Inspection equipment

Abstract

To provide an inspection device which can calculate a deviation amount from a prescribed reference surface of an inspection object surface of an inspection object without having a configuration of detecting a position of the inspection object.SOLUTION: An inspection device 1 comprises: a radiation generator 22; a substrate holding part 24 which holds an inspection object 2; a detector 26; drive parts 16, 18, 20 which change relative positions between the inspection object 2 and the detector 26 held by the radiation generator 22 and the substrate holding part 24; and a control part 10. The control part 10, when the inspection object 2 and the detector 26 held by the radiation generator 22 and the substrate holding part 24 are in prescribed relative positions, detects a deviation amount from a prescribed reference surface of an inspection object surface of the inspection object 2 on the basis of at least one transmission image of the inspection object 2 detected and acquired by the detector 26.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an inspection apparatus.

Background Art

[0002] As an inspection apparatus for measuring the solder shape on the front and back surfaces of a substrate, there is a tomosynthesis type X-ray inspection apparatus (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such an inspection apparatus, a plurality of transmission images are captured by changing the relative positions of the radiation source (radiation generator), the object to be inspected (for example, an electronic substrate), and the detector, and these transmission images are reconstructed to generate a cross-sectional image of the object to be inspected. Further, in such an inspection apparatus, in order to shorten the inspection time and the like, the transmission image is captured while changing the relative positions of the radiation source, the object to be inspected, and the detector. However, when the transmission image is captured while changing the relative positions of the radiation source, the object to be inspected, and the detector, depending on the position of the object to be inspected, so-called motion blur occurs in the image, and the inspection accuracy decreases. For example, when the object to be inspected is an electronic substrate, due to distortion such as warping and bending, the surface of the object to be inspected to be inspected (hereinafter referred to as the "inspection target surface") may be out of the range where no blur occurs (this range is referred to as the "aiming region"), and blur may occur in the transmission image.

[0005] To prevent blurring of such transmitted images, inspection devices have been put into practical use that are equipped with measuring instruments to measure the position on the object being inspected, detect the position of the object being inspected with these measuring instruments, and adjust the inspection surface of the object being inspected so that it approximately coincides with a predetermined reference surface set up within the aiming area, for example, within the aiming area. However, there are issues such as the extra cost required to install the measuring instruments, and the fact that the measuring instruments are also irradiated with radiation, which necessitates checking for deterioration due to radiation exposure and performing replacement work.

[0006] The present invention has been made in view of these problems, and aims to provide an inspection device that can calculate the amount of deviation of the inspection target surface of an object to be inspected from a predetermined reference surface without providing a configuration for detecting the position of the object to be inspected. [Means for solving the problem]

[0007] To solve the above problems, the inspection apparatus according to the present invention comprises a radiation source, a holding unit for holding an object to be inspected, a detector, a drive unit for changing the relative position of the radiation source, the object to be inspected held by the holding unit, and the detector, and a control unit, wherein the control unit, when the radiation source, the object to be inspected held by the holding unit, and the detector are in a predetermined relative position by the drive unit, detects the radiation emitted from the radiation source and transmitted through the object to be inspected with the detector and obtains one transmitted image of the object to be inspected, and the object to be inspected at the predetermined relative position Surface to be inspected but Predetermined reference surface The same feature shape in the reference image, which is a transparent image when the subject is in a certain position, is detected by the phase-limited correlation method, and the difference in the magnification of the feature shape is used to determine the object under inspection. The aforementioned Surface to be inspected The aforementioned The amount of deviation from a predetermined reference plane is detected.

[0008] Furthermore, the inspection apparatus according to the present invention comprises a radiation source, a holding unit for holding an object to be inspected, a detector, a drive unit for changing the relative position between the radiation source, the object to be inspected held by the holding unit, and the detector, and a control unit, wherein the control unit, when the radiation source, the object to be inspected held by the holding unit, and the detector are in a predetermined relative position by the drive unit, detects the radiation emitted from the radiation source and transmitted through the object to be inspected with the detector and obtains one transmitted image of the object to be inspected, and the object to be inspected at the predetermined relative position Surface to be inspected but Predetermined reference surface The same feature shape in the reference image, which is a transparent image when the subject is in a certain position, is detected by feature matching, and the difference in the magnification of the feature shape is used to determine the object under inspection. The aforementioned Surface to be inspected The aforementioned The amount of deviation from a predetermined reference plane is detected.

[0009] Also, The inspection apparatus according to the present invention comprises a radiation source, a holding unit for holding an object to be inspected, a detector, a drive unit for changing the relative position between the radiation source, the object to be inspected held by the holding unit, and the detector, and a control unit, wherein the control unit detects the radiation emitted from the radiation source and transmitted through the object to be inspected by the detector when the radiation source, the object to be inspected held by the holding unit, and the detector are in a predetermined relative position as determined by the drive unit, and obtains a transmitted image of the object to be inspected. The method involves acquiring two or more transmission images when the radiation source, the object to be inspected held by the holding unit, and the detector are in different positions, reconstructing the two or more transmission images to generate a cross-sectional image of the object to be inspected, and using the cross-sectional image. The amount of deviation of the surface of the object to be inspected from a predetermined reference plane is detected.

[0010] Furthermore, in the inspection apparatus according to the present invention, it is preferable that the control unit determines the cross-sectional image that best matches the reference image of the cross-sectional images from among the cross-sectional images, and detects the amount of displacement from the position of the said cross-sectional image.

[0011] Furthermore, in the inspection apparatus according to the present invention, it is preferable that the control unit identifies the cross-sectional image that best matches the reference image of the cross-sectional images from among the cross-sectional images using the phase-limited correlation method, and detects the amount of displacement from the position of the said cross-sectional image.

[0012] Furthermore, in the inspection apparatus according to the present invention, it is preferable that the control unit detects the amount of displacement at multiple positions on the object to be inspected, and calculates the amount of displacement at positions where the amount of displacement has not been detected by linear interpolation using the detected amount of displacement.

[0013] Furthermore, in the inspection apparatus according to the present invention, it is preferable that the control unit performs linear interpolation using the values ​​of positions where the displacement is known, in addition to the detected displacement, when calculating the displacement at positions where the displacement has not been detected.

