KR101659587B1 - Surface defect inspection apparatus - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus, and more particularly, to a frame surface defect inspection apparatus capable of inspecting defects such as particles adhering to the inner surface of an inspection object having an inner surface such as a pellicle frame. The apparatus for inspecting surface defects according to the present invention comprises a first image acquiring means arranged obliquely with an object to be inspected to acquire an image of an inner surface of an object to be inspected and an inner surface formed by a plane portion and a curved portion of the object to be inspected, And a transfer means configured to relatively move the inspected object relative to the first image acquiring means such that the inner surface faces the first image acquiring means with a constant distance between the first image acquiring means and the first image acquiring means, And the light receiving element array is arranged such that the central axis of the light receiving element array is inclined at a certain angle with the central axis of the lens. The apparatus for inspecting surface defects according to the present invention is characterized in that the distance between the inner surface of the object to be inspected and the image acquiring means is kept constant even when the inner surface of the rounded corner is inspected and the image of the inner surface of the object to be inspected . Therefore, there is an advantage that the defect on the inner surface of round corner can be precisely inspected.

Description

[0001] Surface defect inspection apparatus [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus, and more particularly, to a frame surface defect inspection apparatus capable of inspecting defects such as particles adhering to the inner surface of an inspection object having an inner surface such as a pellicle frame.

BACKGROUND ART [0002] In the production of a semiconductor device or a liquid crystal display panel, a method called photolithography is used in which a semiconductor wafer or a liquid crystal substrate is irradiated with light and patterned.

In photolithography, a mask is used as an original plate for patterning, and a pattern on the mask is transferred to a wafer or liquid crystal substrate. At this time, if dust is adhered to the mask, light is absorbed or reflected by the dust, so that the transferred pattern is damaged, resulting in a problem that the performance and the yield of the semiconductor device and the liquid crystal display panel are lowered. So their work is usually done in a clean room. However, since dust is present even in this clean room, a method of attaching a pellicle to prevent dust from adhering to the surface of the mask has been carried out. In this case, the dust is not directly attached to the surface of the mask but attached to the pellicle. At the time of lithography, the focus is located on the pattern of the mask, so that the dust on the pellicle is not focused and is not transferred to the pattern.

The pellicle includes a pellicle frame for supporting the pellicle membrane and the pellicle membrane, and an adhesive layer for attaching the pellicle frame to the mask is formed under the pellicle frame.

Photolithography Process Particles existing on the surface of a mask having a pellicle attached thereto, a surface of a pellicle film, or a surface of a pellicle frame may contaminate the pattern of the mask and cause a process failure. Therefore, inspection is required.

No. 1344817 discloses an apparatus for automatically inspecting defects in a reticle assembly having a reticle and a pellicle attached to the top surface of the reticle. The apparatus of Japanese Patent No. 1344817 includes a first optical system for irradiating light perpendicular to the reticle assembly to acquire a reference image, a second optical system for irradiating light in an inclined state to acquire an image secondarily, and a reticle assembly, And a linear motor system configured to pass the laser beam at a constant velocity downward and to stop below the second optical system.

Patent No. 1344817

Particles present on the inner surface of the pellicle frame must be inspected in that they are very likely to contaminate the pattern of the mask. However, the conventional inspection apparatus described above has a problem that it is difficult to inspect the inside chamfer and rounded inside of the pellicle frame. That is, since the conventional inspection apparatus acquires an image of one side of the pellicle frame by using the line scan camera of the second imaging unit, and then rotates the pellicle frame by 90 degrees to acquire the image of the other side, I can not. Further, since the second image capturing unit only moves up and down suitable for acquiring the inner surface image, the image of the chamfer can not be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a frame surface defect inspection apparatus capable of precisely inspecting defects in the inner chamfer and the inner edge of a corner of a pellicle frame.

