JP2012242268A - Inspection device and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device that determines reflection in a short time in detecting unevenness defects of an inspected object having a periodic pattern, and reduces the time for inspecting a large-area inspected body, and to provide an inspection method.SOLUTION: The inspection device includes: conveyance means for conveying a substrate placed thereon; first and second lighting means for illuminating the substrate; first lighting angle changing means for changing a lighting angle of the first lighting means; second lighting angle changing means for changing a lighting angle of the second lighting means; first imaging means for imaging the substrate illuminated by the first lighting means; second imaging means for imaging the substrate illuminated by the second lighting means; an image processing part for processing the images obtained by the first and second imaging means; and a control part for controlling the conveyance means, the first and second lighting means, the first and second lighting angle changing means, and the first and second imaging means.

Description

  The present invention relates to an inspection apparatus and an inspection method for inspecting a pattern irregularity defect in an inspection object having a periodic pattern.

  A periodic pattern refers to an aggregate of patterns in which a certain shape is arranged with a certain interval. For example, a one-dimensional periodic pattern in which stripe-like patterns are arranged at a predetermined period, or a matrix-like pattern in which island-like or grid-like unit patterns are arranged at a predetermined period, and the like are applicable. As an example of an object to be inspected having a periodic pattern, a photomask used in an exposure process of a photolithography process when manufacturing a semiconductor device, an imaging device, a display device, and the like can be given. Further examples include a color filter and a black matrix used for an imaging device and a display device.

  In the inspection object having such a periodic pattern, when an abnormality occurs in the period or individual unit pattern shape, it is observed as a mura defect.

  A non-uniformity defect in a photomask used when manufacturing an inspection object having a periodic pattern, for example, a display device such as an imaging device such as a CCD or a CMOS or various display devices, is caused by a periodic shift or position of a periodic pixel pattern. In many cases, fluctuations such as deviation and size change are caused by regular arrangement. Therefore, it is difficult to find by individual pattern inspection, and is a defect that can be recognized only when a periodic pattern is observed in a wide area.

  Conventional unevenness inspection for periodic patterns takes a transmission image using coaxial transmission illumination or flat illumination, and compares the light intensity in each image to visually recognize the normal portion and the unevenness defect portion. . However, the difference in light intensity between the normal part and the mura defect part is not always large, and the contrast of the obtained image is low. For this reason, an improvement in contrast is devised by devising an intensity difference processing method for low-contrast images, and inspection is performed by extracting a mura defect portion (see Patent Document 1).

  In recent years, the periodic patterns used in these products have been further miniaturized and apertured due to the miniaturization of semiconductor circuits, the development of display devices aiming at fine and high luminance output, and the development of imaging devices with high sensitivity. There is a tendency for the ratio of parts to increase. In the future, a periodic pattern irregularity inspection apparatus and unevenness inspection method having a larger opening and a finer shape will be required.

  There is a limit to the conventional method for detecting a mura defect based on the intensity (brightness) of light depending on the amplitude of light. In an image that captures unevenness of the light shielding part of the lattice-like periodic pattern, especially unevenness of a pattern with a large opening, it is not possible to expect an improvement in contrast between the normal part and the uneven defect part. In the inspection in the case of an image having a low contrast, there is a problem that only an inspection ability lower than the visual sensory inspection method can be achieved.

Therefore, for example, an inspection apparatus disclosed in Patent Document 2 has been proposed for the purpose of stably and highly accurately detecting a periodic pattern, for example, a mura defect occurring in a black matrix. The inspection apparatus of Patent Document 2 irradiates an object to be inspected with illumination light, and picks up and inspects an image of transmitted diffraction light generated by a periodic pattern. In the normal part of the periodic pattern, the shape and pitch of the openings are constant, so that they interfere with each other and generate diffracted light in a certain direction. On the other hand, since the shape and pitch of the opening are irregular in the mura defect portion, diffracted light is generated with various intensities in various directions according to the shape and pitch. In this inspection apparatus, the mura defect portion is detected from the difference in the diffracted light intensity contrast between the normal portion and the mura defect portion.

