JP2012181135A - Internal defect inspection device and internal defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal defect inspection device and a method for the same which can detect a defect having a smaller size than resolution and allows the defect to be detected in a short inspection period with a simpler configuration.SOLUTION: An internal defect inspection device Da of the present invention comprises: a light source section 1 to emit illumination light having a wavelength capable of penetrating a physical body SM of an inspection object; an illumination optical system 2 to irradiate the physical body SM of the inspection object with the illumination light emitted from the light source section 1; an imaging optical system 3a to form an optical image of the physical body SM of the inspection object; an imaging element 4a and an image processing section 71a to generate an image signal of the optical image through a photoelectric conversion of the optical image formed by the imaging optical system 3a; and an output section 6 to provide the physical body SM of the inspection object based on the generated image signal of the optical image. Also, the illumination optical system 2 and the imaging optical system 3a form a dark field optical system.

Description

  The present invention relates to an internal defect inspection apparatus and an internal defect inspection method for detecting a defect occurring inside an object to be inspected using a dark field optical system.

  With the development of electronics, various electronic components have been developed and manufactured. This electronic component is often realized as an integrated circuit such as an LSI or an IC because of demands for miniaturization, high speed, and low power consumption. The integrated circuit is manufactured using a semiconductor wafer, and the semiconductor wafer is manufactured by slicing an ingot. In addition, the development of solar cells (PV) is also progressing due to the recent demand for environmental measures. This solar cell is manufactured by slicing an ingot or a rectangular brick cut from the ingot or a brick manufactured directly.

  This ingot is manufactured by growing from a raw material melt. For example, a single crystal silicon ingot is manufactured by a so-called Czochralski method (Czochralski method) or a floating zone method (Floating Zone method). In addition, the solar cell does not require a purity as high as a semiconductor grade (purity of 11N or higher) and may be as high as 7N (solar cell grade). Therefore, ingots and bricks for solar cells require a semiconductor grade purification process. Manufactured by a simple method or a method of melting and solidifying the scrap material generated in the processing process of semiconductor grade silicon into a rectangular crucible. In this way, the manufacturing process of ingots and bricks includes the process of solidifying from the melt, so there is a defect called, for example, a substantially spherical void (void) inside the ingot or brick during the solidification process. May occur.

  Ingots and bricks containing such defects, or semiconductor wafers and solar cell wafers sliced from them become defective products, and it is required to detect the defects.

  An inspection apparatus for inspecting such a defect is disclosed in Patent Document 1, for example. This silicon wafer crystal defect inspection apparatus disclosed in Patent Document 1 irradiates a silicon wafer with infrared rays and inspects the silicon wafer for crystal defects from an image obtained by imaging the infrared rays transmitted through the silicon wafer. A crystal defect inspection apparatus according to claim 1, wherein a low-magnification objective lens that acquires a low-magnification inspection image having a fixed visual field area on the silicon wafer, and the position of the crystal defect is confirmed by performing image processing on the low-magnification inspection image and Position confirmation means for storing, a position of the confirmed crystal defect in a fixed visual field region, a high magnification objective lens for acquiring a high magnification inspection image of the visual field region, and the high magnification inspection image The shape of the crystal defect is obtained based on the shape information, and the crystal defect is detected by the shape information of the crystal defect in a circular shape or an irregular shape other than a circular shape. And a determining means for determining de or particles.

JP 2007-258555 A

  By the way, in the silicon wafer crystal defect inspection apparatus disclosed in Patent Document 1, since the bright field optical system is employed, the defect portion is imaged as a dark portion. For this reason, the size of the detectable defect (dark part) depends on the resolution of the camera device that images the object to be inspected, and is equivalent to the resolution determined from the optical magnification of the imaging optical system and the pixel size of the imaging element. It becomes the order of. Therefore, in a bright field optical system, it is difficult to detect a defect smaller than the order.

  In addition, the silicon wafer crystal defect inspection apparatus disclosed in Patent Document 1 uses a low-magnification objective lens and a high-magnification objective lens in order to increase the optical magnification and the resolution. More specifically, a defect position is first identified by imaging with a low-magnification objective lens, and the defect is detected by imaging the identified position with a high-magnification objective lens. Therefore, the silicon wafer crystal defect inspection apparatus disclosed in Patent Document 1 requires a low-magnification objective lens and a high-magnification objective lens, and also requires switching between these objective lenses. End up. In addition, the silicon wafer crystal defect inspection apparatus disclosed in Patent Document 1 processes an image captured by a low-magnification objective lens and processes an image captured by a high-magnification objective lens, and therefore requires a long inspection time. End up. In particular, let's detect the defect in the production line and eliminate the defective product in order to reduce the waste of the processing process of processing the defective product and manufacturing the defective final product and the defect of the final product. In this case, shortening the inspection time is important.

  The present invention has been made in view of the above circumstances, and its object is to detect defects having a size smaller than the resolution, and to detect defects with a simpler configuration and in a shorter inspection time. It is to provide an internal defect inspection apparatus and an internal defect inspection method capable of performing the above.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, an internal defect inspection apparatus according to an aspect of the present invention includes a light source unit that emits illumination light having a wavelength that can pass through an object to be inspected, and the illumination light emitted from the light source unit as the object to be inspected. An illumination optical system that irradiates the image, an imaging optical system that forms an optical image of the object to be inspected, and an image signal of the optical image is generated by photoelectrically converting the optical image formed by the imaging optical system An imaging unit; and a presentation unit that presents a defect inside the object to be inspected based on an image signal of the optical image generated by the imaging unit. The illumination optical system and the imaging optical system are dark A field optical system is formed.

  In the internal defect inspection method according to another aspect of the present invention, the inspection target object is irradiated with illumination light having a wavelength capable of transmitting the inspection target object by a predetermined illumination optical system. Is formed by a predetermined imaging optical system that forms a dark field optical system with the predetermined illumination optical system, and the optical image formed by the imaging optical system is photoelectrically converted to convert the optical image An image signal is generated, and a defect in the object to be inspected is presented based on the generated image signal of the optical image.

