JPH11150142A - Method and device for inspecting wiring bonding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an electrode pattern section and a wire section easily distinguishable from each other by having an inspection area irradiated with light having such a spectrum that reflectivity is low on the surfaces of wires and high at an electrode section, and analyzing images formed by the reflection of the light. SOLUTION: Light projected upon an object to be inspected is reflected by an electrode section 51 and a ball section 54 and forms an image in an image-pickup device. When the light has a wavelength of <=550 nm, light 52 projected upon the electrode section 51 is of high reflection, and light 53 projected upon the ball section 54 is of low reflection, because the electrode section 51 is formed of an aluminum pattern and wires 55 are made of gold. When the object is irradiated with light having a wavelength of >=550 nm on the other hand, both the electrode section 51 and the ball section 54 shows high reflection the light, and both the electrode and the ball sections 51 and 54 become bright in the image. Therefore, the electrode and the ball sections 51 and 54 are easily distinguishable from each other by comparing these images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method and apparatus for inspecting the appearance of a semiconductor device after wire bonding, and more particularly, to a method for inspecting the appearance of wire bonding using a gold wire. And devices.

[0002]

2. Description of the Related Art Conventionally, appearance inspection after bonding has been performed exclusively by visual inspection by an inspection operator.
A method has been adopted in which an image of a semiconductor device after the bonding step is completed is observed with an optical microscope or an imaging device having a magnifying function, and quality is qualitatively determined. In recent years, as shown in, for example, Japanese Patent Application Laid-Open No. 5-121512, a normal state of a semiconductor device to be inspected is stored in a storage device as data, and then the imaging device and the semiconductor device are relatively moved. An external image is captured, and the captured external image is analyzed by an image processing apparatus to extract outlines of components such as a lead frame, a semiconductor chip (hereinafter, referred to as a chip), bonding wires, and the like, which are components of the semiconductor device. A technique has been reported in which after determining the position and shape of the element, the quality of the bonding state is determined by comparing with a predetermined quality determination criterion for each of the constituent elements.

FIG. 7 is a view showing the configuration of the above-mentioned conventional example. A light source 11 for epi-illumination that irradiates a semiconductor device, which is a test object 1, mounted on a sample table 2 through a half mirror 21. While sequentially switching between the ring illumination light source 12 having a plurality of irradiation angles and the image pickup device 31, an image is captured by the imaging device 31 driven by the drive stage 3, and the captured image is binarized or multi-valued by the image analysis device 43. The analysis process is performed to calculate the shape and position of the wire portion.

In Japanese Patent Application Laid-Open No. 7-58500,
In order to extract only a wiring pattern on a printed circuit board, an example is shown in which an image is captured using illumination light of 650 nm or less so that the reflectance is different between the copper electrode part on the board and the aluminum electrode part of the electronic component. And Japanese Patent Laid-Open No. 8-
Japanese Patent No. 29138 discloses an LE arranged in a hemispherical dome shape.
An example in which a pattern defect inspection is performed by illuminating a printed board with D has been reported.

[0005]

However, in the above conventional example, in the case of a wire bonding inspection apparatus as disclosed in, for example, Japanese Patent Application Laid-Open No. 5-121512, the illumination light source is not particularly specified, and a white light bulb is generally used. Because a red light LED that can easily obtain a relatively high luminance is used, or an aluminum pattern forming an electrode portion on a semiconductor device, and a gold wire of a wire portion are used. There is a small difference in the reflection characteristics with respect to the portion, and there is a defect that the bright spot on the electrode portion and the bright spot on the wire are erroneously recognized.

FIG. 4 shows a state in which the surface of the wire-bonded semiconductor device is enlarged and observed from the side. In FIG. 4, reference numeral 51 denotes an electrode portion on the surface of the semiconductor device;
Indicates a ball portion of the bonded wire portion 55.

Here, since the ball portion 54 is sandwiched between the tip of the capillary (not shown) and the surface of the chip when it is crimped on the semiconductor device, it is substantially parallel to the electrode portion 51 as shown in FIG. A flat surface portion is formed.

On the other hand, when epi-illumination is used to observe the bonding portion, the illumination light 52, 53
To the illumination light 5 reflected by the electrode unit 51 because the light is perpendicularly reflected and specularly reflected to form an image on the imaging device 31.
2 and the illumination light 53 reflected on the flat portion of the ball portion 54 form an image on the imaging device 31 under the same conditions, and an image as shown in FIG. 5A is formed.

Here, in the image shown in FIG.
1 and the flat portion of the ball portion 54 are similarly captured as high-luminance portions, so that it is difficult to identify the two when performing image analysis by the image analysis device 43, and to incorrectly recognize the shape or position of the ball portion. Often.