  An example of an inspection object having a periodic pattern is a photomask for an imaging apparatus. A photomask is provided with a light shielding film such as chromium or a halftone film such as MoSi on a transparent substrate. It is known to be formed by forming a predetermined pattern by being removed and used in the manufacturing process of a semiconductor circuit, an imaging device, a display device and the like.

  In the production of a photomask, first, a photoresist is applied to a light-shielding film (or halftone film) formed on a transparent substrate. Next, a predetermined pattern is drawn on the photoresist by a drawing apparatus. Thereafter, the drawn photoresist film is developed, and either the drawn portion or the non-drawn portion is selectively removed. Using the photoresist film left by development as a mask, the pattern shape is etched into the light shielding film, and then the remaining photoresist is removed to complete the photomask. Etching techniques include wet etching using a liquid that is corrosive to the light shielding film, and dry etching using a gas that is corrosive to the light shielding film.

  In a photomask, an electron beam drawing apparatus or a laser beam drawing apparatus is generally used when drawing a pattern. In these pattern drawing apparatuses, a step-and-repeat method in which, after drawing a pattern in an area of a predetermined size (drawing unit area) on a photomask, the pattern is moved to the next drawing unit area and drawn therein. To draw the pattern of the entire photomask.

  In the photomask drawing process, it is known that fluctuations in the drawing pattern such as pitch deviation, size change, and position deviation continuously occur at the order of several nanometers at the boundary between a drawing unit area and an adjacent drawing unit area. Yes. In other words, the mura defect tends to occur in the period of the size of the drawing unit area, and the generation pattern and in-plane distribution of the mura defect in the periodic pattern area may depend on the drawing unit area shape. For example, when the shape of the drawing unit region is a band shape, an image in which the band or line is regularly aligned with the period of the size of the drawing unit region may be seen as a mura defect. If the shape of the drawing unit area is rectangular, the uneven defect may be seen as an image resembling a checkered pattern with shading. In this way, the mura defect may be seen as an artificial pattern.

  In the object to be inspected, which is the object of such an inspection apparatus or inspection method for detecting a mura defect, a pattern having a shape other than the periodic pattern may be provided around the periodic pattern. For example, in a semiconductor product, it is an alignment pattern used for alignment for exposure in a wiring or photolithography process. In addition, on a photomask for an imaging device such as a CCD or CMOS, a wiring pattern for taking out a signal may be arranged around a region where a periodic pattern for manufacturing a pixel is provided. In the inspection apparatus and inspection method for detecting the mura defect described above, illumination is applied to the pattern outside the inspection area, and the reflected light or scattered light may be reflected as stray light in the inspection area of the periodic pattern. . It is necessary to inspect these reflections while distinguishing them from the actual mura defects.

  The operation of distinguishing between the mura defect and the reflection may require multiple inspections using different inspection methods or different inspection apparatuses, which is a problem that leads to reduced time and operational efficiency of the apparatus. Therefore, an inspection apparatus and an inspection method require an apparatus structure and an optical system that do not cause reflection.

  It is known that the position of reflection changes depending on the lighting conditions. For this reason, as an example of an operation for distinguishing between the mura defect and the reflection, there is a case in which a method for discriminating from the actual mura defect by changing the irradiation angle of the illumination light may be employed.

  As the wiring and alignment pattern installed on the photomask, a pattern composed of a rectangle or a straight line is often used. For this reason, stray light and reflection caused by these patterns are also rectangular or linear patterns. When such a reflection occurs, it is not easy to determine whether a mura defect is actually generated in the photomask or whether it is a reflection. When acquiring an image of a mura defect with a camera or the like, it is necessary to inspect and confirm again the location where an actual mura defect and a defect suspected of being reflected are detected by another inspection apparatus or method.

  In order to avoid the addition of these steps, it is necessary to establish an inspection method that hardly causes reflection. For this purpose, for example, a mechanism as in Patent Document 3 has been proposed.

