JP2008039444A - Method and apparatus for inspecting foreign matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect the foreign matter with a size of 100 μm on the surface of a large-sized substrate in a foreign matter inspection method, and a foreign matter inspection device. <P>SOLUTION: The surface of a substrate 1 to be measured is irradiated with the laser beam 2 from a light source so that the laser beam 2 may irradiate the substrate 1 from the front end to the rear end in the optical axis direction of the laser beam 2 an optical axis is inclined from the direction parallel to the surface of the substrate 1 and the scattering light component contained in the reflected light 3 from the substrate 1 is imaged by an image sensor 7 while relatively moving the laser beam 2 and the substrate 1 and the foreign matter is detected from the variation of the two-dimensional light quantity pattern in the acquired image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a foreign matter inspection method and a foreign matter inspection apparatus. For example, in a manufacturing process of a large liquid crystal display device or the like, when a thin film is applied or formed on a flat substrate, foreign matter existing on the substrate surface is inlined. The present invention relates to a foreign substance inspection method and a foreign substance inspection apparatus characterized by a configuration for inspecting with high accuracy.

  In the manufacturing process of a semiconductor device or a liquid crystal display device, a number of thin film forming processes such as a photoresist coating process or various thin film forming processes are required. In such a thin film forming process, If foreign matter exists on the surface of the substrate, it may cause a failure in the coating apparatus or cause a defect in the product after film formation. Therefore, it is necessary to inspect for the presence of foreign matter.

  Conventionally, as a method for inspecting the presence or absence of foreign substances on the surface of such a substrate, for example, a linear light source such as a fluorescent lamp is irradiated on the substrate, the reflected light and irregularly reflected light are acquired by a television camera, and the acquired image A method for inspecting surface defects such as foreign matters and scratches on a substrate surface by binarizing the light intensity of each pixel with a certain reference value and obtaining the binarized diffused reflected light area, that is, the light intensity of the irregularly reflected light Has been proposed (see, for example, Patent Document 1).

  Alternatively, the laser beam is irradiated in parallel to the surface of the substrate, the reflected light reflected by the laser reflector provided on the opposite side of the substrate is detected by a photodetector, and the refraction or absorption of the laser beam by a foreign substance or the like is detected. It has also been proposed to detect a foreign object by measuring the degree of attenuation of the intensity of reflected light due to (see, for example, Patent Document 2).

  Furthermore, the laser beam is irradiated while being scanned laterally in parallel to the surface of the substrate, detected by a photodetector provided on the opposite side of the substrate, and attenuated by refraction or absorption of the laser beam due to foreign matter etc. It has also been proposed to detect foreign matter by measuring the degree (see, for example, Patent Document 3).

In addition, in this proposal, the substrate is rotated 90 ° to perform the inspection twice, and when a foreign object is detected, air is blown to the detected portion with an air gun to remove the foreign object, and then re-inspection is performed. It has also been proposed to do.
Japanese Patent Laid-Open No. 61-283857 JP 2006-105976 A JP 2000-230910 A

  However, in each of the above proposals, there is a problem that it is difficult to detect foreign matter adhering to the surface of a large substrate used in the current generation or next generation large flat panel display. This situation will be described with reference to FIG. To do.

See FIG.
FIG. 14 is a conceptual explanatory diagram of the spatial distribution of the received light intensity. When the foreign object is close to the photodetector, the shadow 62 of the foreign object can be confirmed in the received light source light image 61. Although it can be detected as a decrease in intensity, when the foreign object is far from the photodetector, the diffracted light wraps around the shadowed portion, so the shadow 63 of the foreign object is almost confirmed in the received light source light image 61. The reduction rate of the received light intensity becomes very small.

  Such a tendency becomes more prominent as the distance between the laser light source and the light detector is longer, that is, as the substrate becomes larger. In particular, the current is required to be 100 μm in the process of applying a resist on a glass substrate. There is a problem that it is not possible to reliably detect minute foreign matters of size.

  For example, if there is a 100 μm size foreign material on the surface of the substrate, the distance between the surface of the substrate and the nozzle of the coating apparatus is set to about 100 μm, and the nozzle and the foreign material may come into contact with each other and the nozzle may be damaged. .

