JP2010151479A - Wiring pattern inspecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously perform the detection of the shape of the upper part of a pattern and the detection of the shape of the lower part of the pattern in a pattern inspecting device. <P>SOLUTION: A first illumination means 1a for obliquely illuminating a TAB tape 5 with illumination light from a wiring pattern formed side, a second illumination means 1b for obliquely illuminating the TAB tape with illumination light from the side opposite to the wiring pattern formed side and a third illumination means 1c for illuminating an inspection region with illumination light from the side opposite to the wiring pattern formed side so that the illumination light is incident on the inspection region so as to cross the inspection region at a right angle are provided and the TAB tape is simultaneously illuminated from three directions to take the image of the wiring pattern by an imaging means 11. By this illumination method, the shapes of the upper and lower parts of the wiring pattern can be simultaneously detected by one measurement and such a flaw that the upper part of the wiring pattern is partially lacked can be detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pattern inspection apparatus capable of simultaneously measuring an upper line width and a lower line width of a wiring pattern formed on a light-transmitting substrate such as a TAB (Tape Automated Bonding) tape.

In general, when a wiring pattern (hereinafter also referred to as a pattern) is formed on a substrate by etching, the cross section tends to be trapezoidal with a lower width wider than an upper width. For this reason, if etching is insufficient, even if the upper line width is within the range of non-defective products, a wiring thickness called “root residue” occurs in the lower part, which may cause a short circuit with the adjacent wiring. . Therefore, in the inspection of the wiring pattern, it is important to measure the width of the lower part of the pattern.
As an inspection method for measuring the width of the lower part of the pattern, it is known that the illumination light is transmitted through the substrate on which the pattern is formed (inspection by transmitted illumination) (see, for example, Patent Document 1 and Patent Document 2). ).
Japanese Patent Application Laid-Open No. H10-228688 discloses that the line width at the lower part of the wiring pattern is measured by transmitted illumination to detect whether a short circuit or the like has occurred. FIG. 5 of Patent Document 2 also shows that the line width below the wiring pattern can be measured by transmitted illumination.
JP 2003-303862 A JP 2000-113191 A

With transmitted illumination, the line width at the bottom of the pattern can be measured. However, the upper line width cannot be measured. However, recently, it has become desirable to measure not only the line width at the bottom of the pattern, but also the line width at the top. The reason is as follows.
FIG. 9 shows a cross-sectional shape of the wiring pattern formed on the substrate. As described above, the cross section of the pattern formed by etching has a trapezoidal shape with a lower width wider than an upper portion. That is, as shown in FIG. 9A, in the wiring pattern, the lower width b is a <b with respect to the upper width a, and if the height is h, the cross-sectional area S is S = (a + b) Xh / 2.
However, recently, due to miniaturization of the wiring pattern, the lower line width is within the range of non-defective products, but the upper line width is very narrow, and the cross-sectional shape of the wiring is triangular as shown in FIG. 9B. It may become.
When the cross-sectional shape is triangular, as shown in FIG. 9B, when the width of the lower part of the wiring pattern is b and the height is h, the cross-sectional area S ′ is S ′ = b × h / 2. Even if the widths are the same, the cross-sectional area is smaller than when the cross-section is trapezoidal.
That is, compared with FIG. 9A, the cross-sectional area of FIG. 9B has a smaller area by a × h / 2.

