Method for inspecting radiation and apparatus for inspecting radiation

Abstract

This X-ray inspection method includes: a first control step for controlling an incident position of an electron beam EB from a first incident position Y1 to a second incident position Y2 on a target 22 for generating X-rays when the electron beam EB is incident; a second irradiation step for emitting the electron beam EB toward the second incidence position Y2 in the target 22 and irradiating a structure provided on a mounting substrate SB with X-rays; and a second image acquisition step for acquiring a second image which is an X-ray image of the structure provided on the mounting substrate SB.

Description

Radiation Inspection Method and Radiation Inspection Apparatus 【0001】 The present disclosure relates to a radiation inspection method and a radiation inspection apparatus. 【0002】 Patent Document 1 describes a bump inspection apparatus for detecting defects in the connection portion between a pad and a bump. This bump inspection apparatus includes a main X-ray source that irradiates main X-rays from a perpendicular direction to bumps formed on pads of a printed circuit board, a main X-ray sensor that detects and images the main X-rays transmitted through the bumps, a sub X-ray source that irradiates sub X-rays to the bumps from an oblique direction, and a sub X-ray sensor that detects and images the sub X-rays transmitted through the bumps. 【0003】 Japanese Patent Laid-Open No. 6-53290 【0004】 In an inspection apparatus as described in Patent Document 1, different X-ray sources are arranged for each imaging direction. In this case, since it is difficult to freely change the generation position of the X-rays, it becomes difficult to image structures such as bumps formed on the mounting substrate from an appropriate direction. Therefore, in such an inspection apparatus, there is room for improvement in facilitating the inspection. 【0005】 Therefore, an object of the present disclosure is to provide a radiation inspection method and a radiation inspection apparatus that can easily inspect structures provided on a mounting substrate. 【0006】 The gist of the radiation inspection method and the radiation inspection apparatus according to one aspect of the present disclosure is as follows in [1] to [9]. 【0007】 [1] A radiation generation member that generates radiation when a beam is incident, a first control step of controlling the incident position of the beam from a first incident position to a second incident position, a second irradiation step of emitting the beam toward the second incident position in the radiation generation member and irradiating the radiation to a structure provided on a mounting substrate, and a second image acquisition step of detecting the radiation transmitted through the structure in a second state where the incident position of the beam is the second incident position and acquiring a second image that is a radiation image of the structure based on the detection result of the radiation. A radiation inspection method comprising: 【0008】In the radiation inspection method described in [1] above, by controlling the beam incidence position from the first incidence position to the second incidence position, structures provided on the mounting substrate can be imaged from an appropriate direction. Furthermore, compared to the case where multiple radiation sources are arranged to change the radiation generation position, the radiation generation position can be freely controlled. Therefore, according to the radiation inspection method described in [1] above, structures provided on the mounting substrate can be easily inspected. 【0009】 [2] The radiation inspection method according to [1], further comprising: a first irradiation step of emitting the beam toward the first incidence position and irradiating the structure provided on the mounting substrate with the radiation; and a first image acquisition step of detecting the radiation that has passed through the structure in a first state where the incidence position of the beam is the first incidence position, and acquiring a first image which is a radiation image of the structure based on the radiation detection result, wherein in the first control step, the incidence position of the beam is controlled from the first incidence position to the second incidence position based on the first image. In this case, the incidence position of the beam can be effectively controlled from the first incidence position to the second incidence position using the first image. 【0010】 [3] The radiation inspection method according to [2], further comprising: a displacement amount acquisition step of acquiring the amount of angular displacement of the structure based on the first image; and a first movement amount acquisition step of acquiring a first movement amount of the incident position of the beam based on the amount of angular displacement, wherein the first control step controls the incident position of the beam from the first incident position to the second incident position based on the first movement amount. In this case, the incident position of the beam can be effectively controlled from the first incident position to the second incident position using the amount of angular displacement. 【0011】 [4] The radiation inspection method according to [1], further comprising a design information acquisition step of acquiring design information of the structure, wherein the first control step controls the incident position of the beam from a first incident position to a second incident position based on the design information. In this case, the incident position of the beam can be effectively controlled from a first incident position to a second incident position using the design information. 【0012】[5] The radiation inspection method according to any one of [1] to [4], wherein in the first control step, the incident position of the beam is controlled from the first incident position to the second incident position so that the central axis of the radiation coincides with the central axis of the structure. In this case, the size of the structure can be accurately obtained using the second image. 