  Further, in the above Patent Document 2 or Patent Document 3, the principle is that the decrease in the amount of light when the laser beam passes through the foreign object is detected by comparing the amount of light before and after the passage. When there is a foreign substance of 100 μm at a position 2 to 3 m away from the light detector, there is a problem that the reduction rate of the light amount is very small and the foreign substance cannot be detected reliably.

  In this case, if the reference value for binarization is reduced in order to detect the foreign matter, the influence of noise increases, and it is determined that the foreign matter is detected even when no foreign matter is present, and the throughput is increased. The problem of a significant drop occurs.

  Furthermore, in the above-mentioned Patent Document 1, the principle is to directly detect the amount of irregularly reflected light to detect foreign matter, but in this case, when the substrate size increases, the full width cannot be accommodated in the camera's field of view. Therefore, there is a problem that the configuration of the apparatus becomes very complicated, such as arranging a large number of cameras in parallel.

  Accordingly, an object of the present invention is to accurately detect a foreign matter having a size of 100 μm on the surface of a large substrate.

FIG. 1 is an explanatory diagram of the principle configuration of the present invention. Here, means for solving the problems in the present invention will be described with reference to FIG.
In addition, the code | symbol 5 in a figure is direct light.
1 (1) In order to achieve the above object, according to the present invention, in the foreign matter inspection method, the laser beam 2 from the light source is laser-emitted with respect to the surface of the substrate 1 to be measured in the optical axis direction of the laser beam 2. Irradiation is performed with the optical axis inclined from a direction parallel to the surface of the substrate 1 so that the beam 2 irradiates from the front end to the rear end of the substrate 1, and the laser beam 2 and the substrate 1 are moved relative to each other from the substrate 1. The reflected light 4 is picked up by an image sensor 7 and the foreign matter 3 is detected from the fluctuation of the two-dimensional light quantity pattern in the acquired image.

  Although the reduction rate of the amount of light due to the foreign material 3 is very small, as a result of intensive studies by the present inventors, it is possible to detect the fluctuation of the two-dimensional light amount pattern in the acquired image even with the large substrate 1 with sufficient accuracy. Since it has been confirmed that this can be done, the presence or absence of the foreign matter 3 can be accurately determined by detecting the fluctuation of the two-dimensional light quantity pattern in the acquired image.

  In this case, the direct reflected light component of the reflected light 4 from the substrate 1 not only has a small amount of foreign matter information but also has a large overall light quantity, so that the detection dynamic range is narrowed. The detection dynamic range can be widened by using a scattered light component caused by the contained foreign matter 3.

  (2) In addition, the present invention is characterized in that, in the above (1), the laser beam 2 is a vertically long laser beam 2 whose vertical axis with respect to the surface of the substrate 1 of the laser beam 2 is larger than the horizontal axis.

  As described above, when the laser beam 2 is applied from the front end to the rear end of the substrate 1 by using the vertically long laser beam 2, the total light amount can be reduced, thereby increasing the fluctuation amount with respect to the total light amount, The detection performance for the small foreign matter 3 can be improved.

  (3) In the present invention, in the above (1) or (2), the step of detecting the foreign material 3 from the fluctuation of the two-dimensional light quantity pattern in the acquired image is based on the adjacent images before and after the acquired image. It consists of a step of taking a difference in light intensity for each pixel to form a difference image, a step of forming a maximum value image for each pixel from adjacent difference images, and a step of counting pixels having a predetermined value or more from the maximum value image. It is characterized by.

In this way, in the foreign matter determination step, the conventional moving body detection algorithm is used, and the step of counting pixels having a predetermined value or more from the maximum value image is added to accurately determine the foreign matter 3 on the substrate surface. be able to.
It should be noted that the step of counting pixels having a value greater than or equal to a predetermined value from the maximum value image, the step of creating a binarized image of the maximum value image, and the step of counting white point pixels from the binarized processed image You may comprise as these 2 processes.

  (4) Further, in the above (3), the present invention provides a specific pixel as a target for each pixel constituting the maximum value image in the step of counting pixels having a predetermined value or more from the maximum value image. And a step of setting a minimum value of nine pixels within a range of 3 × 3 in combination with eight adjacent pixels to a value of a specific pixel.

