JP2005098970A - Method and apparatus for identifying foreign matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an identification method and an identification apparatus for especially allowing a detected foreign matters, to identify whether an inspection target is one adhering to the surface, regarding the apparatus for inspecting foreign matters formed on the surface of or in the inside of the inspection target. <P>SOLUTION: The identification apparatus acquires image information (focal point image information), in which the upper surface of the inspection target is focused from an imaging device; and image information (non-focal image information), in which the focal point is shifted from the surface to the lower surface and at a position for enabling an internal foreign matter to be recognized, thus identifying the surface foreign matters and internal foreign matters, based on the focal point image information and non-focal point image information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for inspecting foreign matter formed on or in an inspection object, and more particularly, to an identification method and apparatus for identifying whether or not a detected foreign object is a substance attached to a surface of the inspection object. There is something to do.

In a foreign substance inspection apparatus using a conventional optical microscope and an imaging apparatus such as a CCD, the surface of an inspection object (sample) is imaged with transmitted light or reflected light. At this time, the foreign matter existing on the surface or inside of the inspection object is captured as an image having a darker luminance level than the surface portion. This dark luminance level image area is detected as a foreign object.
However, it is difficult to identify whether the detected foreign matter is above or below the surface of the inspection object.
Hereinafter, the in-focus position of an image acquired through a microscope is referred to as an inspection object (sample) surface. Further, in the Z-axis direction from the surface, foreign matter existing above is referred to as surface foreign matter, and foreign matter existing below is referred to as internal foreign matter.
For example, the foreign substance is a general term for a hole, a dent, a groove formed on the surface of the inspection object, such as a defect, a void, a groove, a hole, and an unevenness, and a foreign object, a cavity, and the like formed inside. In addition, the surface foreign matter includes foreign matter attached to the surface and mounted parts.
In addition, for example, the foreign matter is a part of the original sample (inspection object) that has an external change caused by factors such as external time such as processing, and includes internal cavities, defects, scratches, Includes deposits, pattern wiring, generated films, mounted components, solder, and the like.

As a method for identifying the detected foreign matter, for example, holes, dents, grooves, and cavities formed in the inspection target surface where detection is expected (or known in advance), and further, If the object to be inspected is a material that is close to transparency, foreign materials with different refractive indexes, etc., and mounted parts are stored as image information, compared with the actually detected foreign materials, and foreign materials at the same position are removed from the inspection object. There is a method called template comparison to exclude.
In this comparison method using a template, a formed product and a foreign material are identified by comparing the detected foreign material size, shape, and luminance level difference with a template image. However, this identification method may cause oversight or misrecognition due to differences in the shape, size, and luminance level of foreign matter. Further, in the comparison method using the template, position information of foreign matters (for example, holes, mounted parts, etc.) formed on the inspection target in advance is required, and much time is required for creating the template. (For example, refer to the prior patent document 1).

JP-A-3-72249

In the above-described prior art, it has been difficult to identify whether the detected foreign matter exists above or below the surface of the inspection object.
In addition, if identification is performed using a comparison method using a template, there may be cases where oversight or misrecognition may occur due to differences in the shape, size, and luminance level of the foreign material. In addition, it took a lot of time to create a template. The purpose of the present invention is to reliably identify the foreign matter (surface foreign matter) adhering to the surface of the inspection target or the internal foreign matter formed on the surface of the inspection target. And a device for the same are provided.

In order to achieve the above object, the foreign matter identification method of the present invention uses a microscope device and an imaging device, acquires a reference image at a focal position serving as a reference for an inspection object, and differs at least at one focal position different from the focal position. An image of a focal position is acquired, the acquired images are compared, and a foreign matter above and below a reference focal position is identified from the comparison result.
Further, the foreign matter identification device of the present invention includes a microscope apparatus having a stage on which an inspection object is placed, an imaging apparatus that captures an enlarged image of the inspection object magnified by the microscope apparatus, and a control apparatus that controls the stage. In the foreign object identification device provided, the microscope device has an imaging device that matches a focal plane with the surface of the object to be inspected to obtain at least one image having a focal position different from the reference focal position, and a position different from the imaging apparatus. A second imaging device is provided so as to be in focus, the imaging device acquires image information focused on the surface of the inspection object, and the second imaging device changes image focus to a position different from the surface. To obtain the differential component of the image information out of focus, recognize the part where the differential value is large, and identify the part in the former image information and the part where the recognized differential value is large And butterflies.

