Inspection equipment, inspection methods and inspection procedures

Abstract

This invention provides an inspection apparatus that can perform three-dimensional analysis of the connection path of even fine and complex wiring leads in a short time using fewer images. The inspection apparatus is for inspecting the wiring leads connecting a substrate and a semiconductor wafer. The apparatus includes: a first imaging unit for viewing the semiconductor wafer from above, wherein an optical system and imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface of the substrate becomes the focal plane, and the first imaging unit has an aperture adjusted such that the loop height of the connection lead being inspected converges to the depth of field; a second imaging unit for viewing the semiconductor wafer from a direction different from the viewing direction of the first imaging unit; and an analysis unit that performs three-dimensional analysis of the connection path of the connection leads by comparing a first image output by the first imaging unit with a second image output by the second imaging unit.

Description

[Technical Field]

[0001] This invention relates to an inspection device, inspection method, and inspection procedure. [Previous Technology]

[0002] A known apparatus is used to check whether the bonding leads are properly connected in a mounting body that connects a substrate electrode on a substrate to a wafer electrode of a semiconductor wafer fixed to the substrate using bonding leads. For example, according to the technology of Patent Document 1, an optical system that reduces depth of field is used to take multiple pictures of the bonding leads while changing the focus height, and the XY coordinates of the leads at each focus height are detected to obtain the overall three-dimensional information of the bonding leads. Alternatively, according to the technology of Patent Document 2, which employs a different method, grid stripes are projected onto the bonding leads, and pictures are taken using two or more imaging units. The three-dimensional information of the bonding leads is calculated based on the offset of the corresponding grid points in each image. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-75429 [Patent Document 2] Japanese Patent Application Publication No. 10-54709 [Summary of the Invention]

[0004] [Problems to be Solved by the Invention] According to the technology of Patent Document 1, since multiple shots of the observed object need to be taken while the focus height is moved, a large amount of time is required. In addition, since the shot needs to be taken from directly above, there is a constraint that the jointing leads cannot be crossed when viewed from the height direction. According to the technology of Patent Document 2, since grid points need to be projected onto the surface of the fine jointing leads, there is a problem that a fine grid pattern is required, and it is difficult to distinguish corresponding grids between images.

[0005] This invention addresses this problem by providing an inspection device that can perform three-dimensional analysis of even fine and complex wiring connections using fewer images in a short time. [Means for Solving the Problem]

[0006] The first aspect of the inspection apparatus of the present invention is an apparatus for inspecting bonding leads that are connected between a substrate and a semiconductor wafer. The inspection apparatus includes: a first imaging unit for viewing the semiconductor wafer from above, wherein an optical system and an imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface of the substrate becomes the focal plane, and the first imaging unit has an aperture that is adjusted such that the loop height of the bonding lead to be inspected converges to the depth of field; a second imaging unit for viewing the semiconductor wafer from a direction different from the viewing direction of the first imaging unit; and an analysis unit for performing three-dimensional analysis of the bonding lead connection path by comparing a first image output by the first imaging unit with a second image output by the second imaging unit.

[0007] Furthermore, the second aspect of the inspection method of the present invention is a method for inspecting bonding leads that are connected between a substrate and a semiconductor wafer. The inspection method includes: a first imaging step, in which a first imaging unit is used to take an overhead photograph of the semiconductor wafer to be inspected, wherein the first imaging unit is configured such that an optical system and an imaging element are arranged such that a plane parallel to the surface of the substrate becomes the focal plane to satisfy the Cyinfluence condition, and the first imaging unit has an aperture that is adjusted such that the loop height of the bonding lead to be inspected converges to the depth of field; a second imaging step, in which a second imaging unit is used to take an overhead photograph of the semiconductor wafer from a direction different from the overhead direction of the first imaging unit; and an analysis step, in which a three-dimensional analysis of the bonding lead connection path is performed by comparing a first image output by the first imaging unit with a second image output by the second imaging unit.

[0008] Furthermore, the third aspect of the inspection program of the present invention is a program for inspecting the bonding leads that connect between a substrate and a semiconductor wafer. The inspection program causes a computer to perform the following steps: a first imaging step, in which a first imaging unit is used to take an overhead photograph of the semiconductor wafer to be inspected. In the first imaging unit, the optical system and the imaging element are configured such that a plane parallel to the surface of the substrate becomes the focal plane, satisfying the Cyinfluence condition. The first imaging unit also has an aperture that is adjusted so that the loop height of the bonding lead to be inspected converges to the depth of field; a second imaging step, in which a second imaging unit is used to take an overhead photograph of the semiconductor wafer from a direction different from the overhead direction of the first imaging unit; and an analysis step, in which a three-dimensional analysis of the bonding lead's connection path is performed by comparing the first image output by the first imaging unit with the second image output by the second imaging unit. [Effects of the Invention]

[0009] According to the present invention, an inspection device can be provided that can perform three-dimensional analysis of the connection path in a short time using fewer images, even for connection leads that are thin and complex.

Implementation Method

[0011] Hereinafter, the present invention will be described through embodiments of the invention, but the invention covered by the claims is not limited to the following embodiments. Furthermore, all structures described in the embodiments are not necessarily means for solving the problem. Moreover, in the figures, those marked with the same symbols have the same or identical structures. Additionally, in the figures, when multiple structures with the same or identical structures exist, to avoid clutter, sometimes some symbols are marked while others are omitted.

[0012] FIG1 is a perspective view schematically showing the main parts of the inspection device 100 of this embodiment. The inspection device 100 includes a platform 190 and a first imaging unit 130, a second imaging unit 140, a third imaging unit 150, a fourth imaging unit 160, and a fifth imaging unit 170 disposed at a position overlooking the platform 190. In the figure, each imaging unit is shown as floating in a hollow manner, but is actually supported by a frame or the like.