  However, the inspection method disclosed in Patent Document 3 places restrictions on the illumination angle and the inspectable area. When a mura defect is imaged, the contrast of the image varies greatly depending on the angle of illumination. For this reason, if the illumination angle is limited by the pattern arrangement in the photomask, there is a possibility that the illumination condition that provides the most contrast between the mura defect and the normal part cannot be selected. Even if the periodic pattern that is the object to be inspected is installed with the same unit pattern and the same period, the illumination angle allowed at the time of inspection changes depending on the surrounding pattern arrangement, so evaluation under the same conditions can be performed. The problem of disappearing arises. Further, the mura defect has a possibility of occurring in every place in the inspection area of the periodic pattern, and it is not desirable to generate an area that cannot be inspected. There is a need for an inspection apparatus and an inspection method that suppress the occurrence of reflection and reduce the restrictions on the illumination conditions on the object to be inspected.

  Further, as a recent technical trend related to the production of display devices, there is an increase in the size of a glass substrate used during production. Specifically, a black matrix, a color filter, a photomask for manufacturing these, and the like are applicable. There are cases where a large glass substrate is used due to an increase in the size of each display device, and production costs are reduced by installing a plurality of small display device patterns on a single glass substrate. In the case where a plurality of small display device patterns are installed on a single glass, a step of separating the glass substrate into regions for each display device is performed after the pattern is installed. When inspecting the irregularity defect of the periodic pattern placed on a large-area glass substrate according to any of the above, the inspection time increases in proportion to the area of the glass.

  When inspecting the surface of such a large area in this way, a technique of acquiring an image of the inspection object while scanning the inspection object surface with a line sensor camera may be used. An advantage of using a line sensor camera is that a large area image can be acquired in a short time under a certain condition. When using an area sensor camera, when using lenses with the same magnification, the opposite side distance of the camera field of view is generally shorter than that of a line sensor camera. Therefore, as with the photomask drawing method described above, it is necessary to acquire an image of the surface of the object to be inspected by the step-and-repeat method, and it takes a long time compared to the line sensor camera when acquiring an image of the same area. It takes.

  On the other hand, as an advantage when using an area sensor camera, it is possible to capture changes over time at the same location. In the case of a line sensor camera, it is necessary to return the camera to the target location again and perform the imaging operation again in order to check the change over time of the same location because the relative distance to the imaging subject changes with time during imaging. Arise.

JP 2002-148210 A JP 2006-208084 A JP 2008-26306 A

  The present invention has been made in view of the above-described problems, and the object thereof is a mura defect in an object to be inspected having a periodic pattern such as a photomask for an imaging device or a photomask for a display device. It is an object of the present invention to provide an inspection apparatus and an inspection method capable of discriminating reflections in a short time and further reducing the inspection time of an object to be inspected with a large area.

In order to solve the above-mentioned problem, claim 1 of the present invention is an apparatus for inspecting a substrate having a periodic pattern formed on the substrate surface using diffracted light generated by the periodic pattern,
Transport means for placing and transporting the substrate;
A first illumination means and a second illumination means for illuminating the substrate;
First illumination angle changing means for changing the illumination angle of the first illumination means;
Second illumination angle changing means for changing the illumination angle of the second illumination means;
First imaging means for imaging the substrate illuminated by the first illumination means;
Second imaging means for imaging the substrate illuminated by the second illumination means;
An image processing unit for processing images obtained by the first imaging unit and the second imaging unit;
A controller that controls the transport unit, the first and second illumination units, the first and second illumination angle changing units, and the first and second imaging units; This is an inspection apparatus characterized by the above.

  According to a second aspect of the present invention, the first illuminating means and the second illuminating means change the illumination angle in a plane perpendicular to the substrate to be inspected and in a horizontal plane. 1. The inspection apparatus according to 1.

  A third aspect of the present invention is the inspection apparatus according to the first aspect, wherein the first imaging unit is an area camera, and the second imaging unit is a line sensor camera.

  According to a fourth aspect of the present invention, the image processing unit images a defect candidate extracted by processing an image captured by the first imaging unit by the second imaging unit, and the captured image The inspection apparatus according to claim 1, wherein a true defect is extracted from.

