search) as follows.

A) Registration of Work Mark Prior to detection of the work mark WAM, first, a work mark pattern to be detected is registered in the control unit 11.
As the work mark WAM, for example, a cross-shaped mark shown in FIG. 11A is used. As shown in FIG. 11B, the control unit 11 has a cross-shaped work in units of one pixel of the monitor. It is registered as one pattern including the mark and its background. That is, in order to facilitate the description in FIG. 5, the number of pixels is 5 × 5, but a pattern is registered in which 5 pixels at the center of the screen are black in a cross shape and 20 pixels around the pixel are white.
Specifically, a sample substrate on which a work mark WAM to be detected is formed is placed under an alignment microscope and illuminated with illumination light.
The registered work mark WAM is detected by an alignment microscope (for example, 3 times magnification) 10. On the monitor 12, a range (for example, a range of 15 mm × 15 mm as shown in FIG. 12) that can be captured by the alignment microscope 10 and processed by the control unit 11 is displayed.

Next, the work mark WAM is surrounded on the monitor 12 by a virtual line for registering the work mark (dotted line in FIG. 12) on the monitor 12 so that the entire work mark WAM to be registered enters, and the work mark WAM is registered in the control unit 11. The control unit 11 stores the work mark WAM based on the contrast in units of pixels surrounded by the virtual line. Thereby, the registration work of the work mark WAM is completed.
The size of the workpiece mark WAM varies depending on the type of workpiece, user, and process. For example, it is often used that the size of the virtual line surrounding the workpiece mark WAM is 200 μm to 700 μm as shown in FIG. Is called.
The shape of the work mark WAM also varies for the same reason as described above, and is not limited to the cross shape as shown in FIG. There are many such as a round shape as shown in FIG. 13 (a), and a set of regular patterns as an alignment mark as shown in FIG. 13 (b). In any case, the registration range is set so that the entire pattern of one work mark is included.

B) Pattern search Next, an actual work mark WAM is detected. The sample substrate used for the work mark pattern registration is removed from under the alignment microscope, and the substrate (work) on which the pattern is actually formed is placed. The magnification of the microscope is the same magnification (3 times) that the pattern is registered above.
As shown in FIG. 10, the illumination light is irradiated onto the workpiece mark WAM on the workpiece W through the half mirror 10a of the alignment unit 10, and the workpiece mark WAM is received by the CCD camera 10b. Then, the image of the work mark WAM displayed on the monitor 12 is input to the control unit 11 and converted into coordinate data in units of pixels of the monitor 12.
The control unit 11 compares the registered pattern with the image of the received work mark WAM. For example, if the received image (detection pattern) of the work mark WAM is the detection pattern A shown in FIG. 11C, it is recognized as a score (correlation value) 60 because it matches 60% with the registered pattern.
Similarly, when the received image (detection pattern) of the work mark WAM is the detection pattern B shown in FIG. Further, in the case of the detection pattern C shown in FIG. 11E, the received image of the work mark WAM is 100% identical, so that it is recognized as a score of 100.

As described above, a pattern search is performed on the entire area displayed on the monitor, and the position having the closest score (the highest) to 100 is recognized as the position of the work mark WAM (the position where the work mark WAM is detected). The position coordinates are stored as the position coordinates of the work mark.
Specifically, the vicinity of the workpiece mark WAM on the workpiece W is observed by the alignment unit 10. FIG. 14 is a diagram showing an actual work area projected by the monitor 12 at that time. As described above, the magnification of the alignment microscope is three times the same as the magnification when the work mark pattern is registered.
Therefore, the same range as FIG. 12 (15 mm × 15 mm range) is projected on the monitor 12. This range is moved (scanned) pixel by pixel, and the score is obtained at each position.
In the work mark search area of FIG. 14 (15 mm × 15 mm range), for example, a pattern other than the work mark may be formed as shown in (B), or as shown in (C). There is also a case where dust is attached to the surface. Sometimes the pattern or the shape of the garbage resembles a registered work mark pattern. In such a case, a plurality of positions with relatively high scores may be detected in the image processing area.
However, as described above, the control unit 11 stores the work mark WAM based on the contrast in units of pixels surrounded by virtual lines. Therefore, if the work mark WAM exists in the area of FIG. 14, the score at the position (A) is the highest. Accordingly, the position where the highest score is detected is set to be detected as the position of the work mark.

