Inspection device, inspection method, and inspection program

Abstract

To provide an inspection device and the like capable of three-dimensionally analyzing a wiring path in a short time with a small number of images, even if a bonding wire is fine and intricately connected.SOLUTION: An inspection device for a bonding wire connected between a substrate and a semiconductor chip, the inspection device comprising: a first imaging unit for capturing an overhead image of the bonding wire; a second imaging unit for capturing an overhead image of the bonding wire from a direction different from the overhead direction of the first imaging unit; an acquisition section for acquiring path information relating to a preset reference path of the bonding wire; and an analysis section for analyzing a spatial path of the bonding wire by defining and comparing, on the basis of the path information acquired by the acquisition section, the bonding wire appearing in a first captured image output by the first imaging unit and the bonding wire appearing in a second captured image output by the second imaging unit.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an inspection device, an inspection method, and an inspection program. [Background technology]

[0002] There are known devices that inspect whether bonding wires are properly connected to a mounting assembly in which substrate electrodes on a substrate and chip electrodes of a semiconductor chip fixed on the substrate are connected by bonding wires. For example, according to the technology disclosed in Patent Document 1, an optical system with a shallow depth of field is used to capture images of the bonding wire multiple times while changing the focal height, and the XY coordinates of the wire at each focal height are detected to obtain three-dimensional information about the entire bonding wire. Furthermore, according to the technology disclosed in Patent Document 2, which employs a different method, a lattice pattern is projected onto the bonding wire, which is then imaged with two or more imaging units, and three-dimensional information about the bonding wire is calculated from the amount of deviation between corresponding lattice 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 [Problem to be solved by the invention]

[0004] The technology of Patent Document 1 requires imaging the object to be observed multiple times while moving the focal height, which takes a lot of time. Furthermore, since imaging must be performed from directly above, there is a restriction that no intersections must occur when observing the bonding wire from the height direction. The technology of Patent Document 2 requires projecting grid points onto the surface of a thin bonding wire, which requires fine grid patterns and makes it difficult to identify corresponding grids between images.

[0005] The present invention has been made to solve such problems, and provides an inspection device etc. that can analyze the wiring path of even thin and intricately connected bonding wires in three dimensions in a short time using a small number of images. [Means for solving the problem]

[0006] An inspection device in a first aspect of the present invention is an inspection device for a bonding wire connected between a substrate and a semiconductor chip, and is equipped with a first imaging unit for capturing an image of the bonding wire from a bird's-eye view, a second imaging unit for capturing an image of the bonding wire from a direction different from the bird's-eye view direction of the first imaging unit, an acquisition unit for acquiring path information regarding a predetermined reference path of the bonding wire, and an analysis unit for analyzing the spatial path of the bonding wire by defining and comparing the bonding wire shown in the first image output by the first imaging unit and the bonding wire shown in the second image output by the second imaging unit based on the path information acquired by the acquisition unit.

[0007] In addition, an inspection method in a second aspect of the present invention is a method for inspecting a bonding wire connected between a substrate and a semiconductor chip, and includes a first imaging step of imaging the bonding wire to be inspected from above using a first imaging unit, a second imaging step of imaging the bonding wire from above using a second imaging unit from a direction different from the above-mentioned direction of the first imaging unit, an acquisition step of acquiring path information regarding a predetermined reference path of the bonding wire, and an analysis step of analyzing the spatial path of the bonding wire by defining and comparing the bonding wire shown in the first image output by the first imaging unit in the first imaging step with the bonding wire shown in the second image output by the second imaging unit in the second imaging step based on the path information acquired in the acquisition step.

[0008] In addition, an inspection program in a third aspect of the present invention is an inspection program for a bonding wire connected between a substrate and a semiconductor chip, and causes a computer to execute a first imaging step of imaging the bonding wire to be inspected from above using a first imaging unit, a second imaging step of imaging the bonding wire from above using a second imaging unit from a direction different from the above-mentioned direction of the first imaging unit, an acquisition step of acquiring path information regarding a predetermined reference path of the bonding wire, and an analysis step of analyzing the spatial path of the bonding wire by defining and comparing the bonding wire shown in the first image output by the first imaging unit in the first imaging step with the bonding wire shown in the second image output by the second imaging unit in the second imaging step based on the path information acquired in the acquisition step. [Effects of the Invention]

[0009] The present invention can provide an inspection device or the like that can three-dimensionally analyze the connection path of even thin, complexly connected bonding wires in a short time using a small number of images. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically showing a main part of an inspection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view schematically showing a mounting assembly to be inspected; [Figure 3] FIG. 1 is an explanatory diagram illustrating a Scheimpflug optical system and its depth of field. [Figure 4] FIG. 1 is a system configuration diagram of an inspection device. [Figure 5] FIG. 2 is an explanatory diagram illustrating a captured image output by an imaging unit. [Figure 6] FIG. 2 is an explanatory diagram illustrating the data structure of route information and the concept of a reference route. [Figure 7] FIG. 10 is an explanatory diagram illustrating a method for detecting the center line of a bonding wire. [Figure 8]10 is an explanatory diagram illustrating a method for analyzing the spatial path of an actual bonding wire from each center line of a detected image. FIG. [Figure 9] FIG. 10 is a flow chart illustrating an inspection procedure for a mounting assembly. [Figure 10] FIG. 10 is an explanatory diagram illustrating a method for performing a more highly accurate analysis. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below through embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential means for solving the problems. In each drawing, components with the same reference numerals have the same or similar configurations. Furthermore, when multiple structures with the same or similar configurations exist in each drawing, some may be referenced with the same reference numerals, and others may not be referenced with the same reference numerals, in order to avoid complication.