【0013】 [6] A radiation inspection method according to any one of [1] to [5], wherein the mounting substrate has a plurality of structures including the structure formed on it, and further comprises a design information acquisition step of acquiring design information of the plurality of structures, and a second displacement acquisition step of acquiring a second displacement of the incident position of the beam based on the design information so that the central axis of the radiation coincides with the central axis of another structure among the plurality of structures that is different from the structure. In this case, the second displacement can be easily acquired by using the design information. For example, the size of the other structure can be accurately acquired by using an X-ray image of the other structure acquired by controlling the incident position of the beam based on the second displacement. 【0014】 [7] A radiation inspection method according to any one of [1] to [6], further comprising: controlling the incident position of the beam from the second incident position to the third incident position; emitting the beam toward the third incident position in the radiation generating member and irradiating the structure with the radiation; detecting the radiation that has passed through the structure while the incident position of the beam is at the third incident position, and acquiring a third image which is a radiation image of the structure based on the radiation detection result; and acquiring a tomographic image based on the second image and the third image to acquire a tomographic image of the structure. In this case, the size of the structure at any height can be obtained. 【0015】 [8] The structure is a microbump, a through-hole, or a via, the radiographic inspection method according to any one of [1] to [7]. In this case, the microbump, through-hole, or via can be easily inspected. 【0016】[9] A radiation source for irradiating a structure provided on a mounting substrate with radiation, comprising: a beam emission unit for emitting a beam; a radiation generating member for generating radiation when the beam is incident on it; a control unit for controlling the incident position of the beam in the radiation generating member between a first incident position and a second incident position; and a radiation detection unit having a plurality of pixels for detecting the radiation that has passed through the structure, and acquiring a radiation image of the structure based on the radiation detection results by the plurality of pixels, wherein the control unit controls the incident position of the beam from the first incident position to the second incident position, and the radiation detection unit acquires a second image as the radiation image when the incident position of the beam is the second incident position. 【0017】 In the radiation inspection apparatus described in [9] above, by controlling the beam incidence position from the first incidence position to the second incidence position, structures provided on the mounting substrate can be imaged from an appropriate direction. Furthermore, compared to the case where multiple radiation sources are arranged to change the radiation generation position, the radiation generation position can be freely controlled. Therefore, according to the radiation inspection apparatus described in [9] above, structures provided on the mounting substrate can be easily inspected. 【0018】 According to this disclosure, structures provided on a mounting substrate can be easily inspected. 【0019】This is a schematic diagram showing the configuration of an X-ray inspection apparatus according to an embodiment. (a) to (c) are schematic diagrams showing the configuration of an X-ray source. (a) to (c) are schematic diagrams showing the configuration of an X-ray source. This is a flowchart for explaining a first example of an X-ray inspection method. (a) is a schematic diagram showing the irradiation of an X-ray to a mounting substrate in a first state, and (b) is a diagram showing an X-ray image of a through-hole acquired in the first state. (a) is a schematic diagram showing the irradiation of an X-ray to a mounting substrate in a second state, and (b) is a diagram showing an X-ray image of a through-hole acquired in the second state. This is a flowchart for explaining a second example of an X-ray inspection method. (a) to (c) are schematic diagrams showing the irradiation of an X-ray with the focus of the X-ray aligned to each of the three through-holes. This is a flowchart for explaining a third example of an X-ray inspection method. (a) and (b) are schematic diagrams showing the irradiation of an X-ray to a microbump. (a) is a schematic diagram showing the image of an object when it is imaged, and (b) is a schematic diagram showing the image of an object when it is imaged at a higher magnification than in (a) of Figure 11. 【0020】 Hereinafter, with reference to the drawings, preferred embodiments of an X-ray inspection apparatus and an X-ray inspection method relating to one aspect of this disclosure will be described in detail. [Configuration of the X-ray inspection apparatus according to the embodiment] 【0021】 Figure 1 is a schematic diagram showing the configuration of an X-ray inspection apparatus according to an embodiment. Figures 2(a) to (c) and 3(a) to (c) are schematic diagrams showing the configuration of an X-ray source. The X-ray inspection apparatus 1 (radiation inspection apparatus) shown in Figure 1 is an apparatus that acquires an X-ray image (radiation image) of a mounting substrate SB placed on a stage (not shown) and inspects structures provided on the mounting substrate SB using the X-ray image. The mounting substrate SB is, for example, a printed circuit board or a semiconductor substrate. The mounting substrate SB may be a single-sided substrate, a double-sided substrate, a multilayer substrate, or a bonded substrate, etc. 【0022】Structures provided on the mounting substrate SB include, for example, microbumps, bumps, BGA (Ball Grid Array), through-holes, microvias, interposer vias, TSV (Through-Silicon Via), Cu-Cu hybrid bonding, Cu-Cu direct coupling, through-hole components, surface-mount components, or chip components. 【0023】 The X-ray inspection apparatus 1 comprises an X-ray source 2 (radiation source), a control unit 3, an X-ray detection unit 4 (radiation detection unit), a processing unit 5, an X-ray source fixing jig 6, and a detection unit fixing jig 7. The X-ray inspection apparatus 1 is used, for example, in X-ray non-destructive testing to magnify and observe a mounted substrate SB. In this case, the positional relationship (magnification) between the X-ray source 2, the mounted substrate SB (stage), and the X-ray detection unit 4 can be adjusted in the X-ray inspection apparatus 1 according to the purpose of observing the mounted substrate SB. 