  In this way, noise can be removed by using the process of setting the minimum value of nine pixels within the 3 × 3 range as the value of a specific pixel, that is, the 3 × 3 minimum density extraction process. become.

  (5) Further, the present invention is characterized in that in any of the above (1) to (4), 80% or more of the direct reflected light 4 from the substrate 1 is shielded and imaged. .

  As described above, the amount of foreign matter contained in the directly reflected light component of the reflected light 4 from the substrate 1 is not only small, but the detection dynamic range is narrowed because the total light amount is large, so that the reflection from the substrate 1 is reduced. It is desirable to shield 80% or more, more preferably 95% or more, of the direct reflected light of the light 4, thereby increasing the relative intensity of the scattered light component caused by the foreign material 3, thereby widening the detection dynamic range. can do.

  (6) Further, according to the present invention, in any one of the above (1) to (5), after the foreign matter inspection is performed on the substrate 1 from the first direction, the substrate 1 is in the second direction substantially orthogonal to the first direction. It is characterized by inspecting foreign matter from

  Since scattered light is detected from the end of the substrate 1 parallel to the optical axis of the laser beam 2 at the start of measurement and at the end of measurement, regardless of the presence of the foreign matter 3, the foreign matter is inspected from the first direction. The influence of the scattered light from the end of the substrate 1 can be eliminated by inspecting the foreign substance from the second direction substantially orthogonal to the first direction.

  (7) Further, in the foreign matter inspection apparatus according to the present invention, the laser beam 2 is irradiated from the front end to the rear end of the substrate 1 in the optical axis direction of the laser beam 2 on the surface of the substrate 1 to be measured. More than 80% of the directly reflected light among the light source arranged with the optical axis inclined from the direction parallel to the surface of the substrate 1, the imaging means for measuring the reflected light 4 from the substrate 1, and the reflected light 4 from the substrate 1 It has a foreign substance measuring means comprising a light shielding means 6 for shielding, and a foreign substance determining means 8 for judging the foreign substance 3 from the fluctuation of the two-dimensional light quantity pattern in the image acquired by the imaging means, and the substrate 1 and the foreign substance measuring means are relatively It is characterized in that it is provided with a moving means for moving it.

  By adopting such an apparatus configuration, it is possible to accurately determine the presence or absence of the foreign matter 3 on the surface of the large substrate 1 using the foreign matter inspection method described above with high throughput.

  According to the present invention, it is possible to accurately determine the presence or absence of a 100 μm size foreign substance on the surface of a large substrate used for a large flat panel display or the like, which has been difficult with the conventional method of attenuation of light amount. The destruction of the manufacturing apparatus can be avoided, and the cost and the display quality of a large flat panel display can be reduced.

Here, with reference to FIG. 2 thru | or FIG. 5, the foreign material inspection method of embodiment of this invention is demonstrated.
FIG. 2 is a conceptual configuration diagram of the foreign matter inspection apparatus used in the embodiment of the present invention, and a substrate to be measured 11 such as a glass substrate to be measured, and a substrate to be measured 11 are horizontally placed and held. A substrate mounting table 12, a stage 13 for horizontally mounting and holding the substrate mounting table 12, a rail 14 for moving the stage 13 in a uniaxial direction, a laser light source 15 for irradiating a laser beam 16 to the substrate 11 to be measured, and an area sensor type Camera 17, a neutral density filter 18 disposed immediately before camera 17, a cylindrical lens 19 provided with a light-shielding film 20, and an image processing device 21 that determines foreign matter from an acquired image of camera 17.

  In this case, the laser beam 16 is a vertically long laser beam whose vertical axis is longer than the horizontal axis, and the optical axis is the surface of the substrate 11 to be measured so that the laser beam 16 simultaneously irradiates from the front end to the rear end of the substrate 11 to be measured. The laser beam 16 is incident on the surface of the substrate 11 to be measured at a very shallow angle.

This is because it is advantageous that the laser beam diameter is large in order for the laser beam 16 to irradiate from the front end to the rear end of the substrate 11 to be measured at the same time. However, as the laser beam diameter increases, the overall light quantity increases and the detection performance is improved. descend.
Therefore, by using the vertically long laser beam 16, the entire light amount is reduced and the fluctuation amount with respect to the entire light amount is increased to improve the detection performance.