Claim 5 of the present invention is a method for inspecting a substrate having a periodic pattern formed on the substrate surface using diffracted light generated by the periodic pattern,
A transport process for placing and transporting the substrate;
A first illumination process and a second illumination process for illuminating the substrate;
A first illumination angle changing step of changing an illumination angle of the first illumination step;
A second illumination angle changing step of changing the illumination angle of the second illumination step;
A first imaging step of imaging the substrate illuminated by the first illumination step;
A second imaging step of imaging the substrate illuminated by the second illumination step;
An image processing step for processing images obtained by the first imaging step and the second imaging step;
Using the control process for controlling the transport process, the first and second illumination processes, the first and second illumination angle changing processes, the first imaging process and the second imaging process. This is an inspection method for inspecting a substrate on which a periodic pattern is formed.

  According to a sixth aspect of the present invention, in the first illumination step and the second illumination step, the illumination angle is changed in a plane perpendicular to the substrate to be inspected and in a horizontal plane. 5. The inspection method according to 5.

  A seventh aspect of the present invention is the inspection method according to the fifth aspect, wherein an area camera is used for the first imaging step and a line sensor camera is used for the second imaging step.

  According to an eighth aspect of the present invention, a defect candidate extracted by processing the image picked up by the first image pickup step using the image processing step is picked up by the second image pickup step to pick up the picked-up image. 6. The inspection method according to claim 5, wherein a true defect is extracted from.

  According to the periodic pattern inspection apparatus and inspection method of the present invention, in the inspection of an inspection object such as a photomask for an imaging device and a photomask for a display device, which is a periodic pattern, reflection from a detected defect is reflected. It is possible to efficiently discriminate between unevenness defects.

  Further, the image acquisition time can be shortened even for a large area to be inspected, and as a result, the inspection time can be shortened.

Schematic of one form of unevenness inspection apparatus to which the method of the present invention is applied Schematic which shows an example of the to-be-inspected object holding | maintenance stage of one form of the nonuniformity inspection apparatus to which the method of this invention is applied. Schematic diagram showing the difference in the stage movement trajectory depending on the camera imaging method Schematic showing an example of light rays inside the object to be inspected when light is projected onto a region where a periodic pattern is installed Schematic showing that the reflection position changes with the change of the illumination angle Φ Schematic diagram of light rays when light enters from a region with different refractive index into a transparent object Flow chart for distinguishing between actual defects and reflections

  When using an area sensor camera, it is possible to evaluate in real time changes in images when different illumination conditions are applied. Using this characteristic, it is advantageous for discriminating between a mura defect and a reflection.

  In addition, when using an inspection method that changes the illumination angle, when the positioning accuracy of the illumination angle is low, in order to adjust and optimize the conditions such as the illumination angle so that the contrast of the mura defect can be obtained most, There are cases where the optimum illumination angle is obtained by repeating the acquisition and the calculation of the contrast of the mura defect. In such a case, the area camera can obtain the optimum illumination angle by capturing the change in the contrast of the defect that changes according to the change in the imaging condition such as the illumination angle in the image of the mura defect.

  FIG. 1 is a configuration diagram schematically showing an inspection apparatus 50 to which a method according to an embodiment of the present invention is applied. FIG. 1 shows an apparatus configuration example for obtaining transmitted diffracted light. In addition, it is desirable to use this apparatus in a dark environment where disturbance light and stray light are reduced as much as possible.

An inspection apparatus 50 according to the present invention illustrated in FIG. 1 includes a transport unit 52 that is a transport unit that transports the substrate 10 by being placed thereon, and a first illumination device 305 that is a first illumination unit that illuminates the substrate 10. The second illumination device 315 as the second illumination means, the first arc rail 303 as the first illumination angle changing means for changing the illumination angle of the first illumination device 305, and the second illumination device. A second imaging rail 313 that is a second illumination angle changing means for changing the illumination angle 315 and a first imaging device that is a first imaging means for imaging the substrate illuminated by the first illumination device 305. 201, a second imaging device 211 that is a second imaging means for imaging a substrate illuminated by the second illumination device 315, and images obtained by the first imaging device 201 and the second imaging device 211 Image processing 71, and the transport stage 52 includes a first and second illumination device 305, 315, and first and second arcuate rails 303 and 313, a control unit 70 for controlling the.

