JP2011215132A - Pattern inspection method, pattern inspection device, and imaging head for the pattern inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern inspection device facilitating focusing of a plurality of imaging units.SOLUTION: The plurality of imaging units 5a, 5b and 5c are fixed to one trestle 4 movable in the approaching/separating direction (Z) with respect to the surface of an inspecting object 2, optical lens-based units 8b and 8c of the imaging units 5b and 5c are driven in the approaching/separating direction (Z) to perform focusing, and a pattern 3 formed on the inspecting object 2 is inspected.

Description

  The present invention relates to a pattern inspection method and a pattern inspection apparatus for inspecting a pattern formed on a substrate or the like, and an imaging head for a pattern inspection apparatus.

Conventionally, a pattern inspection apparatus shown in FIG. 14 is used to inspect a pattern of a substrate having a fine pattern such as a plasma display panel or a liquid crystal panel.
This pattern inspection apparatus has a configuration in which a pattern D of an inspection object 63 is captured by an imaging head 66 including a camera 64 and an optical lens system 65. The controller 67 controls the distance between the optical lens system 65 and the image sensor 68 based on a signal obtained from the image sensor 68 of the camera 64.

  In this conventional pattern inspection apparatus, the digital data of the pattern D captured through the camera 64 is processed to detect a defect in the pattern D of the inspection object 63. As a typical processing method, there is a method of finding a defect of the pattern D by comparing data when there is no defect of the pattern D and data of the inspection object 63 captured by the imaging head 66. Although this method is simple in processing, there is a problem that comparison of data is difficult due to uncertain magnification of the imaging system.

  In order to overcome this problem, the data of the inspected object 63 captured by the imaging head 66 is compared with a pattern adjacent to, several cycles ahead, or after, and a non-periodic portion is found and determined as a defect. There is an adjacent comparison method. This is a method using the fact that the pattern D of the object to be imaged 63 is periodic.

  Further, when a CMOS device, a CCD device, or a MOS device is used as the image sensor 68, a measurement error may occur due to a mismatch between the device cell size of the image sensor 68 and the pattern pitch of the inspection object 63.

  As a method of eliminating this measurement error, there is a method described in Patent Document 1. In the method described in Patent Document 1, an optical lens system has a minimum detection defect size as a cell size in an image projected onto a solid-state imaging device of a pattern by an optical lens system so that an integer number of cells are included in one pitch. Is set by the control unit 67.

  However, even with the method described in Patent Document 1, it takes time to inspect a finer pattern over a large area, and the inspection requires a lot of cost. Therefore, it is generally used to capture a pattern in a short time by dividing a region of an inspection object using a plurality of imaging units as an imaging head. Here, each imaging unit has a camera and an optical lens system provided between the inspection object and the camera.

JP 2003-329609 A

  For example, in order to use a plurality of imaging units as in the method described in Patent Document 1, it is easier to install a plurality of imaging units on a single gantry than to install them all independently. it can.

  However, when a plurality of imaging units are mounted on one gantry, it is necessary to focus the plurality of imaging units on the surface of one inspection object. That is, a drive unit for moving each imaging unit independently and vertically (Z-axis direction) with respect to the object to be inspected is required for each imaging unit.

  An object of the present invention is to solve these conventional problems and to provide a pattern inspection method, a pattern inspection apparatus, and an image pickup head for a pattern inspection apparatus that can simply realize a focusing configuration of a plurality of image pickup units.

  A pattern inspection apparatus according to the present invention for solving the above-described problems is characterized in that a pattern periodically arranged on the surface of an object to be inspected is scanned, and an imaging head equipped with an imaging element and an optical lens system unit is separated by a certain period. And a control device that detects a defect in the pattern as compared with a portion of the image pickup device, wherein the imaging head moves a base on which a plurality of imaging units are fixed to a surface of the inspection object. A drive unit that is movable in a direction, and the imaging unit includes an imaging element unit that includes an imaging element, and an optical lens system unit that is movable in the approaching and separating direction. The optical lens system unit is moved so that the magnification M is in the following range so that each imaging unit is focused on the surface of the object to be inspected. And detecting defects of the turn.

C (N−ΔN) / P <M <C (N + ΔN) / P
Where C: element pitch of the image sensor, P: pitch of the pattern, N: number of elements of the image sensor within the projected image pitch of the pattern, and ΔN: allowable element of the projected image.

  An imaging head for a pattern inspection apparatus according to the present invention is an imaging head for a pattern inspection apparatus that images a pattern arranged in parallel on a surface to be inspected by a plurality of imaging units, and is perpendicular to the surface to be inspected And a plurality of imaging units attached to the gantry. The imaging unit is composed of an imaging element and an optical lens system unit movable in the vertical direction.