That is, in order to achieve the above object, the foreign matter identifying method and apparatus of the present invention includes a microscope apparatus having a stage on which an inspection object is placed, and an imaging apparatus that captures an enlarged image of the inspection object magnified by the microscope apparatus. And a control device that controls the stage on which the inspection object is placed, and a recording device that records the inspection conditions according to the inspection object, and outputs from the imaging device based on the inspection conditions recorded in the recording device In an inspection device that analyzes the image information and inspects foreign matter on the inspection target, internal foreign matter such as holes, dents, or grooves originally present on the surface or inside of the inspection target and foreign matter (surface foreign matter) attached to the surface Image information focused on the surface of the object to be inspected (focused image information) and image information shifted from the surface to the position where the internal foreign object can be recognized. Get the (non-focus image information) and is intended to distinguish the foreign surface particles and internal foreign substances on the basis of the focus image information and unfocused image information.
In the foreign matter identifying method and apparatus of the present invention, the information of the focused image information and the non-focused image information preferably calculates a differential component of the non-focused image information, and the calculated differential value is equal to or greater than a predetermined value. The pixel region portion in which the portion of the pixel region substantially coincides with the portion of the pixel region in which the brightness level of the focused image information is less than a predetermined value is identified as an internal abnormal object.
Preferably, in the foreign matter identifying method and apparatus according to the present invention, the information on the focused image information and the unfocused image information includes a portion of the pixel area where the luminance level of the unfocused image information is less than a predetermined value, The pixel region portion where the pixel region portion where the luminance level of the image information is less than a predetermined value substantially matches is identified as an internal abnormal object.

  In addition, the foreign substance identification apparatus of the present invention focuses on a microscope apparatus, an imaging apparatus that focuses the focal plane on the surface of the inspection object, and a different position on the basis of the microscope apparatus as means for obtaining two pieces of image information having different focal planes. An imaging device is arranged and the focal position of the latter imaging device is adjusted.

  That is, the present invention acquires an image of an inspection object using an optical microscope and an imaging device, analyzes the acquired image, and forms fine holes, irregularities, and patterns formed on or in the inspection object. In particular, the detected foreign matter is used to identify whether the inspection object is attached to the surface.

  According to the foreign matter identification method and foreign matter identification device of the present invention, it is possible to identify a foreign matter formed under the sample surface and a foreign matter attached to the surface without prior information such as a sample template and the like, and does not require inspection. Can be excluded from the inspection target, so that the inspection preparation time and the inspection time can be shortened.

Embodiments of the present invention will be described below.
According to the present invention, in order to distinguish an internal foreign matter such as a hole, a dent, or a groove originally present on the surface or inside of the inspection object and a foreign matter (surface foreign matter) adhering to the surface, the imaging device can detect the surface of the inspection object. Focused image information (focused image information) and image information (nonfocused image information) shifted from the front surface to the bottom surface and a position where an internal foreign object can be recognized are acquired. Based on the image information, the surface foreign matter and the internal foreign matter are identified. At this time, the information of the in-focus image information and the non-focus image information is preferably calculated by calculating a differential component of the non-focus image information, the portion of the pixel area where the calculated differential value is equal to or greater than a predetermined value, and the in-focus image information. A portion of the pixel area in which the portion of the pixel area whose luminance level of the image information is less than a predetermined value substantially matches is identified as an internal abnormal object.
Preferably, the information on the in-focus image information and the non-focus image information includes a portion of a pixel area where the brightness level of the non-focus image information is less than a predetermined value, and the brightness level of the focus image information is less than a predetermined value. A part of the pixel area in which the part of the pixel area substantially matches is identified as an internal abnormal object.

  In addition, the foreign substance identification apparatus of the present invention focuses on a microscope apparatus, an imaging apparatus that focuses the focal plane on the surface of the inspection object, and a different position on the basis of the microscope apparatus as means for obtaining two pieces of image information having different focal planes. An imaging device is arranged and the focal position of the latter imaging device is adjusted.

  That is, the present invention acquires an image of an inspection object using an optical microscope and an imaging device, analyzes the acquired image, and forms fine holes, irregularities, and patterns formed on or in the inspection object. In particular, it is possible to identify whether or not the detected foreign matter is attached to the surface of the object to be inspected.

A specific embodiment of the identification method of the present invention will be described with reference to FIGS. 7, 2 to 4 and 5. FIG. 7 and 2 to 4 are diagrams for explaining the principle of the embodiment of the present invention, and FIG. 5 is a flowchart of an example of processing operation of the embodiment of the present invention. Reference numeral 106 denotes a sample, 701 and 702 are internal foreign matters, 703 is a surface foreign matter, 704 is a camera focus surface, 705 is an objective lens, 706 is an eyepiece lens, 707 is a camera imaging surface, and 708 is an optical axis. The internal foreign substances 701 and 702 are holes formed in the sample in the example of FIG.
Light from a light source (not shown) (epi-illumination light) is irradiated perpendicularly to the sample 106, the irradiated light is reflected from the surface of the sample 106, and the reflected light passes through the objective lens 705 and the eyepiece lens 706 and is captured by the camera. An image is formed on the surface 707.