According to an aspect of the present invention, there is provided an image forming apparatus including a first image acquiring unit that is disposed obliquely with an object to be inspected, an inner surface formed by a plane portion and a curved surface of the object to be inspected, Conveying means configured to relatively move the inspected object relative to the first image acquiring means such that the inner surface faces the first image acquiring means while the distance between the acquiring means is kept constant; (X) between a plane shape (A) of an inspected object and a plane shape (B) of a standard inspected object obtained by the shape information acquiring means; Wherein the first image acquiring unit includes a light receiving element array and a lens disposed between the object to be inspected and the light receiving element array Wherein the light receiving element array is arranged such that the central axis of the light receiving element array is inclined at a predetermined angle with respect to the central axis of the lens, and the feeding means receives the offset value (x) obtained by the controller, And the distance between the inner surface of the object to be inspected and the first image acquiring means is kept constant by correcting the distance between the first image acquiring means and the first image acquiring means.

The conveying unit may be configured to be able to linearly move and rotate on a plane, and the conveying unit may be configured such that when the image of the curved surface of the inner surface of the inspected object is captured, And rotating the inspection object and moving the inspection object in a plane.

The shape information acquiring means is a second image acquiring means configured to acquire a planar image of the inspected object. The second image acquiring unit may be disposed perpendicular to the inspected object.

The shape information acquiring means may be a distance measuring sensor for measuring a distance between the outer surface of the object to be inspected and a reference surface.

Further, the light-receiving element array of the first image acquiring means may reflect the light from the lens of the light incident on the light-receiving element array after passing through the lens while being reflected by an area of the inner side far from the lens, (L2) of the light from the lens to the light-receiving element array of the light incident on the light-receiving element array after passing through the lens is reflected by the area of the inner side surface closer to the distance from the lens A surface defect inspection apparatus which is inclined to a short side is provided.

The controller may further include a surface defect inspection device that receives the trigger signal through the encoder provided in the transfer means and controls the first image acquisition means so that the image acquisition of the first image acquisition means is synchronized with the movement of the inspected object to provide.

In addition, when inspecting the long side and the short side of the inspection object, a trigger signal is received through a linear encoder which senses linear movement of the conveying means to control the first image acquiring means, And a control unit for controlling the first image acquiring unit to receive the trigger signal through a rotary encoder for sensing the rotation of the first image acquiring unit.

In addition, the inner surface of the object to be inspected includes a curved surface portion, and the controller measures an offset value (x) of a point at which the curved surface portion ends, one circle having a radius of curvature of the curved surface portion of the standard object to be inspected as a radius, The center of the circle is shifted by an offset value of the point at which the curved surface ends, and then the transporting means is driven on the basis of the locus of the two circles.

Also, the controller rotates the conveying means in the forward direction from the point where the curved surface starts to the center of the curved surface portion, and rotates the conveying means in the reverse direction from the center of the curved surface portion to the end point of the curved surface portion.

The apparatus for inspecting surface defects according to the present invention is characterized in that the distance between the inner surface of the object to be inspected and the image acquiring means is kept constant even when the inner surface of the rounded corner is inspected and the image of the inner surface of the object to be inspected . Therefore, it is possible to precisely inspect defects on the inner side of round corner.

1 is a perspective view of an embodiment of a surface defect inspection apparatus according to the present invention.
2 is a perspective view of the mask assembly;
3 is a plan view of the pellicle.
4 is a conceptual diagram of an optical system for internal side photographing.
5 is a view for explaining focus change of an image according to the distance between the lens and the light receiving element array.
6 is a plan view of the stage unit shown in Fig.
7 is a diagram for explaining a method of measuring an offset value of an edge portion.
8 is a diagram for explaining another method of measuring the offset value of the corner portion.
9 is a view for explaining the movement of the stage unit according to the difference between the center of the corner round and the rotation axis of the mask clamp.
10 is a view for explaining a process of acquiring a corner shape by the first image acquiring unit.
11 is a view for explaining another process in which the first image acquiring means acquires the edge shape.

