JP2010002223A - Inspection device of surface flaw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the detection precision of a flaw by reducing erroneous detection and to achieve the shortening of an inspection time and the reduction of cost at the same time. <P>SOLUTION: An illumination optical system condenses light on a focal surface to irradiate an article 100 to be inspected and scans the light condensing point on the focal surface. A light splitting part 20 splits the light obtained from the article 100 to be inspected. A first light detecting part 21A includes a condensing lens 31A, a light restricting part 32A, and a photodetector 33A and detects one light after splitting. A second light detecting part 21B includes a condensing lens 31B, a light restricting part 32B and a photodetector 33B and detects the other light after splitting. The plane conjugated with the light restricting part 32A and the plane conjugated with the light restricting part 32B are shifted mutually in an optical axis direction in the vicinity of the focal surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface defect inspection apparatus for detecting defects on the surface of an inspection object such as a substrate.

  Conventionally, as a technique for detecting a defect on the surface of an inspection object such as a substrate, a technique for capturing a dark field image of the inspection object and detecting a defect based on the dark field image is known (for example, The following patent documents 1, 2).

  Conventionally, there is also known a method for detecting a minute foreign substance attached on an object surface such as a semiconductor wafer surface using a confocal microscope (for example, Patent Document 3 below). In the method disclosed in Patent Document 3, an image obtained by two-dimensional scanning of irradiation light in the focal plane of a confocal microscope is obtained by imaging a plane having the same height on the object surface. By changing the height of the focal plane with respect to the object surface, images are acquired at the respective heights, and these images are compared to detect minute foreign matter adhering to the object surface.

Further, a method for measuring a minute step using a confocal laser scanning differential interference microscope using a waveguide as a detection system is also known (for example, Patent Document 4 below). In this minute step measuring method, a laser light source, an illumination optical system for condensing light from the laser light source to form a light spot on the test object, and a light beam from the test object are collected on a detection surface. A condensing optical system for illuminating, a detecting means for detecting a light beam condensed on the detection surface, and a scanning means for moving the spot relative to the test object, The detection means has a substrate on which a channel waveguide is formed, and the channel waveguide branches the double mode waveguide region having an incident end face on the detection surface and the two mode waveguides into two channel waveguides. A confocal laser having a waveguide branch region, and the detection means has a detection element for detecting each of the light propagating through the two branched channel waveguides, and obtains information of the test object by a detection signal Using a scanning differential interference microscope Then, from the value of the ratio between the sum signal and the difference signal of each of the detection elements, a minute uneven step on the test object is quantitatively obtained.
JP-A-4-344447 JP 7-103905 A JP-A-6-308040 Japanese Patent Laid-Open No. 6-241736

  According to the conventional method for detecting a defect based on a dark field image, the defect is detected as a minute bright spot on a dark background, so that a very high detection sensitivity can be obtained. However, with this conventional method, scratches (concaves) that are defects on the surface of the object to be inspected, and dust that can be removed by a cleaning operation and cannot be said to be defective (microscopic foreign matter (convex) attached to the surface of the object to be inspected) ) Is almost the same image, and it is difficult to distinguish them. Therefore, according to this conventional method, dust is erroneously detected as a defect, and the detection accuracy is lowered.

  In view of the above-described conventional method of detecting a minute foreign matter adhering to the surface of an object using a confocal microscope, the following surface defect inspection method can be considered. That is, using a general confocal microscope, the height of the focal plane with respect to the object to be inspected is changed, and two-dimensional scanning of the irradiation light in the focal plane is performed at each height to obtain a plurality of images. Perform three-dimensional observation of the inspection object. As a result, it is possible to distinguish between concave and convex with respect to the plane, and thus detect and detect flaws (concaves) that are defects on the surface of the inspection object by distinguishing them from minute foreign substances (convex) adhering to the surface of the inspection object. be able to. Therefore, in this case, it is possible to increase the accuracy of defect detection by reducing erroneous detection that erroneously detects dust as a scratch. However, in this case, it is necessary to change the height of the focal plane relative to the object to be examined, and to perform two-dimensional scanning of the irradiation light in the focal plane at each height to obtain a plurality of images. Therefore, the inspection time becomes long.