  In the pattern inspection method of the present invention, the pattern periodically arranged on the surface of the object to be inspected is scanned by the imaging unit equipped with the imaging element and the optical lens system unit, and compared with a portion separated by a certain period. In the pattern inspection method for detecting a defect in the pattern, each of the imaging units is moved to the surface of the inspection object by moving the optical lens system unit so that the magnification M of the optical lens system unit falls within the following range. After the focus is adjusted, a defect of the pattern is detected.

C (N−ΔN) / P <M <C (N + ΔN) / P
Where C: element pitch of the image sensor, P: pitch of the pattern, N: number of elements of the image sensor within the projected image pitch of the pattern, and ΔN: allowable element of the projected image.

  ADVANTAGE OF THE INVENTION According to this invention, the pattern inspection method and pattern inspection apparatus which can implement | achieve the structure of focusing of several imaging unit simply can be provided, and the imaging head for pattern inspection apparatuses.

1 is a schematic configuration diagram of an imaging head of an inspection apparatus according to Embodiment 1 of the present invention. (A) Schematic front view for showing the specific example of FIG. 1, (b) Schematic side view for showing the specific example of FIG. 1, (c) Schematic top view for showing the specific example of FIG. Flowchart relating to imaging head assembly adjustment in the first embodiment Schematic configuration diagram for explaining mounting errors of multiple imaging heads (A) Schematic configuration diagram of the imaging unit in the first embodiment, (b) A diagram showing the relationship between the optical lens movement amount and the focus movement amount in the first embodiment. The figure which shows the relationship between the movement amount of the optical lens in this Embodiment 1, and magnification. The figure which shows the relationship between the optical lens movement amount in this Embodiment 1, and the variation | change_quantity of a versus projection pattern. The figure which shows the relationship between the projection pattern in this Embodiment 1, and the cell of an image pick-up element. Flowchart for deriving an attachment error of the imaging unit in the first embodiment (A) Schematic configuration diagram of imaging head of inspection apparatus in Embodiment 2 of the present invention, (b) Enlarged view of main part of imaging head in Embodiment 2. (A) Schematic front view for showing a specific example of FIG. 10, (b) Schematic side view for showing a specific example of FIG. 10 (a), (c) For showing a specific example of FIG. 10 (a) Outline top view Schematic configuration diagram of an imaging head in Embodiment 3 of the present invention Schematic configuration diagram of a modified example of the imaging head in the third embodiment Schematic showing a conventional pattern inspection system

Embodiments of the present invention will be described below with reference to FIGS.
(Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating the configuration and principle of an imaging head used in the pattern inspection apparatus according to the first embodiment of the present invention.

  The imaging head 100 is used for reading the pattern 3 formed on the surface of the inspection object 2 placed on the moving table 1. In this imaging head 100, three imaging units 5 a, 5 b, 5 c are fixed on the gantry 4.

  The inspection object 2 is a substrate of a display panel such as a plasma display panel or a liquid crystal panel. More specifically, the display panel is bonded with a gap between the front plate and the back plate. In the case of a plasma display panel, the internal space is partitioned into discharge areas for each display color. In the case of a liquid crystal panel, the interior space is filled with liquid crystal. The pattern 3 is formed on the front plate or the back plate, and pattern inspection of the front plate or the back plate before bonding is performed.

  The imaging units 5a, 5b, and 5c are adjusted by the control device 6 so that the inspection object 2 can be imaged in a state where the pattern 3 is in focus. The control device 6 executes the assembly adjustment flowchart shown in FIG. 3 during assembly, which will be described later in detail.

  The image pickup unit 5a is arranged between the image pickup device 7a and the image pickup device 7a and the inspection object 2 and can move vertically to the surface of the inspection object 2 in the approaching / separating direction (hereinafter referred to as the Z-axis direction). The optical lens system unit 8a.

The imaging unit 5b includes an imaging element 7b and an optical lens system unit 8b that is disposed between the imaging element 7b and the inspection object 2 and can move vertically in the Z-axis direction.
The imaging unit 5c includes an imaging element 7c, and an optical lens system unit 8c that is disposed between the imaging element 7c and the inspection object 2 and can move vertically in the Z-axis direction.

In order to simplify the explanation, only the minimum necessary components are shown in FIG.
In addition, the optical lens system units 8a, 8b, and 8c may have a configuration using a plurality of lens groups or an aspherical lens in order to obtain necessary reading characteristics. A drive system for moving the optical lens system units 8a, 8b, and 8c and a control device for controlling the drive are not shown.

  As the imaging elements 7a, 7b, and 7c, semiconductor solid-state imaging elements such as CMOS devices, CCD devices, and MOS devices are used. These include a line type and an area type. In the present invention, either a line type or an area type can be used.

