Image data generation method and inspection device
By rotating the light source, detector, and holding unit in a parallel plane and using pixel value correction and interpolation, the method generates accurate, seamless cross-sectional image data, addressing the inaccuracies caused by warping and bending in conventional CT inspection methods, thus improving electronic component inspection accuracy.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SAKI CORPORATION
- Filing Date
- 2025-11-10
- Publication Date
- 2026-05-21
Smart Images
Figure JP2025039290_21052026_PF_FP_ABST
Abstract
Description
Method for Generating Image Data and Inspection Apparatus
[0001] The present invention relates to a method for generating image data and an inspection apparatus.
[0002] In an electronic substrate (hereinafter simply referred to as "substrate"), it is difficult to determine the connection state between an electronic component (e.g., a pin) and a wiring on the substrate by solder in an appearance inspection, and an inspection apparatus using a CT (Computed Tomography) method using X-rays is used. Specifically, it is configured to rotate and move a test object (substrate) held by a holding unit and a detector within the X-ray beam emitted from a light source to acquire its transmission image data and generate three-dimensional image data (see, for example, Patent Document 1).
[0003] Japanese Patent Application Laid-Open No. 2019-060808
[0004] Generally, the three-dimensional image data reconstructed from the transmission image data is configured by stacking a plurality of cross-sectional image data parallel to a reference plane. Therefore, if the test object is a substrate without warping, bending, or inclination, the upper surface of the substrate constituting the test object (hereinafter referred to as "substrate inspection surface") is not imaged across a plurality of cross-sectional image data. However, if the test object has warping, bending, or inclination, the substrate inspection surface will extend across a plurality of cross-sectional image data. Therefore, in a conventional inspection apparatus, a portion where the substrate inspection surface appears is cut out from a plurality of cross-sectional image data and joined together to generate image data of the entire substrate inspection surface. However, when generating image data of the entire substrate inspection surface by cutting out and joining cross-sectional image data, a shape that does not originally exist may be formed at the joint portion, resulting in a problem of reduced inspection accuracy.
[0005] The present invention has been made in view of such problems, and an object thereof is to provide a method for generating image data and an inspection apparatus that generate seamless cross-sectional image data by generating cross-sectional image data along the substrate inspection surface of a test object.
[0006] To solve the aforementioned problems, the present invention provides an image data generation method in which two of the light source, detector, and holding part that holds the object to be inspected are rotated in a plane parallel to each other, and the transmitted image data of the object to be inspected is obtained by detecting the light emitted from the light source and transmitted through the object to be inspected by the detector, and the method generates a cross-sectional image data of the object to be inspected using at least two transmitted image data acquired at different positions in the plane, wherein the pixel values of the cross-sectional image data of the substrate inspection surface are generated from the pixel values of the position information corrected based on the position information of the substrate inspection surface of the object to be inspected in the transmitted image data.
[0007] Furthermore, in the image data generation method according to the present invention, it is desirable to generate the pixel values of the cross-sectional image from the pixel values of the transmitted image data using a filter-corrected back projection method or a successive approximation method.
[0008] Furthermore, in the image data generation method according to the present invention, it is desirable to acquire positional information of multiple locations on the substrate inspection surface of the object to be inspected, and to calculate the positional information of each pixel of the cross-sectional image data from the positional information of the multiple locations using an interpolation method.
[0009] Furthermore, in the image data generation method according to the present invention, it is desirable that the position information be managed as coordinate data in three-dimensional space.
[0010] Furthermore, in the image data generation method according to the present invention, it is desirable that the position information be obtained by irradiating the substrate inspection surface of the object to be inspected with laser light and detecting the reflected light of the laser light.
[0011] Furthermore, in the image data generation method according to the present invention, it is desirable that the position information be calculated based on the location with high similarity, by acquiring image data of the substrate inspection surface of the object to be inspected, calculating the similarity between the image data and reference image data using template matching or phase correlation method, and then calculating the position information based on the location with high similarity, and the deviation information of that location in the image data from the reference image data.
[0012] Furthermore, the inspection apparatus according to the present invention comprises a light source, a detector, a holding unit for holding an object to be inspected, a substrate inspection surface height detection unit for detecting positional information of the substrate inspection surface of the object to be inspected, and a control unit that rotates two of the light source, the detector, and the holding unit in a plane parallel to each other, and generates a cross-sectional image data of the object to be inspected using at least two transmitted image data obtained at different positions in the plane, which are transmitted image data of the object to be inspected obtained by detecting the light emitted from the light source and transmitted through the object to be inspected by the detector, wherein the control unit generates and holds the cross-sectional image data of the substrate inspection surface based on the positional information of the substrate inspection surface detected by the substrate inspection surface height detection unit using one of the image data generation methods described above.
[0013] Furthermore, the inspection apparatus according to the present invention has a display unit, and it is desirable that the control unit outputs seamless cross-sectional image data generated by the control unit to the display unit for the bent object under inspection.
[0014] According to the present invention, it is possible to provide an image data generation method and inspection apparatus that generate seamless cross-sectional image data by generating cross-sectional image data along the substrate inspection surface of the object to be inspected.
[0015] This is an explanatory diagram illustrating the configuration of the inspection apparatus according to the first embodiment. This is an explanatory diagram illustrating each functional block of the control unit of the inspection apparatus. This is a flowchart illustrating the inspection process in the inspection apparatus. This is a flowchart illustrating the transmission image acquisition and reconstructed image generation process in the inspection process, where (a) shows the transmission image acquisition and reconstructed image generation process and (b) shows the displacement amount calculation process. This is a flowchart illustrating the judgment process in the inspection process. This is an explanatory diagram illustrating the height information of the substrate inspection surface. This is an explanatory diagram illustrating the relationship between cross-sectional image data and transmission image data. This is an explanatory diagram illustrating the configuration of the inspection apparatus according to the second embodiment. This is a flowchart illustrating the inspection process in the inspection apparatus. This is a flowchart illustrating the transmission image acquisition and reconstructed image generation process in the inspection process, where (a) shows the transmission image acquisition and reconstructed image generation process and (b) shows the displacement amount calculation process. This is an explanatory diagram illustrating the range for generating reconstructed image data (pseudo-cross-sectional image data) of an object to be inspected that is held at an angle, where (a) shows the conventional range and (b) shows the range in this embodiment.
[0016] Preferred embodiments of the present invention will be described below with reference to the drawings.
[0017] (First Embodiment) First, the inspection apparatus 1 according to the first embodiment will be described. As shown in Figure 1, the inspection apparatus 1 is configured to have a control unit 10 which is composed of a processing unit such as a personal computer (PC), a monitor 11 which is a display unit, and an imaging unit 32. The imaging unit 32 also has a radiation generator 22, a holding unit 24, a detector 26, a beam quality changing unit 14, a light source drive unit 16, a holding unit drive unit 18, and a detector drive unit 20.