Further, the light shielding film 20 removes 80% or more of the directly reflected light component of the reflected light 22 of the laser beam 16.
This is because not only the amount of foreign matter contained in the directly reflected light component of the reflected light 22 from the substrate to be measured 11 is small, but also the detection dynamic range is narrowed because the total amount of light is large. This is because the relative intensity of the scattered light component having a large amount of foreign matter information is increased and the detection dynamic range is widened by shielding 80% or more of the directly reflected light of the reflected light 22.

See Figure 3
FIG. 3 is a conceptual explanatory diagram of the spatial distribution of reflected light intensity. As shown in the left diagram, when a foreign object is close to the camera, a shadow 24 of the foreign object is confirmed in the directly reflected light 23 that has been imaged. However, when the foreign object is far from the camera, the shadow 24 of the foreign object can hardly be confirmed in the direct reflected light 23.

  However, in any case, the scattered light 25 detected in the vicinity of the direct reflected light 23 is sufficiently detected. Therefore, the two-dimensional light quantity pattern of the scattered light 25 is measured and foreign matter is detected by the variation. is there.

  In addition, by using the cylindrical lens 19, diffracted / scattered light due to the passage of a foreign substance is guided to the imaging range of the camera as much as possible. Since the cylindrical lens 19 is arranged so as to converge the laser beam 16 from the laser light source 15 in a linear manner, the radiated light that does not contain foreign substance information slightly contained in the laser beam 16 is converged in a linear manner. Therefore, the area affected by the emitted light is limited.

The stage 13 is continuously moved by a motor (not shown), and images are intermittently captured by the camera 17.
The neutral density filter 18 is composed of two polarizing filters and is provided to adjust the amount of light reaching the camera 17.

Next, an image processing method by the image processing apparatus 21 will be described with reference to FIG.
See Figure 4
FIG. 4 is a conceptual explanatory diagram of the image processing method. Here, for the sake of simplicity, the lightness and darkness are reversed. First,
(A) Of the captured images captured in a stepwise manner, a difference image is created by taking a difference in light intensity for each image between adjacent images.
In this case, a difference light image 32 of + (difference is a positive value) and a difference light image 33 of-(a difference is a negative value) are obtained by taking the difference between the reflected light images 31 in the captured image. The minus difference light image 33 is replaced with 0 light quantity.

Then
(B) A maximum value image is created by calculating a logical sum of adjacent difference images.
The process of (a) inter-frame difference + (b) logical sum is a known technique as a moving object detection algorithm (if necessary, Hideyuki Tamura, Computer Image Processing, p. 242, 2002, Ohmsha Published).

Then
(C) The maximum image is binarized to create a binarized image.
When creating this binarized image, the range of 3 pixels × 3 pixels including the adjacent pixel 35 centered on the specific pixel 34 with respect to the specific pixel 34 subject to binarization processing The minimum value of the light intensity of the total nine pixels 34 and 35 is obtained, and the obtained minimum value is set as the light intensity of the specific pixel 34.
Note that the threshold value in binarization is set to a value that reliably determines that the foreign material sample is a foreign material through an experiment using the reference foreign material sample.

Finally,
(D) The number of white spots in the binarized image, that is, the number of pixels determined to be “1” in binarization is counted to determine the presence or absence of foreign matter.
In this case as well, the threshold value for determining the number of white points as a foreign object is set to a value that reliably determines that the foreign object sample is a foreign object by an experiment using a reference foreign object sample.

Next, with reference to FIG. 5, an additional foreign matter inspection process will be described.
See Figure 5
FIG. 5 is an explanatory diagram of the additional foreign matter inspection process of the present invention. First, the foreign substrate inspection is performed by moving the substrate to be measured 11 in one direction as described above, and then the substrate to be measured 11 is rotated by 90 °. The same foreign matter inspection is performed again.
For example, this can be achieved by providing a 90 ° rotation mechanism on the substrate mounting table 12 described above.

As will be described in detail later along with the measurement results, light scattering occurs at both ends 11 _a and 11 _b of the substrate 11 to be measured parallel to the laser beam 16, and the presence or absence of foreign matter in this region is determined. I can't do that.