Hereinafter, preferred embodiments according to the present invention will be described in detail. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms.

1 is a perspective view of an embodiment of a surface defect inspection apparatus according to the present invention. 1, an embodiment of a surface defect inspection apparatus according to the present invention includes a support structure 10, a first image acquiring means 20, a second image acquiring means 30, a controller (not shown) A stage unit 40 which is a conveying means, and a distance measuring sensor 50.

The apparatus for inspecting a surface defect on a surface of a frame includes a first image acquiring means 20 and a second image acquiring means 30 using particles scattered on a surface of a mask assembly 1 moving on an XY plane by a transfer means, Is a device to inspect through.

2 is a perspective view of the mask assembly; As shown in FIG. 2, the mask assembly 1 includes a mask 2 and a pellicle 3 attached to the upper surface of the mask 2. The pellicle (3) includes a pellicle frame (4) and a pellicle frame (5) supporting the pellicle film (4). The pellicle 3 is attached to the mask 2 using a pressure-sensitive adhesive layer formed on the lower surface of the pellicle frame 5. [ The pellicle frame 5 is usually a rectangular frame with rounded corners, but octagonal or circular frames are also used. The pellicle frame 5 also varies in size depending on its use. For example, a large pellicle is used in the LCD manufacturing process and a relatively small pellicle is used in the semiconductor process.

3 is a plan view of the pellicle. As shown in Fig. 3, the actual pellicle frame 5 is curved inwardly in the long side and in the cross-section due to the tension of the pellicle film 4, and rounds of the corner portions are not in a garden shape due to processing variations.

Referring again to FIG. 1, the support structure 10 has an X-axis, a Y-axis, and a Z-axis direction. The support structure 10 serves to support the first image acquiring means 20, the second image acquiring means 30, the controller, the stage unit 40 as the conveying means, and the like. The support structure 10 may comprise a plurality of frames.

The first image acquiring means 20 serves to acquire an image of the inner surface of the pellicle frame 5 of the mask assembly 1. [ In the present invention, the inner surface includes an inner surface 6 orthogonal to the upper surface of the mask 2 and a chamfer 7. The first image acquiring means 20 may include a camera, a lens, a lens holder, an illumination, and the like. The first image acquiring means 20 is arranged so as to be inclined such that the central axis of the first image acquiring means 20 forms an angle as close as possible to the inner surface 6 of the pellicle frame 5 as much as possible for image acquisition of the inner surface 6. [

When light is irradiated from the illumination of the first image acquiring means 20, light irradiated from the illumination is scattered by the particles on the surface of the mask assembly 1. The camera can acquire an image capable of distinguishing particles using light reflected from the surface of the mask assembly 1 and scattered light.

The first image acquiring unit 20 may include one optical system including a camera, a lens, a lens holder, and illumination, but may include two optical systems as shown in FIG. That is, the optical system 20-1 for photographing the inner side 6 and the optical system 20-2 for photographing the chamfer 7 can be respectively provided.

4 is a conceptual diagram of an optical system for internal side photographing. As shown in Fig. 4, the optical system for the inside-side photographing includes a line scan camera and a lens 21. The line scan camera includes a plurality of one-dimensionally arranged charge coupled device (CCD) elements, and a light receiving element array 22 such as a CMOS (Complementary Metal Oxide Semiconductor) element. The lens 21 focuses the light reflected by the inner side surface 6 of the pellicle frame 5 and transmits the light to the light receiving element array 22. Here, the lens 21 is arranged such that the central axis of the lens 21 and the central axis of the light receiving element array 22 are inclined to each other. The arrangement of the light receiving element arrays 22 is inclined so that the distance between the inner side surface 6 and the lens varies depending on the position of the inner side surface 6 of the pellicle frame 5, So that the line scan camera can obtain a clear image of the entire inside surface 6 of the frame 5 of the pellicle.