【0024】 The mounting substrate SB is positioned between the X-ray source 2 and the X-ray detection unit 4 in direction D1. In the following description, the direction perpendicular to direction D1 will be referred to as direction D2, and the direction perpendicular to both directions D1 and D2 will be referred to as direction D3. Directions D2 and D3 are also directions that intersect the optical axis (central axis) of the X-rays. The X-ray source 2 is fixed to the X-ray source fixing jig 6, and the X-ray detection unit 4 is fixed to the detection unit fixing jig 7. This fixes the positions of the X-ray source 2 and the X-ray detection unit 4, respectively. 【0025】 The X-ray source 2 emits X-rays along direction D1 and irradiates the mounting substrate SB with these X-rays. The X-ray source 2 is a so-called transmission-type X-ray source. The X-ray source 2 includes an electron gun 21 (beam emission unit), a target 22 (radiation generating member), a first deflection unit 23A, a second deflection unit 23B, a third deflection unit 23C, and a fourth deflection unit 23D. Note that in Figure 1, the target 22 and the deflection units 23A to 23D are not shown. The X-ray source 2 has, for example, a housing (not shown) that houses the electron gun 21 and the target 22, and the space inside the housing is a space where vacuum has been applied. The X-ray source 2 is communicated with the control unit 3, the X-ray detection unit 4, and the processing unit 5, respectively. 【0026】The electron gun 21 emits an electron beam EB toward the target 22 along direction D1. The electron gun 21 consists of a thermal cathode that emits thermionic electrons, and an electron lens that adjusts the focusing of the electron beam EB. The target 22 is a transmission-type target that generates X-rays when the electron beam EB is incident on it. Examples of materials that make up the target 22 include tungsten, molybdenum, cobalt, copper, silver, iron, or rhodium. The target 22 is formed in the shape of a plate extending along a plane perpendicular to direction D1. That is, the target 22 extends at least along direction D2. The target 22 may be formed on another support by methods such as deposition or sputtering, or it may be embedded in the support. For example, the support can be made of a material with high X-ray transparency such as beryllium, aluminum, diamond, carbon, silicon, or glass. 【0027】 Each of the first deflection section 23A, the second deflection section 23B, the third deflection section 23C, and the fourth deflection section 23D is composed of, for example, a deflection electrode. A positive or negative potential is applied to each of the deflection sections 23A to 23D by the control unit 3, which will be described later. In Figures 2(a) to (c), the deflection sections 23A and 23B are shown, while the deflection sections 23C and 23D are omitted. In Figures 3(a) to (c), the deflection sections 23C and 23D are shown, while the deflection sections 23A and 23B are omitted. 【0028】 The first deflection unit 23A and the second deflection unit 23B are arranged so as to straddle the trajectory of the electron beam EB in direction D2. Figure 2(a) shows the state in which the electron beam EB is not deflected (the state in which no potential is applied to the first deflection unit 23A and the second deflection unit 23B). Figure 2(b) shows the state in which the electron beam EB is deflected towards the second deflection unit 23B due to the electric field formed between the first deflection unit 23A and the second deflection unit 23B. Figure 2(c) shows the state in which the electron beam EB is deflected towards the first deflection unit 23A due to the electric field formed between the first deflection unit 23A and the second deflection unit 23B. 【0029】The third deflection section 23C and the fourth deflection section 23D are positioned to straddle the trajectory of the electron beam EB in direction D3. Figure 3(a) shows the state in which the electron beam EB is not deflected (the state in which no potential is applied to the third deflection section 23C and the fourth deflection section 23D). Figure 3(b) shows the state in which the electron beam EB is deflected towards the fourth deflection section 23D due to the electric field formed between the third deflection section 23C and the fourth deflection section 23D. Figure 3(c) shows the state in which the electron beam EB is deflected towards the third deflection section 23C due to the electric field formed between the third deflection section 23C and the fourth deflection section 23D. 【0030】 Each deflection section 23A to 23D only needs to be able to deflect the electron beam EB, and may be composed of deflection coils. Furthermore, the number and arrangement positions of the deflection sections are not particularly limited and may be determined as appropriate. 【0031】 The control unit 3 is communicatively connected to the X-ray source 2 and the processing unit 5, and is composed of a computer including, for example, a processor (CPU), and recording media such as RAM and ROM. The control unit 3 also includes, for example, a potential application unit for applying potential to the deflection units 23A to 23D. The control unit 3 controls the potential applied to the deflection units 23A to 23D, thereby deflecting the electron beam EB using the deflection units 23A to 23D. When the electron beam EB is deflected, the incident position of the electron beam EB on the target 22 changes. In other words, in the X-ray inspection apparatus 1, the control unit 3 controls the incident position of the electron beam EB by deflecting the electron beam EB using the deflection units 23A to 23D. 【0032】As an example, as shown in Figure 2(b), the control unit 3 controls the incident position of the electron beam EB to the first incident position Y1 (an incident position located on the second deflection unit 23B side relative to the incident position Y0 when the electron beam EB is not deflected). Also, as shown in Figure 2(c), the control unit 3 controls the incident position of the electron beam EB to the second incident position Y2 (an incident position located on the first deflection unit 23A side relative to the incident position Y0). As shown in Figure 3(b), the control unit 3 controls the incident position of the electron beam EB to the third incident position Y3 (an incident position located on the fourth deflection unit 23D side relative to the incident position Y0). As shown in Figure 3(c), the control unit 3 controls the incident position of the electron beam EB to the fourth incident position Y4 (an incident position located on the third deflection unit 23C side relative to the incident position Y0). 