KR102119492B1 - Surface defect inspection apparatus - Google Patents

Abstract

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 to a contaminant. The present invention is configured to acquire a surface image of an object to be inspected with a transparent film attached to a support frame, and to move and rotate the object in the X-axis or Y-axis direction relative to the image acquisition means. Distance measuring means configured to adjust the distance between the transfer means, a distance measuring sensor for generating an electrical signal according to the distance between the upper surface of the transparent film and the reference surface of the image acquisition means, and the reference surface of the transparent film and the image acquisition means And, based on the electrical signal received from the distance measurement sensor, the distance control means is controlled so that the focus of the image acquisition means is located on at least one of the upper and lower surfaces of the transparent film, and the image of the contaminant at the position is obtained. It provides a surface defect inspection apparatus comprising a controller configured to control the image acquisition means to obtain. Surface defect inspection apparatus according to the present invention, while checking in real time the height of the surface of the transparent film, such as a pellicle film, it is possible to check which side of the pellicle film is attached, so that the adhesion of the contaminants more accurately than conventional devices It has the advantage of being able to identify the side.

Description

Surface defect inspection apparatus

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 contaminated.

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

When dust is attached 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 semiconductor devices or liquid crystal displays.

Therefore, these operations are usually performed in a clean room, but since dust is also present in the clean room, a method of attaching a pellicle, a thin film through which light can pass, has been 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 to the pellicle film, and in lithography, the focus is coincident on the pattern of the mask, so the dust attached to the pellicle film is not focused and is not transferred to the pattern. There is this.

However, the dust attached to the pellicle film can be divided into the dust attached to the lower surface (inner surface) facing the mask of the pellicle film and the dust attached to the upper surface (outer surface), and the dust attached to the lower surface falls off the mask in the lithography process. Since there is a problem that it may cause defects, it is necessary to distinguish whether the attached dust is dust attached to the lower surface of the pellicle film or dust attached to the upper surface.

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

In addition, the range in which pellicles can be attached is limited due to the recent high integration of patterns, and a process of inspecting whether the pellicles are rotated or shifted after attaching the pellicles to the mask is required. In addition, for particle inspection, it is necessary to confirm the pellicle attachment position in advance.

In a conventional inspection method, a distance between a pellicle frame and a mask is measured using a caliper or a displacement sensor, etc., and the attachment position of the pellicle is examined.

For example, Patent Publication No. 2003-0060199 discloses a rotator installed on a work table, a measuring device installed at a different position on the work table, and equipped with a caliper, and installed on another position on the work table and airing the meter. A test method using an inspection device for measuring the rotational state of a pellicle of a mask having a measuring device fixed valve capable of being moved and fixed by driving of a cylinder, the first method of loading a mask with a pellicle on a mount of the rotator step; A second step of unlocking the meter fixing valve to lock the meter fixing valve after bringing the meter into close contact with the rotator; A third step of measuring the distance between the edge of the top of the mask and the pellicle frame using the caliper of the meter; A fourth step of measuring a distance between the edge of the lower part of the mask and the pellicle frame using the caliper of the measuring device; And a fifth step of unlocking the meter fixing valve to separate the meter from the rotator.

In addition, in Patent Publication No. 10-2010-0134453, a method for measuring a pellicle attachment position for measuring an attachment position of a pellicle attached to an upper surface of a photomask, wherein the mobile device faces the first and second sides of the photomask, respectively. Placing it in an initial position; Moving the moving device toward the photomask; Stopping the moving device when the moving device 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 at the moving distance. .

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

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

An object of the present invention is to provide a novel surface defect inspection apparatus capable of accurately confirming which surface of a pellicle film is attached to the above-mentioned problems.

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

In order to achieve the above object, the present invention is 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 distance measuring sensor for generating an electric signal according to a distance between a transfer means configured to move and rotate relative to the upper surface of the transparent film and a reference surface of the image acquisition means, and a distance between the transparent film and the reference surface of the image acquisition means The distance adjusting means is configured to control the distance adjusting means so that the focus of the image acquisition means is located on at least one of the upper and lower surfaces of the transparent film based on the electric signal received from the distance measuring sensor. It provides a surface defect inspection apparatus including a controller configured to control the image acquisition means to obtain an image of the contaminants in the.

The surface defect inspection apparatus according to the present invention can confirm which surface of the pellicle film is attached to the pellicle film while checking the height of the surface of the transparent film such as the pellicle film in real time. It has the advantage of being able to identify the side.

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.
FIG. 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 processing unit shown in FIG. 4.
6 is a view for explaining a method for obtaining corner coordinate values.