  In contrast, if the conventional method for measuring micro steps using a confocal laser scanning differential interference microscope using a waveguide in the detection system is used for detecting defects on the surface of the inspection object, defects on the surface of the inspection object are obtained. In addition to being able to detect and detect scratches (concaves) separately from minute foreign matter (convex) adhering to the surface of the object to be inspected, scanning with a different focal plane height is not required, so inspection time is reduced. It can be greatly shortened. However, in this case, since it is necessary to use a waveguide device for the detection system, the waveguide device is more expensive than general optical components (especially when the number of production is small, the unit price is remarkably high). Therefore, the cost increases.

  The present invention has been made in view of such circumstances, and it is possible to improve the accuracy of defect detection by reducing false detection, and it is possible to simultaneously reduce the inspection time and reduce the cost. An object is to provide an inspection device.

  In order to solve the above-described problems, a surface defect inspection apparatus according to an aspect of the present invention includes an illumination optical system that condenses light on a focal plane and irradiates an object to be inspected and scans a focal point on the focal plane. A light dividing unit that divides light obtained from the inspection object by light irradiation by the illumination optical system, and a first light detection unit that detects one light after being divided by the light dividing unit , Based on detection signals from the first and second light detection units, a second light detection unit that detects another light after being divided by the light division unit, and And a processing unit for detecting defects on the surface. The first light detection unit is disposed at a position conjugate with the first condensing lens that condenses the one light and the first plane near the focal plane, and is collected by the first condensing lens. A first light limiting unit that limits the emitted light in a pinhole shape; and a first photodetector that detects light after being limited by the first light limiting unit. The second light detection unit is disposed at a position conjugate with a second condensing lens that condenses the other one light and a second plane near the focal plane, and the second condensing lens. A second light restricting unit that restricts the light collected by the light into a pinhole, and a second photodetector that detects the light after being restricted by the second light restricting unit. The first plane and the second plane are shifted in the optical axis direction.

  According to the present invention, it is possible to provide a surface defect inspection apparatus that can reduce detection errors and increase the accuracy of defect detection, and can simultaneously reduce inspection time and cost.

  Hereinafter, a surface defect inspection apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a surface defect inspection apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, a surface defect inspection apparatus 1 according to this embodiment includes a laser light source 11, a beam expander 12 that expands laser light from the laser light source 11 to a predetermined beam diameter, a scanning unit 13, and a scanning lens. 14, a relay lens 15, a mirror 16, an objective lens 17, and an inspection object holder 18 that holds an inspection object 100 such as a glass substrate, a silicon substrate, or another substrate. A half mirror 19 is provided between the beam expander 12 and the scanning unit 13. The inspection object holder 18 holds the inspection object 100 so that the upper surface (inspection surface) of the inspection object 100 is substantially orthogonal to the optical axis L of the objective lens 17. The inspection object holder 18 can be moved in the direction of the optical axis L and in the in-plane direction orthogonal to the optical axis L as required by a moving mechanism (not shown). In the present embodiment, each of the elements 11 to 17 described above collects light on a focal plane near the upper surface of the inspection object 100 and irradiates the inspection object, and scans a condensing point on the focal plane. The illumination optical system is configured.

  The light from the laser light source 11 is expanded to a required beam diameter by the beam expander 12 and then enters the scanning unit 13 via the half mirror 19. The scanning unit 13 has two sets of movable mirrors 13a and 13b, and is in two directions orthogonal to each other (two directions corresponding to two directions orthogonal to each other in a plane orthogonal to the optical axis L of the objective lens 17). The light from the laser light source 11 is scanned. The light scanned by the scanning unit 13 is imaged in the form of a spot on the primary image plane 200 by the scanning lens 14, and then deflected through the relay lens 15 and the mirror 16, and the upper surface of the object 100 to be inspected by the objective lens 17. A spot image is formed on a nearby focal plane, and the object 100 is irradiated. The mirror 16 simply changes the direction of light and is not essential.

  The laser beam image formed on the focal plane in the vicinity of the upper surface of the inspection object 100 becomes a point image and is focused to a size determined by the NA of the objective lens, so that the inspection object 100 is almost the same size. The upper spot area is illuminated with light. Detection light (reflected light, fluorescence, scattered light, etc.) is generated almost in this spot region due to the optical characteristics of the inspection object 100 in this spot region. Detection light (reflected light, fluorescence, scattered light, etc.) generated in the spot area (irradiation area) on the inspection object 100 is collected again by the objective lens 17 and travels in the opposite direction on the same optical path as the irradiated laser light. The image is formed on the primary image plane 200 by the relay lens 15 and then reaches the half mirror 19 through the scanning lens 14 and the scanning unit 13.