JP 2010-117632 A

In a semiconductor wafer exposure apparatus, a work mark formed on a wafer, which is a workpiece, is often formed by photolithography in the same manner as a circuit pattern formed on the same surface.
On the other hand, in an exposure apparatus for a printed circuit board, a hole (dent) having a diameter of about 100 μm that is formed in the printed circuit board by machining such as laser irradiation or drilling may be used as a work mark.
An illumination method called dark field illumination is used to detect such holes formed in the substrate. In dark field illumination, illumination light is irradiated obliquely onto a substrate, and an image sensor is disposed above the substrate. Holes are difficult to detect with illumination from directly above.
FIG. 15A is a diagram schematically showing a state in which the hole 101 formed in the printed circuit board 100 is imaged by dark field illumination by the alignment microscope of FIG. In the figure, the illumination light 103 is shown only from the right side and the left side of the drawing, but actually, the hole 101 is illuminated from all directions of 360 °.

The illumination light 103 is incident on the printed circuit board 100 at an angle. The surface of the printed circuit board 100 is a diffusing surface, and the illumination light 103 applied to the surface of the substrate or the bottom of the hole is diffused and reflected. , (Not shown).
On the other hand, the light incident on the wall surface of the hole 101 is diffused and reflected, but the light reflected on the wall surface does not directly enter the image sensor (CCD).
Therefore, the hole 101 appears in the image sensor with different brightness between the wall portion and the other portions (the surface of the printed circuit board and the bottom portion of the hole). For example, as shown in FIG. 15B, the wall portion may appear in a ring shape with a black edge, and the bottom portion of the hole may appear gray like the substrate surface.
Therefore, when the hole with the bottom is ideally formed, a ring-shaped pattern as shown in FIG. 15B is registered as a registered image of the work mark WAM.

However, even if the hole having the same shape is intended to be processed, for example, when it is detected by an alignment microscope, the appearance (shape, brightness, darkness, and color tone) of the imaging means (CCD) may be different.
One reason for this is when the shape of the finished holes accidentally changes.
FIG. 16 shows an example of the shape of a hole formed by processing a printed board with a laser or a drill. This figure is a sectional view of the hole.
FIG. 16A shows an ideal hole shape. However, depending on the shape of the tip of the laser or drill, as shown in FIG. 16B, the wall of the hole may be slanted (in a mortar shape). Further, as shown in FIG. 16C, burrs 104 may be generated at the edge portions of the holes.
As described above, the holes formed by machining in the printed circuit board 100 may vary in shape. Therefore, when such a hole is detected with an alignment microscope as a work mark, the appearance on the imaging means (CCD) is different.

Another reason why the appearance of the imaging means (CCD) is different is due to the processing performed after the hole formation.
For example, as shown in FIG. 16D, the printed board may be plated with a metal foil such as copper 105 on the surface, and the inside of the hole is also plated. Since the reflectance of the surface is changed by metal plating, the appearance on the imaging means (CCD) varies depending on the presence or absence of plating.
Moreover, as shown in FIG.16 (e), a resist film may be affixed on the metal-plated thing. The resist film 106 has a thickness of several tens of μm. When the resist film 106 is pasted, the resist film 106 cannot be pasted along the side surface or the bottom surface of the hole, and the opening of the hole is blocked.
Therefore, in the hole portion, the reflectance of illumination light and the direction in which the light is reflected change depending on the resist film, and how the imaging means (CCD) looks when the resist film is not applied and when the resist film is applied. Is different.
For example, as shown in FIG. 16E, when a resist film is applied, the shape of the hole detected by the alignment microscope may appear as a black circle as a whole.
In addition, depending on how the resist film is applied, the degree of sag of the film in the hole also changes, so that the appearance on the imaging means (CCD) differs.

If the appearance of the work mark is different, the actually picked-up work mark image is different from the work mark image stored in the control unit. When this happens, the score at the position where the work mark exists becomes low, and the work mark cannot be detected correctly.
This will be described with reference to FIG. A ring-shaped pattern shown in FIG. 17A is an image of a work mark registered in the control unit.
FIG. 17B shows a case where the work mark exists in the area where the work mark on the substrate is searched (searched) and looks almost the same as the registered image. In this case, the registration marks in FIG. 17A almost coincide with each other at the positions enclosed by the squares in FIG. 17B, and the score is, for example, 9000 points (10,000 full marks).
FIG. 17C shows a case where this is a problem of this case. This is a case where a work mark exists in the area to be searched, but looks different from the registered mark due to the above-mentioned causes, and looks like a black circle. The center of the ring is white, but the black circle is black at the center, so the score at the position enclosed by the square in FIG. 17C is low, for example, about 2000 points.

FIG. 17D shows a case where a black square outline pattern such as wiring that is not a work mark exists in the search area. In this case, although the shapes are different, the bright and dark pattern in which the center is black and the peripheral portion is white is similar, so the score at the position surrounded by the square in FIG. 17 (d) is higher than in the case of FIG. 17 (c), For example, it may be 5000 points.
Although FIG. 17C differs from the registered mark in appearance, it must be detected because it is a work mark. However, since FIG. 17D is not a work mark, it should not be detected as a work mark.
However, in order to detect FIG. 17 (c) as a work mark, for example, if the control unit is set to “use a work mark when the score is 2000 points or more”, FIG. It will be detected as a mark. On the other hand, in order not to detect FIG. 17D as a work mark, if “score is more than 6000 points is set as a work mark”, FIG. 17C cannot be detected as a work mark.
Therefore, the work mark cannot be detected correctly.