[0013] The mounting body 300 placed on the stage 190 is the object of observation of the inspection device 100. The mounting body 300 mainly includes a substrate 320, a semiconductor wafer 330 fixed on the substrate 320, and a plurality of bonding leads 310 electrically connecting the substrate 320 and the semiconductor wafer 330. The mounting body 300 may be in a state before monolithization, in which a plurality of mounting bodies 300 are arranged in a planar direction. In this case, the stage 190 may include a moving mechanism that moves the mounted body 300 in a planar direction so that the mounting body 300, as the object of observation, is positioned at an observation position (e.g., the center) on the stage 190. Furthermore, the substrate before monolithization in which a plurality of mounting bodies 300 are arranged in a planar direction is in a single-plate state, but in this embodiment, the portion corresponding to each individual mounting body 300 after monolithization will be described as the substrate 320. The bonding leads are conductors such as gold, copper, or aluminum, but are not limited to these as long as they are made of a material that can be used as bonding leads.

[0014] In the description of this embodiment, as shown in the figures, the direction along one side of the substrate 320 is defined as the X-axis direction, and the direction along the other side of the substrate 320, orthogonal to the X-axis direction, is defined as the Y-axis direction. In the following description, the XY direction is sometimes referred to as the planar direction. Furthermore, the direction orthogonal to both the X-axis and Y-axis directions is defined as the Z-axis direction. In the following description, the Z-axis direction is sometimes referred to as the height direction, the positive Z-axis direction is referred to as upward, and the negative Z-axis direction is referred to as downward. Additionally, in the following figures, the orientation of the structures represented in each figure is indicated by the same coordinate axes based on the state in which the inspection device 100 is set as shown in Figure 1.

[0015] The first imaging unit 130 is configured to view the mount 300 disposed on the stage 190 from the positive X-axis direction toward the negative X-axis direction. The second imaging unit 140 is configured to view the mount 300 disposed on the stage 190 from the negative X-axis direction toward the positive X-axis direction. That is, the first imaging unit 130 and the second imaging unit 140 are disposed on opposite sides of each other with respect to the semiconductor wafer 330 located at the center of the mount 300, which is the object of observation.

[0016] The first imaging unit 130 includes a first imaging element 131 and a first optical system 132. Details will be described later. The first imaging element 131 and the first optical system 132 are configured to satisfy the Scheimpflug condition, with a plane parallel to the surface of the substrate 320 serving as the focal plane. Similarly, the second imaging unit 140 includes a second imaging element 141 and a second optical system 142. Details will be described later. The second imaging element 141 and the second optical system 142 are configured to satisfy the Scheimpflug condition, with a plane parallel to the surface of the substrate 320 serving as the focal plane. The first imaging unit 130 and the second imaging unit 140 are each controlled by an imaging control unit (described later), which sends image data generated by capturing images of the mounting body 300 according to imaging instructions to the imaging control unit.

[0017] The third imaging unit 150 is configured to view the mounting body 300 disposed on the stage 190 from the positive Y-axis direction toward the negative Y-axis direction. The fourth imaging unit 160 is configured to view the mounting body 300 disposed on the stage 190 from the negative Y-axis direction toward the positive Y-axis direction. That is, the third imaging unit 150 and the fourth imaging unit 160 are disposed on opposite sides of each other with respect to the semiconductor wafer 330 located at the center of the mounting body 300, which is the object of observation.

[0018] The third imaging unit 150 includes a third imaging element 151 and a third optical system 152. Details will be described later. The third imaging element 151 and the third optical system 152 are configured to satisfy the Cyinfluence condition, with a plane parallel to the surface of the substrate 320 serving as the focal plane. Similarly, the fourth imaging unit 160 includes a fourth imaging element 161 and a fourth optical system 162. Details will be described later. The fourth imaging element 161 and the fourth optical system 162 are configured to satisfy the Cyinfluence condition, with a plane parallel to the surface of the substrate 320 serving as the focal plane. The third imaging unit 150 and the fourth imaging unit 160 are each controlled by the imaging control unit described later, and image data generated by capturing images of the mounting body 300 according to the imaging instruction is sent to the imaging control unit.

[0019] The fifth imaging unit 170 is configured to view the mounting body 300 on the stage 190 from directly above. The fifth imaging unit 170 includes a fifth imaging element 171 and a fifth optical system 172. The configuration of the fifth imaging element 171 and the fifth optical system 172 is different from the configuration of the imaging elements and optical systems of the first imaging units 130 to the fourth imaging units 160, and is the same as the configuration of a general imaging unit parallel to the imaging surface and the focal plane. The fifth imaging unit 170 is controlled by the imaging control unit described later, and sends the image data generated by imaging the mounting body 300 according to the imaging instruction to the imaging control unit.

[0020] FIG2 is a schematic perspective view of the mount 300, which is the object of inspection. In this embodiment, as described above, in the mount 300, which is the object of inspection, a semiconductor wafer 330 is fixed on a substrate 320 and electrically connected to each other by a plurality of bonding leads 310. More specifically, each bonding lead 310 connects a plurality of substrate electrodes 321 disposed on the substrate 320 to a plurality of wafer electrodes 331 disposed on the semiconductor wafer 330 one-to-one. The inspection apparatus 100 analyzes how each bonding lead 310 follows a three-dimensional wiring path between the substrate electrodes 321 and the wafer electrodes 331.

[0021] In this embodiment, in the mounting body 300, which is the object of inspection, the substrate 320 and the semiconductor wafer 330 are both approximately square, and the semiconductor wafer 330 is deposited on the substrate 320 with its side edges parallel to each other. A plurality of bonding leads 310 connecting the semiconductor wafer 330 and the substrate 320 are divided into: a first group 311, extending from the first and second sides of the four side edges of the semiconductor wafer 330 that are parallel to each other along the X-axis toward the substrate 320; and a second group 312, extending from the third and fourth sides that are parallel to each other along the Y-axis toward the substrate 320. Details will be described later. The connection paths of the bonding leads 310 in the first group 311 are mainly analyzed by comparing the first image output by the first imaging unit 130 with the second image output by the second imaging unit 140. The connection paths of the bonding leads 310 in the second group 312 are mainly analyzed by comparing the third image output by the third imaging unit 150 with the fourth image output by the fourth imaging unit 160.