[0016] Furthermore, in the inspection apparatus according to the present invention, the control unit is the Subject under inspection Preferably, for each position where the above transmission image is acquired, a correction value is calculated from the amount of displacement relative to the position of the predetermined reference plane, the relative position of the radiation source, the object to be inspected held by the holding unit, and the detector is corrected based on the correction value, and the transmission image is acquired at the predetermined relative position while the relative position of the radiation source, the object to be inspected held by the holding unit, and the detector is changed by the drive unit based on the corrected relative position. [Effects of the Invention]

[0017] According to the inspection device of the present invention, it is possible to provide an inspection device that can calculate the amount of deviation of the surface of an object to be inspected from a predetermined reference plane without providing a configuration for detecting the position of the object to be inspected. [Brief explanation of the drawing]

[0018] [Figure 1] This is an explanatory diagram illustrating the configuration of the inspection apparatus according to this embodiment. [Figure 2] This is an explanatory diagram illustrating each functional block processed by the control unit of the inspection device described above. [Figure 3] This is a flowchart to explain the inspection process. [Figure 4] This is a flowchart illustrating the process of acquiring transmission images and generating reconstructed images. [Figure 5]It is an explanatory diagram for explaining the movement of the substrate holding unit and the detector, and the timing of X-ray radiation from the radiation generator and imaging by the detector. (a) shows a timing chart, and (b) shows the timing of exposure. [Figure 6] It is an explanatory diagram schematically showing the configuration of the inspection device as viewed from the side. [Figure 7] It is a flowchart for explaining the processing of the first correction method. [Figure 8] It is a flowchart for explaining the processing of the second correction method.

Mode for Carrying Out the Invention

[0019] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the inspection device 1 according to the present embodiment includes a control unit 10 configured by a processing device such as a personal computer (PC), a monitor 12, and an imaging unit 32. Further, the imaging unit 32 further includes a quality changing unit 14, a radiation generator driving unit 16, a substrate holding unit driving unit 18, a detector driving unit 20, a radiation generator 22, a substrate holding unit 24, and a detector 26.

[0020] The radiation generator 22 is a device (radiation source) that generates radiation such as X-rays. For example, it generates radiation by colliding accelerated electrons with a target such as tungsten or diamond. In the present embodiment, the radiation is described for the case of X-rays, but it is not limited thereto. For example, the radiation may be alpha rays, beta rays, gamma rays, ultraviolet rays, visible light, infrared rays. Further, the radiation may be microwaves or terahertz waves.

[0021] The substrate holder 24 holds the substrate, which is the object to be inspected. Radiation generated by the radiation generator 22 is irradiated onto the object to be inspected held by the substrate holder 24, and the radiation that passes through the object to be inspected is detected by the detector 26 and captured as an image. Hereinafter, the radiation-transmitted image of the object to be inspected captured by the detector 26 will be called a "transmitted image". As will be described later, in this embodiment, the substrate holder 24 holding the substrate to be inspected and the detector 26 are moved relative to the radiation generator 22 to acquire multiple transmitted images and generate a reconstructed image (cross-sectional image).

[0022] The transmission image captured by the detector 26 is sent to the control unit 10, where it is reconstructed into an image including the three-dimensional shape of the solder joint using a known technique such as the filtered-backprojection method (FBP method). The reconstructed image and the transmission image are then stored in the storage within the control unit 10 or in external storage (not shown). Hereinafter, the image reconstructed into a three-dimensional image including the three-dimensional shape of the solder joint based on the transmission image will be called the "reconstructed image." An image obtained by cutting out an arbitrary cross-section from the reconstructed image will be called a "cross-sectional image." Such reconstructed images and cross-sectional images are output to the monitor 12. In addition to the reconstructed images and cross-sectional images, the monitor 12 also displays inspection results of the solder joint state, which will be described later. Furthermore, as mentioned above, the reconstructed image in this embodiment is reconstructed from a planar image (transmission image) captured by the detector 26, and is therefore also called a "planar CT."

[0023] 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.

[0024] Here, the quality of radiation is determined by its brightness and hardness (spectral distribution). Increasing the tube current increases the number of electrons that collide with the target, and thus the number of photons produced. 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 radiation of high brightness. 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 produced 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.

[0025] The radiation generator drive unit 16 has a drive mechanism such as a motor (not shown) that can move the radiation generator 22 up and down along axis A (the axis (optical axis) passing through the center of the radiation direction of the radiation emitted from the radiation generator 22, and the direction of this axis is defined as the "Z-axis direction") that passes through its focal point. 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) held by the substrate 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 generator position detection unit 23 and output to the control unit 10.

[0026] The detector drive unit 20 also has a drive mechanism such as a motor (not shown) that rotates the detector 26 along the detector rotation trajectory 30. The substrate holder drive unit 18 also has a drive mechanism such as a motor (not shown) that moves the substrate holder 24 in parallel on a plane on which the substrate rotation trajectory 28 is provided. The substrate holder 24 is configured to rotate along the substrate rotation trajectory 28 in conjunction with the rotational movement of the detector 26. This makes it possible to capture multiple transmission images with different projection directions and projection angles while changing the relative positional relationship between the substrate held by the substrate holder 24 and the radiation generator 22.

[0027] Here, the rotation radii of the substrate 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 components placed on the substrate, which is the object under inspection. The orbital planes of the substrate rotation trajectory 28 and the detector rotation trajectory 30 are perpendicular to the Z-axis direction as described above. If the directions perpendicular to these orbital planes are considered to be the X-axis direction and the Y-axis direction, the positions of the substrate 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.

[0028] The control unit 10 controls all operations of the inspection device 1 described above. The 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.

[0029] The control unit 10 includes a storage unit 34, an imaging processing unit 35, a cross-sectional image generation unit 36, a substrate inspection surface detection unit 38, a pseudo-cross-sectional image generation unit 40, and an inspection unit 42. Although not shown, the imaging processing unit 35 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 radiation generator drive unit 16, the substrate holding unit drive unit 18, and the detector drive 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.

