KR20190100616A - Surface defect inspection apparatus - Google Patents

Abstract

The present invention relates to a surface defect inspection apparatus, and more specifically, to a surface defect inspection apparatus capable of checking whether contaminants adhere to upper and lower surfaces of a transparent thin film such as a pellicle. The present invention provides the surface defect inspection apparatus comprising: an image acquisition means configured to acquire a surface image of an object to be inspected having a transparent film attached to a support frame; a transfer means configured to relatively move and rotate the object to be inspected in the X- or Y-axis direction with respect to the image acquisition means; a distance measuring sensor generating an electric signal according to a distance between an upper surface of the transparent film and a reference surface of the image acquisition means; a distance adjusting means configured to adjust a distance between the transparent film and the reference surface of the image acquisition means; and a controller configured to control the distance adjusting means such that a focal point of the image acquisition means is positioned on the upper surface and/or the lower surface of the transparent film based on the electric signal received from the distance measuring sensor and to control the image acquisition means such that the image acquisition means acquires an image of contaminants in the position. The surface defect inspection apparatus, according to the present invention, can check to which side of the pellicle the contaminants are attached while checking the height of the surface of the transparent film such as the pellicle, thereby more accurately confirming a surface to which the contaminants are attached as compared to the conventional device.

Description

Surface defect inspection apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus, and more particularly, to a surface defect inspection apparatus capable of confirming which of the upper and lower surfaces of a transparent thin film, such as a pellicle film, is attached.

In the manufacture of a semiconductor device or a liquid crystal display panel, a method called photolithography is used when patterning a semiconductor wafer or a liquid crystal substrate. In photolithography, a mask is used as an original plate of patterning, and the pattern on the mask is transferred to a wafer or a liquid crystal substrate.

When dust adheres to the mask, light is absorbed or reflected by the dust, and thus the transferred pattern is damaged, resulting in a decrease in performance or yield of a semiconductor device, a liquid crystal display panel, or the like.

Therefore, these operations are usually performed in a clean room, but since dust exists in the clean room, a method of attaching a pellicle, which is a thin film through which light can pass, is performed to prevent dust from adhering to the mask surface.

In this case, the dust is not directly attached to the surface of the mask, but is attached on the pellicle film, and in lithography, since the focus is matched on the pattern of the mask, the dust attached to the pellicle film is not in focus and is not transferred to the pattern. There is this.

However, dust attached to the pellicle film can be classified into dust attached to the lower surface (inner side) facing the mask of the pellicle film and dust attached to the upper surface (outer side). Since there is a problem that can cause a defect, it is necessary to distinguish whether the dust adhered to the lower surface of the pellicle film or the dust attached to the upper surface.

Conventionally, if the dust is clearly seen in the image obtained by the illumination located at the bottom of the mask assembly, which is a mask with a pellicle film, it is determined that the dust is located at the lower surface of the pellicle film, and the dust in the image acquired by the illumination located at the top When was clearly seen, a method of judging that it was dust located on the upper surface of the pellicle film was used. However, since the thin pellicle film vibrates in the process of moving the mask assembly for inspection of the mask assembly, is it not clear that the dust is clearly seen in the acquired image depending on the type of the adhesion surface of the dust, or the pellicle film and the camera due to the vibration of the pellicle film? There was a problem that it is difficult to determine clearly whether the distance between them is changed and out of focus.

In addition, in recent years, the integration of the pellicle is limited due to the high integration of the pattern, and after the pellicle is attached to the mask, a process of inspecting the rotation and shift of the pellicle is necessary. In addition, for particle inspection, it is necessary to confirm the attachment position of the pellicle in advance.

In the conventional inspection method, the position of the pellicle was examined by measuring the distance between the pellicle frame and the mask using a caliper or a displacement sensor.

For example, Korean Patent Laid-Open Publication No. 2003-0060199 includes a rotator installed on a work table, a measuring instrument installed at another position on the work table and mounted with a caliper, and an air measuring apparatus installed at another position on the work table. An inspection method using an inspection apparatus for measuring a pellicle rotation state of a mask having a measuring device holding valve which can be moved and fixed by driving a cylinder, comprising: a first method of loading a mask with a pellicle onto a mounting table of the rotator; step; A second step of unlocking the meter holding valve to lock the meter holding valve after the meter is in close contact with the rotator; A third step of measuring a distance between an edge of an upper portion of a mask and a pellicle frame by using a caliper of the measuring device; A fourth step of measuring a distance between an edge of the lower part of the mask and the pellicle frame by using a caliper of the measuring device; And a fifth step of unlocking the measuring device holding valve to separate the measuring device from the rotator, wherein the inspection method for measuring the pellicle rotation of the mask is disclosed.

