Control device, ultrasonic inspection device, and ultrasonic inspection method

Abstract

A control device (7) controls an ultrasonic inspection device (100) that ultrasonically inspects an object (5) to be inspected by irradiation with ultrasonic waves and reception of reflected waves. The control device (7) comprises: an acquisition unit (71) that acquires a first reflected signal received from a first irradiation position of the ultrasonic waves on the object (5) to be inspected and a second reflected signal received from a second irradiation position of the ultrasonic waves on the object to be inspected, the distance between the second irradiation position and the first irradiation position being shorter than the beam diameter of the ultrasonic waves on a surface of interest of the object (5) to be inspected; and an integration unit (72) that integrates the first reflected signal and the second reflected signal to generate an integrated reflected signal.

Description

Control device, ultrasound inspection device, and ultrasound inspection method

[0001] This disclosure relates to a control device, an ultrasound inspection device, and an ultrasound inspection method.

[0002] Ultrasonic inspection equipment generates an inspection image of the desired interface by repeatedly irradiating the object to be inspected (the object being inspected, the sample) from a probe and receiving reflected waves from within, such as at a bonding interface or internal defects. By applying appropriate processing to the inspection image, defects can be detected. In semiconductors, which are the main objects being inspected, the miniaturization and stacking of circuit patterns are progressing, increasing the need for inspections that can detect even minute bonding defects.

[0003] Patent Document 1 describes an ultrasonic imaging device 100 that irradiates an object made of multiple layers with ultrasonic waves to acquire reflected waves from the bonding interface of the object and generates an image of the bonding interface based on the signal intensity of the reflected waves, comprising: a matching processing unit 56 that corrects the phase difference between a second reflected wave from a second irradiation point on the object and a first reflected wave from a first irradiation point on the object; and a pixelation information generation processing unit (averaging processing unit 57) that removes noise from the first reflected wave based on the first reflected wave and the second reflected wave after phase correction, and generates pixelation information of the portion of the bonding interface that returned the interface echo based on the signal intensity of the interface echo that shows the waveform from the bonding interface among the first reflected waves from which the noise has been removed.

[0004] Japanese Patent Publication No. 2024-11497

[0005] The technology described in Patent Document 1 uses multiple different irradiation points (a first irradiation point and a second irradiation point) among the irradiation points of the ultrasonic beam to obtain a clear interface echo with noise removed (paragraphs 0025-0027, Figures 3 and 4, etc.). However, Patent Document 1 does not describe improving detection accuracy by focusing on the beam diameter of the ultrasonic beam to detect minute defects. The problem that this disclosure aims to solve is to provide a control device, an ultrasonic inspection device, and an ultrasonic inspection method that can improve the accuracy of defect detection.

[0006] The control device of the present disclosure is a control device for an ultrasonic inspection apparatus that ultrasonically inspects an object to be inspected by irradiating it with ultrasonic waves and receiving reflected waves, and comprises: an acquisition unit that acquires a first reflected signal received from a first ultrasonic irradiation position on the object to be inspected and a second reflected signal received from a second ultrasonic irradiation position on the object to be inspected, the distance from which to the first irradiation position is shorter than the beam diameter of the ultrasonic waves on the surface of the object to be inspected; and an integration unit that integrates the first reflected signal and the second reflected signal to generate an integrated reflected signal. Other solutions will be described later in the embodiments for carrying out the invention.

[0007] This disclosure provides a control device, an ultrasonic inspection device, and an ultrasonic inspection method that can improve the accuracy of defect detection.

[0008] This is a block diagram illustrating the concept of an ultrasonic inspection apparatus according to the first embodiment. This is a block diagram illustrating the specific hardware configuration of the control device. This is a block diagram illustrating the schematic of an ultrasonic inspection apparatus according to the first embodiment. This is a diagram illustrating the relationship between relatively large defects and the reflection intensity of ultrasound. This is a diagram illustrating the relationship between relatively small defects and the reflection intensity of ultrasound. This is a graph showing the reflection signal when ultrasound is emitted to the defect shown in Figure 4 (example). This is a graph showing the reflection signal when ultrasound is emitted to the defect shown in Figure 5 (example). This is a graph showing the reflection signal when ultrasound is emitted to an object that does not have defects (reference example). This is a flowchart illustrating the ultrasonic inspection method in the first embodiment. This is a diagram illustrating the first irradiation position and the second irradiation position. This is a diagram illustrating the relationship between the ultrasound irradiation position and the position of the defect. This is a flowchart illustrating the method of integrating the reflection signals. This is a graph showing the first reflection signal and one second reflection signal group superimposed before phase correction. This is a graph showing an enlarged view of part A of Figure 13A. This is a graph superimposed so that the peak (local peak) of the second reflection signal and the first reflection signal coincide on the time axis. This is a graph showing the first reflection signal and multiple second reflection signals (reflection signal groups) superimposed before phase correction. This graph shows the first reflected signal and multiple second reflected signals (group of reflected signals) superimposed after phase correction. This graph shows the xy integrated reflected signal obtained after phase correction and weighted addition. This diagram shows the overall process performed in the first embodiment. This flowchart shows the ultrasonic inspection method in the third embodiment. This diagram shows the overall process performed in the third embodiment.

[0009] The following describes embodiments for implementing this disclosure, with reference to the drawings. The following is merely an example of how to implement the invention related to this disclosure, and this disclosure is not limited to the following example. Within the description of one embodiment below, other embodiments applicable to that embodiment will also be described as appropriate. This disclosure is not limited to the following embodiment, and different embodiments can be combined or modified as appropriate without significantly impairing the effects of this disclosure. In addition, the same reference numerals will be used for the same components, and redundant explanations will be omitted. Furthermore, components having the same function will be given the same name. The illustrations are schematic, and for illustrative purposes, the actual configuration may be changed or some components may be omitted or modified between drawings without significantly impairing the effects of this disclosure. Also, the same embodiment does not necessarily need to have all the components.

[0010] Figure 1 is a block diagram illustrating the concept of an ultrasonic inspection apparatus 100 according to the first embodiment. The ultrasonic inspection apparatus 100 is a device that ultrasonically inspects an object to be inspected 5 by irradiating it with ultrasonic waves (incident waves) and receiving reflected waves 4. The object to be inspected 5 is, for example, a multilayer semiconductor (wafer), a miniature electromechanical system (MEMS), a metal structure, etc. In the following example, the object to be inspected 5 is a multilayer semiconductor, and the ultrasonic inspection apparatus 100 inspects for the presence or absence of defects that may exist at the bonding interface (inspection surface) between the stacked semiconductors. The ultrasonic inspection apparatus 100 of this disclosure generates an inspection image of the inspection surface, and can therefore also be called an inspection surface image generation device.