  FIG. 7A is a diagram for explaining the optical system when the camera focus plane (focus) is in alignment with the upper surface of the sample 106 that is the inspection object. FIG. 7B is a diagram for explaining the optical system when the camera focus plane (focus) is in the downward direction from the upper surface of the sample 106.

  When the upper surface of the sample 106 is in focus, an image acquired by the optical image formed on the camera imaging surface 707 is as shown in FIG. FIG. 2 is a diagram showing an example of an image (FIG. 2A) taken by the first camera 104 and a luminance profile (FIG. 2B) of the image. 201 and 202 are images of the holes 701 and 702 formed in the sample to be detected, 203 is an image of the foreign material 703 on the surface of the sample 106, and 204 is a luminance profile of the broken line portion. The image in FIG. 2 (a) is an image obtained by reflected illumination of a microscope. The hole 701 (image 201), the hole 702 (image 202), and the foreign substance 703 (image 203) are compared with the images of other surface portions. The brightness level is low because the reflected light is dark and dark. FIG. 2 (b) shows the luminance profile 204 of the broken line part of FIG. 2 (a), indicating that the luminance of the images 201 and 202 and the image 203 are both low.

  As shown in FIG. 7B, when the focal point is below the upper surface of the sample 106, an image acquired by the optical image formed on the camera imaging surface 707 is shown in FIG. As shown. FIG. 3 is a diagram showing an example of an image (FIG. 3A) taken by the camera B105 and a luminance profile (FIG. 3B) of the image. Reference numerals 301 and 302 denote images of holes 701 and 702 formed in the sample 106 to be detected, 303 denotes an image of the foreign substance 703 on the surface of the sample 106, and 304 denotes a luminance profile of a broken line portion. 2 and 3, the hole images 201 and 301 capture the same hole 701, the hole images 202 and 302 capture the same hole 702, and the foreign matter images 203 and 303 capture the same foreign matter 703. Yes. The image in FIG. 3A is taken at the same location as in FIG. 2, but the focal position of the microscope is slightly shifted from the inside of the sample (downward from the surface) compared to FIG. For this reason, the image as a whole is blurred, and the change in the luminance level is small. The focal position is desirably above the lower surface of the sample 106, but may be aligned with the lower surface of the sample 106.

In FIG. 3A, the holes 701 and 702 (images 301 and 302) and the foreign material 703 (image 303) have lower reflected light and darker than the surface portions, and therefore have a lower luminance level than the surface portions. . FIG. 3B shows the luminance profile 304 of the broken line part of FIG. 3A, and indicates that the luminance of the images 301 and 302 of the holes 701 and 702 and the luminance of the image 303 of the foreign material 703 are both low.
However, since the surface foreign matter 703 exists in a direction in which the focus is shifted from the holes 701 and 702, the luminance level looks high. Further, the holes 701 and 702 have cavities deeper (downward) than the upper surface of the sample 106, and the brightness level is low because there are places where focus is achieved even in the case of FIG. 7B. For example, if the hole is open parallel to the direction of the optical axis 708, the brightness levels of the images of the holes 701 and 702 are the same regardless of whether the image is taken at the focal point shown in FIGS. 7 (a) or 7 (b).
That is, the images 301 and 302 of the holes 701 and 702 have a focal point located below the upper surface of the sample 106, and therefore the luminance level is equal to or slightly higher than that of the images 201 and 202 of the holes 701 and 702. Although it is small, the luminance level is low because the reflected light is less and darker than the image of other parts. Therefore, since the difference in luminance level with other parts is large, the differential value of the luminance level becomes high.
On the other hand, the image 303 of the foreign object 703 is out of focus in the image acquired at the focus in FIG. 7B, and thus is a blurred image from the image 203, and the luminance level is close to the luminance level of the surface. .