Hereinafter, a preferred embodiment according to the present invention will be described in detail. The following examples are provided as examples to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. 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 an embodiment of a surface defect inspection apparatus according to the present invention. As shown in Figure 1, one embodiment of the surface defect inspection apparatus according to the present invention is a support structure 10, an image acquisition means 20, a distance control means 30, a stage unit that is a transfer means 40, It includes a distance measuring sensor 50 and a controller (not shown).

The surface defect inspection apparatus is an image acquiring means using scattering characteristics of light on which surface of the transparent film the contaminants such as particles present on the surface of the transparent film of the inspection object moving on the XY plane by the transfer means 40 ( It is a device to check through 20). The object to be inspected can 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 an inspection object. The surface defect inspection apparatus according to the present invention can inspect not only the position of the contaminant on the X-Y plane, but also which side of the transparent film.

2 is a perspective view of the mask assembly. 2, the mask assembly 1 includes a mask 2 and a pellicle 3 attached to the top surface of the mask 2. The pellicle 3 includes a pellicle film 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 an octagonal or circular frame is 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 acquiring means 20 may be composed of one optical system capable of acquiring images of various resolutions, but in this embodiment, as shown in FIG. 1, includes two optical systems. That is, the contaminants attached to the low-resolution first image acquisition means 22 and the pellicle film 4 for correcting the position of the pellicle 3 and obtaining coordinates of the contaminants attached to the pellicle film 4 are pellicle films. A high-resolution second image acquiring 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 lighting may include coaxial lighting (reflective lighting) and transmissive lighting. The first image acquiring means 22 is arranged such that its central axis is orthogonal to the mask assembly 1 for acquiring a plane image.

Like the first image acquisition means 22, the second image acquisition means 24 may also include a camera, a lens, a lens holder, and lighting. In addition, the second image acquiring means 24 is also arranged such that its central axis is orthogonal to the mask assembly 1 for acquiring a flat image.

The distance adjusting means 30 serves to adjust the distance between the pellicle film 3 and the reference plane of the second image acquiring means 24 by moving the second image acquiring means 24 in the Z-axis direction. The reference plane may be located on 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 the surface image of the required position of the mask assembly (1). The transfer means 40 may move the mask assembly 1 or, conversely, the first image acquisition means 22 and the second image acquisition means 24. In this embodiment, the first image acquiring means 22 and the second image acquiring means 24 are fixed to the support means 10, and the surface of the mask assembly 1 is used using a stage unit that is a conveying means 40. A method of acquiring images while moving within the depth of field of the first image acquisition means 22 and the second image acquisition means 24 was used.

FIG. 3 is a plan view of the stage unit shown in FIG. 1. As illustrated in FIG. 3, the stage unit 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 installed on the second stage 42 and rotates around a rotation axis orthogonal to the X-Y plane.

Again, the distance measuring sensor 50 will be described with reference to FIG. 1. The distance measurement sensor 50 serves to measure the distance between the top 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 measurement 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 controlled by the distance adjusting means 30.

4 is a block diagram of a controller. 4, the controller 60 includes a signal receiving unit 61, a signal processing unit 62, a control signal generation unit 63, a control signal transmission unit 64 and a memory 65. The signal receiving unit 61 receives a signal regarding 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 of the mask assembly and the rotation angle values 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 adjustment means 30. Also, a video signal is received from the video acquisition means 20.

5 is a block diagram of the signal processing unit shown in FIG. 4. As shown in FIG. 5, the signal processing unit 62 includes an edge coordinate calculation unit 621, a correction value calculation unit 622, a pollutant detection unit 623, a pellicle film distance calculation unit 624, and a pollutant attachment surface determination unit 625. The signal processing unit 62 processes various signals received from the signal receiving unit 61.

The corner coordinate calculator 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 the X and Y coordinate values received from the transfer means 40 Using, calculate the coordinate value of the center point of the corner. For example, as shown in FIG. 6, the corner coordinate calculating unit 621 uses a point 9 where the vertical line 7 and the horizontal line 8 that extend the inner surface of the pellicle frame 5 intersect as a center point of the corner. Finding, and using the coordinate value received from the transfer means 40, it is possible to calculate the coordinate value of this center point. The coordinate values of the center points are stored in the memory 65.

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

The pollutant detection unit 623 analyzes the image of the pellicle film 4 obtained in the process of scanning the mask assembly 1 to detect pollutants such as particles. For example, a particle may be detected using a difference in brightness of each location of the image. In the case of using a dark field method that irradiates light obliquely and acquires an image with reflected light, the light is reflected from the particles and the pellicle film is transmitted, so the particles appear bright, and on the contrary, the image is made using vertically transmitted light. When using the method to acquire the particles appear dark.