As described above, the work marks formed on the work having the same shape differ in the appearance (shape, brightness, darkness, and color tone) projected by the image pickup device depending on the processing conditions of the work mark and the processing in the printed circuit board manufacturing process. Sometimes. In this case, even if an actual work mark is detected with the registered work mark, it may not be detected.
In Patent Document 1, a plurality of patterns having different appearances are registered in the storage unit, the registered pattern is compared with the pattern in the search area, a score of coincidence is obtained, and the score exceeds a certain value. At this time, this pattern is determined as a work mark.
In the present invention, a work mark can be detected without registering a plurality of patterns as described above, and the appearance (shape, brightness, darkness, and color tone) of the work mark projected on the image sensor of the alignment microscope is different. Even if it is, it aims at providing the detection apparatus of the work mark which can detect a work mark correctly.

As a result of intensive studies, the inventor of the present invention determines the distance from the alignment illumination means for illuminating the workpiece (work mark) to the workpiece surface (the height of illumination light with respect to the workpiece) when imaging the workpiece surface with an alignment microscope. It has been found that the appearance (shape, brightness, and color tone) of the work mark image projected on the image sensor of the alignment microscope changes when it is changed.
FIG. 4 shows an image of a work mark that is a non-penetrating hole (a dent) formed in the work, with the interval from the work to the illumination means (the height of the illumination light) changed, and a pre-registered work mark. A score (a value indicating the degree of coincidence between the registered pattern and the pattern of each image, here, a maximum of 9999) is shown when the pattern of each image is searched by pattern (registered pattern).
In each image, five kinds of work marks were created from the left column: a dent of φ140 μm, a dent of φ120 μm, a dent of φ100 μm, a dent of φ80 μm, and a dent of φ200 μm.
The distance from the workpiece to the illumination means (the height of the illumination light) was imaged in six types of 11.0 mm, 8.5 mm, 5.5 mm, 4.0 mm, 2.5 mm, and 1.0 mm from the left in the figure.
As is apparent from the figure, changing the height of the illumination light changes the appearance of the captured work mark and the score.

The reason why the appearance of the work mark changes depending on the height of the illumination light is considered to be because the angle at which the illumination light of the dark field illumination enters the work changes.
FIG. 5 is a diagram showing the state when the height of the dark field illumination means (ring-shaped illumination means 10c) is changed and the luminance distribution of the captured image in each state. The horizontal axis of the graph shown in FIG. The position and the vertical axis indicate luminance (relative value).
As shown in the figure, when the distance from the work W to the illumination means 10c is increased (the height of the illumination light is increased), the incident angle of the illumination light is reduced, and the distance from the work W to the illumination means 10c is reduced. When the height of the illumination light decreases, the incident angle of the illumination light increases.

Returning to FIG. 4, taking an indentation (work mark) of φ200 μm (rightmost column) as an example, when the illumination light height is 11.0 mm or 8.5 mm, a circle with a white portion on the inside (center) Looks like a ring. However, when the height of illumination light is 5.5 mm, 4.0 mm, 2.5 mm, and 1.0 mm, it looks like a black circle.
In the case of φ140 μm (leftmost column), when the illumination light height is 11.0 mm, it looks like an annular shape with a white part inside (center), and when the illumination light height is 8.5 mm. Looks like a gray circle. And when the height of illumination light is 5.5 mm, 4.0 mm, 2.5 mm, and 1.0 mm, it looks like a dark black circle.
In the lower part of FIG. 4, black circles of φ140 μm, black circles of φ120 μm, black circles of φ100 μm, black circles of φ80 μm, and black circles of φ200 μm are registered as work marks, and the scores when searching for the work marks of each image (maximum 9999 points) Indicates. Note that 7000 points or more are generally at a level where stable search is possible.

In the case of a work mark of φ200 μm, the work mark could not be searched in the image with the illumination light height of 11.0 mm, and the score was 1489 when the illumination light height was 8.5 mm. However, when the height of the illumination light was 5.5 mm, 4.0 mm, and 2.5 mm, the score was 8000 or more. This score can be detected as a work mark and used for alignment. Since the highest score is when the illumination light is 4.0 mm in height, it is desirable to perform alignment based on the image at this time. However, when the illumination light height was 1.0 mm, the score decreased again to 5947.
Similarly, in the case of a work mark of φ140 μm and φ120 μm, the score becomes the highest when the height of the illumination light is 4.0 mm. On the other hand, in the case of a work mark of φ100 μm and φ80 μm, the score is highest when the height of the illumination light is 5.5 mm.
As described above, the height of the illumination at which the highest score is obtained differs depending on the size (shape) of the work mark.