[0011] The ultrasonic inspection apparatus 100 comprises a probe 2 (ultrasonic probe) that irradiates (transmits, emits) ultrasonic waves and receives reflected waves, a flaw detector 3, and a scanning measuring device 13 that drives the probe 2 in the xy direction in a horizontal plane. The flaw detector 3 drives the probe 2 by supplying it with a pulse signal. The scanning measuring device 13 includes an actuator (not shown) that drives the probe 2 in the xy direction (in the xy plane). The ultrasonic inspection apparatus 100 also includes a detection unit 1 that detects defects. In this example, the probe 2, flaw detector 3, and scanning measuring device 13 are provided in the detection unit 1.

[0012] The probe 2, driven by the flaw detector 3 (controlled to emit and receive ultrasonic waves), irradiates the inspection area of ​​a multilayer semiconductor, which is an example of an object to be inspected 5, with ultrasonic waves at predetermined intervals (hereinafter referred to as the scanning pitch). The ultrasonic waves are reflected from the surface of the object to be inspected 5 and from predetermined positions inside the object to be inspected 5 (e.g., bonding interfaces), generating reflected waves 4. The probe 2 receives the reflected waves 4, and the flaw detector 3 processes the reflected waves 4 as needed to convert them into reflected intensity (reflected signal intensity). The converter 6 (A / D converter) converts the converted reflected signal into digital waveform data and inputs it to the control device 7.

[0013] Figure 2 is a block diagram showing the specific hardware configuration of the control device 7. The control device 7 is a device that controls, for example, the operation, driving, etc., of the ultrasound examination apparatus 100. The control device 7 is configured to include, for example, a CPU (Central Processing Unit) 1001, a RAM (Random Access Memory) 1002, a ROM (Read Only Memory) 1003, an I / F (Interface) 1004, a bus 1005, etc. The CPU 1001, RAM 1002, ROM 1003, and I / F 1004 are connected, for example, via the bus 1005. The control device 7 is realized when a predetermined control program (for example, a control method, an ultrasound examination method, an image generation method, etc.) stored in the ROM 1003 is loaded into the RAM 1002 and executed by the CPU 1001. Signals and information are exchanged between the control device 7 and various devices (probe 2, scanning measurement device 13, server, personal computer, etc.) and external networks via the I / F 1004 in hardware terms.

[0014] Returning to Figure 1, the control device 7 receives parameters from the user. The control device 7 is connected to a user interface unit 17 (an example of an output device 8 such as a monitor), and a storage device 18, both of which will be described later. The user interface unit 17 is a monitor, for example, a touch panel type, equipped with input and display functions. The user interface unit 17 displays information such as images of defects detected by the control device 7, the number of defects, the coordinates and dimensions of each defect, and furthermore, the detected defects are color-coded by defect type and superimposed on the wafer. The storage device 18 stores characteristic quantities of defects detected by the control device 7 (size, width, dimensions, aspect ratio, etc.), inspection images, etc.

[0015] The control device 7 comprises an acquisition unit 71, an integration unit 72, an image generation unit 73, a defect detection unit 74, and an output unit 75. The reflected signal (waveform data) from the converter 6 is input to the acquisition unit 71. The integration unit 72 generates an integrated reflected signal, which will be described in detail later. The specific method for generating the integrated reflected signal will be described later. The generated integrated reflected signal is input to the image generation unit 73.

[0016] The image generation unit 73 determines pixel values ​​from the signal intensity of the integrated reflection signal (digital waveform data) obtained by the integration processing by the integration unit 72, and generates an inspection image of, for example, a joint interface on the object to be inspected 5 (a cross-sectional image of a specific joint surface) from the determined pixel values. Specifically, for example, the image generation unit 73 scans the measurement range (region in the xy plane) of the object to be inspected 5 with the scanning measuring device 13, and converts the digital data at each scanning position obtained by analog / digital conversion into grayscale values ​​(for example, 0 to 255 when generating a 256-level image). As a result, the image generation unit 73 generates an inspection image showing a plane in the xy direction (a plane parallel to the surface of the object to be inspected 5) at a specific depth (position in the z direction) from the surface of the object to be inspected 5.

[0017] The defect detection unit 74 detects defects by performing appropriate processing on the inspection image generated by the image generation unit 73, such as binarization. The defect detection unit 74 classifies the detected defects into several types. For example, the defect detection unit 74 classifies them into large voids, small voids, cracks, delaminations, etc., according to their size.

[0018] The output unit 75 integrates inspection results such as information on individual defects (defect type, location, size, etc.) and inspection images (images for observing cross-sections) detected by the defect detection unit 74. The output unit 75 generates output data for the integrated data and outputs it to the output device 8 (for example, a display device such as the user interface unit 17, or another control device).

[0019] Figure 3 is a schematic block diagram of the ultrasonic inspection apparatus 100 according to the first embodiment. Figure 3 shows a Cartesian coordinate system 10 consisting of x, y, and z directions. The x and y directions are, for example, horizontal directions, and the x and y plane is, for example, a horizontal plane. The z direction is, for example, a vertical direction, and is also the height direction.

[0020] The detection unit 1 comprises a scanner stand 11 and a water tank 12 provided on the scanner stand 11. The scanning measurement device 13 is a device that moves the probe 2 in the x, y, and z directions, and is provided on the scanner stand 11 so as to straddle the water tank 12. A holder 15 is attached to the scanning measurement device 13, and the scanner 11 is installed almost horizontally. Water 14 is poured into the water tank 12 to a position (height shown by the dotted line) where the object to be inspected 5 is immersed, and the object to be inspected 5 is placed at the bottom (in the water) of the water tank 12. The water 14 is used to efficiently propagate the ultrasonic waves irradiated from the probe 2 into the interior of the object to be inspected 5. The mechanical controller 16 is part of the control device 7 and drives the scanning measurement device 13 to move the probe 2 in the x, y, and z directions. The mechanical controller 16 drives the scanning measurement device 13 based on control commands from the acquisition unit 71, etc. The flaw detector 3 is also driven by commands from the control device 7.