[0012] 1 is a perspective view that schematically shows the main parts of an inspection device 100 according to this embodiment. The inspection device 100 includes a stage 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, which are arranged in positions that overlook the stage 190. In the figure, each imaging unit is shown as floating in midair, but in reality, it is supported by a frame or the like.

[0013] The mounting body 300 placed on the stage 190 is the object of observation by the inspection device 100. The mounting body 300 is mainly composed of a substrate 320, a semiconductor chip 330 fixed on the substrate 320, and a plurality of bonding wires 310 electrically connecting the substrate 320 and the semiconductor chip 330. The mounting body 300 may be in a state before being singulated, with multiple mounting bodies 300 arranged in a planar direction. In this case, the stage 190 may be equipped with a movement mechanism that moves the mounted mounting bodies 300 in a planar direction so that the mounting bodies 300 to be observed are positioned at an observation position (e.g., the center) of the stage 190. Note that, although the substrate before being singulated, on which multiple mounting bodies 300 are arranged in a planar direction, is in the form of a single plate, in this embodiment, the portions corresponding to the individual mounting bodies 300 after singulation will be described as the substrate 320. The bonding wires 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 wires.

[0014] In the description of this embodiment, as shown in the figure, 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 that is perpendicular to the X-axis direction is defined as the Y-axis direction. In the following description, the XY directions may be referred to as planar directions. Furthermore, the direction perpendicular to the X-axis and Y-axis directions is defined as the Z-axis direction. In the following description, the Z-axis direction may be referred to as the height direction, and the positive direction of the Z-axis may be referred to as up, and the negative direction of the Z-axis may be referred to as down. Furthermore, in the following drawings, the orientation of the structure depicted in each drawing is indicated by adding similar coordinate axes based on the state in which the inspection device 100 is installed as shown in FIG. 1.

[0015] The first imaging unit 130 is disposed so as to overlook the mounting body 300 disposed on the stage 190 from the positive side of the X axis toward the negative direction of the X axis. The second imaging unit 140 is disposed so as to overlook the mounting body 300 disposed on the stage 190 from the negative side of the X axis toward the positive direction of the X axis. In other words, the first imaging unit 130 and the second imaging unit 140 are disposed on opposite sides of the semiconductor chip 330 located at the center of the mounting body 300 to be observed.

[0016] The first imaging unit 130 includes a first imaging element 131 and a first optical system 132. As will be described in more detail later, the first imaging element 131 and the first optical system 132 are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate 320 is their focal plane. Similarly, the second imaging unit 140 includes a second imaging element 141 and a second optical system 142. As will be described in more detail later, the second imaging element 141 and the second optical system 142 are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate 320 is their focal plane. The first imaging unit 130 and the second imaging unit 140 are each controlled by an imaging control unit, which will be described later, and capture images of the mounting body 300 in response to imaging instructions and transmit the generated image data to the imaging control unit.

[0017] The third imaging unit 150 is disposed so as to overlook the mounting body 300 disposed on the stage 190 from the positive side of the Y axis toward the negative direction of the Y axis. The fourth imaging unit 160 is disposed so as to overlook the mounting body 300 disposed on the stage 190 from the negative side of the Y axis toward the positive direction of the Y axis. In other words, the third imaging unit 150 and the fourth imaging unit 160 are disposed on opposite sides of the semiconductor chip 330 located at the center of the mounting body 300 to be observed.

[0018] The third imaging unit 150 includes a third imaging element 151 and a third optical system 152. As will be described in more detail below, the third imaging element 151 and the third optical system 152 are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate 320 is their focal plane. Similarly, the fourth imaging unit 160 includes a fourth imaging element 161 and a fourth optical system 162. As will be described in more detail below, the fourth imaging element 161 and the fourth optical system 162 are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate 320 is their focal plane. The third imaging unit 150 and the fourth imaging unit 160 are each controlled by an imaging control unit (described in more detail below), and capture images of the mounting body 300 in response to imaging instructions and transmit the generated image data to the imaging control unit.

[0019] The fifth imaging unit 170 is arranged so as to overlook the mounting body 300 arranged 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 arrangement of the fifth imaging element 171 and the fifth optical system 172 differs from the arrangement of the imaging elements and optical systems of the first imaging unit 130 to the fourth imaging unit 160, and is similar to the arrangement in a general imaging unit in which the imaging plane and focal plane are parallel. The fifth imaging units 170 are each controlled by an imaging control unit (described later), and capture images of the mounting body 300 in response to imaging instructions and transmit the generated image data to the imaging control unit.

[0020] 2 is a perspective view schematically showing a mounting assembly 300 to be inspected. As described above, the mounting assembly 300 to be inspected in this embodiment has a semiconductor chip 330 fixed on a substrate 320, which is electrically connected to each other by a plurality of bonding wires 310. More specifically, each bonding wire 310 connects a plurality of board electrodes 321 provided on the substrate 320 to a plurality of chip electrodes 331 provided on the semiconductor chip 330 in a one-to-one manner. The inspection device 100 analyzes the three-dimensional connection path that each bonding wire 310 follows to connect the board electrodes 321 and the chip electrodes 331.

[0021] In the mounting assembly 300 to be inspected in this embodiment, the substrate 320 and the semiconductor chip 330 each form a substantially square, and the semiconductor chip 330 is stacked on the substrate 320 so that their side edges are parallel. The multiple bonding wires 310 connecting the semiconductor chip 330 to the substrate 320 are divided into a first group 311 that are deployed from first and second sides that are parallel to each other along the X-axis direction among the four side edges of the semiconductor chip 330 toward the substrate 320, and a second group 312 that are deployed from third and fourth sides that are parallel to each other along the Y-axis direction toward the substrate 320. As will be described in detail later, the wiring paths of the bonding wires 310 in the first group 311 are analyzed mainly by comparing the first captured image output by the first imaging unit 130 with the second captured image output by the second imaging unit 140, and the wiring paths of the bonding wires 310 in the second group 312 are analyzed mainly by comparing the third captured image output by the third imaging unit 150 with the fourth captured image output by the fourth imaging unit 160.