  In the internal defect inspection apparatus and the internal defect inspection method configured as described above, a dark field optical system is used. In the dark field optical system, if there is a defect, the illumination light is scattered by the defect, and the scattered light is imaged by the imaging unit. Therefore, in the dark field optical system, the defect is observed as a bright spot. For this reason, if a bright spot smaller than the pixel size of the image sensor is received by the pixel (if the light of the bright spot illuminates a part of the pixel of the image sensor without illuminating the entire pixel surface of the image sensor), the pixel Thus, the light at the bright spot is photoelectrically converted and a signal is output from the pixel. For this reason, the internal defect inspection apparatus and internal defect inspection method using such a dark field optical system can detect defects having a size smaller than the resolution. The internal defect inspection apparatus and the internal defect inspection method using such a dark field optical system increase the optical magnification as described in the background art and increase the resolution by using a low-magnification objective lens and a high-magnification lens. Since it is not necessary to use an objective lens, it is possible to detect a defect with a simpler configuration and a shorter inspection time.

  In another aspect, in the above-described internal defect inspection apparatus, the imaging optical system includes a plurality of optical images of the object to be inspected in a plurality of different directions, and the imaging unit includes a plurality of imaging units. The plurality of imaging optical systems are provided corresponding to each of the imaging optical systems.

  In the internal defect inspection apparatus having such a configuration, optical images of an object to be inspected are formed in a plurality of directions different from each other by a plurality of imaging optical systems. Usually, the defect appears in the plurality of images, while noise or the like hardly appears in all the plurality of images. For this reason, the internal defect inspection apparatus having such a configuration compares the images of the plurality of optical images with each other so that the inspection target object and the imaging optical system It is possible to reduce the influence of noise such as scattering that occurs on the surface intersecting the optical axis of the imaging optical system.

  In another aspect, in the above-described internal defect inspection apparatus, the same refraction as the refractive index of the object to be inspected that covers the surface of the object to be inspected that intersects the optical axis of the imaging optical system. Or a liquid having a refractive index between the refractive index of the object to be inspected and the refractive index of the object to be inspected in the external atmosphere.

  In the internal defect inspection apparatus having such a configuration, the surface that intersects the optical axis of the imaging optical system in the inspection target object is a rough surface between the inspection target object and the imaging optical system. However, since the surface is covered with the liquid, scattering on the surface can be reduced. Even if scattering occurs on the surface, since the scattering is smaller than the scattering caused by the defect, it is possible to distinguish the scattering on the surface from the scattering on the defect, and the defect can be detected.

  In another aspect, in the above-described internal defect inspection apparatus, the depth of focus or the depth of field in the imaging optical system corresponds to the entire range of the illumination light irradiated by the illumination optical system. Features.

  The internal defect inspection apparatus having such a configuration can inspect the entire range of the illumination light irradiated by the illumination optical system at a time, and can shorten the inspection time.

  According to another aspect, in these above-described internal defect inspection apparatuses, the depth of focus or the depth of field in the imaging optical system corresponds to a part of the range of the illumination light irradiated by the illumination optical system. It is characterized by that.

  In the internal defect inspection apparatus having such a configuration, the detection range is limited to the range of the depth of focus or the depth of field in the imaging optical system. Therefore, when a defect is detected, the defect in the optical axis direction of the imaging optical system is detected. The position can be estimated.

  According to another aspect, the internal defect inspection apparatus further includes a distance changing mechanism that changes a distance between the object to be inspected and a focal plane of the imaging optical system.

  The internal defect inspection apparatus having such a configuration can scan the object to be inspected by the distance changing mechanism, and can inspect the entire object to be inspected.

  According to another aspect, in the above-described internal defect inspection apparatus, the illumination light is slit-shaped (sheet-shaped) light.

  In the internal defect inspection apparatus having such a configuration, since the detection range is limited to the slit-shaped (sheet-shaped) illumination light range, the position of the defect can be estimated when the defect is detected.

  In another aspect, the above-described internal defect inspection apparatus further includes an irradiation position moving mechanism that moves the irradiation position of the slit-shaped light.

  The internal defect inspection apparatus having such a configuration can scan the object to be inspected by the irradiation position moving mechanism, and can inspect the entire object to be inspected.

  According to another aspect, in the above-described internal defect inspection apparatus, the illumination optical system irradiates the object to be inspected with the illumination light emitted from the light source unit in a plurality of different directions. It is characterized by being plural.

  Since the internal defect inspection apparatus having such a configuration irradiates the object to be inspected with each of a plurality of illumination lights, the brightness of the scattered light increases, so that the detection sensitivity can be improved, and the defects can be improved. Can be detected.

  INDUSTRIAL APPLICABILITY The internal defect inspection apparatus and the internal defect inspection method according to the present invention can detect defects having a size smaller than the resolution, and can detect defects with a simpler configuration and in a shorter inspection time.

It is a figure which shows the structure of the internal defect inspection apparatus in 1st Embodiment. It is a schematic diagram for demonstrating the inspection image obtained by the internal defect inspection apparatus of 1st Embodiment shown in FIG. It is a figure which shows the structure of the internal defect inspection apparatus in 2nd Embodiment. It is a schematic diagram for demonstrating the inspection image obtained by the internal defect inspection apparatus of 2nd Embodiment shown in FIG. It is a figure which shows the structure of the internal defect inspection apparatus in 3rd Embodiment.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. In the present specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

  The internal defect inspection apparatus D in the present embodiment is an apparatus that detects defects present in an object to be inspected. The internal defect inspection apparatus D includes a light source unit that emits illumination light having a wavelength that can pass through an object to be inspected, and an illumination optical system that irradiates the object to be inspected with the illumination light emitted from the light source unit. An imaging optical system that forms an optical image of the object to be inspected, an imaging unit that generates an image signal of the optical image by photoelectrically converting the optical image formed by the imaging optical system, and the imaging unit A presentation unit that presents a defect inside the object to be inspected based on the image signal of the optical image generated in step (i), and the illumination optical system and the imaging optical system form a dark field optical system. It is what. The object to be inspected may be any solid object, such as a silicon brick. And since the internal defect inspection apparatus D of this embodiment detects the said defect with a dark field optical system, since it can detect the interface which scatters illumination light which exists in the object of inspection object, the said defect Has such an interface. The defect is, for example, a void such as a void that exists in an object to be inspected such a solid object. As described above, the internal defect inspection apparatus D of this embodiment and the internal defect inspection method mounted thereon can detect defects having a size smaller than the resolution because the dark field optical system is used, and Since it is not necessary to use a low-magnification objective lens and a high-magnification objective lens in order to increase the optical magnification and increase the resolution as described in the background art, defects can be eliminated with a simpler configuration and a shorter inspection time. Can be detected. One embodiment of the internal defect inspection apparatus D and the internal defect inspection method mounted thereon will be described in detail below as first to third embodiments.