In addition, Patent Publication No. 10-2010-0134453 is a pellicle attachment position measuring method for measuring the attachment position of the pellicle attached to the upper surface of the photomask, the moving device facing the first side and the second side of the photomask, respectively Placing it in an initial position; Moving the moving device toward the photomask; Stopping the mover when the mover contacts the pellicle; Calculating a moving distance of the stationary mobile device; And calculating a distance between the edge of the photomask and the pellicle by subtracting the distance from the edge of the photomask to the initial position in the moving distance. .

However, the pellicle frame has a problem that it is difficult to accurately measure the attachment position of the pellicle because the long side is bent inward due to the tension of the pellicle film.

Patent Publication 10-2010-0134453 Patent Application Publication No. 2003-0060199

SUMMARY OF THE INVENTION The present invention aims to provide a novel surface defect inspection apparatus capable of accurately identifying which surface of a pellicle film is attached to a pellicle film.

In addition, some embodiments aim to provide a surface defect inspection apparatus capable of accurately measuring the attachment position of the pellicle.

In order to achieve the above object, the present invention provides an image acquisition means configured to acquire a surface image of an inspection object having a transparent film attached to a support frame, and the inspection object in the X-axis or Y-axis direction with respect to the image acquisition means. A conveying means configured to move and rotate relative to each other, a distance measuring sensor for generating an electric signal according to a distance between an upper surface of the transparent film and a reference plane of the image acquisition means, and a distance between the transparent film and a reference plane of the image acquisition means. And a distance adjusting means configured to adjust the distance control means such that the focus of the image acquisition means is located on at least one of an upper surface and a lower surface of the transparent film based on the electrical signal received from the distance measuring sensor. A controller configured to control the image acquisition means to acquire an image of a contaminant in It provides a surface defect inspection apparatus comprising.

The surface defect inspection apparatus according to the present invention can confirm which side of the pellicle membrane is attached to the contaminant, while confirming the height of the surface of the transparent membrane such as the pellicle membrane in real time, so that the contaminant adheres more accurately than the conventional apparatus. The advantage is that you can see the side.

1 is a perspective view of one embodiment of a surface defect inspection apparatus according to the present invention.
2 is a perspective view of a mask assembly.
3 is a plan view of the stage unit shown in FIG. 1.
4 is a block diagram of a controller.
5 is a block diagram of the signal processor shown in FIG. 4.
6 is a view for explaining a method of obtaining corner coordinate values.

Hereinafter, the preferred embodiment according to the present invention will be described in detail. The following embodiments are provided as examples to ensure that the spirit of the present invention to those skilled in the art will fully convey. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms.

1 is a perspective view of one embodiment of a surface defect inspection apparatus according to the present invention. As shown in FIG. 1, one embodiment of the surface defect inspection apparatus according to the present invention includes a support unit 10, an image acquisition unit 20, a distance adjusting unit 30, and a transfer unit 40. Distance measuring sensor 50 and a controller (not shown).

The surface defect inspection apparatus uses image scattering means using light scattering characteristics to determine on which surface of the transparent film contaminants such as particles existing on the surface of the transparent film of the inspection object moved on the XY plane by the transfer means 40 ( It is a device to check through 20). The inspected object may be a variety of articles having a support frame and a thin film attached to the support frame. For example, the inspection object may be a pellicle or a mask to which the pellicle is attached, that is, the mask assembly 1. Hereinafter, the mask assembly 1 will be described as an example of the inspection object. The surface defect inspection apparatus according to the present invention can inspect not only the position on the X-Y plane of the contaminant but also on which side of the transparent film.

2 is a perspective view of a mask assembly. As shown in FIG. 2, the mask assembly 1 comprises a mask 2 and a pellicle 3 attached to an 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 an adhesive layer (not shown) formed on the lower surface of the pellicle frame 5. The pellicle frame 5 is usually in the form of a square frame with rounded corners, but octagonal or circular frames are also used. The pellicle frame 5 also differs in size depending on its use. For example, large pellicles are used in the LCD manufacturing process and relatively small pellicles are used in the semiconductor process.