[0022] Two cross-shaped reference marks 322, for example, are provided diagonally on the periphery of the substrate 320. In analyzing the wiring path, a coordinate system is defined using the images of these reference marks 322 as reference positions. Note that the reference marks 322 do not have to be indicators specifically provided on the substrate 320; for example, the pattern of a specific substrate electrode 321 may also be used as the reference mark 322.

[0023] 3 is an explanatory diagram illustrating the Scheimpflug optical system and its depth of field employed in the first imaging unit 130 to the fourth imaging unit 160. The only difference between the combination of the first imaging unit 130 and the second imaging unit 140 and the combination of the third imaging unit 150 and the fourth imaging unit 160 is whether they are installed along the X-axis direction or along the Y-axis direction, and therefore the combination of the first imaging unit 130 and the second imaging unit 140 will be described here as a representative example.

[0024] First, the arrangement conditions of the image sensor and the optical system in the Scheimpflug optical system will be described using the first imaging unit 130. In FIG. 3, plane S1 is a plane including the substrate surface 320a, which is the surface of the substrate 320, and is the intended focal plane. Virtual plane S2 is a plane including the principal plane of the first optical system 132, which is composed of the object-side lens group 132a and the image-side lens group 132b. Plane S3 is a plane including the light-receiving surface of the first image sensor 131. When the first image sensor 131 and the first optical system 132 are arranged to satisfy the Scheimpflug condition, as shown in the figure, plane S1, virtual plane S2, and plane S3 intersect with each other on a common line P1. In other words, the first image sensor 131 and the first optical system 132 arranged to satisfy the Scheimpflug condition can have a plane obliquely intersecting the light-receiving surface of the first image sensor 131 as the focal plane. Therefore, even if the first imaging unit 130 is installed at a position where it overlooks the mounting assembly 300 from an oblique direction, it can use the board surface 320a as its focal plane.

[0025] The aperture 133 is disposed between the object-side lens group 132a and the image-side lens group 132b, and limits the light beam that passes through. In particular, in the inspection apparatus 100 of this embodiment, the diameter of the aperture 133 is adjusted to adjust the depth of field D P is adjusted to a certain range. Specifically, the depth of field D P is the maximum height of the bonding wires 310 belonging to the first group 311, i.e., the loop height H W The loop height H W is a value that is greater than the height when the bonding wire 310 is connected according to the design value, and is set to, for example, a value that is 110% or more and less than 130%. If set in this way, even if the bonding wire 310 is actually connected with a deviation in the height direction of less than 30% from the design value, it is possible to capture an image of the entire bonding wire 310 in a focused state, and the connection path can be properly detected as described below. Note that in the figure, the depth of field D P is shown as a line parallel to the plane S1, which is the intended focal plane, but the actual depth of field D PIn the Scheimpflug optical system, the depth of field D is narrow on the side of the line P1 and widens as it moves away from the line P1. In this embodiment, the depth of field D is narrowest in the imaging range for imaging the mounting body 300. P may be adjusted as described above.

[0026] In the illustrated example, the plane S1, which is the intended focal plane, is a plane including the substrate surface 320a. P is the loop height H W As long as the loop height H W Alternatively, the plane S1 may be set to coincide with a plane that bisects the first and second imaging units 130 and 140. The stage 190 may be moved up and down relative to the first and second imaging units 130 and 140 so that such an inclusive relationship is realized.

[0027] In this embodiment, telecentricity on the object side is achieved by the object-side lens group 132a. As a result, on the obliquely intersecting focal planes, whether the subject is located on the near side (positive side of the X axis) or the far side (negative side of the X axis), as long as the subject is the same size, it can be imaged on the light-receiving surface of the first image sensor 131 at the same magnification. In other words, since perspective does not appear in the depth direction of the subject, there is no need to perform enlargement / reduction conversion according to the depth position of the subject depicted in the captured image, and three-dimensional analysis, which will be described later, can be easily performed.

[0028] The second imaging unit 140 has a configuration similar to that of the first imaging unit 130, and is installed symmetrically with the first imaging unit 130 with respect to the YZ plane so that the mounting body 300 can be imaged at the center of the angle of view. Specifically, the second imaging unit 140 includes a second imaging element 141 and a second optical system 142 having an object-side lens group 142a and an image-side lens group 142b as constituent groups, and the second imaging element 141 and the second optical system 142 are arranged to satisfy the Scheimpflug condition so that the plane S1 becomes the focal plane. The aperture 143 is arranged between the object-side lens group 142a and the image-side lens group 142b, and has a loop height H WDepth of field D P The diameter of the aperture 143 is adjusted so that the above is realized.

[0029] In addition, the loop height H W The depth of field D of the first imaging unit 130 is P and the depth of field D of the second imaging unit 140 P may be different. Similarly, the depth of field D P Loop H W As long as the above is included, the focal plane of the first imaging unit 130 and the focal plane of the second imaging unit 140 do not have to be on the same plane.

[0030] Furthermore, as described above, the third imaging unit 150 and the fourth imaging unit 160 are provided to capture images of the bonding wires 310 belonging to the second group 312. However, if the stage 190 is rotatable around the Z axis, for example, the first imaging unit 130 and the second imaging unit 140 can capture images of the bonding wires 310 of the second group 312 from orthogonal directions, so the installation of the third imaging unit 150 and the fourth imaging unit 160 may be omitted.

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

[0032] The arithmetic processing unit 110 is a processor (CPU: Central Processing Unit) that controls the inspection device 100 and executes programs. The processor may be configured to work in conjunction with an arithmetic processing chip such as an ASIC (Application Specific Integrated Circuit) or a GPU (Graphics Processing Unit). The arithmetic processing unit 110 reads out the inspection program stored in the storage unit 121 and executes various processes related to the inspection of the bonding wire 310.