The cross-sectional area of the wiring pattern is designed from the value of current flowing through the pattern. Therefore, in a pattern inspection apparatus, a pattern having a cross-sectional area smaller than an allowable range must be regarded as defective.
However, if only the width of the lower part of the wiring pattern is measured, the size of the cross-sectional area of the pattern cannot be determined. In order to obtain the cross-sectional area, the widths of the upper and lower wirings of the pattern must be measured.
By the way, it is known to use reflected illumination light to detect the line width of the upper part of the wiring pattern.
Therefore, if the pattern to be inspected is irradiated with reflected illumination light to measure the line width at the top of the pattern, and then irradiated with transmitted illumination light to measure the line width at the bottom of the pattern, both of them are measured. The cross-sectional area can be obtained from the measurement result.
However, in this method, two measurements, that is, measurement with reflected illumination light and measurement with transmitted illumination light are performed on one inspection pattern, and the inspection time becomes longer. Therefore, an inspection apparatus capable of simultaneously measuring the line width of the upper part of the pattern and measuring the line width of the lower part is desired.
The present invention has been made in view of the above circumstances, and an object of the present invention is to enable detection of the upper shape of a pattern and detection of the lower shape at the same time in a pattern inspection apparatus. is there.

In the present invention, the above problem is solved as follows.
In a wiring pattern inspection apparatus for determining the quality of the above pattern based on an image obtained by irradiating illumination light to a wiring pattern formed on a light-transmitting substrate, the pattern formed on the light-transmitting substrate is Thus, illumination means for illuminating from three different directions is provided to illuminate simultaneously from three directions.
The first illuminating unit irradiates the illumination light so as to be incident obliquely on the inspection region from the side on which the substrate pattern is formed. The second illuminating means irradiates the illumination light so as to be incident obliquely on the inspection region from the side opposite to the side on which the substrate pattern is formed. The third illuminating unit irradiates the illumination light from the side opposite to the side on which the substrate pattern is formed so as to be incident substantially orthogonal to the inspection region.
By illuminating in this way, it is possible to detect the shape of the upper part and the lower part of the pattern at the same time. For example, the defect is that the shape of the lower part of the wiring pattern is normal but a part of the upper part is missing. Can be detected.
If necessary, the cross-sectional area of the pattern can be calculated based on the upper shape (line width) and lower shape (line width) of the detected pattern. It is compared whether or not the calculated cross-sectional area is within the allowable range, and if it is out of the allowable range, the pattern is determined to be defective.

  In the present invention, the shape of the upper part and the shape of the lower part of the pattern can be detected simultaneously with a single measurement for the inspection pattern. Therefore, it is possible to detect a wiring pattern defect or the like without lengthening the inspection time.

FIG. 1 is a block diagram of a wiring pattern inspection apparatus according to an embodiment of the present invention. In the following examples, the case where the substrate is a film-like workpiece such as TAB tape or COF (Chip On Film) will be described. However, the present invention is applicable to pattern inspection of other substrates as long as it is light transmissive. can do.
As shown in the figure, the pattern inspection apparatus according to the present embodiment illuminates the tape transport mechanism 20 including the delivery reel 21 and the take-up reel 22 that transport the TAB tape 5, and the TAB tape 5 delivered from the delivery reel 21. An inspection unit 1 that irradiates light and images the inspection pattern 6, a scanning unit 2 that scans the inspection unit 1 on the inspection pattern 6 of the TAB tape, and a marker unit 3 that marks a defective pattern are provided.
In the marker unit 3, a pattern such as color coating is applied so that a pattern determined to be defective can be punched with a punch or the portion can be immediately confirmed visually as a defective product.

Further, the pattern inspection apparatus includes a control unit 4. The control unit 4 controls operations of the inspection unit 1, the marker unit 3, and the tape transport mechanism 20, and detects pattern defects based on the upper and lower shapes of the detected pattern. It is also possible to determine the quality of the pattern by calculating the cross-sectional area based on the upper and lower line widths.
The inspection unit 1 includes a first illumination unit 1a that irradiates illumination light obliquely from the side on which the pattern is formed to the TAB tape 5, and illumination light obliquely from the side opposite to the side on which the pattern is formed. A second illuminating means 1b for irradiating illumination light, a third illuminating means 1c for irradiating illumination light so as to enter (substantially) perpendicularly to the inspection region from the side opposite to the side on which the pattern is formed, The imaging unit 11 is provided on the same side as the first illumination unit 1a and directly above the inspection area. The light sources of the first, second, and third illumination means 1a, 1b, and 1c use LEDs in this embodiment, but may use halogen lamps. When a halogen lamp is used as a light source, the light from the lamp is guided by a light guide fiber, and the incident angle of the light emitted from the fiber to the inspection region is set to a desired angle.