[0030] The memory unit 34 stores information such as imaging conditions for capturing a transmission image of the substrate and the design of the substrate being inspected. The memory unit 34 also stores the transmission image and reconstructed image (cross-sectional image, pseudo-cross-sectional image) of the substrate, as well as the inspection results of the inspection unit 42, which will be described later. The memory unit 34 also stores information for driving the radiation generator drive unit 16, the substrate holding unit drive unit 18, and the detector drive unit 20 (for example, the speed at which the radiation generator drive unit 16 drives the radiation generator 22, the speed at which the substrate holding unit drive unit 18 drives the substrate holding unit 24, and the speed at which the detector drive unit 20 drives the detector 26, etc.).

[0031] The imaging processing unit 35 drives the radiation generator 22, substrate holder 24, and detector 26 using the radiation generator drive unit 16, substrate holder drive unit 18, and detector drive unit 20 to capture a transmission image of the object under inspection held by the substrate holder 24, and generates a reconstructed image (cross-sectional image) from the transmission image. The method of capturing the transmission image and generating the reconstructed image (cross-sectional image) by the imaging processing unit 35 will be described later.

[0032] The cross-sectional image generation unit 36 ​​generates a cross-sectional image based on multiple transmission images acquired from the storage unit 34. This can be achieved using known techniques such as the FBP method or the maximum likelihood estimation method. Different reconstruction algorithms result in different properties of the reconstructed image and different reconstruction times. Therefore, it is possible to prepare multiple reconstruction algorithms and the parameters used in the algorithms in advance and allow the user to select one. This provides the user with the freedom to choose whether to prioritize a shorter reconstruction time or to prioritize high image quality even if it takes longer. Each of the generated cross-sectional images is output to the storage unit 34 along with attribute information such as the position in the Z-axis direction of each cross-sectional image and the position (coordinate) of pixels in the X-axis and Y-axis directions within the cross-sectional image, and is stored in the storage unit 34.

[0033] The substrate inspection surface detection unit 38 identifies the position (cross-sectional image) that shows the surface on the substrate to be inspected (for example, the surface of the substrate) from among the multiple cross-sectional images generated by the cross-sectional image generation unit 36. Hereafter, the cross-sectional image showing the inspection surface of the substrate will be referred to as the "inspection surface image".

[0034] The pseudo-cross-sectional image generation unit 40 visualizes a region of the substrate thicker than the cross-sectional image by stacking a predetermined number of consecutive cross-sectional images generated by the cross-sectional image generation unit 36. The number of cross-sectional images to stack is determined by the thickness of the substrate region shown in the cross-sectional image (hereinafter referred to as "slice thickness") and the slice thickness of the pseudo-cross-sectional image. For example, if the slice thickness of the cross-sectional image is 50 μm, and the slice thickness of the pseudo-cross-sectional image is to be the height of a BGA solder ball (hereinafter simply referred to as "solder") (for example, 500 μm), then 500 / 50 = 10 cross-sectional images should be stacked. In this case, the inspection surface image identified by the substrate inspection surface detection unit 38 is used to identify the position of the solder.

[0035] The inspection unit 42 inspects the solder bonding state based on the cross-sectional image generated by the cross-sectional image generation unit 36, the inspection surface image identified by the substrate inspection surface detection unit 38, and the pseudo-cross-sectional image generated by the pseudo-cross-sectional image generation unit 40. Since the solder that bonds the substrate and the component is located near the substrate inspection surface, it is possible to determine whether the solder is properly bonding the substrate and the component by inspecting the inspection surface image and the cross-sectional image that shows the area on the radiation generator 22 side relative to the inspection surface image.

[0036] 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.

[0037] The detailed operation of 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 the pseudo-cross-sectional image generated by the pseudo-cross-sectional image generation unit 40, and the molten state inspection unit 46 inspects the molten state of the solder based on the inspection surface image identified by the substrate inspection surface detection unit 38. 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.

[0038] Figure 3 is a flowchart showing the flow from capturing a transmission image and generating a reconstructed image (cross-sectional image), to identifying the inspection surface image, and inspecting the solder joint state. Figure 4 is a flowchart showing the flow of the part of the process that involves capturing a transmission image and generating a reconstructed image (cross-sectional image). 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).

[0039] When the inspection begins, the control unit 10 first performs a calculation process for a correction value of the aiming height to determine the position of the radiation generator 22 in the Z-axis direction, as shown in Figure 3 (step S100). The calculation process for the aiming height and the correction of the aiming height will be described later. Once the correction value of the aiming height is calculated, the control unit 10 sets the irradiation field of the radiation emitted by the radiation generator 22 using the radiation generator drive unit 16, moves the substrate holder 24 using the substrate holder drive unit 18, and moves the detector 26 using the detector drive unit 20 to change the imaging position, while setting the beam quality of the radiation generator 22 using the beam quality change unit 14 and irradiating the substrate with radiation to capture a transmission image. Furthermore, from the multiple transmission images captured in this way, the cross-sectional image generation unit 36 ​​and the pseudo-cross-sectional image generation unit 40 generate a reconstructed image (step S101). Furthermore, the movement path of the substrate holder 24 by the substrate holder drive unit 18 and the movement path of the detector 26 by the detector drive unit 20 when capturing a transmission image are pre-set in the substrate holder drive unit 18 and the detector drive unit 20 by reading information stored in the memory unit 34 or by inputting it from an input device. Similarly, the position of the radiation generator 22 in the Z-axis direction is also pre-set in the radiation generator drive unit 16 by the same method.

[0040] The details of the process in step S101 will be explained with reference to Figures 4 and 5. In the inspection apparatus 10 according to this embodiment, for the inspection of an object to be inspected, multiple inspection areas are provided, including the area to be inspected on the object to be inspected. The apparatus is configured to acquire a transmission image and generate a reconstructed image (cross-sectional image, etc.) using this transmission image for each inspection area. In the following explanation, each inspection area will be referred to as the imaging area (FOV), and the processes shown in Figures 4 and 5 will be performed for each imaging area.

