JP2009244037A - Illuminating light source and pattern inspection device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminating unit for illuminating incident light with same incident condition at a given point in an imaging region and a pattern inspection device capable of determining the quality of a pit. <P>SOLUTION: Each of surface light sources are arranged so that a number of LEDs 2 are lined up on an LED support member 3, and illuminating light is emitted from the LEDs 2 in parallel to enter into the imaging region R at a predetermined incident angle θ. The area of the region with the LEDs 2 lined up is larger than that of the imaging region R. Illuminating light is emitted from the eight surface light sources in parallel to enter the whole of the imaging region R at a predetermined angle θ. Accordingly, illuminating light is entered at a given point on the BAC of the imaging region R from all directions at a same incident angle and thus its condition is the same even at any point in the imaging region. This allows one to determine the quality by a difference in the brightness of a pit in the whole region to be inspected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In order to inspect the surface state of an object, the present invention irradiates illumination light to an illumination light source that irradiates illumination light obliquely on the surface, and illumination light to a pattern formed on a substrate. The present invention relates to a pattern inspection apparatus that obtains a patterned image and automatically performs inspection.

There is known a pattern inspection apparatus that determines the quality of a pattern based on an image captured by irradiating illumination light onto a pattern formed on a light-transmitting substrate.
In such a pattern inspection apparatus, the reflected illumination means illuminates the inspection area obliquely from the side on which the substrate pattern is formed, and the substrate pattern is imaged by the imaging means. The presence or absence of pits (recesses or chips) on the pattern can be detected from the brightness distribution pattern of the image to be displayed. If there is a pit on the pattern, disconnection may occur, so it must be detected as a defective product.
As the illumination unit, a ring illumination unit is often used as an illumination unit for irradiating illumination light obliquely from all directions to the inspection object. As an inspection apparatus using ring illumination means, for example, there is Patent Document 1.
According to the above publication, as shown in FIG. 14A, the conventional ring illumination has a large number of LEDs 103 arranged concentrically in a thin cylindrical donut-shaped main body container 102.
Further, each LED 103 has an angle in the direction of the center O of the circle as shown in FIG. It is arranged so that illumination light can be irradiated obliquely to the work to be inspected.

JP 2002-328094 A

In the pattern inspection apparatus, the reflected illumination light is incident at the same incident angle from all directions (360 ° direction) at any point in the work inspection area, and the intensity of the light incident from each direction is the same. Must.
Furthermore, the conditions (light having the same incident angle from all directions and the intensity of light incident from each direction being the same) must be the same at any point in the inspection region. The reason will be described below.
(1) In the pattern inspection apparatus, when a pit is present on the pattern, an image is picked up as a bright (high luminance) part. When the brightness (luminance) is large, the size of the pit is large, and when the brightness (luminance) is small, the pit is small.
In the case of a small pit, it may not be determined to be defective. In this case, the quality is determined based on the brightness (luminance) of the pit.
(2) If the intensity of illumination light incident on a point in the inspection region varies depending on the direction, even if the size of the pit (chip) is the same, brightness ( (Luminance) changes.

For example, as shown in FIG. 15, it is assumed that illumination light is irradiated with strong intensity from the right side and weak intensity from the left side. The pit on the right side of the pattern P is bright because it reflects the high intensity illumination light. On the contrary, the pit on the left side of the pattern P is dark because it reflects the low intensity illumination light.
That is, even if the size of the chip (pit) is the same, the brightness (luminance) differs, and correct inspection (good / bad determination) cannot be performed. Therefore, the illumination light must be illuminated with the same intensity from all directions (360 ° direction) at any point in the inspection region.
Further, there may be a protrusion on the surface of the pattern. Since the projection is less likely to cause a disconnection, it is not necessary to detect it as a defect. In order to distinguish and detect pits and protrusions occurring on the pattern surface, the reflected illumination light is illuminated. However, depending on the angle, it is difficult to distinguish and detect pits and protrusions. In order to distinguish and detect pits on the pattern surface from protrusions, it is necessary to irradiate illumination light within an optimum angular range. Similar to the above, the pits and protrusions must be made indistinguishable by the direction in which the chip is generated. Therefore, at a certain point in the inspection region, light having the same incident angle must be incident from all directions (360 ° direction).