[0022] Two reference marks 322, for example, in a cross shape, are provided diagonally at the periphery of the substrate 320. In the analysis of the junction line path, the images of these reference marks 322 are used as reference positions to determine the coordinate system. Furthermore, the reference marks 322 may not be indicators specifically provided on the substrate 320; for example, the pattern of a specific substrate electrode 321 may also be used as a reference mark 322.

[0023] Figure 3 is an explanatory diagram illustrating the Cyinflux optical system and its depth of field used in the first to fourth imaging units 130. The combination of the first imaging unit 130 and the second imaging unit 140 differs from the combination of the third imaging unit 150 and the fourth imaging unit 160 only in that they are arranged along the X-axis or along the Y-axis. Therefore, the combination of the first imaging unit 130 and the second imaging unit 140 will be described here as representative.

[0024] First, the configuration conditions of the imaging element and optical system in the Cyinfluence optical system will be explained using the first imaging unit 130. In FIG3, plane S1 is a plane including the substrate surface 320a, which is the surface of the substrate 320, and is a predetermined focal plane. Imaginary plane S2 is a plane including the principal plane of the first optical system 132, which is composed of object-side lens group 132a and image-side lens group 132b. Plane S3 is a plane including the light-receiving surface of the first imaging element 131. When the first imaging element 131 and the first optical system 132 are configured to satisfy the Cyinfluence conditions, as shown in the figure, plane S1, imaginary plane S2, and plane S3 intersect each other on a common straight line P1. In other words, the first imaging element 131 and the first optical system 132 configured to satisfy the Cyinfluence conditions can make the plane that is obliquely intersecting the light-receiving surface of the first imaging element 131 the focal plane. Therefore, even if the first imaging unit 130 is positioned at a position overlooking the mounting body 300 from an inclined direction, the substrate surface 320a can become the focal plane.

[0025] The aperture 133 is positioned between the object-side lens group 132a and the image-side lens group 132b, restricting the passing light beam. Specifically, in the inspection device 100 of this embodiment, the depth of field DP is adjusted to a certain range by adjusting the diameter of the aperture 133. Specifically, the depth of field DP is adjusted to include the ring height HW, which is the maximum height of the bonding lead 310 belonging to the first group 311. Here, the ring height HW is a value greater than the height of the bonding lead 310 when it is connected according to the design value, for example, a value set to be more than 110% and less than 130%. If this setting is made, even if the bonding lead 310 is actually connected with a height offset of less than 30% relative to the design value, the entire bonding lead 310 can be photographed in focus, and the wiring path can be appropriately detected as described later. Furthermore, in the diagram, the depth of field DP is represented by a line parallel to the plane S1, which serves as the predetermined focal plane. However, in the Cyinflux optical system, the actual depth of field DP is narrow on one side of the line P1 and widens as it moves away from the line P1. In this embodiment, the narrowest depth of field DP within the shooting range of the mounting body 300 can be adjusted as described above.

[0026] Furthermore, in the example shown in the figure, the plane S1, which serves as the predetermined focal plane, is set to include the substrate surface 320a. However, as long as the depth of field DP includes the ring height HW, the plane S1 only needs to be a plane parallel to the substrate surface 320a. For example, the plane S1 can be set to coincide with the plane that divides the ring height HW in two. In addition, in order to achieve this inclusion relationship, the stage 190 can be positioned vertically relative to the first imaging unit 130 and the second imaging unit 140.

[0027] In this embodiment, telecentricity on the object side is achieved by the object-side lens group 132a. Therefore, in the oblique focal planes, whether the subject is located on the near-front side (positive X-axis side) or the inside side (negative X-axis side), as long as the subject is of the same size, it can be imaged at the same magnification on the light-receiving surface of the first imaging element 131. That is, since there is no perspective in the depth direction of the subject, it is not necessary to perform magnification / reduction conversion corresponding to the position of the subject in the depth direction in the captured image, and the three-dimensional analysis described later can be performed easily.

[0028] The second imaging unit 140 has the same structure as the first imaging unit 130 and is symmetrically arranged with respect to the YZ plane to capture images of the mounting body 300 at the center of the field of view. Specifically, the second imaging unit 140 includes a second imaging element 141 and a second optical system 142 consisting of an object-side lens group 142a and an image-side lens group 142b. The second imaging element 141 and the second optical system 142 are configured to satisfy the Cyinfluence condition with the plane S1 as the focal plane. An aperture 143 is disposed between the object-side lens group 142a and the image-side lens group 142b. The diameter of the aperture 143 is adjusted to achieve a depth of field DP including the ring height HW.

[0029] Furthermore, as long as the ring height HW is included, the depth of field DP of the first imaging unit 130 and the depth of field DP of the second imaging unit 140 may also be different. Similarly, as long as the depth of field DP includes the ring height HW, the focal plane of the first imaging unit 130 and the focal plane of the second imaging unit 140 may also not be the same plane.

[0030] In addition, as described above, the third shooting unit 150 and the fourth shooting unit 160 are provided for shooting the bonding leads 310 belonging to the second group 312. For example, if the stage 190 can rotate around the Z-axis, the first shooting unit 130 and the second shooting unit 140 can be used to shoot the bonding leads 310 of the second group 312 from the orthogonal direction, so the setting of the third shooting unit 150 and the fourth shooting unit 160 can be omitted.

[0031] Next, the main system structure of the inspection device 100 will be described. Figure 4 is a system structure diagram of the inspection device 100. The control system of the inspection device 100 mainly includes an arithmetic processing unit 110, a storage unit 121, an input / output device 123, and first imaging units 130 to fifth imaging units 170.