[0021] Probe 2 emits ultrasonic waves towards the object to be inspected 5 and receives the reflected waves 4 that return from the object to be inspected 5. Probe 2 is mounted on a holder 15 and moves freely in the x, y, and z directions by a scanning measuring device 13. As a result, probe 2 irradiates ultrasonic waves at multiple pre-set measurement points on the object to be inspected 5 while moving in the x and y directions. Simultaneously, probe 2 receives the reflected waves 4. In this way, a cross-sectional image (two-dimensional inspection image) of the joint interface within the measurement range (x and y plane) can be obtained, and the presence or absence of defects can be inspected. Probe 2 is connected to a flaw detector 3 that converts the reflected waves 4 into a reflection intensity signal.

[0022] The parameter setting unit 76 in the control device 7 receives parameters such as measurement conditions (recipes) input from an external source and sets them in the defect detection unit 74 and the output unit 75. The parameter setting unit 76 is connected to the database 77.

[0023] Figure 4 illustrates the relationship between a relatively large defect 42a and the reflection intensity of the ultrasonic beam 41. Figure 5 illustrates the relationship between a relatively small defect 42b and the reflection intensity of the ultrasonic wave. First, as a characteristic of ultrasonic waves, they propagate inside the object being inspected 5, and when there is a boundary where the material properties (acoustic impedance) change, a portion of the waves are reflected. In particular, if there is an air gap, most of the waves are reflected. For this reason, bonding defects (air gaps) such as voids and delaminations can be detected with high sensitivity from the reflection intensity at the bonding interface inside the object being inspected 5.

[0024] The ultrasonic beam 41 (ultrasound), shown in shaded areas, is emitted from the probe 2 toward defects 42a and 42b, and also diffuses away from the probe 2 relative to the defects 42a and 42b. Normally, the height position of the probe 2 is adjusted so that the ultrasonic beam is focused on the bonding interface (surface to be inspected). The ultrasonic beam 41 is narrowed near defects 42a and 42b, as indicated by the pair of opposing arrows in Figures 4 and 5. Therefore, the ultrasonic beam 41 has a finite spread. Hereinafter, the size of this spread will be referred to as the beam diameter. The beam diameter can be defined as the diameter of the circle formed by connecting the parts where the ultrasonic intensity is at a predetermined ratio (e.g., 50%), with the part with the highest ultrasonic intensity (e.g., the center of the ultrasonic beam) as the intensity center.

[0025] The size of defect 42a is relatively large relative to the beam diameter, and its reflected wave can be obtained from the ultrasonic irradiation position. On the other hand, the size of defect 42b (Figure 5) is small relative to the beam diameter, so at the ultrasonic irradiation position, reflected waves from the surrounding area (within the beam diameter) are obtained along with the reflected wave from the defect.

[0026] Figure 6 is a graph showing the reflected signal when ultrasonic waves are emitted towards defect 42a shown in Figure 4 (example). Figure 7 is a graph showing the reflected signal when ultrasonic waves are emitted towards defect 42b shown in Figure 5 (example). Figure 8 is a graph showing the reflected signal when ultrasonic waves are emitted towards an object 5 that does not have defects (reference example). In Figures 6 to 8, the horizontal axis is the signal reception time (time t), and the vertical axis is the intensity (intensity of the reflected signal). The reception time shown on the horizontal axis can be converted to the depth (height position) where the reflected wave 4 was generated. Therefore, the reception time can also be said to be in the z direction. In Figures 6 and 7, the dashed line indicates the time when the reflected wave 4 from the bonding interface containing defects 42a and 42b was received. In Figure 8, the dashed line indicates the time at the same time as in Figures 6 and 7. In Figures 6 to 8, the graphs were measured under the same measurement conditions except for the difference between defects 42a and 42b.

[0027] As shown within the dashed box in Figure 6, a strong reflected wave 4 is obtained from a relatively large defect 42a. However, as shown within the dashed box in Figure 7, the reflected wave 4 from a relatively small defect 42b is buried (averaged) by the reflected wave 4 from the vicinity of defect 42a. As a result, only a signal with almost the same intensity as that of a location without defect 42b is obtained, as shown in Figure 8. Furthermore, even outside the dashed line, electrical noise with an intensity equivalent to that of a minute defect 42b is generated, and this is superimposed on the reflected wave 4 from the junction interface. As a result, the signal intensity across the entire range of the graph shown in Figure 7 is the same as that of the graph in Figure 8 where no defects exist, indicating room for improvement in the accuracy of defect detection.

[0028] Therefore, in this disclosure, in order to obtain a weak reflected signal from a minute defect such as defect 42b, the signal intensities in the xy plane (xy direction) and the time direction (z direction) are, for example, integrated (averaged). This generates an integrated reflected signal, and based on the integrated intensity value, an inspection image in which minute defects are revealed can be generated.

[0029] Figure 9 is a flowchart of the ultrasonic inspection method in the first embodiment. The ultrasonic inspection method of the present disclosure shown in Figure 9 can be performed using the ultrasonic inspection apparatus 100 described above. With reference to Figure 9, the functional parts of the control device 7 provided in the ultrasonic inspection apparatus 100 will also be described as appropriate. The ultrasonic inspection method of the present disclosure is a method of ultrasonically inspecting an object to be inspected 5 by irradiating it with ultrasound and receiving the reflected waves. The ultrasonic inspection method of the present disclosure is also a method for generating an inspection image (defect image), and can therefore be said to be a method for generating an inspection image of the inspection surface.

[0030] The acquisition unit 71 (part of the functional unit) provided in the control device 7 first acquires a first reflected signal received from the first irradiation position P0 (described later with reference to Figures 10 and 11), which is the measurement point of interest (step S101). The first irradiation position P0 is one of the positions where ultrasound is irradiated, for example, the center of the beam circle of the irradiated ultrasound. Therefore, the acquisition unit 71 acquires a first reflected signal received from the first irradiation position P0 of the ultrasound on the object to be inspected 5.

[0031] Next, the acquisition unit 71 acquires the second reflected signals received from one or more second irradiation positions P1 to P8 (described later with reference to Figures 10 and 11) of the ultrasonic waves on the object to be inspected 5 (step S102). The second irradiation positions P1 to P8 are irradiation positions in the xy plane where the distance from the first irradiation position P0 is shorter than the ultrasonic beam diameter 52 (Figure 10) at the surface of the object to be inspected 5 (e.g., the bonding interface). That is, the distance between the first irradiation position P0 and the second irradiation positions P1 to P8 is shorter than the beam diameter 52. In particular, it is preferable to have multiple second irradiation positions P1 to P8. This can further improve the accuracy of defect detection. Hereinafter, multiple second reflected signals may be collectively referred to as a group of reflected signals.

