Inspection device, inspection method, and inspection program

Abstract

Provided is an inspection device that is a device for inspecting bonding wires connecting a substrate and a semiconductor chip. The inspection device comprises: a first image-capturing unit which is for capturing an image of a semiconductor chip from overhead, which has an aperture that is adjusted such that the loop height of bonding wires to be inspected falls within the depth of field, and which is arranged in a manner in which an optical system and an image-capturing element satisfy the Scheimpflug condition such that a plane parallel to the surface of the substrate is a focal plane; a second image-capturing unit which is for capturing an image of the semiconductor chip from overhead and from a direction different from the overhead direction of the first image-capturing unit; and an analysis unit which three-dimensionally analyzes the connection paths of the bonding wires by comparing a first image output by the first image-capturing unit with a second image output by the second image-capturing unit. When using this inspection device, even if the bonding wires are fine and intricately connected, the connection paths can be three-dimensionally analyzed in a short time and using only a few images.

Description

Inspection device, inspection method, and inspection program

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

[0002] There are known devices for inspecting 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 by 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.

[0003] JP-A-8-75429 JP-A-10-54709

[0004] The technology of Patent Document 1 requires imaging the object of observation 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.

[0006] The 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 includes: a first imaging unit for capturing an image of the semiconductor chip from above, in which the optical system and imaging element are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate is the focal plane, and the imaging unit has an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; a second imaging unit for capturing an image of the semiconductor chip from above from a direction different from the overhead direction of the first imaging unit; and an analysis unit that analyzes the connection path of the bonding wire in three dimensions by comparing the first image output by the first imaging unit with the second image output by the second imaging unit.

[0007] In addition, a second aspect of the present invention provides an inspection method for a bonding wire connected between a substrate and a semiconductor chip, comprising: a first imaging step of capturing an image of the semiconductor chip to be inspected from above using a first imaging unit in which an optical system and an imaging element are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate is the focal plane, and the first imaging unit has an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field;

[0008] The method includes a second imaging step of using a second imaging unit to capture an image of the semiconductor chip from a bird's-eye view in a direction different from the bird's-eye view direction of the first imaging unit, and an analysis step of three-dimensionally analyzing the connection path of the bonding wire by comparing the first image output by the first imaging unit with the second image output by the second imaging unit.

[0009] 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 the following steps: a first imaging step of capturing an image of the semiconductor chip to be inspected from above using a first imaging unit in which the optical system and the imaging element are arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface of the substrate is the focal plane, and the first imaging unit has an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; a second imaging step of capturing an image of the semiconductor chip to be inspected from above using a second imaging unit from a direction different from the overhead direction of the first imaging unit; and an analysis step of three-dimensionally analyzing the connection path of the bonding wire by comparing the first image output by the first imaging unit with the second image output by the second imaging unit.

[0010] 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.

[0011] FIG. 1 is a perspective view schematically showing a main part of an inspection device according to the present embodiment; FIG. 2 is a perspective view schematically showing a mounted body to be inspected; FIG. 3 is an explanatory diagram illustrating a Scheimpflug optical system and its depth of field; FIG. 4 is a system configuration diagram of the inspection device; FIG. 5 is an explanatory diagram illustrating an image captured by an imaging unit; FIG. 6 is an explanatory diagram illustrating the data structure of path information and the concept of a reference path; FIG. 7 is an explanatory diagram illustrating a method for detecting the center line of a bonding wire; FIG. 8 is an explanatory diagram illustrating a method for analyzing the actual spatial path of the bonding wire from each center line of a detected image; FIG. 9 is an explanatory flow diagram showing the inspection procedure for a mounted body; and FIG. 10 is an explanatory diagram illustrating a method for performing an even more accurate analysis.

[0012] 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.

[0013] 1 is a perspective view schematically showing 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 overlooking the stage 190. In the drawing, each imaging unit is shown as floating in midair, but in reality, it is supported by a frame or the like.

[0014] 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 singulation in which multiple mounting bodies 300 are 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 singulation, 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.

[0015] 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 direction and the Y-axis direction 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 .

[0016] The first imaging unit 130 is disposed so as to overlook the mounting assembly 300 placed 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 assembly 300 placed 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 assembly 300 to be observed.

[0017] The first imaging unit 130 includes a first imaging element 131 and a first optical system 132. As will be described in more detail below, 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 below, 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 below, and capture images of the mounted assembly 300 in response to imaging instructions and transmit the generated image data to the imaging control unit.

[0018] The third imaging unit 150 is disposed so as to overlook the mounting assembly 300 placed 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 assembly 300 placed 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 assembly 300 to be observed.