【0033】 As a result, the control unit 3 controls the incident position of the electron beam EB between incident positions Y1 to Y4. The incident position of the electron beam EB is the focal position of the electron beam EB in the target 22, or in other words, the X-ray generation position (X-ray focal position) in the target 22. In other words, it can be said that the control unit 3 controls the X-ray focal position. 【0034】 As described above, the X-ray inspection apparatus 1 can irradiate the mounting substrate SB with X-rays generated when the electron beam EB is incident at each of the incident positions Y1 to Y4. The X-rays that have passed through the mounting substrate SB are incident on the X-ray detection unit 4. In the following description, the state in which the incident position of the electron beam EB is the first incident position Y1 is referred to as the "first state", the state in which the incident position of the electron beam EB is the second incident position Y2 is referred to as the "second state", the state in which the incident position of the electron beam EB is the third incident position Y3 is referred to as the "third state", and the state in which the incident position of the electron beam EB is the fourth incident position Y4 is referred to as the "fourth state". The control unit 3 can also be said to be switching the detection state between the first to fourth states. 【0035】In Figures 2(a) to 2(c) and 3(a) to 2(c), the incident position of the electron beam EB moved along direction D2 or direction D3. However, the control unit 3 may move the incident position of the electron beam EB along a direction inclined with respect to both direction D2 and direction D3 (for example, a direction inclined by 45 degrees with respect to each of direction D2 and direction D3) by controlling the potential applied to the deflection units 23A to 23D. The positions of incident positions Y1 to Y4 in the first to fourth states are not limited to the positions shown in Figures 2(a) to 2(c) and 3(a) to 2(c). As shown in Figures 8(a) to 2(c) described later, the incident positions Y2 to Y4 may be aligned in direction D2. 【0036】 The X-ray detection unit 4 detects X-rays that have passed through a structure provided on the mounting substrate SB and acquires an X-ray image of the structure based on the detection result. The X-ray detection unit 4 is communicated with the X-ray source 2 and the processing unit 5, respectively. The X-ray detection unit 4 has a plurality of pixels 41 (see Figure 5(a), etc., described later) for detecting X-rays that have passed through the mounting substrate SB. The plurality of pixels 41 are arranged at least along direction D2. The X-ray detection unit 4 is, for example, an area sensor in which the plurality of pixels 41 are arranged in two dimensions. The X-ray detection unit 4 may also be a line sensor in which the plurality of pixels 41 are arranged in one dimension. In the following description, the X-ray image acquired by the X-ray detection unit 4 in the first state will be referred to as the "first image", the X-ray image acquired by the X-ray detection unit 4 in the second state will be referred to as the "second image", the X-ray image acquired by the X-ray detection unit 4 in the third state will be referred to as the "third image", and the X-ray image acquired by the X-ray detection unit 4 in the fourth state will be referred to as the "fourth image". 【0037】The processing unit 5 is communicatively connected to the X-ray source 2, the control unit 3, and the X-ray detection unit 4, and is composed of a computer including, for example, a processor (CPU), and recording media such as RAM and ROM. The processing unit 5 processes the X-ray image output from the X-ray detection unit 4. The processing unit 5 may acquire height information of structures provided on the mounting substrate SB. The processing unit 5 may acquire a composite image of two or more X-ray images. The processing unit 5 may acquire a tomographic image or a three-dimensional image of the structure based on two or more X-ray images. Note that the X-ray detection unit 4 may have a processing unit 5. In other words, the X-ray detection unit 4 may function as the processing unit 5. [First example of X-ray inspection method] 【0038】 Referring to Figures 4 to 6, a first example of an X-ray inspection method (radiation inspection method) using the X-ray inspection apparatus 1 will be described. In the first example, a through-hole TH is provided in the mounting substrate SB. Figure 4 is a flowchart for explaining the first example of the X-ray inspection method. Figure 5(a) is a schematic diagram showing the irradiation of X-rays to the mounting substrate SB in the first state, and Figure 5(b) is a diagram showing the X-ray image (first image) of the through-hole TH acquired in the first state. Figure 6(a) is a schematic diagram showing the irradiation of X-rays to the mounting substrate SB in the second state, and Figure 6(b) is a diagram showing the X-ray image (second image) of the through-hole TH acquired in the second state. When performing dimensional inspection of the through-hole TH, it is desirable to inspect the geometric positional relationship between the X-ray generation position and the position of the through-hole TH in order to reduce the effect of oblique X-ray entry. 【0039】 In step S11, the stage on which the mounted substrate SB is placed is moved to roughly align the X-ray focal point with the mounted substrate SB. 【0040】 In step S12, the electron gun 21 emits an electron beam EB toward the first incident position Y1 in the target 22. As a result, X-rays are irradiated into the through-hole TH, as shown in Figure 5(a) (first irradiation step). In the example in Figure 5(a), the position of the first incident position Y1 is offset from the position directly above the through-hole TH, and the optical axis LA (central axis) of the X-ray does not coincide with the central axis CA of the through-hole TH. 【0041】 In step S13, the X-ray detector 4 detects the X-rays transmitted through the through-hole TH in the first state, and acquires a first image which is an X-ray image of the through-hole TH based on the X-ray detection result (first image acquisition step). 