[0033] The storage unit 121 is a non-volatile storage medium and is configured, for example, by an HDD (Hard Disk Drive). The storage unit 121 can store various parameter values, functions, lookup tables, and the like used for control and calculation, in addition to programs for controlling and executing processes of the inspection apparatus 100. The storage unit 121 particularly stores path information 122. The path information 122, which will be described in detail later, includes information on the substrate 320 and the semiconductor chip 330, and information on reference paths described based on the design values ​​of the bonding wires 310 connecting them. Note that a portion of the storage unit 121 may be connected via a network.

[0034] The input / output device 123 includes, for example, a keyboard, a mouse, a display monitor, and a network interface, and is a device that accepts menu operations by a user and presents information to the user. For example, the arithmetic processing unit 110 may display images captured by each imaging unit on a display monitor that is one of the input / output devices 123. When the storage unit 121 is connected to a network, the arithmetic processing unit 110 obtains necessary information, programs, etc. from the storage unit 121 via a network interface that is one of the input / output devices 123.

[0035] The arithmetic processing unit 110 also serves as a functional calculation unit that executes various calculations in accordance with the processing instructed by the inspection program. The arithmetic processing unit 110 can function as an imaging control unit 111, an acquisition unit 112, and an analysis unit 113. The imaging control unit 111 transmits imaging request signals to the first imaging unit 130 to the fifth imaging unit 170, and receives image data captured and generated by each imaging unit. The imaging control unit 111 also hands over the received image data in response to a request from the analysis unit 113.

[0036] The acquisition unit 112 acquires path information corresponding to the mounting assembly 300 to be inspected from the storage unit 121. If the storage unit 121 is connected to a network, the acquisition is performed via the input / output device 123. The analysis unit 113, which will be described in detail later, performs a three-dimensional analysis of the connection paths of each of the bonding wires 310 belonging to the first group 311, for example, by comparing a first captured image output by the first imaging unit 130 with a second captured image output by the second imaging unit 140. If a specific bonding wire 310 is designated as the inspection target, it is possible to analyze only the connection path of that bonding wire 310.

[0037] Next, a method for analyzing the bonding wire 310 by the analysis unit 113 will be described with reference to several figures. Fig. 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. In the following description, the reference numerals assigned to the actual mounting body 300 appearing in each captured image will also be used as they are.

[0038] The first captured image is an image captured by the first imaging unit 130 looking down on the mounting body 300 from the positive side of the X-axis toward the negative side of the X-axis. Therefore, the portion of the mounting body 300 closer to the positive side of the X-axis is at the bottom of the image, and the portion closer to the negative side of the X-axis is at the top of the image. When the mounting body 300 is captured in this manner, the bonding wires 310 arranged on the first side 311a of the first group 311 on the positive side of the Y-axis are positioned on the right side of the image, and the bonding wires 310 arranged on the second side 311b on the negative side of the Y-axis are positioned on the left side of the image. Furthermore, since a telecentric optical system is employed on the object side in this embodiment, the bonding wires 310 appearing on the bottom and the top are the same size without being affected by perspective. The following description focuses on the R3 wire, which is the third wire from the top in the first captured image, among the bonding wires 310 arranged on the first side 311a.

[0039] The second captured image is an image captured by the second imaging unit 140 looking down on the mounting body 300 from the negative side of the X-axis toward the positive side of the X-axis. Therefore, the portion of the mounting body 300 closer to the negative side of the X-axis is at the bottom of the image, and the portion closer to the positive side of the X-axis is at the top of the image. When the mounting body 300 is captured in this manner, the bonding wires 310 arranged on the first side 311a on the positive side of the Y-axis in the first group 311 are positioned on the left side of the image, and the bonding wires 310 arranged on the second side 311b on the negative side of the Y-axis are positioned on the right side of the image. In the mounting body 300 captured in this manner, the R3 wire is positioned third from the bottom on the first side 311a, which is captured on the left side. Similarly to the first captured image, the image is not affected by perspective.

[0040] Here, the second captured image is rotated 180°. As a result, the bonding wire 310 on the first side 311a is positioned on the right side, and thus the third bonding wire 310 from the top corresponds to the R3 wire, similar to its position in the first captured image. However, due to the difference in the observation direction of the first imaging unit 130 and the second imaging unit 140 relative to the mounting assembly 300, i.e., due to parallax, the path of the R3 wire captured in the first captured image differs from the path of the R3 wire captured in the second captured image. In this embodiment, the three-dimensional wiring path of the R3 wire is calculated by detecting this difference in path.

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

[0042] Path information 122 is prepared in advance for each package that can be inspected. Each piece of path information 122 includes a package number that identifies the package, a board number that indicates the model number of the board that constitutes the package, and a semiconductor chip number that indicates the model number of the semiconductor chip. The path information 122 further includes wire numbers that correspond to each of a plurality of bonding wires that connect the board and the semiconductor chip, and for each wire number, a reference path is described as the design connection path of the bonding wire. The reference path is expressed as a plurality of spatial coordinate values ​​through which the design connection path passes.

[0043] In the illustrated example, wire number R3 includes four spatial coordinate values ​​as its reference path. Specifically, the end point PS(x s ,y s ,z s ), and PE(x e ,y e ,z e ), and two intermediate points PM1(x1,y1,z1) and PM2(x2,y2,z2). The reference path of the R3 wire described in this way can be expressed by multiple line segments connecting adjacent spatial coordinates, as shown on the right side of the figure. Increasing the number of intermediate points allows for a smoother representation of the reference path, but the number is determined based on the balance between processing accuracy and speed, as described below.

