JP2002139440A - Illuminator for pattern inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminator for pattern inspection which can obtain reflected light having sufficient luminance even at a fine pattern section when a pattern is inspected for propriety. SOLUTION: A pattern inspection device 10 is provided with edge section irradiating ends 15 and 15 for vertical pattern which irradiate the edge section of a vertical pattern 22 with light and an edge section irradiating end 16 for horizontal pattern which irradiates the edge section of a horizontal pattern 23 with light in addition to a top section irradiating end 14 which irradiates the upper surface of the top section of a pattern formed on the surface of a wiring board 17. Consequently, even in such a case that the top section of the pattern becomes extremely narrower in width than a designed value in a fine pattern portion or is not left, the edge sections are irradiated with light and reflected light rays from the edge sections are received by means of a one-dimensional CCD element 11. Therefore, reflected light rays having sufficient luminance are received as a whole by means of the CCD element 11 even when the reflected light from the top section has insufficient luminance, because the reflected light rays have sufficient luminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection lighting device used for inspecting the quality of a fine pattern formed on a surface of a printed wiring board, an IC package, or the like. More specifically, the present invention relates to a pattern inspection lighting device that can accurately image a pattern even in a fine pattern portion during a pass / fail inspection.

[0002]

2. Description of the Related Art Printed wiring boards, IC packages, etc.
With respect to a fine pattern formed on the surface, an appearance inspection using image processing is performed to inspect the quality of the pattern formation. Inspection of the quality of this pattern usually utilizes the fact that the reflectance of light is different between the pattern (copper plating, etc.) and the place where it is not. This is done by detecting. That is, image processing is performed on the information detected by the light receiving element, the pattern is visually recognized, and a defect is detected by comparing the pattern with a reference pattern.

[0003] This fine pattern is usually formed by etching. Therefore, as shown in FIG. 7, the cross-sectional shape of the pattern becomes trapezoidal. That is, the width of the flat portion formed on the top portion is slightly smaller than the width of the bottom portion. In recent years, with the miniaturization of electronic devices, finer patterns have been developed. For this reason,
In the fine pattern portion, as shown in FIG. 8, the flat portion formed on the top portion of the pattern becomes extremely thinner than the designed value (a flat portion remains slightly), or as shown in FIG. There is a case where a flat portion is not formed on the substrate. And even in such a case, it is necessary to perform the pass / fail inspection of the pattern with high accuracy.

[0004]

However, in the conventional illumination device for pattern inspection, there is a problem that the brightness of the reflected light from the pattern is insufficient in the fine pattern portion. For this reason, the quality inspection of the pattern could not be accurately performed. That is, even if the fine pattern portion is electrically connected, the inspection image may appear in a shape such as a broken line or a broken line as shown in FIG. This is because if the top portion of the pattern has the shape shown in FIGS. 8 and 9, the light applied to the top portion will be irregularly reflected, and the brightness of the regular reflection light at the top portion will be insufficient. is there. In particular, when the flat portion does not remain at the top of the pattern, the lack of luminance becomes remarkable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a pattern inspection method capable of obtaining reflected light having a sufficient luminance even in a fine pattern portion at the time of pattern quality inspection. An object of the present invention is to provide a lighting device for lighting.

[0006]

According to the illumination device for pattern inspection according to the present invention which has been made to solve the above-mentioned problems, a pattern formed on an inspection surface of an object to be inspected is irradiated with light. In a pattern inspection illuminating device used for detecting reflected light with a light receiving element and inspecting the quality of the pattern based on the detection information, a top portion irradiating means for irradiating light to an upper surface of the pattern, and a longitudinal portion of the light receiving element A first method of irradiating light to an edge portion of a pattern formed in a direction
Edge part irradiating means, a second edge part irradiating means for irradiating light to an edge part of a pattern formed in a direction intersecting with the longitudinal direction of the light receiving element, and a light source for supplying light to each irradiating means, It is characterized by having.