  The transport unit 52 is an XY-θ stage that can perform the positioning operation of the device under test 10 and the substrate transport operation, and the illumination unit 300 is a first illumination device 305 that is a first illumination unit that illuminates the substrate 10. And a second lighting device 315 as second lighting means, and first and second arc rails 303 and 313. The imaging unit 200 includes a first imaging device 201 and a second imaging device 211. A periodic pattern is formed on the substrate surface of the device under test 10. Here, the substrate surface is a surface located on one side of the inspected object 10 in the thickness direction.

  The imaging unit 200 includes an area camera 201, an area camera lens 202, a line sensor camera 211, and a line sensor camera lens 212. The imaging unit 200 captures the inspected object 10 and acquires a captured image of the inspected object.

In the illumination unit 300, an arc rail 303 whose arc center is located in the optical axis direction of the area camera 201 is installed. The arc rail 303 is provided with an illumination light projecting unit 301, which guides light from the illumination device 305 using a light guide 306. By driving the illumination light projecting unit 301 on the arc rail 303, it is possible to change the irradiation angle Φ _{1 in} the direction perpendicular to the substrate surface of the object 10 to be inspected. The illumination light projecting unit 301 is adjusted so as to be able to irradiate illumination light to a predetermined position on the XY-θ stage 52 at any position on the arc rail 303. Irradiation from various irradiation angles is possible on the substrate surface of the inspection object 10 on the Y-θ stage 52. The illumination light projecting unit 301 is provided with a parallel optical system, and may include a mechanism for changing the wavelength range of the illumination light.

The illumination unit 300 further includes an arc rail 313 in which the center of the arc is located in the optical axis direction of the line sensor camera 211. To enable change of the irradiation angle [Phi ₂ in a direction perpendicular to the substrate surface of the inspection object 10 by driving the illuminating light projecting section 311 on a circular arc rail 313. These are illuminations used when imaging by the line sensor camera. The illumination light projecting unit 311 is provided with a parallel optical system. 311 and 313 are not necessarily separate components from 301 and 303, and may be replaced by moving their positions.

  Reference numerals 206 and 216 denote control devices for the imaging devices 201 and 211. Reference numeral 55 denotes an operation control device 52 of the transport device. Furthermore, 72 is an information display part, 73 is an information input part provided with the touch panel, for example.

  FIG. 2 is a view of the XY-θ stage 52 of FIG. 1 viewed from the arc rail 303 side. The XY-θ stage 52 has a function of translating the object to be inspected 10 in the X-axis direction and the Y-axis direction of FIG. 2 and a rotation direction around the substrate surface normal line orthogonal to the substrate surface. Has a function of rotating 360 ° (this axis of rotation is the Θ axis). Thus, the device under test 10 is driven in the X-axis and Y-axis directions according to a preset operation procedure. Further, by rotating the device under test 10 in-plane around the Θ axis, it is possible to adjust the illumination irradiation direction of the device under test 10 into the substrate surface. Reference numeral 12 denotes a light shielding film part to be inspected, and 13 denotes a light shielding film part to be inspected.

  The line sensor array direction of the line sensor camera 211 shown in FIG. 1 is parallel to the X direction. When acquiring an image of the inspected object 10 using a line sensor camera, first the XY-θ stage 52 is moved to the image acquisition position in the X direction, and then the image is captured by the line sensor camera while moving in the Y direction. I do.

  FIG. 3 is a schematic diagram showing the difference in the locus of stage movement depending on the imaging method of the camera. FIG. 3A shows an example in which the area camera 201 is used to image the entire object to be inspected. The image is divided into nine regions so as to cover the object to be inspected, and nine images including the object to be inspected are acquired by moving the stage eight times. On the other hand, FIG.3 (b) shows an example in the case of using the line sensor camera 211 and imaging the whole to-be-inspected object. The test object is divided into two regions, and two images including the test object are acquired by moving the stage three times.

  The control unit 70 performs operation control of devices that configure the illumination unit 300, the XY-θ stage 52, and the imaging unit 200. The image processing unit 71 inputs the output from the imaging unit 200 as image information or signal information, and performs arithmetic processing. Further, the processing result and the processed image are displayed on the display means 72.