In Japanese Patent Application Laid-Open No. 7-58500B, since the object to be inspected is a wiring pattern on a printed circuit board, illumination light that can recognize the copper electrode section on the board and the aluminum electrode section of the electronic component is used. Therefore, the method cannot be applied to the inspection of the bonding wire.
No. 9138 merely shows an example of a structure arranged in a hemispherical dome shape as so-called dark-field illumination or diffuse illumination, and it cannot be desired to improve the discrimination performance between the electrode portion and the wire portion.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has been made capable of capturing an image in which an electrode pattern portion and a wire portion on a chip can be easily identified. It is an object of the present invention to provide a wire bonding inspection method and apparatus for performing an inspection by illuminating with an illumination light, and even when a light source that emits white illumination light is used, an electrode pattern portion on a chip and An object of the present invention is to enable capturing of an image that can be easily distinguished from a wire portion.

[0012]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned problems of the prior art as follows.

The inspection area has a low reflectance on the wire surface,
In addition, the state of bonding is inspected by irradiating with illumination light having a spectrum having a high reflectance at the electrode portion and analyzing an image formed by reflection of the illumination light. More specifically, the inspection area has an observation image in a wavelength region having a low reflectance at the wire surface and a high reflectance at the electrode portion, and a spectrum having a high reflectance at the wire surface and the electrode portion. The electrode portion and the wire portion are identified by comparing the observation image in the wavelength region.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The wire bonding inspection method according to the present invention illuminates an inspection area with illumination light having a spectrum having a low reflectance on a wire surface and a high reflectance on an electrode portion. It is characterized by taking in an image formed by reflection of light, and even if conditions for reflecting illumination light to both the electrode portion and the wire portion are equal, high reflection is obtained at the electrode portion, and the wire portion is obtained. In this case, the reflection becomes low, and the image of the electrode portion and the image of the wire portion can be easily distinguished.

[0015] Further, the inspection area is formed by an observation image in a wavelength region having a spectrum having a low reflectance on the wire surface and a high reflectance on the electrode portion, and a spectrum having a high reflectance on the wire surface and the electrode portion. It is characterized by discriminating between the electrode portion and the wire portion by comparing the observation image in the wavelength region having the image portion, and comparing two types of images in which the image of the wire portion has changed without changing the image of the electrode portion. This makes it possible to identify only the wire portion.

A wire bonding inspection apparatus according to the present invention comprises: mounting means for mounting a wire-bonded semiconductor chip and a lead frame; an illuminating device for illuminating a region to be inspected; and an imaging device for imaging a wire to obtain an image signal. Means for inspecting a bonding state based on the image signal, wherein the lighting device has a low reflectance on the wire surface in the inspection area, and an electrode. It is characterized by irradiating with illumination light having a spectrum with a high reflectance at the portion.

[0017] The image analysis device may include an observation image in the wavelength region having a spectrum in which the reflectance on the wire surface is low and the reflectance on the electrode portion is high, and the reflectance on the wire surface and the electrode portion. Is characterized in that the electrode part and the wire part are distinguished by comparing with an observation image in a wavelength region having a high spectrum.

As a light source for generating the illumination light, blue L
ED is used.

A white light source is used as a light source for generating the illumination light, and a wavelength filter is inserted into an optical path of the illumination light or the reflected light to perform illumination with blue illumination light, or a blue light is selected from the reflected light. Is selectively extracted and used.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a drawing that best illustrates the features of the present invention. Hereinafter, a wire bonding inspection apparatus according to the present invention (hereinafter, referred to as the present apparatus) will be described with reference to FIG.
Will be described.

In FIG. 1, reference numeral 1 denotes a test object, 2 denotes an inspection stage for moving the test object 1 (hereinafter, referred to as a stage), 5 denotes an aperture device for adjusting the depth of focus and light quantity of an image pickup system, and 6 denotes a diaphragm device. An optical adjustment device for adjusting an illumination light amount and an illumination wavelength, 11 a light source (white light source) for generating illumination light,
31 is an imaging device for capturing an image of the test object 1, 7 is a condenser lens, 21 is a half mirror, 41 is an input device 4.
A controller 43 connected to the controller 2 for controlling the entire apparatus;
Is an image analysis device for adding arithmetic processing to the image captured by the imaging device 31. Reference numeral 44 denotes an image sensor driving circuit, 45 denotes a lamp power supply circuit, 46 denotes an actuator driving circuit, and 47 denotes a stage driving circuit.