[0018] The radiation generator 22 is a device (light source) that generates radiation such as X-rays, and generates radiation by, for example, colliding accelerated electrons with a target such as tungsten or diamond. In this embodiment, the radiation will be described in the case of X-rays, but it is not limited to this. For example, the radiation may be alpha rays, beta rays, gamma rays, ultraviolet rays, visible light, or infrared rays. The radiation may also be microwaves or terahertz waves. The radiation generator 22 is configured to emit radiation along axis A passing through the focal point of the radiation generator 22 (the axis (optical axis) passing through the center of the direction of radiation emitted from the radiation generator 22, and the direction of this axis is defined as the "Z-axis direction"). Therefore, in the absence of obstacles, the luminous beam of radiation emitted from the radiation generator 22 will be conical with the light source at its apex.
[0019] The holding unit 24 holds the substrate, which is the object to be inspected 12. The object to be inspected 12 held by the holding unit 24 is irradiated with radiation generated by the radiation generator 22, and the radiation that passes through the object to be inspected 12 is detected by the detector 26 and captured as an image (acquired as image data). Hereinafter, the radiation transmission image data of the object to be inspected 12 captured by the detector 26 will be referred to as "transmission image data". As will be described later, in this embodiment, the holding unit 24 holding the substrate, which is the object to be inspected 12, and the detector 26 are moved relative to the radiation generator 22 to acquire multiple transmission image data, and a reconstructed image data (cross-sectional image data), which is a three-dimensional image, is generated from these transmission image data.
[0020] The transmission image data captured by the detector 26 is sent to the control unit 10, where it is reconstructed into image data including the three-dimensional shape of the solder joint using known techniques such as the filtered-backprojection method (FBP method) or the iterative approximation method. The reconstructed image data and transmission image data are then stored in the storage within the control unit 10 (for example, the memory unit 34 described later) or in external storage (not shown). Hereinafter, image data extracted from a cross-section of the three-dimensional shape calculated based on the transmission image data will be called "cross-sectional image data." A set of one or more cross-sectional image data will be called "three-dimensional image data" or "reconstructed image data." In other words, cross-sectional image data is image data obtained by cutting out an arbitrary cross-section from three-dimensional image data (reconstructed image data). Such reconstructed image data and cross-sectional image data are output to the monitor 11. The monitor 11 displays not only the reconstructed image data and cross-sectional image data, but also the inspection results of the solder joint state, which will be described later. Here, the reconstructed image data in this embodiment is also called "planar CT" because, as described above, it is reconstructed from a planar image (transmission image data) captured by the detector 26.
[0021] The radiation quality changing unit 14 changes the quality of the radiation generated by the radiation generator 22. The quality of the radiation is determined by the voltage applied to accelerate the electrons that collide with the target (hereinafter referred to as "tube voltage") and the current that determines the number of electrons (hereinafter referred to as "tube current"). The radiation quality changing unit 14 is a device that controls these tube voltage and tube current. This radiation quality changing unit 14 can be realized using known technologies such as transformers and rectifiers.
[0022] Here, the quality of radiation is determined by its brightness and wavelength (spectral distribution of radiation). Increasing the tube current increases the number of electrons that collide with the target, and thus the number of photons produced by the radiation. As a result, the brightness of the radiation increases. For example, some components, such as capacitors, are thicker than other components, and to capture transmission images of these components, it is necessary to irradiate them with high-brightness radiation. In such cases, the brightness of the radiation is adjusted by adjusting the tube current. Also, increasing the tube voltage increases the energy of the electrons that collide with the target, and thus the energy (spectrum) of the generated radiation increases. Generally, the higher the energy of the radiation, the greater its penetrating power through materials and the less easily it is absorbed by those materials. Transmission images captured using such radiation have low contrast. Therefore, the tube voltage can be used to adjust the contrast of the transmission image.
[0023] The inspection device 1 is configured to acquire transmission image data by rotating two of the following components—a radiation generator 22 which is a light source, a holding unit 24 which holds the object to be inspected 12, and a detector 26—in a plane parallel to each other, detecting the radiation emitted from the radiation generator 22 and transmitted through the object to be inspected 12 with the detector 26, and capturing a transmitted image of the object to be inspected 12. In this configuration, the object to be inspected 12, held by the holding unit 24, is rotated along a rotational trajectory (holding unit rotational trajectory) 28 on the holding unit trajectory plane, which is a plane perpendicular to axis A, within the luminous beam of radiation emitted from the radiation generator 22, and simultaneously rotating the detector 26 along a rotational trajectory (detector rotational trajectory) 30 on a detector trajectory plane different from the holding unit trajectory plane, thereby detecting the radiation transmitted through the object to be inspected 12 and capturing a transmitted image of the object to be inspected 12. Furthermore, the orbital planes of the holding unit rotation orbit 28 and the detector rotation orbit 30 are perpendicular to the Z-axis direction as described above. If the directions perpendicular to these orbital planes are defined as the X-axis direction and the Y-axis direction, the positions of the holding unit 24 in the X-axis and Y-axis directions are detected by the substrate position detection unit 29 and output to the control unit 10, and the positions of the detector 26 in the X-axis and Y-axis directions are detected by the detector position detection unit 31 and output to the control unit 10.
[0024] The light source drive unit 16 has a drive mechanism such as a motor (not shown) that can move the radiation generator 22 up and down in the Z-axis direction along the axis A described above. This makes it possible to change the irradiation field by changing the distance between the radiation generator 22 and the object to be inspected (substrate) 12 held by the holding unit 24, and to change the magnification of the transmitted image captured by the detector 26. The position of the radiation generator 22 in the Z-axis direction is detected by the light source position detection unit 23 and output to the control unit 10.
[0025] The holding unit drive unit 18 has a drive mechanism such as a motor and rotates the holding unit 24 along a rotational trajectory (holding unit rotational trajectory 28) on the holding unit raceway surface, which is a plane perpendicular to axis A. The holding unit drive unit 18 is an H-shaped XY stage and is configured to include a movable table to which the holding unit 24 is attached, a Y-direction guide extending in the Y-axis direction and a Y-drive unit that moves the movable table in the Y-axis direction along this Y-direction guide, two X-direction guides that support the Y-direction guide at both ends and are configured to allow the movable table and Y-direction guide to move in the X-axis direction, and an X-drive unit that moves the movable table and Y-direction guide in the X-axis direction. The detector drive unit 20 also has a drive mechanism such as a motor and rotates the detector 26 along a rotational trajectory (detector rotational trajectory 30) on the detector raceway surface, which is a plane perpendicular to axis A and different from the holding unit raceway surface. The detector drive unit 20 has the same configuration as the holding unit drive unit 18 described above.