  In FIG. 1, the imaging unit 200 and the illumination unit 300 are arranged with the substrate of the inspection object 10 interposed therebetween, but the imaging unit 200 and the illumination unit 300 may be arranged on the same surface side of the inspection object 10.

  FIG. 4 shows a light path when the periodic pattern 12 which is the inspection region is reflected by the light passing through the opening 14A. After the incident light 40 shown in FIG. 4 is incident at the incident angle + Φ from the opening 14A of the peripheral pattern, it is reflected on the back surface (surface opposite to the light shielding film surface 12) of the glass substrate 11, and then a periodic pattern is provided. The light that reaches the light shielding film surface 12 and diffracts in the vertical direction toward the lens side of the light shielding film surface is reflected in the camera 201. When an image is acquired by the camera 201 in the positional relationship of FIG. 4, the areas a and c in the figure are not reflected, but the area indicated by b is a or c due to the reflected light from the opening 14A being reflected. Looks brighter. That is, the diffracted light 41 from the light shielding film layer and the diffracted light 42 including the reflection are reflected on the camera 201. Let d be the distance from the end of the opening 14A to the position where the reflection occurs. Reference numeral 51 denotes a substrate holding jig.

4A to 5C are schematic diagrams of images obtained by capturing the pattern of the light shielding film surface 12 using the camera 201 or 211 (camera shown in FIG. 1) in the state of FIG. FIGS. 5A to 5C are schematic diagrams of captured images when the irradiation angle of the illumination light projecting unit 301 is changed to Φ ₁₁ (a), Φ ₁₂ (b), and Φ ₁₃ (c). . The case where the image brightness of the mura defect 63 is higher than that of the normal portion 61 is shown. The reflection 64 is also reflected in the region of the periodic pattern 61. When the mura defect detection process is applied to this image, not only the mura defect 63 but also the reflection 64 is detected as a mura defect.

  In the configuration of the inspection apparatus 50, a distance d indicating the range from the peripheral pattern to the reflection is obtained below.

  FIG. 6 shows a case where a peripheral pattern having an opening different from the periodic pattern to be inspected is projected at an illumination angle Φ. The projected light is incident on the transparent substrate 11 while being refracted at an angle α at the interface of the transparent substrate 11 because the refractive index of the transparent substrate 11 and air is different at the interface of the incident surface of the transparent substrate 11 of the object to be inspected. . Further, the relational expression between the incident angle Φ and the refraction angle α is expressed by Equation 1. This is represented by Equation 1.

  A part of the incident light is transmitted from the back surface of the transparent substrate 11 to the outside of the substrate, and a part of the light incident on the opening without the light shielding film is reflected on the back side of the substrate and returns to the surface having the light shielding film again. Come. The distance d from the peripheral pattern to the reflection is the distance from the position where the incident light is incident on the substrate to the position where the light is reflected back to the substrate surface. The distance d indicating the range from the peripheral pattern to the reflection is expressed by Equation 2. This is represented by Equation 2.

From the above formulas 1 and 2, the distance d indicating the range from the peripheral pattern to the reflection in the configuration of the inspection apparatus 50 is obtained by the following equation (3). This is represented by Equation 3. According to Equation 3, it can be seen that d is represented by a variable of the illumination angle Φ. Here, n ₀ is the refractive index of the space outside the substrate to be inspected, n ₁ is the refractive index of the transparent substrate 11 of the substrate to be inspected, and t is the thickness of the transparent substrate 11. Φ is an irradiation angle of the illumination light projecting unit 301. Φ is 0 ° in the direction perpendicular to the light shielding film surface to be inspected. When Φ = 90 °, the light is projected onto the inspection object from the positive Y-axis direction.

When the illumination angle Φ is changed to Φ _{11 to} Φ ₁₃ as shown in FIGS. 5D to 5F while the area to be inspected is imaged by the area camera, the range d is (a) to (c) until reflection. ) As shown. On the other hand, since the position of the mura defect 63 actually present on the pattern does not change, it is possible to easily discriminate between the actual defect and the reflection.

(Application example 1)
A flow in the case of detecting defects by applying the periodic pattern inspection apparatus according to the present invention will be described with reference to a flowchart of FIG. 7 and a schematic diagram of the unevenness inspection apparatus of FIG.