【0042】 In step S14, the processing unit 5 acquires the amount of deviation of the angle of the through-hole TH based on the first image (deviation amount acquisition step). In the first state, since the optical axis LA of the X-rays does not coincide with the central axis CA of the through-hole TH, as shown in (b) of FIG. 5, the through-hole TH is inclined in the first image. As an example, the amount of angular deviation is the angle formed by a straight line passing through the first incident position Y1 and perpendicular to the X-ray detector 4 and a straight line passing through the first incident position Y1 and the through-hole TH to be inspected. In the example of (a) of FIG. 5, the angle corresponds to the angle α formed by the optical axis LA of the X-rays and a straight line KA passing through the first incident position Y1 and the through-hole TH to be inspected. 【0043】 In step S15, the processing unit 5 acquires the movement amount (first movement amount) of the incident position of the electron beam EB based on the amount of angular deviation (first movement amount acquisition step). The processing unit 5 acquires the movement amount of the incident position of the electron beam EB required to make the optical axis LA of the X-rays coincide with the central axis CA of the through-hole TH in step S17 described later. 【0044】 In step S16, the control unit 3 controls the incident position of the electron beam EB from the first incident position Y1 to the second incident position Y2 based on the movement amount acquired in step S15 (first control step). The movement amount corresponds to the distance between the first incident position Y1 and the second incident position Y2. Thus, the control unit 3 controls the incident position of the electron beam EB from the first incident position Y1 to the second incident position Y2 so that the optical axis LA of the X-rays coincides with the central axis CA of the through-hole TH. In the example of (a) of FIG. 6, the second incident position Y2 is located directly above the through-hole TH. 【0045】In step S17, the electron gun 21 emits an electron beam EB toward the second incident position Y2 on the target 22. As shown in (a) of FIG. 6, with the optical axis LA of the X-ray coinciding with the central axis CA of the through hole TH, the through hole TH is irradiated with X-rays (second irradiation step). 【0046】 In step S18, the X-ray detection unit 4 detects the X-rays that have passed through the through hole TH in the second state, and acquires a second image, which is an X-ray image of the through hole TH, based on the X-ray detection result (second image acquisition step). 【0047】 In step S19, the processing unit 5 acquires the hole diameter of the through hole TH based on the second image. In the second state, since the optical axis LA of the X-ray coincides with the central axis CA of the through hole TH, as shown in (b) of FIG. 6, the through hole TH is not tilted in the second image. Therefore, by using the second image, the hole diameter of the through hole TH can be accurately acquired. [Operation and Effect] 【0048】 As described above, in the first example of the X-ray inspection apparatus 1 and the X-ray inspection method, by controlling the incident position of the electron beam EB from the first incident position Y1 to the second incident position Y2 based on the first image, the through hole TH provided in the mounting substrate SB can be imaged from an appropriate direction. Further, compared with the case of arranging a plurality of X-ray sources and changing the X-ray generation position, the X-ray generation position can be freely controlled. Therefore, the through hole TH provided in the mounting substrate SB can be easily inspected. 【0049】 In the first example of the X-ray inspection method, the incident position of the electron beam EB is controlled from the first incident position Y1 to the second incident position Y2 so that the optical axis LA of the X-ray coincides with the central axis CA of the through hole TH. In this case, the size of the through hole TH can be accurately acquired using the second image. 【0050】In the first example of the X-ray inspection method, the angular displacement of the through-hole TH is obtained based on the first image, and the amount of movement of the incident position of the electron beam EB is obtained based on the angular displacement. Furthermore, based on this amount of movement, the incident position of the electron beam EB is controlled from the first incident position Y1 to the second incident position Y2. In this case, the optical axis LA of the X-ray can be reliably aligned with the central axis CA of the through-hole TH. [Second example of the X-ray inspection method] 【0051】 A second example of an X-ray inspection method using the X-ray inspection apparatus 1 will be described with reference to Figures 7 and 8(a) to 8(c). In this second example, three through-holes TH1 to TH3 are provided on the mounting substrate SB. The number of through-holes provided on the mounting substrate SB is not limited. Figure 7 is a flowchart for explaining the second example of the X-ray inspection method. Figures 8(a) to 8(c) are schematic diagrams showing X-ray irradiation with the focus of the X-rays aligned to each of the three through-holes TH1 to TH3. 【0052】 In step S21, the processing unit 5 acquires design information for through-holes TH1 to TH3 (design information acquisition step). As an example, the processing unit 5 accepts design information as input. The design information is, for example, CAD (Computer Aided Design) data of the mounted substrate SB, including the position information of through-holes TH1 to TH3. 【0053】 In step S22, the through-hole TH1 is inspected by performing steps S11 to S19 shown in Figure 4. Specifically, the incidence position of the electron beam EB is controlled based on the first image, so that, as shown in Figure 8(a), the incidence position of the electron beam EB is controlled to a second incidence position Y2 directly above the through-hole TH1. As a result, the optical axis LA of the X-ray coincides with the central axis of the through-hole TH1. In this state, the through-hole TH1 is irradiated with X-rays, and a second image, which is an X-ray image of the through-hole TH1, is acquired. Then, based on the second image, the hole diameter of the through-hole TH1 is acquired. 