And if there are variations in the intensity and incident angle of the illumination light from each direction in the entire inspection area, the brightness (brightness) may vary depending on the location, even if the pits are the same size, and they can be distinguished from projections. Since it may not be able to be attached, correct inspection (good / bad judgment) cannot be performed. Therefore, at any location (point) in the inspection region, light having the same incident angle must be incident from all directions (360 ° direction), and the intensity of light incident from each direction must be the same.
In the pattern inspection apparatus, the entire image of the inspection area is imaged by scanning the imaging means, which is a CCD line sensor, in a direction orthogonal to the direction in which the line sensor extends.
FIG. 16 is a plan view of a long and narrow area captured by a CCD line sensor (not shown) at a time. The size of the imaging region is, for example, 18 mm in length and 2 μm in width.
Although schematically shown in the figure, as described above, for example, the incident illumination light is omnidirectional (360 ° direction) also in the central portion A of the imaging region, the left end portion B, and the right end portion C. ) From the same incident angle, and the intensity of light incident from each direction must be the same.

However, in the conventional ring illumination shown in FIG. 14, each LED 103 is arranged with an angle in the direction of the center O of the circle. Therefore, as shown in FIG. 17, the light from each LED is not flat light, but the illumination light is directed toward the center A of the imaging region.
Therefore, when the inspection area has a certain size as shown in FIG. 16, the central portion A is irradiated with light having a uniform intensity and angle from all directions. In C and C, the intensity of incident light varies depending on the direction.
Returning to FIG. 17, in B and C of the imaging regions, for example, there is no illumination light (A) (A) (indicated by a dotted line) incident from a direction orthogonal to the direction in which the CCD line sensor extends. For this reason, even if there is a pit with a chip in the direction of (A) or (B) at the position of B or C, the illumination light does not enter from that direction, so the pit cannot be detected.
That is, in the pattern inspection apparatus, the conventional ring illumination cannot be used as it is as the reflection illumination means.

  The present invention has been made in view of the above circumstances, and the object of the present invention is that light at the same incident angle is incident from all directions (360 ° direction) at any point in the region to be imaged. Reflective illumination means with the same incident light intensity and the same conditions at any point in the imaging region are obtained, and correct inspection of pits using this reflected illumination means It is to provide a pattern inspection apparatus capable of performing the above.

  As a result of intensive studies, the inventors of the present invention have incident light at the same incident angle from all directions (360 ° direction) at any point in the area to be imaged, and the intensity of light incident from each direction is the same. In addition, at any point in the inspection region, imaging is performed because the conditions (light having the same incident angle from all directions and the intensity of light incident from each direction being the same) are the same. A surface light source that emits light that is equal to or larger than the vertical and horizontal dimensions of the region is used as one unit, and this surface light source is formed in a plurality of rings on the same plane above the imaging region. It has been found that the imaging region may be disposed so as to surround the imaging region.

The principle of the solution means will be described with reference to FIG.
FIG. 1A is a plan view of the linear imaging region R as viewed from above. Six linear light sources A, A, U, D, O, and C having the same length and width as the imaging region R are shown in FIG. Are prepared and arranged so as to surround the imaging region R on the same plane above the imaging region R. Moreover, FIG.1 (b) is the side view which looked at Fig.1 (a) from the side.
As shown in FIG. 1, illumination light is emitted in a parallel state from linear light sources, and enters each point BAC of the imaging region R at a predetermined incident angle. That is, the light emitted from the central portion A ′ of each light source enters the central portion A of the imaging region R. Light emitted from the left end B ′ of each light source enters the left end B of the imaging region R. Furthermore, the light emitted from the right end C ′ of each light source enters the right end C of the imaging region R.
As shown in FIG. 1, AA ′, BB ′, and CC ′, which are optical paths of illumination light, are parallel to each other, and their lengths (distances from the light source to the imaging region) are also equal. Therefore, at each point of A, B, and C of the imaging region R, light having the same incident angle is incident from each direction (six directions in FIG. 1), and the intensity of light incident from each direction is the same. Further, at any point in the imaging region R, light having the same incident angle is incident from all directions, and the intensity of the light incident from each direction is the same.
In FIG. 1, the number of light sources arranged around the imaging region R is six so that the drawing is not complicated. However, as the number increases, illumination light of uniform intensity and angle is incident from all directions. To do.