The test object 1 is fixed after being transferred onto the stage 2 by a transfer device (not shown).
It moves to a position specified in advance by the instruction 1. On the other hand, the illumination light emitted from the light source 11 is
After that, blue illumination light having a wavelength of 550 nm or less selectively extracted by the optical adjustment device 6 is irradiated onto the test object 1 via the half mirror 21.

As shown in FIG. 4, the illuminating light radiated onto the test object 1 is reflected on the electrode portion 51 and the ball portion 54 as in the conventional example, and is again reflected by the image pickup device 31 via the half mirror 21.
At this time, the illumination light generally has a property of exhibiting a reflection characteristic as shown in FIG. 6 depending on the material of the test object. 6, 62 indicates the spectral reflectance of aluminum, 63 indicates the spectral reflectance of copper, and 64 indicates the spectral reflectance of gold. According to FIG. 6, in the wavelength region of 550 nm or less, the reflectance of aluminum is other than that. It can be seen that while the reflectance is high with almost no change in the wavelength, the reflectance of gold sharply decreases.

On the other hand, the electrode portion on the chip is generally formed of an aluminum pattern, and a gold wire is used for the wire used for ball bonding. In this case, the illumination light 52 applied to the electrode unit 51 in FIG.
Is high reflection, but the reflection of the illumination light 53 irradiated on the ball portion 54 is low reflection, and the insulating portion 56 other than the electrode portion on the chip is formed of a material having a low reflectance. As a result, the image captured by the imaging device 31 has a state in which only the electrode portions are brightly raised as shown in FIG. 5B.

Subsequently, the optical adjustment device 6 is controlled by the controller 4
In accordance with the instruction of No. 1, the setting is changed so that light of a wavelength exceeding 550 nm is transmitted.
6 is captured by the imaging device 31, according to the reflection characteristics of FIG. 6, both the electrode portion 51 and the ball portion 54 exhibit high reflectance, whereas the insulating portion 56 has 550n.
Since the reflectance is low even at a wavelength exceeding m, the flat surface on the electrode portion 51 and the ball portion 54 is captured as a bright portion as shown in FIG.

At this time, however, the imaging device 31 is generally 5
The sensitivity is reduced in a wavelength region of 50 nm or less.
Since the emission intensity is reduced in a wavelength region of 50 nm or less, an illumination light having a wavelength exceeding 550 nm is used as the illumination light amount of the light source 11 in order to maintain a good contrast of an image captured by the imaging device 31. There is a need to increase it compared to the case. Therefore, in this apparatus, before capturing an image,
The image illuminance and the variance of the luminance distribution of the image are calculated by the image analyzer 43, and the lamp power supply circuit 45 is controlled so as to reach a preset threshold value, so that the illumination intensity of the light source 11 can be automatically adjusted. I have.

Further, regarding the optical elements constituting the image pickup system, there is a shift in the focal position between the case where illumination light having a wavelength of 550 nm or less is used and the case where illumination light having a wavelength exceeding 550 nm is used due to chromatic aberration. In this device, the wavelength range of the illumination light actually used is limited to 100 nm or less and 450 to 550 in this apparatus.
An imaging system that has been so-called achromatized so as to be used in two sections of a short wavelength range of 600 nm and a long wavelength range of 600 to 700 nm, and that the optical performance at the center wavelength of each wavelength range substantially matches. Used.

Naturally, the use of the function of automatically adjusting the relative distance between the test object 1 and the imaging system for each illumination wavelength region in anticipation of the defocus caused by chromatic aberration is within the scope of the present invention. Not contrary.

FIG. 5 captured by the above procedure
The image shown in FIG. 5A and the image shown in FIG. 5B are respectively sent to the image analyzer 43, and the image shown in FIG. 5A is further extracted, and a combined image of the electrode portion 51 and the ball portion 54 is extracted by subjecting the image of FIG. Further, by subtracting the image of only the electrode portion 51 from the composite image of the electrode portion 51 and the ball portion 54, the ball portion 5
Only four images can be easily extracted.

(Second Embodiment) In the first embodiment, a white light source is used as a light source for illumination. However, in this embodiment, an LED light source is used as a light source for illumination.

In FIG. 2, a red LED and a blue LED having high directivity are regularly arranged in the LED light source 15 so as to converge at one point, and the lamp power supply circuit 45 is controlled by the controller 41 to provide illumination. The selection of the color of the light source and the adjustment of the illumination intensity are performed. The illuminating light is converged on one point, is formed into parallel light, is irradiated on the test object 1 as in the first embodiment, and an image is captured by the imaging device 31.

(Third Embodiment) In this embodiment, a laser light source is used as a light source for illumination.

In FIG. 3, a red laser light source 13 and a blue laser light source 14 are connected in parallel to a laser power supply 48, and illumination light is applied to the test object 1 via half mirrors 21, 22 and 23. It has become.