[0032] The arithmetic processing unit 110 is a processor (central processing unit (CPU)) that performs control and program execution processing of the inspection device 100. The processor may also be configured to cooperate with an arithmetic processing chip such as an application-specific integrated circuit (ASIC) or a graphics processing unit (GPU). The arithmetic processing unit 110 reads the inspection program stored in the storage unit 121 and performs various processes related to the inspection of the bonding leads 310.

[0033] Storage unit 121 is a non-volatile storage medium, such as a hard disk drive (HDD). In addition to storing the program for controlling or processing the inspection device 100, storage unit 121 can also store various parameter values, functions, lookup tables, etc., used for control or calculation. Storage unit 121 specifically stores path information 122. Specific details regarding path information 122 will be described later, including information about the substrate 320 and the semiconductor wafer 330, and information about the reference path recorded based on the design values ​​of the respective bonding leads 310 that connect these components. Furthermore, a portion of storage unit 121 can also be connected via a network.

[0034] Input / output device 123 includes, for example, a keyboard, mouse, display monitor, and network interface, and is a device that accepts user-based menu operations or provides information to the user. For example, the processing unit 110 can display images captured by each imaging unit on the display monitor, which is one of the input / output devices 123. When the storage unit 121 is connected to a network, the processing unit 110 obtains the required information or programs from the storage unit 121 via the network interface, which is one of the input / output devices 123.

[0035] The arithmetic processing unit 110 also functions as an arithmetic unit, performing various calculations according to the instructions of the inspection program. The arithmetic processing unit 110 can function as the shooting control unit 111, the acquisition unit 112, and the analysis unit 113. The shooting control unit 111 sends shooting request signals to the first shooting unit 130 to the fifth shooting unit 170 and receives image data generated by each shooting unit. In addition, the shooting control unit 111 transfers the received image data according to the request of the analysis unit 113.

[0036] The acquisition unit 112 acquires path information corresponding to the installation body 300 to be inspected from the storage unit 121. When the storage unit 121 is connected to a network, the information is acquired via the input / output device 123. The analysis unit 113 will be described in detail later. For example, by comparing the first image output by the first imaging unit 130 with the second image output by the second imaging unit 140, a three-dimensional analysis is performed on the wiring paths of each of the bonding leads 310 belonging to the first group 311. When a specific bonding lead 310 is designated as the inspection target, only the wiring path of that bonding lead 310 can be analyzed.

[0037] Next, the analysis method for the bonding lead 310 based on the analysis unit 113 will be explained using several figures. Figure 5 is an explanatory diagram illustrating the first captured image output by the first imaging unit 130 and the second captured image output by the second imaging unit 140. Furthermore, in the following explanation, the numbers marked on the entity will be used directly for the images of the mount 300 captured in each captured image.

[0038] Since the first captured image is an image obtained by the first capturing unit 130 from a top view of the mounting body 300 from the positive X-axis direction towards the negative X-axis direction, the portion closer to the positive X-axis becomes the lower side of the image, and the portion closer to the negative X-axis becomes the upper side of the image. If the mounting body 300 is captured in this way, the connecting leads 310 arranged on the first side 311a on the positive Y-axis in the first group 311 are located on the right side of the image, and the connecting leads 310 arranged on the second side 311b on the negative Y-axis are located on the left side of the image. In addition, in this embodiment, a telecentric optical system is used on the object side, so it is not affected by perspective, and the connecting leads 310 captured on the lower side and the connecting leads 310 captured on the upper side are the same size. Hereinafter, focusing on the connecting leads 310 arranged on the first side 311a, the third R3 lead from the top in the first captured image will be explained.

[0039] Since the second captured image is an image obtained by the second capturing unit 140 from a downward view of the mounting body 300 from the negative X-axis direction toward the positive X-axis direction, the portion closer to the negative X-axis becomes the lower side of the image, and the portion closer to the positive X-axis becomes the upper side of the image. If the mounting body 300 is captured in this way, the connecting leads 310 arranged on the first side 311a on the positive Y-axis in the first group 311 are located on the left side of the image, and the connecting leads 310 arranged on the second side 311b on the negative Y-axis are located on the right side of the image. In the mounted body 300 captured in this way, as shown, the R3 lead is the third one from below the first side 311a captured from the left. Furthermore, the situation where perspective does not affect the image is the same as in the first captured image.

[0040] Here, the second captured image is rotated 180°. If so, since the bonding lead 310 of the first side 311a is located on the right, the third bonding lead 310 from the top corresponds to the R3 lead, just as it does in the first captured image. However, due to the difference in viewing directions between the first capturing unit 130 and the second capturing unit 140 relative to the mounting body 300, i.e., parallax, the path of the R3 lead captured in the first captured image is different from the path of the R3 lead captured in the second captured image. In this embodiment, the three-dimensional bonding path of the R3 lead is calculated by detecting this difference in path.

[0041] In order to detect the path of the R3 lead on the first captured image and the path of the R3 lead on the second captured image, the analysis unit 113 uses the reference path contained in the path information 122. Figure 6 is an explanatory diagram illustrating the data structure of the path information 122 and the concept of the reference path.

[0042] For each mount that can be inspected, path information 122 is prepared in advance. Each path information 122 includes a mount number that distinguishes the mount, a substrate number indicating the model of the substrate constituting the mount, and a semiconductor wafer number indicating the model of the semiconductor wafer. The path information 122 further includes lead numbers corresponding to multiple bonding leads that connect the substrate and the semiconductor wafer, and for each lead number, a reference path is described as the connection path in the design of the bonding lead. The reference path is represented as multiple spatial coordinate values ​​through which the connection path passes in the design.