FIG. 2 is an example when the imaging region is rectangular.
2A and 2B are plan views of the rectangular imaging region R as seen from above, as in FIG. 1A. Eight rectangular surface light sources having the same size as the imaging region R are shown in FIGS. To are prepared and arranged so as to surround the imaging region R on the same plane above the imaging region R. FIG. 3 is a side view of FIG. 2A viewed from the side.
From A′B′C′D ′ of the surface light sources AC, the illumination light is emitted in a parallel state and is incident on each ABCD point of the imaging region R at a predetermined incident angle. For example, as shown in FIG. 2A, light (shown by a dotted line in the figure) from the lower left D ′ of each surface light source is incident on the lower left D of the imaging region R in the figure. As shown in FIG. 2B, light from the upper right B ′ of each surface light source (indicated by a one-dot chain line in the figure) enters the upper right B of the imaging region R.
Similarly, the illumination light from the lower right C ′ of the surface light source is incident on the lower right C of the imaging region R, and the illumination light from the upper left A ′ of the surface light source is incident on the upper left A of the imaging region R.

FIG. 3 shows a state in which illumination light is incident on D of the imaging region R from D ′ of the surface light source A and D, and on C of the imaging region R from C ′.
AA ′, BB ′, CC ′, and DD ′, which are optical paths of the illumination light, are parallel to each other, and their lengths (the distance from the light source to the imaging region) are also equal. At points A, B, C, and D in the region R, light having the same incident angle is incident from each direction (eight directions in the case of FIG. 2), and the intensity of light incident from each direction is the same. Further, at any point in the imaging region R, light having the same incident angle is incident from all directions, and the intensity of light incident from each direction is the same.
As the number of surface light sources arranged around the imaging region R increases, illumination light having a uniform intensity and angle enters from all directions. However, as will be described later, when the number of surface light sources is increased, the diameter (size) of the illumination means is increased accordingly, and the apparatus is increased in size.

Based on the above, the present invention solves the above problems as follows.
(1) In the illumination light source, a plurality of surface light sources that irradiate light parallel to the illuminated area are arranged in a ring shape on the same plane, and the size of each surface light source is irradiated on the illuminated area surface. The area irradiated with light from the surface light source has a size including the entire illuminated area.
(2) In the above (1), the plurality of surface light sources are configured by arranging a plurality of LEDs on the same plane. Then, the LEDs in each surface light source are arranged to be inclined toward the inner side of the annular surface where each surface light source is arranged so that parallel light from each surface light source is illuminated on the illuminated area. (3) In the above (1), the plurality of surface light sources are composed of a plurality of annularly arranged prism sheets for emitting light emitted from the plurality of LEDs as parallel light on the light emitting side of the plurality of LEDs. The prism sheet constituting each surface light source refracts the light emitted from each LED to the inner side of the ring where each surface light source is arranged so that the parallel light from each prism sheet is illuminated on the illuminated area. .
(4) Dark field illuminating means for irradiating reflected illumination light obliquely to the workpiece on which the pattern is formed, imaging means for imaging the pattern illuminated by the dark field illuminating means, and workpiece holding means for holding the workpiece And a control unit that determines the quality of the pattern based on the pattern image picked up by the image pickup unit, the illumination light source of (1) to (3) is used as the dark field illumination unit. Use.

In the present invention, the following effects can be obtained.
(1) Light at the same incident angle is incident from any direction (360 ° direction) at any point in the area to be imaged, and the intensity of light incident from each direction is the same, and which point in the inspection area The light can be illuminated so that the conditions are the same, that is, light having the same incident angle is incident from all directions and the intensity of light incident from each direction is the same.
For this reason, the brightness (luminance) in the area to be imaged does not change depending on the location, and any point in the inspection area can be imaged under the same conditions.
(2) By using the illumination light source of the present invention as dark field illumination means of the pattern inspection apparatus, pits and protrusions are distinguished from captured images in all areas to be inspected, and the brightness (luminance) of the pits is different. Therefore, pass / fail can be determined.