(First embodiment)
First, the configuration of the internal defect inspection apparatus Da in the first embodiment will be described. FIG. 1 is a diagram showing a configuration of an internal defect inspection apparatus in the first embodiment. In FIG. 1, an internal defect inspection apparatus Da according to the first embodiment includes a light source unit 1, an illumination optical system 2, an imaging optical system 3a, an imaging element 4a, an input unit 5, an output unit 6, and arithmetic control. A unit 7a and a storage unit 8 are provided.

  The light source unit 1 is an apparatus for emitting illumination light having a wavelength that can pass through the object SM to be inspected according to the control of the arithmetic control unit 7a. The illumination light only needs to be able to pass through the object SM to be inspected, and its intensity may be attenuated while propagating through the object SM to be inspected. The illumination light is appropriately selected according to the object SM to be inspected. For example, when the object SM to be inspected is silicon (Si), the illumination light is preferably infrared. For this reason, in this case, the light source unit 1 includes an infrared light source device that emits light having a predetermined wavelength in the infrared region. For example, when the object SM to be inspected is glass, the illumination light is preferably visible light. For this reason, in this case, the light source unit 1 includes a visible light source device that emits light having a predetermined wavelength in the visible light region. For example, when light emitted from a light source such as a lamp includes an unnecessary wavelength component as illumination light, the light source unit 1 further includes an optical filter that blocks the unnecessary wavelength component. May be. The illumination light emitted from the light source unit 1 enters the illumination optical system 2.

  The illumination optical system 2 irradiates the object SM to be inspected with the illumination light emitted from the light source unit 1. For example, in this embodiment, the illumination optical system 2 includes a collimator lens that emits illumination light emitted from the light source unit 1 as a substantially parallel light beam in order to illuminate the object SM to be inspected with substantially uniform light intensity. It is prepared for. In the example shown in FIG. 1, the illumination light is made into a substantially parallel light beam by the illumination optical system 2 and is irradiated onto the object SM to be inspected with the substantially parallel light beam, but the illumination light is a parallel light beam. There may not be (it may be a non-parallel light beam). The illumination light emitted from the illumination optical system 2 is irradiated onto a predetermined surface of the object to be inspected.

  The imaging optical system 3a forms an optical image of the object SM to be inspected on the light receiving surface of the imaging element 4a. The light beam from the object SM to be inspected is imaged on the light receiving surface of the image sensor 4a by the image pickup optical system 3a, and becomes an optical image of the object SM to be inspected. The depth of focus or the depth of field in the imaging optical system 3a may correspond to, for example, the entire range La of illumination light irradiated by the illumination optical system 2. In such a configuration, since the entire range of illumination light irradiated by the illumination optical system 2 can be inspected at a time, the inspection time can be shortened. For example, the depth of focus or the depth of field in the imaging optical system 3a may correspond to a part Lb of the range of illumination light irradiated by the illumination optical system 2. In such a configuration, since the detection range is limited to the range of the depth of focus or the depth of field in the imaging optical system 3a, when a defect is detected, the position of the defect in the optical axis direction of the imaging optical system 3a is estimated. can do.

  In general, when focusing on a certain distance, light emitted from one point on the optical axis at that distance passes through a lens and forms an image on one point on the optical axis of the focal plane. There is a range that appears to be in focus before and after the focal plane, and this range is the depth of focus. Also, when focusing on a certain distance, not only the subject at that distance is clearly visible, but also before and after the subject is clearly visible in a certain range. The depth of field is the depth before and after the subject that is clearly visible.

  In the present embodiment, the imaging optical system 3a is configured such that the depth of focus or the depth of field is a part Lb of the range of illumination light irradiated by the illumination optical system 2. In this case, the internal defect inspection apparatus Da according to the present embodiment scans the object SM to be inspected with the object SM to be inspected according to the control of the arithmetic control unit 7a in order to scan the object SM in the optical axis direction of the imaging optical system. A distance changing mechanism (not shown) for changing the distance from the focal plane of the imaging optical system 3a is further provided. Such a distance changing mechanism is a mechanism that moves the imaging optical system 3a in the optical axis direction, for example, like a focus mechanism. Further, for example, the distance changing mechanism includes a stage device (for example, an XY stage) including a mounting table for mounting the object SM to be inspected and a moving mechanism for moving the mounting table in the optical axis direction of the imaging optical system 3a. Device). When the imaging optical system 3a is configured so that the depth of focus or the depth of field is a part Lb of the range of illumination light irradiated by the illumination optical system 2, such a distance changing mechanism is further provided. Thus, the internal defect inspection apparatus Da having such a configuration can inspect the entire object SM to be inspected, and when a defect is detected, the position of the defect in the optical axis direction of the imaging optical system 3a is also determined. Can be estimated.

  In FIG. 1, the image sensor 4a is connected to the arithmetic control unit 7a, and generates an image signal of the optical image by photoelectrically converting the optical image of the object SM to be inspected formed by the imaging optical system 3a. Is. The imaging device 4a is configured to include, for example, a CCD image sensor, a CMOS image sensor, or the like that includes a plurality of photoelectric conversion elements as a plurality of pixels arranged in a two-dimensional array. The image signal of the optical image generated by the image sensor 4a is output to the arithmetic control unit 7a.