However, by rotating the substrate to be measured 11 by 90 ° and performing the foreign substance inspection again, the foreign substances can be inspected at the end portions 11 _a and 11 _b where the presence or absence of the foreign substance could not be determined in the previous measurement.
In this case, although light scattering occurs at the other end portions 11 _c and 11 _d of the other substrate 11 to be measured, the presence or absence of foreign matter cannot be determined. There is no problem because the presence or absence is confirmed.

Based on the above, Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 6 is an explanatory diagram of the apparatus configuration of the foreign matter inspection process of the first embodiment of the present invention. The distance between the laser light source 15 and the camera 17 is 2500 mm, and the end surface on the light source side of the measured substrate 11 made of a glass substrate The distance between the cylindrical lens 19 and the cylindrical lens 19 is 2000 mm (= 2 m), the distance between the cylindrical lens 19 and the light receiving surface of the camera 17 is 250 mm, and the distance between the laser light source 15 and the light source side end surface of the substrate 11 to be measured is 250 mm.

  As the laser light source 15 in this case, a red semiconductor laser having a wavelength of, for example, 635 nm is used. The laser beam 16 is formed of an elliptical parallel beam having a major axis of 6 mm and a minor axis of 3 mm. Irradiate so that

  The camera 17 uses, for example, a 1/4 inch CMOS area sensor having 350,000 pixels (640 × 480 pixels + peripheral pixels) without a lens, and here, four pixels are combined to form 320 × 240. Imaging as a pixel.

  In this case, a glass substrate having a thickness of 0.7 mm and a width of 650 mm in the optical axis direction of the laser beam 16 is used as the substrate 11 to be measured, and the stage 13 is moved at a moving speed of 3 mm / second, for example. For example, imaging is performed stepwise at a frequency of 8 frames / second.

See FIG.
FIG. 7 is an explanatory diagram of the configuration of the cylindrical lens. A light shielding film 20 made of a black light shielding film having a width of 4.5 mm and a length of 12 mm is provided on the convex surface side of the cylindrical lens 19 having F = 250 mm. The light shielding film 20 shields 95% or more of the direct reflected light 23 from the substrate 11 to be measured.

  In this case, since the reflected light and the direct light 26 not irradiated on the substrate 11 to be measured are simultaneously received, they are shielded by 95% or more. However, since the direct light 26 does not include foreign substance information, it is accompanied by diffracted / scattered light. Even if the remainder of the direct light 26 is received, the influence can be eliminated by converging linearly with the cylindrical lens.

See FIG.
FIG. 8 is an explanatory diagram of the arrangement state of the foreign material sample in Example 1 of the present invention. Under the condition A shown in the left diagram, Ref ₁ and Ref ₂ having a size of 500 μm are formed at the light source side end of the substrate 11 to be measured. Are arranged at intervals of 11 mm, and a 100 μm-sized sample to be measured is arranged at a position 5 mm from Ref ₂ .

On the other hand, under the condition B shown in the right figure, 500 μm-sized Ref ₁ and Ref ₂ are arranged at an interval of 11 mm at the light source side end of the substrate 11 to be measured, and a 100 μm-sized sample to be measured is set to Ref _1. And 5 mm outside.

See FIG.
FIG. 9 is an explanatory diagram of the acquired captured image. Here, a single captured image is shown in a replicated manner, but here too, the light and dark are shown inverted for the sake of simplicity.
As shown in the figure, the remaining portion of the direct reflected light 23 in the laser beam 16 and the convergent light image 41 due to the radiated light component are converged linearly at the center of the image, and diffraction / scattering by foreign matter on the periphery thereof. The light component 42 is imaged.

In this case, since the length of the horizontal axis (short axis) of the laser beam 16 is 3 mm, the diffracted / scattered light component 42 is detected while the laser beam 16 traverses a 100 μm foreign matter.
In this case, the moving speed of the stage is 3 mm / second, and one foreign object is imaged continuously for 1 second. However, since the imaging frequency is 8 images / second, the image is continuously displayed on 8 images. A foreign object will be detected.

  Note that the actual captured image is a very bright image even when there is no foreign object, and it is virtually impossible to visually observe the influence of the foreign object on the captured image, and the difference image, the maximum value image, and 2 Since it is very difficult to illustrate a binarized image as a patent drawing, illustration is omitted, but a binarized image is created by performing the image processing shown in FIG. 4 on an actually captured image. To do.