[0026] As described above, the rotational movement of the holding unit 24 and the detector 26 is linked, and they are configured to rotate on the holding unit rotation trajectory 28 and the detector rotation trajectory 30, respectively. This makes it possible to acquire transmission image data by capturing multiple transmission images with different projection directions and angles while changing the relative positional relationship between the object under inspection 12 held by the holding unit 24 and the radiation generator 22. In this embodiment of the inspection apparatus 1, the area on which transmission image data can be acquired on the object under inspection 12 is determined by the size of the radiation detection area of the detector 26 and the relative positions of the radiation generator 22, the object under inspection 12 (holding unit 24), and the detector 26. This area on which transmission image data can be acquired (imaging area) is called the "FOV (field of view)". When the object under inspection 12 is divided into multiple imaging areas (FOV) for imaging, each imaging area moves on the holding unit rotation trajectory 28 described above.
[0027] The rotational radii of the holding unit rotation trajectory 28 and the detector rotation trajectory 30 are not fixed but can be freely changed. This makes it possible to arbitrarily change the irradiation angle of the radiation irradiated onto the substrate, which is the object under inspection 12, and the components attached to this substrate. Alternatively, instead of the above configuration, the holding unit 24 that holds the object under inspection 12 may be fixed, and the radiation generator 22 and detector 26 may be rotated on a trajectory plane which is a plane perpendicular to axis A to acquire transmission image data of the object under inspection 12. Alternatively, the detector 26 may be fixed, and the holding unit 25 that holds the radiation generator 22 and the object under inspection 12 may be rotated on a trajectory plane which is a plane perpendicular to axis A to acquire transmission image data of the object under inspection 12.
[0028] Furthermore, the inspection apparatus 1 according to the first embodiment has a substrate inspection surface height detection unit 32 that detects height information (position in the Z direction) of the upper surface (substrate inspection surface) of the substrate of the object to be inspected 12 held by the holding unit 24. This substrate inspection surface height detection unit 32 is positioned above the holding unit 24 and consists of a displacement sensor that acquires height information of the substrate inspection surface of the substrate, which is the object to be inspected 12 held by the holding unit 24. As this displacement sensor, for example, it can be configured to detect the position in the Z-axis direction of the substrate inspection surface (information relating to height, hereinafter referred to as "height information") by irradiating the substrate inspection surface with laser light and receiving the reflected light, but it is not limited to this configuration. For example, it may be configured to acquire height information by contacting a probe with the substrate inspection surface. In the following description, the substrate inspection surface height detection unit 32 is assumed to be a displacement sensor that acquires height information using laser light, as described above. If the substrate constituting the object to be inspected 12 is free from warping and no bending or tilting occurs when held by the holding part 24, then the substrate inspection surface, which is the top surface of the substrate, is flat, and its position in the Z-axis direction is known from information such as the substrate design (this ideal substrate inspection surface is called the "reference surface"). However, in reality, the substrate constituting the object to be inspected 12 may warp or bend, or the holding part 24 may hold the object to be inspected 12 in an inclined position, so the substrate inspection surface of the object to be inspected 12 held by the holding part 24 is deviated from the reference surface. Therefore, the control unit 10 is configured to obtain height information of the top surface (substrate inspection surface) of the substrate of the object to be inspected 12 held by the holding part 24 using the substrate inspection surface height detection unit 32, and to calculate the amount of deviation from the reference surface. This height information is managed, for example, in a three-dimensional space coordinate system (XYZ coordinate system) with a predetermined position of the inspection device 1 as the origin, but the coordinate system is not limited to this.
[0029] The control unit 10 controls all operations of the inspection device 1 described above. The main functions of the control unit 10 will be explained below with reference to Figure 2. Although not shown, input devices such as a keyboard and mouse are connected to the control unit 10.
[0030] The control unit 10 includes a storage unit 34, an imaging processing unit 36, a substrate inspection surface displacement amount calculation unit 38, a pseudo-cross-sectional image generation unit 40, and an inspection unit 42. Although not shown, the imaging processing unit 36 of the control unit 10 also has the function of an imaging control unit that controls the operation of the beam quality changing unit 14, the light source driving unit 16, the holding unit driving unit 18, and the detector driving unit 20. Furthermore, each of these functional blocks is realized through the cooperation of hardware such as a CPU that performs various calculations, RAM used as a work area for data storage and program execution, and software. Therefore, these functional blocks can be realized in various forms by combinations of hardware and software.
[0031] The memory unit 34 stores information such as imaging conditions for capturing images of the substrate (which is the object under inspection 12) and acquiring transmission image data, as well as information about the substrate's design. The memory unit 34 also stores image data such as transmission image data and reconstructed image data (cross-sectional image data, pseudo-cross-sectional image data) of the substrate, as well as inspection results from the inspection unit 42, which will be described later. The memory unit 34 also stores information for driving the light source drive unit 16, the holding unit drive unit 18, and the detector drive unit 20 (for example, the position of the radiation generator 22, the position (rotational trajectory) and speed at which the holding unit drive unit 18 moves the holding unit 24, the position (rotational trajectory) and speed at which the detector drive unit 20 moves the detector 26, the imaging position for acquiring transmission image data, etc.).
[0032] The imaging processing unit 36 moves the radiation generator 22, the holding unit 24, and the detector 26 using the light source drive unit 16, the holding unit drive unit 18, and the detector drive unit 20 to image the object under inspection 12 held by the holding unit 24 and acquire transmission image data, and generates reconstructed image data (cross-sectional image data) from the transmission image data. The method of acquiring transmission image data (imaging of transmission images) and generating reconstructed image data (cross-sectional image data) by the imaging processing unit 36 will be described later.
[0033] The substrate inspection surface misalignment calculation unit 38 moves the object to be inspected 12 below the substrate inspection surface height detection unit 32 using the holding unit 24, and obtains height information of a predetermined position on the upper surface (substrate inspection surface) of the object to be inspected 12 using the substrate inspection surface height detection unit 32, and calculates the amount of misalignment between the substrate inspection surface of the object to be inspected 12 and the reference surface. Further details will be described later.
[0034] The pseudo-cross-sectional image generation unit 40 generates pseudo-cross-sectional image data (multiple cross-sectional image data included in a predetermined slice thickness) that includes the substrate inspection surface, based on a plurality of transparent image data acquired from the storage unit 34 and the amount of displacement between the substrate inspection surface and the reference surface calculated by the substrate inspection surface displacement amount calculation unit 38. Here, the pseudo-cross-sectional image data is an image of a region of the substrate that is thicker than the cross-sectional image data by stacking a predetermined number of consecutive cross-sectional image data. The number of cross-sectional image data to be stacked is determined by the thickness of the region of the substrate that the cross-sectional image data displays (hereinafter referred to as "slice thickness") and the slice thickness of the pseudo-cross-sectional image data. For example, if the slice thickness of the cross-sectional image data is 50 μm, and the slice thickness is to be the height of a solder ball of a BGA (hereinafter simply referred to as "solder") (for example, 500 μm) as the pseudo-cross-sectional image, then 500 / 50 = 10 cross-sectional image data should be stacked. Furthermore, the cross-sectional image data that constitutes the pseudo-cross-sectional image data and displays the substrate inspection surface of the substrate is called "inspection surface image data".