The imaging means 11 is, for example, a CCD line sensor or an area sensor having light receiving sensitivity at the wavelength of the illumination light.
Further, a projection lens (not shown) is provided on the light incident side of the image pickup means for enlarging and projecting an area to be inspected of the TAB tape 5. This lens is a combination of a plurality of lenses housed in a lens barrel.
The control unit 4 turns on and off the illumination light of the first, second, and third illumination units 1a, 1b, and 1c, captures the imaging unit 11, moves the inspection unit 1 by the scanning unit 2, and moves the TAB tape 5. Control the transport.
Moreover, the control part 4 determines the quality of a pattern based on the shape of the upper part and lower part of the detected pattern. Further, the cross-sectional area of the pattern may be calculated based on the upper and lower line widths, and the quality of the pattern may be determined from this cross-sectional area.
For this reason, the upper line width of the pattern, the allowable range of the lower line width, the allowable range of the cross-sectional area of the wiring pattern, and the like are input in advance to the control unit.

2 and 3 are enlarged views of the inspection unit 1. 2 is a perspective view of the inspection portion, and FIG. 3 is a cross-sectional view of the TAB tape 5 along the longitudinal direction.
As shown in FIG. 2, the first illuminating means 1a and the second illuminating means 1b have the same incident angle from all directions incident on the inspection region, and the intensity of the light incident from each direction is as follows. A plurality of LEDs are arranged in an annular shape so that they can be illuminated in the same manner. For example, as shown in FIG. 3, a prism sheet 10b is provided on the light emitting side of the LEDs 10a. A diffusion plate 10c is attached to the light emitting side.
The 3rd illumination means 1c arrange | positions LED10a along a linear test | inspection area | region, and attached the diffuser plate 10c to the light emission side.

FIG. 4 shows a specific configuration example of the first illuminating means 1a and the second illuminating means 1b formed in the annular shape. The figure (a) shows the prism sheet cut out in the fan shape, and the figure (b) shows the A direction of the figure (a) when the illumination means is constituted by using the prism sheet shown in the figure (a). (C) shows the light emission direction when viewed from the direction B. When the illumination means is configured by using the prism sheet shown in FIG. The light emission direction is shown.
The prism sheet 10b is formed by arranging a large number of triangular prisms on one side of a transparent sheet so that the prisms are parallel to each other. As shown in FIG. Cut out in a fan shape so that it faces the tangential direction of the arc of the mold. Then, the prism sheets are arranged in an annular shape and arranged on the light emitting side of the LED 10a attached on the support member 12. A diffusing plate 10c is further attached to the first illuminating means 1a and the second illuminating means 1b.
The light in which the principal rays emitted from the LED 10a are incident on the prism sheet 10b and refracted by the prism when viewed from the direction A in FIG. 10 (a) to maintain the parallel state as shown in FIG. The light enters the imaging region R at a constant angle. Further, when viewed from the B direction in FIG. 5A, the light is irradiated downward without being refracted by the prism, as shown in FIG.

  Returning to FIG. 1, the imaging unit 11 images the examination area illuminated simultaneously by the first, second, and third illumination units 1 a, 1 b, and 1 c. The CCD used for the imaging means 11 is a line sensor, and the imaging area is an elongated area along the CCD line sensor. The imaging means 11 moves in the width direction of the TAB tape 5 integrally with the first, second, and third illumination means 1a, 1b, and 1c, and images the entire inspection area.