Hereinafter, a specific configuration example of the light source unit of the illumination unit according to the embodiment of the present invention will be described. FIG. 4 is a diagram showing the configuration of the surface light source that constitutes the illumination means of the first embodiment of the present invention, in which a plurality of LEDs are inclined and arranged in parallel so that the illumination light is emitted in a parallel state. An embodiment of a surface light source that enters the imaging region at a predetermined incident angle will be described.
4A is a plan view of an illumination surface light source viewed from the lower side (imaging region side), FIG. 4B is a side view of the light source of FIG. 4A viewed from the A direction, and FIG. 4 (c) is a front view of the light source of FIG. 4 (a) viewed from the B direction. These figures are schematic diagrams for easy understanding, and actual LEDs are arranged with a large number of intervals.
In the present embodiment, as shown in the figure, the surface light source 1 is configured so that the chief rays of the illumination light from the respective LEDs 2 are emitted in parallel and enter the imaging region R at a predetermined incident angle θ. . Note that a diffusing plate 4 may be provided between the LED 2 and the imaging region R as shown by the dotted line in FIG.

As shown in FIG. 4A, a large number of LEDs 2 are arranged on the LED support member 3 so that the strongest light components (principal rays) among the light emitted from the LEDs 2 are parallel to each other. Since parallel light from the surface light source 1 must enter the imaging region R, the size of the region where the LEDs 2 are arranged is made larger than the size of the imaging region R.
A plurality of the surface light sources 1 configured as described above are arranged in a ring shape so as to surround the imaging region in a plane on the imaging region in blocks. Therefore, it is convenient to form the support member 3 in a fan shape.
As shown in FIG. 4B, the LED 2 is disposed to be inclined toward the imaging region R so that the incident angle of the illumination light to the imaging region R becomes a desired angle θ.
Since the light emitted from the LEDs 2 has high directivity, the light from each LED 2 enters the imaging region R in a substantially parallel state.

A plurality of the surface light sources 1 configured in this way are arranged in an annular shape so as to surround the imaging region R in the same plane above the imaging region R.
5 and 6 are diagrams schematically showing a state in which the eight surface light sources of FIG. 4 are arranged uniformly at 45 °. 5 (a) and 6 are plan views, and FIG. 5 (b) is a side view. Note that a diffusion plate 4 may be provided between the LED 2 and the imaging region R as shown by the dotted line in FIG.
FIG. 5 shows a state in which illumination light is irradiated from the eight surface light sources 1-a to 1-k to the linear imaging region R. 1 to 3, the imaging region R and the surface light source 1 have been described as having the same size. However, in the present drawing, the area of the surface light source 1 is larger than the area of the imaging region R.
Actually, it is difficult to make the size of the imaging region R coincide with the size of the surface light source 1, and in order to make parallel light incident on the entire imaging region R with uniform illuminance, the area of the surface light source 1 is imaged. This is because it is advantageous to make it slightly larger than the area of the region.

In FIG. 5, illumination light is emitted from eight surface light sources in a parallel state, and enters the entire imaging region R at a predetermined angle θ. Therefore, at any point on the BAC in the imaging region R, illumination light of the same angle from all directions (360 ° direction) is incident with the same irradiation intensity, and the condition (omnidirectional (360) The illumination light at the same angle from the direction (°) is incident at the same irradiation intensity).
FIG. 6 shows a state in which illumination light is irradiated from eight surface light sources to the rectangular imaging region R. As in the case of FIG. 5, the illumination light is emitted from the eight surface light sources in a parallel state, and is incident on the entire imaging region R at a predetermined angle θ.
Therefore, at any point in the region surrounded by ABCD in the imaging region R, illumination light of the same angle enters from all directions (360 ° direction) with the same irradiation intensity, and the condition is set at any point in the imaging region R. Be the same. That is, illumination light having the same angle enters from all directions (360 ° direction) with the same irradiation intensity.