  The input unit 5 is connected to the arithmetic control unit 7a and is a device for inputting commands (commands), data, and the like from the outside to the internal defect inspection device Da, and is, for example, a touch panel or a keyboard. The output unit 6 is connected to the calculation control unit 7a and outputs a command and data input from the input unit 5, a calculation result of the calculation control unit 7a (for example, an image of the optical image, a detected internal defect, and the like). For example, a display such as a CRT display, LCD (liquid crystal display), or organic EL display, and a printing device such as a printer.

  The storage unit 8 is connected to the arithmetic control unit 7a, and detects internal defects based on the imaging results of the image sensor 4a and control programs for controlling each unit of the internal defect inspection apparatus Da according to the function. ROM (Read Only Memory) which is a non-volatile storage element that stores various predetermined programs such as programs and various predetermined data such as data necessary for execution of the predetermined programs, and is rewritable EEPROM (Electrically Erasable Programmable Read Only Memory) which is a non-volatile memory element, RAM (Random Access Memory) which is a so-called CPU working memory to store data generated during execution of the predetermined program, and the like These peripheral circuits are provided.

  The arithmetic control unit 7a is a circuit that controls each part of the internal defect inspection apparatus Da according to the function, and obtains the internal defect V in the object SM to be inspected based on the detection result of the image sensor 4a. . The arithmetic control unit 7a includes, for example, a CPU (Central Processing Unit) that performs predetermined control processing and predetermined arithmetic processing by reading and executing a predetermined program stored in the storage unit 8, and its peripheral circuit. Composed. The arithmetic control unit 7a functionally includes an image processing unit 71a and a defect detection unit 72a.

  The image processing unit 71a generates an image of the object SM to be inspected based on the image signal of the image sensor 4a. More specifically, the image processing unit 71a performs amplification processing, digital conversion processing, and the like, and determines an appropriate black level, γ correction, white balance adjustment (WB adjustment), contour correction, and color for the entire image. By performing known image processing such as unevenness correction, an image of the object SM to be inspected is generated from the image signal of the image sensor 4a.

  The defect detection unit 72a detects the defect V inside the inspection target object SM based on the image (image signal) of the inspection target object SM generated by the image processing unit 71a. In order to detect the defect V by visual observation, an image of the object SM to be inspected generated by the image processing unit 71a is output to the output unit 6, so that the inside of the object to be inspected is based on the image signal of the optical image. Although the defect V may be presented, the internal defect inspection apparatus Da of the present embodiment further includes a defect detection unit 72a, and the defect detection unit 72a detects the defect V, and the detection result is also output to the output unit 6. It is configured to output. Note that only the image of the object SM to be inspected is presented in the output unit 6 and the detection result need not be presented, and only the detection result is presented without presenting the image of the object SM to be inspected. May be.

  The imaging element 4a and the image processing unit 71a correspond to an example of an imaging unit that generates an image signal of the optical image by photoelectrically converting the optical image of the object SM to be inspected formed by the imaging optical system 3. To do. Further, instead of the image sensor 4a, a camera device including the image sensor 4a and the image processing unit 71a may be used. In this case, the arithmetic control unit 7a receives the object SM to be inspected from the camera device. The image signal of the optical image is input, and the image signal of the optical image is processed by the defect detection unit 72a.

  In the internal defect inspection apparatus Da of this embodiment, the illumination optical system 2 and the imaging optical system 3a form a dark field optical system. When the illumination optical system 2 illuminates the object SM to be inspected, the dark-field optical system is configured so that the imaging optical system 3a excludes the transmitted light direction of illumination light and the specular reflection direction of the illumination light from the direction other than the inspection object This is an optical system for observing SM. In the dark field optical system, the scattered component of the illumination light is captured and observed.

  More specifically, in this embodiment, for example, the illumination optical system 2 and the imaging optical system 3a are arranged so that the optical axis of the illumination optical system 2 and the optical axis of the imaging optical system 3a are orthogonal to each other. ing. That is, the imaging optical system 3a observes the inspection target object SM from the side surface in the traveling direction of the illumination light illuminated on the inspection target object SM by the illumination optical system 2, and captures the light from the inspection target object SM. ing.

  Next, the operation of the internal defect inspection apparatus Da in the first embodiment will be described. FIG. 2 is a schematic diagram for explaining an inspection image obtained by the internal defect inspection apparatus according to the first embodiment shown in FIG.

  When the inspection is started, the internal defect inspection apparatus Da operates the distance changing mechanism (not shown) under the control of the arithmetic control unit 7a, so that the object SM to be inspected and the focal plane of the imaging optical system 3a are operated. The distance is changed to a predetermined distance. For example, when the depth of focus of the imaging optical system 3a is configured to correspond to a part Lb of the range of illumination light irradiated by the illumination optical system 2, it is virtually set in the object SM to be inspected. The object SM (that is, the predetermined object surface) to be inspected and the focal plane of the imaging optical system 3a so that the light from the predetermined object surface is focused on the light receiving surface of the image sensor 4a by the imaging optical system 3a. The distance between is changed by the distance changing mechanism. Further, for example, when the depth of field of the imaging optical system 3a is configured to correspond to a part Lb of the range of illumination light irradiated by the illumination optical system 2, a virtual image is included in the object SM to be inspected. The object SM (that is, the predetermined object surface) to be inspected and the imaging optical system 3a so that the light from the predetermined object surface that is set in focus is focused on the light receiving surface of the image sensor 4a by the imaging optical system 3a. The distance to the focal plane is changed by the distance changing mechanism. The predetermined object plane is, for example, a plane that is parallel to the optical axis of the illumination optical system 2 and orthogonal to the optical axis of the imaging optical system 3a.

  Subsequently, the internal defect inspection apparatus Da irradiates the light source unit 1 on the object SM to be inspected by operating the light source unit 1 under the control of the arithmetic control unit 7a.

  As a result, the light source unit 1 emits illumination light. The illumination light emitted from the light source unit 1 is incident on the object SM to be inspected via the illumination optical system 2. In the example shown in FIG. 1, the illumination light emitted from the light source unit 1 is incident on the illumination optical system 2, and is emitted from the illumination optical system 2 as a substantially parallel light beam by the illumination optical system 2. The bundle of illumination light is incident on a substantially planar upper surface (incident surface) of the object SM to be inspected.