【0054】In step S23, the processing unit 5 determines whether the inspection of all through-holes (in the second example, the three through-holes TH1 to TH3) has been completed. In other words, the processing unit 5 determines whether the hole diameter of all through-holes has been obtained. If the determination result by the processing unit 5 indicates that the inspection of all through-holes has been completed (step S23: YES), the process ends. If the determination result by the processing unit 5 indicates that the inspection of all through-holes has not been completed (step S23: NO), the process proceeds to step S24, and steps S24 to S28 are repeated until the inspection of all through-holes is completed. 【0055】 In step S24, the processing unit 5 acquires the amount of movement of the incident position of the electron beam EB (second movement amount) based on the design information acquired in step S21 (second movement amount acquisition step). The processing unit 5 acquires the amount of movement of the incident position of the electron beam EB required to align the X-ray optical axis LA with the central axis of the through-hole TH2 in step S26, which will be described later. Since the design information includes the position information of the through-hole TH2, the amount of movement required to align the focus of the X-ray with the through-hole TH2 can be acquired by using the design information. 【0056】 In step S25, the control unit 3 controls the incident position of the electron beam EB from the second incident position Y2 to the third incident position Y3 based on the amount of movement acquired in step S24. This amount of movement corresponds to the distance between the second incident position Y2 and the third incident position Y3. In this way, the control unit 3 controls the incident position of the electron beam EB from the second incident position Y2 to the third incident position Y3 so that the optical axis LA of the X-ray coincides with the central axis of the through-hole TH2. 【0057】 In step S26, the electron gun 21 emits an electron beam EB toward the third incidence position Y3 in the target 22. At this time, as shown in Figure 8(b), the X-ray beam is irradiated into the through-hole TH2 with the X-ray beam axis LA aligned with the central axis of the through-hole TH2. 【0058】In step S27, the X-ray detection unit 4 acquires a third image, which is an X-ray image of the through-hole TH2. In step S28, the processing unit 5 acquires the hole diameter of the through-hole TH2 based on the third image. With this, the inspection of the through-hole TH2 is completed. 【0059】 After the inspection of through-hole TH2 is completed, the determination process in step S23 is performed. Then, steps S24 to S28 are performed on through-hole TH3. Specifically, the incidence position of the electron beam EB is controlled based on the design information, so that, as shown in Figure 8(c), the incidence position of the electron beam EB is controlled to the fourth incidence position Y4 directly above through-hole TH3. As a result, the optical axis LA of the X-ray coincides with the central axis of through-hole TH3. In this state, the through-hole TH3 is irradiated with X-rays, and a fourth image, which is an X-ray image of through-hole TH3, is acquired. Then, based on the fourth image, the hole diameter of through-hole TH3 is acquired. 【0060】 As explained above, in the second example of the X-ray inspection method, the amount of movement of the electron beam EB incident position is obtained based on design information so that the X-ray optical axis LA coincides with the central axis of through-holes TH2 and TH3 (separate structures) which are different from through-hole TH1. In this case, the amount of movement can be easily obtained by using the design information. Furthermore, by using the X-ray images of through-holes TH2 and TH3 obtained by controlling the incident position of the electron beam EB based on the amount of movement, the sizes of through-holes TH2 and TH3 can be accurately obtained. 【0061】In the second example of the X-ray inspection method described above, the through-hole TH1 is inspected in step S22 by executing steps S11 to S19 shown in Figure 4. However, if design information for through-holes TH1 to TH3 is acquired in step S21, steps S12 to S14 shown in Figure 4 may be omitted. In this case, instead of steps S12 to S14, the control unit 3 may acquire the amount of movement of the incident position of the electron beam EB (first movement amount) based on the design information. This movement amount corresponds to the distance between the first incident position Y1 and the second incident position Y2. Based on this movement amount, the control unit 3 may control the incident position of the electron beam EB from the first incident position Y1 to the second incident position Y2. In other words, without emitting the electron beam to the first incident position Y1 (without acquiring the first image), the incident position of the electron beam EB may be controlled from the first incident position Y1 to the second incident position Y2 using the design information to align the optical axis of the X-ray with the central axis of the through-hole TH1. In this case, the first incidence position Y1 refers to the position where the electron beam EB would be incident if the electron beam EB were emitted from the electron gun 21 without control by the control unit 3, and it is not necessary for the electron beam EB to actually be emitted toward the first incidence position Y1. The first incidence position Y1 may also be the default incidence position of the electron beam EB set in the X-ray source 2. [Third example of X-ray inspection method] 【0062】 A third example of an X-ray inspection method using the X-ray inspection apparatus 1 will be described with reference to Figure 9 and Figures 10(a) and (b). In this third example, microbumps MB are provided on the mounting substrate SB. The microbump MB has a bump portion MBa and copper portions MBb arranged above and below the bump portion MBa. The number of microbumps provided on the mounting substrate SB is not limited. Figure 9 is a flowchart for explaining the third example of the X-ray inspection method. Figures 10(a) and (b) are schematic diagrams showing the irradiation of X-rays onto the microbump MB. In Figures 10(a) and (b), the mounting substrate SB is not shown. 【0063】In step S31, the same process as in steps S11 to S18 shown in Figure 4 is performed to image the microbump MB. Specifically, the incident position of the electron beam EB is controlled based on the first image, so that, as shown in Figure 10(a), the incident position of the electron beam EB is controlled to a second incident position Y2 directly above the microbump MB. As a result, the optical axis LA of the X-ray beam coincides with the central axis of the microbump MB. In this state, the microbump MB is irradiated with X-rays, and a second image, which is an X-ray image of the microbump MB, is acquired. 