Next, an experimental result of examining what kind of illumination should be performed in order to be able to simultaneously measure the line width of the upper part and the lower part of the pattern is shown.
FIG. 5 shows a pattern of a sample to be inspected. FIG. 5A is a view of the pattern as viewed from above, and FIG. 5B is a cross-sectional view taken along the line AA in FIG. is there. The figure schematically shows the result of observing an actual pattern with a laser microscope.
As shown in FIGS. 4A and 4B, the sample pattern has a lower width of about 20 μm, an upper width of 14 μm, a slope width of 3 μm, and a pattern height of about 7-8 μm. As shown in FIG. 4, the upper part of the wiring is 83% less than the non-defective product (the lower part is also missing, but the upper part is larger). Therefore, when this pattern is inspected by the pattern inspection apparatus, it is ideal that it is possible to detect that there is “83% chipping” in the upper part as well as the line width in the lower part.
Note that the percent missing is calculated from the brightness of each pixel of the missing portion in the captured pattern image.

In the experiment, (a) the first illuminating means 1a that irradiates illumination light obliquely from the side on which the pattern is formed with respect to the TAB tape, and (b) obliquely from the side opposite to the side on which the pattern is formed. A second illuminating means 1b for irradiating the illumination light with (c) a third irradiating illumination light so as to be incident (substantially) perpendicularly to the inspection region from the side opposite to the pattern-formed side; Using the illuminating means 1c, the image sensor 11 takes a sample pattern image and compares the three types of illuminations (a), (b), and (c) individually and in combination. did.
(1) When not using the 3rd illumination means 1c (transmission orthogonal).
Illumination of only the first illumination means 1a (reflection oblique), illumination of only the second illumination means 1b (transmission oblique), simultaneous illumination of the first illumination means 1a and the second illumination means 1b (reflection oblique + transmission oblique) ), The image of the pattern of the sample was taken by the imaging means.
In either case, it was found that the image was dark and the contrast was poor, it was difficult to check not only the line width at the bottom of the pattern but also the line width at the top, and it was difficult to accurately measure the line width of the pattern.

(2) When the sample pattern is illuminated only by the third illumination means 1c (transmission orthogonal).
FIG. 6A is a diagram schematically showing an image when the sample pattern is illuminated only by the third illumination means 1c (transmission orthogonal). As described above, when the third illumination unit 1c is used, the portion of the substrate without the wiring pattern transmits the illumination light, and an image with good contrast is obtained. The line width at the bottom of the pattern can be detected and measured.
However, the line width at the top of the pattern cannot be measured only with the third illumination means 1c. In FIG. 6A, the ratio of chipping at the top of the pattern detected is 47%.
As described above, the actual chip ratio is 83%, and the detected chip size is about half smaller than the actual chip. This means that the line width at the top of the pattern is not correctly detected.

(3) When the first illumination means 1a (reflection oblique) or the second illumination means 1b (transmission oblique) is added to the third illumination means 1c (transmission orthogonal) for illumination.
FIG. 6B shows the case where the first illumination means 1a (reflection oblique) is added to the third illumination means 1c (transmission orthogonal), and FIG. 6C shows the third illumination means 1c (transmission). This is a case where the second illumination means 1b (transparent oblique) is added to (perpendicular).
As shown in FIGS. 6B and 6C, if the illumination by the second illumination means 1b or the third illumination means 1c is added to the illumination by the third illumination means 1c (transmission orthogonal), the lower line The width and upper line width can be detected.
However, in the case of FIG. 6B, the size of the chip at the top of the pattern is detected as 64%, and in the case of FIG. 6C, the size of the chip at the top of the pattern is detected as 55%. In either case, the size of the chip is closer to the correct value (83%) than in the case of only the third illumination means 1c (transmission orthogonal) in FIG. 6A, but it is sufficient. Absent.