[0032] In the example of this disclosure, the acquisition unit 71 acquires a first reflection signal from the first irradiation position P0 of interest (for inspection purposes) and a second reflection signal from at least one (preferably all) of, for example, one or more second irradiation positions P1 to P8, and integrates these signals. For example, if only the first reflection signal from the first irradiation position P0 is used, the change in the signal (echo) caused by the defect may be small if the defect is too small, and it may be difficult to distinguish it from noise. As a result, minute results may be overlooked.

[0033] Therefore, in the example of this disclosure, at least one second reflected signal from one or more second irradiation positions P1 to P8 that are within the same beam diameter (the distance to the first irradiation position P0 is less than or equal to the beam diameter) is collected, and the collected second reflected signals are integrated with the first reflected signal. The integration generates a single signal (integrated reflected signal). An ultrasonic beam has some beam diameter, even at the focal point (i.e., it is not completely zero), and the ultrasonic beam has a certain degree of spread. Therefore, even if the first irradiation position P0 of interest (the object to be inspected) is different, the reflected signals based on the beam circles of different ultrasonic beams that irradiate the same defect, i.e., the defects that overlap with the ultrasonic beams, contain information about the defect. Conceptually speaking, if the beam circle when irradiating the first first irradiation position P0 is close enough to the beam circle when irradiating the second first irradiation position P0 (the second irradiation position from the perspective of the first first irradiation position P0) that is near the first first irradiation position P0, then these can be used. Therefore, by integrating these to generate an integrated reflection signal, it is possible to generate a reflection signal that emphasizes defects. In this way, the accuracy of detecting minute defects can be improved.

[0034] There is no limit to the size of detectable defects. For example, defects larger than the beam diameter can certainly be detected, but according to this disclosure, defects smaller than the beam diameter can also be detected, such as defects with a size of 1 / 10 to 1 / 20 of the beam diameter (for example, the length of the longest part of the defect).

[0035] These steps S101 and S102 are acquisition steps that acquire a first reflected signal received from a first ultrasonic irradiation position P0 on the object to be inspected 5, and a second reflected signal received from second ultrasonic irradiation positions P1 to P8 on the object to be inspected 5, the second of which is a distance from the first irradiation position P0 that is shorter than the beam diameter of the ultrasonic on the surface of the object to be inspected 5.

[0036] The second irradiation positions P1 to P8 are also one of the positions for irradiating ultrasonic waves, for example, the center of the beam circle of the ultrasonic waves to be irradiated. In other words, by irradiating the inspection object 5 with ultrasonic waves by slightly shifting, for example, from the irradiation position (first irradiation position) of the ultrasonic beam in step S101, the second reflected signals from the second irradiation positions P1 to P8 can be received. Note that the specific positions, number of points, etc. of the second irradiation positions can be input together, for example, to the control device 7 at the time of recipe setting of inspection conditions and the like.

[0037] The shapes of the first irradiation position P0 and the second irradiation positions P1 to P8 can be, for example, a rectangular region, a circular region, a cross region, etc. The second irradiation positions P1 to P8 are, for example, close to the first irradiation position P0.

[0038] FIG. 10 is a diagram for explaining the first irradiation position P0 and the second irradiation positions P1 to P8. In FIG. 10, an inspection interface 50 (a surface extending in the xy direction. For example, a bonding interface) in the inspection object 5 is shown, and the inspection interface 50 is imaged. In the illustrated example, the first irradiation position P0 and the second irradiation positions P1 to P8 are all squares having the same area. As the eight second irradiation positions P1 to P8, four second irradiation positions P2, P4, P5, P7 are at positions adjacent to the four sides of the square first irradiation position P0, and four second irradiation positions P1, P3, P6, P8 are at positions filling the gaps between the second irradiation positions P2, P4, P5, P7 adjacent to the four sides, respectively.

[0039] The circle 51 is the spread of the ultrasonic beam when ultrasonic waves are radiated with the first irradiation position P0 as the center. The ultrasonic beam has a beam diameter 52 (the diameter of the circle 51) at the inspection interface 50 which is the inspection object surface as described above. The ultrasonic beam has the maximum intensity, for example, at the first irradiation position P0, and spreads circularly in a direction away from the first irradiation position P0 while weakening the intensity with the first irradiation position P0 as the center. The first irradiation position P0 and the second irradiation positions P1 to P8 are within the irradiation range of the same ultrasonic beam, and in the illustrated example, are within the circle 51. By setting the positions in this way, it is easy to improve the defect detection accuracy.

[0040] For example, when an ultrasonic beam is irradiated centered on the first irradiation position P0, the intensity of the reflection signal from the first irradiation position (the first reflection signal) is greater than the intensity of the reflection signals from the second irradiation positions P1 to P8 (the second reflection signals). Then, when the probe 2 is slightly shifted and an ultrasonic beam is irradiated centered on, for example, the second irradiation position P1 before the shift, the intensity of the second reflection signal from, for example, the second irradiation position P1 before the shift (which becomes the first reflection signal from the first irradiation position P0 after the shift) is greater than the intensities of the first reflection signals and the second reflection signals at the first irradiation position P0 and the second irradiation positions P2 to P8 before the shift.

[0041] FIG. 11 is a diagram for explaining the relationship between the ultrasonic irradiation position and the position of a defect. Actually, the ultrasonic wave is continuously irradiated in the x direction while fixing, for example, the y-direction position (y coordinate). FIG. 11 shows a state where the irradiation position P0b is regarded as a measurement point with the first irradiation position. FIG. 11 further shows the states when ultrasonic waves are irradiated with the irradiation positions P0a, P0c, and P0d as the first irradiation positions (which are the second irradiation positions when viewed from when the irradiation position P0b is the first irradiation position).

[0042] In FIG. 11, the straight line 54 is the y-direction position of the irradiation position P0a, and the straight line 55 is the y-direction position of the irradiation position P0d. The distance between the straight line 54 and the straight line 55 coincides with the beam diameter 52, and the irradiation positions P0b and P0a, P0c, Pd are all located between the straight line 54 and the straight line 55. Also, the irradiation positions P0a, P0b, P0c, P0d are located inside the same beam diameter 52, and in FIG. 11, the y-direction positions are also within the beam 52, but in FIG. 11, for the sake of illustration, they are shown separated in the x direction.