Here, in this specification, the “top portion”
Means the upper part of the pattern, and means a flat part when a flat part is formed on the top part (see FIGS. 7 and 8), and a top part when no flat part is formed (see FIGS. 7 and 8). 9). Further, the “edge portion” means a boundary portion between an upper portion and a side surface of the pattern. For this reason, the edge portions are present at both ends in one pattern (see FIGS. 8 and 9). In an actual pattern, both edges of the top portion of the pattern are sagged, so that the edge portion is often slightly rounded. The reason why the edge is irradiated with light is to prevent the reflected light from the pattern from being separated and incident on the light receiving element. That is, when light is irradiated not on the edge but on the side surface of the pattern, the reflected light from the pattern is separated and enters the light receiving element, so that one or two patterns exist in the inspection image. It is because it is reflected in.

In this illumination device for pattern inspection, light is supplied from a light source to each of the irradiating means, that is, the top part irradiating means, the first edge part irradiating means, and the second edge part irradiating means. Here, a light source may be individually provided for each irradiation unit to supply light to each irradiation unit from each light source, or one light source may be provided to supply light to each irradiation unit from the light source. You may. As the light source, a metal halide light source,
Halogen light sources, LED light sources and the like can be used.

Then, light is irradiated on the top portion of the pattern by the top portion irradiation means. Further, the first edge irradiating means irradiates the edge of the pattern formed in the longitudinal direction of the light receiving element with light. Further, the second edge irradiating means irradiates the edge of the pattern formed in a direction intersecting the longitudinal direction of the light receiving element with light.

Specifically, the top irradiating means is arranged so that its optical axis and the normal to the inspection surface of the object to be inspected form a predetermined angle, and is arranged in the top of the pattern and in the longitudinal direction of the light receiving element. The first edge irradiating unit irradiates light to one edge of the formed pattern, and irradiates the second edge of the pattern formed in the longitudinal direction of the light receiving element with light. The edge irradiating means may irradiate light to both edge portions of the pattern formed in a direction intersecting the longitudinal direction of the light receiving element.
Here, the “optical axis” means the center of the angular distribution of the light irradiated from the irradiation unit. The predetermined angle is
It may be about 5 to 30 degrees.

The first edge irradiating means may irradiate light to both edge portions of a pattern formed in the longitudinal direction of the light receiving element. That is,
A first edge irradiating means may be separately provided so as to irradiate light from behind the top irradiating means.

Alternatively, the top irradiating means irradiates light perpendicularly to the inspection surface of the object to be inspected via a half mirror, and the first edge irradiating means includes a pattern formed in a longitudinal direction of the light receiving element. And the second edge irradiating means may irradiate both edges of the pattern formed in a direction intersecting the longitudinal direction of the light receiving element with light.

As described above, in the illumination device, light is emitted not only to the top portion of the pattern but also to the edge portion of the pattern. For this reason, even when the flat portion at the top of the pattern in the fine pattern portion is extremely thinner than the design value or the flat portion does not remain at the top portion, light is irradiated to the edge portion. The reflected light is incident on the light receiving element. As a result, even if the brightness of the reflected light from the top portion of the pattern is insufficient, the reflected light from the edge portion also enters the light receiving element, so that the reflected light having sufficient luminance enters the light receiving element as a whole. Will do. Therefore, when the bottom portion remains in the fine pattern portion and conduction is established, the pattern can be inspected with high accuracy without a disconnection or a missing line in the inspection image.

Here, in addition to a pattern formed in the longitudinal direction of the light receiving element and a pattern formed in a direction intersecting with the pattern, an oblique pattern formed in other directions exists on the surface of the test object. May be. With respect to this oblique pattern, the top portion is irradiated with light by the top portion irradiation means, and the first and second edges are irradiated on the edge portion.
Light is irradiated by the edge irradiating means. At this time, the intensity of light reflected from the edge portion due to irradiation from the first edge portion irradiation means is slightly weak. Similarly, the intensity of light reflected from the edge portion due to irradiation from the second edge portion irradiation means is slightly low. However, as the reflected light from the edge portion, the respective reflected light from the edge portion due to the irradiation from the first and second edge portion irradiation means is simultaneously incident on the light receiving element. Therefore, the reflected light incident on the light receiving element has sufficient luminance. Therefore, even when an oblique pattern is formed in the fine pattern portion, the pattern does not have a broken or missing shape in the inspection image, and a highly accurate pattern inspection can be performed.