Next, an embodiment of a method for identifying a foreign object will be described with reference to FIGS.
First, in the image of FIG. 2, a part having a level less than a predetermined luminance level is detected as a foreign object, and the position coordinates of the foreign object are calculated. As a method for calculating the position coordinates, for example, a pixel region having a luminance level lower than a predetermined luminance level is detected by binarization for each pixel, and the detected barycentric position of each cluster is set as the position coordinates of the foreign object.
Further, a differential value of the luminance level is calculated for the image of FIG. Then, a portion where the differential value is a predetermined value or more is detected as a bright spot, and the position coordinates of the bright spot are obtained. If the size of a foreign object is a size close to one pixel to several pixels, the detected shape of each lump is similar to the shape of a foreign object, and the size of a foreign object is a size of several pixels or more. For example, the shape of each detected mass is close to the contour shape of the foreign matter. As a method for calculating the position coordinates, for example, a pixel area having a predetermined luminance level or more is detected by binarization for each pixel, and the detected barycentric position of each mass is used as the position coordinates of the foreign object.
FIG. 4 shows an example of a binarized image calculated from the differential value calculated from the image (FIG. 3A) acquired by the camera B105. 401 and 402 are binarized images of holes, and 403 is a binarized image of abnormal surface objects. When the surface abnormal object 403 is binarized, the luminance actually becomes the same as that of the surrounding black part as shown in FIG. 4, but in FIG. 4, it is drawn brightly so as to be distinguished from the surrounding black part. .
Then, the position where the position coordinates of the foreign matter obtained from the image of the camera A104 (FIG. 2 (a)) and the bright spot obtained from the image of the camera B105 (FIG. 3 (a)) coincide with the position which does not coincide is detected. Then, the foreign substance at the matching position is determined as an internal abnormal object, and the foreign substance at the non-matching position is determined as an abnormal surface object.

  In this way, it is possible to distinguish holes and foreign objects based on whether or not the foreign object detection result in FIG. 2 and the binarized image result calculated from the differential value of the luminance level in FIGS. The position and distribution of the holes can be obtained without mixing with foreign substances.

  As a simpler method, a portion with a low luminance level according to the image in FIG. 2 is compared with a portion with a low luminance level according to the image in FIG. 3 (a cluster of pixels). It is also possible to determine that the foreign material is distributed downward from the focal position in FIG. Further, although the luminance level in the image of FIG. 2 is a low portion, the portion in which the luminance level is not so low in the image is a surface foreign matter (foreign matter distributed upward from the focal position in FIG. 7A). Can be identified.

FIG. 4 shows a case where the luminance level is differentiated for each pixel in the image of FIG. 3A, and the pixel having a luminance level with a differentiated value less than a predetermined value is “0” and the other pixels are “255”. This is an example of the binarized image. 401 and 402 are binarized images of the holes 701 and 702, and 403 is a binarized image of the abnormal surface object 703. The surface abnormal object 703 is actually the same as the surrounding black part, but in FIG. 4, it is drawn with diagonal lines to distinguish it from the surrounding black part.
Then, the position coordinates of the foreign matter obtained from the image of FIG. 2A and the position where the bright spot obtained from the image of FIG. Is determined as an internal foreign matter, and a foreign matter at a position that does not match is determined as a surface foreign matter, and the internal foreign matter and the surface foreign matter are identified.

In FIG. 5, in step 501, an image ImA is acquired at the focal position shown in FIG.
In step 502, the binarization threshold ThA at the focal position in FIG. 7A is read from the input device or memory. The memory is, for example, a built-in control personal computer (described later) that executes this processing operation, or an external storage device. The input device is a man-machine interface between a control personal computer and an operator, such as a keyboard, a pointing device, and an operation panel.
In step 503, binarization processing is performed using the binarization threshold ThA read for the image ImA, and a binarized image BimA is calculated. That is, for example, for each pixel, a pixel whose luminance level is less than the binarization threshold ThA is set to “0”, and a pixel whose luminance level is equal to or higher than the binarization threshold ThA is set to “255” (the minimum luminance level). When the value is “0” and the maximum value is “255”).
In step 504, a labeling process is performed on a cluster of pixels having a luminance level less than the binarization threshold ThA from the binarized image BimA.
In step 505, the position coordinate Pn on the image of each label created by the labeling process in step 504 is stored in the memory. Here, n is an integer, and n ≧ 0.

In step 506, the sample is moved to the focal position shown in FIG.
In step 507, an image ImB is acquired at the focal position shown in FIG.
In step 508, the luminance level of the image ImB is differentiated for each pixel, and the differential value is acquired as an image ImBd.
In step 509, the binarization threshold ThB is read from the input device or memory.
In step 510, binarization processing is performed using the binarization threshold ThB read for the image ImBd, and a binarized image BimB is calculated. That is, for example, for each pixel, a pixel whose luminance level is less than the binarization threshold ThB is set to “0”, and a pixel whose luminance level is the binarization threshold ThB or more is set to “255” (minimum luminance level). When the value is “0” and the maximum value is “255”).
In step 511, a labeling process is performed on a cluster of pixels having a luminance level less than the binarization threshold ThB from the binarized image BimB.
In step 512, the position coordinate pk on the image of each label created by the labeling process in step 511 is stored in the memory. Here, k is an integer, and k ≧ 0.