[0043] In the example shown in the figure, lead number R3 includes four spatial coordinate values ​​as its reference path. Specifically, it includes PS (xs, ys, zs) as an endpoint connected to wafer electrode 331, PE (xe, ye, ze) as an endpoint connected to substrate electrode 321, and PM1 (x1, y1, z1) and PM2 (x2, y2, z2) as two intermediate points. The reference path of lead R3, as described in this way, can be represented by multiple line segments connecting adjacent spatial coordinates, as shown on the right side of the figure. Increasing the number of intermediate points can more smoothly represent the reference path, but the number should be determined based on the balance between the accuracy and speed of the processing described later.

[0044] FIG7 is an explanatory diagram illustrating a method for detecting the center line of the R3 lead in the bonding lead 310 captured in the first captured image. In each of FIG7(a) to FIG7(e), the R3 lead captured in the first image is extracted and shown.

[0045] Figure 7(a) is a diagram showing the projection reference path 401 superimposed on the image of the R3 lead. The projection reference path 401 is a collection of line segments that connect nodes 410 in sequence. The nodes 410 are two-dimensional coordinates obtained by projectively transforming the spatial coordinate values ​​described in the reference path illustrated in Figure 6 based on the overhead view of the first imaging unit 130. More specifically, the angle between the optical axis of the first optical system 132 and the substrate surface 320a is used as the downward angle to project the spatial coordinate values ​​described in the reference path onto the XY plane, and the coordinate values ​​of the projected plane coordinates are converted according to the image magnification of the first optical system 132 to become the coordinate values ​​of the nodes 410. Therefore, the projection reference path 401 is equivalent to the image captured in the first captured image when the first imaging unit 130 imaginarily captures the reference path.

[0046] The actual R3 lead wires connected using the lead wire connector may not necessarily follow the designed spatial path. If they follow a spatial path that deviates from the reference, they should be evaluated as poor connections. Therefore, firstly, the center line of the R3 lead wires captured in the first image is inspected.

[0047] Figure 7(b) shows the following situation: relative to the projective reference path 401, the line segments between adjacent nodes 410 are divided into n equal parts (n is a natural number; in the example of the figure, n=3), and edge search lines 411 orthogonal to the line segments are drawn at each division point. Edge search lines 411 are auxiliary lines used to search for the boundary, i.e., the edge, between the image and the background of the R3 lead.

[0048] Figure 7(c) shows the following situation: when searching for an edge along the edge search line 411, the intersection point with the edge, i.e., the edge intersection point 412, is extracted. Specifically, the analysis unit 113 extracts the edge intersection point 412 by image processing using an edge filter.

[0049] Figure 7(d) shows the inner contour line 413 formed by sequentially connecting the edge intersections 412 extracted inside the projective reference path 401 using Bezier curves, and the outer contour line 414 formed by sequentially connecting the edge intersections 412 extracted outside the projective reference path 401 using Bezier curves. Here, the edge intersections 412 are smoothly connected by Bezier curves, but adjacent edge intersections 412 can also be connected and associated using line segments.

[0050] Figure 7(e) shows a first center line 415, calculated as the midline between the inner contour line 413 and the outer contour line 414, representing the path of the actual R3 lead captured in the first image. The analysis unit 113 determines the first center line 415 thus detected as the detection path of the R3 lead in the first image. The analysis unit 113 can also calculate a center line (designated as the second center line) based on the R3 lead captured in the second image according to the same procedure, and determine this center line as the detection path of the R3 lead in the second image.

[0051] FIG8 is an explanatory diagram illustrating a method for analyzing the spatial path of the actual bonding leads based on the detected center lines. The left side of FIG8(a) is an enlarged view of the area around the R3 lead captured in the first image, and the first center line 415, which serves as the detection path of the detected R3 lead, is shown overlaid. In addition, multiple auxiliary lines, namely detection parallel lines 330b, parallel to the edge line 330a of the semiconductor wafer 330 detected by image processing, are shown overlaid. Furthermore, the leftmost detection parallel line 330b is configured to pass through the first reference endpoint 415a, which serves as one end of the first center line 415. The right side of FIG8(a) is an enlarged view of the area around the R3 lead captured in the second image, and the second center line 416, which serves as the detection path of the detected R3 lead, is shown overlaid. In addition, multiple auxiliary lines, namely detection parallel lines 330b, parallel to the edge line 330a of the semiconductor wafer 330 detected by image processing, are shown overlaid. Furthermore, the detection parallel line 330b located on the far left is configured to pass through the second reference endpoint 416a, which serves as one end of the second center line 416.

[0052] The first reference endpoint 415a in the first captured image and the second reference endpoint 416a in the second captured image can both be understood as points corresponding to the same observation point (let's call it point A) connected to the wafer electrode 331 in the R3 lead. Therefore, the first reference endpoint 415a and the second reference endpoint 416a are set as reference points without parallax, and the height at these reference points is set as the reference height.

[0053] Figure 8(b) is a composite image of the first center line 415 and the second center line 416 based on this idea, wherein the first reference endpoint 415a and the second reference endpoint 416a overlap, and the corresponding detection parallel lines 330b overlap with each other. As shown in the figure, the coordinate system on the composite image corresponds to the XY direction in the spatial coordinate system, the x-axis is determined downwards and the y-axis is determined to the right. At this time, the y coordinates of each detection parallel line 330b are set as ya, yb, ... yj in sequence.

[0054] For example, if focusing on the detection parallel line 330b of y=yb, the intersection point with the first center line 415 is (xd1, yd), and the intersection point with the second center line 416 is (xd2, yd). As described above, since the first imaging unit 130 and the second imaging unit 140 are symmetrically arranged with respect to the YZ plane, no parallax is generated in the Y-axis direction when observing the same observation point. Therefore, even in the first and second images, the image of the same observation point will not be shifted in the Y-axis direction. In other words, points with the same y-coordinate in both the first center line 415 and the second center line 416 can be considered to be identical points. That is, the intersection point (xd1, yd) with the first center line 415 and the intersection point (xd2, yd) with the second center line 416 are the same point on the R3 lead line (let's call it point D).