Therefore, a work mark pattern is registered in advance (hereinafter, this pattern is referred to as a registered pattern), and when the work mark is imaged by an alignment microscope, the height of the dark field illumination means is changed to image the work, Search using registered patterns.
For example, first, a work mark image is searched by obtaining a score while comparing a pattern on a workpiece imaged at the height of the first illumination light with a registered pattern. Next, the work mark image is searched by obtaining a score while comparing the pattern captured at the height of the second illumination light with the registered pattern.
This is repeated, and if there is a pattern showing a score equal to or higher than a preset value, it is assumed that the work mark is detected using this as a work mark image. Then, alignment is performed using the work mark image. Alternatively, alignment is performed using a work mark image having a height of illumination light showing the highest score as a work mark.

In the present invention, the above-described problems are solved as described above, and the workpiece alignment mark detection apparatus is configured as follows.
(1) Dark field illumination means for illuminating a pattern on the work, illumination means moving means for moving the dark field illumination means in a direction orthogonal to the work surface, and on the work illuminated by the dark field illumination means An image pickup means for picking up a pattern, and a controller for controlling the illumination means moving means and the image pickup means to detect an alignment mark on the workpiece are provided. The control portion has a pattern to be detected as a work alignment mark. Is stored as a registered pattern, and an alignment mark detector is provided.
The alignment mark detector compares the pattern on the workpiece imaged by the imaging means with the registered pattern to obtain a degree of coincidence, and when the degree of coincidence is equal to or greater than a preset value, When the degree of coincidence detected is detected as an alignment mark, the dark field illumination means is moved by the illumination means moving means, the pattern on the workpiece is imaged again by the imaging means, and the image on the imaged workpiece is again imaged. The pattern and the registered pattern are compared to determine the degree of coincidence. When the obtained degree of coincidence exceeds a preset value, the pattern on the workpiece is detected as an alignment mark.
(2) In the above (1), an alignment microscope for receiving a pattern on a work that includes an image pickup means and is illuminated by the dark field illumination means, and an alignment that moves the alignment microscope in a direction orthogonal to the work surface. A microscope moving means is provided.
The illumination means moving means is attached to the alignment microscope so as to move integrally, and the dark field illumination means is moved relative to the alignment microscope by the illumination means moving means.

In the present invention, the following effects can be obtained.
(1) Provide a means for moving the dark field illumination means, illuminate the work with the dark field illumination means from different heights to image the pattern on the work, and compare the imaged pattern on the work with the registered pattern Since the workpiece alignment mark is detected, the workpiece alignment mark can be reliably detected even if the workpiece alignment mark looks different depending on conditions.
(2) The illumination means moving means is attached to the alignment microscope and configured to move integrally, and the dark field illumination means is moved relative to the alignment microscope by the illumination means moving means. By doing so, when workpieces with different thicknesses are placed on the workpiece stage and the alignment microscope is moved for focusing, the dark field illumination means can be moved in accordance with the movement of the alignment microscope. .
For this reason, if the height of the dark field illumination means is set to an appropriate height with respect to the workpiece surface, the darkness of the dark field illumination means can be adjusted by moving the alignment microscope for focusing even if the workpiece thickness changes. The height of the field illumination means is set to an appropriate height with respect to the work surface.

It is a figure which shows the structural example of the projection exposure apparatus which is one of the application objects of this invention. It is a figure which shows the structural example of the ring illumination means (dark-field illumination means) shown in FIG. It is a figure which shows the attachment structure of the alignment microscope and illumination means moving mechanism shown in FIG. It is a figure which shows the image and the score which imaged the work mark formed in the workpiece | work by changing the height of illumination light. It is a figure which shows the brightness distribution of the picked-up image in a state when changing the height of an illumination means, and each state. It is a figure explaining registration of a mask mark and a work mark. It is a figure explaining the detection of a work mark, and alignment of a mask and a work. It is a figure explaining an example of detection of a work mark. It is a figure which shows the other example from which the appearance of a work mark differs. It is a figure which shows schematic structure of an alignment microscope. It is a figure which shows an example of a registration pattern and a detection pattern. It is a figure which shows an example of the image displayed on a monitor. It is a figure which shows the example of a shape of a work mark. It is a figure explaining a pattern search. It is the figure which showed typically a mode that the hole formed in the board | substrate with the alignment microscope was imaged by dark field illumination. It is a figure which shows the example of the shape of the hole formed by processing a printed circuit board with a laser or a drill. It is a figure which shows the example of the image imaged with the registered work mark image and the alignment microscope.

