JPH0569304B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an imaging inspection of a semiconductor device in which the appearance of the wire bonding state of a semiconductor device that has completed a wire bonding process such as ball bonding or wedge bonding is inspected by imaging. It is related to the device.

[Prior art]

Inspection of the wire bonding state has conventionally been performed manually and visually by an operator.
Inspection items include, for example, in the case of ball bonding, no wire, wire breakage, misbond (bond in the wrong place), wire height,
These include wire curl (excessive bending), lift bond (lifting of the bond), pad, bond position relative to the lead, ball or stitch size and shape, etc.

Among these, from “no wire” to “lift bond”
Inspections for the previous items were performed visually using a low-magnification microscope with a wide field of view that included the entire IC chip and its surrounding bonding parts.

[Problem that the invention seeks to solve]

However, in conventional inspections using such means, although it is possible to grasp the three-dimensional shape of the wire using a binocular microscope, since it is a visual inspection, it is difficult to inspect a large number of items on a large number of bonding parts. Inspection efficiency is low because it takes a lot of time, and the bonding condition is good.
Because the inspector relies on his or her intuition to judge defects, there are many variations in the inspection results.Furthermore, since the inspection is performed using a microscope from above the front to diagonally downward, there is a difference in distance between the front and back sides. Due to the distortion of the image caused by this, it was easy to make errors in determining the amount of deflection of the wire, resulting in low inspection accuracy.

In addition, attempts have been made to inspect the amount of deformation in the height direction of the wire by using a lens with an extremely shallow depth of focus and moving the camera up and down to focus on each point in the height direction of the wire. In addition to taking time to move the camera in different directions, the lens has a high magnification and has a narrow field of view, and in order to cover a wide area around the IC chip, it is necessary to move the camera in a horizontal plane for each pad and lead. It was time consuming and the inspection efficiency was low.

The present invention solves the above problems of the conventional ones,
Inspection efficiency is improved by determining a large number of input data signals from images within a wide field of view in an extremely short time, and the criteria for determining good and bad are quantified.
Moreover, it is an object of the present invention to provide an imaging inspection apparatus for a semiconductor device that does not cause distortion due to distance on the entire inspection surface, reduces errors, and improves inspection accuracy.

[Means for solving problems]

As a means for solving the above-mentioned problems, the present invention provides an imaging inspection apparatus for a semiconductor device that performs an external appearance inspection of a semiconductor device after wire bonding. a plurality of imaging units each having a light-receiving surface for forming an image by a lens system; an optical/electrical signal converter that converts an image signal on the light-receiving surface of the imaging unit into an electrical signal; and digitizing the electrical signal. an arithmetic circuit that synthesizes digital signals from at least two of the imaging units to obtain data on the three-dimensional position of the object; a memory circuit that stores digitized standard data regarding inspection items; - an image processing device that compares an input data signal digitized based on an electrical signal converted from an electrical signal with a standard data signal based on the standard data to determine whether the input data is normal or abnormal; Each of the imaging units has a light-receiving surface parallel to the inspection surface of the semiconductor device to be inspected, and a central axis connecting the center of the light-receiving surface of each imaging unit and the center of the lens system is parallel to the inspection surface. It is an object of the present invention to provide an imaging device for inspecting a semiconductor device, which is characterized in that it is arranged so as to intersect with each other.

[Effect]

Since the present invention is configured as described above, it is possible to use a lens with low magnification, to perform imaging inspection with the entire bonding area around the IC chip in one wide field of view, and to move the imaging device in a horizontal plane. There is no need to move each lead,
Since a low magnification lens can be used to grasp the three-dimensional shape of the object, the depth of focus is deep, there is no need to move the imaging device up and down, and there is no need for the time associated with these movements. Many types of signals from many parts of the entire visual field,
Since it is possible to make a determination by comparing with a standard data signal by scanning one frame or several frames in a short time, the inspection time is shortened and the inspection efficiency is improved.