[0055] At this time, the difference in x-coordinates, xd2-xd1, between the intersection point (xd1, yd) with the first center line 415 and the intersection point (xd2, yd) with the second center line 416, is proportional to the height of point D. Furthermore, since the actual height of each unit difference coordinate in the composite image can be predetermined, the difference in x-coordinates can be converted into the actual height. That is, the height of point D (Z-coordinate) relative to the reference height can be calculated.

[0056] Furthermore, when the intersection of the detection parallel line 330b of y=yd and the reference height is set as (xd0, yd), if xd0-xd1=xd2-xd0, then the X coordinates of point D are the same as those of point A. However, if xd0-xd1≠xd2-xd0, then the X coordinates of point D are different from those of point A. Furthermore, (xd0-xd1)-(xd2-xd0) is proportional to the offset of the X coordinates of point D relative to the X coordinates of point A. Here, since the actual difference in X coordinates per unit difference coordinate in the synthesized image can be predetermined, (xd0-xd1)-(xd2-xd0) can be converted into the actual difference in X coordinates. That is, by adding the X coordinate differences converted to the X coordinates of point A, the X coordinates of point D can be calculated.

[0057] Next, focusing on the detection parallel line 330b of y=yj, the intersection point with the first center line 415 is (xj1, yd), and the intersection point with the second center line 416 is (xj2, yd). As mentioned above, these intersection points are the same point on the R3 lead line (let's call it point J). Regarding point J, the Z and X coordinates can be calculated in the same way as for point D. Here, at point D, xd2-xd1>0, so it can be known that the Z coordinate of point D is greater than the Z coordinate of point A, that is, the height of point D is higher than the height of point A. However, at point J, xj2-xj1<0, so it can be known that the Z coordinate of point J is less than the Z coordinate of point A, that is, the height of point J is lower than the height of point A.

[0058] Thus, if the same calculation is repeatedly performed in the detection parallel lines 330b of y=yb, ... y=yj, as shown in Figure 8(c), the spatial coordinates Pa=(Xa, Ya, Za), the spatial coordinates Pb of point B, the spatial coordinates Pc of point C, ... the spatial coordinates Pj of point J can be calculated sequentially. Then, if adjacent points are connected by line segments, a detection result of the spatial path that can be evaluated as an actual R3 lead can be obtained. Then, the analysis unit 113 can compare the spatial path obtained as such a detection result with the reference path contained in the path information. For example, if the deviation between the two is within the reference range, it is evaluated as an appropriate knot; if it exceeds the reference range, it is evaluated as a poor knot.

[0059] The analysis unit 113 can confirm whether there is any inconsistency between the image of the R3 lead extracted from the fifth captured image output from the fifth imaging unit 170 and the spatial path obtained as a detection result. For example, by projecting the spatial path obtained as a detection result onto the XY plane, and evaluating the degree of consistency between the projected plane coordinate values ​​on the fifth captured image after magnification conversion based on the image magnification of the fifth optical system 172 and the center line extracted from the image of the R3 lead on the fifth captured image, the reliability of the spatial path obtained as a detection result can be confirmed. In the case of low consistency, for example, the analysis unit 113 only needs to recalculate the spatial path again.

[0060] The analysis unit 113 uses the first and second captured images to analyze the spatial paths of all bonding leads 310 belonging to the first group 311 as described above. Additionally, it uses the third and fourth captured images to analyze the spatial paths of all bonding leads 310 belonging to the second group 312 in the same manner as described above.

[0061] Next, a series of inspection procedures based on the inspection device 100 will be organized. Figure 9 is a flowchart showing the inspection procedure of the mounting body 300. The procedure begins from the state where the mounting body 300, which is the object of observation, is placed on the stage 190.

[0062] In step S101, the imaging control unit 111 sends an imaging request signal to the first imaging unit 130. When the first imaging unit 130 receives the imaging request signal, it takes an image of the entire mounting body 300, including the bonding lead 310 which is the object of inspection, and generates image data. The imaging control unit 111 receives the image data generated by the first imaging unit 130 and transfers it to the analysis unit 113 as the image data of the first captured image.

[0063] In step S102, the imaging control unit 111 sends an imaging request signal to the second imaging unit 140. When the second imaging unit 140 receives the imaging request signal, it takes an image of the entire mounting body 300, including the bonding lead 310 which is the object of inspection, and generates image data. The imaging control unit 111 receives the image data generated by the second imaging unit 140 and transfers it to the analysis unit 113 as the image data of the second captured image. Furthermore, the processing in step S101 and the processing in step S102 can be in reverse order or in parallel.

[0064] In step S103, the analysis unit 113 uses the first captured image and the second captured image as described above to detect the spatial paths of the bonding leads 310 belonging to the first group 311. Then, each detected spatial path is compared with the corresponding reference path to perform analysis, such as whether it is an appropriate bonding lead.

[0065] In step S104, the imaging control unit 111 sends an imaging request signal to the third imaging unit 150. When the third imaging unit 150 receives the imaging request signal, it takes an image of the entire mounting body 300, including the bonding lead 310 which is the object of inspection, and generates image data. The imaging control unit 111 receives the image data generated by the third imaging unit 150 and transfers it to the analysis unit 113 as the image data of the third imaging image.

[0066] In step S105, the imaging control unit 111 sends an imaging request signal to the fourth imaging unit 160. When the fourth imaging unit 160 receives the imaging request signal, it takes an image of the entire mounting body 300, including the bonding lead 310 which is the object of inspection, and generates image data. The imaging control unit 111 receives the image data generated by the fourth imaging unit 160 and transfers it to the analysis unit 113 as the image data of the fourth imaging image. Furthermore, the processing in step S104 and the processing in step S105 can be in reverse order or in parallel.