The distance D1 between the upper end of the inner side surface 6 of the pellicle frame 5 and the lens 21 is smaller than the distance D1 between the lower end of the inner side surface 6 of the pellicle frame 5 and the lens 21, The distance L2 between the lower end of the light receiving element array 22 and the lens 21 on which the light reflected by the upper end of the inner side surface 6 is incident is smaller than the distance D2 between the lower end The distance between the upper end of the light receiving element array 22 and the lens 21 is longer than the distance L1 between the upper end of the light receiving element array 22 and the light receiving element array 22.

5 is a view for explaining focus change of an image according to the distance between the lens and the light receiving element array. The distance D between the lens 21 and the object S is close to the distance between the lens 21 and the light receiving element array 22 as shown in Figures 5 (a) and 5 (b) The distance L between the lens 21 and the light receiving element array 22 is longer than the distance D between the lens 21 and the object S when the image focused on the light receiving element array 22 is focused, The image focused on the light receiving element array 22 is focused. As shown in FIG. 5 (c), if the light receiving element array 22 is not placed in an appropriate position, the image is out of focus and the image is blurred.

The light receiving element array 22 is arranged so that the center axis of the lens 21 and the central axis of the light receiving element array 22 are inclined with respect to each other, A clear image of the entire inner surface 6 can be obtained by compensating for the variation in the distance between the side surface 6 and the lens 21.

Since the chamfer 7 is entirely contained in the depth of field of the camera, a separate optical system 20-2 for photographing the chamfer 7 places the light receiving element array so that the central axes of the lens and the light receiving element array coaxial with each other .

The inclination angle of the optical system 20-1 for photographing the inner side 6 and the optical system 20-2 for photographing the chamfer 7 may differ from each other. That is, it is preferable that the angle of inclination of the optical system 20-2 for chamfering with the inner surface 6 of the pellicle frame 5 is 45 degrees, and the optical system 20-1 for the inner surface photographing is the pellicle frame 5 Of the inner surface (6).

The second image acquiring means 30 serves to acquire images of the upper surface 8, the lower surface 9 and the pellicle film 4 of the mask 2 of the mask assembly 1. The second image acquiring unit 30 may also include a camera, a lens, a lens holder, an illumination unit, and the like as the first image acquiring unit 20. The second image acquiring means 30 is arranged such that its central axis is orthogonal to the mask assembly 1 for plane image acquisition.

The second image acquiring means 30 may be composed of one optical system, but in the present embodiment, as shown in Fig. 1, it includes two optical systems. That is, it is possible to separately provide a high-resolution optical system 30-1 for inspecting the upper surface 8 of the mask 2, a pellicle film 4, and a low-resolution optical system 30-2 for the mask- have.

The transfer means moves the mask assembly 1 relative to the first image acquiring means 20 and the second image acquiring means 30 so that the first image acquiring means 20 and the second image acquiring means 30 And serves to acquire the entire surface image of the mask assembly 1. The transfer means can move the mask assembly 1, or conversely, move the first image acquiring means 20 and the second image acquiring means 30. In this embodiment, the first image acquiring means 20 and the second image acquiring means 30 are fixed to the supporting means 10 and the surface of the mask assembly 1 is fixed by using the stage unit 40, A method of acquiring an image while moving within the depth of field of the first image acquiring means 20 and the second image acquiring means 30 is used.

6 is a plan view of the stage unit shown in Fig. 6, the stage unit 40 includes a first stage 41 and a second stage 42, and a mask clamp unit 43. [ The first stage 41 moves along the guide rail 11 in the X-axis direction provided on the support means 10. [ The second stage 42 moves along the guide rail 44 in the Y-axis direction provided on the first stage 41. The mask clamp unit 43 is provided on the second stage 42 and rotates about a rotational axis orthogonal to the X-Y plane.