[0041] As shown in Figure 4, when step S100 begins, the imaging processing unit 35 of the control unit 10 transmits signals corresponding to the initial positions to the radiation generator drive unit 16, the substrate holder drive unit 18, and the detector drive unit 20 in order to move the radiation generator 22, the substrate holder 24, and the detector 26 to the initial positions corresponding to the current imaging area (step S1000). The control unit 10 corrects the preset aiming height to the radiation generator drive unit 16 based on the correction value calculated in the aiming height correction value calculation process (step S100) described later, and transmits a signal indicating the position of the radiation generator 22 in the Z direction so that the reference plane (details described later) is positioned at this corrected aiming height. Furthermore, since the movement paths of the substrate holder 24 and the detector 26 are preset as described above, the control unit 10 transmits signals indicating their initial positions to the substrate holder drive unit 18 and the detector drive unit 20. Upon receiving this signal, the radiation generator drive unit 16, the substrate holder drive unit 18, and the detector drive unit 20 each move the radiation generator 22, the substrate holder 24, and the detector 26 to their respective initial positions based on the signal (steps S1002, S1004, S1006).

[0042] Next, the control unit 10 turns on the operating signals output to the substrate holder drive unit 18 and the detector drive unit 20 (step S1008). This corresponds to time t0 in Figure 5(a). When this operating signal is turned on, the substrate holder drive unit 18 starts moving the substrate holder 24 (step S1010), and the detector drive unit 20 starts moving the detector 26 (step S1012). The substrate holder 24 and the detector 26 are moved along the preset movement path as described above.

[0043] The imaging processing unit 35 determines whether or not it is time to take an image (step S1014). If it determines that it is not time to take an image ("N" in step S1014), it repeats this step after a predetermined time interval. If it determines that it is time to take an image ("Y" in step S1014), it sends an imaging start signal (trigger) to the detector 26 (step S1016). For example, in the example in Figure 5(a), the trigger for the detector 26 is turned on at time t1.

[0044] Upon detecting that the trigger has been turned on by the imaging processing unit 35, the detector 26 starts capturing a transmission image and sends a response signal to the imaging processing unit 35 indicating that imaging has started (step S1018). The detector 26 also sends an exposure signal to the radiation generator drive unit 16 (step S1020). For example, in the example shown in Figure 5(a), the exposure signal output to the radiation generator drive unit 16 is turned on from time t2 to time T. By configuring the detector 26 to send the exposure signal to the radiation generator drive unit 16 in this way, the delay from the start of imaging to the start of exposure can be minimized.

[0045] Upon receiving an exposure signal from the detector 26, the radiation generator drive unit 16 generates radiation from the radiation generator 22 while the exposure signal is ON, and this radiation irradiates the object under inspection (step S1022). Here, if the detector 26 employs a rolling shutter method, the X-ray information (intensity, etc.) detected by the photodetector element of the detector 26 is acquired along multiple scanning lines arranged in a predetermined direction, but the start time is shifted for each scanning line. For example, as shown in Figure 5(b), if the detector 26 is composed of n scanning lines extending in the left-right direction, the detected information is acquired in the order of D1, D2, D3, ..., Dn-1, Dn from top to bottom, with shifted start times. Therefore, by generating X-rays from the radiation generator 22 during the time when all scanning lines are acquiring data (during time T in Figure 5(b)), the information obtained from each scanning line becomes information from X-rays irradiated at the same time, thus preventing distortion of the acquired transmission image.

[0046] Furthermore, the imaging processing unit 35, upon receiving the response signal transmitted from the detector 26, acquires position information of the substrate holding unit 24 from the substrate position detection unit 29 and acquires and stores the position of the detector 26 from the detector position detection unit 31 (step S1024). Note that the movement of the substrate holding unit 24 by the substrate holding unit drive unit 18 and the movement of the detector 26 by the detector drive unit 20 are controlled along predetermined movement paths as described above. Therefore, if either the position of the substrate holding unit 24 or the position of the detector 26 is known, the position of the other can also be known. Thus, the positions of both the substrate holding unit 24 and the detector 26 may be stored, or the position of either one may be stored. In addition, the positions of the substrate holding unit 24 and the detector 26 may be stored in the XY Cartesian coordinate system (in the form of position (x,y) in the X-axis direction and Y-axis direction), or they may be stored in polar coordinates (in the form of position (r,θ) specified by distance r from the origin and angle θ) with the center of the orbital plane of the substrate rotation orbit 28 and the detector rotation orbit 30 as the origin.

[0047] Once the acquisition of the transmission image is complete, the detector 26 transmits the acquired transmission image to the imaging processing unit 35 (step S1026). The imaging processing unit 35 then stores the acquired transmission image in the storage unit 34, associating it with the position information of the substrate holding unit 24 and the position information of the detector 26 acquired in step S1024 (step S1028).

[0048] Furthermore, the imaging processing unit 35 determines whether or not there is a next imaging position (step S1030). If it determines that there is a next imaging position ("Y" in step S1030), it returns to step S1014 and repeats the above-described process (steps S1014 to S1028). On the other hand, if the imaging processing unit 35 determines that there is no next imaging position ("N" in step S1030), it turns off the operating signals output to the substrate holding unit drive unit 18 and the detector drive unit 20 (step S1032). The substrate holding unit drive unit 18, detecting that the operating signals have been turned off, stops the movement of the substrate holding unit 24 (step S1034), and the detector drive unit 20 stops the movement of the detector 26 (step S1036). For example, this corresponds to time t3 in Figure 5(a).

[0049] Finally, the imaging processing unit 35 generates a reconstructed image (cross-sectional image) from the transmission image stored in the storage unit 34 using the cross-sectional image generation unit 36 ​​and the pseudo-cross-sectional image generation unit 40 (step S1038). The generated reconstructed image (cross-sectional image) may be stored in the storage unit 34. The control unit 10 then determines whether there is another imaging region, and if there is, it returns to step S1000 and repeats the above processing for that imaging region. Note that the reconstructed image generation process in step S1038 may be executed in parallel with the processing for the next imaging region.