[0043] The irradiation positions P0a, P0b, P0c, P0d are the centers in the spread of the ultrasonic beam indicated by the circles 51a, 51b, 51c, 51d and are the target measurement points. Among these, here, the irradiation position P0b is the measurement point of interest (the first irradiation position). For example, by changing the xy-direction position of the probe 2, ultrasonic waves can be irradiated to each of the irradiation positions P0a, P0b, P0c, P0d.

[0044] Even when ultrasound is irradiated to irradiation positions P0a, P0b, P0c, and P0d, the defect 53 is located within the spread of the ultrasonic beam indicated by circles 51a, 51b, 51c, and 51d. Preferably, the entire defect 53 is located within circles 51a, 51b, 51c, and 51d, but only a part of the defect 53 may be located within circles 51a, 51b, 51c, and 51d.

[0045] The interior of circle 51b, particularly the irradiation position P0b, completely overlaps with the defect 53. Therefore, at irradiation position P0b, the beam is irradiated near the defect 53 with maximum intensity. As a result, the intensity of the resulting reflected signal is also maximum. On the other hand, the ultrasonic beam is also irradiated at irradiation position P0c, which is slightly offset from the defect 53, and at irradiation positions P0a and P0d, which are significantly offset. However, at these irradiation positions, the ultrasonic waves are irradiated with an intensity lower than the maximum ultrasonic intensity. Since a portion of the defect 53 is contained within the interior of circles 51a, 51c, and 51d, the defect 53 is irradiated with ultrasonic waves, albeit at a weak intensity. As a result, the reflected signal (echo) from the defect 53 can be detected.

[0046] In this way, signals from second irradiation positions (irradiation positions P0a, P0c, P0d) located within the circle 51b, which is within the beam diameter 52 range from the measurement point of interest (irradiation position P0b), are used. Then, by integrating the reflected wave group, which is multiple second reflected signals from multiple second irradiation positions, a reflected wave 4 can be generated that emphasizes the reflected signal from the defect 53. Note that the beam diameter usually differs depending on the specifications of the probe 2. For this reason, irradiation positions P0a, P0c, and P0d can be set for each probe 2 used.

[0047] Returning to Figure 9, in step S103 (integration step), the integration unit 72 (functional unit) integrates the first reflection signal and the second reflection signal to generate an integrated reflection signal. The integration unit 72 integrates the first reflection signal, which is the reflection signal from the first irradiation position P0, and the group of reflection signals from the second irradiation positions P1 to P8 (eight second reflection signals) to generate an xy integrated reflection signal by integrating the reflection signals in the x and y directions. That is, the integration unit 72 generates an xy integrated reflection signal as an example of an integrated reflection signal by integrating the first reflection signal and the second reflection signal in the x and y directions, which indicate the irradiation direction of the ultrasound. The integration process is a concept that corresponds, for example, to the averaging process in Patent Document 1. However, in the example of this disclosure, "weighting," which will be described in detail later, may be performed during integration.

[0048] Figure 12 is a flowchart illustrating a method for integrating reflected signals. For illustrative purposes, Figure 12 also shows the integration in the z-direction (time axis direction), which will be described later. The group of eight second reflected signals consists of reflected signals adjacent to the first reflected signal, but there is a possibility that phase shifts such as jitter, which is a fluctuation in the time axis direction, may occur. Therefore, the integration unit 72 first detects the phase shift in the time axis direction of each of the eight second reflected signals relative to the first reflected signal (step S601). Next, the integration unit 72 corrects each second reflected signal based on the detected shift so that the phase in the time axis direction is aligned (step S602). In other words, a "matching process" is performed in which each second reflected signal is corrected so as to overlap the phase shifts. Steps S601 and S602 can be performed, for example, by the method described in Patent Document 1.

[0049] The integration unit 72 further generates a single xy integrated reflection signal by performing a "weighted addition process" on the first reflection signal and eight second reflection signals that have been "weighted" according to the distance (step S603). The xy integrated reflection signal is obtained through the weighted addition process. The meaning and specific method of weighted addition will be explained with reference to Figures 13 and 14.

[0050] Figure 13A is a graph showing the first reflected signal (solid line) and an arbitrary second reflected signal (dashed line) superimposed before phase correction. Part A, enclosed by a solid line frame, represents the reflected signal (echo) from the joint interface being inspected, and part B, enclosed by a solid line frame, represents the reflected signal (echo) from the surface of the object being inspected 5.

[0051] Figure 13B is an enlarged graph of section A of Figure 13A. Peak 73a is a local peak that is part of the interface echo of the first reflected signal. In the example of this disclosure, the peak of the second reflected signal corresponding to peak 73a, shown by the solid line, is searched for and recognized from the second reflected signal (echo), shown by the dashed line. As a specific recognition method, the normalized cross-correlation coefficients are calculated between peak 73a, shown by the solid line, and each of the corresponding candidate peaks 73b and 73c, shown by the dashed lines, and the candidate with the higher correlation coefficient is selected as the corresponding peak.

[0052] Figure 13C is a graph in which the peak 73c of the second reflected signal and the peak 73a (local peak) of the first reflected signal are superimposed so that they coincide on the time axis. By aligning the phases and superimposing the peaks in this way, multiple reflected signals can be integrated. That is, the integration unit 72 generates an integrated reflected signal by aligning the phase of the first reflected signal with the phase of the second reflected signal. Specifically, for example, by aligning the phases of each second reflected signal with respect to a local peak (e.g., peak 73a) and superimposing the peak 73c corresponding to that local peak, multiple second reflected signals can be integrated into the first reflected signal (phase correction; phase alignment).

[0053] As described above, the intensity of the ultrasonic beam decreases with increasing distance from the center. Therefore, the intensity of the resulting echo also decreases with increasing distance from the center (first irradiation position P0). Consequently, if each second reflected signal constituting the group of reflected signals is treated with the same "weight," i.e., added equally, the intensity of the echo at the defect may actually decrease. Therefore, in the example of this disclosure, a "weight" is assigned according to the distance from the measurement point of interest (first irradiation position P0) (the weight decreases as the distance from the center increases), and the reflection intensities of each reflected signal in the group of reflected signals are added together. In the example of this disclosure, such addition is called "weighted addition."