  In this binarization processing, for example, with respect to 256 gradations, a pixel having a gradation of 4 or more in each pixel is “1”, that is, a white point, and pixels less than 4 are “0”, that is, , Black spots are counted, and the number of white spots in the binarized image is counted.

See FIG.
FIG. 10 is an explanatory diagram of the result of the foreign matter inspection in Example 1 of the present invention. In the case of the condition A indicated by a broken line and the condition B indicated by a solid line, about 30 μm are separated from each other at a position where continuous images are separated from each other. Peaks due to size Ref ₁ and Ref ₂ were detected.
Since one image corresponds to 0.375 mm (= 3 mm / 8 sheets), an interval of 11 mm corresponds to 29.3 images, that is, about 30 images.

In the case of Condition A, a peak with a frequency, that is, the number of counted white dots exceeding 3000, is detected at a position about 13 images away from Ref ₁ , and this corresponds to a sample of 100 μm size.

On the other hand, in the case of condition B, a peak where the frequency, that is, the number of counted white spots exceeds 1000, is detected at a rear position about 13 images away from Ref ₁ , and this corresponds to a sample of 100 μm size. .

  In either case, almost no white point was detected from the area where Ref and the sample were not arranged. Therefore, by setting the frequency threshold to 1000, the distance between the foreign object and the cylindrical lens 19 is 2 m. Even in this case, it was confirmed that foreign matters having a size of 100 μm or more can be accurately detected.

As shown in FIG. 10, light scattering occurs at the side end portion of the measurement target substrate 11 at the start of detection, and the scattering component is detected, but the scattering component at the side end portion of the measurement target substrate 11 is detected. As shown in FIG. 5 described above, the influence can be eliminated by rotating the substrate under measurement 11 by 90 ° and reinspecting it.
As described above, after the foreign matter inspection is performed in real time, the measurement target substrate 11 in which no foreign matter is detected is carried into the coating apparatus to apply the resist.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, the foreign matter is disposed near the light source, but in the second embodiment, the foreign matter is disposed on the side closer to the detection system.
11. FIG. 11 is an explanatory diagram of the apparatus configuration of the foreign matter inspection process of the second embodiment of the present invention. The distance between the laser light source 15 and the camera 17 is 1500 mm, and the end surface on the light source side of the measured substrate 11 made of a glass substrate. The distance between the cylindrical lens 19 and the cylindrical lens 19 is 1000 mm (= 1 m), the distance between the cylindrical lens 19 and the light receiving surface of the camera 17 is 250 mm, and the distance between the laser light source 15 and the light source side end surface of the substrate 11 to be measured is 250 mm.
The other measurement system configuration conditions and image processing conditions are exactly the same as in the first embodiment.

See FIG.
FIG. 12 is an explanatory diagram of the arrangement state of the foreign material sample in Example 2 of the present invention. Under the condition A shown in the left diagram, a 500 μm size Ref and a measurement target are measured at the camera side end of the substrate 11 to be measured. Samples with a size of 100 μm are arranged at intervals of 7 mm.

  On the other hand, under the condition B shown in the right figure, only the Ref of 500 μm size is arranged at the same position as the condition A at the camera side end of the substrate to be measured 11.

See FIG.
FIG. 13 is an explanatory diagram of the result of the foreign substance inspection in Example 2 of the present invention. In the case of the condition A indicated by the broken line and the condition B indicated by the solid line, a peak due to Ref having a 500 μm size is detected at substantially the same position. It was.

  In the case of condition A, a peak with a frequency, that is, the number of counted white spots exceeding 1000, is detected at a position about 20 images away from Ref, and this corresponds to a sample of 100 μm size.

In either case, almost no white point was detected from the area where Ref and the sample were not arranged. In this case as well, by setting the frequency threshold to 1000, the distance between the foreign object and the cylindrical lens 19 can be increased. It was confirmed that a foreign substance having a size of 100 μm or more can be accurately detected even in the case of 1 m.
In this case, since the scattered light is reduced because the distance to the detection system is short, the number of signals, that is, white spots, is reduced.