The stage unit 40 further includes a linear encoder for detecting movement of the first stage 41 in the X-axis direction and a linear encoder for detecting movement of the second stage 42 in the Y-axis direction. Further, it further includes a rotary encoder for detecting the rotation of the mask clamp unit 43. [ These encoders serve to supply a trigger signal to the controller to synchronize the line scan camera with the motion of the pellicle frame (5).

Referring again to FIG. The distance measuring sensor 50 serves to arrange the pellicle frame 5 in place. In this embodiment, the distance measuring sensor 50 measures the distance between the long side of the pellicle frame 5 of the mask assembly 1 fixed to the mask clamp unit 43 of the stage unit 40 and the reference line A pair of laser displacement sensors 51, and a pair of laser displacement sensors 52 for measuring the distance between the short sides. The distance value of the pellicle frame 5 measured by the distance measuring sensor 50 and the distance between the long side and the short side of the pellicle frame 5 from the reference line is transmitted to the stage unit 40. The stage unit 40 uses this value, Are placed in place.

The controller serves to position the pellicle frame 5 in place by controlling the stage unit 40 by transferring the measured value from the distance measuring sensor 50 to the stage unit 40. [ The stage unit 40 is connected to the first image acquiring unit 20 and the second image acquiring unit 30 so that the first image acquiring unit 20 and the second image acquiring unit 30 scan the surface of the mask assembly 1 to acquire images. And moves along the path in the depth of field of the second image acquiring means 30.

As described above, unlike the ideal pellicle frame, the actual pellicle frame 5 is curved inwardly in the long side and in the cross-section due to the tension of the pellicle film 4, and rounds of the corner portions are not in a garden shape due to processing variations. Therefore, if the controller drives the stage unit 40 on the basis of the ideal shape of the pellicle frame 5, there is a problem that the carrera is out of focus and a clear image can not be obtained. To solve this, the controller provides the stage unit 40 with an offset value x between the shape of the actual pellicle frame A and the shape of the ideal pellicle frame B (see FIG. 3).

The offset value x can be obtained by obtaining the shape A of the actual pellicle frame through the image of the pellicle film 4 obtained by the second image acquiring means 30 and comparing it with the ideal standard frame shape B . The standard frame shape B may be pre-stored in a memory of the controller in the form of a table. The offset value x may be a distance between a closed curve by the inner surface of the standard frame shape B and a closed curve by the inner surface of the obtained frame shape A. [ That is, the normal line of the closed curve by the inner surface of the standard frame shape B can be obtained, and the length between the closed lines of the normal line can be set as the offset value (x).

7 is a diagram for explaining a method of measuring an offset value of an edge portion. Referring to FIG. 7, the offset value (x) of the edge round portion can be obtained by the following method. First, a point (S) at which a round starts from the shape (A) of an actual pellicle frame and a point (E) at which an end is found. Then, a circle (c1) having a design value of the radius as a radius is drawn based on the point (S) at which the round starts. Then, the offset value x, which is the distance between the circle c1 and the closed curve due to the inner surface of the round portion of the shape (A) of the actual pellicle frame, is measured. There may be differences depending on the depth of field range of the first image acquiring means 20, but the offset value of the edge round can be measured at intervals of about 3 degrees.

8 is a diagram for explaining another method of measuring the offset value of the corner portion. In this method, as shown in Fig. 8, at a point where a line extending from the inner side of the long side of the shape (A) of the actual pellicle frame and a line extending from the inner side of the short side meet, And a circle c3 centered on a point moved in the Y-axis direction, respectively. Then, the offset value x, which is the distance between the circle c3 and the closed curve due to the inner surface of the round portion of the shape A of the actual pellicle frame, is measured.