[0050] Next, returning to Figure 3, the substrate inspection surface detection unit 38 of the control unit 10 receives a transmission image or a reconstructed image (cross-sectional image) from the cross-sectional image generation unit 36 ​​and identifies the inspection surface image from there (step S102). The bridge inspection unit 44 acquires a pseudo-cross-sectional image from the pseudo-cross-sectional image generation unit 40 with a slice thickness similar to that of the solder ball that is showing the solder ball, and checks for the presence or absence of a bridge (step S104). If no bridge is detected ("N" in step S106), the melting state inspection unit 46 acquires the inspection surface image from the substrate inspection surface detection unit 38 and checks whether or not the solder is melted (step S108). If the solder is melted ("Y" in step S110), the void inspection unit 48 acquires a pseudo-cross-sectional image from the pseudo-cross-sectional image generation unit 40 that partially shows the solder ball, and checks whether or not a void exists (step S112). If no voids are found ("N" in step S114), the void inspection unit 48 determines that the solder joint is normal (step S116) and outputs this to the storage unit 34. If a bridge is detected ("Y" in step S106), if the solder is not molten ("N" in step S110), or if voids are present ("Y" in step S114), the bridge inspection unit 44, the molten state inspection unit 46, and the void inspection unit 48, respectively, determine that the solder joint is abnormal (step S118) and output this to the storage unit 34. Once the solder status is output to the storage unit 34, the processing in this flowchart is completed.

[0051] Note that the processing in steps S102 to S118 shown in Figure 3 is also performed for each imaging area as described above. Alternatively, steps S102 to S118 may be performed for each imaging area after capturing images of all imaging areas in step S101, or steps S102 to S118 may be performed sequentially as the generation of reconstructed images is completed for each imaging area, in parallel with the imaging of other imaging areas.

[0052] According to the above method, the position where the transmission image is captured is not based on the time the imaging processing unit 35 sends a trigger to the detector 26, but rather on the time the detector 26 starts acquiring the image (the time the response signal is received from the detector 26). When the relative position between the radiation generator 22, the substrate holder 24, and the detector 26 is changing (the substrate holder 24 and the detector 26 are continuously moving), a delay occurs between the time the imaging processing unit 35 sends a trigger and the time the detector 26 starts acquiring the image. Therefore, the positions of the substrate holder 24 and the detector 26 at the time the trigger is sent may differ from the actual position where the transmission image is captured. For this reason, as described above, by acquiring the positions of the substrate holder 24 and the detector 26 when the detector 26 starts acquiring the image and the imaging processing unit 35 receives the response signal transmitted from the detector 26 at that time, accurate positional information can be obtained, thereby improving the accuracy of the reconstructed image. Furthermore, the movement path of the substrate holder 24 by the substrate holder drive unit 18 and the movement path of the detector 26 by the detector drive unit 20 may deviate from a predetermined position due to the characteristics of the drive units, etc. However, as described above, these positions are detected by the substrate position detection unit 29 and the detector position detection unit 31, so accurate position information can be obtained, and the accuracy of the reconstructed image can be further improved.

[0053] Furthermore, the position information of the substrate holding unit 24 and the detector 26, as well as the transmitted image, are stored in the control unit 10's storage area (memory, hard disk, etc.) using a predetermined area cyclically (a method in which information is stored sequentially from the beginning of the predetermined area, and when information is stored at the end of the predetermined area, it returns to the beginning of the predetermined area for storage), thereby enabling efficient use of the storage area.

[0054] Furthermore, when the detector 26 is capturing a transmission image using a rolling shutter method, the image may be distorted if the relative position between the radiation generator 22, the substrate holder 24, and the detector 26 is changed while acquiring the transmission image. However, as described above, by synchronizing the on / off switching of X-rays emitted from the radiation generator 22 (on / off exposure signal) with the rolling shutter signal (response signal) of the detector 26, a distortion-free transmission image can be acquired.

[0055] Figure 6 schematically shows the configuration of the inspection device 1 as viewed from the side. The following explanation will be based on Figure 6. As described above, in the inspection device 1 according to this embodiment, the position of the radiation generator 22 is fixed, and the object to be inspected 2 and the detector 26, which are held by the substrate holding part 24, are moved in a plane perpendicular to a predetermined axis A (for example, the optical axis of the radiation generator 22) around this axis A, while acquiring a transmitted image of the object to be inspected 2 at a predetermined position. When a transmitted image is acquired while moving the object to be inspected 2 in this way, the transmitted image of the inspection target surface of the object to be inspected 2 moving within a predetermined range in the Z-axis direction is not blurred, but as it moves away from the inspection target surface, so-called "motion blur" occurs, resulting in a blurred image. At this time, the surface on which no motion blur occurs is called the "reference surface S", and the region on which motion blur occurs only at a level that does not affect the inspection is called the "targeting region". This reference plane S is determined by the distance L between the position Pf of the radiation generator 22 in the Z-axis direction and the position Pd of the detector 26 in the Z-axis direction, the rotation radius of the detector 26, and the rotation radius of the object under inspection 2 (substrate holder 24). For the sake of simplicity, in the following explanation, the plane located approximately in the center of this aiming area (the plane perpendicular to axis A) will be referred to as the "reference plane S". However, this reference plane S can be anywhere within the aiming area and is not limited to the center. Therefore, in order to perform an accurate inspection, it is necessary to move the object under inspection 2 so that the surface to be inspected (the surface perpendicular to axis A) is within this aiming area, that is, on or near the reference plane S, and acquire a transmission image.

[0056] In the inspection apparatus 1 according to this embodiment, as described above, it is necessary to set the value of the aiming height H in order to specify the position Ps of the reference plane S in the Z-axis direction relative to the inspection target surface of the object to be inspected 2. In Figure 6, the origin 0 in the Z-axis direction is shown as the surface on which the object to be inspected 2 is placed on the substrate holding part 24, but the origin can be any point within the range in which the position of the reference plane S can be identified. As described above, in the inspection of the object to be inspected 2, the position of the radiation generator 22 in the Z-axis direction is determined based on this aiming height H information, and as a result the reference plane S is at the position of aiming height H. In Figure 6, the substrate rotation trajectory 28 described above is located on a plane passing through the origin 0 and perpendicular to axis A, and the detector rotation trajectory 30 described above is located on a plane passing through position Pd and perpendicular to axis A.