Next, the illumination means of the second embodiment of the present invention will be described.
In this embodiment, an LED and a prism sheet are used in combination.
Similar to the first embodiment, a large number of LEDs are arranged in a ring on a flat support member and arranged on the imaging region. However, the LEDs are arranged so as to face directly below without being inclined. Therefore, among the light emitted from each LED, the strongest light components (principal rays) are parallel to each other.
Fig.7 (a) is the top view which looked at the light source arrange | positioned in that way from the bottom, FIG.7 (b) is AA sectional side view of FIG. This figure is a schematic diagram for easy understanding, and in actuality, LEDs are arranged with a large number of intervals.
As shown in FIG. 7B, in this embodiment, the LED 2 is attached to the support member 3 so that the principal ray of light emitted from the LED 2 is orthogonal to the plane including the imaging region.
A prism sheet is divided and attached to the light emission side of the light source. As will be described later, the prism sheet to be divided is larger than the imaging region, and has a shape that divides the light emitting portion at an equal angle.

A prism sheet is a sheet in which a large number of prisms with a triangular cross section are arranged on one side of a transparent sheet so that the major axis direction is parallel, and so-called peaks and valleys are continuously formed in a straight line. is there. The prism sheet is provided between the backlight and the liquid crystal panel, for example, in order to make the brightness of the liquid crystal panel uniform in a liquid crystal display screen.
As shown in FIG. 8, such a prism sheet is cut into the size of a surface light source to be formed, and a plurality of such sheets are prepared. As shown in FIG. 8, the prism sheet is cut out in such a direction that the major axis direction of the prism formed on the prism sheet 5 is substantially orthogonal to the central axis rr of the fan-shaped surface light source.
That is, when the prism sheet is attached to the light source, parallel light emitted from the prism sheet is cut out so as to enter the imaging region R at an approximately equal incident angle.
And as shown in FIG. 9, it attaches to the light emission side of the light source shown in FIG. In FIG. 9, eight prism sheets 5 are attached, and the illuminating means is in a state in which eight surface light sources are equally arranged at 45 ° as in the first embodiment.

FIG. 10 is an enlarged view of a portion of the light source to which one prism sheet is attached. 10A is a plan view of the illumination light source viewed from below, FIG. 10B is a side view of the light source of FIG. 10A viewed from the direction A, and FIG. 10C is FIG. It is the front view which looked at the light source of (a) from the B direction.
As shown in FIGS. 10B and 10C, the prism sheet 5 is attached to the LED support member 3 via a column 6. In addition, you may provide the diffusion plate 4 between the prism sheet 5 and LED2 as shown to the dotted line of the figure.
As shown in FIG. 10B, the illumination light in which the principal rays emitted from the respective LEDs 2 are parallel is incident on the slope of the prism of the prism sheet 5 and refracted, and branches in two directions while maintaining the parallel state. . One branched light component illuminates the imaging region R at an incident angle θ. The other branched light component is not used. The prism angle of the prism sheet 5 is designed so that the incident angle θ has a desired value.

FIG. 11 is a modification of the prism sheet used in FIG. In the case of FIG. 10, since the light incident on the prism sheet 5 is divided into two directions, half of the light emitted from the LED 2 is not used. Therefore, the light utilization efficiency is poor.
In order to solve this problem, the prism cross-sectional shape of the prism sheet 5 is a right triangle. Thereby, the light incident on the prism is refracted only in one direction, and all the light emitted from the LED 2 can be used.

FIG. 12 shows the experimental results of observing pits generated on the pattern using the illumination means of the second embodiment shown in FIG. In this experimental example, as shown in FIG. 12 (c), the number of illumination light sources divided by using the prism sheet 5 is 12, that is, 12 surface light sources are arranged uniformly at 30 °. State.
FIG. 12A shows a pit (observed object) generated in a certain pattern on the left side of the field of view of the imaging means (CCD line sensor) (corresponding to the position B of the imaging region R) and the center of the field of view (imaging region). A graph showing a change in luminance of a pit received by the imaging means when rotated 360 ° at the respective positions on the right side of the visual field (corresponding to the position C of the imaging region R)) It is. In the figure, the vertical axis represents the luminance (relative value), and the horizontal axis represents the rotation angle of the pit (observed object).
If light of the same incident angle is incident from any direction (360 ° direction) at an arbitrary point in the imaging region R and the intensity of light incident from each direction is the same, the brightness of the pit can be improved even if rotated. There should be no change.