The image acquisition unit 20 may be formed of one optical system capable of acquiring images of various resolutions. However, in the present embodiment, as shown in FIG. 1, the image acquisition unit 20 includes two optical systems. That is, the low resolution first image acquisition means 22 and the contaminants adhered to the pellicle film 4 are used to correct the position of the pellicle 3 and to obtain the coordinates of the contaminants attached to the pellicle film 4. A second high-resolution image acquisition means 24 for checking whether it is attached to the upper surface or the lower surface of (4) is separately provided.

The first image acquisition means 22 may include a camera, a lens, a lens holder, lighting, and the like. The illumination may include coaxial illumination (reflective illumination) and transmitted illumination. The first image acquisition means 22 is arranged such that its central axis is orthogonal to the mask assembly 1 for planar image acquisition.

Like the first image acquisition means 22, the second image acquisition means 24 may also include a camera, a lens, a lens holder, illumination, and the like. The second image acquisition means 24 is also arranged such that its central axis is orthogonal to the mask assembly 1 for planar image acquisition.

The distance adjusting means 30 serves to adjust the distance between the pellicle film 3 and the reference plane of the second image acquisition means 24 by moving the second image acquisition means 24 in the Z-axis direction. The reference plane may be located in the camera of the second image acquisition means 24.

The transfer means 40 moves the mask assembly 1 relative to the first image acquisition means 22 and the second image acquisition means 24, so that the first image acquisition means 22 and the second image acquisition means ( 24) serves to acquire a surface image of the required position of the mask assembly 1. The transfer means 40 may move the mask assembly 1 or, conversely, move the first image acquisition means 22 and the second image acquisition means 24. In this embodiment, the first image acquisition means 22 and the second image acquisition means 24 are fixed to the support means 10, and the surface of the mask assembly 1 is fixed by using a stage unit which is the transfer means 40. A method of acquiring an image while moving within the depth of field of the first image acquiring means 22 and the second image acquiring means 24 was used.

3 is a plan view of the stage unit shown in FIG. 1. As shown in FIG. 3, the stage unit includes a first stage 41, 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 in the support means 10. The second stage 42 moves along the guide rail 44 in the Y-axis direction provided in the first stage 41. The mask clamp unit 43 is installed on the second stage 42 and rotates about a rotation axis orthogonal to the X-Y plane.

Again, referring to FIG. 1, the distance measuring sensor 50 will be described. The distance measuring sensor 50 measures the distance between the upper surface of the pellicle film 4 of the mask assembly 1 fixed to the mask clamp unit 43 of the stage unit and the reference surface of the second image acquisition means 24. Do it. For example, the distance measuring sensor 50 may be installed in the camera of the second image acquisition means 24. The distance measuring sensor 50 may be a laser displacement sensor. The distance between the reference surface of the second image acquisition means 24 and the top surface of the pellicle film 4 is adjusted by the distance adjusting means 30.

4 is a block diagram of a controller. As shown in FIG. 4, the controller 60 includes a signal receiver 61, a signal processor 62, a control signal generator 63, a control signal transmitter 64, and a memory 65. The signal receiver 61 receives a signal relating to the distance between the upper surface of the pellicle film 4 and the reference surface from the distance measuring sensor 50. Then, the X and Y coordinate values and rotation angle values of the mask assembly are received from the transfer means 40. In addition, the Z coordinate value of the second image acquisition means 24 is also received from the distance adjusting means 30. Also, an image signal is also received from the image acquisition means 20.

5 is a block diagram of the signal processor shown in FIG. 4. As shown in FIG. 5, the signal processor 62 includes an edge coordinate calculator 621, a correction value calculator 622, a pollutant detector 623, a pellicle film distance calculator 624, and a pollutant adhesion surface determiner. 625. The signal processor 62 processes various signals received from the signal receiver 61.

The corner coordinate calculation unit 621 processes the corner image of the pellicle 3 received from the image acquisition means 20 to find the center point of the corner on the image, and receives the X and Y coordinate values received from the transfer means 40. Calculate the coordinate value of the center point of the corner using. For example, as shown in FIG. 6, the edge coordinate calculating unit 621 uses the point 9 at which the vertical line 7 extending the inner surface of the pellicle frame 5 and the horizontal line 8 intersect as the center point of the corner. The coordinate value of the center point can be calculated by using the coordinate value received from the transport means 40. The coordinate values of the center points are stored in the memory 65.