(4) When the first illumination means 1a (reflection oblique) and the second illumination means 1b (transmission oblique) are added to the third illumination means 1c (transmission orthogonal) and illuminated.
FIG. 6D shows a case where the third illumination unit 1c (transmission orthogonal), the first illumination unit 1a (reflection oblique), and the second illumination unit 1b (transmission oblique) are all illuminated simultaneously. The size of the detected chip is 73%, and it can be detected at a value closest to the actual chip ratio. Also, the lower and upper line widths could be detected more clearly than in the case of (3) above.
As will be described later, in the case of illumination with only the third illumination means 1c (transmission orthogonal), both the side surface and the upper surface of the pattern are displayed black (dark), but the first illumination means 1a (reflection) When illumination light from (oblique) or illumination light from the second illumination means 1b (transmission oblique) is added, the side surface of the pattern becomes slightly brighter. Thereby, the upper part of the pattern and the side surface of the pattern can be distinguished, and the line width of the upper part can be detected.
FIG. 6E schematically shows an enlarged image of the missing part of FIG. 6D. Here, the lower width of the wiring pattern is 20 μm, the upper width is 16 μm, and the side width is 2 μm. As shown in the figure, the side surface portion of the pattern is slightly brighter than the upper portion of the pattern, and the width of the lower portion of the pattern can be obtained from this.
FIGS. 6A to 6E schematically show images. The image captured by the imaging unit 1 is subjected to image processing by the control unit 4 and based on the luminance of each pixel. By calculating the size of the chip, the size of the chip can be measured.

As described above, by simultaneously performing the first, second, and third illuminations, the shape of the upper part and the lower part of the pattern can be detected relatively clearly in one measurement. Pattern defects can be detected.
In addition, the cross-sectional area can be obtained by simultaneously detecting the lower line width and the upper line width of the pattern.
In the case of FIG. 6D, when the line width is calculated based on the luminance of each pixel of the captured image, the lower line width is about 20 μm, and the upper line width of the part where the chip is generated is about 4 μm. It was.
Therefore, the cross-sectional area of the portion where the chip is generated is (20 μm + 4 μm) × pattern height × 1/2. Since the height of the pattern cannot be obtained from the image of FIG. 6, a design value is substituted.
The lower limit value of the cross-sectional area allowed from the current value flowing in the pattern is input in advance to the control unit 4 of the apparatus. The control unit 4 compares the cross-sectional area of the missing part of the pattern obtained by the above calculation with the lower limit value of the cross-sectional area, and determines that the pattern is defective if it is smaller than the lower limit value.

The reason why the lower line width and the upper line width of the pattern can be detected simultaneously by performing the first, second, and third illuminations simultaneously is considered as follows.
This will be described with reference to FIG.
The line width at the bottom of the pattern is detected by the illumination light (3) from the third illumination means 1c (transmission orthogonal).
In addition, the illumination light (1) from the first illumination means 1a (reflective oblique) and the illumination light (2) from the second illumination means 1b (transparent oblique) are incident. In addition, although the illumination light (1) from the 1st illumination means 1a and the illumination light (2) from the 2nd illumination means 1b are shown in FIG. 7 so that it may inject from right and left in a figure, Actually, light is incident on the pattern from all directions of 360 °.

The actual side surface of the pattern is not a smooth surface, but has a large number of fine irregularities. Therefore, the illumination light (1) from the first illumination means 1a and the illumination light (2) from the second illumination means 1b are irregularly reflected on the side surface of this pattern, and a part of them is incident on the imaging means 11. . Thereby, the side of the pattern is imaged slightly brighter than the upper part of the pattern.
That is, in the case of illumination only with the third illumination means 1c (transmission orthogonal), both the side surface and the upper surface of the pattern are displayed black (dark), but the illumination from the first illumination means 1a (reflection oblique) When light (i) and illumination light (ii) from the second illumination means 1b (transmission oblique) are added, the side surface of the pattern becomes slightly brighter, and the upper part of the pattern and the side surface of the pattern can be distinguished. Therefore, the shape of the upper part of the pattern becomes clear and the line width can be detected.
As described above, the lower shape and the upper shape of the pattern can be detected simultaneously.