  The illumination light incident on the object SM to be inspected propagates through the object SM to be inspected, travels, and is emitted from a substantially flat lower surface (exit surface) facing the incident surface. Here, if a defect V such as a substantially spherical void exists in the inspection object SM, the illumination light propagating through the inspection object SM is caused by the interface of the defect V. Scattered. The defect V does not need to be substantially spherical, and may be an arbitrary shape such as an irregular shape. Part of this scattered light is incident on the imaging optical system 3a, and an optical image of the defect V is formed on the light receiving surface of the imaging element 4a by the imaging optical system 3a. The optical image of the defect V is photoelectrically converted by the image sensor 4a, and an image signal corresponding to the optical image of the defect V is generated. This image signal is input from the image sensor 4a to the arithmetic control unit 7a.

  When an image signal is input from the image sensor 4a to the arithmetic control unit 7a, the image processing unit 71a generates an image of the object SM to be inspected based on the image signal of the image sensor 4a. The image processing unit 71a outputs an image of the object SM to be inspected to the output unit 6 and notifies the defect detection unit 72a. For example, an image of the object SM to be inspected as shown in FIG. The defect V may be recognized and detected by the operator visually checking the image of the object SM to be inspected presented on the output unit 6.

  On the other hand, the defect detection unit 72a determines whether or not there is a pixel having a luminance level equal to or higher than a predetermined luminance level in the image of the object SM to be inspected, and sets the luminance level equal to or higher than the predetermined luminance level. If there is a pixel having the pixel, it is determined that the pixel corresponds to the defect V, and coordinates on the predetermined object plane corresponding to the pixel are calculated. Then, the defect detection unit 72a outputs the detected defect V and the coordinates of the defect V to the output unit 6. The output unit 6 presents that the defect V has been detected and the coordinates of the defect V.

  When the inspection on the predetermined object surface is completed, the predetermined object surface is shifted by the distance changing mechanism (not shown), and the inspection is performed by the same operation. This is repeated and the entire object SM to be inspected is scanned.

  By operating in this way, the internal defect inspection apparatus Da of the present embodiment can detect the defect V present in the object SM to be inspected.

  And in the internal defect inspection apparatus Da of this embodiment and the internal defect inspection method mounted in this, as above-mentioned, the illumination optical system 2 and the imaging optical system 3a are comprised with the dark field optical system. In this dark field optical system, if there is a defect V, the illumination light is scattered by the defect V, and the scattered light is imaged by the imaging element 4a via the imaging optical system 3a. Therefore, in the dark field optical system, the defect V is observed as a bright spot. For this reason, even if a bright spot smaller than the pixel size of the image sensor 4a is received by the pixel (if the light of the bright spot illuminates a part of the pixel of the image sensor 4a without illuminating the entire pixel surface of the image sensor 4a). The light of the bright spot is photoelectrically converted by the pixel and a signal is output from the pixel. Therefore, the internal defect inspection apparatus Da and the internal defect inspection method using such a dark field optical system can detect the defect V having a size smaller than the resolution. The internal defect inspection apparatus Da and the internal defect inspection method using such a dark field optical system have a low magnification objective lens and a high magnification in order to increase the optical magnification and increase the resolution as described in the background art. Since it is not necessary to use a magnification objective lens, it is possible to detect a defect with a simpler configuration and a shorter inspection time. Further, even when noise occurs, the noise is superimposed on the background of a predetermined luminance level in the bright field optical system, but the noise is superimposed on the background of the luminance level 0 in the dark field optical system. Therefore, it is considered that the dark field optical system has higher noise resistance than the bright field optical system, and the SN is improved.

  Next, another embodiment will be described.

(Second Embodiment)
FIG. 3 is a diagram showing the configuration of the internal defect inspection apparatus in the second embodiment. FIG. 4 is a schematic diagram for explaining an inspection image obtained by the internal defect inspection apparatus according to the second embodiment shown in FIG. FIG. 4A shows a first inspection image obtained by the first imaging optical system 3b-1, the first imaging element 4b-1, and the first image processing unit 71b-1, and FIG. 2 shows a second inspection image obtained by the two imaging optical system 3b-2, the second imaging element 4b-2, and the second image processing unit 71b-2.

  Although the internal defect inspection apparatus Da of the first embodiment images the object SM to be inspected from one direction, the internal defect inspection apparatus Db of the second embodiment images the object SM to be inspected from a plurality of different directions. To do. For this reason, the imaging optical system is a plurality of optical images of the object SM to be inspected in a plurality of different directions, and the imaging unit is provided corresponding to each of the plurality of imaging optical systems. It is more than one.

  For example, as shown in FIG. 3, an internal defect inspection apparatus Db that images an object SM to be inspected from two different directions, a light source unit 1, an illumination optical system 2, an imaging optical system 3b, and an imaging element 4b. , An input unit 5, an output unit 6, a calculation control unit 7 b, and a storage unit 8.

  The light source unit 1, the illumination optical system 2, the input unit 5, the output unit 6, and the storage unit 8 in the internal defect inspection apparatus Db of the second embodiment are the light source unit 1 and illumination in the internal defect inspection apparatus Da of the first embodiment. Since the optical system 2, the input unit 5, the output unit 6, and the storage unit 8 are similar to each other, the description thereof is omitted.

  The imaging optical system 3b forms an optical image of the object SM to be inspected on each light receiving surface of the plurality of imaging elements 4b. In the example shown in FIG. 3, as described above, the imaging optical system 3b includes the first imaging optical system 3b-1 and the second imaging optical system 3b-2. The imaging element 4b is a plurality provided corresponding to each of the plurality of imaging optical systems 3b, each connected to the arithmetic control unit 7b, and the object SM to be inspected formed by each imaging optical system 3b. Each of the optical images is photoelectrically converted to generate each image signal of the optical image. In the example shown in FIG. 3, the image sensor 4 b is provided corresponding to the first image sensor 4 b-1 provided corresponding to the first image pickup optical system 3 b-1 and the second image pickup optical system 3 b-2. The first image sensor 4b-2. The light beam from the object SM to be inspected is imaged on the light receiving surface of the first image sensor 4b-1 by the first image pickup optical system 3b-1, and becomes the first optical image of the object SM to be inspected. In addition, the light beam from the object SM to be inspected is imaged on the light receiving surface of the second image sensor 4b-2 by the second imaging optical system 3b-2 to become a second optical image of the object SM to be inspected.