FIG. 1 is a diagram showing a configuration example of a projection exposure apparatus which is one of application targets of the present invention.
In the figure, MS is a mask stage. On the mask stage MS, a mask M on which a mask mark MAM and a mask pattern MP are formed is placed and held.
Exposure light is emitted from the light irradiation device 1. The emitted exposure light is irradiated onto the workpiece W placed on the workpiece stage WS via the mask M and the projection lens 2, and the mask pattern MP is projected onto the workpiece W and exposed.
Between the projection lens 2 and the workpiece W, there are provided four alignment microscopes 10 that can move in the direction of arrow A (left and right in the drawing). Before the mask pattern MP is exposed on the workpiece W, the alignment microscope 10 is inserted into the position shown in the figure, the mask mark MAM and the workpiece mark WAM formed on the workpiece are detected, and the mask M and the workpiece W are aligned. I do. After the alignment, the alignment microscope 10 is retracted from the workpiece W. FIG. 1 shows only one of the four alignment microscopes provided.

As described above, the alignment microscope 10 includes the half mirror 10a, the lenses L1 and L2, and the CCD camera 10b as an imaging unit. In order to perform the dark field illumination shown in FIG. 15, the alignment microscope 10 is provided with illumination means 10c for irradiating the substrate with illumination light obliquely. The illumination unit 10c is configured by arranging a plurality of illumination light sources such as LEDs in a ring shape.
FIG. 2 shows a configuration example of ring illumination means (dark field illumination means) for irradiating illumination light obliquely from all directions (dark field illumination) as described above.
As shown in FIG. 2 (a), the ring illumination means has a large number of LEDs 22 arranged concentrically in a thin cylindrical donut-shaped main body container 21. Each LED 22 has an angle in the direction of the center O of the circle, as shown in FIG. It arrange | positions and it is comprised so that illumination light can be irradiated to the workpiece | work to test | inspect from diagonally.

Further, as shown in FIG. 1, an illumination means moving mechanism (illumination means moving means) 5 is attached to the illumination means 10c. The illumination means moving mechanism 5 moves the illumination means 10c in a direction orthogonal to the surface of the workpiece W (arrow B direction in the figure: vertical direction in the drawing). That is, when the illumination means moving mechanism 5 operates, the interval between the workpiece W and the illumination means 10c changes. In addition, the space | interval of the alignment microscope 10 and the workpiece | work W does not change.
FIG. 3 shows a mounting structure of the alignment microscope 10 and the illumination means moving mechanism 5.
As shown in the figure, the alignment microscope 10 is attached to a support member 6a via an alignment microscope moving mechanism (alignment microscope moving means) 6, and the support member 6a is attached to a base 6b. Therefore, the alignment microscope 10 can be moved in the vertical direction with respect to the base 6b by the alignment microscope moving mechanism 6.
The illumination means 10 c is attached to the support member 5 a via the illumination means moving mechanism 5, and the support member 5 a is attached to the alignment microscope 10.

  Therefore, the illumination means moving mechanism 5 moves integrally with the alignment microscope 10, and the illumination means moving mechanism 5 can move the illumination means 10 c relative to the alignment microscope 10. For this reason, when a workpiece of different thickness is placed on the workpiece stage WS and the alignment microscope 10 is moved in the vertical direction for focusing, the illumination means 10c is also moved in the vertical direction in accordance with the movement of the alignment microscope. To do. Therefore, if the height of the illumination means 10c is set to an appropriate position with respect to the work surface, the distance between the illumination means 10c and the work surface is kept constant even if the thickness of the work changes, and the illumination means The height of 10c can be maintained at an appropriate height.

Returning to FIG. 1, the mask mark MAM image, the work mark WAM image, and the like captured by the CCD camera 10 b of the alignment microscope 10 are sent to the control unit 11. The control unit 11 includes an image processing unit 11a that processes an image captured by the CCD camera 10b, and a storage unit 11b that stores positional coordinate information such as a work mark and a mask mark, various parameters, and the like.
Further, the control unit 11 compares the pattern image on the workpiece imaged by the CCD camera 10b and image-processed by the image processing unit 11a with a work mark image (registered pattern) registered in the storage unit 11b as will be described later. A score indicating the degree of coincidence, and based on this score, the alignment mark detector 11c that determines whether the imaged pattern on the workpiece is a pattern to be detected as a workpiece mark; In order to move the illuminating means 10c in the vertical direction (B direction), an illuminating means moving mechanism control section 11d for controlling the driving of the illuminating means moving mechanism 5 is provided.
In addition, the control unit 11 detects the workpiece stage WS and / or the mask stage MS so that the position coordinates of the pattern on the workpiece detected as the workpiece mark coincide with the position coordinates of the mask mark image stored in the storage unit 11b. ) And a green climbing unit 11f for climbing the work mark image (registered pattern) to the storage unit 11b in accordance with an operator's instruction.