  By the relative movement of the inspection object 2 and the gantry 4, the imaging units 5 a, 5 b, and 5 c attached to the gantry 4 scan the area to which the inspection object 2 is assigned and read the pattern 3. In the present embodiment, the inspection object 2 and the gantry 4 are moved relative to each other in a direction perpendicular to the paper surface of FIG. 1 to scan the inspection object 2 in the X-axis direction.

FIG. 2A, FIG. 2B, and FIG. 2C are diagrams showing specific examples of FIG.
Both sides of the gantry 4 are supported by the guides 9a and 9b so as to be slidable in the Z-axis direction with respect to the surface of the inspection object 2. A screw shaft 11 screwed into a screw hole formed in the gantry 4 is rotationally driven by a main motor 10 attached to a fixed stage 12 so that the gantry 4 is in the Z-axis direction with respect to the surface of the inspection object 2. Drive slide. Here, the Z-axis drive unit 30 includes the screw shaft 11 and the main motor 10.

  An image sensor unit 13a having an image sensor 7a, an image sensor unit 13b having an image sensor 7b, and an image sensor unit 13c having an image sensor 7c are arranged on the gantry 4 arranged along the Y axis direction orthogonal to the X axis direction. , And are fixed at predetermined intervals in the Y-axis direction.

  Furthermore, optical lens system units 8a, 8b, and 8c are attached to the gantry 4 so as to be slidable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The optical lens system units 8a, 8b, and 8c are attached to the image sensor unit 13a, the image sensor unit 13b, and the image sensor unit 13c with their optical axes aligned.

  The optical lens system unit 8a is positioned by a guide 14a extending on one side in the Z-axis direction, screwed into a screw hole formed on the other side, and a first screw shaft whose axis is parallel to the guide 14a. It is supported by 15a. In the optical lens system unit 8a, the first screw shaft 15a is rotationally driven by a first motor 16a attached to the gantry 4, and is slid in the Z-axis direction. Similarly, in the optical lens system unit 8b, the second screw shaft 15b is rotationally driven by the second motor 16b attached to the gantry 4 and is slid in the Z-axis direction. The optical lens system unit 8c rotationally drives the third screw shaft 15c by a third motor 16c attached to the gantry 4 and slides it in the Z-axis direction. The optical lens system unit 8b is positioned by the guide 14b, and the optical lens system unit 8c is positioned by the guide portion 14c.

FIG. 3 is a flowchart when the imaging head 100 is assembled.
First, in step S <b> 1, the imaging units 5 a, 5 b, and 5 c are fixed on the gantry 4 in a state where the positions in the vertical direction (Z-axis direction) are aligned with the plane of the inspection object 2. At this time, the imaging devices 7a, 7b, and 7c of the imaging units 5a, 5b, and 5c include attachment errors Δz1 and Δz2 of about 100 μm in the Z-axis direction as shown in FIG.

  In step S2, the main motor 10 is operated so that the gantry 4 is moved in the Z-axis direction and adjusted so that the focus of the imaging unit 5a matches the pattern 3. Here, the state in which the imaging unit 5a is focused on the pattern 3 is a state in which a focused image of the pattern 3 is obtained by the imaging device 7a.

  When the imaging unit 5a is in focus, in step S3, the magnification of the imaging unit 5a is measured. In step S4, it is determined whether or not the magnification measured in step S3 is a magnification suitable for the pattern.

If it is determined in step S4 that the magnification is not suitable, the magnification of the imaging unit 5a is adjusted in step S5.
The routine of steps S2, S3, S4 and S5 is repeated to determine whether the magnification is suitable for the pattern. If it is determined in step S4 that the magnification is suitable, it is determined that the adjustment of the imaging unit 5a is completed. When the adjustment of the imaging unit 5a is completed, step S6 is then executed.

  In step S6, adjustment is performed so that the focus of the imaging unit 5b and the imaging unit 5c matches the pattern 3. Specifically, first, the second motor 16b is operated to move the optical lens system unit 8b in the Z-axis direction so that the focused image of the pattern 3 can be obtained by the image pickup device 7b of the image pickup unit 5b. Subsequently, the third motor 16c is operated to move the optical lens system unit 8c in the Z-axis direction so that a focused image of the pattern 3 can be obtained by the imaging element 7c of the imaging unit 5c.

  By adjusting the imaging units 5a, 5b, and 5c in this way, the attachment errors Δz1 and Δz2 that have occurred in step S1 of the imaging units 5a, 5b, and 5c can be complemented. However, when adjustment is performed in this way, the magnifications of the images of the imaging units 5a, 5b, and 5c are slightly different. That is, in the present embodiment, the adjustment of the magnification of the imaging unit and the focusing on the pattern are performed using the adjustment flow shown in FIG.