[0057] Here, if the object under inspection 2 is, for example, a substrate, warping or bending may occur, and the surface to be inspected may not necessarily be located on the reference plane S specified by the aiming height H. Therefore, it is necessary to measure the position of the object under inspection 2 in the Z-axis direction for each imaging field of view (FOV) to detect the amount of deviation from the reference plane S, and to correct the aiming height H based on this amount of deviation. Two methods for detecting the amount of deviation from the reference plane S and correcting the aiming height H are described below.

[0058] (First correction method) The first correction method involves capturing one transmission image (referred to as the "detection image") for each imaging area where the amount of deviation between the inspection target surface and the reference surface S of the object under inspection 2, i.e., the correction value of the aiming height H, is to be detected. The amount of deviation is then detected by comparing the detection image with a previously captured reference transmission image (referred to as the "reference image") and detecting the difference in magnification. Here, the reference image is a transmission image captured under the same conditions as the detection image, and is a transmission image of the object under inspection 2 in which there is no distortion on the substrate surface (the reference surface S and the inspection target surface are approximately in agreement).

[0059] For example, if there is no distortion in the object under inspection 2, the reference plane S and the inspection surface of the object under inspection 2 coincide, so both the inspection image and the reference image have the same magnification. On the other hand, if the substrate surface of the object under inspection 2 is bent so as to be convex toward the radiation generator 22, the inspection surface of the object under inspection 2 is closer to the radiation generator 22, so the inspection image becomes smaller than the reference image. That is, the magnification of the inspection image becomes smaller than the magnification of the reference image. Conversely, if the inspection surface of the object under inspection 2 is bent so as to be concave toward the radiation generator 22, the substrate surface of the object under inspection 2 is further away from the radiation generator 22, so the inspection image becomes larger than the reference image. That is, the magnification of the inspection image becomes larger than the magnification of the reference image. From the above, since the amount of deviation of the aiming height H (the amount of deviation of the inspection surface relative to the reference plane S) is proportional to the magnification, the amount of deviation of the aiming height H can be determined from this difference in magnification. The magnification ratio may be the ratio of the reference size of the part to be compared (which may be a specific pattern or mark, or the outline of a component mounted on the circuit board; these are called "feature shapes") to the reference size (the ratio of the feature shape to the reference size in both the reference image and the inspection image), or it may be the ratio of the size of the comparison object (feature shape) in the inspection image to the size of the comparison object (feature shape) in the reference image, with the size of the comparison object (feature shape) in the reference image set to 1.

[0060] The calculation process for the aiming height correction value in this first correction method will be explained with reference to Figure 7. Here, the object under inspection 2 has multiple imaging fields (FOVs) set, but the imaging field for which the correction value is to be calculated is selected from among these imaging fields and stored in the storage unit 34 in advance. Similarly, a transmission image (reference image) that serves as the reference for the selected imaging field is also acquired in advance and stored in the storage unit 34. Even if the amount of deviation from the reference plane S is not detected in all imaging fields, for imaging fields where the amount of deviation has not been detected, the value can be calculated by linear interpolation using the values ​​of the imaging fields around that imaging field where the amount of deviation has been detected.

[0061] When the control unit 10 starts the calculation of the aiming height correction value in step S100, it selects one of the imaging areas of the object under inspection 2 to detect the amount of displacement, as shown in Figure 7 (step S2000). The control unit 10 also moves the substrate holder 24 and the detector 26 so that the center of the imaging area of ​​the object under inspection 2 and the center of the detector 26 are located on axis A (on the optical axis of the radiation generator 22) (step S2002). At this time, the position of the radiation generator 22 in the Z-axis direction does not need to be specifically specified, and the radiation generator 22 is set in step S2002 to a position where the entire imaging area can be clearly imaged. However, the positions of the radiation generator 22, the substrate holder 24 and the detector 26 must be the same as when the reference image was acquired. Then, the control unit 10 irradiates the currently selected imaging area of ​​the object under examination 2 with radiation from the radiation generator 22, and the detector 26 detects the radiation that has passed through this imaging area to acquire a transmitted image (detection image) (step S2004).

[0062] Next, the control unit 10 reads a reference image of the currently selected imaging area from the storage unit 34 (step S2006), calculates the feature quantities of this reference image and the detection image captured in step S2004, and detects the same location (the feature shape to be compared) using the feature quantity matching method (step S2008). Alternatively, the feature shape may be detected using the phase-limited correlation method. For example, a specific pattern or mark set on the substrate of the object under inspection 2, or the outline of a component placed on the substrate, can be used as the feature shape. Locations with a high feature quantity agreement rate are detected from these patterns, marks, or component outlines. Then, the magnification ratio of the feature shape (e.g., pattern, mark, component outline) is calculated for each of the reference image and the detection image (step S2010), the amount of deviation is calculated from the difference in magnification ratios of the reference image and the detection image, and this amount of deviation is stored in the storage unit 34 as a correction value for the aiming height H (step S2012). The feature shape (pattern, mark, part outline) used to calculate the magnification ratio may be a feature shape located at or near the center of the currently selected imaging region, or it may be the feature shape that best matches the feature quantity. Alternatively, the difference in magnification ratios may be calculated for multiple feature shapes, and their average value may be used as the difference in magnification ratios for the currently selected imaging region. Furthermore, using the rotation-invariant phase-only correlation method instead of the phase-only correlation method allows for the detection of the same location and the calculation of its magnification ratio.

[0063] Once the calculation of the displacement amount (correction value for aiming height H) for the currently selected imaging area is complete, the control unit 10 determines whether or not a displacement amount has been detected in all of the imaging areas where the displacement amount is detected (step S2014). If it determines that there are still imaging areas where the displacement amount has not been detected ("N" in step S2014), the control unit 10 selects the next imaging area (step S2016) and returns to step S2002 to repeat the process described above. On the other hand, if it determines that a displacement amount has been detected in all of the imaging areas where the displacement amount is detected ("Y" in step S2014), the control unit 10 calculates the displacement amount for the imaging areas where the displacement amount has not been detected from the values ​​of the surrounding imaging areas where the displacement amount has been detected, stores this displacement amount in the storage unit 34 as the correction value for aiming height H (step S2018), and terminates the calculation process for the aiming height correction value. The displacement amount can be calculated by linear interpolation from the displacement amounts of at least three imaging areas among the surrounding imaging areas.