In step 513, the values of all the position coordinates Pn and all the position coordinates pk are respectively compared. If the position coordinates Pn are within the predetermined range with respect to the position coordinates pk, the process proceeds to step 514. Proceed to step 515. For example, the minimum value of the distance between two points between the position coordinate Pn and the position coordinate pk is calculated, and if the minimum value of the distance between the two points is within a predetermined value, it is set within the predetermined range.
For example, the position coordinates P1 and the position coordinates p1 to pk are compared one after another to check whether any of the position coordinates p1 to pk substantially matches the position coordinates P1.
In step 514, a combination of position coordinate values Pn and pk within a predetermined range is extracted as a target foreign matter and stored as an internal foreign matter.
In step 515, it is determined whether or not the comparison is completed for the combination of the position coordinates pk for all the position coordinates Pn. If the comparison is completed, the position coordinates Pn that are not associated with the position coordinates pk are set as surface foreign matters. Store, and the identification processing operation ends. If all the comparisons have not been completed, the process returns to step 513 to continue the identification process.
As a result, for example, when a hole processed in a sample is inspected, foreign matter adhering to the surface of the sample is not erroneously detected, and only the detected portion can be inspected, so that a quick inspection can be performed.

  An embodiment of an apparatus for carrying out the identification method of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the identification device according to one embodiment of the present invention. 6 discriminates foreign matter adhering to the surface of the object to be inspected (sample) and holes opened from the surface of the sample toward the inside, and also has a function of inspecting the position and distribution of the holes. Yes.

Reference numeral 101 denotes a microscope, 102 denotes a revolver for switching the objective lens, 103 denotes an autofocus optical unit, 120 denotes an optical image, 604 denotes a camera, and 111 denotes a control personal computer. The camera 604 includes, for example, an image sensor such as a CCD, converts light (optical image 120) incident from the microscope 101 into an electrical signal, and outputs the electrical signal to the control personal computer 111.
Reference numeral 107 denotes an X-axis stage, 108 denotes a Y-axis stage, 109 denotes a Z-axis stage, and 106 denotes an inspection object (sample) placed on the Y-axis stage 108. The X-axis stage 107 and the Y-axis stage 108 are arranged on the Z-axis stage 109, can move in the XY-axis direction and the Z-axis direction, and can control the observation position. Since the sample 106 is placed on the Y-axis stage 108, the sample 106 moves in the X-axis direction, the Y-axis direction, and the Z-axis direction as the X, Y, and Z stages move.

Reference numeral 116 denotes reflected illumination; 117 and 118, half mirrors; 122, laser light.
As shown in FIG. 6, the reflected illumination light 116 enters from the lateral direction of the microscope 101, is reflected by the half mirror 117, passes through the objective lens (not shown) attached to the revolver 102, and passes through the surface of the sample 106. Irradiate. The sample 106 emits reflected light (optical image 120) by the irradiated light, and enters the microscope through the objective lens. That is, the light that has passed through the objective lens passes through the half mirrors 117 and 118 and forms an image as an optical image 120 at an imaging plane position (photoelectric conversion plane) of the camera 604 by an imaging lens (not shown). The camera 604 converts the optical image 120 into image data and outputs it to the control personal computer 111.

  Reference numeral 110 denotes a stage control unit, and 112 denotes a position control board mounted in the control personal computer 111. The stage control unit 110 controls the stage mechanism (the X-axis stage 107, the Y-axis stage 108, and the Z-axis stage 109) according to a command from the position control board 112.

An image input board 113 is mounted in the control personal computer 111 and captures images acquired by the first camera 104 and the second camera 105. Reference numeral 114 denotes a display that displays at least one of a control screen of the inspection apparatus, a captured image, and a processed image.
Reference numeral 115 denotes an autofocus control unit, which focuses the first camera 104 on the surface of the inspection object 106 by a combination of the autofocus optical unit 103, the stage control unit 110, and the Z-axis stage 109. That is, the autofocus control unit 115 outputs laser light from the autofocus optical unit 103, irradiates the surface of the sample 106 at a right angle with the half mirror 118, detects the reflected laser light, and is not in focus. An error signal is output to the stage control unit 110. The stage control unit 110 sends a control signal to the Z stage 109 in response to the input error signal. The Z stage 109 moves the stage up and down according to the input control signal.