[0044] 7A to 7E are explanatory diagrams illustrating a method for detecting the center line of the R3 wire among the bonding wires 310 captured in the first captured image. In each of the diagrams in Fig. 7A to 7E, the R3 wire captured in the first image is extracted and shown.

[0045] 7(a) is a diagram showing a virtual superimposition of a projected reference path 401 on an image of the R3 wire. The projected reference path 401 is a collection of line segments sequentially connecting nodes 410, which are two-dimensional coordinates obtained by projectively transforming each spatial coordinate value described in the reference path described with reference to FIG. 6 based on the overhead view direction of the first imaging unit 130. More specifically, each spatial coordinate value described in the reference path is projected onto the XY plane using the angle formed by the optical axis of the first optical system 132 and the substrate surface 320a as the depression angle, and the coordinate values ​​obtained by magnifying each of the projected plane coordinate values ​​according to the image magnification of the first optical system 132 become the coordinate values ​​of the node 401. Therefore, the projected reference path 401 corresponds to an image that appears in the first captured image when the reference path is virtually captured by the first imaging unit 130.

[0046] The actual R3 wire connected by the wire bonder does not necessarily follow the spatial path as designed, and if it follows a spatial path that deviates from the standard, it should be evaluated as a faulty connection. Therefore, first, the center line of the R3 wire in the first captured image is detected.

[0047] 7(b) shows the state in which the line segment between adjacent nodes 410 on the projection reference path 401 is divided into n equal parts (n is a natural number; in the example shown, n=3), and edge search lines 411 perpendicular to the line segment are drawn at each dividing point. The edge search lines 411 are auxiliary lines used to search for the edge that is the boundary between the image of the R3 wire and the background.

[0048] 7(c) shows how edge intersections 412, which are points of intersection with edges, are extracted when an edge is searched for along the edge search line 411. Specifically, the analysis unit 113 extracts the edge intersections 412 by image processing using an edge filter.

[0049] 7(d) shows an inner contour 413 obtained by sequentially connecting, with Bezier curves, the edge intersections 412 extracted inside the projection reference path 401, and an outer contour 414 obtained by sequentially connecting, with Bezier curves, the edge intersections 412 extracted outside the projection reference path 401. Here, the edge intersections 412 are smoothly connected by Bezier curves, but adjacent edge intersections 412 may also be connected by line segments.

[0050] 7(e) shows a first center line 415 that represents the actual on-image path of the R3 wire that appears in the first captured image, calculated as the intermediate line between the inner contour line 413 and the outer contour line 414. The analysis unit 113 determines the first center line 415 detected in this manner as the detected path of the R3 wire in the first captured image. The analysis unit 113 can also calculate a center line (referred to as a second center line) from the R3 wire that appears in the second captured image using a similar procedure, and determines the center line as the detected path of the R3 wire in the second captured image.

[0051] FIG. 8 is an explanatory diagram illustrating a method for analyzing the spatial path of the actual bonding wire from each detected center line. The left side of FIG. 8(a) is an enlarged view of the R3 wire and its surroundings in the first captured image, with a first center line 415, which is the detected path of the R3 wire, superimposed on the image. Also shown are multiple superimposed detected parallel lines 330b, which are auxiliary lines parallel to the edge line 330a of the semiconductor chip 330 detected by image processing. The leftmost detected parallel line 330b is positioned so as to pass through a first reference end point 415a, which is one end of the first center line 415. The right side of FIG. 8(a) is an enlarged view of the R3 wire and its surroundings in the second captured image, with a second center line 416, which is the detected path of the R3 wire, superimposed on the image. Also shown are multiple superimposed detected parallel lines 330b, which are auxiliary lines parallel to the edge line 330a of the semiconductor chip 330 detected by image processing. The leftmost detection parallel line 330b is disposed so as to pass through a second reference end point 416a, which is one end of the second center line 416.

[0052] The first reference end point 415a in the first captured image and the second reference end point 416a in the second captured image can both be considered to correspond to the same observation point (point A) of the R3 wire that contacts the tip electrode 331. Therefore, the first reference end point 415a and the second reference end point 416a are set as reference points without parallax, and the height at these reference points is set as the reference height.

[0053] Based on this idea, Figure 8(b) shows a diagram in which the first center line 415 and the second center line 416 are synthesized so that the first reference end point 415a and the second reference end point 416a overlap, and so that the corresponding detected parallel lines 330b overlap each other. As shown in the figure, the coordinate system on the synthesized image is defined so that the x-axis extends downward and the y-axis extends rightward in the figure, corresponding to the X and Y directions in the spatial coordinate system. At this time, the y-coordinates of the respective detected parallel lines 330b are expressed in order as y a , y b , …y j Let's say.

[0054] For example, y=y b When the detected parallel line 330b is observed, the intersection point with the first center line 415 is (x d1 ,y d ), and the intersection point with the second center line 416 is (x d2 ,y d ) As mentioned above, the first imaging unit 130 and the second imaging unit 140 are installed symmetrically with respect to the YZ plane, so no parallax occurs in the Y-axis direction when observing the same observation point. Therefore, no deviation occurs in the y-axis direction for the images of the same observation point in the first captured image and the second captured image. In other words, it can be said that points with the same y coordinate on the first center line 415 and the second center line 416 are the same point. In other words, the intersection (x d1 ,y d ) and the intersection point (x d2 ,y d ) are the same point (point D) on the R3 wire.

[0055] At this time, the intersection point (x d1 ,y d) and the intersection point (x d2 ,y d ) x coordinate difference d2 -x d1 is proportional to the height of point D. Since the actual height per unit difference coordinate in the composite image can be measured in advance, the difference in x coordinate can be converted to the actual height. In other words, the height (Z coordinate) of point D relative to the reference height can be calculated.