As another method, a distance measuring sensor can be used. For example, while the stage unit 40 is moved in the X-axis direction, the offset value of the outer surface of one side of the short side of the pellicle frame 5 is obtained and the offset value of the one side of the long side of the pellicle frame 5 The offset value of the outer surface can be obtained, and the offset value of the remaining outer surfaces can be obtained while moving the stage unit 40 in the X-axis direction and the Y-axis direction again. Since the thickness of the pellicle frame 5 is substantially uniform, the offset value of the outer surface can be used for image acquisition of the inner surface using the first image acquiring means 20. [

The surface defect inspection apparatus also includes an alignment mark recognizing device (not shown) for loading the mask assembly 1 to be inspected and detecting an alignment mark displayed on the mask 2 for aligning the mask 2 with a loading device (Not shown) for acquiring an image of the entire pellicle frame 5 in order to recognize the size of the pellicle frame 5, as shown in FIG.

Further, it may further comprise a review image acquiring means (not shown) capable of ensuring a high-resolution image that can be confirmed again on the inspection result. The review image acquiring means may include an optical system vertically disposed on the mask assembly 1 and an optical system disposed on the mask assembly 1 inclined about 45 degrees. The optical system arranged vertically is used for reaffirming the particles detected through the second image acquiring means 30 and the optical system arranged at a tilt angle of about 45 degrees is used for acquiring the particles detected through the first image acquiring means 10. [ Is used to reconfirm the.

Hereinafter, the operation of the surface defect inspection apparatus having the above-described structure will be described.

First, a reticle (mast) pod in which the mask assembly 1 is stored is loaded on a loading device. The loading device opens the lid of the reticle pawl and places it on the stage unit 40 with the lower face 9 of the mask assembly 1 facing up.

Next, while the stage unit 40 is moved on the X-Y plane, the second image acquiring unit 30 acquires the image of the lower surface 9 of the mask 2 by masking it, thereby acquiring the image of (9).

Next, the mask assembly 1 is rotated 180 degrees in the loading apparatus so that the upper surface 8 of the mask assembly 1 faces upward.

Next, the alignment mark recognizing device senses the alignment mark displayed on the mask 2, and moves the stage unit 40 to align the mask 2.

Next, after the position of the pellicle frame 5 is measured using the distance measuring sensor 50, the stage unit 40 is moved to align the pellicle frame 5 in the correct position. Since the position of the pellicle frame 5 is measured since the mask assembly 1 has already been aligned but the pellicle 3 may not be attached to the correct position in the process of attaching the pellicle 3 to the mask 2, It is necessary to move the unit 40 to move the pellicle frame 5 to the reference position.

In the same way, the image of the mask top surface 8 is obtained by using the second image acquiring means 30.

Next, while the stage unit 40 is moved on the X-Y plane, the second image acquiring unit 30 causes the pellicle film 4 to be photographed to acquire the image of the pellicle film 4. [ In this process, the pellicle frame image (A) can also be secured.

Next, the value of the normal direction offset (x) between the actual pellicle frame shape A and the standard frame shape B is obtained. As described above, the offset value x can be obtained by two methods. One is a method of using the pellicle frame image (A) obtained through the second image acquiring means (30). And the other is a method of using the distance measuring sensor 50.

Next, the image of the chamfer 7 is acquired by the first image acquiring means 20. [ The controller moves the stage unit 40 on the XY plane so that the first image acquiring means 20 scans the chamfer 7 of the pellicle frame 5 and acquires an image. For example, long side straight section -> corner round section -> short side straight section -> corner round section -> opposite side long side straight section -> corner round section -> opposite short side straight section -> edge round section The stage unit 40 can be moved.

In the scan of the straight line section, the controller controls the stage unit 40 to move the pellicle frame 5 to the scan start position. Then, the stage unit 40 is linearly moved in the X-axis direction. Simultaneously, the stage unit 40 is linearly moved in the Y-axis direction according to the offset value to correct the difference between the actual pellicle frame shape A and the standard frame shape B.