  In the imaging head of the present embodiment, only the optical lens system units 8a, 8b, 8c of the imaging units 5a, 5b, 5c need to be moved. That is, the common mount 4 for the plurality of imaging units 5a, 5b, and 5c may have only one drive mechanism that drives in the Z-axis direction. Therefore, the configuration can be simplified compared to the case where a drive mechanism that drives in the Z-axis direction is provided for each imaging unit. Since the configuration is simple, the driving accuracy of the driving mechanism is good, and the cost of the driving mechanism is reduced.

  FIGS. 5A and 5B are diagrams illustrating the configuration and performance of the imaging unit according to the present embodiment. Since the imaging units 5a, 5b, and 5c have the same structure, the imaging unit 5b will be described here.

  FIG. 5A is a schematic configuration diagram of the imaging unit 5b. FIG. 5B is a diagram showing the relationship between the amount of movement of the optical lens and the amount of movement of the focal point when the distance between the image sensor 7b and the optical lens system unit 8b is changed. The graph in FIG. 5B is a graph measured by moving the optical lens system unit 8b in a state where the image sensor 7b is fixed.

In the present embodiment, the following conditions are satisfied in the lens formula 1 / F = 1 / L ₁ + 1 / L ₂ and M = L ₂ / L ₁ .
F: Focal length of optical lens system unit 8b = 15 mm
L ₁ : distance between the optical lens system unit 8b and the inspection object 2 = 20 mm
(When the amount of movement is 0)
L ₂ : Distance between the optical lens system unit 8b and the image sensor 7b = 60 mm
(When the amount of movement is 0)
M: Magnification = 3 (when movement amount is 0)
In the above relationship, when only the optical lens system unit 8b is moved, the optical lens moving amount and the focal point moving amount are substantially the same.

  FIG. 6 shows changes in the optical lens movement amount and magnification. FIG. 7 shows the amount of change in expansion / contraction when a 100 μm pattern is projected onto the image sensor 7 b with a projection pattern of 300 μm.

  From these figures, when the optical lens system unit 8b is moved 0.1 mm upward (Z-axis direction), the focal point moves from the surface of the inspection object 2 by about 0.1 mm in the Z-axis direction from FIG. I understand that When the focal point moves in the Z-axis direction by about 0.1 mm, it can be seen from FIG. 7 that the projection pattern of 100 μm is reduced from 300 μm to about 0.6 μm.

  Generally, when the imaging head 100 is assembled, an attachment error to the gantry 4 of about ± 50 μm occurs. In the present embodiment, this generated error can be canceled by moving the optical lens system unit 8b. Even when the optical lens system unit 8b is moved up to 100 μm to cancel, the expansion / contraction of the pattern 3 caused by the change in magnification is 0.6 μm with respect to the 300 μm pattern.

Next, whether or not there is a problem in pattern inspection in this embodiment will be considered. Hereinafter, the influence of 0.6 μm on a 300 μm pattern will be described.
First, a pattern inspection apparatus using the imaging head 100 described so far will be described.

  The pattern inspection apparatus first scans a pattern periodically arranged on the surface of a planar inspection object with the imaging head 100 to generate digital data. Then, the control device 6 compares the pattern data of the part separated by a certain period with the operated pattern, and detects the defect of the pattern.

  A method of performing a comparison inspection with a pattern of a different part in pattern data (hereinafter referred to as a comparison inspection method) is also used in the technique described in Patent Document 1. In the pattern inspection apparatus, since a solid-state imaging device is used as an imaging device, when one pitch of the pattern is projected onto the imaging device, it is necessary that the one pitch of the pattern surely fits in an integer number of imaging cells. This is because if one pitch of the pattern does not fit in an integer number of imaging cells, when comparing data, it is determined that the pattern for one cycle is different at the edge, and false detection occurs. is there. For this purpose, in the comparative inspection method, data obtained by optimizing the magnification of the optical lens system unit is comparatively inspected.

  The imaging head 100 of the present embodiment satisfies the magnification tolerance required for the comparative inspection in the comparative inspection method, although the magnifications of the imaging units 5a, 5b, and 5c are slightly different for focusing.

Subsequently, in the present embodiment, a relationship in which a 300 μm pattern image on the image sensor 7b is changed by 0.6 μm due to a change in magnification generated for focusing will be described with reference to FIG.
As shown in FIG. 8, the image sensor 7b of the present embodiment has a cell size of 10 μm. The pattern 3 of the 100 μm inspection object 2 described with reference to FIG. 1 is projected as a 300 μm projection image 17 onto 30 cells having a cell size of 10 μm by the optical lens system unit 8b having the optimum magnification.