The work stage WS or the mask stage MS is driven by the work stage drive mechanism 4 and the mask stage drive mechanism 3 controlled by the alignment control unit 11e, and in the XY directions (X, Y: mask stage MS, work stage WS surface) And move around an axis perpendicular to the XY plane.
A monitor 12 is connected to the control unit 11, and an image processed by the image processing unit 11 a is displayed on the screen of the monitor 12.

In the exposure apparatus of FIG. 1, the detection of the work mark and the alignment of the mask M and the work W are performed as follows.
Illumination light is irradiated onto the mask M from the light irradiation device 1 or an alignment light source (not shown), and the mask mark MAM image is received by the CCD camera 10 b of the alignment microscope 10 and sent to the control unit 11. The image processing unit 11a of the control unit 11 converts the mask mark MAM image into position coordinates and stores it in the storage unit 11b.
Various methods for detecting a mask mark have been proposed. For example, refer to Patent Document 1 if necessary.

Next, the workpiece W is irradiated with illumination light from the illumination means 10c of the alignment microscope 10, and a pattern on the workpiece W is imaged and a pattern search is performed. That is, the alignment mark detection unit 11c compares the captured pattern with a registered pattern that is a work mark image registered in the storage unit 11b to detect the work mark WAM on the work W. The control unit 11 obtains the position coordinates.
The alignment control unit 11e of the control unit 11 allows the work stage WS (or the mask stage MS, the mask stage MS, so that the position coordinates of the stored mask mark MAM and the position coordinates of the detected work mark WAM have a predetermined positional relationship. Alternatively, both of them are moved and the mask M and the workpiece W are aligned.

Hereinafter, the work mark detection procedure and the mask alignment procedure according to the embodiment of the present invention will be described in detail.
(1) Registration of Mask Mark MAM and Work Mark WAM First, the registration procedure of the mask mark MAM and the work mark WAM will be described with reference to FIG.
First, the position of the mask mark MAM is detected. Therefore, as shown in FIG. 6A, the position coordinates (xm1, ym1) of the mask mark MAM within the field of view of the alignment microscope 10 are obtained.
That is, the mask mark MAM image captured by the CCD camera 10b of the alignment microscope 10 is processed by the image processing unit 11a of the control unit 11, and the position coordinates (xm1, ym1) of the mask mark MAM are obtained and stored in the storage unit 11b. To do.

Next, the work mark image is registered in the storage unit 11 b of the control unit 11. This climbing is performed visually by the operator as follows.
An actual workpiece W1 (for example, the first workpiece in a series of workpieces to be subjected to exposure processing) is placed on the workpiece stage WS, and illumination light is irradiated onto the workpiece W1 from the illumination unit 10c. The alignment microscope 10 is used to receive the surface image of the workpiece W1, and the image processing unit 11a processes the image to display the surface of the workpiece W1 on the monitor 12.
The alignment microscope 10 at this time is the same alignment microscope 10 as when actually detecting the work mark WAM, and the magnification of the alignment microscope 10 is the same as when actually detecting the work mark WAM (for example, 3 times). is there. Moreover, the alignment microscope 10 is maintained at the same position as the position when the mask mark is detected, and the field of view of the alignment microscope 10 is also the same.

The worker looks at the projected image of the workpiece W1 and searches for the workpiece mark WAM. If the work mark WAM is found, as shown in FIG. 6 (b), the work mark WAM is surrounded on the monitor 12 by a virtual line for registering the work mark so that the entire work mark WAM can be entered. And mark it with +.
At that time, the operator moves the illumination means 10c in the vertical direction, and the image received at the illumination position where the work mark is most clearly seen is used as the work mark pattern.
If the storage unit 11b stores the position of the illumination unit 10c where the workpiece mark is most clearly seen, the initial position of the illumination unit 10c when the workpiece mark is automatically detected by the control unit 11, which will be described later, is used. can do.

Then, the area surrounded by the virtual line for registering the work mark is set as a pattern image of the work mark WAM, and a green climbing instruction is given to the registration unit 11f and registered as a “registration pattern” in the storage unit 11b.
Further, the center position of the work mark image is visually identified, and the distances dx and dy from the upper left corner of the quadrangle formed by a virtual line to the center position of the work mark image are stored in the storage unit 11b as the position coordinates of the work mark image. Greening.
Various methods for automatically obtaining the center position of the work mark image by calculation or the like have been known so far, and the setting of the center position of the work mark image is not visually observed but automatically performed by image processing by the image processing unit 11a. You may make it ask for.