It should be noted that, instead of separately providing the first and second edge portion irradiation means, one ring-shaped irradiation means is provided.
The edge of the pattern may be irradiated. By providing such ring-shaped irradiation means, light can be efficiently irradiated even to oblique patterns. Further, the size in the width direction of the second edge portion irradiation means may be smaller than the size in the width direction of the first edge portion irradiation means. The first edge irradiating means needs to irradiate the pattern with the light corresponding to the length of the light receiving element in the longitudinal direction, while the second edge irradiating means applies the light corresponding to at least one line width of the light receiving element to the pattern. This is because irradiation may be performed with respect to.

In the illuminating device for pattern inspection according to the present invention, the first and second edge irradiating means may be arranged such that the angle between each optical axis and the inspection surface of the inspection object is 5 to 5 respectively.
It is preferable that they are arranged so as to be within a range of 30 degrees. This is because if the first and second edge irradiating means are arranged at such an angle, light is likely to be reflected at the edge of the pattern. In particular, it is desirable to arrange at an angle of about 10 degrees. This is because, if it is arranged at about 10 degrees, light is most easily reflected at the edge of the pattern.

In the illumination device for pattern inspection according to the present invention, it is preferable that the first and second edge portion irradiating means include a cylindrical lens at a tip thereof.

When light is irradiated from the first and second edge portion irradiation means at a low angle (30 degrees or less) with respect to the inspection surface of the object to be inspected, not a small amount of light reflected at a portion where a pattern is not formed. Light enters the light receiving element. Also, the first
And since the light emitted from the second edge portion irradiation means has an angular distribution, even if the irradiation angle of the first and second edge portion irradiation means with respect to the inspection surface is set to a predetermined angle,
Light having an angle different from the set angle is also emitted. And there are fine irregularities in the part where the pattern is not formed,
The light emitted from the first and second edge irradiating means includes a large amount of light having an angle that is easily reflected by these irregularities. Therefore, the light reflected from the portion where the pattern is not formed is also detected by the light receiving element. As a result, it becomes difficult to distinguish the pattern portion from the non-pattern portion in the inspection image.

Therefore, the light irradiated from the first and second edge irradiating means is condensed by a cylindrical lens so as to be parallel light having a constant width parallel to the object to be inspected. As described above, by making the light emitted from the first and second edge portion irradiation means parallel light, it is possible to prevent reflection from a portion where a pattern is not formed. This makes it possible to accurately distinguish between the pattern portion and the portion that is not. Therefore, the quality inspection of the pattern can be performed with high accuracy. Note that it is preferable to mount a cylindrical lens even when a ring-shaped irradiation unit is used.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a lighting device for pattern inspection according to the present invention. This embodiment is a pattern inspection apparatus to which the present invention is applied.

First, a schematic configuration of a pattern inspection apparatus to which the present invention is applied is shown in FIG. The pattern inspection apparatus 10
A CCD line sensor camera 12 having a three-dimensional CCD element 11, a lens 13, a top irradiation end 14, two vertical pattern edge irradiation ends 15, 15, a horizontal pattern edge irradiation end 16, and an inspection object. A table 18 on which the wiring board 17 is installed and a feed mechanism 19 for moving the table 18 in the direction A in FIG. 1 are provided. Each irradiation end 14 ~
Reference numeral 16 is connected to each of the light sources 24-26, which are light sources, via cables. In the present embodiment,
A halogen lamp is used for the light sources 24 and 26, and a metal halide lamp is used for the light source 25.

The irradiation ends 15 and 15 of the vertical pattern edge portion are
Each of them has a horizontally long rectangular parallelepiped shape, and is arranged opposite to a substantially symmetrical position with respect to a center line of the table 18 drawn in the direction A in FIG. In addition, as shown in FIG.
Is set so that the irradiation angle with respect to the angle is about 10 degrees. This is because such an irradiation angle most easily reflects light at the edge of the vertical pattern 22. Cylindrical lenses 20, 20 are attached to the ends of the irradiation ends 15, 15, respectively, of the vertical pattern edge portions. The reason why the cylindrical lens 20 is attached is to prevent diffusion of light emitted from the vertical pattern edge irradiation end 15 and to prevent reflection of light from a portion of the wiring board 17 where the pattern is not formed. As a result, in the wiring board 17, a portion where a pattern is formed and a portion where the pattern is not formed can be accurately distinguished, and a pass / fail inspection of the pattern can be accurately performed.