As shown in FIG. 8, since the cell size of this embodiment is 10 μm, the deficiency of 0.6 μm is 6% of the cell.
In order not to affect the detection result in the comparative inspection method, it is to what extent the amount of protrusion of the projection image cell generated for focusing is permissible. Note that the amount of protrusion of the cell is converted into an allowable range of magnification. The amount of movement of the optical lens system unit 8b needs to be determined so as to be within the allowable range of the magnification.

  In the present embodiment, when the signs are set as follows, the allowable amount of magnification (allowable magnification M) of the optical lens system unit 8b of the imaging unit 5b needs to be suppressed within the range of the following equation (1). is there.

C (N−ΔN) / P <M <C (N + ΔN) / P (1)
C: element pitch of the image sensor 7b, P: pitch of the pattern 3, N: number of elements of the image sensor 7b within the pitch of the projected image 17 (integer), ΔN: allowable amount (element) of the projected image 17. .

FIG. 9 shows a series of flows until the control device 6 derives the allowable amount of the mounting error of the imaging units 5a, 5b, 5c.
Here, the element pitch C = 10, the pitch P = 100, and the number of elements N = 30. The allowable amount ΔN is a unit of how many cells are the allowable protrusion of the projection pattern.

  First, in step S11, the allowable protrusion of ΔN is determined based on the inspection accuracy required for the inspection object 2 and the like. For example, the allowable protrusion amount is 6%, that is, ΔN = 0.06 cells.

  Next, in step S12, the allowable magnification M is derived by substituting the protrusion allowable amount ΔN into the above equation (1). When applied to the example described with reference to FIG. 7, the allowable magnification M is a condition of the following expression (2).

2.994 <M <3.006 (2)
When the allowable magnification M is derived, in step S13, the allowable movement amount of the optical lens system units 8b and 8c is determined.

  The relationship between the amount of movement of the optical lens system units 8b and 8c and the magnification is determined by the optical design of the imaging units 5a, 5b and 5c. The allowable movement amount based on this magnification becomes the allowable attachment error amount of each imaging unit 5a, 5b, 5c in step S14.

  From these relationships, in the present embodiment, it can be seen that the optical lens system units 8b and 8c can move to 0.1 mm. Therefore, the focal position can be moved to 0.1 mm, and there is no influence even if the focusing error of ± 50 μm is complemented and the focus of each imaging unit 5 a, 5 b, 5 c is adjusted to the surface of the inspection object 2. It could be confirmed. That is, in the configuration of the present embodiment, it was confirmed that the obtained pattern data was suitable for the comparative inspection method.

  The configuration of the imaging unit 5b described above is basic. However, depending on the optical lens design, a more suitable configuration can be designed. Below, the conditions of the suitable structure are demonstrated using the imaging unit 5b.

  First, the minimum condition of a suitable configuration in the present embodiment is to fix the imaging unit 5b by fixing the imaging element 7b and moving the optical lens system unit 8b. At this time, since the distance between the optical lens system unit 8b and the imaging element 7b changes, the magnification of the imaging unit 5b changes. However, as described above, since the change in magnification is so small that it does not affect the comparison inspection method, focusing can be performed within a magnification allowable amount suitable for the comparison inspection method.

  As an example of an optical lens design that satisfies such a condition, there is a design in which the distance between the optical lens system unit 8b and the image sensor 7b is longer. Even if each imaging unit 5a, 5b, 5c has the same magnification, the distance between the optical lens system unit 8b and the imaging element 7b and the distance between the optical lens system unit 8c and the imaging element 7c are designed to be longer. The one is preferred. This is because the larger the distance between the optical lens system unit 8b and the image sensor 7b, and the longer the distance between the optical lens system unit 8c and the image sensor 7c, the magnification when the distance between the optical lens system unit 8b and the image sensor 7b is changed. This is because the amount of change of becomes smaller. In addition, since the amount of change in magnification when the distance between the optical lens system unit 8c and the image sensor 7c is changed is small, the allowable movement distance of the optical lens system units 8b and 8c within the magnification change allowable amount is long.

  By designing under such conditions, even when the mounting accuracy of the imaging units 5a, 5b, 5c is rough, the mounting error can be complemented. In addition, when it is necessary to narrow the range of allowable magnification change, that is, when the magnification error between the imaging units 5a, 5b, and 5c needs to be further reduced, such an optical lens design is performed. Can respond.

  It is also important to consider the depth of focus of each imaging unit 5a, 5b, 5c when the pattern 3 is projected onto the imaging elements 7a, 7b, 7c. That is, when the depth of focus is deep, there is no problem of focusing, but the depth of focus depends on NA which is the numerical aperture of the optical lens system units 8a, 8b, and 8c. In order to make the projection image obtained when the pattern 3 is projected onto the image pickup devices 7a, 7b, and 7c higher in definition, it is necessary to design the optical lens system units 8a, 8b, and 8c to have a high NA.