【0064】 In step S32, the control unit 3 controls the incident position of the electron beam EB from the second incident position Y2 to the third incident position Y3 (second control step). As a result, the control unit 3 controls the incident position of the electron beam EB to a position offset from directly above the microbump MB, as shown in Figure 10(b). 【0065】 In step S33, the electron gun 21 emits an electron beam EB toward the third incidence position Y3 on the target 22. As a result, the microbump MB is irradiated with X-rays, as shown in Figure 10(b) (third irradiation step). In step S34, the X-ray detection unit 4 acquires a third image, which is an X-ray image of the microbump MB (third image acquisition step). 【0066】 In step S35, the processing unit 5 determines whether or not the acquisition of X-ray images has been completed. For example, the processing unit 5 determines whether or not the acquisition of the number of X-ray images specified by the user has been completed. If the determination result by the processing unit 5 indicates that the acquisition of X-ray images has been completed (step S35: YES), the process proceeds to step S36. If the determination result by the processing unit 5 indicates that the acquisition of X-ray images has not been completed (step S35: NO), the process proceeds to step S32, and the processing from steps S32 to S34 is repeated until an X-ray image meeting the conditions specified by the user (direction, angle, or amount of movement, etc.) is acquired. The following describes the process when the user specifies the acquisition of a second and a third image. In this process, the acquisition of X-ray images is completed when the third image is acquired in step S34. Therefore, the process proceeds to step S36. 【0067】In step S36, the processing unit 5 acquires a tomographic image of the microbump MB based on the second and third images (tomographic image acquisition step). The processing unit 5 acquires a tomographic image by integrating the second and third images while changing the shift amount according to the height of the tomographic plane of interest. The tomographic image may also be acquired by reconstructing multiple acquired X-ray images, as in X-ray CT. 【0068】 In step S37, the processing unit 5 obtains the size of the microbump MB based on the tomographic image acquired in step S36. The processing unit 5 can obtain the size of the microbump MB at any height using the tomographic image. The processing unit 5 may also obtain the diameter of the bump portion MBa, the diameter of the copper portion MBb, the height of the bump portion MBa, or the filling rate of the bump portion MBa. The processing unit 5 may also determine whether there are voids in the bump portion MBa and obtain the location of any voids. If multiple microbump MBs are provided on the mounting substrate SB, the processing unit 5 may also determine whether the bump portions MBa of adjacent microbump MBs are in contact with each other and obtain the location of any contact. The processing unit 5 may also determine whether there are cracks or delaminations in the microbump MB. 【0069】 As explained above, in the third example of the X-ray inspection method, a tomographic image of the microbump MB is obtained based on the second and third images. In this case, the size of the microbump MB at any height can be obtained. [Modified example] 【0070】 This disclosure is not limited to the embodiments described above. For example, the materials and shapes of each component are not limited to those described above, but can be made from a variety of materials and shapes. 【0071】The processing unit 5 may correct the distortion in the X-ray image. Figure 11(a) is a schematic diagram showing the image of an object, and Figure 11(b) is a schematic diagram showing the image of an object when the object is imaged at a higher magnification than in Figure 11(a). As shown in Figures 11(a) and (b), the greater the magnification, the greater the distortion of the image of the object. The magnitude of this distortion changes depending on the height of the tomographic plane of interest. For this reason, the processing unit 5 may correct the distortion in the X-ray image according to the height of the tomographic plane. 【0072】 In the X-ray inspection apparatus 1, the X-ray source 2 was a so-called transmission-type X-ray source, but the X-ray source 2 may also be a so-called reflection-type X-ray source. 【0073】 The X-ray inspection device 1 may be an inspection device capable of acquiring a radiographic image of an object using radiation other than X-rays (for example, electron beams, beta rays, or gamma rays). In this case, the X-ray source 2 may be a radiation source that generates radiation other than X-rays (for example, electron beams, beta rays, or gamma rays). These radiation sources do not need to have a radiation generating component; for example, in the case of electron beams, the electron beam generated from the electron gun is directly irradiated onto the object. The X-ray detection unit 4 may be a radiation detection unit that detects radiation other than X-rays and acquires a radiographic image of the object based on the detection result. 【0074】 In the X-ray inspection apparatus 1, the control unit 3 controls the X-ray generation position (X-ray focal position) by controlling the incident position of the electron beam EB. However, as described above, if the radiation generating member is omitted from the radiation source, the control unit 3 may directly control the focal position of the radiation emitted from the radiation source between the first focal position and the second focal position. The processing unit 5 may process the first image acquired as a radiation image in the first state where the focal position is the first focal position, and the second image acquired as a radiation image in the second state where the focal position is the second focal position. 【0075】1...X-ray inspection device (radiation inspection device), 2...X-ray source (radiation source), 3...control unit, 4...X-ray detection unit (radiation detection unit), 21...electron gun (beam emission unit), 22...target (radiation generating member), 41...pixel, CA...central axis, LA...optical axis (central axis), MB...microbump, SB...mounted substrate, TH, TH1-TH3...through-hole, Y1...first incident position, Y2...second incident position, Y3...third incident position.