(2) Work mark detection procedure and mask alignment The work mark detection procedure and mask alignment will be described with reference to FIG.
The alignment mark detection unit 11c of the control unit 11 compares the registered workpiece mark image with the pattern on the workpiece and detects the workpiece mark on the workpiece W. At this time, the pattern on the workpiece is imaged by changing the height of the illumination means 10c relative to the workpiece W (the interval between the illumination means 10c and the workpiece W).
That is, the alignment mark detection unit 11c controls the illumination unit movement mechanism 5 by the illumination unit movement mechanism control unit 11d to first set the illumination unit 10c to the first height, and then registers the registered pattern (registered work mark image). ) And the pattern in the search area to obtain a score of coincidence, then the illumination means 10c is set to the second height, the registered pattern (registered work mark image) and the pattern in the search area And the score of the degree of coincidence is obtained.
Similarly, the score of coincidence is obtained while changing the height of the illumination means 10c, and an image in which this score exceeds a certain value, for example, or the height image of the illumination light with the highest score is obtained. The pattern in the search area is detected as a work mark on the work W.
Here, if the first height is the height of the illumination light when the “registered pattern” that is the pattern image of the work mark is imaged, the illumination means 10c is set to the first height, The possibility that the work mark can be detected can be increased.

For example, the registered pattern is a black circle shape, and the pattern (work mark WAM1) on the workpiece imaged at the height of the first illumination light looks like a ring, and the height of the second illumination light. It is assumed that the pattern (work mark WAM2) on the work imaged in FIG.
Using the registered pattern, first, a search area of a work imaged at the height of the first illumination light is searched to obtain a score of the work mark WAM1. Next, the search area of the workpiece imaged at the height of the second illumination light is searched, and the score of the workpiece mark WAM2 is obtained. Then, the alignment control unit 11e performs alignment between the mask and the workpiece using a workpiece mark that has a score equal to or higher than a preset value or using a workpiece mark that has the highest score.
In the case of the above example, if the registered work mark WAM has a black circle shape, the degree of coincidence with the work mark WAM2 imaged at the height of the second illumination light is high and the score is also high. Therefore, in such a case, the mask and the work are aligned using the work mark WAM2 imaged at the height of the second illumination light.

The work mark search is performed as shown in FIG. 7, for example.
For example, it is assumed that the rectangular area P shown in FIG. 7A is registered in the storage unit 11b as a registered pattern (work mark image).
In order to search for a work mark, as shown in FIG. 7 (b), within the field of the alignment microscope 10, for example, from the upper left corner of the field of view, the vertical Y including the registered pattern shown in FIG. The rectangular areas P of X are overlapped while being shifted little by little, and a place with a high degree of coincidence is searched for.
Then, when a region having a high degree of coincidence is searched within the field of view of the alignment microscope, the coordinates (x1, y1) of the upper left corner of the rectangular region P at that time are obtained, and the center position of the pattern in the region P is indicated. By adding (dx, dy), (x1 + dx, y1 + dy) is set as the position coordinates (xw1, yw1) of the detected work mark.

  When the position coordinates of the work mark are detected as described above, the alignment control unit 11e stores the position coordinates (xw1, yw1) of the detected work mark WAM in advance as shown in FIG. 7C. The work stage WS and / or the mask stage MS are moved so as to coincide with the position coordinates (xm1, ym1) of the mask mark being set (or so as to have a preset positional relationship).

The detection of the work mark will be described with reference to FIG.
Here, the registered work mark pattern (registered pattern) WAM is a black circle pattern as shown in FIG. Then, the height of the illumination light is switched in three stages to illuminate the work (work mark).
The appearance of the work mark on the workpiece when the illumination light is at the first height is shown in FIG. 8B, and the appearance of the work mark when the illumination light is at the second height is shown in FIG. Assume that the appearance of the work mark in the case of the height of FIG.
(1) Start of search.
First, the pattern on the workpiece is illuminated and imaged with the height of the first illumination light, and the search area is searched with the climbing pattern. The alignment mark detection unit 11c of the control unit 11 compares the registered pattern WAM with the pattern shown in FIG.
While the green climbing mark is a black circle, the visible work mark is a ring shape shown in FIG. Accordingly, the degree of coincidence between the two is low, and the score is also low (the score in this case is 2000 points). This value is stored in the storage unit 11b as a score in the case of the height of the first illumination light.

Subsequently, the height of the illumination light is changed, the pattern on the workpiece is illuminated with the second illumination light, and the search area is searched with the registered pattern WAM. The alignment mark detection unit 11c compares the registered pattern WAM with the pattern shown in FIG.
Since the registered pattern WAM is very similar to the shape of the visible work mark, the degree of coincidence is high and a high score is obtained (the score in this case is 9000 points). This value is stored in the storage unit 11b as a score for the second illumination light height.
Further, the height of the illumination light is changed, the pattern on the work is illuminated and imaged with the height of the third illumination light, and the search area is searched with the green climbing mark. The alignment mark detector 11c compares the registered pattern WAM with the pattern shown in FIG. 8D to obtain a score.
The green climbing pattern WAM does not resemble the shape of the visible work mark and has a low matching score and a low score (the score in this case is 1500 points). This value is stored in the storage unit 11b as a score in the case of the third illumination light height.
The alignment mark detection unit 11c of the control unit 11 has a score of 2000 points for the height of the first illumination light, a score of 9000 points for the height of the second illumination light, and a height of the third illumination light. In this case, the score is compared with 1500 points. Then, the pattern of FIG. 8C in the case of the second illumination light height at which the highest score is obtained is adopted as a work mark.