  The surface defect inspection apparatus 1 according to this embodiment includes a half mirror 20 as a light splitting unit that splits light (detection light) obtained from the inspection object 100 by irradiation of light from the illumination optical system, and the half mirror 20. A first light detection unit 21A that detects one light after being divided, a second light detection unit 21B that detects another light after being divided by the half mirror 20, a first and a first light detection unit And a processing unit 22 for detecting defects on the surface of the inspection object 100 based on detection signals from the two light detection units 21A and 21B.

  The detection light reaching the half mirror 19 from the inspection object 100 is bent by the half mirror 19 and then divided into two by the half mirror 20, and one detection light is detected by the first light detection unit 21A. The other detection light is detected by the second light detection unit 21B.

  The first light detection unit 21A restricts the light collected by the first light collecting lens 31A and the first light collecting lens 31A into a pinhole shape. A first pinhole plate 32A serving as one light restricting portion, and a first photodetector 33A that detects light after being restricted by the pinhole plate 32A.

  Here, the first condensing lens 31A is disposed at a position conjugate with the first plane in the vicinity of the focal plane (the upper surface of the inspection object 100 that is the inspection surface) on which the irradiation laser light is condensed. . Hereinafter, for convenience of explanation, this first plane is referred to as a “first pinhole conjugate plane”.

  The pinhole (opening) of the first pinhole plate 32A is formed on the optical axis of the first condenser lens 31A, and the size of the pinhole is, for example, on the first pinhole plate 32A. The diameter is set to be approximately the same as the diameter of the light spot formed on the substrate. The light that has passed through the pinhole of the first pinhole plate 32A is detected by the first photodetector 33A, and the first photodetector 33A outputs an electrical signal having an intensity (level) corresponding to the amount of received light. It is like that.

  Similarly, the second light detection unit 21B has a second condensing lens 31B that condenses the other detection light after the division and the light condensed by the second condensing lens 31B in a pinhole shape. It has the 2nd pinhole board 32B as a 2nd light restriction part to restrict | limit, and the 2nd photodetector 33B which detects the light after being restrict | limited by the pinhole board 32B.

  Here, the second condenser lens 31B is arranged at a position conjugate with the second plane in the vicinity of the focal plane (the upper surface of the inspection object 100 that is the inspection surface) on which the irradiation laser light is condensed. . Hereinafter, for convenience of explanation, this second plane is referred to as a “second pinhole conjugate plane”.

  The pinhole (opening) of the second pinhole plate 32B is formed on the optical axis of the second condenser lens 31B, and the size of the pinhole is, for example, on the second pinhole plate 32B. The diameter is set to be approximately the same as the diameter of the light spot formed on the substrate. The light that has passed through the pinhole of the second pinhole plate 32B is detected by the second photodetector 33B, and the second photodetector 33B outputs an electrical signal having an intensity (level) corresponding to the amount of received light. It is like that.

  In the present embodiment, the first pinhole conjugate surface and the second pinhole conjugate surface are displaced in the direction of the optical axis L. An example of setting the heights of these pinhole conjugate surfaces in the optical axis L direction will be described with reference to FIG. The vertical direction in FIG. 2A coincides with the direction of the optical axis L. FIG. 2A schematically shows the height positions a to e in the optical axis L direction, and schematically shows an example of the surface shape of the upper surface of the inspection object 100 in a cross section including the optical axis L with a solid line. FIG. In the present embodiment, the height of the focal plane on which the irradiation laser beam is condensed is set to the height c in FIG. 2A, and the first pinhole conjugate plane of the first photodetecting portion 21A is set. The height is set to the height a in FIG. 2A above the height c, and the height of the second pinhole conjugate surface of the second photodetecting portion 21B is below the height c. The height e in FIG. 2A is set. However, the positional relationship between the focal plane and the heights of the first and second pinhole conjugate planes is not limited to the example shown in FIG. If the heights of the two pinhole conjugate planes are different, the heights of the first and second pinhole conjugate planes are both set to either one above or below the focal plane height. Alternatively, the height of one of the first and second pinhole conjugate surfaces may be made to coincide with the height of the focal plane.