First, the stage 52 is moved directly below the area camera 201 (S1). Then turns on the illuminating light projecting portion 301 for area camera 201 (S2), the illumination angle [Phi ₁ of the illumination light projecting section 301 for area camera 201 moves to the 0 degree (S3). n = −1 (S4), n is incremented to n = n + 1 (S5), and the illumination angle Φ ₁ is Φ ₁ = Φ ₁ + n × A (where A is the image acquisition interval of Φ ₁ ). (S6), first, after the illumination angle of the illumination light projecting section 301 has moved to Φ ₁ (S7), to adjust the output of the light source device until the appropriate image brightness on the image pickup (S8). Here, adjusting the output of the light source device until an appropriate image brightness is achieved means that the output of the light source device is adjusted under conditions suitable for inspection.

Thereafter, an image by the area camera 201 is acquired (S9). Defect detection processing is performed from the acquired image (S10). At this time, it is determined whether Φ ₁ = Φ ₁ + n × A is within the movable limit angle of Φ ₁ (S11). If the movable limit angle is exceeded (YES in S11), the process proceeds to step (S12). To do. That is, in step (S12), the detected defects, and extracts those that does not change the position by the [Phi ₁ as Mura (S12).

The illumination angle Φ ₁ ′ having the highest image contrast of the extracted mura defect is extracted (S13),
The illumination 311 for the line sensor camera 211 is moved so that Φ ₂ = Φ ₁ ′ (S14), and the entire object to be inspected is imaged by the line sensor camera 211 (S16).

  The entire image of the object to be inspected obtained by the line sensor camera 211 is subjected to image processing by the image processing unit 71 to inspect the mura defect (S16).

If step (S11) in _{Φ 1 = Φ 1 + n ×} A has not exceeded the movable limit angle [Phi ₁ (
S11 in NO), the process proceeds to step (S5), executes the step (S6) since by changing the [Phi _1.

As described above, the illumination angle Φ1 is changed while continuously capturing images with the area camera 201, and the entire inspection region 12 or a partial region shown in FIG. 5 is imaged. Next, a local fluctuation portion of the image luminance in the region is detected. Among them, the one that does not change depending on the illumination angle is extracted. The defect extracted here is a defect candidate but is highly likely to be a mura defect. For the defect candidate whose position is identified in this way, the illumination angle Φ ₁ ′ that maximizes the image brightness difference from the normal part is obtained. This illumination angle is reflected in the imaging system by the line sensor camera. In order to image a mura defect by setting the illumination angle Φ ₂ of the line sensor camera illumination 311 to the same angle as Φ ₁ (in this case, the obtained illumination angle Φ ₁ ′ is indicated) by the arc rail 313 shown in FIG. The optimum illumination angle condition is set for the imaging system using the line sensor camera. Thereafter, the line sensor camera 211 is used to acquire an image of the region to be inspected. By processing the image data by the processing unit 70, the mura defect is inspected. In this way, the defect portion extracted by the area camera is further inspected by the line sensor camera with the illumination angle Φ ₂ set to the same angle as Φ ₁ (in this case, the determined illumination angle Φ ₁ ′). As a result, it is possible to perform a highly accurate inspection in a short time as compared with the case where the inspection area is inspected while changing the illumination angle using the line sensor camera.

(Application example 2)
Application example 2 will be described. After the inspection is completed, it is possible to confirm in a short time whether the spot detected as a mura defect is an actual mura defect or a reflection by an area camera. It is only necessary to change the illumination angle around the illumination angle condition Φ used for the inspection and confirm whether or not the portion having the image luminance fluctuation locally moves. At this time, the line sensor camera needs to repeat the imaging operation by changing the illumination condition and moving the stage. On the other hand, when using the image of the area sensor camera, it is not necessary to move the stage, so that the confirmation work is completed in a short time.

  In the above description, the illumination angle is changed. However, in the illumination condition setting by the area camera, images are acquired at regular time intervals while changing the wavelength of illumination light by a certain amount, which is optimal for mura defect inspection. It is also possible to search for illumination wavelength conditions. It is also possible to search for an optimal illumination wavelength condition for mura defect inspection by acquiring images at regular time intervals while changing the installation angle Θ of the object to be inspected by a certain amount.