When illuminated by the illumination means of the conventional example shown in FIG. 14, when the pit was rotated at the center (A) of the visual field, the change in luminance was approximately ± 8%. On the other hand, in the present invention, as shown in FIG. 12 (a), even if the pit is rotated, the field of view is left (B), the center of the field of view (A), or the right of the field of view (C). However, there is little change in brightness. The change in luminance is approximately ± 3% at any position, which is less than half that of the conventional example.
FIG. 12B shows changes in luminance when pits (observed objects) generated in a certain pattern are moved to the left (B), the center (A), and the right (C) of the field of view of the imaging unit. It is the shown graph. In the figure, the vertical axis represents the luminance (relative value), and the horizontal axis represents the position in the imaging means. From the left of the plotted points, the left field of view (B), the center of the field of view (A), and the right field of view (C). That is, the difference in luminance when the same pit is viewed with the left field of view (B), when viewed with the center of the field of view with (A), and with the right field of view (C).
If the entire inspection area is illuminated under the same conditions, even if you change the position where you place the pit (observation object) (any position in the field of view of the imaging means), what you see is the same pit, Its brightness should not change.
In addition, the graph of “(old)” indicated by the alternate long and short dash line in the figure is an experimental result when illuminated by the illumination means of the conventional example shown in FIG.

As shown in FIG. 12B, in the case of the conventional example, when the pit position is moved, the luminance changes greatly. In particular, the luminance increases at the center of the visual field (A), and the luminance decreases at the end of the visual field (imaging region) such as the visual field left (B) and the visual field right (C). The change in luminance is approximately ± 8%.
On the other hand, in the present invention, the luminance increases at the center of the visual field (A) and tends to decrease at the left visual field (B) and the right visual field (C), but the change is about ± 4.5%. It can be reduced to about half compared to the conventional example.
Note that as the number of illumination light sources divided by the prism sheet, that is, the number of surface light sources, increases, uniform illumination light can be irradiated from all directions to the imaging region.
However, as described above, since the entire imaging region must be irradiated with parallel light, the size of the surface light source must be the same as or larger than the size of the imaging region.
Therefore, when the number of surface light sources is increased, the diameter (size) of the illumination means is increased accordingly, and the apparatus is increased in size. Therefore, the number of illumination means to be divided (number of surface light sources) is limited from the viewpoint of preventing the apparatus from becoming large, and 12 divisions (12 surface light sources) shown in the above experimental example are appropriate. it is conceivable that.

The illumination light source of the present invention can be applied to an inspection apparatus for inspecting the surface state of an object. Hereinafter, a case where the illumination light source of the present invention is applied to a pattern inspection apparatus will be described.
FIG. 13 is a view showing an embodiment when the illumination means of the present invention is applied to a pattern inspection apparatus, and FIG. 13 is a view of the inspection apparatus of this embodiment as viewed from the side.
In FIG. 13, dark field illumination means (reflective illumination means) 10 for irradiating reflected illumination light is the illumination light source shown in the first or second embodiment, and is provided around the image pickup unit 11 in a ring shape. The work W is illuminated from all 360 ° directions of the imaging unit.
The imaging unit 11 includes a CCD line sensor 11a that is an imaging element and a lens unit 11b that includes an optical element that forms an image of a pattern on the workpiece W on the CCD line sensor 11a.

An imaging unit driving mechanism 12 is attached to the imaging unit 11, and the imaging unit 11 is scanned (scanned) in the direction of the arrow in the figure by driving the imaging unit driving mechanism 12 by the scanning unit 13.
A workpiece W provided with a pattern such as wiring to be inspected is placed on a workpiece holding means (work stage) 14 and is formed on the workpiece W by scanning the imaging unit 11 on the workpiece W. A pattern such as a wiring line is picked up.
The scanning unit 13, the imaging unit 11, the dark field illumination unit 10, and the like are controlled by the control unit 15.