[0019] 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 mounted assembly 300 in response to imaging instructions and transmit the generated image data to the imaging control unit.

[0020] 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.

[0021] 2 is a perspective view schematically showing a mounting assembly 300 to be inspected. In the mounting assembly 300 to be inspected in this embodiment, as described above, a semiconductor chip 330 is fixed on a substrate 320, and the semiconductor chips 330 are 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 wiring path that each bonding wire 310 follows to connect the board electrodes 321 and the chip electrodes 331.

[0022] 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.

[0023] 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.

[0024] 3 is an explanatory diagram illustrating the Scheimpflug optical system and its depth of field employed in the first to fourth imaging units 130 to 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.

[0025] First, the arrangement conditions of the image pickup element and the optical system in the Scheimpflug optical system will be described using the first image pickup unit 130. １ is a plane including the substrate surface 320a, which is the surface of the substrate 320, and is the intended focal plane. ２ is a plane including the principal plane of the first optical system 132, which is made up of the object-side lens group 132a and the image-side lens group 132b. ３ 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 so as to satisfy the Scheimpflug condition, as shown in the figure, the plane S １ , virtual surface S ２ , plane S ３ is a common straight line P １ In other words, the first imaging element 131 and the first optical system 132, which are arranged to satisfy the Scheimpflug condition, can use a plane that intersects obliquely with the light receiving surface of the first imaging element 131 as a focal plane. Therefore, even if the first imaging unit 130 is installed in a position that overlooks the mounting assembly 300 from an oblique direction, the first imaging unit 130 can use the board surface 320a as a focal plane.

[0026] 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. Ｐ is the maximum height of the bonding wire 310 belonging to the first group 311, i.e., the loop height H ＷHere, the loop height H Ｗ is a value greater than the height when the bonding wire 310 is connected according to the design value, and is set to, for example, a value of 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 image the entire bonding wire 310 in a focused state, and the connection path can be properly detected as described later. Note that in the figure, the depth of field D Ｐ The plane S is the intended focal plane. １ Although the actual depth of field D Ｐ In the Scheimpflug optical system, the line P １ The line P is narrow on the side of １ In this embodiment, the depth of field D Ｐ may be adjusted as described above.

[0027] In the example shown in the figure, the plane S １ is a plane including the substrate surface 320a, and the plane S １ is the depth of field D Ｐ is the loop height H Ｗ As long as the loop height H Ｗ plane S so that it coincides with the plane that bisects １ Alternatively, the stage 190 may be moved up and down relative to the first imaging unit 130 and the second imaging unit 140 so that such an inclusive relationship is realized.

[0028] In this embodiment, the object-side lens group 132a realizes telecentricity on the object side. As a result, in the obliquely intersecting focal planes, whether the subject is located in the foreground (positive side of the X axis) or the background (negative side of the X axis), the subject can be imaged at the same magnification on the light-receiving surface of the first image sensor 131 as long as the subject is the same size. In other words, because perspective does not appear in the depth direction of the subject, there is no need to perform zoom conversion according to the depth position of the subject in the captured image, which makes it easy to perform the three-dimensional analysis described below.

[0029] 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 is located on a plane S １ The second image sensor 141 and the second optical system 142 are arranged to satisfy the Scheimpflug condition so that the focal plane is defined by the lens group 142a and the lens group 142b. 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 Ｗ Depth of field D Ｐ The diameter of the aperture 143 is adjusted so that the above is realized.

[0030] 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. Ｐ Loop H Ｗ As long as the focal plane of the first imaging unit 130 and the focal plane of the second imaging unit 140 are included, they do not have to be on the same plane.

[0031] 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.

[0032] Next, a description will be given of 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.

[0033] 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.

[0034] The storage unit 121 is a non-volatile storage medium, and is configured, for example, by a hard disk drive (HDD). 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.

[0035] 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, which 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, which is one of the input / output devices 123.

[0036] The arithmetic processing unit 110 also serves as a functional calculation unit that executes various calculations in response to 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.

[0037] 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 also possible to analyze only the connection path of that bonding wire 310.

[0038] Next, the analysis method of the bonding wire 310 by the analysis unit 113 will be described using 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.

[0039] 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, in the image of the mounting body 300, the portion 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 on the positive side of the Y-axis of the first group 311 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 bonding wires 310 appearing on 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.

[0040] 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 of the first group 311 arranged on the first side 311a on the positive side of the Y-axis 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, as shown in the figure. Similarly to the first captured image, the image is not affected by perspective.

[0041] Here, the second captured image is rotated 180 degrees. As a result, the bonding wire 310 on the first side 311a is positioned on the right side, and thus, similar to its position in the first captured image, the third bonding wire 310 from the top corresponds to the R3 wire. 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 connection path of the R3 wire is calculated by detecting this difference in path.