The controller controls the stage unit 40 to move linearly on the XY plane so that the stage unit 40 can position the region to be photographed below the photographing region of the first image acquiring means 20. [ The mask clamp unit 43 is rotated so that the first image acquiring unit 20 and the region to be photographed can face each other. Simultaneously, the stage unit is linearly moved in the Y-axis direction according to the offset value to correct the difference between the actual pellicle frame shape A and the standard frame shape B.

Hereinafter, a method of acquiring an image of an edge portion will be described in more detail with reference to FIGS. FIG. 8 is a view for explaining the movement of the stage unit according to the difference between the center of the corner round and the rotation axis of the mask clamp, and FIG. 9 is a view for explaining the process of acquiring the edge shape by the first image acquiring unit.

8, the rotation axis a1 of the mask clamp unit 43 is located at the center of the pellicle frame 5. As shown in Fig. However, the pellicle frame 5 must be rotated with respect to the center a2 of the corner round so that the first image acquiring means 20 and the chamfer 7 at the edge which is the shooting target region can face each other.

Therefore, as shown in FIG. 9, the mask clamp unit 43 must be rotated and moved on the X-Y plane so that the first image acquiring unit 20 can acquire an image while facing the chamfer 7 at the edge.

Once the first image acquiring means 20 faces the chamfer 7 at the edge, the stage unit is linearly moved in the Y-axis direction in accordance with the offset value, and the actual pellicle frame shape A and the standard frame shape B are moved, Thereby correcting the error due to the difference between them. Since the first image acquiring means 20 faces the chamfer 7 at the corner, it can be corrected by linearly moving only in the Y direction. If the correction is not made, the corner surface is out of the depth of field of the first image acquiring means 20 and a clear image can not be obtained.

10 is a view for explaining another process in which the first image acquiring unit acquires the edge shape. According to the method of FIG. 10, the correction according to the offset value can be minimized, and the time required for image acquisition of the chamfer (or inner side) of the rounded corner of the pellicle frame 5 can be shortened.

In the above description, offset values are measured at intervals of about 3 degrees. However, in the present method, when acquiring an image of an edge portion, an offset value is obtained only for a point at which a round ends. Then, as shown in FIG. 8, the design radius of curvature of the round is drawn as two radii. One circle c1 is drawn based on a point at which the round starts, and the other circle c2 is moved by centering the obtained offset value. Then scan the corners along the trajectory of the two circles. That is, from the start point of the round to the middle point of the round, the scan is performed based on the circle c1 drawn based on the point at which the round starts, and the rest is scanned based on the circle c2 drawn based on the end point of the round.

At this time, it is possible to scan in the forward direction from the point where the round starts to the intermediate point, and to scan the reverse point from the midpoint to the end point of the round. This method can be applied to a case where the depth of field of the first image acquiring means 20 is wide enough to neglect the error occurring near the overlapping region of the circles by this method.

Next, the image of the inner surface 6 of the pellicle frame 5 is acquired by the first image acquiring means 20. [ Except that the line scan camera in which the light receiving element array 22 is arranged is used so that the central axis of the lens 21 and the central axis of the light receiving element array 22 are inclined with respect to each other, The image of the inner side 6 can be obtained in almost the same manner as the method of FIG. However, in this step, it is necessary to synchronize the movement of the line scan camera and the pellicle frame 5. Synchronization is not performed, and there is a problem that a distorted two-dimensional image is obtained.

At the time of scanning the linear section, the controller receives the trigger signal from the linear encoder which detects movement in the X-axis direction of the stage unit 40, and synchronizes the motion of the line scan camera and the pellicle frame 5.

When acquiring the image of the corner round portion, the controller receives the trigger signal from the circular encoder detecting the rotation of the stage unit 40 and synchronizes the motion of the line scan camera and the pellicle frame 5.

In this way, the image acquisition of the straight line section and the edge section is repeated to acquire the entire image of the side surface 6 in the pellicle frame 5.