In FIG. 13, when the work W is placed on the work holding means (work stage) 14, the dark field illumination means (reflective illumination means) 10 is turned on.
Next, the imaging unit 11 is scanned by the scanning unit 13 in the width direction of the workpiece W from one side to the other side (from right to left in the figure). The wiring pattern image on the workpiece W illuminated by the dark field illumination means 10 is received by the CCD line sensor 11a of the imaging unit 11 and stored in the control unit 15.
When the imaging of the wiring pattern is finished, the dark field illumination means 10 is turned off.
The control unit 15 performs image processing on the image pattern captured by the imaging unit 11 and detects the presence or absence of a defect on the pattern. If there is an abnormality, an alarm or the like is output.
When the inspection of the pattern is completed, the workpiece W to be inspected next is placed on the workpiece holding means 14, and the above-described operation is repeated thereafter.
In the above description, the pattern inspection of the substrate has been described. However, even in the case of the pattern inspection of the film-like workpiece, it is different in that a film-like workpiece feeding mechanism is provided, but can be realized by the same apparatus.

It is a figure explaining the principle of this invention (when an imaging region is linear). It is a figure explaining the principle of this invention (when an imaging region is rectangular shape). FIG. 3 is a side view of FIG. It is a figure which shows the structure of the surface light source which comprises the illumination means of 1st Example of this invention. It is a figure which shows the case where eight surface light sources of FIG. 4 are arrange | positioned equally. It is a figure explaining the case where illumination light is irradiated with respect to the rectangular imaging region R from eight surface light sources. It is a figure explaining the structure of the light source which comprises the illumination means of the 2nd Example of this invention. It is a figure explaining extraction of a prism sheet. It is a figure explaining attachment of the prism sheet to the light source shown in FIG. It is the figure which expanded and showed the surface light source which comprises the illumination means of a 2nd Example. It is a figure which shows the modification of the prism sheet used in FIG. It is a figure which shows the experimental result which observed the pit using the illumination means of the 2nd Example. It is a figure which shows the Example at the time of applying the illumination means of this invention to a pattern inspection apparatus. It is a figure explaining the conventional ring illumination means. It is a figure explaining the case where brightness (luminance) changes with directions in which a chip has occurred, even if the size of a pit (chip) is the same. It is a top view of the elongate area | region which a CCD line sensor images at a time. It is a figure explaining that illumination light goes to the center part of an imaging region in the conventional ring illumination means.

Explanation of symbols

1 Surface light source 2 LED
3 Support member 4 Diffuser plate 5 Prism sheet 6 Post 10 Dark field illumination means (reflective illumination means)
DESCRIPTION OF SYMBOLS 11 Imaging unit 11a CCD line sensor 11b Lens unit 12 Imaging unit drive mechanism 13 Scanning means 14 Work holding means (work stage)
15 Control unit R Imaging area W Work area to surface light source

Claims (4)

A plurality of surface light sources that irradiate light parallel to the irradiated region are arranged in a ring on the same plane,
The illumination light source characterized in that the size of each surface light source is such that the irradiation area of light from each surface light source irradiated on the surface of the illuminated area includes the entire illuminated area. The plurality of surface light sources are configured by arranging a plurality of LEDs on the same plane,
The LEDs in each surface light source are arranged to be inclined toward the inner side of the ring in which each surface light source is arranged so that parallel light from each surface light source is illuminated on the illuminated area. The illumination light source according to claim 1. The plurality of surface light sources are configured by arranging a plurality of prism sheets that emit light emitted from the plurality of LEDs as parallel light on the light emission side of the plurality of LEDs,
The prism sheet that constitutes each surface light source refracts the light emitted from each LED to the inner side of the ring in which each surface light source is arranged so that parallel light from each prism sheet is illuminated on the illuminated area. The illumination light source according to claim 1, wherein: Dark field illumination means for irradiating reflected illumination light obliquely with respect to the workpiece on which the pattern is formed; imaging means for imaging the pattern illuminated by the dark field illumination means;
A work holding means for holding the work;
In a pattern inspection apparatus comprising a control unit for determining the quality of a pattern based on a pattern image imaged by the imaging means,
The pattern inspection apparatus according to claim 1, wherein the dark field illumination means is the illumination light source according to claim 1.

Images