[0035] Each of the cross-sectional image data that make up the pseudo-cross-sectional image data can be realized using known techniques (reconstruction algorithms), such as the FBP method or the maximum likelihood estimation method. Different reconstruction algorithms result in different properties of the reconstructed image data and different reconstruction times. Therefore, it is possible to prepare multiple reconstruction algorithms and the parameters used in each algorithm in advance and allow the user to select one. This provides the user with the freedom to choose, such as prioritizing a shorter reconstruction time or prioritizing high image quality even if it takes longer. Each of the generated cross-sectional image data is stored in the storage unit 34 along with attribute information such as the position in the Z-axis direction of each cross-sectional image data and the position (coordinate) of pixels in the X-axis and Y-axis directions within the cross-sectional image data.
[0036] The inspection unit 42 is configured to perform various control processes for inspection using the pseudo-cross-sectional image data generated by the pseudo-cross-sectional image generation unit 40, based on the substrate inspection data stored in the memory unit 34. Here, the substrate inspection data is inspection data created for each type of substrate. An inspection area (hereinafter referred to as "inspection window") is set for each location on the image data of the object to be inspected 12 to be inspected, and the inspection data consists of inspection items set for each inspection window and inspection criteria that serve as the basis for determining whether the object is good or bad. One or more inspection windows are set for each inspection item. For example, in an inspection item that determines whether the solder application state is good or bad, usually the same number of inspection windows as the number of solder application areas of the component are set in an arrangement corresponding to the arrangement of the solder application areas. In addition, for inspection items that use image data of the object to be inspected 12 that has undergone predetermined image processing, the content of that image processing is also included in the inspection data.
[0037] The inspection unit 42 inspects the solder joint condition. Since the solder that joins the substrate and the component is located near the substrate inspection surface, it is possible to determine whether the solder is properly joining the substrate and the component by inspecting the inspection surface image data and the cross-sectional image data that shows the area on the radiation generator 22 side relative to the inspection surface image data, i.e., the pseudo-cross-sectional image data.
[0038] Here, "solder joint condition" refers to whether the substrate and the component are joined by solder and whether an appropriate conductive path is created. Inspection of the solder joint condition includes bridge inspection, molten state inspection, and void inspection. "Bridge" refers to an undesirable conductive path between conductors created by the solder joint. "Molten state" refers to whether the joint between the substrate and the component is insufficient due to insufficient solder melting, also known as "floating." "Void" refers to a defect in the solder joint caused by air bubbles within the solder joint. Therefore, the inspection unit 42 includes a bridge inspection unit 44, a molten state inspection unit 46, and a void inspection unit 48.
[0039] The processing by the bridge inspection unit 44, the molten state inspection unit 46, and the void inspection unit 48 will be described later, but the bridge inspection unit 44 and the void inspection unit 48 inspect bridges and voids, respectively, based on pseudo-cross-sectional image data, and the molten state inspection unit 46 inspects the molten state of the solder based on inspection surface image data included in the pseudo-cross-sectional image data. The inspection results from the bridge inspection unit 44, the molten state inspection unit 46, and the void inspection unit 48 are stored in the storage unit 34.
[0040] Figures 3 to 5 are flowcharts showing the flow (inspection process) from capturing transmission images (acquisition of transmission image data) and generating reconstructed image data (pseudo-cross-sectional image data) to performing inspection (acquisition of solder joint status, etc.). The processing in this flowchart starts, for example, when the control unit 10 receives an instruction to start inspection from an input device (not shown).
[0041] As shown in Figure 3, when the inspection is started, the control unit 10 moves the object to be inspected 12 into the inspection device 1 and holds it in the holding unit 24 (step S100). Next, the imaging processing unit 36 of the control unit 10 sets the size of the irradiation field of the radiation emitted from the radiation generator 22 (the imaging area to which radiation is irradiated in order to acquire the transmission image data of the field of view FOV described above) by positioning the radiation generator 22 in the Z-axis direction using the light source drive unit 16 (step S102). If there are multiple imaging areas (field of view FOV) on the object to be inspected 12, one imaging area is selected and set from among them. Then, the transmission image acquisition and reconstruction image generation process is started (step S104).
[0042] As shown in Figure 4(a), when the transmission image acquisition and reconstruction image generation process S104 is started, the control unit 10 first acquires height information of the substrate inspection surface of the object to be inspected 12 in the currently selected imaging area (field of view FOV) and performs a displacement amount calculation process to calculate the amount of displacement from the reference surface (step S1040). Specifically, when the displacement amount calculation process S1040 is executed, as shown in Figure 4(b), the substrate inspection surface displacement amount calculation unit 38 of the control unit 10 moves the object to be inspected 12 below the substrate inspection surface height detection unit 32 using the holding unit 24, and acquires height information of a predetermined position of the object to be inspected 12 using this substrate inspection surface height detection unit 32 (step S10401).
[0043] Figure 6 shows an example of an object under inspection 12, which is an electronic circuit board to be inspected by the inspection device 1. Electronic components 12b to 12f are mounted on the circuit board 12a of this object under inspection 12. The dashed rectangle shown in Figure 6 indicates the currently selected imaging area R. The imaging processing unit 36 of the control unit 10 moves the holding unit 24 with respect to the circuit board inspection surface height detection unit 32 using the holding unit drive unit 18, and measures the height information of multiple locations on the circuit board inspection surface within the imaging area R. In Figure 6, the imaging area R is divided into four sub-regions R1 to R4, and the height information of points P1 to P4 within each sub-region R1 to R4 is measured. Note that when the center of a sub-region can be measured, such as in sub-regions R1 and R2, the height information of the center points P1 and P2 may be acquired. When a component (for example, component 12b) is placed, such as in sub-regions R3 and R4, the system may be configured to acquire the height information of points (for example, P3 and P4) on the circuit board 12a that can be irradiated with laser light, while avoiding the component 12b.
[0044] The substrate inspection surface deviation amount calculation unit 38 calculates the height information of other positions in the imaging region R from these height information P1 to P4 by an interpolation method such as linear interpolation, and calculates the inclination, warp, and deflection of the substrate inspection surface of the inspection object 12 in the imaging region R as the deviation amount from the reference surface (step S10402), and ends the deviation amount calculation process S1040. In the present embodiment, the case of calculating the deviation amount of the substrate inspection surface from the reference surface in the imaging region R by acquiring the height information (the height information of the points P1 to P4) of the partial regions R1 to R4 obtained by dividing the imaging region R into four has been described. However, the number of divisions of the partial regions with respect to the imaging region R is not limited to four, and by dividing more finely, the accuracy of the deviation amount of the substrate inspection surface from the reference surface can be improved.