[0064] The object under inspection 2, held by the substrate holding section 24, is fixed around its periphery by a holding member or the like. Therefore, the height of the area near the portion held by the substrate holding section 24 is known. For this reason, the imaging area near the portion held by the substrate holding section 24 may not be included in the detection of displacement, and the displacement from the reference plane S may be determined from the information of the object under inspection 2 and used as the displacement amount of that imaging area (correction value for aiming height H). This displacement amount of the imaging area may be used as data for linear interpolation when determining the displacement amounts of the surrounding imaging areas.

[0065] According to this first correction method, for each imaging area where the amount of displacement is to be detected, one transmission image (detection image) is captured, and the correction value for the aiming height H (the amount of displacement of the inspection target surface of the object being inspected relative to the reference surface S) can be calculated from the difference in magnification between this detection image and the reference image. This reduces the time required for imaging to calculate the correction value and the time required for the correction value calculation process, thus reducing the overall inspection time. Furthermore, since one transmission image is acquired for each imaging area, the amount of radiation exposure during the calculation of the correction value can be reduced. In addition, for imaging areas where the height is known, the known value is used without detection, and for other imaging areas, the amount of displacement in that imaging area (correction value for aiming height H) can be calculated by linear interpolation from the detected or known amount of displacement. This reduces the imaging process required to calculate the correction value and thus the overall inspection time. Furthermore, since no transmission image is acquired in imaging areas where the correction value is not detected, the amount of radiation exposure can also be reduced. Furthermore, since the aiming height H can be corrected simply by acquiring a transmission image of the object under inspection 2, measuring instruments such as length measuring devices for measuring the height of the object under inspection 2 are unnecessary, thereby reducing the cost of the inspection device 1, and eliminating the need for maintenance such as checking for deterioration due to radiation exposure or replacing parts.

[0066] (Second correction method) The second correction method involves detecting the amount of deviation between the inspection target surface of the object under inspection 2 and the reference surface S, i.e., the correction value for the aiming height H, from a cross-sectional image generated by reconstructing the transmission image. Specifically, similar to the inspection of the object under inspection 2, the object under inspection 2 held by the substrate holder 24 and the detector 26 are moved relative to the radiation generator 22, and transmission images are taken at multiple predetermined positions. The cross-sectional image reconstructed from this transmission image (this image is called the "detection image") is compared with a previously captured reference cross-sectional image (a cross-sectional image corresponding to the inspection target surface, and this image is called the "reference image"), and the image that best matches this reference image is identified from the detection images. The actual position in the Z direction is then detected from the identified detection image (cross-sectional image). The difference between this position in the Z direction and the current aiming height H becomes the correction value for the aiming height H.

[0067] The calculation process for the aiming height correction value in this second correction method will be explained with reference to Figure 8. In this second correction method as well, multiple imaging regions (FOVs) are set for the object under inspection 2, but the imaging region for which the aiming height correction value is to be calculated is selected in advance from among these imaging regions and stored in the storage unit 34. Similarly, a cross-sectional image that serves as the reference for the selected imaging region (a reference image which is a cross-sectional image showing the surface to be inspected) is also acquired in advance and stored in the storage unit 34. Even if the aiming height correction value (the amount of deviation between the surface to be inspected and the reference surface S) is not detected in all imaging regions, for imaging regions where the correction value has not been detected, it can be calculated by linear interpolation using the correction values ​​of the imaging regions surrounding that imaging region.

[0068] When the control unit 10 starts the calculation of the targeting height correction value in step S100, it selects one of the imaging areas of the object under inspection 2 for which to calculate the correction value of the targeting height H, as shown in Figure 8 (step S2100). Then, as explained with reference to Figure 4, the control unit 10 sets the position of the radiation generator 22 in the Z-axis direction based on the targeting height H set for the currently selected imaging area, and further moves the substrate holder 24 and the detector 26 according to a preset trajectory, acquiring a transmission image of the object under inspection 2 at a predetermined position (step S2102). Furthermore, the control unit 10 reconstructs the acquired transmission image to generate a cross-sectional image (the detection image described above) in a predetermined range in the Z-axis direction (step S2104).

[0069] Next, the control unit 10 reads a reference image (cross-sectional image of the surface to be inspected) of the currently selected imaging area from the storage unit 34 (step S2106), compares this reference image with the detection image (cross-sectional image) generated in step S2104, identifies the detection image (cross-sectional image) that best matches the reference image, and stores the position of the identified detection image (cross-sectional image) in the Z-axis direction as the position of the detected surface to be inspected in the current imaging area (step S2108). That is, in this step S2108, the amount of displacement between the reference surface S and the surface to be inspected in the aiming area is detected. Here, as a method for identifying the detection image (cross-sectional image) that best matches the reference image from among the detection images (cross-sectional images), for example, the phase-limited correlation method can be used to quickly determine the matching rate regardless of positional displacement. Then, once the control unit 10 has identified the position in the Z-axis direction of the image that best matches the reference image from among the inspection images, it calculates the difference between that position and the currently set aiming height H, and stores this difference in the storage unit 34 as a correction value for the aiming height H of the currently selected imaging area (step S2110).

[0070] Once the calculation of the correction value for the aiming height H of the currently selected imaging area is complete, the control unit 10 determines whether or not the correction value has been calculated for all imaging areas for which the correction value is calculated (step S2112). If it determines that there are still imaging areas for which the correction value has not been calculated ("N" in step S2112), the control unit 10 selects the next imaging area (step S2114) and returns to step S2102 to repeat the process from there. On the other hand, if it determines that the correction value has been calculated for all imaging areas for which the correction value is calculated ("Y" in step S2112), the control unit 10 calculates the correction value for the imaging area for which the correction value has not been calculated by linear interpolation from the correction values ​​of the surrounding imaging areas for which the correction value has been calculated, stores it in the storage unit 34 (step S2116), and terminates the calculation process for the aiming height correction value. Similar to the first correction method, the correction value can be calculated by linear interpolation from the correction values ​​of at least three imaging areas among the surrounding imaging areas. Furthermore, similar to the first correction method, for imaging regions where the height (position in the Z-axis direction) is known, such as the vicinity of the portion held by the substrate holding portion 24, this information may be used as the correction value for the aiming height H.

