Apparatus and method for inspecting through-holes in transparent substrates based on scanning holography

Abstract

A scanning holography-based transparent substrate through-hole inspection device comprises a stage frame for placing a transparent substrate in an inspection area, a wedge-type reflector composed of a first reflective surface and a second reflective surface positioned at different angles of inclination below the transparent substrate, and a projection detection unit that provides irradiation light to the transparent substrate, transmits through the transparent substrate to simultaneously receive a first reflected light reflected from the first reflective surface and a second reflected light reflected from the second reflective surface to acquire holographic image data, and analyzes the holographic image data to detect defects in the transparent substrate.

Description

Technology Field

[0001] The present invention relates to optical inspection technology, and more specifically, to a transparent substrate inspection device and inspection method capable of automatically detecting and quantifying defects in through holes by integrating a hologram-based scanning optical system and an artificial intelligence analysis algorithm. Background Technology

[0003] Recently, in the manufacturing processes of displays, semiconductors, and optoelectronic devices, technology for precisely machining micrometer or sub-micrometer through-holes in transparent substrates, such as glass substrates or transparent wafers, and for non-destructively inspecting these structures for defects, is emerging as a critical process element. Through-holes are utilized as functional structures for electrode connections, microfluidic channels, and panel wiring, and microscopic defects within the holes, such as cracks, deformation, or blockage, can directly affect product yield and reliability.

[0004] Conventional optical inspection methods have adopted a structure that detects defects based on 2D images by irradiating light onto the upper or lower surface of a transparent substrate and receiving reflected or transmitted light in a single direction. However, this method fails to adequately reflect 3D information, such as the depth structure of through-holes, geometric distortion, and the alignment of the central axis, and its detection performance is limited for micro-defects involving complex structures or alignment errors. In particular, image quality fluctuates easily depending on the optical characteristics and reflection conditions of the transparent substrate, leading to problems where image contrast or focus quality becomes unstable.

[0005] Although hologram-based inspection technologies have been proposed, most are limited to hologram analysis based on single reflected light or a single viewpoint. There is a lack of integrated inspection systems that encompass the acquisition of aligned images based on multiple optical paths, precise correction of center axis errors, and AI-based defect classification.

[0007] Korean Registered Patent No. 10-2129071 (June 25, 2020) relates to an automated optical inspection device based on a scanning hologram, and includes a function to calculate a rotation angle and depth position based on hologram data acquired from an object on a target plate, and to restore an image of the object by forming a rotated coordinate system.

[0008] The scanning hologram-based automatic optical inspection device includes a hologram capturing unit that captures a hologram using a scanning hologram camera, an optical monitoring processing unit that detects the tilt and depth position of an object surface, and a restoration unit that extracts the rotation angle / depth position and aligns an image restoration coordinate system, thereby enabling high-precision image restoration even when the object is in a tilted or out-of-focus state. Prior art literature

[0010] Korean Registered Patent No. 10-2129071 (June 25, 2020) The problem to be solved

[0011] One embodiment of the present invention aims to provide a scanning holography-based transparent substrate through-hole inspection device and method capable of automatically detecting and quantifying defects in through-holes by integrating a hologram-based scanning optical system and an artificial intelligence analysis algorithm.

[0012] One embodiment of the present invention aims to provide a scanning holography-based transparent substrate through-hole inspection device and method capable of acquiring multiple holographic images through a plurality of reflected light paths.

[0013] One embodiment of the present invention aims to provide a scanning holography-based transparent substrate through-hole inspection device and method capable of automatically correcting alignment between reflected light and center axis errors.

[0014] One embodiment of the present invention aims to provide a scanning holography-based transparent substrate through-hole inspection device and method capable of automatically identifying micro-defects in through-holes by combining a Fresnel kernel-based restoration technique and an artificial intelligence classification model.

[0015] One embodiment of the present invention aims to provide a scanning holography-based transparent substrate through-hole inspection device and method capable of generating a composite defect map based on the intensity, frequency, and phase information of an interference pattern. means of solving the problem

[0017] Among the embodiments, a scanning holography-based transparent substrate through-hole inspection device comprises a stage frame for placing a transparent substrate in an inspection area, a wedge-type reflector composed of a first reflective surface and a second reflective surface positioned at different angles of inclination and positioned below the transparent substrate, and a projection detection unit that provides irradiation light to the transparent substrate, transmits through the transparent substrate to simultaneously receive a first reflected light reflected from the first reflective surface and a second reflected light reflected from the second reflective surface to acquire holographic image data, and analyzes the holographic image data to detect defects in the transparent substrate.

[0018] The above stage frame may be formed to fix the transparent substrate on the edge and move in the X-axis and Y-axis directions to perform sequential inspection of the through holes of the transparent substrate, and the inspection area may be opened to prevent interference between the irradiated light and the reflected light.

[0019] The wedge-type reflector may be configured to be spaced apart from the bottom of the transparent substrate by a specific distance, and each of the first and second reflective surfaces may provide different reflection paths and angles of incidence to acquire multiple holograms based on different light paths.

[0020] The wedge-type reflector above can be configured with the first and second reflective surfaces at asymmetric angles to simultaneously obtain bright field images and dark field images.

[0021] The projection detection unit can acquire the holographic image data based on the interference pattern included in the first reflected light and the second reflected light, and can reconstruct the three-dimensional structure of the through-hole of the transparent substrate through a Fresnel diffraction kernel-based convolution operation on the holographic image data.