FIG. 8 is a diagram showing an experimental result for obtaining an optimum angle of the illumination light of the first illumination unit 1a and the second illumination unit 1b.
The illumination unit 30 that illuminates the TAB tape 5 is moved from the side opposite to the side on which the pattern is formed to the side on which the pattern is formed, and a change in brightness on the side surface of the sample pattern is captured. It was measured by.
As shown in FIG. 8A, the illuminating means 30 has a position where the illumination light is incident perpendicularly from the side opposite to the side where the pattern is formed (that is, the position of the third illuminating means) at 0 °. And measured by moving to a position of 160 ° toward the side where the pattern is formed.
In this experiment, it is difficult to change the incident angle of the illumination light emitted from the annular illumination means. Therefore, the LEDs are placed on both sides in the longitudinal direction of the inspection region, and the LEDs are moved as shown in FIG. Thus, the incident angle of the illumination light on the TAB tape was changed. Here, as the illumination means 30, LEDs in which chips are arranged in one row were used, and a current of 70 mA was passed.
FIG. 8B shows the result. The horizontal axis represents the angle (°) of the illumination means, and the vertical axis represents the brightness (arbitrary unit) of the side surface of the pattern. As shown in the figure, the side surface of the pattern becomes bright when illuminated in a range of about 30 ° to 60 ° and illuminated at 120 ° or more. The brighter the side of the pattern, the clearer the boundary with the upper part of the pattern, so it is suitable as the position of the illumination means.
Therefore, the 1st illumination means 1a is set so that the incident angle to the test | inspection area | region of illumination light may become the range of 120 degrees-160 degrees. Moreover, the 2nd illumination means 1b is set so that the incident angle to the test | inspection area | region of illumination light may be in the range of 30 degrees-60 degrees.

It is a block diagram of the wiring pattern inspection apparatus of the Example of this invention. It is the perspective view which expanded the test | inspection part of FIG. It is sectional drawing which cut the test | inspection part of FIG. 1 along the longitudinal direction of a TAB tape. It is a figure which shows the specific structural example of the 1st illumination means 1a formed in the annular | circular shape, and the 2nd illumination means 1b. It is a figure which shows typically the pattern of the sample which test | inspects. It is the figure which showed typically the image obtained when the combination of an illumination means is changed and the sample of FIG. 5 is imaged. It is a figure explaining the reason why the line width of the lower part of a pattern and the line width of an upper part can be detected simultaneously by performing 1st, 2nd, and 3rd illumination simultaneously. It is a figure which shows the experimental result for calculating | requiring the optimal angle of the illumination light of the 1st illumination means 1a and the 2nd illumination means 1b. It is a figure which shows the cross-sectional shape of the wiring pattern formed on the board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test | inspection part 1a 1st illumination means 1b 2nd illumination means 1c 3rd illumination means 2 Scanning means 3 Marker part 4 Control part 5 TAB tape 6 Test pattern 10a LED
10b Prism sheet 10c Diffusion plate 11 Imaging means 12 Support member 20 Tape transport mechanism 21 Delivery reel 22 Take-up reel 30 Illumination means

Claims (1)

In a wiring pattern inspection apparatus for determining the quality of the above pattern based on an image captured by irradiating illumination light to a wiring pattern formed on a light-transmitting substrate,
A first illuminating means for irradiating the illumination light so as to be incident obliquely on the inspection region from the side of the substrate on which the wiring pattern is formed;
A second illuminating means for irradiating illumination light so as to be obliquely incident on the inspection region from the side opposite to the side on which the wiring pattern of the substrate is formed on the light transmissive substrate;
A third illuminating means for irradiating the illumination light so as to be incident perpendicularly to the inspection region from the side opposite to the side on which the wiring pattern of the substrate is formed;
Imaging means provided on the side of the board on which the wiring pattern is formed;
Control means for controlling illumination of the first illumination means, the second illumination means, and the third illumination means,
The control means simultaneously illuminates the substrate with the first, second, and third illumination means,
The wiring pattern inspection apparatus characterized in that the imaging means images a wiring pattern illuminated simultaneously by the first, second and third illumination means.

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