  The control personal computer 111 processes an image input from the camera 604 via the image input board 113 and outputs a display image to the display 114. The control personal computer 111 receives focus information from the autofocus control unit 115 and displays it on the display 114 or uses it as data for image analysis. In addition, the control personal computer 111 outputs focal length change information to the autofocus control unit 115 according to the set program to change the focal position. Also, the control personal computer 111 sends a signal to the revolver 102 to change the objective lens attached to the revolver 102 to an objective lens with a designated magnification read from the input device or memory.

  In the embodiment of FIG. 5 above, the image obtained by shifting the focal position downward from the upper surface of the sample and labeling the image binarized using the threshold after obtaining the differential image. However, either the image picked up by focusing on the surface of the sample or the image picked up by focusing below the surface of the sample may be differentiated, or both of the differentiated images may be binarized. Alternatively, both may be binarized without differentiation. FIG. 10 shows an example of the relationship between the luminance profile and the threshold ThB ′ in the case where the image captured by shifting the focal position shown in FIG. 3 downward from the upper surface of the sample and binarized with a predetermined threshold.

  In addition, the number of images acquired by changing the focal position is not limited to two. For example, using images acquired with the focal position downward or upward (in some cases, above the surface). Obviously, foreign matter may be identified by logical calculation of a plurality of images. For example, when the focal position is changed many times, it is effective for analyzing foreign matter on each film when a plurality of pattern films are generated and stacked on a semiconductor or insulator substrate. In addition, the identification method of the present invention can be applied to inspect whether there is a foreign object for each height of components having different heights of the mounted components.

With reference to FIG. 8, the processing of one embodiment of a method for binarizing without differentiating both will be described. FIG. 8 is a flowchart showing an example of processing operation according to an embodiment of the present invention.
In FIG. 8, the same step number is assigned to the same process as in FIG. In the flowchart of FIG. 8, step 508 of the flowchart of FIG. 5 is deleted, and step 510 is changed to step 810.
Description of the processing described in FIG. 5 is omitted.
When the processing from step 501 to step 507 is completed by the same processing as in FIG. 5 and proceeds to step 509, the binarization threshold ThB ′ is read from the input device or memory in step 509 as in FIG.
In the next step 810, the image ImB acquired in step 507 is binarized using the read binarization threshold ThB 'to calculate the binarized image BimB. In step 511, a labeling process is performed on a cluster of pixels having a luminance level less than the binarization threshold ThB ′ from the binarized image BimB.
Thereafter, the processing from step 512 is the same as in FIG.

Another embodiment of the foreign matter identifying method of the present invention will be described with reference to FIG. FIG. 9 is a diagram for explaining the principle of one embodiment of the present invention. The embodiment of FIG. 9 is a method for improving that the identification method described with reference to FIG. 7 takes a long time for identification because the imaging is performed at least twice by changing the focal position. That is, as shown in FIG. 9, a plurality of imaging devices are provided, and images having different focal positions are acquired simultaneously.
9, components having the same functions as those in FIG. 7 are denoted by the same reference numerals. In addition, 707 'is the imaging surface of the camera A, 807 is the imaging surface of the camera B, 808 is the optical axis, 806 is the eyepiece, 801 is the image plane position, and 119 is the half mirror.

In FIG. 9, the operation of the camera A is the same as that of the camera in FIG. That is, the image acquired by the camera A on the camera A imaging surface 707 ′ is focused on the upper surface of the sample 106 that is the inspection object. On the other hand, in the case of the camera B, the half mirror 119 splits the light reflected from the sample into two, and one is installed so that an image is formed on the camera A imaging surface 707 ′ by the eyepiece lens 706 as in the past. On the other hand, the other image is formed by the eyepiece lens 806 at the imaging plane position 801, and the camera B imaging plane 807 is provided at the front pin position from the imaging plane position 801.
As a result, an image focused on the upper surface of the sample 106 and an image at another focal position can be simultaneously acquired by another camera.
In the embodiment of FIG. 9, the camera B imaging surface 807 is provided at the front pin position from the imaging plane position 801, but it may be provided at the rear pin position from the imaging plane position 801, or the camera A imaging plane 707 ′. Since the focal positions of the camera B imaging surface 807 need only be relatively different, it is obvious that neither is the reference.
Further, as in the embodiment of FIG. 7, by changing the position of the Z stage, it is possible to further increase the variation of combinations of focal positions, and various processing methods can be applied to the analysis.