[0022] The projection detection unit can correct the center axis alignment error for the through-hole of the transparent substrate by performing pixel matching between images obtained from the first reflected light and the second reflected light, respectively.

[0023] The projection detection unit can automatically determine the defect type of the through-hole by inputting a feature vector extracted from the external shape of the through-hole of the transparent substrate through the holographic image data into an artificial intelligence classification model.

[0024] The projection detection unit can independently analyze the interference pattern intensity, frequency component, or phase information of the first reflected light and the second reflected light, respectively, and generate a composite defect map of the transparent substrate based on the results of the analysis. Effects of the invention

[0026] The disclosed technology may have the following effects. However, this does not mean that a specific embodiment must include all of the following effects or only the following effects; therefore, the scope of the rights of the disclosed technology should not be understood as being limited by this.

[0027] A scanning holography-based transparent substrate through-hole inspection device and method according to one embodiment of the present invention can automatically detect and quantify defects in through-holes by integrating a hologram-based scanning optical system and an artificial intelligence analysis algorithm.

[0028] A scanning holography-based transparent substrate through-hole inspection device and method according to one embodiment of the present invention can acquire multiple holographic images through a plurality of reflected light paths.

[0029] A scanning holography-based transparent substrate through-hole inspection device and method according to one embodiment of the present invention can automatically correct alignment between reflected light and center axis errors.

[0030] A scanning holography-based transparent substrate through-hole inspection device and method according to one embodiment of the present invention can automatically determine micro-defects in through-holes by combining a Fresnel kernel-based restoration technique and an artificial intelligence classification model.

[0031] A scanning holography-based transparent substrate through-hole inspection device and method according to one embodiment of the present invention can generate a composite defect map based on intensity, frequency, and phase information of an interference pattern. Brief explanation of the drawing

[0033] FIG. 1 is a drawing showing the overall configuration of a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention. FIG. 2 is a diagram showing the functional block configuration of a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention. FIG. 3 is a sequential flowchart illustrating the overall processing flow of a scanning holography-based transparent substrate through-hole inspection method performed in a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention. FIG. 4 is a conceptual diagram illustrating the optical operation principle of a hybrid inspection mode performed in a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention. FIG. 5 is an overall conceptual diagram showing the principle of a Hybrid inspection mode that simultaneously analyzes reflected light under bright field and dark field conditions based on a wedge-type reflected light structure in a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention, and the inspection results utilizing the same. Specific details for implementing the invention

[0034] The description of the present invention is merely an example for structural or functional explanation, and therefore the scope of the present invention should not be interpreted as being limited by the examples described in the text. That is, since the examples are subject to various modifications and may take various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical concept. Furthermore, the objectives or effects presented in the present invention do not imply that a specific example must include all of them or only such effects; therefore, the scope of the present invention should not be understood as being limited by them.

[0035] Meanwhile, the meaning of the terms described in this application should be understood as follows.

[0036] Terms such as "first," "second," etc., are intended to distinguish one component from another, and the scope of rights shall not be limited by these terms. For example, the first component may be named the second component, and similarly, the second component may be named the first component.

[0037] When it is stated that one component is "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between. Conversely, when it is stated that one component is "directly connected" to another component, it should be understood that there are no other components in between. Meanwhile, other expressions describing the relationships between components, such as "between" and "exactly between," or "adjacent to" and "directly adjacent to," should be interpreted in the same way.

[0038] A singular expression should be understood to include a plural expression unless the context clearly indicates otherwise, and terms such as "include" or "have" are intended to specify the existence of the implemented features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood not to preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0039] In each step, identifiers (e.g., a, b, c, etc.) are used for convenience of explanation and do not describe the order of the steps; the steps may occur differently from the specified order unless a specific order is clearly indicated in the context. That is, the steps may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

[0040] The present invention may be implemented as computer-readable code on a computer-readable recording medium, and the computer-readable recording medium includes all types of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc. Additionally, the computer-readable recording medium may be distributed across networked computer systems, so that computer-readable code can be stored and executed in a distributed manner.

[0041] Unless otherwise defined, all terms used herein have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having meanings consistent with the context of the relevant technology and should not be interpreted as having an ideal or overly formal meaning unless explicitly defined in this application.

[0044] * FIG. 1 is a drawing showing the overall configuration of a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention.

[0045] Referring to FIG. 1, FIG. 1a is a perspective view showing the external state in which a transparent inspection sample (140), a stage frame (110), a wedge-type reflective mirror (120), and a projection detector (130) are arranged in three dimensions, and FIG. 1b is a drawing showing a side cross-sectional structure of the same configuration, conceptually illustrating how multiple reflected light paths formed through the wedge-type reflective mirror (120) are received simultaneously.

[0047] A scanning holography-based transparent substrate through-hole inspection device (100) includes a stage frame (110) on which a transparent inspection sample (140) is mounted, a wedge-type reflective mirror (120) fixedly installed at the bottom of the inspection sample to form multiple reflected light paths, and a projection detection unit (130) that receives reflected light and acquires holographic image data.

[0048] The stage frame (110) is configured to fix a transparent inspection sample (140) on its edge and to be transportable in the X-axis and Y-axis directions, thereby enabling sequential inspection of the entire substrate area. The inspection area of ​​the stage frame (110) is formed with an opening structure so that multiple reflected lights coming from below can reach the projection detection unit (130) without interference.