[0056] Also, y=y d The intersection of the detection parallel line 330b and the reference height is (x d0 ,y d ), then x d0 -x d1 =x d2 -x d0 If so, the X coordinate of point D is the same as the X coordinate of point A, but x d0 -x d1 ≠x d2 -x d0 If so, then the X coordinate of point D and the X coordinate of point A are different. d0 -x d1 )-(x d2 -x d0 ) is proportional to the amount of deviation of the X coordinate of point D from the X coordinate of point A. Here, the actual difference in X coordinate per unit difference coordinate in the composite image can be measured in advance, so (x d0 -x d1 )-(x d2 -x d0 ) can be converted into the actual difference in X coordinate. In other words, the X coordinate of point D can be calculated by adding the converted difference in X coordinate to the X coordinate of point A.

[0057] Next, y=y j When the detected parallel line 330b is observed, the intersection point with the first center line 415 is (x j1 ,y d ), and the intersection point with the second center line 416 is (x j2 ,y d ) These intersections are the same point (point J) on the R3 wire as mentioned above. The Z and X coordinates of point J can be calculated in the same way as for point D. Here, at point D, xd2 -x d1 >0, so the Z coordinate of point D is greater than the Z coordinate of point A. In other words, the height of point D is higher than the height of point A. However, at point J, x j2 -x j1 <0, the Z coordinate of point J is smaller than the Z coordinate of point A, that is, the height of point J is lower than the height of point A.

[0058] In this way, y=y b ,…y=y j By repeating the same calculation for each of the detected parallel lines 330b, the spatial coordinates Pa of point A can be calculated as follows, as shown in FIG. 8(c): a ,Y a ,Z a ), the spatial coordinate Pb of point B, the spatial coordinate Pc of point C, ..., and the spatial coordinate Pj of point J can be calculated sequentially. Then, by connecting adjacent points with line segments, a detection result that can be evaluated as the actual spatial path of the R3 wire can be obtained. Then, the analysis unit 113 compares the spatial path obtained as such a detection result with the reference path included in the path information, and can evaluate the connection as proper if the deviation between the two is within a reference range, or evaluate the connection as faulty if the deviation exceeds the reference range.

[0059] The analysis unit 113 can check whether there is a mismatch between the image of the R3 wire extracted from the fifth captured image output by the fifth imaging unit 170 and the spatial path obtained as the detection result. For example, the analysis unit 113 can check the reliability of the spatial path obtained as the detection result by projecting the spatial path obtained as the detection result onto the XY plane and evaluating the degree of match between the projected path on the fifth captured image obtained by magnifying and converting each of the projected plane coordinate values ​​according to the image magnification of the fifth optical system 172 and the center line extracted from the image of the R3 wire on the fifth captured image. If the degree of match is low, for example, the analysis unit 113 can simply perform the process of calculating the spatial path again.

[0060] The analysis unit 113 uses the first captured image and the second captured image to analyze the spatial paths of all the bonding wires 310 belonging to the first group 311 as described above. Also, using the third captured image and the fourth captured image, the analysis unit 113 analyzes the spatial paths of all the bonding wires 310 belonging to the second group 312 as described above.

[0061] Next, we will summarize a series of inspection procedures performed by the inspection device 100. Fig. 9 is a flow diagram illustrating the inspection procedures for the mounting structure 300. The flow starts with the mounting structure 300, which is the object of observation, being placed on the stage 190.

[0062] In step S101, the imaging control unit 111 transmits an imaging request signal to the first imaging unit 130. Upon receiving the imaging request signal, the first imaging unit 130 captures an image of the entire mounting assembly 300 including the bonding wire 310 to be inspected, and generates image data. The imaging control unit 111 receives the image data generated by the first imaging unit 130 and passes it to the analysis unit 113 as image data of the first captured image.

[0063] In step S102, the imaging control unit 111 transmits an imaging request signal to the second imaging unit 140. Upon receiving the imaging request signal, the second imaging unit 140 captures an image of the entire mounting assembly 300 including the bonding wire 310 to be inspected, and generates image data. The imaging control unit 111 receives the image data generated by the second imaging unit 140 and passes it to the analysis unit 113 as image data of the second captured image. Note that the processing of step S101 and the processing of step S102 may be performed in reverse order, or may be performed 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 wires 310 belonging to the first group 311. Then, the analysis unit 113 compares each of the detected spatial paths with the corresponding reference path to perform an analysis as to whether or not the wiring is proper, for example.

[0065] In step S104, the imaging control unit 111 transmits an imaging request signal to the third imaging unit 150. Upon receiving the imaging request signal, the third imaging unit 150 captures an image of the entire mounting assembly 300 including the bonding wire 310 to be inspected, and generates image data. The imaging control unit 111 receives the image data generated by the third imaging unit 150 and passes it to the analysis unit 113 as image data of the third captured image.

[0066] In step S105, the imaging control unit 111 transmits an imaging request signal to the fourth imaging unit 160. Upon receiving the imaging request signal, the fourth imaging unit 160 captures an image of the entire mounting assembly 300 including the bonding wire 310 to be inspected, and generates image data. The imaging control unit 111 receives the image data generated by the fourth imaging unit 160 and passes it to the analysis unit 113 as image data of the fourth captured image. Note that the processing of step S104 and the processing of step S105 may be performed in reverse order, or may be performed in parallel.

[0067] In step S106, the analysis unit 113 uses the third captured image and the fourth captured image as described above to detect the spatial paths of the bonding wires 310 belonging to the second group 312. Then, the analysis unit 113 compares each of the detected spatial paths with the corresponding reference path to analyze, for example, whether the wiring is proper. Note that the processing from step S101 to step S103 and the processing from step S104 to step S106 may be performed in reverse order or may be performed in parallel.