  In the example shown in FIG. 2A, the standard height of the upper surface of the inspection object 100 coincides with the height c (that is, the height of the focal plane) in FIG. The height of the convex portion (micro foreign matter) on the upper surface of 100 becomes the height b between the heights a and c in FIG. 2A, and the height of the concave portion (scratch) on the upper surface of the inspection object 100 is shown in FIG. (A) The height d between the middle heights c and e. However, the positional relationship among the standard height of the upper surface of the inspection object 100, the height of the convex portion and the height of the concave portion, and the heights of the first and second pinhole conjugate surfaces and the focal plane is shown in FIG. It is not limited to the example shown in 2 (a).

  Since the heights of the first and second pinhole conjugate planes and the focal plane are set as described above, it corresponds to the surface shape of the upper surface of the object 100 to be inspected indicated by the solid line in FIG. In addition, the detection signal shown in FIG. 2B is obtained from the first light detection unit 21A (that is, the first light detector 33A) and the second light detection unit 21B (that is, the second light detection). The detection signal shown in FIG. 2C is obtained from the device 33B). 2B and 2C, the vertical axis indicates the signal intensity, and the horizontal axis indicates the horizontal position corresponding to the surface shape of the upper surface of the inspection object 100 in FIG. This also applies to FIG. 2D described later. In the detection signal from the first light detection unit 21A, as shown in FIG. 2B, compared with the standard level obtained corresponding to the standard height of the upper surface of the inspection object 100, While the level obtained corresponding to the convex portion on the upper surface of the inspection object 100 is high, the level obtained corresponding to the concave portion on the upper surface of the inspection object 100 is low. On the contrary, in the detection signal from the second light detection unit 21B, as shown in FIG. 2C, the standard signal obtained corresponding to the standard height of the upper surface of the inspection object 100 is obtained. Compared with the level, the level obtained corresponding to the convex portion on the upper surface of the inspection object 100 is lower, while the level obtained corresponding to the concave portion on the upper surface of the inspection object 100 is higher.

  In the present embodiment, the processing unit 22 is provided on the upper surface of the inspection object 100 on the condition that the processing unit 22 is determined to be a concave portion based on detection signals from the first and second light detection units 21A and 21B. Detect defects. In the present embodiment, the processing unit 22 is a difference processing unit that obtains a difference signal according to the difference between the detection signal from the first light detection unit 21A and the detection signal from the second light detection unit 21B. Based on the differential amplifier 41 and the output signal (difference signal) of the differential amplifier 41, data processing for detecting a defect on the upper surface of the inspected object 100 is performed on the condition that it is determined to be a concave portion. And a data processing unit 42.

  Corresponding to the surface shape of the upper surface of the inspected object 100 indicated by the solid line in FIG. 2A, the detection signals from the first and second light detection units 21A and 21B are the signals shown in FIG. In the case of the signal shown in FIG. 2C, the output signal (difference signal) of the differential amplifier 41 becomes the signal shown in FIG. In the output signal (difference signal) of the differential amplifier 41, as shown in FIG. 2D, a standard level (for example, zero level) obtained corresponding to the standard height of the upper surface of the inspection object 100 is obtained. ), The level obtained corresponding to the convex portion on the upper surface of the inspection object 100 is low, while the level obtained corresponding to the concave portion on the upper surface of the inspection object 100 is high. And in the output signal (difference signal) of the differential amplifier 41 as shown in FIG. 2D, between the standard level, the level obtained corresponding to the convex part, and the level obtained corresponding to the concave part Is a relative position in the optical axis L direction of the inspection object 100 with respect to the height of the focal plane and the first and second pinhole conjugate surfaces (that is, the upper surface of the inspection object 100). The standard height, the height of the convex part and the height of the concave part are shifted, the protruding amount of the convex part (difference between the height of the convex part and the standard height) and the concave part amount (the height of the concave part) Even if the difference from the standard height is changed, it is maintained.

  Therefore, whether or not the portion is a convex portion can be determined depending on whether or not the output signal of the differential amplifier 41 is higher or lower than the standard level.