[0049] The wedge-type reflective mirror (120) is an integrated reflective plate structure composed of a first reflective surface and a second reflective surface having different inclination angles, and when the irradiating light passes through the transparent inspection sample (140) and reaches the corresponding reflective surface, each reflected light is formed along a different reflection path. Unlike the conventional inspection mode switching mirror method, the wedge structure can simultaneously implement bright field and dark field reflection conditions without separate mechanical driving, and has the advantage of minimizing time delay, alignment error, and mechanical vibration through the fixed geometric arrangement of the reflective surfaces.

[0050] The projection detection unit (130) simultaneously receives the reflected lights, acquires holographic image data including an interference pattern, and can obtain multi-mode image information from multiple reflected lights. The projection detection unit (130) may include a high-sensitivity light detection element or an image sensor array and is utilized for subsequent image matching, 3D reconstruction, and artificial intelligence-based defect analysis.

[0051] A structure utilizing a wedge-type reflective mirror (120) can acquire multiple image information based on various reflection angles without requiring a switching mode, thereby providing a structural advantage of simultaneously securing complex holographic images within the same inspection target. The projection detection unit (130) can perform precise defect analysis including depth, shape, center axis error, and internal scattering information for the same through hole.

[0053] FIG. 2 is a diagram showing the functional block configuration of a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention.

[0054] Referring to FIG. 2, a scanning holography-based transparent substrate through-hole inspection device (100) includes a stage frame (210), a wedge-type reflector (220), a projection detection unit (230), and a control unit (240).

[0056] The stage frame (210) performs the function of aligning the transparent substrate with the inspection area and is formed to stably fix the outer edge of the transparent substrate. The stage frame (210) is configured to be linked with a transfer mechanism that moves the substrate to be inspected in the X-axis and Y-axis directions, and through the transfer operation of the stage frame (210), sequential optical inspection can be performed on the through holes distributed throughout the transparent substrate.

[0057] The center of the stage frame (210) is formed with an open structure, and the irradiated light emitted from a light source passes through the open area and reaches the lower reflector (220), and the reflected light reflected from the reflector (220) is configured to be transmitted upward without being blocked by the structure. A black matte surface treatment or an anti-reflection coating may be applied to the structure around the opening of the stage frame (210) to prevent scattering of the irradiated light and reflected light.

[0058] The stage frame (210) may include a vacuum suction type fixing part or a mechanical clamp structure, and the fixing part is designed to be positioned so as not to obstruct the light path by being placed in a position that does not block the transparent substrate's transmission area. After fixing the transparent substrate, it is configured to enable precise transfer through a linear stage that is driven independently in the X-axis and Y-axis directions. The linear stage is driven by a servo motor or a stepping motor and can support a transfer resolution of ±1 μm or less and a travel distance of several hundred millimeters or more.

[0059] A stage frame (210) according to one embodiment is configured as a rectangular metal frame structure, and a vacuum pad that fixes the outer edge of a transparent substrate by vacuum suction may be attached to the upper surface. The stage frame (210) is combined with an XY axis transfer device including a linear motion guide and a ball screw, so that sequential inspection based on linear movement can be performed on through holes distributed in a transparent substrate of 600 mm × 600 mm. An opening with a diameter of 400 mm or more is formed in the center of the stage frame (210), allowing reflected light from the reflector (220) to reach the projection detection unit (230) directly without being blocked by the structure. The inner surface of the stage frame (210) is composed of a matte black anodized aluminum material so that scattering and reflection of the irradiated light and reflected light can be suppressed.

[0060] A stage frame (210) according to an embodiment other than the claim may include a precision movement function in the Z-axis direction to correct surface flatness and height errors of a transparent substrate. For example, a micro-lift module may be installed at the four corners or edge areas of the stage frame (210) to independently control the Z-axis height at each position and automatically correct the inclination or distortion of the substrate. The micro-lift module may be composed of a piezoelectric actuator, a lifting screw, or a thermally expanding micro-actuator. Additionally, the stage frame (210) may include a machine vision-based automatic alignment function for automatically recognizing and aligning a reference position of the transparent substrate. For example, after detecting the position of a substrate corner, mark, or guide hole through an auxiliary camera or line sensor installed around the stage frame (210), the control system may automatically adjust the XYZ-axis position and rotation direction based on the position information and align the reference coordinate system of the substrate with the reference coordinate system of the inspection system. The precision movement function and automatic alignment function included in the stage frame (210) can automatically handle transparent substrates of various specifications or thicknesses within a single system, and can ensure stable position alignment and flatness without user intervention.

[0062] A wedge-type reflector (220) is a reflective structure included in a scanning holography-based transparent substrate through-hole inspection device (100), and is positioned at a predetermined distance from the bottom of a transparent substrate and may be composed of a first reflective surface and a second reflective surface positioned at different angles of inclination. The wedge-type reflector (220) can simultaneously form different reflection conditions within a single structure, thereby reducing inspection time and improving the accuracy of the reflection angle-based matching image.