  In this case as well, light scattering occurs at the side edge of the measured substrate 11 at the start of detection, and the scattered component is detected. The influence of the scattered component at the side edge of the measured substrate 11 is As shown in FIG. 5 described above, it can be eliminated by rotating the substrate to be measured 11 by 90 ° and reinspecting it.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various modifications can be made.
For example, the size of the glass substrate, the distance between the light source and the substrate, and the distance between the substrate and the cylindrical lens in each of the above embodiments are arbitrary, and are appropriately changed according to the size of the glass substrate to be measured.

Further, depending on the configuration, the cylindrical lens may be omitted if the diffracted / scattered light can be accommodated in the area sensor without passing through the cylindrical lens.
On the other hand, if most of the diffracted / scattered light does not fit in the area sensor with the cylindrical lens alone, a single spherical lens or a combination optical system of spherical lenses may be added after the cylindrical lens.

  In each of the above embodiments, a CMOS type area sensor is used as a camera. However, the present invention is not limited to a CMOS type area sensor, and a CCD type or MOS type area sensor may be used. .

  Although it is desirable to use a monochrome camera as the camera, it is also possible to use a color camera that is easily available. In this case, since the color information is irrelevant to detection, the captured color image is converted to grayscale. Then, a difference image may be created.

In the above embodiment, a red laser having a wavelength of 635 nm which is inexpensive and easily available is used as the laser light source. However, it goes without saying that lasers of other wavelengths may be used, and in principle, the shorter the wavelength, the shorter the wavelength. Since scattering by a minute object becomes remarkable, a short wavelength laser may be used.
However, when a short wavelength is used, attention should be paid because the measurement object may be sensitive to blue to ultraviolet light.

  Alternatively, an infrared laser may be used as a laser light source, and scattering is reduced at a long wavelength, which is disadvantageous for detection, but can be used without problems up to a wavelength of 1000 nm by increasing the infrared sensitivity of the camera. .

  In the description of each of the above embodiments, the stage is continuously moved. However, the stage may be moved step by step so as to be synchronized with imaging by the camera.

  Further, in the above-described embodiment, the description is made as the foreign substance inspection process on the surface of the glass substrate in the liquid crystal panel, but the invention is not limited to the foreign substance inspection, but is also applied to the inspection of the irregularities on the glass surface. The convex portion having a height of 100 μm is effective because it causes nozzle destruction.

  Further, in each of the above embodiments, the foreign matter inspection before the resist coating step is performed. However, the present invention is not limited to the foreign matter inspection before the resist coating step, but the foreign matter before the insulating film or conductive film forming step. This also applies to inspection, and if foreign matter is present on the substrate surface before film formation, it may cause pinholes and cracks, which in turn affects the reliability of the product.

  In the above embodiment, the neutral density filter is provided on the camera side, but it may be provided on the light source side.

  In each of the above embodiments, the description is made for the purpose of detecting a foreign matter having a size of 100 μm or more. However, the present invention is also applied to the detection of a foreign matter having a size of 100 μm or less. Therefore, it is possible to estimate the size of the foreign substance from the measured frequency by obtaining the frequency of a plurality of foreign substances whose sizes are known.

  In each of the above embodiments, the substrate to be measured is moved by the stage, but the substrate to be measured is fixed, and the measurement system including the laser light source / cylindrical lens / camera is moved to acquire an image. It may be good.

  Further, in each of the above-described embodiments, the treatment when a foreign object is detected is not mentioned, but when a foreign object is detected, scanning and detection of the substrate are performed as shown in FIG. 10 or FIG. By synchronizing, it is possible to accurately grasp the position of the foreign matter in the scanning direction, so try to remove the foreign matter by injecting gas with an air gun along the position in the scanning direction where the foreign matter was detected, and then reinspect. May be.

  Or when a foreign material is detected, it may be considered as a defective product as it is, and the thin film already laminated on the glass substrate is removed to reuse the glass substrate.

  As an application example of the present invention, a foreign substance inspection on the surface of a glass substrate in a manufacturing process of a large-sized liquid crystal panel is typical, but is not limited to a large-sized liquid crystal panel, and liquid crystal panels of various sizes or organic EL The present invention is also applied to a foreign matter inspection process before a film forming process or a resist coating process in an electronic device such as a plasma display panel or a semiconductor device.