The irradiation end 15 of the vertical pattern edge portion is
Light is applied from the side to the line-shaped elongated field of view of the one-dimensional CCD element 11. Therefore, it is necessary to irradiate the vertical pattern edge portion irradiation end 15 with light in a plane. If the degree of condensing of the cylindrical lens 20 is too strong, the light amount distribution in the field of view of the one-dimensional CCD element 11 is made uniform. It becomes difficult. Therefore, the light condensing degree of the cylindrical lens 20 depends on the one-dimensional CCD element 11.
It is necessary to consider the balance between the size of the field of view and the work distance of the irradiation end 15 of the vertical pattern edge portion.

With such a configuration, the vertical pattern edge irradiating ends 15, 15 are condensed by the cylindrical lenses 20, 20 to irradiate the light emitted from the leading ends thereof, and the edge of the vertical pattern 22 formed on the wiring board 17 is formed. A parallel light is radiated around the portion. The irradiation range at this time is slightly larger than the field of view (detection range) through the lens 13 of the one-dimensional CCD element 11. That is, the irradiation ends 15 and 15 of the vertical pattern edge portion are connected to the one-dimensional CCD element 11.
Can be uniformly illuminated.

The horizontal pattern edge irradiating end 16 has a horizontally long rectangular parallelepiped shape similarly to the vertical pattern edge irradiating end. As shown in FIG. 3, the irradiation angle with respect to the table 18 is about 10 degrees. It is installed in. This is because such an irradiation angle most easily reflects light at the edge of the horizontal pattern 23. A cylindrical lens 21 is attached to the tip of the irradiation end 16 of the horizontal pattern edge. The reason why the cylindrical lens 21 is attached is the same as in the case of the irradiation end 15 of the vertical pattern edge portion.

The irradiation end 16 of the horizontal pattern edge portion is
Light is emitted from the back surface (in parallel) to the line-shaped elongated field of view of the one-dimensional CCD element 11. Therefore, the irradiation end 16 of the horizontal pattern edge portion needs to irradiate light linearly along the field of view of the one-dimensional CCD element 11. Therefore, even if the degree of light collection by the cylindrical lens 21 is strong, it is easy to make the light amount distribution in the field of view of the one-dimensional CCD element 11 uniform. Therefore, as the cylindrical lens 21, a lens having a certain degree of light collection or more may be used.

With such a configuration, the horizontal pattern edge irradiating end 16 condenses the light radiated from the tip thereof by the cylindrical lens 21 so as to center on the edge of the horizontal pattern 23 formed on the wiring board 17. It is designed to emit parallel light. The irradiation range at this time is slightly larger than the field of view (detection range) through the lens 13 of the one-dimensional CCD element 11. That is, the irradiation end 16 of the horizontal pattern edge portion can irradiate the field of view of the one-dimensional CCD element 11 uniformly.

Here, the irradiation range required for the vertical pattern edge irradiation end 15 and the horizontal pattern edge irradiation end 16 is different. That is, the irradiation end 15 of the vertical pattern edge portion needs to uniformly irradiate the light corresponding to the length in the longitudinal direction of the one-dimensional CCD element 11, whereas the irradiation end 16 of the horizontal pattern edge portion has the one-dimensional CCD element 11. It is sufficient to irradiate light of one line width of the above. Therefore, the size in the width direction of the irradiation edge 15 of the vertical pattern edge portion can be made smaller than the size of the irradiation end 16 in the width direction of the horizontal pattern edge portion.