[0063] The first reflective surface of the wedge-type reflector (220) is formed to provide bright field imaging conditions, and the second reflective surface can be positioned at different angles to provide dark field imaging conditions. The first reflective surface and the second reflective surface each form different angles of incidence and reflection, so that multiple holographic data based on different reflection paths can be acquired for light rays passing through the same transparent substrate. The reflection structure of the wedge-type reflector (220) enables the acquisition of multiple image information without a mechanical switching device for switching inspection modes, thereby minimizing system alignment errors, time delays, and mechanical vibrations. In particular, compared to the conventional mechanical switching mirror method, excellent reflection surface alignment retention and a significant reduction in repeatable alignment errors can be expected. Additionally, the wedge-type reflector (220) has the advantage of lowering the burden of maintenance due to the simplification of the structure of the reflective surface.

[0064] The wedge-type reflector (220) can be implemented by precisely machining the inclined surface in a single flat plate structure or by combining heterogeneous reflective blocks. The machining of the inclined surface of the wedge-type reflector (220) can be implemented through precision CNC grinding, ultrasonic precision machining, or ion beam etching technology, and the reflection angle tolerance can be precisely maintained within ±0.1°. The reflective surface can be composed of high-hardness and low-thermal-expansion materials such as silicon (Si), quartz, alumina (Al₂O₃), or tempered glass, and a metal reflective film such as aluminum (Al), silver (Ag), or platinum (Pt) can be deposited to secure reflection properties. If adjustment of reflection efficiency is required, the reflective surface of the wedge-type reflector (220) may additionally include a dielectric multilayer film (TiO₂ / SiO₂-based) or an anti-diffuse reflection coating layer.

[0065] The first reflective surface and the second reflective surface of the wedge-type reflector (220) can each be precisely formed within a tolerance of ±0.1°, and the difference in inclination angle between the two reflective surfaces can be set to 20°, for example. The distance between the transparent substrate and the wedge-type reflector (220) can be adjusted, for example, in the range of 0.1mm to 12mm, and can be designed to match the light irradiation conditions and the focal length of the projection detection unit (230). The wedge-type reflector (220) is aligned with the lower reference plane of the transparent substrate and the vertical axis, and can be positioned so that the incident angle of the reflected light coincides with the center of the light-receiving surface of the projection detection unit (230). The alignment reference is set according to the optical axis reference point and the Z-axis reference height within the system. The entire reflector can be mounted on a fixed frame and configured so that the reflection angle is stably maintained for a long time.

[0066] In one embodiment, the wedge-type reflector (220) may be implemented as a flat reflective structure having two inclined surfaces, the first reflective surface may be an inclined surface identical to the reference horizontal plane, and the second reflective surface may be fixed at an angle of inclination identical to the angle of the projection detector so that a beam incident from the projection detector may be specularly reflected back. The first reflective surface is fabricated by depositing an aluminum thin film on a quartz-based substrate, and the second reflective surface may have a thin metal film or a multilayer thin-film dielectric mirror stacked in multiple layers to transmit a certain amount of light and reflect the remaining light. A light ray passing through the transparent substrate is specularly reflected from the first reflective surface to form a bright field image based on the aperture shape and the central axis, and a light ray specularly reflected from the second reflective surface may be scattered and reflected from an inspection hole within the transparent substrate to form a dark field image containing information on internal defects and foreign matter within the hole. The two reflected lights are simultaneously received by the light detection element of the projection detector (230), so that holographic data containing multiple information can be obtained in a single shot.

[0067] In an embodiment other than the claims, the wedge-type reflector (220) may be formed with an aspherical curvature structure. For example, the wedge-type reflector (220) may be configured as a curved reflector with a radius of curvature of 100 mm, and may form a structure in which the reflection conditions vary spatially depending on the position of the incident light so that the center induces specular reflection and the periphery induces diffuse reflection. The reflective surface is formed by coating a silver (Ag) reflective film and a scattering auxiliary layer on a curved glass substrate, and a multi-coating technology capable of separately controlling the reflection characteristics of the center and the periphery may be applied. Since the reflection conditions of the curved reflector change continuously depending on the position of the incident light, the diversity and resolution of the reflection angle-based matching image information can be secured simultaneously. In addition, the wedge-type reflector (220) may be configured as a replaceable module depending on the type of inspection target or the required defect analysis item, and a magnetic fixing structure or a bayonet fixing slot structure may be applied for quick switching between modules. The wedge-type reflector (220) controls reflection characteristics and incident conditions according to module selection, enabling the acquisition of images specialized for high-precision hole detection, boundary line crack detection, or foreign matter distribution analysis.

[0069] The projection detection unit (230) is a component of the scanning holography-based transparent substrate through-hole inspection device (100), and simultaneously receives a first reflected light and a second reflected light formed by the first reflective surface and the second reflective surface of the wedge-type reflector (220), respectively, after light irradiated onto the transparent substrate (140) passes through the substrate, and can acquire holographic image data from the reflected light. The projection detection unit (230) can perform the function of detecting defects present in the through-hole of the transparent substrate (140) by analyzing the acquired holographic image data.

[0070] The projection detection unit (230) can generate holographic image data based on interference patterns included in the first reflected light and the second reflected light, and can restore the three-dimensional structure of the through hole by applying a convolution operation using a Fresnel diffraction kernel based on the holographic image data. The Fresnel diffraction kernel is a transfer function that can approximate the diffraction phenomenon of interference fringes, and includes parameters such as the distance between the observation plane and the object plane (z-axis depth), the wavelength of the illumination light (e.g., 405 nm), phase, and amplitude distribution. The projection detection unit (230) can generate a plurality of tomographic images restored for each depth unit by performing a two-dimensional complex convolution operation on the interference fringes, and can construct the three-dimensional shape of the through hole by combining the tomographic images. The Fast Fourier Transform (FFT) is applied to improve the convolution speed of the restoration operation, and can improve the overall computational processing efficiency of the system so that real-time restoration is possible even for a large-area transparent substrate (140) with multiple through holes formed therein.