  In addition, as described in the first embodiment, each depth of focus or each depth of field in the imaging optical system 3b corresponds to, for example, the entire range La of illumination light emitted by the illumination optical system 2. For example, it may correspond to a part Lb of the range of illumination light irradiated by the illumination optical system 2. In this case, the internal defect inspection apparatus Db of the present embodiment further includes a plurality of unillustrated distance changing mechanisms that change the distance between the object SM to be inspected and the focal plane of the imaging optical system 3b. Also good.

  The plurality of imaging optical systems 3b form a dark field optical system together with the imaging optical system 3a, and are arranged so as to form optical images of the object SM to be inspected in a plurality of different directions. Yes. In the example shown in FIG. 3, the first and second imaging optical systems 3b-1 and 3b-2 are arranged so as to face each other. More specifically, in the present embodiment, for example, the illumination optical system 2 and the first imaging optical system are arranged such that the optical axis of the illumination optical system 2 and the optical axis of the first imaging optical system 3b-1 are orthogonal to each other. 3b-1, the illumination optical system 2 and the second imaging optical system 3b-2 are arranged so that the optical axis of the illumination optical system 2 and the optical axis of the second imaging optical system 3b-2 are orthogonal to each other. Is arranged. That is, each of the first and second imaging optical systems 3b-1, 3b-2 moves the inspection object SM from the side surface in the traveling direction of the illumination light illuminated on the inspection object SM by the illumination optical system 2. Observe and capture light from the object SM to be inspected. Then, the first imaging optical system 3b-1 and the second imaging optical system 3b-2 are arranged so that the optical axis of the first imaging optical system 3b-1 and the optical axis of the second imaging optical system 3b-2 coincide with each other. Is arranged. That is, the first imaging optical system 3b-1 observes the object SM to be inspected from the first side surface, captures light from the object SM to be inspected, and the second imaging optical system 3b-2 has the first side surface. The object SM to be inspected is observed from the second side opposite to the light and the light from the object SM to be inspected is captured.

  The arithmetic control unit 7b is a circuit that controls each part of the internal defect inspection apparatus Da according to the function, and obtains the internal defect V in the object SM to be inspected based on the detection result of the image sensor 4b. . The arithmetic control unit 7b includes, for example, a CPU (Central Processing Unit) that performs predetermined control processing and predetermined arithmetic processing by reading and executing a predetermined program stored in the storage unit 8, and its peripheral circuit. Composed. The arithmetic control unit 7b functionally includes an image processing unit 71b and a defect detection unit 72b.

  The image processing unit 71b generates each image of the object SM to be inspected based on each image signal of the plurality of imaging elements 4b. More specifically, the image processing unit 71b is a plurality provided corresponding to each of the plurality of imaging elements 4b, and for each image signal of the plurality of imaging elements 4b, amplification processing, digital conversion processing, and the like. And performing known image processing such as determination of an appropriate black level, γ correction, white balance adjustment (WB adjustment), contour correction, and color unevenness correction for the entire image, and each of the plurality of image sensors 4b. Each image of the object SM to be inspected is generated from the image signal. In the example illustrated in FIG. 3, the image processing unit 71 b is provided corresponding to the first image processing unit 71 b-1 provided corresponding to the first image sensor 4 b-1 and the second image sensor 4 b-2. And a first image processing unit 71b-2.

  The defect detection unit 72b detects a defect V in the inspection target object SM based on each image (each image signal) of the inspection target object SM generated by the image processing unit 71b. In order to detect defects visually, each image of the object SM to be inspected generated by the plurality of image processing units 71b is output to the output unit 6, so that the object to be inspected based on the image signal of the optical image Although the defect V in the SM may be presented, the internal defect inspection apparatus Da of the present embodiment further includes a defect detection unit 72b, which detects the defect V and outputs the detection result. It is configured to output to the unit 6. Note that only the image of the object SM to be inspected is presented in the output unit 6 and the detection result need not be presented, and only the detection result is presented without presenting the image of the object SM to be inspected. May be.

  The plurality of image pickup devices 4b and the plurality of image processing units 71b generate respective image signals of the optical images by photoelectrically converting the respective optical images in the object SM to be inspected formed by the image pickup optical system 3. This corresponds to an example of an imaging unit. Further, instead of the plurality of image pickup devices 4b, a plurality of camera devices provided with the image pickup devices 4b and the image processing unit 71b may be used. In this case, the arithmetic control unit 7b includes the plurality of camera devices. Each image signal of the optical image of the object SM to be inspected is input, and each image signal of the optical image is processed by the defect detection unit 72b.

  The internal defect inspection apparatus Db of the second embodiment having such a configuration operates in the same manner as the internal defect inspection apparatus Da of the first embodiment, so that a plurality of optical images of the defect V are formed on a predetermined object surface. Each of the image pickup devices 4b performs photoelectric conversion, and each image signal corresponding to the optical image of the defect V is generated. Each of these image signals is input to the arithmetic control unit 7a from each of the plurality of imaging elements 4b. When each image signal is input from the plurality of image pickup devices 4b to the arithmetic control unit 7b, the plurality of image processing units 71b generate each image of the object SM to be inspected based on each image signal of the plurality of image pickup devices 4a. To do. The plurality of image processing units 71b output each image of the object SM to be inspected to the output unit 6 and notify the defect detection unit 72b. In the example shown in FIG. 3, the inspection target object observed from the first side surface of the inspection target object SM by the first imaging optical system 3b-1, the first imaging element 4b-1, and the first image processing unit 71b-1. The first image of SM is generated and observed from the second side surface of the object SM to be inspected by the second imaging optical system 3b-2, the second imaging element 4b-2, and the second image processing unit 71b-2. A second image of the object SM to be inspected is generated. For example, each image (first image and second image) of the object SM to be inspected as shown in FIGS. 4A and 4B is presented on the output unit 6. The defect V may be recognized and detected by an operator visually confirming each image of the inspection target object SM presented in the output unit 6.