The top irradiation end 14 has a horizontally long rectangular parallelepiped shape similarly to the edge irradiation end. As shown in FIG. 3, the top portion irradiation end 14 is
7 is inclined at an angle θ with respect to a normal H lowered to 7. For this reason, the lens 13 and the one-dimensional CCD element 11 are also arranged at an angle θ so that the one-dimensional CCD element 11 can receive the regular reflection light of the light emitted from the top part irradiation end 14. In this embodiment, θ =
It is set to 11.5 °. As described above, since the top portion irradiation end 14 is installed at an angle, not only the top surface of the pattern top portion, but also the edge portion of the pattern (the side to which light is not irradiated by the horizontal pattern edge portion irradiation end 16). It is designed to emit light. For this reason, in the present embodiment, unlike the vertical pattern edge irradiation end 15, only one horizontal pattern edge irradiation end 16 is provided. However, the horizontal pattern edge portion irradiation end 16
Of course, two may be installed.

An inspection method in the pattern inspection apparatus 10 configured as described above will be briefly described. First,
A wiring board 17 to be inspected is set at a predetermined position on a table 18. When the wiring board 17 is set on the table 18, light is applied to the pattern formed on the wiring board 17 from each of the top irradiation end 14, the vertical pattern edge irradiation ends 15, 15, and the horizontal pattern irradiation end 16. Is irradiated. Then, in this state, the table 18 is moved by the feed mechanism 19, so that the wiring board 17 is scanned, and reflected light from the pattern is received by the one-dimensional CCD element 11. Then, image processing is performed by the CCD line sensor camera 12 based on the detection data from the one-dimensional CCD element 11, and a binarized image relating to the pattern on the wiring board 17, that is, an inspection image is obtained. Then, the quality of the pattern formation is determined by comparing the obtained inspection image with the reference data.

Here, the irradiation end 15 of the vertical pattern edge portion,
In order to examine the effect of providing the horizontal pattern edge irradiation end 16, the fine pattern portion (between two lands) shown in FIG. Part)
An imaging test of a wiring pattern having the following was performed. FIG. 5 shows the imaging result (binary image) at that time. As is clear from FIG. 5, the binarized image in the fine pattern portion does not have any shape such as disconnection or missing line, and the pattern shape is accurately captured. Therefore, it can be understood that the fine pattern portion can be accurately imaged by the pattern inspection apparatus 10 even when the luminance of the reflected light with respect to the irradiation light from the top irradiation end 14 is insufficient. Therefore, by using the pattern inspection apparatus 10 to which the present invention is applied, even if the pattern has a fine pattern portion, the quality of the pattern can be inspected with high accuracy.

As described in detail above, the pattern inspecting apparatus 10 according to the present embodiment has a pattern irradiation apparatus in which a pattern formed on the surface of the wiring board 17 is irradiated with light on the top of the top of the top, in addition to the top irradiation end 14. The vertical pattern edge irradiation ends 15 and 15 for irradiating the edge of the vertical pattern 22 with light, and the horizontal pattern edge irradiation end 16 for irradiating the edge of the horizontal pattern 23 with light are provided. Therefore, even when the top portion is extremely thinner than the design value in the fine pattern portion or the top portion does not remain, the edge portion is irradiated with light, and the reflected light is reflected on the one-dimensional CCD. The light is received by the element 11. For this reason, even if the brightness of the reflected light from the top portion of the pattern is insufficient, the reflected light from the edge portion is also received by the one-dimensional CCD element 11, so that the reflected light having sufficient brightness as a whole is obtained. The light is received by the one-dimensional CCD element 11. Therefore, when the bottom portion remains in the fine pattern portion and conduction is established, the pattern in the inspection image does not have a broken or missing shape. Therefore, an accurate pattern inspection can be performed.

The present embodiment is merely an example, and does not limit the present invention. Therefore, of course, the present invention provides various improvements without departing from the gist thereof.
Deformation is possible. For example, as shown in FIG. 6, the irradiation light from the irradiation end of the top portion may be vertically incident on the upper surface of the pattern top portion via the half mirror 30. In this case, it is necessary to newly install the irradiation end 16a of the horizontal pattern edge portion, and the installation may be performed at a position facing the irradiation end 16 of the horizontal pattern edge portion.
Further, although the one-dimensional CCD element 11 is used as the light receiving element, a two-dimensional CCD element can of course be used.
Further, although a halogen light source is used as a light source, for example, a metal halide light source or an LED light source may be used. Also, in the above character embodiment,
Although the case where the present invention is applied to the wiring board pattern inspection apparatus has been described, the present invention is not limited to the wiring board inspection apparatus but can be widely applied to the appearance inspection apparatus.