It is explanatory drawing of the fundamental structure of this invention. It is a notional block diagram of the foreign material inspection apparatus used for embodiment of this invention. It is a conceptual explanatory drawing of the spatial distribution of reflected light intensity. It is a conceptual explanatory view of an image processing method. It is explanatory drawing of the additional foreign material inspection process of this invention. It is explanatory drawing of the apparatus structure of the foreign material inspection process of Example 1 of this invention. FIG. 6 is a configuration explanatory diagram of a cylindrical lens. It is explanatory drawing of the arrangement | positioning condition of the foreign material sample in Example 1 of this invention. It is explanatory drawing of the acquired captured image. It is explanatory drawing of the result of the foreign material test | inspection in Example 1 of this invention. It is explanatory drawing of the apparatus structure of the foreign material inspection process of Example 2 of this invention. It is explanatory drawing of the arrangement | positioning condition of the foreign material sample in Example 2 of this invention. It is explanatory drawing of the result of the foreign material test | inspection in Example 2 of this invention. It is a conceptual explanatory drawing of the spatial distribution of received light intensity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Laser beam 3 Foreign object 4 Reflected light 5 Direct light 6 Light shielding means 7 Image sensor 8 Foreign object determination means 11 Substrate to be measured 11 _{a to} 11 _d End 12 Substrate mounting stage 13 Stage 14 Rail 15 Laser light source 16 Laser beam 17 Camera 18 Neutral filter 19 Cylindrical lens 20 Light-shielding film 21 Image processing device 22 Reflected light 23 Direct reflected light 24 Foreign object shadow 25 Scattered light 26 Direct light 31 Reflected light image 32 Differential light image 33 − Differential light image 34 Specific Pixel 35 Adjacent pixel 41 Convergent light image 42 Diffracted / scattered light component 61 Light source light image 62 Foreign object shadow 63 Foreign object shadow

Claims (7)

The optical axis is parallel to the surface of the substrate so that the laser beam from the light source irradiates the surface of the substrate to be measured in the optical axis direction of the laser beam from the front end to the rear end of the substrate. Irradiating at an angle, irradiating the laser beam and the substrate relative to each other, capturing reflected light from the substrate with an image sensor, and detecting foreign matter from fluctuations in the two-dimensional light quantity pattern in the acquired image Foreign matter inspection method characterized by 2. The foreign matter inspection method according to claim 1, wherein the laser beam is a vertically long laser beam having a vertical axis larger than a horizontal axis with respect to the surface of the substrate. The step of detecting a foreign substance from the fluctuation of the two-dimensional light amount pattern in the acquired image is adjacent to the step of taking a difference in light intensity for each pixel from adjacent images before and after the acquired image and forming a difference image. The foreign matter inspection method according to claim 1, comprising: forming a maximum value image for each image from the difference image; and counting pixels having a predetermined value or more from the maximum value image. In the step of counting pixels having a value greater than or equal to a predetermined value from the maximum value image, each pixel constituting the maximum value image is combined with 8 pixels adjacent to a specific target pixel, and 3 × The foreign matter inspection method according to claim 3, further comprising a step of setting a minimum value of nine pixels within the range of 3 to a value of the specific pixel. 5. The foreign matter inspection method according to claim 1, wherein 80% or more of the direct reflected light of the reflected light from the substrate is shielded and imaged. 6. The foreign substance inspection of the substrate from a first direction, and then the foreign substance inspection of the substrate from a second direction substantially orthogonal to the first direction. 6. Foreign substance inspection method. The optical axis is inclined from the direction parallel to the surface of the substrate so that the laser beam irradiates from the front end to the rear end of the substrate in the optical axis direction of the laser beam with respect to the surface of the substrate to be measured. In the image acquired by the imaging means, a foreign matter measuring means comprising a light source, an imaging means for measuring the reflected light from the substrate, and a light shielding means for shielding 80% or more of the direct reflected light from the reflected light from the substrate. A foreign matter inspection apparatus comprising a foreign matter determination means for judging foreign matter from a change in a two-dimensional light quantity pattern, and a moving means for relatively moving the substrate and the foreign matter measurement means.

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