  On the other hand, for example, for each image of the object SM to be inspected, the defect detection unit 72b determines whether there is a pixel having a luminance level equal to or higher than a predetermined luminance level in the image. If there is a pixel having a luminance level, it is determined that the pixel corresponds to the defect V, and coordinates on the predetermined object plane corresponding to the pixel are calculated. Then, the defect detection unit 72b outputs the detected defect V and the coordinates of the defect V to the output unit 6 for each image of the object SM to be inspected. The output unit 6 presents that the defect V has been detected and the coordinates of the defect V for each image of the object SM to be inspected. In this case, the defect detection unit 72b compares the coordinates of each defect V in each image of the object SM to be inspected, and if the coordinates match, the defect V of those coordinates is If it is determined that the defect is a true defect V and the coordinates do not match, the defect V of these coordinates may be determined as noise such as particles adhering to the surface of the object SM to be inspected. Good.

  Further, for example, the defect detection unit 72b adds each image of the inspection target object SM to each other to form an image of the inspection target object SM, and for this image, a pixel having a luminance level equal to or higher than a predetermined luminance level in the image. If there is a pixel having a luminance level equal to or higher than a predetermined luminance level, it is determined that the pixel corresponds to the defect V, and the predetermined object plane corresponding to the pixel is determined. The upper coordinates may be calculated. Then, the defect detection unit 72b outputs the detected defect V and the coordinates of the defect V to the output unit 6. The output unit 6 presents that the defect V has been detected and the coordinates of the defect V. In this case, the output unit 6 may be presented with an image of the inspection object SM obtained by adding the images of the inspection object SM to each other.

  When the inspection on the predetermined object surface is completed, the predetermined object surface is shifted by the distance changing mechanism (not shown), and the inspection is performed by the same operation. This is repeated and the entire object SM to be inspected is scanned.

  By operating in this way, the internal defect inspection apparatus Db of this embodiment can detect the defect V existing in the object SM to be inspected, and can detect the defect V having a size smaller than the resolution. In addition, the defect can be detected with a simpler configuration and a shorter inspection time.

  In the internal defect inspection apparatus Db of this embodiment, optical images of the object SM to be inspected are formed in a plurality of directions different from each other by the plurality of imaging optical systems 3b. Usually, the defect appears in the plurality of images, while noise or the like hardly appears in all the plurality of images. For this reason, the internal defect inspection apparatus Db having such a configuration compares the images of the plurality of optical images with each other, so that the inspection target object SM and the imaging optical system 3b can be compared with each other. It is possible to reduce the influence of noise such as scattering that occurs on the surface of the object SM that intersects the optical axis of the imaging optical system 3b.

  Next, another embodiment will be described.

(Third embodiment)
FIG. 5 is a diagram showing the configuration of the internal defect inspection apparatus in the third embodiment. The internal defect inspection apparatus Dc of the third embodiment is a surface that intersects the optical axis of the imaging optical systems 3a and 3b in the object SM to be inspected in the internal defect inspection apparatuses Da and Db of the first and second embodiments described above. It further comprises a liquid covering the top. For example, FIG. 5 shows an example of the internal defect inspection apparatus Dc of the third embodiment with respect to the internal defect inspection apparatus Da of the first embodiment. As shown in FIG. 5, the internal defect inspection apparatus Dc of the third embodiment with respect to the internal defect inspection apparatus Da of the first embodiment has a light source unit 1, an illumination optical system 2, an imaging optical system 3 a, and an imaging system. A liquid that includes an element 4a, an input unit 5, an output unit 6, an arithmetic control unit 7a, and a storage unit 8, and further covers a surface that intersects the optical axis of the imaging optical system 3a in the object SM to be inspected. 21 is provided. The light source unit 1, the illumination optical system 2, the imaging optical system 3a, the imaging element 4a, the input unit 5, the output unit 6, the calculation control unit 7a, and the storage unit 8 in the internal defect inspection apparatus Dc of the third embodiment are the first. Since it is the same as the light source unit 1, the illumination optical system 2, the imaging optical system 3a, the imaging element 4a, the input unit 5, the output unit 6, the arithmetic control unit 7a, and the storage unit 8 in the internal defect inspection apparatus Da of the embodiment, The description is omitted.

  Although not shown, the internal defect inspection apparatus Dc of the third embodiment with respect to the internal defect inspection apparatus Db of the second embodiment includes a light source unit 1, an illumination optical system 2, an imaging optical system 3b, and an imaging element 4b. And an input unit 5, an output unit 6, an arithmetic control unit 7b, and a storage unit 8, and further, a liquid 21 that covers the surface of the object SM to be inspected that intersects the optical axis of the imaging optical system 3b. It is to be prepared.

  The liquid 21 is a liquid having the same refractive index as that of the object to be inspected, or a refractive index between the refractive index of the object to be inspected SM and the refractive index in the external atmosphere of the object of inspection SM. It has a liquid. For example, the refractive index of silicon is about 3.5 in the near-infrared wavelength region, and the liquid 21 is, for example, high refractive index silicon oil or the like for the object SM to be inspected.

  The gravitational force acts in a direction (downward) from the imaging optical systems 3a, 3b toward the inspection target object SM with respect to a surface intersecting the optical axis of the imaging optical systems 3a, 3b in the inspection target object SM. When the internal defect inspection apparatus Dc of the third embodiment is configured, such a liquid 21 is formed on the surface intersecting with the optical axis of the imaging optical systems 3a and 3b in the object SM to be inspected due to the gravity. Retained. Alternatively, the internal defect inspection apparatus Dc of the third embodiment may include a holding member that holds the liquid 21 on the surface that intersects the optical axis of the imaging optical systems 3a and 3b in the object SM to be inspected. Such a holding member is, for example, a housing that accommodates the object SM to be inspected at a predetermined interval. The liquid 21 is filled in the gap at the predetermined interval that occurs after the object SM to be inspected is accommodated in the casing.