[0067] In step S106, the analysis unit 113 uses the third and fourth captured images as described above to detect the spatial paths of the bonding leads 310 belonging to the second group 312. Then, each detected spatial path is compared with the corresponding reference path to perform analysis, such as whether it is an appropriate bonding lead. Furthermore, the processing in steps S101 to S103 and the processing in steps S104 to S106 can be performed in reverse order or in parallel.

[0068] In step S108, the imaging control unit 111 sends an imaging request signal to the fifth imaging unit 170. When the fifth imaging unit 170 receives the imaging request signal, it takes an image of the entire mounting body 300, including the bonding lead 310 which is the object of inspection, and generates image data. The imaging control unit 111 receives the image data generated by the fifth imaging unit 170 and transfers it to the analysis unit 113 as the image data of the fifth imaging image.

[0069] In step S108, the analysis unit 113 extracts the center lines of each of the bonding leads 310 captured in the fifth image and calculates the consistency with the spatial paths of each bonding lead 310 obtained in steps S103 and S107. If the consistency is within a specified range, it is evaluated as a normal analysis result, and the analysis result is displayed on a display monitor, which is one of the input / output devices 123. If the consistency exceeds the specified range, error handling, such as repeating a series of processes, can be performed. After the evaluation of the analysis result obtained by the analysis unit 113 is completed, the arithmetic processing unit 110 ends the series of processes. Alternatively, the arithmetic processing unit 110 may omit the processes in steps S107 and S108, display the analysis result obtained by the analysis unit 113 on the display monitor, and end the series of processes.

[0070] Next, the application method for performing higher-precision analysis of the bonding leads 310 will be described. FIG10 is an explanatory diagram illustrating one of this application methods. Specifically, FIG10 is a diagram corresponding to FIG2, showing the case where the semiconductor wafer 330 is rotated θ° relative to the substrate 320 about the Z-axis and fixed. That is, it shows the case where the relative posture of the substrate 320 and the semiconductor wafer 330 is offset from the intended posture. Even if the semiconductor wafer 330 is offset about the Z-axis and fixed as described above, the wire bonder detects the substrate electrode 321 and the wafer electrode 331 to be wired and then bonds the bonding leads 310, so the wiring process can be completed smoothly. However, due to the rotational offset of the semiconductor wafer 330, there may be cases where adjacent bonding leads 310 come into contact with each other. Therefore, the inspection device 100 takes into account the rotational offset of the semiconductor wafer 330 and performs three-dimensional analysis of the wiring path.

[0071] Specifically, the analysis unit 113 extracts the reference mark 322 and the edge line 330a of the semiconductor wafer 330 from the fifth captured image, and calculates the rotation center coordinates and rotation amount of the semiconductor wafer 330 relative to the substrate 320 about the Z-axis. Then, it reads the path information 122 of the bonding lead 310 (e.g., R3 lead) that is being detected, and performs an affine transformation on each of the spatial coordinates of the reference path using the calculated rotation center coordinates and rotation amount. Then, the processing of performing the projective transformation and applying it to the first captured image and the second captured image is as described using FIG7.

[0072] The analysis unit 113 analyzes, for example, whether the spatial paths of each bonding lead 310 calculated in this way are separated from the reference path beyond the allowable range. In addition, the diameter of the bonding lead 310 can also be considered to analyze whether the calculated spatial paths of the bonding leads 310 are in contact with the spatial paths of adjacent bonding leads 310.

[0073] The inspection device 100, as an example of an inspection device, has been described above. However, various modifications can be made to the device structure or processing method of the inspection device in this embodiment. For example, regarding the aperture of each shooting unit set to meet the Cyclone conditions, it is conceivable that the fixed aperture is selected such that the ring height HW corresponding to the connecting lead 310 as the object of observation is included in the depth of field DP. However, if the shooting unit uses a variable aperture, the size of the aperture opening can also be adjusted according to the mounting body as the object of observation. For example, for a mounting body with a high ring height HW, the aperture opening is reduced to increase the depth of field DP; conversely, for a mounting body with a low ring height HW, the aperture opening is increased to decrease the depth of field DP. In this case, when the aperture opening is reduced, the illumination light illuminating the mounting body is strengthened; conversely, when the aperture opening is increased, the illumination light illuminating the mounting body is weakened.

[0074] Furthermore, in the inspection device 100, a first captured image and a second captured image are used to detect the spatial paths of each of the plurality of bonding leads 310 belonging to the first group 311. However, for example, the spatial path of a specific bonding lead 310 can also be detected based on a first captured image and a second captured image. Thus, if the acquired first captured image and second captured image are used to detect the spatial path of a bonding lead 310, the requirements of the optical system can be mitigated, for example.

[0075] Furthermore, in the inspection device 100, the paired first and second imaging units are configured as imaging units that satisfy the Cyinflux condition, but one of them can also be configured as a general imaging unit with the imaging surface parallel to the focal plane. Even with the combination of imaging units that satisfy the Cyinflux condition and general imaging units, as long as the mounting body 300 is viewed from different directions, the two images obtained by each imaging unit become parallax images, thus the spatial path of the bonding lead 310 can also be detected.

[0076] Furthermore, it has been described that in the inspection apparatus 100, one end of each bonding lead 310 is connected to the substrate 320, and the other end is connected to the semiconductor wafer 330. However, the inspection apparatus can also inspect bonding leads formed on the semiconductor wafer in an open manner, such as with one end in a pin shape. In addition, it is not limited to an inspection apparatus for inspecting bonding leads that are connected to the substrate and the semiconductor wafer, but can also be an inspection apparatus for inspecting bonding leads that are connected to the substrate and other components, or that are connected to the substrate in an open manner. [Simplified Explanation of the Diagram]

[0010] Figure 1 is a perspective view schematically showing the main parts of the inspection apparatus of this embodiment. Figure 2 is a perspective view schematically showing the mounting body as the object of inspection. Figure 3 is an explanatory diagram illustrating the Cyinflux optical system and its depth of field. Figure 4 is a system structure diagram of the inspection apparatus. Figure 5 is an explanatory diagram illustrating the captured image output by the imaging unit. Figure 6 is an explanatory diagram illustrating the data construction of path information and the concept of a reference path. Figure 7 is an explanatory diagram illustrating a method for detecting the centerline of the bonding lead. Figure 8 is an explanatory diagram illustrating a method for analyzing the spatial path of the actual bonding lead based on the centerlines of the detected image. Figure 9 is a flowchart showing the inspection procedure of the mounting body. Figure 10 is an explanatory diagram illustrating a method for performing higher precision analysis.