[0045] Here, the location where the upper surface of the substrate 12a can be directly measured (that is, the location where the electronic components 12b to 12f are not attached and the substrate is exposed, and a laser beam can be directly irradiated onto the upper surface of this substrate) can be determined from data such as the design of the inspection object (electronic substrate) 12. Alternatively, a location where no electronic component is attached may be specified from image data (two-dimensional color image) obtained by imaging the upper surface of the inspection object 12 in advance. Generally, since a green resist is applied to the upper surface of the substrate 12a, the green portion may be identified using the color image data of the inspection object 12, and this green portion may be determined as the location where no electronic component is attached. Further, by specifying the substrate surface where no electronic component is attached from the image data of the inspection object 12, height information can be acquired at the position of the substrate surface while relatively moving the substrate inspection surface height detection unit 32 and the holding unit 24 (inspection object 12), so that height information at a plurality of positions on the substrate inspection surface can be efficiently acquired.
[0046] When acquiring height information for multiple locations within the imaging area R (field of view FOV), the relative positions of the holding unit 24 that holds the object to be inspected 12 and the substrate inspection surface height detection unit 32 may be fixed for each location where height information is to be acquired (if the configuration involves moving the holding unit 24 to move the position from which the laser light from the substrate inspection surface height detection unit 32 is irradiated, the substrate holding unit drive unit 18 moves the substrate holding unit 24 to move the object to be inspected 12 to the position from which the laser light is irradiated, and then the substrate holding unit 24 is stopped) to acquire height information for that location. Alternatively, the relative positions of the holding unit 24 that holds the object to be inspected 12 and the substrate inspection surface height detection unit 32 may be changed (if the configuration involves moving the holding unit 24 to move the position from which the laser light from the substrate inspection surface height detection unit 32 is irradiated, the holding unit drive unit 18 moves the holding unit 24) to acquire height information at a desired position.
[0047] Furthermore, the amount of deviation of the substrate inspection surface from the reference surface may be calculated for each pixel of the cross-sectional image data of the currently selected imaging area R and stored in the storage unit 34. However, storing the amount of deviation for each pixel would result in a very large amount of data. Therefore, it is preferable to calculate the amount of deviation in the imaging area R as a function of an approximate curved surface represented by the position (x, y) in the cross-sectional image data of the imaging area R, based on the height information of a predetermined position of the object to be inspected 12 detected by the substrate inspection surface height detection unit 32 in step S10401, and to store the height information of the predetermined position and information of the approximate curved surface function (for example, the parameters of the approximate curved surface function) in the storage unit 34. In this configuration, the amount of deviation of each pixel in the generation of the reconstructed image data described later is calculated for each pixel based on the height information of the predetermined position and the approximate curved surface function (parameters of this function, etc.).
[0048] Returning to Fig. 4(a), after the imaging processing unit 36 of the control unit 10 moves the holding unit 24 and the detector 26 to the imaging start position corresponding to the currently selected imaging region R, on the rotation trajectories (holding unit rotation trajectory 28 and detector rotation trajectory 30), the holding unit 24 and the detector 26 are started. When the holding unit 24 and the detector 26 are moving on the rotation trajectories 28 and 30, it is determined whether the holding unit 24 and the detector 26 are at the imaging position. When it is determined that they are at the imaging position, the detector 26 images the test object 12 to acquire transmission image data and stores it in the storage unit 34. This process is repeated until imaging at all imaging positions is completed (step S1042). When it is determined that transmission images have been taken at all imaging positions, the imaging processing unit 36 moves the holding unit 24 and the detector 26 from the rotation trajectories to the retracted position and stops them.
[0049] In addition, the movement paths of the holding unit 24 by the holding unit driving unit 18 and the detector 26 by the detector driving unit 20 when acquiring the transmission image data are set in advance in the holding unit driving unit 18 and the detector driving unit 20 by a method of reading the information stored in the storage unit 34 or a method of inputting from an input device. Also, the position of the radiation generator 22 in the Z-axis direction is set in advance in the light source driving unit 16 by a similar method. The acquired transmission image data is stored in the storage unit 34 for each imaging region R (field of view FOV). Also, the irradiation of radiation from the radiation generator 22 to the test object 12 may be configured to continue during rotational movement, or may be configured to irradiate only when the test object 12 is at the imaging position and the detector 26 acquires the transmission image data.
[0050] When the transmission image data is acquired, the cross-sectional image generation unit 36 of the control unit 10 generates reconstructed image data (pseudo cross-sectional image data composed of cross-sectional image data with a predetermined slice thickness including the inspection surface image data as described above) using the transmission image data stored in the storage unit 34, stores it in the storage unit 34, and ends the transmission image imaging / reconstructed image generation process S104 (step S1044).
[0051] Here, the luminance value Vc(x,y,z) of the position (x,y,z) of the inspection device 10 within the inspection space can be calculated from the transmission image data using the following equation (1).
[0052] Vc(x,y,z) = Σi{Vti(g(i,x,z)×β,g(i,y,z)×β)} (1) where, Σi: A function that calculates the sum of the corresponding pixel values (luminance values) Vti(x,y) in each transmission image data from i=1 to N, where N is the number of transmission image data images. g(i,x,z), g(i,y,z): A function that calculates the position in the X-axis direction or Y-axis direction in the i-th transmission image data from the position in the X-axis direction or Y-axis direction and the position in the Z direction of point P. β: Magnification of the transmission image data (ratio of the distance from the radiation generator 22 to the object under examination 12 to the distance from the radiation generator 22 to the detector 26 in the Z-axis direction). Vti(xt,yt): Pixel value (luminance value) at position (xt,yt) in the i-th transmission image data.
[0053] Generally, cross-sectional image data generated from transmission image data is generated as image data of a plane perpendicular to the axis A, i.e., the Z-axis direction, passing through the focal point of the radiation generator 22 (including the reference plane mentioned above). However, it is possible to calculate the pixel values of any point in the inspection space (however, this is limited to points in the space through which light emitted from the radiation generator 22 and detected by the image sensor of the detector 26 passes, i.e., within the imaging area (FOV)).
[0054] For example, as shown in Figure 7, the value (luminance value) Vc(x,y,z0) of point P(x,y,z0) on a reference plane S passing through height z0 in the Z-axis direction can be calculated using the above-mentioned formula (1) from the pixel values (luminance values) Vt(xt,yt) at the corresponding positions in each of the multiple transmission image data 50. Specifically, the value of point P on the reference plane S is calculated using the value of point Ptn(xtn,ytn) in the nth transmission image data 50n and the value of point Ptn+1(xtn+1,ytn+1) in the (n+1)th transmission image data 50n+1. The direction of the radiation that passed through the object under inspection 12 when the transmission image data was acquired is known. Also, with respect to the optical axis A of the radiation generator 22, which is the light source, the X-axis and Y-axis directions are rotationally symmetric. Therefore, by specifying the position P(x, y, z0) of the pixel to be generated in the cross-sectional image data, the identification information i of the transmission image data, and the imaging magnification β, the pixel value of the corresponding location in each transmission image data can be determined based on equation (1), and the pixel value at position P(x, y, z) can be calculated by summing the values of those pixels.