  In order to increase the NA of the optical lens system unit, it is preferable to design the imaging unit with a shallow depth of focus. This is because, when the depth of focus is deep, the problem of focusing is eliminated, but the depth of focus is inevitably shallow for high definition of the projected image. In addition, when the depth of focus is deep, a structure behind the pattern is captured as a pattern projection image, and thus accurate imaging may not be possible. From this point of view, it is necessary to make the depth of focus of the imaging unit shallow. In the present embodiment, the depth of focus of the imaging unit is preferably 20 μm or less.

  It should be noted that the present invention also has a feature that a drive mechanism that normally drives each imaging unit and a drive mechanism in the imaging unit are omitted. Therefore, it may be applicable not only to an inspection device but also to a scanner device that reads a precise image at high speed.

  In addition, this pattern inspection apparatus is characterized in that a drive mechanism for driving each imaging unit and a drive mechanism in the imaging unit are omitted. Therefore, the pattern inspection apparatus can be manufactured at low cost.

(Embodiment 2)
FIG. 10A is a schematic configuration diagram illustrating the configuration and principle of the imaging head used in the pattern inspection apparatus according to the second embodiment of the present invention. FIG.10 (b) is an enlarged view of the A section in Fig.10 (a).

The imaging head 200 according to the second embodiment reads the pattern 3 formed on the surface of the inspection object 2 placed on the moving table 1.
The gantry 24 is supported so as to be slidable in the Z-axis direction with respect to the surface of the inspection object 2. The screw shaft 11 screwed into the screw hole formed in the gantry 24 is rotationally driven by the main motor 10 attached to the fixed stage 12, and the gantry 24 is moved in the Z-axis direction with respect to the surface of the inspection object 2. Slide driven.

In the present embodiment, four image pickup units 25a, 25b, 25c, and 25d are fixed on the gantry 24.
These imaging units 25a to 25d are adjusted at the time of assembling to the gantry 24 so that the inspection object 2 can be imaged in a state where the pattern 3 is in focus.

  The imaging unit 25a includes an imaging element unit 26a and an optical lens system unit 28a. The image sensor unit 26 a includes an image sensor 7 a and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The optical lens system unit 28 a is disposed between the image sensor unit 26 a and the inspection object 2 and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. In the present embodiment, the image sensor unit 26a and the optical lens system unit 28a are connected to form a single unit by a drive unit 27a that can adjust the distance between them. The image sensor unit 26a and the optical lens system unit 28a are attached to the gantry 24 via the drive unit 27a.

  The imaging unit 25b includes an imaging element unit 26b and an optical lens system unit 28b. The image sensor unit 26b includes an image sensor 7b, and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The optical lens system unit 28b is disposed between the image sensor unit 26b and the inspection object 2, and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The image sensor unit 26b and the optical lens system unit 28b are connected to form a single unit by a drive unit 27b that can adjust the distance between them. The image sensor unit 26b and the optical lens system unit 28b are attached to the gantry 24 via the drive unit 27b.

  The imaging unit 25c includes an imaging element unit 26c and an optical lens system unit 28c. The image sensor unit 26 c includes an image sensor 7 c and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The optical lens system unit 28c is disposed between the image sensor unit 26c and the inspection object 2, and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The imaging element unit 26c and the optical lens system unit 28c are connected by a drive unit 27c that can adjust the distance between them. The image sensor unit 26c and the optical lens system unit 28c are attached to the gantry 24 via the drive unit 27c.

  The imaging unit 25d includes an imaging element unit 26d and an optical lens system unit 28d. The image sensor unit 26d includes an image sensor 7d and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The optical lens system unit 28d is disposed between the image sensor unit 26d and the inspection object 2, and is movable perpendicularly to the surface of the inspection object 2 in the Z-axis direction. The imaging element unit 26d and the optical lens system unit 28d are connected by a drive unit 27d that can adjust the distance between them. The image sensor unit 26d and the optical lens system unit 28d are attached to the gantry 24 via the drive unit 27d.

  Depending on the inspection object or the optical configuration of the imaging units 25a to 25d, it may be required that the accuracy of the tilt angle with respect to the inspection object is high. In such a case, as shown in FIG. 10B, the imaging units 25a to 25d are arranged between the imaging element units 26a to 26d and the drive units 27a to 27d with rolls, pitches, and pitches around three orthogonal axes. It is preferable to attach an adjustment shaft mechanism 29 that can adjust the tilt in the three directions Ro, Pi, and Ya of the yaw.