[0071] The projection detection unit (230) performs pixel matching between holographic images obtained from the first reflected light and the second reflected light, and can accurately determine measurement information regarding the external shape of the through hole of the transparent substrate (140) based on the matching result, and can perform the function of extracting and analyzing external surface condition information, such as micro-cracks in the through hole, in the bright field.

[0072] The projection detection unit (230) can perform the function of independently analyzing the intensity distribution, frequency components, and phase information included in the interference patterns of the first reflected light and the second reflected light, and generating a composite defect map of the transparent substrate (140) based on the analysis results. The projection detection unit (230) can decompose the frequency spectrum of the interference fringe through a fast Fourier transform and analyze areas with high defect sensitivity centered on high-frequency components to extract the location of fine defects or multiple defects with high precision. The projection detection unit (230) can generate a detailed defect distribution map based on differences in energy distribution by frequency band even when defects overlap or composite defects of different sizes and types exist, and the generated defect map can be utilized in conjunction with an inspection report or an automatic quality control system.

[0073] The projection detection unit (230) integrates a series of analysis functions, including image acquisition, restoration, alignment correction, defect identification, and complex defect map generation, based on holographic image data acquired from the first reflected light and the second reflected light, and can realize a non-contact, high-precision, automated through-hole defect detection function within a single device.

[0075] In one embodiment, the projection detection unit (230) may be applied to an inspection device for automatically evaluating the alignment quality of the center axis of a through hole formed in a large-area transparent body inspection sample (140) made of a glass substrate. The projection detection unit (230) simultaneously receives a first reflected light and a second reflected light formed by the illumination light passing through the transparent body inspection sample (140) and being reflected from a wedge-type reflector (220), and can acquire holographic image data including interference patterns from each reflected light. For example, if the center axis alignment error between through holes of a glass substrate that has been processed through on both sides is at the level of ±3μm, the projection detection unit (230) can perform a phase cross correlation (PCC)-based alignment algorithm on a plurality of acquired holographic images and calculate alignment correction values ​​for the x-coordinate, y-coordinate, and θ-axis (rotation angle) between each alignment pair. The projection detection unit (230) corrects the single-layer reconstruction images based on the alignment correction value, reconstructs the aligned three-dimensional through-hole shape, and evaluates the alignment quality between the multilayer substrates based on the reconstruction result using a numerical standard.

[0076] In another embodiment, the projection detection unit (230) can be applied to inspect a glass interposer placed between a semiconductor chip and a substrate packaging substrate. Compared to conventional silicon interposers, the glass interposer has electrical insulation properties and a coefficient of thermal expansion that falls between that of silicon and a PCB substrate, resulting in less warping due to thermal expansion compared to silicon interposer-based packaging substrates, and is being developed as a material for a next-generation I / O redistribution layer.

[0077] In glass interposers, microcracks may occur due to the characteristics of glass during the through-hole and panel splitting processes, and since these cracks can develop into conductive cracks in subsequent processes, it is very important to filter them out in advance through prior detection. The projection detection unit (230) can accurately determine measurement information regarding the external quality shape of the through-hole formed in the glass interposer using a dark field, and is suitable for extracting and analyzing external surface condition information, such as microcracks within the through-hole, using a bright field. In another embodiment, the projection detection unit (230) can be applied to a configuration for high-speed inspection of the edge quality of hundreds of thousands or more through-holes formed on a thin-film transistor (TFT) substrate for a display. The projection detection unit (230) can acquire holographic image data containing interference patterns in real time using the first reflected light and the second reflected light received from the large-area transparent inspection sample (140), and can reconstruct the cross-sectional shape of each through-hole through a Fast Fourier Transform-based reconstruction algorithm. For example, if there is a process condition in which the contrast of the reference edge must be maintained at 20:1 or higher, the projection detection unit (230) calculates the rate of change of the grayscale gradient value for the pixel group outside the through hole of the restored cross-sectional image and calculates the edge sharpness index, and if the reference contrast is degraded, the through hole can be automatically classified as an edge break defect. The coordinates of the through hole having an abnormal edge are automatically collected and aggregated in a map format, and can be used as basic data for yield analysis and readjustment of process conditions.

[0078] In an additional embodiment, the projection detection unit (230) may be applied to a configuration for non-destructively inspecting whether fine foreign substances are mixed inside a transparent through-hole formed on a PET-based lens protection film attached to a vehicle camera module. The projection detection unit (230) receives a first reflected light and a second reflected light generated by the illumination light transmitted through the PET film being reflected from a wedge-type reflector (220), and can obtain a holographic image from the interference pattern included in the reflected light. For example, if the diameter of the through-hole is 100 μm and foreign substances with a particle size of 3 μm or more are attached to the wall surface, the projection detection unit (230) can determine local density anomalies by comparing the texture density distribution of the restored 3D image with a reference vector. The area where an anomaly distribution is detected is classified and labeled through a CNN-based foreign substance detection algorithm, and a reliability score (e.g., 96.3%) is assigned along with the defect location and can be stored as historical data at the film roll level.