[0055] For example, let's explain the case where an image of the substrate inspection surface S', which is the upper surface of the substrate of the object under inspection 12, is generated as cross-sectional image data. As mentioned above, the displacement amount ΔP is the difference between the position P on the reference surface S when the substrate of the object under inspection 12 is in an ideal state without warping, bending, or tilting, and the position P' on the substrate inspection surface S' of the object under inspection 12 that is currently being inspected. If the object under inspection 12 has no warping, bending, or tilting, then position P and position P' will coincide. If the position of point P on the reference surface S is represented as (x, y), then the displacement amount ΔP at position P is defined as a vector quantity expressed by the following equation (2). As mentioned above, because positional displacement due to warping and bending occurs not only in the Z-axis direction but also in the X-axis and Y-axis directions, the displacement amount ΔP is managed as coordinate data in three-dimensional space.
[0056] ΔP(x,y) = (Δx, Δy, Δz) (2) where, Δx, Δy, Δz: displacement in the X-axis direction, Y-axis direction, and Z-axis direction.
[0057] Each of Δx, Δy, and Δz is either measured for each position (x, y) of point P using the method described above, or obtained by interpolation from the measured values. Alternatively, the displacement amount ΔP = (Δx, Δy, Δz) may be defined as a function of the approximate surface from the measured points.
[0058] If the position of the reference plane S in the Z-axis direction is z0, the coordinates of point P on the reference plane S are given by (x, y, z0), and the position of point P' on the substrate inspection surface S' corresponding to point P (x', y', z') is given by function f as equation (3) below. Note that function f may be configured to store the amount of deviation between the position of point P' on the reference plane S and the position of point P' on the substrate inspection surface S' in a tabular format, as described above, or the amount of deviation may be configured as a function of the approximate surface.
[0059] (x', y', z') = f (x, y, z0) = (x+Δx, y+Δy, z0+Δz) (3)
[0060] Based on the above, by changing the position (x, y, z0) of a point (pixel P) within the imaging region (FOV) at position z0 in the Z-axis direction (by changing x and y while keeping z0 fixed), and correcting according to equation (3), that is, by determining the position (x', y', z') of the point (pixel P') on the substrate inspection surface S' corresponding to each point (pixel P) on the reference surface S, and determining the pixel value (Vc(x', y', z')) at the position of that point (pixel P') from the transmission image data according to equation (1), the image data of the substrate inspection surface S' can be generated as cross-sectional image data.
[0061] Similarly, by changing the position in the Z-axis direction to determine a plane parallel to the reference plane S, and adding the displacement amount ΔP to each coordinate of the parallel plane based on equation (3), the coordinate values (luminance values) of those coordinates can be calculated using equation (1), thereby generating cross-sectional image data of a plane parallel to the substrate inspection surface S'. Thus, by determining the positions of the substrate inspection surface S' and the plane parallel to this substrate inspection surface S' from the reference plane S and the cross section parallel to this reference plane S, and generating cross-sectional image data at those positions, reconstructed image data (pseudo-cross-sectional image data), which is three-dimensional image data, can be generated.
[0062] Here, multiple cross-sectional image data are generated as reconstructed image data from transparent image data, and a reference image data is determined and pseudo-cross-sectional image data is generated for these cross-sectional image data. However, it is also possible to perform the process of determining the reference image data and generating pseudo-cross-sectional image data each time a cross-sectional image data is generated as reconstructed image data, and then generating the next cross-sectional image data.
[0063] Returning to Figure 3, the inspection unit 42 of the control unit 10 selects one of the inspection windows set in the current imaging area (field of view) (step S106), and executes the judgment process (inspection) set in that inspection window (step S108). Various judgment processes can be set in the inspection window, but here we will explain using the process of determining the solder joint state as an example.
[0064] As shown in Figure 5, in the determination process S108, the bridge inspection unit 44 of the control unit 10 acquires pseudo-cross-sectional image data with a slice thickness similar to that of the solder ball being projected from the pseudo-cross-sectional image generation unit 40 (read from the storage unit 34), checks for the presence or absence of a bridge within the currently selected inspection window (step S1081), and makes a determination of whether a bridge exists (step S1082). If no bridge is detected (step S1082:N), the melting state inspection unit 46 of the control unit 10 acquires inspection surface image data included in the pseudo-cross-sectional image data described above (read from the storage unit 34), checks whether the solder is melted or not within the currently selected inspection window (step S1083), and determines the melting state (step S1084). If the solder is molten (step S1084:Y), the void inspection unit 48 of the control unit 10 acquires pseudo-cross-sectional image data partially showing the solder ball from the pseudo-cross-sectional image generation unit 40 (read from the storage unit 34), checks whether a void exists within the currently selected inspection window (step S1085), and makes a void determination (step S1086). If no void is found (step S1086:N), the inspection unit 42 of the control unit 10 determines that the solder joint is normal and outputs this to the storage unit 34 (step S1087). If a bridge is detected (step S1082:Y), if the solder is not molten (step S1084:N), or if a void exists (step S1086:Y), the inspection unit 42 determines that the solder joint is abnormal and outputs this to the storage unit 34 (step S1088). Once the solder state is output to the storage unit 34, the determination process in this flowchart is terminated. Bridge inspection, molten state inspection, and void inspection may be performed in parallel.
[0065] Returning to Figure 3, once the determination process S108 for the currently selected inspection window is completed, the inspection unit 42 of the control unit 10 determines whether there is a next inspection window in the currently selected imaging area (field of view FOV) (step S110). If it determines that there is a next inspection window (step S110:Y), it returns to step S106 to select the next inspection window and repeats the determination process. Meanwhile, if the inspection unit 42 of the control unit 10 determines that it has performed the determination process for all inspection windows (step S110:N), the imaging processing unit 36 of the control unit 10 determines whether there is a next imaging area (field of view FOV) (step S112). If it determines that there is a next imaging area (step S112:Y), it returns to step S102 to select the next imaging area (field of view FOV) and repeats the image acquisition and determination process. On the other hand, if the imaging processing unit 36 of the control unit 10 determines that there is no next imaging area (field of view) (step S112:N), it terminates the inspection process, moves the holding unit 24 to the unloading position, unloads the object to be inspected 12 from the inspection device 1 (step S114), and terminates the inspection of the object to be inspected 12. The control unit 10 may also be configured to display (output) pseudo-cross-sectional image data (seamless cross-sectional image data including inspection surface image data) including the abnormal area on the monitor 11, which is the display unit, if it determines that the solder joint state is abnormal in any of the inspection windows described above.
[0066] As mentioned above, image acquisition and judgment processing may be performed for each imaging area (field of view), or the inspection may be performed sequentially from the imaging area (FOV) where the generation of reconstructed image data (cross-sectional image data and pseudo-cross-sectional image data) has been completed, in parallel with the acquisition of transmission image data and generation of reconstructed image data for other imaging areas (FOV).