[0068] In step S108, the imaging control unit 111 transmits an imaging request signal to the fifth imaging unit 170. Upon receiving the imaging request signal, the fifth imaging unit 170 captures an image of the entire mounting assembly 300 including the bonding wire 310 to be inspected, and generates image data. The imaging control unit 111 receives the image data generated by the fifth imaging unit 170 and passes it to the analysis unit 113 as image data of the fifth captured image.

[0069] In step S108, the analysis unit 113 extracts the center lines of each bonding wire 310 in the fifth captured image and calculates the degree of match with the spatial path of each bonding wire 310 obtained in steps S103 and S107. If the degree of match is within a predetermined range, the analysis result is evaluated as normal, and the analysis result is displayed on a display monitor, which is one of the input / output devices 123. If the degree of match is beyond the predetermined range, error processing such as repeating the series of processes may be performed. Once the analysis result evaluation by the analysis unit 113 is complete, the calculation processing unit 110 ends the series of processes. Note that the calculation processing unit 110 may omit the processes of steps S107 and S108 and end the series of processes by displaying the analysis result by the analysis unit 113 on the display monitor.

[0070] Next, we will explain an application technique for performing even more accurate analysis of the bonding wire 310. FIG. 10 is an explanatory diagram illustrating one such application technique. Specifically, FIG. 10 corresponds to FIG. 2 and illustrates a state in which the semiconductor chip 330 is fixed and rotated by θ° around the Z axis relative to the substrate 320. In other words, it illustrates a state in which the relative orientation of the substrate 320 and the semiconductor chip 330 is deviated from the expected orientation. Even if the semiconductor chip 330 is fixed and misaligned around the Z axis, the wire bonder detects the board electrodes 321 and chip electrodes 331 to be connected and then bonds the bonding wire 310, so the wire connection process can be completed smoothly. However, due to rotational misalignment of the semiconductor chip 330, adjacent bonding wires 310 may come into contact with each other. Therefore, the inspection device 100 performs a three-dimensional analysis of the connection path, taking into account the rotational misalignment of the semiconductor chip 330.

[0071] Specifically, the analysis unit 113 extracts the reference mark 322 and the edge line 330a of the semiconductor chip 330 from the fifth captured image, and calculates the rotation center coordinate and the rotation amount of the semiconductor chip 330 around the Z axis relative to the substrate 320. Then, the analysis unit 113 reads out the path information 122 of the bonding wire 310 (e.g., R3 wire) to be detected, and performs affine transformation on each of the spatial coordinates of the reference path using the calculated rotation center coordinate and rotation amount. The subsequent process of performing projective transformation and applying it to the first captured image and the second captured image is as described using FIG. 7.

[0072] For example, the analysis unit 113 analyzes whether the spatial path of each bonding wire 310 calculated in this way is separated from the reference path beyond an allowable range. Furthermore, the analysis unit 113 may analyze whether the calculated spatial path of the bonding wire 310 is in contact with the spatial path of an adjacent bonding wire 310, taking into account the diameter of the bonding wire 310.

[0073] Although the fifth captured image is used to detect the relative orientation between the substrate 320 and the semiconductor chip 330 here, the analysis unit 113 may use any one of the first to fourth captured images, or a combination of these, to detect the relative orientation between the substrate 320 and the semiconductor chip 330. Furthermore, if the semiconductor chip 330 has a reference mark, the relative orientation may be detected by referring to the reference mark.

[0074] Although the inspection device 100 has been described above as an example of an inspection device, the device configuration and processing method of the inspection device according to this embodiment can be modified in various ways. For example, the aperture of each imaging unit installed to satisfy the Scheimpflug condition is set to a loop height H corresponding to the bonding wire 310 to be observed. W Assuming that the depth of field is D P However, if the imaging unit adopts a variable aperture, the size of the aperture opening can be adjusted depending on the mounted object to be observed. For example, if the expected loop height H W For a high-intensity mounting body, the aperture should be made smaller to reduce the depth of field D PConversely, the assumed loop height H W For a low-field mounting object, the aperture should be enlarged to increase the depth of field D P In this case, if the aperture is made smaller, the intensity of the light irradiating the mounted body should be increased, and conversely, if the aperture is made larger, the intensity of the light irradiating the mounted body should be decreased.

[0075] Furthermore, in the inspection device 100, one first captured image and one second captured image are used to detect the spatial path of each of the bonding wires 310 belonging to the first group 311, but, for example, it is also possible to detect the spatial path of one specific bonding wire 310 from one first captured image and one second captured image. In this way, if the acquired first captured image and second captured image are used to detect the spatial path of one bonding wire 310, it is possible to relax, for example, the required specifications of the optical system.

[0076] Although the optical systems of the first imaging unit 130 through the fourth imaging unit 160 are configured to be telecentric on the object side, telecentric optical systems are not necessarily required. If an object of the same size actually has different sizes on the image depending on its position in the depth direction, the analysis unit 113 can simply convert the size on the image depending on its position in the depth direction. While the optical systems and imaging elements of each of the imaging units, the first imaging unit 130 through the fourth imaging unit 160, are arranged so that the Scheimpflug condition is satisfied, they can also be replaced with general imaging units whose imaging planes and focal planes are parallel. In this case, it becomes difficult to include the entire bonding wire 310 in the depth of field. However, by reducing the number of bonding wires 310 analyzed at one time, it is possible to focus on and image only that bonding wire 310, and thus at least that bonding wire 310 can be analyzed. In this case, by repeating the analysis while sequentially displacing the mounting body 300 in the planar direction relative to the imaging units, analysis results for all bonding wires 310 can be obtained.