[0054] In this way, the integration unit 72 generates an xy integrated reflection signal (an example of an integrated reflection signal) using a second reflection signal weighted according to the distance between the first irradiation position P0 and the second irradiation positions P1 to P8. By doing so, the influence of the second reflection signal at positions close to the first irradiation position P0 can be increased, while the influence of the second reflection signal at positions far from the first irradiation position P0 can be decreased. As a result, the xy integrated reflection signal can be generated by effectively using the second reflection signal, which has a higher intensity due to its proximity.

[0055] In the example of this disclosure, when the distance from the measurement point of interest, i.e., the distance between the first irradiation position and the second irradiation position, is the first distance, the integration unit 72 generates an xy integrated reflection signal (an example of an integrated reflection signal) using the second reflection signal multiplied by a first coefficient. The second reflection signal multiplied by the first coefficient is a signal value obtained by multiplying the measured value (intensity) of the second reflection signal by a predetermined first coefficient. Furthermore, when the distance is the second distance, which is longer than the first distance, the integration unit 72 generates an xy integrated reflection signal (an example of an integrated reflection signal) using the second reflection signal multiplied by a second coefficient smaller than the first coefficient. The second reflection signal multiplied by the second coefficient is a signal value obtained by multiplying the measured value (intensity) of the second reflection signal by a predetermined second coefficient. With this weighting, when a defect near the center affects the magnitude of the reflection signal, the xy integrated reflection signal can be generated while appropriately taking that effect into account.

[0056] Weighted addition can be performed based on the following equation (1). Equation (1) is a function that integrates over the range of real numbers m and n, from -1 to 1.

[0057]

[0058] In equation (1), I ｘｙ (t) is the intensity of the integrated reflected signal at coordinate (x, y) at time t. ｘ＋ｍ，ｙ＋ｎis the intensity of the reflected signal at coordinates (x+m, y+n) of a measurement point (e.g., the second irradiation positions P1 to P8) located near the measurement point of interest (e.g., the first irradiation position P0), and k(m,n) is a weighting coefficient (first coefficient, second coefficient, etc.) corresponding to the distance from the measurement point of interest. (The coordinates of the measurement point of interest (P0) are (x, y), the coordinates of the nearby measurement points (P1 to P8) are (x+m, y+n), and the ranges of m and n are -1 ≤ m and n ≤ 1, respectively.)

[0059] The acquisition range of the reflected signal group, the shape of the acquisition region, and the weighting coefficient k(m,n) can be appropriately set according to the beam diameter of the ultrasonic beam and the intensity distribution of the ultrasonic beam. For example, if the intensity distribution of the ultrasonic beam follows a Gaussian distribution, it is preferable that the weighting coefficient k(m,n) also has a Gaussian distribution shape. Alternatively, as shown in Figure 10 above, the reflected signal group may be acquired by focusing on, for example, eight adjacent measurement points, and the weights of all second reflected signals constituting the reflected signal group may be made equal (k(m,n) = 1.0), as described in detail in the second embodiment below. In this case, since weighting addition according to distance is not performed, the integrated reflected signal will be generated in accordance with the method described in Patent Document 1 above.

[0060] Figure 14 is a graph showing the first reflected signal and multiple second reflected signals (group of reflected signals) superimposed before phase correction. That is, Figure 14 is a graph of the first reflected signal and the second reflected signal before step S601 described above. As shown in step S601 described above, the shift on the time axis (horizontal axis) of the peak (local peak) of section C is calculated for the first reflected signal (e.g., echo of the junction interface). Then, the phase of each of the group of reflected signals is corrected based on the calculated shift.

[0061] Figure 15 is a graph showing the first reflected signal and multiple second reflected signals (group of reflected signals) superimposed after phase correction. That is, Figure 15 is a graph of the first reflected signal and the second reflected signals after steps S601 and S602 described above. Due to phase correction, as shown in Figure 15, the peaks (local peaks) in section D coincide on the time axis.

[0062] Figure 16 is a graph showing the integrated xy reflection signal obtained after phase correction and weighted addition. The graph shown in Figure 16 is obtained by going through step S603 described above. The peak in section E is the peak corresponding to sections C and D (the integrated peak obtained by superimposing the first reflection signal and the second reflection signal). By using the graph shown in Figure 16 (signal intensity over time), it is possible to perform defect detection using the integrated reflection signal obtained by integrating multiple reflection signals.

[0063] Returning to Figure 9, in the example of this disclosure, the integration unit 72 further integrates a predetermined range of reception time from the xy integrated reflection signal (an example of an integrated reflection signal) (integrating the signal of the xy integrated reflection signal for a predetermined reception time). This makes it possible to detect even smaller defects and further improve detection accuracy. In the example of this disclosure, the predetermined range of reception time is the z direction, which is the direction of the horizontal axis (time axis t) in Figure 16. Based on this, the integration unit 72 calculates the xyz integrated intensity value (step S104). That is, in the example of this disclosure, the presence of a defect is determined using the xy integrated reflection signal, but more specifically, the presence of a defect is determined based on the xyz integrated intensity value obtained using the xy integrated reflection signal.

[0064] In Figure 12 above, the integration unit 72 sets a range Tw (a predetermined time range) to be integrated in the time axis direction in the xy integrated reflection signal (step S604). The range Tw is like an imaging gate in an ultrasound examination device, for example. Conventionally, the maximum intensity within the imaging gate (time range Tw) was searched for, and the maximum intensity was converted into a pixel value, and the resulting pixel value was used to create an image. On the other hand, in the example of this disclosure, the signal intensity in the time range Tw is integrated, and the integrated intensity is converted into a pixel value, and the resulting pixel value can be used to create an image.

[0065] The xy integrated reflection signal has positive and negative values, as shown in Figure 16 above. Therefore, the integration unit 72 converts the xy integrated reflection signal within the time range Tw (Figure 17) to absolute values ​​(step S604). This allows the sum of the areas in the graph to be calculated when the signals are integrated (i.e., integrated). The integration unit 72 then further integrates the signal intensity within the range Tw, which is a predetermined range of reception time, of the generated xy integrated reflection signal with the generated xy integrated reflection signal. This allows the presence of defects to be determined taking time into account. In the example of this disclosure, the integration unit 72 adds all signals that are positive within the range Tw according to the following formula (2) (step S606). This calculates C(x,y), which represents the xyz integrated intensity value at the measurement point coordinates (x,y).

[0066]

[0067] In equation (2), st is the start time of range Tw, and et is the end time of range Tw.