Claims

1. An inspection apparatus for inspecting bonding leads that connect between a substrate and a semiconductor wafer, the inspection apparatus comprising: A first imaging unit is used to capture an overhead view of the semiconductor wafer, wherein the optical system and imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface of the substrate becomes the focal plane, and the first imaging unit has an aperture adjusted such that the ring height of the bonding wire being inspected converges to the depth of field; a second imaging unit is used to capture an overhead view of the semiconductor wafer from a direction different from the overhead view of the first imaging unit; and an analysis unit performs three-dimensional analysis of the bonding wire connection path by comparing a first image output by the first imaging unit with a second image output by the second imaging unit, wherein the second imaging unit is disposed on the side opposite to the first imaging unit relative to the semiconductor wafer, wherein the optical system and imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface becomes the focal plane, and the second imaging unit has an aperture adjusted such that the ring height converges to the depth of field.

2. The inspection apparatus as described in claim 1, comprising: A third imaging unit is used to view and photograph the semiconductor wafer from a direction orthogonal to the first imaging unit, wherein the optical system and imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface becomes the focal plane, and the third imaging unit has an aperture that is adjusted such that the ring height converges to the depth of field; and a fourth imaging unit is used to view and photograph the semiconductor wafer from a side opposite to the third imaging unit relative to the semiconductor wafer, wherein the optical system and imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface becomes the focal plane, and the fourth imaging unit has an aperture that is adjusted such that the ring height converges to the depth of field; The analysis unit compares the first image output by the first imaging unit with the second image output by the second imaging unit, and performs three-dimensional analysis on the bonding leads that extend from the side edge of the semiconductor wafer along the first side of the straight line connecting the positions of the first and second imaging units and toward the substrate, respectively, as inspection objects. Similarly, it compares the third image output by the third imaging unit with the fourth image output by the fourth imaging unit, and performs three-dimensional analysis on the bonding leads that extend from the side edge of the semiconductor wafer along the third side orthogonal to the first side and the fourth side opposite to the third side and toward the substrate, respectively, as inspection objects.

3. The inspection apparatus as claimed in claim 1, comprising a fifth imaging unit for taking a top-view image of the semiconductor wafer, wherein the analysis unit uses the fifth image output by the fifth imaging unit to evaluate the analyzed junction path.

4. The inspection apparatus as claimed in claim 1, wherein, The analysis unit performs a three-dimensional analysis of the connection paths of each of the multiple bonding leads that are the objects of inspection, based on a first captured image and a second captured image.

5. The inspection apparatus as claimed in claim 1, wherein, The first imaging unit employs a telecentric optical system at least on the object side.

6. The inspection apparatus as claimed in claim 1, wherein, The analysis unit searches for the connection path of the bonding wire that is the object of inspection in each of the first and second captured images, referring to a pre-set reference path.

7. The inspection apparatus as claimed in claim 6, wherein, The analysis unit detects the relative posture of the substrate and the semiconductor wafer, and searches for the junction path by referring to the reference path corrected based on the posture.

8. The inspection apparatus as claimed in claim 1, wherein, The analysis unit analyzes the connection path of the bonding lead by calculating the intersection point of the imaginary line generated parallel to the side edge of the semiconductor wafer captured in the first and second captured images and the bonding lead being inspected.

9. An inspection method for inspecting bonding leads that connect between a substrate and a semiconductor wafer, the inspection method comprising: a first imaging step of taking an overhead photograph of the semiconductor wafer to be inspected using a first imaging unit, wherein the first imaging unit is configured such that a plane parallel to the surface of the substrate is a focal plane satisfying the Cyinfluence condition, and the first imaging unit has an aperture adjusted such that the loop height of the bonding lead to be inspected converges to the depth of field; a second imaging step of taking an overhead photograph of the semiconductor wafer from a direction different from the overhead direction of the first imaging unit using a second imaging unit; and an analysis step of performing a three-dimensional analysis of the bonding lead connection path by comparing a first image output by the first imaging unit with a second image output by the second imaging unit, wherein... The second imaging unit is disposed on the opposite side of the first imaging unit relative to the semiconductor wafer, wherein the optical system and the imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface becomes the focal plane, and the second imaging unit has an aperture that is adjusted such that the ring height converges to the depth of field.

10. An inspection program for inspecting bonding leads connecting a substrate and a semiconductor wafer, the inspection program causing a computer to perform the following steps: a first imaging step, using a first imaging unit to take an overhead photograph of the semiconductor wafer to be inspected, wherein the first imaging unit has an optical system and an imaging element configured such that a plane parallel to the surface of the substrate becomes the focal plane to satisfy the Cyinfluence condition, and the first imaging unit has an aperture adjusted such that the loop height of the bonding lead to be inspected converges to the depth of field; a second imaging step, using a second imaging unit to take an overhead photograph of the semiconductor wafer from a direction different from the overhead direction of the first imaging unit; and an analysis step, performing a three-dimensional analysis of the bonding lead's connection path by comparing a first image output by the first imaging unit with a second image output by the second imaging unit, wherein... The second imaging unit is disposed on the opposite side of the first imaging unit relative to the semiconductor wafer, wherein the optical system and the imaging element are configured to satisfy the Cyinfluence condition such that a plane parallel to the surface becomes the focal plane, and the second imaging unit has an aperture that is adjusted such that the ring height converges to the depth of field.

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