[0077] Furthermore, in the inspection device 100, the analysis process is performed using a combination of the first imaging unit 130 and the second imaging unit 140, and a combination of the third imaging unit 150 and the fourth imaging unit 160, which are arranged in positions facing each other, but the combinations are not limited to this. Even if the combination is not two imaging units arranged in positions facing each other, as long as there is a combination of imaging units that image the mounting body 300 from different directions, the two images obtained from each imaging unit will be parallax images of each other, and therefore the spatial path of the bonding wire 310 can be detected.

[0078] In addition, in the inspection device 100, it has been described that one end of each bonding wire 310 is connected to the substrate 320 and the other end is connected to the semiconductor chip 330. However, the inspection device may also be one that inspects bonding wires that are formed on the semiconductor chip in a pin shape or the like with one end open. Furthermore, the inspection device is not limited to bonding wires connected to the substrate and the semiconductor chip, but may be an inspection device that inspects bonding wires that are connected to the substrate and another element, or that are connected to the substrate with one end open. [Explanation of symbols]

[0079] 100... inspection apparatus, 110... arithmetic processing unit, 111... imaging control unit, 112... acquisition unit, 113... analysis unit, 121... storage unit, 122... route information, 123... input / output device, 130... first imaging unit, 131... first imaging element, 132... first optical system, 132a... object-side lens group, 132b... image-side lens group, 133... aperture, 140... second imaging unit, 141... second imaging element, 142... second optical system, 142a... object-side lens group, 142b... image-side lens group, 143... aperture, 150... third imaging unit, 151... third imaging element, 152... third optical system, 160... fourth imaging unit, 161... fourth imaging element, 162... fourth optical system, 170... fifth imaging unit Image unit, 171... fifth imaging element, 172... fifth optical system, 190... stage, 300... mounting body, 310... bonding wire, 311... first group, 311a... first side, 311b... second side, 312... second group, 320... substrate, 320a... substrate surface, 321... substrate electrode, 322... reference mark, 330... semiconductor chip, 330a... edge line, 330b... detection parallel line, 331... chip electrode, 401... projected reference path, 410... node, 411... edge search line, 412... edge intersection, 413... inner contour line, 414... outer contour line, 415... first center line, 415a... first reference end point, 416... second center line, 416a... second reference end point

Claims

1. An inspection device for bonding wires connected between a substrate and a semiconductor chip, comprising: a first imaging unit for capturing an image of the bonding wire from above; a second imaging unit for capturing an image of the bonding wire from a direction different from the bird's-eye view direction of the first imaging unit; an acquisition unit that acquires path information regarding a preset reference path of the bonding wire; an analysis unit that analyzes a spatial path of the bonding wire by defining and comparing the bonding wire shown in a first captured image output by the first imaging unit and the bonding wire shown in a second captured image output by the second imaging unit based on the path information acquired by the acquisition unit; and An inspection device comprising:

2. 2. The inspection device according to claim 1, wherein the analysis unit detects the edge of the bonding wire that appears in the first captured image using the reference path that has been projectively transformed based on the overhead direction of the first imaging unit, and detects the edge of the bonding wire that appears in the second captured image using the reference path that has been projectively transformed based on the overhead direction of the second imaging unit.

3. The inspection device according to claim 2 , wherein the analysis unit detects the edge based on a plurality of normals set with respect to the reference path that has been subjected to projective transformation.

4. The inspection device described in claim 2, wherein the analysis unit determines a first center line relative to the extension direction of the bonding wire defined in the first captured image, determines a second center line relative to the extension direction of the bonding wire defined in the second captured image, and analyzes the spatial path of the bonding wire by comparing the first center line with the second center line.

5. 5. The inspection device according to claim 4, wherein the analysis unit calculates three-dimensional coordinates for each of the intersections between the first center line and a plurality of parallel lines set relative to the edge of the semiconductor chip shown in the first captured image and the intersections between the second center line and a plurality of parallel lines set relative to the edge of the semiconductor chip shown in the second captured image, thereby analyzing the spatial path of the bonding wire.

6. The inspection device according to claim 1, wherein the analysis unit detects the relative attitude of the substrate and the semiconductor chip, and determines the bonding wire that appears in the first captured image and the bonding wire that appears in the second captured image using the path information corrected based on the relative attitude.

7. the first imaging unit has an optical system and an imaging element arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate is a focal plane, and has an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; 2. The inspection device according to claim 1, wherein the second imaging unit has an optical system and an imaging element arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface is a focal plane, has an aperture adjusted so that the loop height falls within the depth of field, and is installed on the opposite side of the semiconductor chip from the first imaging unit.

8. A method for inspecting bonding wires connected between a substrate and a semiconductor chip, comprising the steps of: a first imaging step of capturing an image of the bonding wire as an inspection target from above using a first imaging unit; a second imaging step of imaging the bonding wire from a bird's-eye view direction different from the bird's-eye view direction of the first imaging unit by a second imaging unit; an acquiring step of acquiring path information regarding a preset reference path of the bonding wire; an analyzing step of analyzing a spatial path of the bonding wire by defining and comparing the bonding wire shown in a first captured image output by the first imaging unit in the first imaging step and the bonding wire shown in a second captured image output by the second imaging unit in the second imaging step based on the path information acquired in the acquiring step; An inspection method having the following.

9. A program for inspecting bonding wires connected between a substrate and a semiconductor chip, a first imaging step of capturing an image of the bonding wire as an inspection target from above using a first imaging unit; a second imaging step of imaging the bonding wire from a bird's-eye view direction different from the bird's-eye view direction of the first imaging unit by a second imaging unit; an acquiring step of acquiring path information regarding a preset reference path of the bonding wire; an analyzing step of analyzing a spatial path of the bonding wire by defining and comparing the bonding wire shown in a first captured image output by the first imaging unit in the first imaging step and the bonding wire shown in a second captured image output by the second imaging unit in the second imaging step based on the path information acquired in the acquiring step; An inspection program that causes a computer to execute the following.

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