  In the present embodiment, the data processing unit 42 is, for example, an image based on the output signal of the differential amplifier 41 (an image composed of the intensity value of the output signal of the differential amplifier 41 for each two-dimensional position. Obtained by capturing the intensity value of the output signal of the differential amplifier 41 in synchronism with the operation of the unit 13), and obtaining an image of the predetermined value from the standard level of the output signal of the differential amplifier 41. The binarization process is performed using a lower level as a threshold value, labeling is performed, the feature extraction of the shape of the labeling region is performed, and the feature is compared with a preset feature to detect a defect on the upper surface of the inspection object 100. . In this case, binarization processing using a level that is lower than the standard level of the output signal of the differential amplifier 41 by a predetermined value as a threshold corresponds to the determination as a recess.

  Although not shown in the drawings, the processing unit 22 (particularly, the data processing unit 42) outputs the presence / absence of defects, the number and positions of defects to the outside as inspection results, and does not illustrate them as necessary. Display on the display. As the inspection result, only the presence / absence of a defect may be output.

  In the surface defect inspection apparatus 1 according to the present embodiment, as can be seen from the above description, scratches (concaves) that are defects on the surface of the object to be inspected are separated from minute foreign substances (convex) adhering to the surface of the object to be inspected. Since the detection can be performed separately, it is possible to reduce the erroneous detection that erroneously detects dust as a scratch and improve the accuracy of defect detection. In this embodiment, since the height of the focal plane or the like is set to a certain height with respect to the inspection object 100, the two-dimensional scanning of the laser light in the focal plane only needs to be performed once. Compared to a case where a plurality of images are acquired by changing the height of the focal plane relative to 100 and performing two-dimensional scanning of the laser light in the focal plane at each height, respectively. Can be greatly shortened. Furthermore, the surface defect inspection apparatus 1 according to the present embodiment does not require the use of a waveguide device, and is configured with general optical components such as those used in a general confocal microscope. Cost can be greatly reduced compared to the case where a device is required. As described above, according to the present embodiment, it is possible to reduce erroneous detection and increase the accuracy of defect detection, and it is possible to simultaneously shorten inspection time and reduce costs.

  When a waveguide is used for the detection system, the detection sensitivity for extremely small steps is high, but the signal due to the unevenness may be inverted for steps of about the wavelength or more.

  In the present embodiment, the height of the first pinhole conjugate surface can be adjusted, for example, by adjusting the position of the first light detection unit 21A in the optical axis direction. Since the adjustment of the height of the pinhole conjugate surface can be performed by adjusting the position of the second light detection unit 21B in the optical axis direction, for example, the height of the first and second pinhole conjugate surfaces is set. High degree of freedom.

  FIG. 3 is a schematic configuration diagram showing a surface defect inspection apparatus 51 according to a comparative example compared with the surface defect inspection apparatus 1 according to the present embodiment, and corresponds to FIG. 3, elements that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and redundant descriptions thereof are omitted.

  The surface defect inspection apparatus 51 according to this comparative example is different from the surface defect inspection apparatus 1 according to the present embodiment in that one light detection unit 21 is used instead of the first and second light detection units 21A and 21B. Only the point that the half mirror 20 is removed, and the point that the data processing unit 52 is used instead of the processing unit 22 (the differential amplifier 41 and the data processing unit 42). Thereby, the surface defect inspection apparatus 51 by this comparative example has the same structure as a general scanning confocal microscope.

  In this comparative example, the detection light reaching the half mirror 19 from the inspection object 100 is detected by the light detection unit 21 after being bent by the half mirror 19.

  The light detection unit 21 is arranged at a position conjugate with a condensing lens 31 that condenses the detection light and a focal plane (focal plane near the upper surface of the inspection object 100) on which the irradiation laser light is condensed. A pinhole plate 32 that restricts the light collected by the light 31 to a pinhole shape, and a photodetector 33 that detects the light that has passed through the pinhole of the pinhole plate 32. The photodetector 33 outputs an electric signal having an intensity corresponding to the amount of received light. The pinhole of the pinhole plate 32 is formed on the optical axis of the condenser lens 31, and the size of the pinhole is approximately the same as the diameter of the light spot formed on the pinhole plate 32. It is set to be.