  The internal defect inspection apparatus Dc in the third embodiment having such a configuration is between the object SM to be inspected and the imaging optical system 3 (3a, 3b), and the imaging optical system 3 in the object SM to be inspected. Even if the surface intersecting the optical axis is a rough surface, the surface is covered with the liquid 21, so that scattering on the surface can be reduced. Even if scattering occurs on the surface, since the scattering is smaller than the scattering caused by the defect V, it is possible to distinguish the scattering from the surface and the scattering from the defect V, and the defect V can be detected. It becomes.

  In the internal defect inspection apparatus D in the first to third embodiments described above, the illumination optical system 2 and the imaging optical system 3 have the optical axis of the illumination optical system 2 and the optical axis of the imaging optical system 3 orthogonal to each other. However, it is not limited to this, and if it is a dark field optical system, the illumination optical system 2 and the imaging optical system 3a are the optical axis of the illumination optical system 2 and the imaging optical system 3a. You may arrange | position so that an optical axis may cross | intersect at another angle.

  Further, in the internal defect inspection apparatus D in the first to third embodiments described above, the imaging optical system 3 has a part of the range of the illumination light whose depth of focus or depth of field is irradiated by the illumination optical system 2. In combination with or instead of this (that is, the imaging optical system 3 has a range of the illumination light whose depth of focus or depth of field is irradiated by the illumination optical system 2. The illumination light may be slit-shaped (sheet-shaped) light.

  Even with such a configuration, the internal defect inspection apparatus D can estimate the position of the defect when the defect is detected because the detection range is limited to the slit-shaped (sheet-shaped) illumination light range. .

  In such a configuration, the internal defect inspection apparatus D may further include an irradiation position moving mechanism that moves the irradiation position of the slit-shaped light. Such an irradiation position moving mechanism is, for example, a mechanism that changes the optical axis direction of the illumination optical system, or a stage device such as an XY stage device.

  The internal defect inspection apparatus D having such a configuration can scan the inspection target object SM by the irradiation position moving mechanism, and can inspect the entire inspection target object SM.

  In the internal defect inspection apparatus D in the first to third embodiments described above, the illumination optical system 2 irradiates the object SM to be inspected with the illumination light emitted from the light source unit 1 in a plurality of different directions. There may be a plurality. Such an illumination optical system 2 distributes, for example, the illumination light emitted from one light source unit 1 into two, irradiates one illumination light from the upper surface of the object SM to be inspected, and the other illumination light. Is illuminated from the lower surface of the object SM to be inspected. Further, for example, there are two light source units 1, and such an illumination optical system 2 irradiates illumination light emitted from one light source unit 1 from the upper surface of the object SM to be inspected, and the other light source unit. The illumination light emitted from 1 is illuminated from the lower surface of the object SM to be inspected. In this example, the two directions are up and down, but the other illumination optical system 2 may be configured to illuminate the object SM to be inspected from the side surface orthogonal to the optical axis of one illumination optical system 2. Alternatively, the illumination optical system 2 may illuminate the object SM to be inspected from other directions such as three directions or four directions.

  Since the internal defect inspection apparatus D having such a configuration irradiates the object SM to be inspected with each of the plurality of illumination lights, the brightness of the scattered light increases, so that the detection sensitivity can be improved, and the defect can be detected. Can be detected more.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

Da, Db, Dc Internal defect inspection apparatus 1 Light source part 2 Illumination optical system 3a, 3b Imaging optical system 4a, 4b Imaging element 6 Output part 7a, 7b Calculation control part 71a, 71b Image processing part 72a, 72b Defect detection part

Claims (10)

A light source that emits illumination light having a wavelength that can pass through the object to be inspected;
An illumination optical system that irradiates the object to be inspected with the illumination light emitted from the light source unit;
An imaging optical system for forming an optical image of the object to be inspected;
An imaging unit that generates an image signal of the optical image by photoelectrically converting the optical image formed by the imaging optical system;
A presentation unit that presents a defect inside the object to be inspected based on an image signal of the optical image generated by the imaging unit;
The internal defect inspection apparatus, wherein the illumination optical system and the imaging optical system form a dark field optical system. The imaging optical systems are a plurality of optical images of the object to be inspected in a plurality of directions different from each other,
The internal defect inspection apparatus according to claim 1, wherein the imaging unit is a plurality provided corresponding to each of the plurality of imaging optical systems. A liquid having the same refractive index as the refractive index of the object to be inspected, which covers the surface intersecting the optical axis of the imaging optical system in the object to be inspected, or the refractive index of the object to be inspected and the The internal defect inspection apparatus according to claim 1, further comprising a liquid having a refractive index between the refractive index of an object to be inspected and an external atmosphere. The depth of focus or the depth of field in the imaging optical system corresponds to the entire range of the illumination light irradiated by the illumination optical system. Internal defect inspection equipment. The depth of focus or the depth of field in the imaging optical system corresponds to a part of the range of the illumination light irradiated by the illumination optical system. The internal defect inspection device described in 1. The internal defect inspection apparatus according to claim 5, further comprising a distance changing mechanism that changes a distance between the object to be inspected and a focal plane of the imaging optical system. The internal defect inspection apparatus according to any one of claims 1 to 3, wherein the illumination light is slit-shaped light. The internal defect inspection apparatus according to claim 7, further comprising an irradiation position moving mechanism that moves the irradiation position of the slit-shaped light. The illumination optical system includes a plurality of illumination light beams emitted from the light source unit to irradiate the object to be inspected in a plurality of directions different from each other. The internal defect inspection apparatus according to claim 1. Illuminating the object to be inspected with illumination light having a wavelength that can pass through the object to be inspected by a predetermined illumination optical system,
An optical image of the object to be inspected is formed by a predetermined imaging optical system that forms a dark field optical system with the predetermined illumination optical system,
Generating an image signal of the optical image by photoelectrically converting the optical image formed by the imaging optical system;
An internal defect inspection method comprising presenting a defect inside the object to be inspected based on the generated image signal of the optical image.

Images