In addition, the judgment of normal or abnormal input data is quantified, there is less variation due to individual differences among inspectors, there is no distortion of perspective over a wide field of view, which reduces errors, and it is possible to use low-magnification lenses. This allows for a deep depth of focus, making it easy to focus on the entire field of view, and improving inspection accuracy.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, a supply magazine 2 containing semiconductor devices such as lead frames that have undergone a wire bonding process is placed on a base frame 1 of the main body of the inspection device, and a supply elevator 3 (e.g. Jitsukai Showa 61-116632
Publication No. 119532, Publication No. 119532, Publication No. 119532, Utility Model Application No. 62-
20017 Publication), an inspection stage 4 that performs a visual inspection, and an extrusion device 5 that pushes out and supplies the semiconductor devices in the supply magazine 2 one by one to the inspection stage 4 (for example, Utility Model Application Laid-Open No. 61-185741, Kaisho
62-2543)), the semiconductor device 6 supplied to the inspection stage 4 is intermittently transferred through a low magnification inspection point 7, a high magnification inspection point 8, and a marking point 9. (See Publication No. 63-9946), a storage magazine 11 that accommodates semiconductor devices that have been inspected and marked, and a storage elevator 1 that raises and lowers the storage magazine 11.
2 are provided. One set of the transfer device 10 may move a plurality of semiconductor devices at the same time, or a plurality of sets may be used to move the semiconductor devices simultaneously or individually.

An imaging device for imaging a semiconductor device includes a low magnification imaging device 14 provided on an XY table 13 and an XY
It consists of a high-magnification imaging device 16 provided on a table 15, and is configured to image a predetermined portion of the semiconductor device 6 at a low-magnification inspection point 7 and a high-magnification inspection point 8, respectively. 17 is a monitor that displays the captured image.

A marking device 18 attaches a mark indicating that the semiconductor device is defective to a portion of the semiconductor device that has a defective inspection result, and is adapted to attach a mark at a marking point 9 according to the inspection result.

The field of view of the low-magnification imaging device 14, as shown at 19 in FIG. Inspect shape and dimensions.

If the IC chip 20 is particularly large, such as a super LSI, it is divided into a plurality of fields of view and moved by the XY table 13 to inspect the whole.

The field of view of the high magnification imaging device 16 is such that the bonding condition near one pad 22 (or lead) can be seen, as shown at 21 in FIG. 3, and the position, shape, and size of the ball and stitches are mainly inspected. This field of view 21 moves for each pad and lead, but it has already been obtained with the low magnification imaging device 14.
Since the position of each pad is calculated based on the amount of deviation of the IC chip 20 and stored in the memory circuit,
When moving the field of view, there is no need to detect the pad position again during high-magnification imaging, and the pad position can be quickly moved using the calculated position as the target.

Examples of the low magnification imaging device 14 are shown in FIGS.
It is shown in FIG.

The low-magnification imaging device 14 includes lens systems 23A, 23B, and 23 each composed of one or more lenses.
C, light-receiving surfaces 24A, 24B, 24C equipped with a vidicon or solid-state image sensor, and an optical/electrical converter 25
A, 25B, 25C, lens barrel 26A, 26B, 26
C, an imaging unit 27A, 27B, 27C consisting of an aperture 45A, 45B, 45C, and a central axis 28 connecting the center of each light-receiving surface and the center of the lens.
A, 28B, and 28C coincide with and intersect with the low magnification inspection point 7 on the inspection surface of the IC chip 20 to be inspected, and in the plan view, the central axis 2 as shown in FIG.
8A and 28C are oriented in opposite directions (180° direction), and central axis 28B is perpendicular to central axes 28A and 28C. The lens surfaces of each lens system 23A, 23B, 23C (surfaces perpendicular to the main axis of the lens) and the light receiving surfaces 24A, 24B, 24C are all inspection surfaces.
It is held parallel to the surface of the IC chip 20. That is, the planes 41, 42, and 43 are parallel.

When the respective imaging units 27A, 27B, 27C are arranged as described above and imaged, the central axes 28A, 28
Although B and 28C are tilted with respect to the surface of the IC chip 20, the light receiving surfaces 24A, 24B, and 24C are
The image formed is in focus over the entire field of view in Fig. 2, and it looks as if the image was taken from directly above.For example, the IC chip 20 remains in a rectangular or square shape without distortion due to the distance from the lens. to form an image.

However, since images are taken from an oblique angle, objects with different heights are
B, 27C are imaged with different shapes and dimensions,
The three-dimensional position of each part is calculated by calculating and synthesizing the two-dimensional position signals on each light-receiving surface obtained by digitizing the imaging signals of at least two of the imaging units using an arithmetic circuit.
A digital signal of the shape can be obtained.