The correction value calculation unit 622 uses the coordinate values of the center points of the four corners to position the mask assembly 1 in the X-axis direction and to position the pellicle 3 in position for the surface inspection of the pellicle 3. Calculate how much to move in the Y-axis direction and how much to rotate.

The contaminant detecting unit 623 analyzes an image of the pellicle film 4 obtained in the process of scanning the mask assembly 1 to detect contaminants such as particles. For example, particles may be detected by using brightness differences for each location of an image. In the case of using a dark field method of irradiating light obliquely and acquiring an image with reflected light, the particle appears bright because light is reflected from the particle and the pellicle film is transmitted. Particles look dark when using the method of obtaining.

The pellicle film distance calculating unit 624 calculates the distance from the reference plane to the upper surface of the pellicle film 4 using the electric signal received from the distance measuring sensor 50. Even at the same position, the height of the pellicle film 4 continues to change due to vibration in the conveying process. Accordingly, the pellicle film distance calculating unit 624 calculates the distance between the reference surface and the upper surface of the pellicle film 4 at the moment of obtaining the image using the second image acquisition means 24.

The contaminant attaching surface determining unit 625 determines whether the contaminant is attached to the upper and lower surfaces of the pellicle film 4 by using the high resolution image of the contaminant. For example, when the image captured while the camera focuses on the upper surface is clear, it is determined to be a particle attached to the upper surface, and when the image is blurred, the particle is attached to the lower surface. If close inspection is required, further analysis of the image taken while the camera is focused on the bottom surface is performed. The position of the lower surface can be calculated using, for example, the position of the upper surface and the pellicle film 4 thickness value stored in the memory 65. In this case, on the contrary, when the photographed image is clear, it is determined as particles attached to the lower surface, and when it is blurred, it is determined as particles attached to the upper surface. If two judgment results about the same particle do not coincide with each other, a retest can be performed.

Referring back to FIG. 4, the control signal generator 63 receives the calculation result from the signal processor 62 to control the transfer means 40, the distance adjusting means 30, and the image acquisition means 20. To generate a control signal.

The control signal transmitter 64 transmits the control signal generated by the control signal generator 63 to the transfer means 40, the distance adjusting means 30, and the image acquisition means 20.

In addition, the surface defect inspection apparatus loads the mask assembly 1 to be inspected, and an alignment mark recognition device for detecting an alignment mark displayed on the mask 2 for aligning the mask 2 and a loading device (not shown) for flipping. It may further include a frame image acquisition means (not shown) for obtaining an image of the entire pellicle frame 5 to recognize the size of the pellicle frame (5).

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

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

Next, while the stage unit is moved on the X-Y plane, the first image acquisition means 22 photographs the lower surface of the mask 2 to obtain an image of the lower surface of the mask.

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 recognition device detects the alignment mark displayed on the mask 2, and moves the stage unit to align the mask 2.

Next, while moving the mask assembly 1 using the stage unit, the first image acquisition means 22 is used to acquire images of four corners of the pellicle frame 5 as shown in FIG. 6. .

Next, the coordinate values of the corners of the pellicle frame 5 are obtained by using the image acquired by the first image acquisition means 22. For example, the coordinates of the intersection points are obtained by finding a point where the extension lines of the inner surface of the pellicle frame intersect in the obtained corner images. The coordinate value controls the transfer means 40 so that the intersection point is located at the center of the image acquired by the first image acquisition means 22, and the movement distance in the X and Y axis directions of the transfer means 40 at this time. It can be obtained by obtaining the X, Y coordinate value from.

The controller 60 then controls the transfer means 40 to place the pellicle 3 in place for inspection. Although the mask assembly 1 has already been aligned, the pellicle 3 may not be attached to the reference position in the process of attaching the pellicle 3 to the mask 2, based on the edge coordinate value of the pellicle frame 5. It is necessary to move and rotate the stage unit to move the pellicle frame 5 to the correct position for inspection.

Next, the mask assembly 1 is moved in the X-axis and Y-axis directions so that the first image acquisition means 22 can scan the pellicle film 4. At this time, the controller 60 detects a contaminant in the scan image of the pellicle film 4, obtains and stores a coordinate value of the contaminant.