[0079] In an embodiment other than the claims, the projection detection unit (230) may be applied to an inspection device for verifying whether an electrode pattern formed inside a transparent OLED panel for an augmented reality (AR) device is precisely aligned at a position penetrating the substrate. The transparent body inspection sample (140) has a structure in which a metal electrode line in micrometer units is connected through a transparent substrate, and the irradiated light can generate complex interference patterns due to the difference in refractive index between the metal layer and the transparent layer. The projection detection unit (230) can convert the acquired interference pattern into the frequency domain and detect whether there is an interface refractive anomaly by analyzing the phase change included in each frequency component based on the spectrum. For example, if the internal metal layer has a fine thickness deviation in some sections or if foreign substances that induce abnormal scattering are mixed in, the projection detection unit (230) classifies the corresponding area as an abnormal pattern based on an increase in the energy density of high-frequency components, and the inspection result can be reflected in the calculation of adjustment values ​​at the beginning of the panel manufacturing process.

[0080] In another embodiment other than the claims, the projection detection unit (230) may be integrated into a line system that automatically inspects micro-through holes formed in a flexible transparent substrate supplied continuously in a roll-to-roll manner. The flexible substrate is transported at a constant speed on a reflector (220) without a stage frame (210), and the illumination light is incident on the moving substrate to form real-time interference patterns. The projection detection unit (230) can capture frames at 0.1-second intervals, correct the relative displacement between consecutive images, and then apply a restoration algorithm to construct a three-dimensional through-hole shape. Based on the restored shape, the projection detection unit (230) evaluates the straightness of the central axis, and if traces of residual silicon particles detected in a specific frequency band exist at the edge of the through-hole, it can be automatically classified as a foreign substance defect. The corresponding foreign substance coordinate information can be recorded in roll-unit quality certification data.

[0081] In another embodiment other than the claims, the projection detection unit (230) may be applied to inspect micro-defects and foreign matter around through-holes during the post-processing stage of a large OLED TV panel. After the panel is completed, a plurality of reflected light interference patterns are obtained from the location of the through-holes on the transparent inspection sample (140). Then, the projection detection unit (230) can reconstruct the three-dimensional shape of each through-hole and analyze the phase distribution through a restoration algorithm. For example, if the amplitude value restored in the border area shows a deviation of 10% or more from the reference, the projection detection unit (230) can determine that it is an area with a possibility of micro-scratches that are not visible externally or internal contamination. The projection detection unit (230) can calculate a precise location based on an xy coordinate system and record the corresponding coordinates and an abnormality judgment indicator in a re-inspection log file. The OLED TV panel manufacturing system can perform manual inspection or transfer to a local repair process based on the recorded information, thereby reducing the possibility of micro-defects being missed during the post-processing stage.

[0082] In an additional embodiment, the projection detection unit (230) may be applied to analyze micro-delamination defects between dielectric-electrode layers formed in a multilayer structure inside a transparent substrate for an autonomous driving sensor or LiDAR device. The transparent inspection sample (140) has a structure in which 3 to 5 thin film layers are stacked at intervals of several μm, and internal delamination defects are not detected externally. The projection detection unit (230) can detect regions where phase discontinuity occurs at a specific z-depth through frequency analysis of reflected light interference patterns, and can measure the delamination location based on a rapid transition of the amount of phase change within the restored 3D data. The projection detection unit (230) can determine delamination if the average phase gradient at a specific height exceeds a reference value (e.g., 0.2 rad / μm), and the corresponding coordinates can be generated as an automatic report and linked with a manufacturing process monitoring system.

[0083] In an additional embodiment, the projection detector (230) may be used to inspect the cross-sectional shape of a microchannel structure within a transparent glass substrate used in a biochip or lab-on-a-chip device. The transparent inspection sample (140) may include a structure in which a precision etching channel is formed with a width between 50 μm and 200 μm and a depth of 20 μm or more. Since fluid moves or reaction reagents are introduced inside the channel, if air bubbles, processing residues, or wall defects are present, fluid flow obstruction or reaction delay problems may occur. In this case, the transparent inspection sample (140) requires a non-destructive precision shape inspection. The projection detector (230) can acquire interference patterns generated by the reflection of the illumination light after it passes through the transparent inspection sample (140), and can reconstruct the three-dimensional shape of the microchannel by restoring a plurality of z-axis cross-sections. Regarding the restored cross-sectional shape, the projection detection unit (230) can calculate the inclination, curvature, bending deviation, and depth-to-cross-sectional width ratio of the channel wall surface, and can evaluate straightness by modeling the center axis as a three-dimensional curve from multiple cross-sectional data. For example, if the inclination of the center axis changes by ±2° or more within a certain section (e.g., 1 mm length) or if the difference in distance between the left and right walls within the cross-section exceeds 10%, the projection detection unit (230) can determine that the channel is abnormally processed. The abnormality determination result is stored as an automatic log along with the center coordinates, channel ID, and defect type, and the processing precision history of the entire biochip can be collected and utilized for process stability evaluation and shipment quality control.

[0085] The control unit (240) can integrally control the overall operation of the scanning holography-based transparent substrate through-hole inspection device (100) and coordinate control signals and data flow between the stage frame (210), the wedge-type reflector (220), and the projection detection unit (230).

[0086] The control unit (240) can control the movement of the X-axis and Y-axis of the stage frame (210) to sequentially adjust the position of the inspection target and output a command to set the inclination angle of the wedge-type reflector (220). In addition, the control unit (240) can control the image acquisition timing and interference pattern restoration sequence of the projection detection unit (230) so that the three-dimensional shape reconstruction is performed smoothly.