[0068] In equation (2), all signals within range Tw are added with uniform weights to calculate the integrated intensity value. However, for example, the maximum intensity within range Tw may be identified, and the values ​​obtained by adding weights within a fixed time before and after the maximum intensity, i.e., the convolution integral value obtained by weighted addition, may be used as the xyz integrated intensity value. In either calculation method, the xyz integrated intensity value can be calculated by integrating the xy integrated reflected signal values ​​in the time axis direction within a specific gate.

[0069] The integration range Tw is a parameter predetermined based on the duration (pulse width) of a single wave, which varies depending on the specifications of the probe 2. If Tw = 1, integration in the time direction does not occur. Therefore, the integration unit 72 determines the range Tw, which is a predetermined range of reception time, based on the duration of the irradiated ultrasound, and generates an integrated reflected signal within the determined Tw. In this way, integration can be performed under conditions that conform to the specifications of the probe 2.

[0070] As described above, in the first embodiment, the integration unit 72 first integrates the first reflection signal and the second reflection signal in the xy direction, which indicate the direction of ultrasonic irradiation, to generate an xy integrated reflection signal. Furthermore, the integration unit 72 further integrates the signal intensity within a predetermined range Tw of the reception time of the generated xy integrated reflection signal with the generated xy integrated reflection signal. This enables the generation of an xyz integrated reflection signal, and the pixel values ​​used for imaging the inspection target surface (bonding interface) can be calculated from the integrated intensity values.

[0071] In the flow shown in Figure 9, the image generation unit 73 uses the pixel value determined from the signal intensity of the integrated xy reflection signal as the pixel value of the first irradiation position P0, and generates an inspection image 95 from this pixel value (step S105). This allows the inspection image to be displayed on a display device such as the output device 8, or transmitted to any server. For example, if the image generation unit 73 is generating an 8-bit inspection image 95, it converts the distribution of the integrated xyz intensity values ​​to a range of 0 to 255.

[0072] In the example of this disclosure, the pixel values ​​used in step S105 are values ​​based on xyz intensity values ​​determined from the signal intensity of the xy integrated reflection signal. If integration is not performed in the time range Tw, i.e., if step S104 is not performed, the inspection image 95 may be generated from pixel values ​​directly determined from the signal intensity of the xy integrated reflection signal generated in step S103.

[0073] By performing steps S101 to S105 shown in Figure 9 for all measurement points in the inspection area, an inspection image can be generated.

[0074] Figure 17 shows the overall process performed in the first embodiment. Ultrasound is irradiated onto the inspection area 90 (xy plane) of the object to be inspected, with the probe 2 scanning from the upper left to the lower right, at a predetermined scanning pitch. As a result, reflected waves from the object to be inspected 5 are received, and reflected signals from the inspection surface (e.g., bonding interface) are obtained from each point of interest measurement point (first irradiation position P0) within the inspection area 90. Two reflected signals are obtained: the first is the reflected signal 91 of the point of interest measurement point (including the reflected signal 91a on the inspection surface), and the second is the group of reflected signals 92 of measurement points within the ultrasonic beam diameter (in this case, eight nearby measurement points). Then, by integrating the reflected signal 91 and the group of reflected signals 92, a graph 93 of the xy integrated reflected signal is generated.

[0075] Furthermore, as shown in Graph 94, the integrated reflection signal C(t) is calculated by integrating the reflection signals in the range Tw(st to et) in Graph 93 of the integrated xy reflection signal. The integrated reflection signal C(t) is the formula that forms the basis of the above-mentioned integrated xyz signal value, and the integrated intensity value I of xyz is derived from the integrated reflection signal C(t). ｘｙｚ The following is calculated: xyz integrated intensity value I ｘｙｚ This is converted to a value such as 8 bits, and the converted value is used as the pixel value of the measurement point 96 (first irradiation position P0).

[0076] By performing the above process for all measurement points, an inspection image 95 is generated. The generated inspection image 95 is input to the defect detection unit 74, where a defect determination is performed and defects are detected.

[0077] In the first embodiment described above, the time-axis processing shown in step S104 is performed. However, in the second embodiment, the time-axis processing shown in step S104 is not performed. Therefore, the inspection image 95 is generated from the xy integrated reflection signal. For example, in the time range st to et of the xy integrated reflection signal in Figure 17, the intensity of the maximum negative peak I ｘｙ This is converted to the pixel value of the measurement point of interest, as shown by the dashed line in the figure. However, depending on the characteristics and specifications of probe 2, a positive peak may be used instead of a negative peak.

[0078] Whether or not to perform integration in the time axis direction, that is, whether to perform control according to the first embodiment or control according to the second embodiment, can be fixed to one or the other in advance, depending on the functions and specifications of the ultrasonic inspection device 100. However, for example, the ultrasonic inspection device 100 (particularly the control device 7) may be designed so that the control of the first embodiment and the control of the second embodiment can be arbitrarily selected and executed, and either one can be selected and executed according to the user's request (selection). For example, if the control of the first embodiment is performed, integration in the time axis direction is also performed, so the accuracy of defect detection can be further improved. On the other hand, if the control of the second embodiment is performed, integration in the time axis direction is not performed, so the calculation time can be shortened and the inspection time can be shortened.

[0079] In the third embodiment, the integration in the x and y directions and the integration in the z direction (time direction) are reversed compared to the first embodiment. That is, in the third embodiment, the integration unit 72 generates a first integrated signal by integrating the reflected signals within a predetermined range Tw of the first reflected signal in the x and y directions, which is within a predetermined range of reception time. At the same time, the integration unit 72 generates a second integrated signal by integrating the reflected signals within the same predetermined range Tw of the second reflected signal in the x and y directions, which is within a predetermined range of reception time. Furthermore, the integration unit 72 integrates the first integrated signal and the second integrated signal. Even in this way, an inspection image 95 can be generated.

[0080] Specifically, the integration unit 72 aligns the phases of the first reflected signal and the group of reflected signals (multiple second reflected signals) along the time axis. Then, for each of the phase-aligned group of reflected signals, the integration unit 72 calculates a group of z-integrated intensity values ​​by integrating the signals within the range Tw. Furthermore, the integration unit 72 weights and adds the z-integrated intensity values ​​of measurement points adjacent to the first irradiation position P0 (the second irradiation positions P1 to P8 from which the second reflected signals are acquired) according to their distance from the first measurement point (first irradiation position P0). The obtained xyz combined intensity values ​​are converted into pixel values ​​of the first measurement point to generate the inspection image 95.