  Thus, according to the periodic pattern inspection apparatus and inspection method of the present invention, it is possible to efficiently discriminate between reflections and unevenness defects from the detected defects. It is possible to prevent erroneous determination of defects due to reflection, and it is possible to shorten the inspection time even when inspecting a large area inspection object.

DESCRIPTION OF SYMBOLS 10 ... Test object 11 ... Transparent substrate 12 ... Light-shielding film part 13 of inspection object ... Light-shielding film part 14 which is not inspection object ... Opening 40 ... Incident light 41 ... Diffraction light 42 from light-shielding film layer ... Diffraction including reflection Light 50 ... Inspection device 51 ... Transparent substrate holding jig 52 ... Conveying device 55 ... Conveying device operation control device 61 ... Light shielding film layer 63 imaged under arbitrary illumination conditions ... Uneven defect 64 ... Reflection example 66 ... Reflection An example of a ray trajectory that causes an image 70 ... a control unit 71 ... an image processing unit 72 ... an information display unit 73 ... an information input unit 200 ... an imaging unit 201 ... an area camera 202 ... an area camera imaging lens 206 ... an area camera control device 211 ... Line sensor camera 202 ... line sensor camera imaging lens 206 ... line sensor camera control device 300 ... illumination unit 301 ... area camera light projecting unit 303 ... area camera Lighting apparatus for arc rails 305 ... area camera (first illumination device)
306 ... Area camera light guide 311 ... Line sensor camera light projection unit 313 ... Line sensor camera arc rail 315 ... Line sensor camera illumination device (second illumination device)
316 ... Light guide for line sensor camera

Claims (8)

An apparatus for inspecting a substrate having a periodic pattern formed on a substrate surface using diffracted light generated by the periodic pattern,
Transport means for placing and transporting the substrate;
A first illumination means and a second illumination means for illuminating the substrate;
First illumination angle changing means for changing the illumination angle of the first illumination means;
Second illumination angle changing means for changing the illumination angle of the second illumination means;
First imaging means for imaging the substrate illuminated by the first illumination means;
Second imaging means for imaging the substrate illuminated by the second illumination means;
An image processing unit for processing images obtained by the first imaging unit and the second imaging unit;
A controller that controls the transport unit, the first and second illumination units, the first and second illumination angle changing units, and the first and second imaging units; Inspection apparatus characterized by that.   The inspection apparatus according to claim 1, wherein the first illuminating unit and the second illuminating unit change an illumination angle in a plane perpendicular to a substrate to be inspected and a horizontal plane.   The inspection apparatus according to claim 1, wherein the first imaging unit is an area camera, and the second imaging unit is a line sensor camera.   The image processing unit images a defect candidate extracted by processing an image captured by the first imaging unit by the second imaging unit, and extracts a true defect from the captured image. The inspection apparatus according to claim 1. A method for inspecting a substrate having a periodic pattern formed on a substrate surface using diffracted light generated by the periodic pattern,
A transport process for placing and transporting the substrate;
A first illumination process and a second illumination process for illuminating the substrate;
A first illumination angle changing step of changing an illumination angle of the first illumination step;
A second illumination angle changing step of changing the illumination angle of the second illumination step;
A first imaging step of imaging the substrate illuminated by the first illumination step;
A second imaging step of imaging the substrate illuminated by the second illumination step;
An image processing step for processing images obtained by the first imaging step and the second imaging step;
Using the control step for controlling the transport step, the first and second illumination steps, the first and second illumination angle changing steps, the first imaging step and the second imaging step. An inspection method for inspecting a substrate on which a periodic pattern is formed.   6. The inspection method according to claim 5, wherein in the first illumination step and the second illumination step, the illumination angle is changed in a plane perpendicular to the substrate to be inspected and in a horizontal plane.   6. The inspection method according to claim 5, wherein an area camera is used for the first imaging step, and a line sensor camera is used for the second imaging step.   Using the image processing step, the defect candidates extracted by processing the image picked up by the first image pickup step are picked up by the second image pickup step to extract a true defect from the picked-up image. The inspection method according to claim 5.

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