[0087] The control unit (240) can select the operation mode of the device according to user-set conditions and monitor the status of each component in real time to stop or restart the operation in the event of an error. In addition, the control unit (240) can transmit the image and analysis data of the projection detection unit (230) to an external storage device or user interface device to be used for visualization of inspection results and quality control.

[0089] FIG. 3 is a sequential flowchart illustrating the overall processing flow of a scanning holography-based transparent substrate through-hole inspection method performed in a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention.

[0090] Referring to FIG. 3, the scanning holography-based transparent substrate through-hole inspection method comprises a substrate mounting and inspection position control step (S310), a light irradiation and reflected light reception step (S320), a hologram generation and 3D structure restoration step (S330), an image matching and center axis correction step (S340), an AI-based defect analysis and automatic identification step (S350), and a composite defect map generation step (S360).

[0092] The substrate mounting and inspection position control step (S310) is a step of fixing a transparent inspection sample (140) to an inspection area on a stage frame (210), moving it in the X-axis and Y-axis directions, and sequentially setting inspection points where through holes are located. The stage frame (210) can be configured to fix the edges of the substrate using vacuum suction or a mechanical clamp, and to enable fine positional movement through linear motor-based control. The control unit (240) automatically designates inspection positions according to the through-hole arrangement coordinates and can sequentially move all inspection points within a large-area substrate.

[0093] The light irradiation and reflected light reception step (S320) is a step in which the projection detector (230) irradiates light onto a transparent body inspection sample (140) and simultaneously receives light reflected from an inner first reflective surface and an outer wedge-type reflector (220). The irradiated light passes through the substrate and through the through-hole, is reflected from the lower first reflective surface and the inclined reflector (220), and enters the projection detector (230) again. At this time, the received light includes interference effects, and reflected light under bright field and dark field conditions can be superimposed and recorded within a single frame. The reflection pattern collected in the light irradiation and reflected light reception step (S320) can provide base data for simultaneously collecting optical defect information and shape information.

[0094] The hologram generation and 3D structure restoration step (S330) is a step of generating a hologram image from interference light and restoring the 3D structure of the through hole by performing Fresnel diffraction and angular spectrum-based convolution operations on the image. The projection detection unit (230) can store the received interference pattern as a digital image and generate multiple cross-sectional images in the z-axis direction by applying an FFT-based restoration algorithm. The generated cross-sections show fine features such as changes in the diameter of the through hole, taper angles, and wall curvatures, and images for each depth can be combined to obtain 3D shape information of the through hole.

[0095] The image matching and center axis correction step (S340) is a step of precisely aligning pixels between a first reflection image and a second reflection image acquired at the same location and correcting alignment errors based on the center axis. The projection detection unit (230) automatically corrects the positional and angular differences between the two images by applying a phase cross-correlation method or a feature point tracking-based matching algorithm, and can quantitatively calculate whether the center axis tilt or eccentricity is present. The center axis correction result is subsequently used as a reference axis for defect analysis and can contribute to maintaining geometric consistency.

[0096] The AI-based defect analysis and automatic determination step (S350) is a step of extracting shape feature vectors of through holes from a restored 3D image and inputting them into an artificial intelligence classification model to automatically determine whether there is a defect and the type thereof. For example, the projection detection unit (230) can extract quantitative shape indicators such as diameter deviation of the through hole, wall curvature, center axis asymmetry, and edge discontinuity from the restored through hole image, and input the extracted indicators into a classification model such as a multilayer perceptron (MLP), a convolutional neural network (CNN), or a support vector machine (SVM) to determine whether there is an abnormality. The output result is provided along with the defect type (e.g., eccentricity, step, non-circularity), location, and reliability, and can be used for automatic quality determination during the entire inspection process.

[0097] The complex defect map generation step (S360) is a step of generating a complex defect map based on individual analysis results performed on the entire inspection area. The projection detection unit (230) visually arranges the analysis data of each through-hole according to spatial coordinates and analyzes the defect distribution pattern to determine whether there is a systemic abnormality in the processing process. By comprehensively analyzing the phase change, frequency components, and intensity distribution of the interference pattern, the spatial correlation of not only single defects but also complex defects (e.g., eccentricity + interlayer step difference) can be identified. The generated defect map can be stored through the control unit (240) or transmitted to an external quality control system and utilized for feedback control of the manufacturing line.

[0099] FIG. 4 is a conceptual diagram illustrating the optical operation principle of a hybrid inspection mode performed in a scanning holography-based transparent substrate through-hole inspection device (100).

[0100] Referring to FIG. 4, the Hybrid inspection mode is configured to efficiently collect various defect information while reducing inspection time and equipment complexity by simultaneously receiving reflected light under bright field and dark field conditions using a single illumination light path. Generally, since the bright field is sensitive to surface shape and material contrast, and the dark field is advantageous for detecting fine defects, scratches, or inherent cracks, the Hybrid inspection mode enables high-precision image analysis by combining the advantages of both conditions.

[0101] The hybrid inspection mode is a structure that separates and receives reflected light under different observation conditions by utilizing the difference in reflection position and reflection angle for a single illumination light, and a wedge-type reflective mirror (120) is used. The wedge-type reflective mirror (120) is a structure that combines two inclined transparent substrates, a beam splitting coating with a reflectivity of 50% is applied to the first incident surface, and a high-reflection coating for total reflection is applied to the second incident surface.