[0042] 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.

[0043] 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 distinguishes 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.

[0044] In the illustrated example, wire number R3 includes four spatial coordinate values ​​as its reference path. Specifically, the PS(x ｓ , y ｓ , z ｓ ), the end point PE(x ｅ , y ｅ , z ｅ ), the midpoint between the two, PM1(x １ , y １ , z １ ), PM2(x ２ , y ２ , z ２) 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 accuracy and speed of the processing described below.

[0045] 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.

[0046] 7A 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 bird's-eye 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 the image that appears in the first captured image when the reference path is virtually captured by the first imaging unit 130.

[0047] 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 beyond the standard, it should be evaluated as a faulty connection. Therefore, first, the center line of the R3 wire shown in the first captured image is detected.

[0048] 7B shows the state in which the line segment between adjacent nodes 410 on the projected 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.

[0049] 7C 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.

[0050] 7D 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.

[0051] 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, and is 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.

[0052] FIG. 8 is an explanatory diagram illustrating a technique for analyzing the spatial path of the actual bonding wire from each detected center line. The left side of FIG. 8A 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. 8A 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 detected parallel line 330 b is disposed so as to pass through a second reference end point 416 a which is one end of the second center line 416 .

[0053] 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 parallax-free reference points, and the height at these reference points is set as the reference height.

[0054] 8B is a diagram showing a result of combining the first center line 415 and the second center line 416 based on such a concept, 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 combined image is defined by setting the x-axis downward and the y-axis rightward in correspondence with the X and Y directions in the spatial coordinate system. At this time, the y-coordinates of the respective detected parallel lines 330b are set as y ａ , y ｂ , ...y ｊ Let's say.

[0055] For example, y = y ｂWhen the detected parallel line 330b is taken into consideration, the intersection point with the first center line 415 is (x ｄ１ , y ｄ ), and the intersection with the second center line 416 is (x ｄ２ , y ｄ ) As described 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 the same observation point is observed. 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 second center line 416 (x ｄ２ , y ｄ ) are the same point (point D) on the R3 wire.

[0056] At this time, the intersection point (x ｄ１ , y ｄ ) and the second center line 416 (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 the x-coordinate can be converted into the actual height. In other words, the height (Z-coordinate) of point D relative to the reference height can be calculated.

[0057] 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, it can be said that the X coordinate of point D and the X coordinate of point A are different. ｄ０ -x ｄ１ )-(xｄ２ -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. That is, the X coordinate of point D can be calculated by adding the converted difference in X coordinate to the X coordinate of point A.

[0058] Next, y = y ｊ When the detected parallel line 330b is taken into consideration, the intersection point with the first center line 415 is (x ｊ１ , y ｄ ), and the intersection with the second center line 416 is (x ｊ２ , y ｄ ) These intersections are the same point (point J) on the R3 wire as described above. The Z and X coordinates of point J can also be calculated in the same way as for point D. Here, at point D, x ｄ２ -x ｄ１ > 0, so 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, x ｊ２ -x ｊ１ <0, it can be seen that 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.

[0059] 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 are 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. The analysis unit 113 then 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.

[0060] 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 a detection result. For example, the analysis unit 113 projects the spatial path obtained as a detection result onto the XY plane and evaluates the degree of match between the projected path on the fifth captured image obtained by magnifying 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, thereby checking the reliability of the spatial path obtained as a detection result. If the degree of match is low, the analysis unit 113 may, for example, redo the process of calculating the spatial path.

[0061] 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.

[0062] 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 assembly 300. The flow starts with the mounting assembly 300, which is the object of inspection, being placed on the stage 190.

[0063] 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.

[0064] 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.

[0065] 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 the wiring is proper, for example.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] In step S108, the analysis unit 113 extracts the center lines of each bonding wire 310 shown in the fifth captured image and calculates the degree of coincidence with the spatial path of each bonding wire 310 obtained in steps S103 and S107. If the degree of coincidence 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 coincidence exceeds 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 terminates the series of processes. Note that the calculation processing unit 110 may omit the processes of steps S107 and S108 and terminate the series of processes by displaying the analysis result by the analysis unit 113 on the display monitor.

[0071] Next, an application technique for performing even more accurate analysis of the bonding wire 310 will be described. 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, for example, 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.

[0072] 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 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.

[0073] The analysis unit 113 analyzes whether the spatial path of each bonding wire 310 calculated in this manner is separated from the reference path by more than 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.