Claims

1. A radiation inspection method comprising: a first control step of controlling the incident position of a beam from a first incident position to a second incident position in a radiation generating member that generates radiation when a beam is incident on it; a second irradiation step of emitting the beam toward the second incident position in the radiation generating member and irradiating a structure provided on a mounting substrate with the radiation; and a second image acquisition step of detecting the radiation that has passed through the structure in a second state where the incident position of the beam is the second incident position, and acquiring a second image which is a radiation image of the structure based on the radiation detection result.

2. A radiation inspection method according to claim 1, further comprising: a first irradiation step of emitting the beam toward the first incidence position and irradiating the structure provided on the mounting substrate with the radiation; and a first image acquisition step of detecting the radiation that has passed through the structure in a first state where the incidence position of the beam is the first incidence position, and acquiring a first image which is a radiation image of the structure based on the radiation detection result, wherein in the first control step, the incidence position of the beam is controlled from the first incidence position to the second incidence position based on the first image.

3. The radiation inspection method according to claim 2, further comprising: a displacement amount acquisition step of acquiring the amount of angular displacement of the structure based on the first image; and a first movement amount acquisition step of acquiring a first movement amount of the incident position of the beam based on the amount of angular displacement, wherein the first control step controls the incident position of the beam from the first incident position to the second incident position based on the first movement amount.

4. The radiation inspection method according to claim 1, further comprising a design information acquisition step of acquiring design information of the structure, wherein the first control step controls the incident position of the beam from a first incident position to a second incident position based on the design information.

5. The radiation inspection method according to claim 1, wherein in the first control step, the incident position of the beam is controlled from a first incident position to a second incident position so that the central axis of the radiation coincides with the central axis of the structure.

6. The radiation inspection method according to claim 1, wherein the mounting substrate has a plurality of structures including the structure formed on it, and further comprises a design information acquisition step of acquiring design information of the plurality of structures, and a second movement amount acquisition step of acquiring a second movement amount of the incident position of the beam based on the design information so that the central axis of the radiation coincides with the central axis of a different structure among the plurality of structures.

7. The radiation inspection method according to claim 1, further comprising: a second control step of controlling the incident position of the beam from a second incident position to a third incident position; a third irradiation step of emitting the beam toward the third incident position in the radiation generating member and irradiating the structure with the radiation; a third image acquisition step of detecting the radiation that has passed through the structure while the incident position of the beam is at the third incident position, and acquiring a third image which is a radiation image of the structure based on the radiation detection result; and a tomographic image acquisition step of acquiring a tomographic image of the structure based on the second image and the third image.

8. The radiation inspection method according to claim 1, wherein the structure is a microbump, a through hole, or a via.

9. A radiation source for irradiating a structure provided on a mounting substrate with radiation, comprising: a beam emission unit for emitting a beam; a radiation generating member for generating radiation when the beam is incident on it; a control unit for controlling the incident position of the beam in the radiation generating member between a first incident position and a second incident position; and a radiation detection unit having a plurality of pixels for detecting the radiation that has passed through the structure, and acquiring a radiation image of the structure based on the radiation detection results by the plurality of pixels, wherein the control unit controls the incident position of the beam from the first incident position to the second incident position, and the radiation detection unit acquires a second image as the radiation image when the incident position of the beam is the second incident position.

Images