[0081] Figure 18 is a flowchart showing the ultrasonic inspection method in the third embodiment. In the same manner as steps S101 and S102, a first reflection signal and a group of reflection signals are acquired. Next, the integration unit 72 integrates the reflection signals within a range Tw in the time axis direction (z direction) for each of the first reflection signal and the group of reflection signals, and generates a z-integrated reflection signal group (S1003). The specific integration method in the time axis direction can adopt the method described in the first embodiment. Next, the integration unit 72 calculates a z-integrated intensity value group (step S1004). Step S1004 will be described while referring to FIG. 19.

[0082] Figure 19 is a diagram showing the overall process performed in the third embodiment. When ultrasonic waves are irradiated to and reflected from the inspection target region 90 in the same manner as in the first embodiment, a graph 111 in which the respective reflection signals from the target measurement point (first irradiation position P0) and, for example, its adjacent 8 neighboring measurement points (second irradiation positions P1 to P8) are superimposed is obtained. Among these, by performing convolution integration within the range Tw for, for example, any three reflection signals, a z-integrated reflection signal group (I ｚ (t)) shown in graph 112 is obtained.

[0083] The start time st of the range Tw is different for each. In the example of the present disclosure, a z-integrated intensity value is calculated from each z-integrated reflection signal (step S1004). These calculated z-integrated intensity values are collectively referred to as a z-integrated intensity value group. As an example of the method for calculating the z-integrated intensity value, the maximum intensity (C ｚ 、C Ｚ１ 、C Ｚ２ 、C Ｚ３ ) of each I ｚ (t) shown in graph 112 can be used. As another example, the sum of I

[0084] (t) can be used. Ｚ１ 、C Ｚ２ 、C Ｚ３A weight is assigned to each of the following points (,,,) according to the distance from the measurement point of interest (first irradiation position P0). Specifically, for example, as in the first embodiment described above, the weight decreases as the distance from the center increases. Then, by adding the weights in the same manner as in the first embodiment, the xyz integrated intensity value C(x,y) at the measurement point coordinates (x,y) is calculated (step S1005). Step S1005 is an integration step in which a first reflection signal, which has been integrated in the time axis direction in advance, and a second reflection signal (group of reflection signals), which has also been integrated in the time axis direction in advance, are integrated to generate an xyz integrated reflection signal (an example of an integrated reflection signal). Next, as in the same manner as in the first embodiment described above, the xyz integrated intensity value C(x,y) is converted to a pixel value and an inspection image 95 is generated (step S1006).

[0085] In the third embodiment, first, the integrated intensity value in the time axis direction for each group of reflected signals is uniquely calculated within Tw. This has the advantage that it is not necessary to perform phase alignment of each reflected wave.

[0086] 1 Detection unit 10 Cartesian coordinate system 100 Ultrasonic inspection device 13 Scanning measurement device 2 Probe 3 Flaw detector 4 Reflected wave 5 Object to be inspected 7 Control device 71 Acquisition unit 72 Integration unit 73 Image generation unit 74 Defect detection unit 75 Output unit 76 Parameter setting unit 77 Database 8 Output device

Claims

1. A control device for controlling an ultrasonic inspection apparatus that ultrasonically inspects an object to be inspected by irradiating it with ultrasonic waves and receiving reflected waves, comprising: an acquisition unit that acquires a first reflected signal received from a first ultrasonic irradiation position on the object to be inspected, and a second reflected signal received from a second ultrasonic irradiation position on the object to be inspected, the distance between the second irradiation position and the first irradiation position being shorter than the beam diameter of the ultrasonic waves on the surface of the object to be inspected; and an integration unit that integrates the first reflected signal and the second reflected signal to generate an integrated reflected signal.

2. The control device according to claim 1, wherein the integration unit generates the integrated reflected signal by aligning the phase of the first reflected signal with the phase of the second reflected signal.

3. The control device according to claim 2, wherein the integration unit further integrates a predetermined range of reception time from the integrated reflected signal.

4. A control device according to claim 1, wherein the integration unit generates an xy integrated reflection signal as the integrated reflection signal by integrating the first reflection signal and the second reflection signal in the xy direction indicating the irradiation direction of the ultrasonic wave, and further integrates the signal intensity within a predetermined range of reception time from the generated xy integrated reflection signal with respect to the generated xy integrated reflection signal.

5. A control device according to claim 1, wherein the integration unit generates a first integrated signal by integrating the first reflected signals in the x and y directions within a predetermined range of reception time, and generates a second integrated signal by integrating the second reflected signals in the x and y directions within the predetermined range of reception time, and further integrates the first integrated signal and the second integrated signal.

6. The control device according to claim 1, characterized in that it comprises an image generation unit that generates an inspection image from pixel values ​​determined from the signal intensity of the integrated reflection signal.

7. A control device according to claim 1, characterized in that the integration unit generates the integrated reflection signal using the second reflection signal weighted according to the distance.

8. A control device according to claim 7, wherein the integration unit generates the integrated reflection signal by using the second reflection signal multiplied by a first coefficient when the distance is a first distance, and by using the second reflection signal multiplied by a second coefficient smaller than the first coefficient when the distance is a second distance which is longer than the first distance.

9. A control device according to claim 1, wherein the integration unit determines a predetermined range of reception time based on the duration of the irradiated ultrasonic wave, and generates the integrated reflected signal within the predetermined range of reception time.

10. A control device according to claim 1, characterized in that the first irradiation position and the second irradiation position are located within the same ultrasonic beam irradiation range.

11. A control device according to claim 10, characterized in that a plurality of the second irradiation positions are arranged.

12. An ultrasonic inspection apparatus comprising: a control device according to claim 1; a probe for irradiating ultrasonic waves and receiving reflected waves; and a scanning measuring device for driving the probe in the x and y directions.

13. An ultrasonic inspection method for ultrasonically inspecting an object to be inspected by irradiating it with ultrasonic waves and receiving reflected waves, comprising: an acquisition step of acquiring a first reflected signal received from a first irradiation position of the ultrasonic waves on the object to be inspected, and a second reflected signal received from a second irradiation position of the ultrasonic waves on the object to be inspected, wherein the distance between the second irradiation position and the first irradiation position is shorter than the beam diameter of the ultrasonic waves on the surface of the object to be inspected; and an integration step of integrating the first reflected signal and the second reflected signal to generate an integrated reflected signal.

Images