  A specific embodiment of FIG. 9 will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an identification apparatus according to an embodiment of the present invention. The identification device of FIG. 1 is a device for discriminating foreign matters adhering to the surface of an inspection object (sample) and holes opened from the surface of the sample toward the inside, and inspecting the positions and distribution of the holes. include. Components having the same functions as those in FIG. 6 are denoted by the same reference numerals. In addition, 104 is a camera A, 105 is a camera B, 119 is a half mirror, and 121 is an optical image incident on the camera B 105 dispersed by the half mirror 119.

  In FIG. 1, the camera A 104 has the same function and role as the camera 604 described in FIG. 1, acquires an image (optical image 120) focused on the upper surface of the sample 106, and controls the personal computer 111. Output to. In this case, as described with reference to FIG. 9, the optical image 120 is installed so as to form an image on the camera A imaging surface 707 ′ with the eyepiece lens 706. Similarly, the camera B 105 acquires an image (optical image 121) focused at a position below the upper surface of the sample 106 and outputs it to the control personal computer 111. In this case, as described in FIG. 9, the optical image 121 is installed so as to form an image behind the camera B imaging surface 807 by the eyepiece 806.

  By using the image as shown in FIG. 2 and the image as shown in FIG. 3 having a different focal position, there is no prior information such as the template of the sample, and the foreign matter formed below the sample surface and attached to the surface. Therefore, the inspection preparation time and the inspection time can be shortened.

As an embodiment of the present invention, an example of a procedure for detecting a hole penetrating a sample will be described below.
Procedure 1. An image focused on the sample surface is acquired, this image is binarized, black spots are detected, and coordinates on the image are obtained. At the time of detection, it is assumed that the area threshold value for determining the black point as the binarization threshold value can be set variably.
Procedure 2. An image focused on a position close to the back surface of the sample is obtained, an inspection window is set around the coordinates of the black spot obtained in step 1, and a differential image in the window is obtained. When there are a plurality of black spots in the procedure 1, there are a plurality of inspection windows. The window size is variable and can be set. In general, the size of the inspection window is determined by the expected inclination of the through hole to be detected. When the inclination is small, the window size is also small, and when the inclination is large, it is necessary to set it large.
Procedure 3. Among the differential images obtained in the procedure 2, the position where the differential value becomes large is detected and the coordinates on the image are obtained. It is assumed that the differential value serving as a threshold value at the time of detection is variable and can be set. If it is a through hole, it is a condition that it is detected in common in the procedure 1 and procedure 3 (logical product). For this reason, the processing order is performed in the order of an image focused on the sample surface and an image focused on the vicinity of the sample back surface. Here, the condition to be detected in common is coordinate information on the image, and coincidence detection having a range in consideration of the inclination of the hole and the image shift considered in the configuration of the apparatus.
Procedure 4. If there is something to be detected in common, set the inspection window for the points detected in common between the sample surface and the back of the sample, for example, near the middle, and display the differential image in the inspection window. Ask.
Procedure 5. Among the differential images obtained in step 4, the position where the differential value is large is detected. Here, let the detected point be a through hole.
The processing after the procedure 4 is performed in order to improve detection reliability because foreign matter, scratches, etc. adhering to both the sample surface and the sample back surface are assumed.
Further, it is expected that the detection reliability can be improved by repeatedly executing the processing after the procedure 4.

With reference to FIG. 11 and FIG. 12, a description will be given of an identification apparatus according to another embodiment of the present invention. FIG. 11 is a block diagram showing the configuration of the identification device according to one embodiment of the present invention. FIG. 12 is a view showing a part of a cross section of a semiconductor wafer made of a crystal such as silicon, and schematically shows defects, scratches, holes, etc. existing in the front surface, back surface and bulk of the wafer.
11 discriminates foreign matter adhering to the surface of an inspection object (sample, for example, FIG. 12) and holes opened from the surface of the sample toward the inside, and inspects the positions and distribution of the holes. Included in the device to do. The apparatus shown in FIG. 11 is provided with three cameras (camera 1, camera 2, camera 3). A part of the camera is shown in a sectional view in FIG. This is to detect flaws such as holes and dents, foreign matters, and the like. In FIG. 11, wiring such as an autofocus unit, a stage control unit, a control PC, a display, and a cable connecting between them as shown in FIG. 1 or FIG. 6 is omitted.

  In FIG. 11, cameras 1 to 3 are high-resolution cameras having, for example, 2000 × 2000 pixels, and images of the sample obtained from the optical microscope are branched by mirrors 5 and 6 and half mirrors 7 and 8 and captured. . At this time, as shown in FIG. 12, for example, the imaging plane of each camera is such that the camera 1 is on the surface of the sample, the camera 2 is about 1/3 from the surface of the sample, and the camera 3 is on the surface of the sample. It is the position which entered in about 2/3. These positions can be set in advance or can be changed according to the type and thickness of the sample to be measured.