  In this comparative example, if a plane conjugate with the pinhole plate 32 is called a pinhole conjugate plane, as can be seen from the above description, the pinhole conjugate plane coincides with the focal plane on which the irradiated laser beam is condensed. ing. This point will be described with reference to FIG. 4A schematically shows the height positions b to d in the optical axis L direction, and schematically shows an example of the surface shape of the upper surface of the inspection object 100 in a cross section including the optical axis L with a solid line. FIG. The height positions b to d in FIG. 4A are the same as the height positions b to d in FIG. 2A, and the surface shape of the upper surface of the inspection object 100 shown in FIG. It is the same as the surface shape of the upper surface of the inspection object 100 shown in FIG. In this comparative example, not only the focal plane on which the irradiation laser beam is condensed but also the pinhole conjugate plane is set to the height c.

  In this comparative example, since the focal plane and the pinhole conjugate plane are both set to a height c, the surface of the upper surface of the inspected object 100 indicated by the solid line in FIG. Corresponding to the shape, the signal shown in FIG. 4B is obtained from the light detector 21 (that is, the light detector 33). In FIG. 4B, the vertical axis indicates the signal intensity, and the horizontal axis indicates the horizontal position corresponding to the surface shape of the upper surface of the inspection object 100 in FIG. In the detection signal from the light detection unit 21, as shown in FIG. 4B, the inspection object is compared with the standard level obtained corresponding to the standard height of the upper surface of the inspection object 100. Both the level obtained corresponding to the convex portion on the upper surface of 100 and the level obtained corresponding to the concave portion on the upper surface of the inspection object 100 are both low.

  Therefore, the two-dimensional laser beam in the focal plane is set such that the height of the focal plane and the pinhole conjugate plane is set to a certain level with respect to the surface of the inspected object 100 as shown in FIG. If the scanning is performed only once, the intensity of the detection signal from the light detection unit 21 is weakened in the place where the unevenness exists as shown in FIG. Whether it is concave or convex cannot be determined. Therefore, by performing two-dimensional scanning only once, not only defects (concaves) that are defects on the surface of the object to be inspected, but also dust that can be removed by cleaning operations and cannot be said to be defective (attached to the surface of the object to be inspected) The minute foreign matter (convex) is also erroneously detected as a defect, and the detection accuracy is reduced.

  Therefore, in this comparative example, the height of the focal plane and the pinhole conjugate plane with respect to the inspection object 100 is changed, and two-dimensional scanning of the laser beam in the focal plane is performed at each height. Each dimension scan is performed. Then, the data processing unit 52 acquires a plurality of images based on detection signals from the light detection unit 21 corresponding to each height, and performs three-dimensional observation of the inspection object 100, thereby performing unevenness determination. Scratches (concaves) that are defects on the surface of the inspection object 100 are detected separately from minute foreign substances (convexity) adhering to the surface of the inspection object 100. This reduces false detection and increases the accuracy of defect detection.

  However, according to this comparative example, the height of the focal plane is relatively changed with respect to the object to be inspected 100, and two-dimensional scanning of the laser light in the focal plane is performed at each height to obtain a plurality of images. The inspection time becomes longer because it is necessary to do this.

  On the other hand, in the present embodiment, as described above, the two-dimensional scanning of the laser light in the focal plane is performed only once with the height of the focal plane or the like being set to a certain height with respect to the inspection object 100. Therefore, the inspection time can be greatly shortened.

  In the comparative example, when the unevenness is observed based on the signal intensity of the detection signal from the light detection unit 21, the signal intensity is easily affected by the dependence on the reflectance of the inspection object 100, and the unevenness is in focus. If the size is within the depth, the change in the signal is small and the detection sensitivity is not good.

  In contrast, in the present embodiment, the differential amplifier 41 obtains a differential signal corresponding to the difference between the detection signal from the first light detection unit 21A and the detection signal from the second light detection unit. In addition to being less susceptible to the signal intensity depending on the reflectance of the object to be inspected 100, the amount of change in the signal at the concave and convex portions in the differential signal is increased, and the detection capability of the concave and convex portions is enhanced.

  The surface defect inspection apparatus 1 according to the present embodiment may be modified as described below, for example.

  Instead of the first pinhole plate 32A, for example, an optical fiber having a core of the same size as the pinhole of the first pinhole plate 32A may be used as the light limiting portion. In this case, one end face of the optical fiber may be disposed on the optical axis, and light emitted from the other end of the optical fiber may be detected by the photodetector 33A. Similarly, instead of the second pinhole plate 32B, an optical fiber may be used as the light limiting portion.