[0067] As described above, the inspection apparatus 1 according to the first embodiment is configured to acquire height information of the substrate inspection surface of the object to be inspected 12 held by the holding unit 24 using the substrate inspection surface height detection unit 32, calculate the amount of deviation from the reference surface (the substrate inspection surface in an ideal state) based on this information, and generate reconstructed image data (pseudo-cross-sectional image data), which is three-dimensional image data, by generating cross-sectional image data (inspection surface image data) along the substrate inspection surface and cross-sectional image data of a surface parallel to the substrate inspection surface based on this amount of deviation. With this configuration, the cross-sectional image data that constitutes the reconstructed image data, which is three-dimensional image data, includes image data of the substrate inspection surface of the object to be inspected 12 (inspection surface image data), so that inspection can be performed using seamless image data of the substrate inspection surface, thereby improving inspection accuracy.
[0068] (Second Embodiment) In the first embodiment described above, the position information of the substrate inspection surface of the object to be inspected 12 is acquired by the substrate inspection surface height detection unit 32, and the amount of deviation of the substrate inspection surface from the reference surface is calculated from this position information. In the second embodiment, a configuration is described in which reconstructed image data is generated using transmission image data, and the amount of deviation is calculated from this reconstructed image data.
[0069] Figure 8 shows the configuration of the inspection device 1' according to the second embodiment, which does not have the substrate inspection surface height detection unit 32 described in the first embodiment. The other components are the same as in the first embodiment, so the same reference numerals are used and detailed descriptions are omitted. Furthermore, the configuration of the control unit of the inspection device 1' according to the second embodiment is the same as in the first embodiment shown in Figure 2.
[0070] In the inspection apparatus 1' according to this second embodiment, a method for inspecting an object to be inspected, including a method for calculating the amount of deviation of the substrate inspection surface of the object to be inspected 12 from the reference surface, will be described. Note that the same reference numerals are used for the same processes as in the first embodiment, and detailed explanations are omitted.
[0071] As shown in Figure 9, when the inspection of the object to be inspected 12 is started, the control unit 10 brings the object to be inspected 12 into the inspection device 1' (step S100), sets the imaging area (step S102), and executes transmission image acquisition and reconstruction image generation processing (step S104a).
[0072] As shown in Figure 10(a), in the transmission image acquisition and reconstruction image generation process S104a, the imaging processing unit 36 of the control unit 10 starts the holding unit 24 and the detection unit 26 and moves them along rotational trajectories (holding unit rotational trajectory 28 and detector rotational trajectory 30), acquires transmission image data at preset imaging positions, and stops the holding unit 24 and the detector 26 in the retracted position once transmission image data has been acquired at all imaging positions (step S1042). Then, once the transmission image data has been acquired, the control unit 10 executes the displacement amount calculation process (step S1043a).
[0073] As shown in Figure 10(b), in the displacement amount calculation process S1043a, the control unit 10 first generates reconstructed image data by using the cross-sectional image generation unit 36 to generate cross-sectional image data of a plane parallel to the Z-axis direction, that is, the reference plane S shown in Figure 7 and a plane parallel to this reference plane S, using the transmission image data (step S10431). The method for generating the reconstructed image data is the same as the method for generating the pseudo-cross-sectional image data in the first embodiment. Furthermore, since this reconstructed image data (cross-sectional image data) is used to calculate the displacement amount of the substrate inspection surface, as will be described later, it is sufficient to generate it within a predetermined range that includes the substrate inspection surface in the Z-axis direction.
[0074] Next, the substrate inspection surface displacement calculation unit 38 of the control unit 10 uses the reconstructed image data (cross-sectional image data) generated in step S10431 to identify the position of the substrate inspection surface in the Z-axis direction and acquire its height information (step S10432). For example, as shown in Figure 6, the currently selected imaging area R is divided into four sub-regions R1 to R4, and in each of the sub-regions R1 to R4, the similarity is calculated by comparing each cross-sectional image data with the reference image data (cross-sectional image data of the substrate inspection surface of a normal object to be inspected 12 with no abnormalities in the solder joint state, etc.), and based on the location with the highest similarity, the cross-sectional image data that best matches the reference image data is identified as the inspection surface image data, and the Z-direction position of the best-matching cross-sectional image data is stored in the storage unit 34 as the Z-direction position of the substrate inspection surface in that sub-region. As a method for identifying the cross-sectional image data that best matches the reference image data from among the cross-sectional image data, for example, template matching or the phase correlation method (phase-limited correlation method) can be used to identify the inspection surface image data at high speed with a high agreement rate regardless of positional displacement. Furthermore, a reference point is determined for each subregion R1 to R4, and the X-axis and Y-axis positions of the reference point in the identified cross-sectional image data are determined (the Z-axis position of the reference point is the Z-axis position of the identified cross-sectional image data).
[0075] Based on the positions of the reference points in the X-axis, Y-axis, and Z-axis directions in each of the sub-regions R1 to R4 constituting the imaging region R, which have been identified as described above, the amount of displacement of each point (the amount of displacement of the substrate inspection surface from the reference surface) is calculated and stored in the storage unit 34 (step S10433). The method for calculating the amount of displacement from the height information of the substrate inspection surface is as described in the first embodiment.
[0076] Returning to Figure 10(a), once the amount of deviation of the substrate inspection surface from the reference surface is calculated as described above, the pseudo-cross-sectional image generation unit 40 generates reconstructed image data (pseudo-cross-sectional image data) by generating cross-sectional image data of the substrate inspection surface and the surface parallel to the substrate inspection surface based on the reference surface, the surface parallel to the reference surface, and the amount of deviation, and terminates the transmission image acquisition and reconstruction image generation process S104a (step S1044). The method for generating cross-sectional image data of the substrate inspection surface and the surface parallel to the substrate inspection surface is as described in the first embodiment.
[0077] Returning to Figure 9, once the reconstructed image data (cross-sectional image data) and pseudo-cross-sectional image data are generated, one of the inspection windows set in the currently selected imaging region (field of view) is selected (step S106), and the inspection process described above is performed on that inspection window (step S108). Then, it is determined whether all inspection windows have been selected and the inspection has been performed (step S110). If the inspection has been performed on all inspection windows, it is determined whether there is another imaging region (step S112). When the inspection of all imaging regions has been completed, the object to be inspected 12 is removed from the inspection device 1' (step S114), and the inspection process is terminated.
[0078] As described above, in the inspection apparatus 1' according to the second embodiment, in order to calculate the amount of deviation of the substrate inspection surface of the object to be inspected 12 from the reference surface, no special function such as the substrate inspection surface height detection unit 32 described in the first embodiment is required. Cross-sectional image data (reconstructed image data) of a predetermined area including the substrate inspection surface is generated from the captured transmission image data, the substrate inspection surface can be identified from these cross-sectional image data, and furthermore, the amount of deviation can be calculated from this identified substrate inspection surface. Therefore, even with an inspection apparatus with a conventional configuration, for example, even if the object to be inspected 12 is warped, bent, or tilted, cross-sectional image data along the substrate inspection surface can be generated, and inspection can be performed using seamless inspection surface image data, thereby improving the accuracy of the inspection.