When the three imaging units 27A, 27B, and 27C take images of the IC chip 20 as shown in FIG.
The images of the wire 30 are captured as shown in FIGS. The three-dimensional positions of points P, Q, etc. can be determined. 31 is a lead, 32 is a ball, and 33 is a stitch.

For example, if the bonding section 29' is in a normal state, the imaging units 28A and 28C take an image as shown in FIG. 8a, and the imaging unit 28B takes an image as shown in FIG. 8b, and both images are scanned. By digitally processing each position of the wire 30 and performing a composite calculation, the three-dimensional position of any point on the wire 30 can be determined.

The digital input data signal regarding the actual object obtained in this way is compared with the digital standard data signal already stored in the memory circuit, and the low magnification imaging device 14 detects the positional deviation of the IC chip 20 and the Missing wires, broken wires, misbonds (bonds in other incorrect locations), incorrect wire heights, wire curls (lateral deviation, contact with adjacent wires), lift bonds (ball 32 or stitch 33 bonding to pad 22 or It is possible to inspect the presence or absence of a defect such as the lead 31 floating up from the lead 31 and not making contact.

At this time, it is not necessary to inspect each wire individually; instead, it is possible to inspect several wires at a time and scan the entire wire in blocks and divide it into several frames, or scan the entire wire in one frame and digitally process it. The inspection time can be extremely shortened. Furthermore, by quantifying the allowable limit, there is no variation in inspection, the entire inspection surface is in focus, there is no shape distortion due to distance, errors are reduced, and accuracy is improved.

There may be only two sets of imaging units. The directions of the central axes of the two or three sets of imaging units can be arbitrarily selected. For example, in FIGS. 4 to 6, only the imaging unit 27A may be vertical.

In addition to the imaging unit shown in FIGS. 4 to 6, another recognition unit or other unit may be provided vertically in the center directly above the low magnification inspection point 7.

The lens surfaces of the lens systems 23A, 23B, and 23C are not necessarily parallel to the inspection surface, for example, the central axis 2
It may be perpendicular to 8A, 28B, and 28C. At this time, the entire field of view cannot be brought into focus accurately, but if the depth of focus is deep, this can be compensated for and practically the entire field of view can be brought into focus.

In the high-magnification imaging device 16, pattern recognition is performed using an image magnified in a narrow field of view as shown in FIG. Misalignment, ball 32
The shape and dimensions of the stitch 33 (or the stitch 33) can be compared with pre-stored standard data to check for defects.

FIG. 9 is an explanatory diagram of the signal path, where 35 is a camera control unit, 36 is a pattern recognition unit as an image processing device, 37 is an interface control system, 38 is a CPU, 39 is a memory circuit,
40 is a stage driver, and 41 is another driver.

The memory circuit 39 stores standard data regarding each inspection item, a calculation program for calculating a three-dimensional position by combining two-dimensional position data from two imaging units, and the like.

In the camera control unit 35,
The entire field of view or the field of view is divided into a plurality of blocks, one or several frames are scanned, a digital imaging signal is output, and the pattern recognition unit 3
6, the input signal is compared with a standard data signal based on the standard data from the memory circuit 39 to determine whether the input data signal is normal or abnormal;
If it is defective, it sends a signal to the marking device 18,
Add a mark near the applicable IC.

In addition to the imaging screen as inspection information, the monitor 17 is designed to display inspection values, defective locations, defect analysis, etc. in real time, so depending on the situation, feedback can be immediately sent to the bonding machine for actions such as setting bonding conditions. can be done promptly.

In addition, by aggregating inspection data, it is possible to quickly respond to defects occurring in the previous process.
Production yield can be improved.

10 and 11 show examples of lighting equipment at the low magnification inspection point 7. IC at low magnification inspection point 7
An illumination lamp 46 having an annular light source is provided so as to surround the chip 20 and at a low position close to the inspection surface. By being illuminated from the periphery and from a low position, the three-dimensional shape of the bonding wire 30 can be clearly imaged without error.