[0071] According to this second correction method, since the transmitted image is reconstructed to generate a reconstructed image (cross-sectional image), time is required to move the object under inspection 2 (substrate holding part 24) and the detector 26 relative to the radiation generator 22 to acquire the transmitted image, and time is also required for the processing of reconstructing the reconstructed image (cross-sectional image) from the transmitted image. Therefore, compared to the first correction method, the time required to calculate the correction value for the aiming height H is longer, and as a result, the overall inspection time is longer. However, since the inspection target surface is identified from the cross-sectional image reconstructed from the transmitted image, and the correction value for the aiming height H is calculated from the position in the Z-axis direction of the identified cross-sectional image, it becomes easy to match the inspection target surface and the reference surface S in each imaging area, and a reconstructed image (cross-sectional image) without motion blur can be obtained, thereby improving the accuracy of the inspection.

[0072] Furthermore, in this second correction method, the number of transmission images acquired in each imaging area during the process of calculating the correction value for the aiming height can be less than the number of transmission images acquired to inspect the object under inspection 2 (to generate the reconstructed image (cross-sectional image) for inspection). Reducing the number of transmission images will decrease the accuracy of the cross-sectional image generated by reconstruction, but this is not a problem because the range of the irradiation area (the range in the Z-axis direction where blurring does not occur) is wider than the accuracy required for inspection (the step size of the cross-sectional image). Also, similar to the first correction method, the aiming height H can be corrected using only the equipment that acquires the transmission image of the object under inspection 2, so measuring instruments for measuring the height of the object under inspection 2 are unnecessary, which reduces the cost of this inspection device 1 and eliminates the need for checking for deterioration due to radiation exposure or replacing parts. In addition, it becomes unnecessary to place measuring patterns or marks near the part under inspection.

[0073] Furthermore, in order to correct the aiming height H, both the first and second correction methods described above may be implemented in the inspection device 1, and the device may be configured to allow the user of the inspection device 1 to select which method to use to correct the aiming height H. In this case, the first correction method may be set as the default correction method, and the device may be configured to allow the user to select the second correction method only when they wish to use it. [Explanation of symbols]

[0074] 1. Inspection device 2. Subject under inspection 10 Control Unit 16. Radiation generator drive unit (drive unit) 18. Substrate holding unit drive unit (drive unit) 20 Detector drive unit (drive unit) 22. Radiation generator (radiation source) 24 Board holding part (holding part) 26 Detectors

Claims

1. The radiation source and, A holding part for holding the object to be inspected, Detector and A drive unit that changes the relative position between the radiation source, the object to be inspected held by the holding unit, and the detector, It has a control unit and The control unit, When the radiation source, the object to be inspected held by the holding unit, and the detector are in a predetermined relative position by the drive unit, the same feature shape is detected by phase-limited correlation in a single transmission image of the object to be inspected obtained by detecting the radiation emitted from the radiation source and transmitted through the object to be inspected with the detector, and in a reference image which is a transmission image when the inspection target surface of the object to be inspected is on a predetermined reference plane at the predetermined relative position, and the amount of deviation of the inspection target surface of the object to be inspected from the predetermined reference plane is detected based on the difference in the magnification of the feature shape. Inspection device.

2. The radiation source and, A holding part for holding the object to be inspected, Detector and A drive unit that changes the relative position between the radiation source, the object to be inspected held by the holding unit, and the detector, It has a control unit and The control unit, When the radiation source, the object to be inspected held by the holding unit, and the detector are in a predetermined relative position by the drive unit, the detector detects the radiation emitted from the radiation source and transmitted through the object to be inspected to obtain a single transmitted image of the object to be inspected, and the detector detects identical feature shapes in a reference image, which is a transmitted image of the object to be inspected when the inspection surface of the object to be inspected is on a predetermined reference plane at the predetermined relative position, and the amount of deviation of the inspection surface of the object to be inspected from the predetermined reference plane is detected based on the difference in the magnification of the feature shapes. Inspection device.

3. The radiation source and, A holding part for holding the object to be inspected, Detector and A drive unit that changes the relative position between the radiation source, the object to be inspected held by the holding unit, and the detector, It has a control unit and The control unit, When the radiation source, the object to be inspected held by the holding unit, and the detector are in predetermined relative positions as a drive unit, the radiation emitted from the radiation source and transmitted through the object to be inspected is detected by the detector to obtain two or more transmission images of the object to be inspected, where the radiation source, the object to be inspected held by the holding unit, and the detector are in different positions. A cross-sectional image of the object to be inspected is generated by reconstructing the two or more transmission images, and the amount of deviation of the inspection target surface of the object to be inspected from a predetermined reference plane is detected using the cross-sectional image. Inspection device.

4. The control unit, From the aforementioned cross-sectional images, the cross-sectional image that best matches the reference image of the cross-sectional images is identified, and the amount of displacement is detected from the position of that cross-sectional image. The inspection apparatus according to claim 3.

5. The control unit, From the aforementioned cross-sectional images, the cross-sectional image that best matches the reference image of the cross-sectional images is identified using the phase-limited correlation method, and the amount of displacement is detected from the position of that cross-sectional image. The inspection apparatus according to claim 4.

6. The control unit, The amount of displacement is detected at multiple locations on the object to be inspected, The displacement amounts for positions where the aforementioned displacement amount has not been detected are calculated by linear interpolation using the detected displacement amounts. The inspection apparatus according to any one of claims 1 to 5.

7. The control unit, In calculating the displacement amount for positions where the displacement amount has not been detected, linear interpolation is performed using the values ​​for positions where the displacement amount is known, in addition to the detected displacement amount. The inspection apparatus according to claim 6.

8. The control unit, For each position on the object under inspection where the transmitted image is acquired, a correction value is calculated from the amount of displacement relative to the position of the predetermined reference plane, and the relative positions of the radiation source, the object under inspection held by the holding unit, and the detector are corrected based on the correction value. Based on the corrected relative position, the drive unit changes the relative position between the radiation source, the object under inspection held by the holding unit, and the detector, and acquires the transmission image at a predetermined relative position. The inspection apparatus according to any one of claims 1 to 7.

Images