  With this configuration, the distance between the optical lens system unit 28a and the image sensor 7a can be adjusted by controlling the drive unit 27a with the control device 6. Similarly, the distance between the optical lens system unit 28b and the image sensor 7b can be adjusted by controlling the drive unit 27b with the control device 6. Similarly, the distance between the optical lens system unit 28c and the image sensor 7c can be adjusted by controlling the drive unit 27c with the control device 6. Similarly, the distance between the optical lens system unit 28d and the image sensor 7d can be adjusted by controlling the drive unit 27d with the control device 6. Thus, by adjusting the distance between the optical lens system unit and the image sensor, the focal planes of the image pickup units 25a to 25d can be adjusted to the same plane, and the image pickup units 25a to 25d are driven by a single Z-axis. The unit 25 can be used for simultaneous movement. Here, the Z-axis drive unit 30 includes the screw shaft 11 and the main motor 10.

FIGS. 11A, 11B, and 11C show specific examples of FIG.
The gantry 24 arranged along the Y-axis direction is supported so as to be slidable in the Z-axis direction with respect to the surface of the inspection object 2 with both sides positioned by the guides 9a and 9b. Imaging units 25a to 25d are fixed to the gantry 24 at predetermined intervals in the Y-axis direction.

  The image pickup device unit 26a of the image pickup unit 25a is positioned by a guide 34 having one side extending in the Z-axis direction, screwed into a screw hole formed on the other side, and a shaft whose axis is parallel to the guide 34. It is supported by the shaft 36. The screw shaft 36 is rotationally driven by a motor 38 attached to the gantry 24, and the image sensor unit 26a slides in the Z-axis direction. The optical lens system unit 28a having the optical axis aligned with the image pickup device unit 26a is positioned by a guide 35 extending on one side in the Z-axis direction and screwed into a screw hole formed on the other side. The center is supported by a screw shaft 37 parallel to the guide 35. The screw shaft 37 is rotationally driven by a motor 39 attached to the gantry 24, and the optical lens system unit 28a slides in the Z-axis direction.

  The imaging units 25b to 25d are the same as the imaging unit 25a. The imaging element unit 26b of the imaging unit 25b is driven to slide in the Z-axis direction by rotating the screw shaft 40 by a motor 42. The optical lens system unit 28b of the imaging unit 25b is driven to slide in the Z-axis direction by rotating the screw shaft 41 by a motor 43.

  The image pickup device unit 26c of the image pickup unit 25c is driven to slide in the Z-axis direction by rotating the screw shaft 44 by a motor 46. The optical lens system unit 28c of the imaging unit 25c is driven to slide in the Z-axis direction by rotating the screw shaft 45 by a motor 47.

  The imaging element unit 26d of the imaging unit 25d is driven to slide in the Z-axis direction by rotating the screw shaft 48 by the motor 50. The optical lens system unit 28d of the imaging unit 25d rotates the screw shaft 49 by the motor 51 and slides it in the Z-axis direction.

(Embodiment 3)
FIG. 12 is a schematic plan view of the pattern inspection apparatus according to the third embodiment of the present invention.

  In the third embodiment, the gantry 61 corresponding to the gantry 4 of the first embodiment or the gantry 24 of the second embodiment moves in the Z-axis direction by operating the main motor 10 of the Z-axis drive unit 30. A plurality of imaging units are attached to the gantry 61 in two rows so as to sandwich the gantry 61. Eight imaging units 62a to 62h are attached to the gantry 61 of the present embodiment. Since the specific attachment method is the same as the configuration of the first or second embodiment, the description thereof is omitted.

  By attaching a plurality of imaging units to the gantry 61 in this way, the inspection area of the inspection object 2 can be divided into two areas. For this reason, the movement distance of the inspection object 2 is half the distance in the case of one row. Can be reduced. As a result, the inspection speed can be increased and the inspection time can be shortened as compared with the configurations of the first and second embodiments.

FIG. 13 shows a modification of the third embodiment.
In the modification of the third embodiment, similarly to the configuration shown in FIG. 12 with respect to the gantry 61, one row of eight imaging units 62a, 62c, 62e, and 62g and imaging units 62b, 62d, 62f, and 62h. It is arranged in two rows with another row. In FIG. 13, when reading is performed by moving the inspection object 2 with respect to the gantry 61 in the X-axis direction, the imaging unit 62 a reads the area E <b> 1 of the inspection surface of the inspection object 2 to inspect the inspection object 2. The imaging unit 62b reads the area E2 of the surface, the imaging unit 62c reads the area E3 of the inspection surface of the inspection object 2, and the imaging unit 62d reads the area E4 of the inspection surface of the inspection object 2. Similarly, the image pickup units 62a to 62h are arranged in a staggered arrangement so that the image pickup units 62e, 62f, 62g, and 62h read the areas E5, E6, E7, and E8 on the inspection surface of the inspection object 2 in the same manner. . By adopting such an arrangement, the inspection object 2 can be efficiently inspected by one scan.