[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 mounting body with a high depth of field D, the aperture is made smaller. Ｐ Conversely, the assumed loop height H Ｗ For a mounting body with a low depth of field D, the aperture is enlarged. 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, one first captured image and one second captured image may be used to detect the spatial path of one specific bonding wire 310. 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] Furthermore, in the inspection device 100, both the pair of first and second imaging units are configured as imaging units that satisfy the Scheimpflug condition, but one of them may be a general imaging unit whose imaging surface and focal plane are parallel. Even when an imaging unit that satisfies the Scheimpflug condition and a general imaging unit are combined, as long as the mounting assembly 300 is observed from different directions, the two images obtained from each imaging unit will be parallax images of each other, making it possible to detect the spatial path of the bonding wire 310.

[0077] 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-like shape 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.

[0078] 100... inspection apparatus, 110... calculation 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, 414... outer contour, 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 semiconductor chip from above, the first imaging unit having 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 the focal plane, and an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; a second imaging unit for capturing an image of the semiconductor chip from above from a direction different from the direction of the first imaging unit; and an analysis unit for three-dimensionally analyzing the connection path of the bonding wire by comparing the first image output by the first imaging unit with the second image output by the second imaging unit.

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 the 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.

3. A third imaging unit for capturing an image of the semiconductor chip from above in a direction perpendicular to the first imaging unit, the third imaging unit having an optical system and an imaging element arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface is the focal plane, and having an aperture adjusted so that the loop height falls within the depth of field; and a fourth imaging unit for capturing an image of the semiconductor chip from above from the opposite side of the semiconductor chip to the third imaging unit, the fourth imaging unit having an optical system and an imaging element arranged to satisfy the Scheimpflug condition so that a plane parallel to the surface is the focal plane, and having an aperture adjusted so that the loop height falls within the depth of field.

3. The inspection device according to claim 2, wherein the analysis unit compares a first captured image output by a first imaging unit with a second captured image output by the second imaging unit to three-dimensionally analyze a wiring path of the bonding wires that are to be inspected, the bonding wires being deployed from a first side of the side edge of the semiconductor chip that is along a straight line connecting the positions of the first imaging unit and the second imaging unit and a second side opposite the first side, and compares a third captured image output by a third imaging unit with a fourth captured image output by the fourth imaging unit to three-dimensionally analyze a wiring path of the bonding wires that are to be inspected, the bonding wires being deployed from a third side of the side edge of the semiconductor chip that is perpendicular to the first side and a fourth side opposite the third side, and 4. The inspection device according to claim 2, further comprising a fifth imaging unit for capturing an image of the semiconductor chip from directly above, wherein the analysis unit uses a fifth captured image output by the fifth imaging unit to evaluate the analyzed wiring path.

5. An inspection device as described in claim 1, wherein the analysis unit three-dimensionally analyzes the connection paths of each of the multiple bonding wires to be inspected from one of the first captured images and one of the second captured images.

6. The inspection device according to claim 1, wherein the first imaging unit employs a telecentric optical system at least on the object side.

7. An inspection device as described in claim 2, wherein the analysis unit searches for the connection path of the bonding wire to be inspected that appears in each of the first captured image and the second captured image by referring to a predetermined reference path.

8. An inspection device according to claim 7, wherein the analysis unit detects the relative attitude of the substrate and the semiconductor chip, and searches for the wiring path by referring to the reference path corrected based on the attitude.

9. The inspection device described in claim 2, wherein the analysis unit analyzes the connection path of the bonding wire by calculating the intersection of a virtual line generated parallel to the side edge of the semiconductor chip shown in each of the first captured image and the second captured image and the bonding wire to be inspected.

10. A method for inspecting a bonding wire connected between a substrate and a semiconductor chip, comprising: a first imaging step of capturing an image of the semiconductor chip to be inspected from above using a first imaging unit, the first imaging unit having 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 the focal plane, and an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; a second imaging step of capturing an image of the semiconductor chip from above using a second imaging unit from a direction different from the direction of the first imaging unit; and an analysis step of three-dimensionally analyzing the connection path of the bonding wire by comparing the first image output by the first imaging unit and the second image output by the second imaging unit.

11. An inspection program for a bonding wire connected between a substrate and a semiconductor chip, comprising: a first imaging step of capturing an image of the semiconductor chip to be inspected from above using a first imaging unit, the first imaging unit having 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 the focal plane, and an aperture adjusted so that the loop height of the bonding wire to be inspected falls within the depth of field; a second imaging step of capturing an image of the semiconductor chip from above using a second imaging unit from a direction different from the direction of the first imaging unit; and an analysis step of three-dimensionally analyzing the connection path of the bonding wire by comparing the first image output by the first imaging unit and the second image output by the second imaging unit.

Images