〔Effect of the invention〕

In the present invention, a plurality of imaging units whose light-receiving surfaces are arranged parallel to the inspection surface of the semiconductor device are arranged so that their central axes intersect with the inspection surface, making it possible to grasp the bonding shape and dimensions three-dimensionally. It is now possible to use a low magnification lens, which provides a wide field of view.
Moreover, even though the image is taken from an angle, there is no distortion due to distance, and a lens with a deep depth of focus can be used, making it easy to focus on the entire field of view, and the imaging device can be moved vertically and horizontally. In addition, since the imaging data is digitally processed and compared with standard data to determine whether the bonding condition is good or bad, many parts of the entire area with a wide field of view can be inspected. Many types of signals can be compared and judged with standard data in a short time, reducing inspection time and improving inspection efficiency.
It is possible to provide an imaging inspection apparatus for semiconductor devices in which abnormality determination is quantified, variations due to individual differences among inspectors are eliminated, and errors due to defocus and perspective distortion are eliminated, and inspection accuracy is improved. It has a great practical effect.

[Brief explanation of drawings]

The drawings relate to embodiments of the present invention, and FIG. 1 is an overall perspective view, FIG. 2 is a field of view of a low-magnification imaging device, FIG. 3 is a field of view of a high-magnification imaging device, and FIG. 4 is a low-magnification imaging device. 5 is a cross-sectional front view of the device taken along a vertical plane passing through the low magnification inspection point 7 and parallel to the transport direction of the semiconductor device 6; FIG. 5 is a side view of the cross-section along the - line; FIG. Figures a, b, and c are explanatory diagrams of how images appear when one bonding part is imaged with different imaging units, and Figures 8a and b are illustrations of images when another bonding part is imaged with different imaging units. An explanatory diagram of how it looks, Fig. 9 is an explanatory diagram of the signal path, Fig. 10 is a plan view of an embodiment of the lighting device,
FIG. 11 is a sectional front view taken along the line --. DESCRIPTION OF SYMBOLS 1... Base frame, 2... Supply magazine, 3... Supply elevator, 4... Inspection stage, 5... Extrusion device, 6... Semiconductor device, 7
...Low magnification inspection point, 8...High magnification inspection point, 9...
Marking points, 10...transfer device, 11...storage magazine, 12...storage elevator, 13...
...XY table, 14...Low magnification imaging device, 15
...XY table, 16...High magnification imaging device, 1
7...Monitor, 18...Marking device, 19
...Field of view, 20...IC chip, 21...Field of view,
22... Pad, 23A, 23B, 23C... Lens system, 24A, 24B, 24C... Light receiving surface, 2
5A, 25B, 25C...Optical/electrical converter, 26
A, 26B, 26C...sharp tube, 27A, 27B,
27C...imaging unit, 28A, 28B, 28
C... Central axis, 29, 29'... Bonding part,
30... Wire, 31... Lead, 32... Ball, 33... Stitch, 34... Transparent body, 35...
...Camera control unit, 36...Pattern recognition unit, 37...Interface control system, 38...CPU, 39...Memory circuit, 40
...Stage driver, 41...Other drivers,
42, 43, 44...plane, 45A, 45B, 4
5C...Aperture, 46...Illuminating light.

Claims (1)

[Scope of Claims] 1. An imaging inspection apparatus for a semiconductor device that performs an external appearance inspection of a semiconductor device after wire bonding by imaging, comprising: a lens system comprising one or more lenses;
a plurality of imaging units each having a light receiving surface for forming an image by the lens system; an optical/electrical signal converter for converting an image signal on the light receiving surface of the imaging unit into an electrical signal; and a light/electrical signal converter for converting the electrical signal into an electrical signal. , an arithmetic circuit that synthesizes digital signals from at least two of the imaging units to obtain data on the three-dimensional position of the object; and a memory circuit that stores digitized standard data regarding inspection items; an image processing device that compares an input data signal digitized based on an electrical signal converted from an optical/electrical signal with a standard data signal based on the standard data to determine whether the input data is normal or abnormal; The imaging units are arranged so that their respective light receiving surfaces are parallel to the inspection surface of the semiconductor device to be inspected, and the central axis connecting the center of the light receiving surface of each imaging unit and the center of the lens system is parallel to the inspection surface. 1. An imaging inspection apparatus for semiconductor devices, characterized in that the apparatus is arranged so as to intersect with each other. 2. The apparatus according to claim 1, wherein a lens surface of the lens system perpendicular to the lens principal axis is arranged parallel to the inspection surface.