Finally, when the particle is found in the inspection process, the position information in which the particle is found is stored, and the stage unit 40 is moved using the position information, So that a more detailed review image is obtained.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

For example, although the object to be inspected is described as a mask assembly, other frames that require inspection of the inner surface and the chamfer may also be the object of inspection.

1: mask structure 2: mask
3: Pellicle 4: Pellicle membrane
5: Pellicle frame 10: Support means
20: first image acquiring means 30: second image acquiring means
40: stage unit 50: distance measuring sensor

Claims (10)

A first image acquiring unit that is disposed obliquely with the object to be inspected to acquire an image of an inner surface of the object to be inspected,
A first image acquiring means for acquiring an image of the object to be inspected from the first image acquiring means so that the inner surface faces the first image acquiring means while the distance between the inner surface formed by the plane portion and the curved surface portion of the object to be inspected and the first image acquiring means is kept constant, A conveying means configured to relatively move the conveying means,
Shape information acquiring means configured to acquire planar shape (A) information of the inspection object;
And a controller configured to obtain an offset value (x) between the plane shape (A) of the inspected object and the plane shape (B) of the standard inspected object obtained by the shape information acquiring means,
Wherein the first image acquiring means includes a light receiving element array and a lens disposed between the inspected object and the light receiving element array, wherein the light receiving element arrays are arranged such that the central axis of the light receiving element array is inclined at a predetermined angle with the central axis of the lens Respectively,
And the distance between the inner surface of the object to be inspected and the first image acquiring means is set to a constant value by adjusting the distance between the inner surface of the object to be inspected and the first image acquiring means, Of the surface defects. The method according to claim 1,
Wherein the conveying means is configured to be able to perform linear motion and rotational motion on a plane, and wherein the conveying means is configured to rotate the inspected object about the rotation center of the round center of the curved surface portion of the inspected object And to rotate the inspection object and to move the inspection object in a plane. The method according to claim 1,
Wherein the shape information acquiring unit is a second image acquiring unit configured to acquire a planar image of the inspected object. The method according to claim 1,
Wherein the shape information acquiring means is a distance measuring sensor for measuring a distance from a reference surface to an outer surface of the inspection object. The method according to claim 1,
Wherein the light receiving element array of the first image acquiring means reflects the light from the lens to the light receiving element array of light incident on the light receiving element array after passing through the lens while being reflected by the inner side surface area far from the lens, (L1) is shorter than the distance (L2) from the lens to the light-receiving element array of the light incident on the light-receiving element array after being reflected by the inner surface of the lens near the distance from the lens and passing through the lens Inclined surface defect inspection apparatus. The method according to claim 1,
Wherein the controller receives the trigger signal through the encoder provided in the conveying means and controls the first image acquiring means so that the image acquisition of the first image acquiring means is synchronized with the movement of the inspected object. The method according to claim 6,
Wherein the control unit controls the first image acquiring unit by receiving a trigger signal through a linear encoder that senses linear movement of the conveying unit when inspecting the long side and the short side of the inspected object and controls the first image acquiring unit when the edge of the inspected object is inspected, And receives the trigger signal through a rotary encoder for detecting the rotation and controls the first image acquiring means. The method of claim 3,
And the second image acquiring unit is disposed perpendicularly to the object to be inspected. The method according to claim 1,
Wherein the inner surface of the object to be inspected includes a curved surface portion,
The controller measures an offset value (x) of a point at which the curved surface finishes, and has a circle having a radius of curvature of a curved surface portion of a standard inspection object as a radius, and the other circle is centered by an offset value of a point And then drives the conveying means on the basis of the trajectory of the two circles. 10. The method of claim 9,
Wherein the controller rotates the conveying means in the forward direction from the point where the curved surface starts to the central portion of the curved surface portion and rotates the conveying means in the reverse direction from the central portion of the curved surface portion to the point where the curved surface portion ends.

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