  The detection result of the through hole (through hole) shown in FIG. 12 is compared with the result of visual observation with reference to FIGS. FIG. 13 is a diagram showing a relationship between a semiconductor wafer (for example, a silicon wafer, a diameter of about 50 mm) as a sample and an evaluation range. Moreover, FIG. 14 is a figure which shows an example of the detection result of the through-hole obtained using the image processing method and apparatus of one Example of this invention about the evaluation range of the sample shown in FIG. Moreover, FIG. 15 is a figure which shows the result of having detected the through-hole visually in the same evaluation range of the same sample.

13 to 15, the field of view is about 1 mm × 1 mm (10x objective lens is used), the illumination method is transmitted illumination, the camera resolution used for imaging is 2000 × 2000 pixels, and the number of observation fields in the evaluation range Is about 1900 fields of view (confirmed by visual observation and recording images of all fields of view), and the evaluation range is about 15 × 15 fields of view (image processing simulation is performed as shown in FIG. 14). Further, in the image processing of FIG. 14, objects commonly detected in images focused on the surface and different inner layers (for example, the surface, A surface, and B surface in FIG. 12) were counted as through holes.
As a result, the through-hole detection rate could be increased to 95% or higher.
Further, in the course of image processing, it was possible to detect foreign matters on the wafer surface, scratches, bubbles in the wafer, defects, etc., as distinguished from through holes.

  When it is known in advance at which height of the sample there is an object to be inspected such as a foreign object, the identification method of the present invention is used to identify and identify the object and store the position coordinates of the object, Thereafter, using the inspection device or the measurement device that also serves as the identification device, it is possible to inspect or measure the identified or specified object. In addition, it is possible to easily perform inspection or measurement with another inspection device or assumed device based on data such as a position table that identifies the object by the identification device of the present invention.

The block diagram which shows the structure of the identification device of one Example of this invention. The figure for demonstrating an example of the principle of this invention. The figure for demonstrating an example of the principle of this invention. The figure for demonstrating an example of the principle of this invention. The flowchart which shows the processing operation example of one Example of this invention. The block diagram which shows the structure of the identification device of one Example of this invention. The figure for demonstrating an example of the principle of this invention. The flowchart which shows the processing operation example of one Example of this invention. The figure for demonstrating the principle of one Example of this invention. The figure for demonstrating an example of the principle of this invention. The block diagram which shows the structure of the identification device of one Example of this invention. The figure which shows a part of cross section of a semiconductor wafer. The figure which shows the relationship between a sample and an evaluation range. The figure which shows an example of the detection result of the through-hole obtained using the image processing method and apparatus of one Example of this invention. The figure which shows the result of having detected the through-hole visually.

Explanation of symbols

  101: Microscope, 102: Revolver, 103: Autofocus optical unit, 104: Camera A, 105: Camera B, 106: Sample, 107: X axis stage, 108: Y axis stage, 109: Z axis stage, 110: Stage Control unit, 111: personal computer for control, 112: position control board, 113: image input board, 116: reflected illumination light, 117, 118, 119: half mirror, 120, 121: optical image, 122: laser light, 201 , 202: Hole image, 203: Foreign object image, 204: Luminance profile, 301, 302: Hole image, 303: Foreign object image, 304: Luminance profile, 701, 702: Internal foreign object, 703: Surface foreign object, 704 : Camera focus surface, 705: Pair Lens, 706: eyepiece, 707: camera imaging plane, 708: optical axis.

Claims (2)

Using a microscope device and an imaging device, obtain a reference image at the focal position that serves as a reference for the inspection object, obtain images of different focal positions at at least one focal position different from the focal position, and compare the obtained images Then, from the comparison result, a foreign matter identification method characterized by identifying foreign matter above and below the reference focal position. In a foreign object identification apparatus comprising a microscope apparatus having a stage on which an inspection object is placed, an imaging apparatus that captures an enlarged image of the inspection object magnified by the microscope apparatus, and a control apparatus that controls the stage,
In order to obtain at least one image at a focal position different from the reference focal position, the microscope apparatus focuses on a position different from the imaging apparatus that focuses on the surface of the inspection object. A second imaging device,
The imaging device acquires image information focused on the surface of the inspection object, and the second imaging device acquires image information whose focus is changed to a position different from the surface, and the image information defocused. A foreign substance identification device method characterized in that a differential component of the first image information is obtained, a portion having a larger differential value is recognized, and a portion in the former image information is identified from a portion having a recognized differential value increased.