  As the main motor 10, the first motor 16a, the second motor 16b, the third motor 16c, the motors 38, 39, 42, 43, 46, 47, 50, and 51 of the above embodiments, a stepping motor or a servo motor is used. Can be used.

  The present invention can be used for pattern inspection of display panels such as plasma display panels and liquid crystal panels.

DESCRIPTION OF SYMBOLS 1 Moving table 2 Inspected object 3 Pattern 4, 24, 61 Mount 5a, 5b, 5c, 25a-25d, 62a-62h Image pickup unit 6 Control apparatus 7a-7c Image pick-up element 8a-8c, 28a-28d Optical lens system unit 9a , 9b, 14a, 14b, 14c, 34, 35 Guide 10 Main motor 11, 36, 37, 40, 41, 44, 45, 48, 49 Screw shaft 12 Fixed stage 13a, 13b, 13c, 26a to 26d Image sensor unit 15a to 15c First to third screw shafts 16a to 16c First to third motors 27a to 27d Drive unit 29 Adjustment shaft mechanism 30 Z-axis drive unit 38, 39, 42, 43, 46, 47, 50, 51 Motor E1 E8 Area 100 of inspection surface of inspection object 2 Imaging head 200 Imaging head

Claims (8)

A control device that scans a pattern periodically arranged on the surface of an object to be inspected and detects a defect in the pattern in comparison with an image pickup head on which an image pickup element and an optical lens system unit are mounted, and a portion separated by a fixed period In a pattern inspection apparatus comprising:
The imaging head has a drive unit that moves a gantry to which a plurality of imaging units are fixed in an approaching and separating direction with respect to the surface of the inspection object,
The imaging unit includes an imaging element unit having an imaging element, and an optical lens system unit that is movable in the approaching and separating direction,
The control device moves the optical lens system unit so that the magnification M of the optical lens system unit is in the following range, and focuses each imaging unit on the surface of the object to be inspected. A pattern inspection apparatus for detecting a defect.
C (N−ΔN) / P <M <C (N + ΔN) / P
Where C: element pitch of the image sensor,
P: pitch of the pattern,
N: the number of the imaging elements within the projected image pitch of the pattern,
ΔN: Allowable element of the projected image The pattern inspection apparatus according to claim 1, wherein a depth of focus of the optical lens system unit is 20 μm or less. The optical lens system unit has a small amount of change in magnification with respect to a change in distance between the optical lens system unit and the image sensor due to the focusing, and a distance between the optical lens system unit and the image sensor. The pattern inspection apparatus according to claim 1, wherein the pattern inspection apparatus is designed to be long. The imaging unit is configured to be divided into two units, an optical lens system unit and an imaging element unit, and the imaging unit and the optical lens system unit are connected via a drive unit that drives in a straight direction,
The pattern inspection apparatus according to claim 1, wherein the control device adjusts a distance between the optical lens system unit and the imaging element unit by controlling the drive unit. The pattern inspection apparatus according to claim 3, wherein the imaging element unit is attached to the gantry via an adjustment shaft mechanism that adjusts a tilt angle between a focal plane and an object to be inspected. An imaging head for a pattern inspection apparatus that images a pattern arranged in parallel on a surface to be inspected by a plurality of imaging units,
A gantry that is movable in a direction perpendicular to the surface to be inspected, and a plurality of imaging units attached to the gantry,
The imaging head for a pattern inspection apparatus, wherein the imaging unit includes an imaging element and an optical lens system unit movable in the vertical direction. A pattern inspection method in which a pattern periodically arranged on the surface of an object to be inspected is scanned by an image pickup unit equipped with an image pickup element and an optical lens system unit, and a defect of the pattern is detected by comparison with a portion separated by a fixed period. In
The optical lens system unit is moved so that the magnification M of the optical lens system unit is within the following range, and the focus of each imaging unit is focused on the surface of the object to be inspected. A pattern inspection method characterized by detecting.
C (N−ΔN) / P <M <C (N + ΔN) / P
Where C: element pitch of the image sensor,
P: pitch of the pattern,
N: the number of the imaging elements within the projected image pitch of the pattern,
ΔN: Allowable element of the projected image The optical lens system unit has a small amount of change in magnification with respect to a change in distance between the optical lens system unit and the image sensor due to the focusing, and a distance between the optical lens system unit and the image sensor. The pattern inspection method according to claim 7, wherein the pattern inspection method is designed to be long.

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