If the pattern on the workpiece is imaged many times by changing the height of the illumination light and the search is performed, it takes time to detect the workpiece mark, and as a result, the exposure processing time becomes longer as a whole.
As a solution to the problem, for example, if a score more than a preset score is obtained at a certain illumination light height, the imaging with the illumination light height changed at that stage is terminated, and the illumination light It is conceivable that the height is set so as to proceed to the next procedure (work mark position detection and mask / work position alignment).
In the example of FIG. 8 above, for example, if a score of 8000 or more is obtained, it is determined that the work mark has been detected, and the control unit 11 is set to proceed to the next procedure (mask and workpiece alignment). . By doing so, since the imaging at the height of the third illumination light is not performed, the work mark detection time can be shortened.

In the present invention, when a bottomed hole (concave, dent) formed in the substrate is used as a work alignment mark (work mark), it is detected by an alignment microscope by plating or applying a resist film to the hole. As an example, it was explained that the appearance (shape, brightness, and color tone) of the work mark is different.
However, not only in the case of holes, even when the protrusions 107 (projections, bulges) formed on the substrate 100 are used as work alignment marks as shown in FIG. Change, the present invention can be applied.
In addition, for example, as shown in FIG. 9B, the surface reflectance may change depending on the presence or absence of plating of copper 105 or the like, and the appearance may change.
Further, when the resist film 106 is attached to the protrusion as shown in FIG. 9C, it cannot be attached along the side surface of the protrusion, and a space is formed on the side surface of the protrusion. Therefore, the reflectance of the illumination light and the direction in which the light is reflected change, and the appearance on the imaging means (CCD) differs depending on whether the resist film is not applied or not.
Furthermore, depending on how the resist film is applied, the slackness of the film also changes, so that the appearance changes, but the present invention can also be applied to these cases.

DESCRIPTION OF SYMBOLS 1 Light irradiation apparatus 2 Projection lens 3 Mask stage drive mechanism 4 Work stage drive mechanism 5 Illumination means moving mechanism 5a Support member 6 Alignment microscope moving mechanism 6a Support member 6b Base 10 Alignment microscope 10a Half mirror 10b Imaging means (CCD camera)
10c Illumination means (dark field illumination means)
21 Main body container 22 LED
11 control unit 11a image processing unit 11b storage unit 11c alignment mark detection unit 11d illumination means moving mechanism control unit 11e alignment control unit,
11f Green climbing part 12 Monitor MS Mask stage MAM Mask alignment mark (mask mark)
MP Mask pattern M Mask WS Work stage W Work WAM Work alignment mark (work mark)

Claims (2)

A device for detecting a work alignment mark formed on a work as a protrusion or a dent,
Dark field illumination means for illuminating a pattern on the workpiece;
Illumination means moving means for moving the dark field illumination means in a direction perpendicular to the workpiece surface;
Imaging means for imaging the pattern on the workpiece illuminated by the dark field illumination means;
A controller for controlling the illumination means moving means and the imaging means to detect an alignment mark on the workpiece;
The control unit
A storage unit storing a pattern to be detected as a work alignment mark as a registered pattern, and an alignment mark detection unit,
The alignment mark detector compares the pattern on the workpiece imaged by the imaging means with the registered pattern to obtain a degree of coincidence, and when the degree of coincidence is equal to or greater than a preset value, Detect as alignment mark,
When the obtained degree of coincidence is low, the dark field illumination unit is moved by the illumination unit moving unit, the pattern on the workpiece is imaged again by the imaging unit, and the pattern on the workpiece and the registered pattern that have been imaged again are registered. An apparatus for detecting a workpiece alignment mark, wherein a matching degree is obtained by comparison, and a pattern on the workpiece is detected as an alignment mark when the obtained matching degree is equal to or greater than a preset value. An alignment microscope that incorporates the imaging means and receives the pattern on the workpiece illuminated by the dark field illumination means, and an alignment microscope moving means that moves the alignment microscope in a direction orthogonal to the workpiece surface;
2. The workpiece alignment mark detection according to claim 1, wherein the illumination means moving means moves integrally with the alignment microscope, and moves the dark field illumination means relative to the alignment microscope. apparatus.

Images