[0034]

As is apparent from the above description, according to the illumination device for pattern inspection according to the present invention, it is possible to obtain reflected light having sufficient luminance even in a fine pattern portion at the time of pattern quality inspection. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of a pattern inspection apparatus according to an embodiment.

FIG. 2 is a diagram schematically illustrating an arrangement position of an irradiation end of a vertical pattern edge portion.

FIG. 3 is a diagram schematically illustrating the arrangement position of a horizontal pattern edge irradiation end.

FIG. 4 is a plan view showing an example of a pattern.

FIG. 5 is a diagram showing a binarized image when the pattern of FIG. 4 is imaged without irradiating light from a top irradiation end;

FIG. 6 is a perspective view of a pattern inspection apparatus according to another embodiment.

FIG. 7 is a sectional view of a general pattern.

FIG. 8 is a cross-sectional view of a pattern in which a slightly flat portion remains in a top portion.

FIG. 9 is a cross-sectional view of a pattern in which a flat portion does not remain on a top portion.

FIG. 10 is a diagram showing an example of an inspection image (binary image) of a fine pattern portion when a pattern inspection is performed by a conventional illumination device.

[Explanation of symbols]

 Reference Signs List 10 pattern inspection apparatus 11 one-dimensional CCD element 12 CCD line sensor camera 14 top irradiation end 15 vertical pattern edge irradiation end 16 horizontal pattern edge irradiation end 17 wiring board 20, 21 cylindrical lens 22 vertical pattern 23 horizontal pattern 24 to 26 light source

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA07 AA12 AA14 AA54 AA61 BB02 CC01 DD09 FF01 FF04 GG02 GG07 HH05 HH14 JJ02 JJ09 JJ25 LL08 MM03 PP12 RR08 SS04 UU01 2G051 AA65 AB03 CA01 BB01 CA03

Claims (5)

[Claims] 1. A pattern inspection illumination used for irradiating a pattern formed on an inspection surface of an object to be inspected with light and detecting the reflected light with a light receiving element, and inspecting the quality of the pattern based on the detected information. In the apparatus, a top part irradiating means for irradiating light to a top part of the pattern, a first edge part irradiating means for irradiating light to an edge part of the pattern formed in a longitudinal direction of the light receiving element, and a light receiving element A second edge irradiating means for irradiating light to an edge of a pattern formed in a direction intersecting the longitudinal direction of the pattern, and a light source for supplying light to each of the irradiating means. Lighting equipment for inspection. 2. The illuminating device for pattern inspection according to claim 1, wherein the top irradiating means is arranged such that an optical axis thereof and a normal to an inspection surface of the inspection object form a predetermined angle, The top portion of the pattern and one edge portion of the pattern formed in the longitudinal direction of the light receiving element are irradiated with light, and the first edge portion irradiating means is the other of the pattern formed in the longitudinal direction of the light receiving element. Irradiating light to an edge portion, and the second edge portion irradiating means irradiates light to both edge portions of a pattern formed in a direction crossing a longitudinal direction of the light receiving element. Lighting equipment. 3. The illuminating device for pattern inspection according to claim 1, wherein the top irradiating unit irradiates light perpendicularly to an inspection surface of an object to be inspected via a half mirror, and the first edge. The part irradiating means irradiates light to both side edges of the pattern formed in the longitudinal direction of the light receiving element, and the second edge part irradiating means in the pattern formed in a direction intersecting the longitudinal direction of the light receiving element. An illumination device for pattern inspection, which irradiates light to both edge portions. 4. The illuminating device for pattern inspection according to claim 1, wherein the first and second edge portion irradiating means include an optical axis and an inspection surface of an object to be inspected. 5-30 each
An illumination device for pattern inspection, wherein the illumination device is arranged to be within a range of degrees. 5. The illuminating device for pattern inspection according to claim 4, wherein said first and second edge portion irradiating means include a cylindrical lens at a tip thereof.