Further, the beam splitter 24
After separating the wavelength of 50 nm or less from other wavelengths,
Images can be captured at the same time by the imaging devices 31 and 32, respectively, and there is no need to switch the wavelength of illumination light, so that the time required for imaging can be reduced.

Here, in each of the above embodiments, the epi-illumination is described as an example. However, it goes without saying that the same effect can be obtained in dark-field illumination or diffuse illumination. Reference numeral 3 does not limit the arrangement of the optical elements constituting the imaging system.

In the above embodiment, the description is made with particular attention to the image of the ball portion among the wires. However, the same effect can be obtained for all the luminescent spots present on the image of the wire. It is needless to say that the present invention is also effective in calculating the locus of the wire by identifying the bright spot observed on the horizontal portion of the wire other than the portion and the electrode on the chip.

[0037]

As described above, according to the inspection method and apparatus of the present invention, an image can be obtained which allows the electrode pattern portion on the chip to be easily distinguished from the wire portion. Further, even when a light source that emits white illumination light is used, it is possible to capture an image that can easily identify an electrode pattern portion and a wire portion on a chip.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a wire bonding inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a wire bonding inspection device according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a wire bonding inspection apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram showing illumination light applied to a test object.

FIG. 5 is a diagram showing a captured image, (a) showing 550n;
(b) shows a case where illumination light having a wavelength of 550 nm or less is applied.

FIG. 6 is a diagram showing characteristics of illumination light.

FIG. 7 is an explanatory diagram of a conventional bonding wire inspection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test object 2 Inspection stage (stage) 3 Drive stage 5 Aperture device 6 Optical adjustment device 7 Condenser lens 11 Light source 12 Light source 13 Red laser light source 14 Blue laser light source 15 LED light source 21 Half mirror 22 Half mirror 23 Half mirror 24 Beam splitter REFERENCE SIGNS LIST 31 imaging device 32 imaging device 41 controller 42 input device 43 image analysis device 44 imaging device drive circuit 45 lamp power supply circuit 46 actuator drive circuit 47 stage drive circuit 51 electrode unit 52 illumination light 53 illumination light 54 ball unit 55 wire unit 56 insulating unit 61 Spectral reflectance of silver 62 Spectral reflectance of aluminum 63 Spectral reflectance of copper 64 Spectral reflectance of gold

Claims (9)

[Claims] 1. A bonding wire inspection method for inspecting a bonding state based on an image signal, wherein an illumination area has a spectrum having a low reflectance on a wire surface and a high reflectance on an electrode portion in an inspection area. A wire bonding inspection method, wherein an image formed by reflection of the illumination light is analyzed. 2. The wire bonding inspection method according to claim 1, wherein the illumination light has a wavelength of 550 nm or less. 3. An observation image in a wavelength region having a spectrum having a low reflectance on a wire surface and a high reflectance on an electrode portion, and a spectrum having a high reflectance on a wire surface and an electrode portion. 2. The wire bonding inspection method according to claim 1, wherein the electrode part and the wire part are identified by comparing the observation image in the wavelength region having the electrode part. 4. The wire bonding inspection method according to claim 3, wherein, when comparing observation images in a plurality of wavelength regions, the range of each wavelength region is 100 nm or less. 5. A mounting device for mounting a wire-bonded semiconductor chip and a lead frame, an illuminating device for illuminating a region to be inspected, an imaging device for capturing an image of a wire to obtain an image signal, and an image analyzing device. A bonding wire inspection device for inspecting a bonding state based on the image signal, wherein the illumination device has a low reflectance of the inspection region on a wire surface and a high reflectance of an electrode portion. A wire bonding inspection apparatus characterized by irradiating with illumination light having a spectrum. 6. The image analysis apparatus according to claim 1, wherein the inspection area includes an observation image in a wavelength region having a spectrum having a low reflectance on a wire surface and a high reflectance on an electrode portion, and an inspection image on the wire surface and the electrode portion. 6. The wire bonding inspection apparatus according to claim 5, wherein the electrode part and the wire part are identified by comparing an observation image in a wavelength region having a spectrum with a high reflectance. 7. The wire bonding inspection apparatus according to claim 5, wherein a blue LED is used as a light source for generating the illumination light. 8. The illumination device according to claim 5, wherein a white light source is used as the illumination light source, and a blue illumination light is selectively extracted and used by inserting a wavelength filter in an optical path of the illumination light. 7. The wire bonding inspection apparatus according to 6. 9. A white light source is used as an illumination light source, and blue reflected light is selectively extracted and used from an image of an inspection area illuminated by the white light source. The wire bonding inspection apparatus according to the above.