  Further, the differential amplifier 41 is removed in the processing unit 22, and the data processing unit 42 captures an image based on the detection signal from the first light detection unit 21A and an image based on the detection signal from the second light detection unit 21B, respectively. A difference image obtained by taking a difference between the images may be obtained, and a defect on the surface of the inspection object may be detected based on the difference image. In this case, for example, the data processing unit 42 binarizes and labels the difference image using a level that is a predetermined value lower than a standard value (a value corresponding to a value of a place without unevenness) as a threshold value. Then, a feature on the shape of the labeling region is extracted, and the feature is compared with a preset feature to detect a defect on the upper surface of the inspection object 100. Also in this case, substantially the same processing as the processing of the processing unit 22 including the differential amplifier 41 and the data processing unit 42 used in the surface defect inspection apparatus 1 according to the present embodiment is performed. It will be. However, this embodiment is more preferable from the viewpoint of S / N.

  As mentioned above, although embodiment of this invention and its modification were demonstrated, this invention is not limited to these.

  For example, although the epi-illumination microscope configuration is employed in the embodiment, a transmission microscope configuration may be employed in the present invention. In the epi-illumination microscope configuration as in the present embodiment, reflection, fluorescence, scattered light, etc. can be captured from the optical response from the object 100 to be inspected by the irradiated light, whereas in the transmission microscope configuration, Of the optical response from the object 100 to be inspected by the irradiation light, it is possible to capture the degree of fluorescence, scattered light, phase change of light, and the like.

  In addition, the inspection object 100 is not limited to a glass substrate, a silicon substrate, other substrates, or the like.

It is a schematic block diagram which shows the surface defect inspection apparatus by one embodiment of this invention. It is a figure which shows the example of the surface shape of the surface of a to-be-inspected object, and the detection signal in embodiment shown in FIG. It is a schematic block diagram which shows the surface defect inspection apparatus by a comparative example. It is a figure which shows the example of the surface shape of the surface of a to-be-inspected object, and the detection signal in the comparative example shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface defect inspection apparatus 11 Laser light source 12 Beam expander 13 Scanning unit 14 Scanning lens 17 Objective lens 20 Half mirror (light division part)
21A, 21B Light detection unit 22 Processing unit 31A, 31B Condensing lens 32A, 32B Pinhole plate (light limiting unit)
33A, 33B Photodetector 41 Differential amplifier (difference means)
100 Inspection object

Claims (4)

An illumination optical system that condenses light on a focal plane and irradiates the object to be inspected, and scans a condensing point on the focal plane;
A light dividing unit that divides light obtained from the inspection object by irradiation of light by the illumination optical system;
A first light detection unit for detecting one light after being split by the light splitting unit;
A second photodetecting unit for detecting another one of the lights after being divided by the light dividing unit;
A processing unit for detecting defects on the surface of the inspection object based on detection signals from the first and second light detection units;
With
The first light detection unit is disposed at a position conjugate with the first condensing lens that condenses the one light and the first plane near the focal plane, and is collected by the first condensing lens. A first light restriction unit that restricts the emitted light into a pinhole shape, and a first photodetector that detects light after being restricted by the first light restriction unit,
The second light detection unit is disposed at a position conjugate with a second condensing lens that condenses the other one light and a second plane near the focal plane, and the second condensing lens. A second light restricting portion for restricting the light collected by the pinhole shape, and a second photodetector for detecting the light after being restricted by the second light restricting portion,
The surface defect inspection apparatus, wherein the first plane and the second plane are displaced in the optical axis direction.   The processing unit detects defects on the surface of the inspection object on the condition that the processing unit is determined to be a recess based on detection signals from the first and second light detection units. The surface defect inspection apparatus according to claim 1.   The processing unit includes a difference processing unit that obtains a difference signal according to a difference between a detection signal from the first light detection unit and a detection signal from the second light detection unit, and is based on the difference signal. 3. A surface defect inspection apparatus according to claim 1, wherein a defect on the surface of the inspection object is detected.   The processing unit obtains a difference image obtained by taking a difference between an image based on a detection signal from the first light detection unit and an image based on a detection signal from the second light detection unit, and based on the difference image 3. The surface defect inspection apparatus according to claim 1, wherein a defect on the surface of the inspection object is detected.

Images