[0102] When the irradiating light passes through the transparent inspection sample (140) and is incident on the wedge-type reflective mirror (120), some of the light (about 50%) is reflected from the first incident surface and returns along a path of a relatively large angle, reaching the projection detector (130) as dark field reflected light. The remaining light passes through the first surface and is totally reflected from the second surface, reflecting at a relatively small angle, and reaches the projection detector (130) in the same way as bright field reflected light.

[0103] The projection detection unit (130) records bright field and dark field information superimposed within a single image based on interference patterns received simultaneously through two reflection paths, and can quantitatively obtain fine defect information along with shape information of the glass through-hole.

[0104] An optical structure utilizing a wedge-type reflective mirror (120) has a simpler structure compared to a conventional beam scanning unit for changing inspection angles, and can provide the advantage of simultaneously collecting various reflected light information without separate mechanical movement. In particular, since cracks inside the glass or abnormal wall reflection characteristics can be clearly seen in the dark field image, the Hybrid inspection mode can be utilized as an effective inspection method that simultaneously satisfies precise shape analysis and non-destructive defect detection.

[0106] FIG. 5 is an overall conceptual diagram showing the principle of a Hybrid inspection mode that simultaneously analyzes reflected light under bright field and dark field conditions based on a wedge-type reflected light structure in a scanning holography-based transparent substrate through-hole inspection device (100) according to one embodiment of the present invention, and the inspection results utilizing the same.

[0108] FIG. 5a is a side view illustrating a structure that utilizes a glass wedge structure to receive bright field and dark field reflected light separately in a single illumination light path. Illumination light passing through a through-hole in a glass substrate is incident on a wedge-type reflective mirror. Light reflected from the first incident surface with a reflectivity of 50% returns at a relatively large angle of reflection to become dark field reflected light, while the remaining light passes through the front surface and is totally reflected from the second surface, reflecting at a small angle to become bright field reflected light. The bright field reflected light and dark field reflected light are received simultaneously at the projection detector, and the structure is configured to collect images of both observation conditions in a single shooting motion without mechanical changes to the illumination angle or the angle of reflection.

[0109] Figure 5b is an image of the actual inspection result obtained by applying the Hybrid inspection mode to a through-hole in a glass substrate. The image clearly shows various defect characteristics such as the outer boundary of the through-hole, surface inclination shape, internal cracks, and abnormal wall reflection distribution, and empirically demonstrates that the Hybrid inspection mode can provide more precise non-destructive inspection capabilities than conventional methods based on single observation conditions of bright field or dark field.

[0110] Inspection results collected through the hybrid inspection mode provide foundational information for quantitatively determining the presence of abnormalities inside the hole, and can also be effectively utilized in image-based defect detection algorithms or the configuration of automated inspection systems.

[0112] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims. Explanation of the symbols

[0114] 100: Scanning Holography-Based Transparent Substrate Through-hole Inspection Device 110: Stage frame 120: Wedge-type reflective mirror 130: Projection detector 140: Transparent object inspection sample 210: Stage frame 220: Wedge-type reflector 230: Projection detection unit 240: Control unit

Claims

Claim 1 A scanning holography-based transparent substrate through-hole inspection device comprising: a stage frame for placing a transparent substrate in an inspection area; a wedge-type reflector composed of a first reflective surface and a second reflective surface placed below the transparent substrate and arranged at different angles of inclination; and a projection detection unit that provides irradiation light to the transparent substrate, transmits through the transparent substrate to simultaneously receive a first reflected light reflected from the first reflective surface and a second reflected light reflected from the second reflective surface to acquire holographic image data, and analyzes the holographic image data to detect defects in the transparent substrate. Claim 2 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, wherein the stage frame fixes the transparent substrate on the edge and moves in the X-axis and Y-axis directions to perform sequential inspection of the through-hole of the transparent substrate, and the inspection area is formed to be open to prevent interference between the irradiated light and the reflected light. Claim 3 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, characterized in that the wedge-type reflector is spaced apart from the lower part of the transparent substrate by a specific distance, and each of the first and second reflective surfaces is configured to provide different reflection paths and angles of incidence to acquire multiple holograms based on different light paths. Claim 4 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, characterized in that the wedge-type reflector is configured with the first and second reflective surfaces at an asymmetric angle to simultaneously obtain a bright field image and a dark field image. Claim 5 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, wherein the projection detection unit acquires holographic image data based on interference patterns included in the first reflected light and the second reflected light, and restores the three-dimensional structure of the through-hole of the transparent substrate through a Fresnel diffraction kernel-based convolution operation on the holographic image data. Claim 6 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, wherein the projection detection unit performs pixel matching between images obtained from the first reflected light and the second reflected light, respectively, to correct the center axis alignment error for the through-hole of the transparent substrate. Claim 7 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, wherein the projection detection unit inputs a feature vector extracted from the external shape of the through-hole of the transparent substrate through the holographic image data into an artificial intelligence classification model to automatically determine the defect type of the through-hole. Claim 8 A scanning holography-based transparent substrate through-hole inspection device according to claim 1, wherein the projection detection unit independently analyzes the interference pattern intensity, frequency component, or phase information of the first reflected light and the second reflected light, respectively, and generates a composite defect map of the transparent substrate based on the results of the analysis.

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