[0079] (Main Effects) The main features and effects of the image data generation method in the inspection apparatus according to the above embodiment are shown below.
[0080] Firstly, according to the image data generation method of this embodiment, the cross-sectional image data constituting the reconstructed image data, which is three-dimensional image data, can be cross-sectional image data along the substrate inspection surface of the object under inspection 12, rather than cross-sectional image data of a plane perpendicular to the axis A, i.e., the Z-axis direction, that passes through the focal point of the radiation generator 22 (reference plane and plane parallel to this reference plane). Therefore, even if the substrate of the object under inspection 12 is warped, bent, or tilted, and the substrate inspection surface is misaligned with the reference plane, inspection can be performed using seamless inspection image data.
[0081] Figure 11 shows a case where an electronic component 12b is bonded to the upper surface (substrate inspection surface S') of the substrate 12a of the object under inspection 12 via solder balls, and the substrate inspection surface S' is held in a tilted state (not orthogonal) with respect to the axis A (Z-axis direction) passing through the focal point of the radiation generator 22. In conventional methods, when cross-sectional image data is generated as image data of a plane orthogonal to axis A (Z-axis direction), if the substrate 12a is warped, bent, or tilted, as shown in Figure 11(a), it is necessary to generate cross-sectional image data that includes the substrate inspection surface S' and solder balls within the imaging area (FOV). As a result, the range W1 for generating cross-sectional image data (range in the Z-axis direction) becomes wider, and consequently, the number of cross-sectional image data images to be generated increases, and the processing time and computational load for generating reconstructed image data (pseudo-cross-sectional image data) increases. Furthermore, since it is necessary to cut out the portion of the substrate inspection surface S' that spans multiple cross-sectional image data and join them together to generate inspection surface image data, additional processing time and computational load are required. On the other hand, in the image data generation method according to this embodiment, since cross-sectional image data is generated along the substrate inspection surface S', as shown in Figure 11(b), the range W2 for generating cross-sectional image data (the range including the substrate inspection surface S' and solder balls) is narrower than W1. As a result, the number of cross-sectional image data to be generated is reduced, and cutting and splicing processes are unnecessary. Therefore, the processing time and computational load for generating reconstructed image data (pseudo-cross-sectional image data) including inspection surface image data are reduced.
[0082] Secondly, the image data generation method according to this embodiment is configured to generate the pixel values of the cross-sectional image from the pixel values of the transmitted image data using a filter-corrected back projection method or a successive approximation method. Therefore, cross-sectional image data along the substrate inspection surface of the object to be inspected 12 can be generated using a known method.
[0083] Thirdly, in the image data generation method according to this embodiment, the amount of deviation of the substrate inspection surface from the reference surface is calculated based on the positional information of multiple locations within the imaging area, and the amount of deviation at other locations is calculated by interpolation. Therefore, it is not necessary to determine the amount of deviation for all pixels within the imaging area, and cross-sectional image data along the substrate inspection surface of the object to be inspected 12 can be generated with less processing.
[0084] Fourth, in the image data generation method according to this embodiment, positional information including the amount of displacement is managed as coordinate data in three-dimensional space. Therefore, the position of the substrate of the object to be inspected 12 due to warping, bending, and tilting can be managed not only in the Z-axis direction but also in the X-axis and Y-axis directions, making it possible to generate cross-sectional image data with higher accuracy.
[0085] Fifth, in the image data generation method according to this embodiment, by providing a substrate inspection surface height detection unit 32 that acquires positional information (amount of displacement) of the substrate inspection surface by irradiating the substrate inspection surface of the object to be inspected 12 with laser light and detecting the reflected light of the laser light, the amount of displacement can be measured more accurately, and cross-sectional image data with higher accuracy can be generated.
[0086] Sixth, in the image data generation method according to this embodiment, the similarity between the cross-sectional image data generated from the transmission image data, which is parallel to the reference plane, and the reference image data is calculated using template matching or a phase correlation method. Based on the locations with high similarity, the positional information (amount of displacement) of the substrate inspection surface is calculated. This eliminates the need for a function like the substrate inspection surface height detection unit 32 described above, and allows for the generation of cross-sectional image data along the substrate inspection surface of the object to be inspected 12 using a conventional inspection device.
[0087] 1,1' Inspection device 10 Control unit 11 Monitor (display unit) 12 Object to be inspected 22 Radiation generator (light source) 24 Holding unit 26 Detector 32 Substrate inspection surface height detection unit
Claims
1. A method for generating cross-sectional image data, wherein two of the light source, detector, and holding part that holds the object to be inspected are rotated in a plane parallel to each other, and the light emitted from the light source and transmitted through the object to be inspected is detected by the detector, and the method generates cross-sectional image data of the object to be inspected using at least two transmitted image data acquired at different positions in the plane, wherein the method generates pixel values of the cross-sectional image data of the substrate inspection surface from the pixel values of the position information corrected based on the position information of the substrate inspection surface of the object to be inspected in the transmitted image data.
2. The method for generating image data according to claim 1, wherein the pixel values of the cross-sectional image are generated from the pixel values of the transmitted image data by a filter-corrected back projection method or a successive approximation method.
3. The method for generating image data according to claim 1, wherein positional information of multiple locations on the substrate inspection surface of the object to be inspected is acquired, and positional information for each pixel of the cross-sectional image data is calculated from the positional information of the multiple locations by interpolation.
4. The method for generating image data according to claim 1, wherein the position information is managed as coordinate data in three-dimensional space.
5. The method for generating image data according to claim 1, wherein the position information is obtained by irradiating the substrate inspection surface of the object to be inspected with laser light and detecting the reflected light of the laser light.
6. The method for generating image data according to claim 1, wherein the position information is calculated based on the location of the location in the image data, which is determined by acquiring image data of the substrate inspection surface of the object to be inspected, calculating the similarity between the image data and reference image data by template matching or phase correlation method, and then calculating the position information based on the location of the location in the image data from the reference image data.
7. An inspection apparatus comprising: a light source; a detector; a holding unit for holding an object to be inspected; a substrate inspection surface height detection unit for detecting positional information of the substrate inspection surface of the object to be inspected; and a control unit that rotates two of the light source, the detector, and the holding unit in a plane parallel to each other, and generates a cross-sectional image data of the object to be inspected using at least two transmitted image data obtained at different positions in the plane, wherein the control unit generates and holds a cross-sectional image data of the substrate inspection surface based on the positional information of the substrate inspection surface detected by the substrate inspection surface height detection unit using the image data generation method described in any one of claims 1 to 6.
8. The inspection apparatus according to claim 7, comprising a display unit, wherein the control unit outputs seamless cross-sectional image data generated by the control unit to the display unit for the bent object under inspection.