Next, the controller 60 contaminates the photographing area of the second image acquiring means 24 by using the coordinate values of the contaminants in order to obtain a high resolution image of the contaminant detected through the first image acquiring means 22. The transport means 40 is controlled so that the material is disposed.

Next, the distance from the reference surface of the second image acquisition means 24 to the upper surface of the pellicle film 4 is measured using the distance measuring sensor 50, and then the pellicle film 4 is formed using the distance adjusting means 30. The height of the camera of the second image acquisition means 24 is adjusted so that the top of the second image acquisition means 24 is in focus.

Next, a high resolution image of the pollutant is obtained by using the second image acquisition means 24. If the image of the contaminant is clear, it is determined that the contaminant is located on the upper surface of the pellicle film 4.

Next, after measuring the distance to the upper surface of the pellicle film 4 using the distance measuring sensor 50, the second image acquisition means 24 on the lower surface of the pellicle film 4 using the distance adjusting means 30 The height of the camera of the second image acquisition means 24 is adjusted to be in focus.

Next, a high resolution image of the pollutant is obtained by using the second image acquisition means 24. If the image of the contaminant is not clear, the contaminant located on the upper surface of the pellicle film 4 is determined. If the contaminant image is clear, repeat the above steps and retest.

Next, the inspection is repeated on which surface of the pellicle film 4 is attached while moving the stage unit on the X-Y plane according to the coordinate value of the contaminant.

The embodiments described above are merely illustrative of the preferred embodiments of the present invention, the scope of the present invention is not limited to the described embodiments, those skilled in the art within the spirit and claims of the present invention It will be understood that various changes, modifications, or substitutions may be made thereto, and such embodiments are to be understood as being within the scope of the present invention.

1: mask structure
2: mask
3: pellicle
4: pellicle membrane
5: pellicle frame
10: supporting means
22: first image acquisition means
24: second image acquisition means
30: distance adjusting means
40: transfer means
50: distance measuring sensor
60: controller

Claims (7)

Image acquisition means configured to acquire a surface image of the inspection object having a transparent film attached to the support frame;
Transfer means configured to relatively move and rotate the inspection object in the X-axis or Y-axis direction with respect to the image acquisition means;
A distance measuring sensor for generating an electric signal according to a distance between an upper surface of the transparent film and a reference plane of the image acquisition means;
Distance adjusting means configured to adjust a distance between the transparent film and a reference plane of the image acquisition means;
Control the distance adjusting means such that the focal point of the image acquisition means is located on at least one of an upper surface and a lower surface of the transparent film based on the electrical signal received from the distance measuring sensor, and acquire an image of the contaminant at the position And a controller configured to control the image acquisition means. The method of claim 1,
The controller
Receives an electrical signal according to the distance between the upper surface of the transparent film and the reference surface of the image acquisition means from a distance measuring sensor, receives a signal about the X, Y coordinates and the rotation angle of the inspection object from the transfer means, from the image acquisition means A signal receiver for receiving a video signal;
A signal processor for processing signals received from the signal receiver;
A control signal generation unit which receives a result of the calculation in the signal processing unit and generates a control signal for controlling the transfer means, distance adjusting means, and image acquisition means;
And a control signal transmitter for transmitting the control signal generated by the control signal generator to the transfer means, distance adjusting means, and image acquisition means. The method of claim 2,
The signal processing unit,
And a corner coordinate calculator for finding a center point of the corner of the support frame from the image signal and calculating coordinate values of the center point of the corner by using the X and Y coordinate values received from the transfer means. The method of claim 3,
The signal processing unit,
Surface defect including a correction value calculator for calculating a correction value used for position correction for positioning the inspection object in the correct position for the surface inspection using the coordinate values of the center point of the four corners calculated by the corner coordinate calculator Inspection device. The method of claim 2,
The signal processing unit,
If the image captured with the focus of the image acquisition means on the upper surface of the transparent film is clear, it is determined as a contaminant attached to the upper surface. Surface defect inspection device. The method of claim 5,
The pollutant adhesion surface determination unit,
The surface defect inspection apparatus, if the image taken with the focus of the image acquisition means on the lower surface of the transparent film is clear, it is determined as a contaminant attached to the lower surface, and if it is cloudy, it is determined as a contaminant attached to the upper surface. The method of claim 1,
The inspection object is a surface defect inspection apparatus is a pellicle or a mask with a pellicle attached.

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