The pellicle film distance calculator 624 calculates a distance from the reference surface to the top surface of the pellicle film 4 using the electrical signal received from the distance measurement sensor 50. Even at the same position, the height of the pellicle film 4 continues to change due to vibration in the transport process. Therefore, the pellicle film distance calculator 624 calculates the distance between the upper surface and the reference surface of the pellicle film 4 at the moment of acquiring the image using the second image acquisition means 24.

The contaminant attaching surface determination unit 625 uses a high-resolution image of the contaminant to determine which of the upper and lower surfaces of the pellicle film 4 is attached. For example, when the image photographed while the camera is focused on the upper surface is clear, it is determined as a particle attached to the upper surface, and when it is cloudy, it is determined as a particle attached to the lower surface. When detailed inspection is required, the image captured while the camera is focused on the lower surface is further analyzed. The position of the lower surface can be calculated using, for example, the position of the upper surface and the thickness value of the pellicle film 4 stored in the memory 65. In this case, on the contrary, if the captured image is clear, it is determined as a particle attached to the lower surface, and when it is cloudy, it is determined as a particle attached to the upper surface. If two judgment results for the same particle do not match, re-inspection can be performed.

Referring to FIG. 4 again, the control signal generation unit 63 receives the calculation result from the signal processing unit 62, and controls the transfer means 40, the distance adjustment means 30, and the image acquisition means 20. To generate a control signal.

The control signal transmission unit 64 transmits the control signal generated by the control signal generation unit 63 to the transfer means 40, the distance adjustment means 30, and the image acquisition means 20.

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

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

First, a reticle (mast) pod in which the mask assembly 1 is stored is loaded in a loading device. The loading device opens the lid of the reticle pod and places it on the stage unit so that the lower surface of the mask assembly 1 faces upward.

Next, while moving the stage unit on the X-Y plane, the first image acquisition means 22 captures 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 device, so that the top surface 8 of the mask assembly 1 faces upward.

Next, the alignment mark recognition device senses 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, as shown in FIG. 6, using the first image acquisition means 22, images of four corners of the pellicle frame 5 are acquired. .

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

Next, the controller 60 controls the transfer means 40 to place the pellicle 3 in place for inspection. The mask assembly 1 is already aligned, but in the process of attaching the pellicle 3 to the mask 2, the pellicle 3 may not be attached to the reference position, so that it is based on the corner coordinate values 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 the contaminants from the scanned image of the pellicle film 4, obtains and stores the coordinate values of the contaminants.

Next, the controller 60 uses the coordinate values of the pollutants to obtain a high-resolution image of the pollutants detected through the first image acquisition means 22, and pollutes the photographing area of the second image acquisition means 24 The transport means 40 are controlled so that the material is placed.

Next, after measuring the distance from the reference surface of the second image acquisition means 24 to the upper surface of the pellicle film 4 using the distance measuring sensor 50, the pellicle film 4 is measured using the distance adjusting means 30. The height of the camera of the second image acquiring means 24 is adjusted so that the second image acquiring means 24 focuses on the upper surface of the.

Next, a high-resolution image of the pollutant is acquired using the second image acquisition means 24. If the image of the contaminant is clear, it is determined as a contaminant located on the top surface of the pellicle film 4.

Next, after measuring the distance to the top 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 Adjust the height of the camera of the second image acquisition means 24 so that the focus of the.

Next, a high-resolution image of the pollutant is acquired using the second image acquisition means 24. If the image of the contaminant is not clear, it is determined as a contaminant located on the top surface of the pellicle film 4. If the image of the contaminants is clear, repeat the above steps to perform the re-inspection.

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

The embodiments described above are merely illustrative of preferred embodiments of the present invention, and the scope of the present invention is not limited to the described embodiments, and those skilled in the art within the technical spirit and claims of the present invention. Various changes, modifications, or substitutions may be made by, and such embodiments should be understood to be within the scope of the present invention.

1: Mask structure
2: Mask
3: pellicle
4: pellicle membrane
5: pellicle frame
10: support means
22: first image acquisition means
24: second image acquisition means
30: distance adjustment means
40: conveying means
50: distance measuring sensor
60: controller

Claims (7)

An image acquiring means configured to acquire a surface image of an inspection object having a transparent film attached to a support frame,
Transfer means configured to move and rotate the inspection object relative to the image acquisition means in the X-axis or Y-axis direction,
A distance measuring sensor generating an electrical signal according to the distance between the upper surface of the transparent film and the reference surface of the image acquisition means;
Distance control means configured to adjust the distance between the transparent film and the reference surface of the image acquisition means,
Control the distance adjusting means so that the focus of the image acquisition means is located on at least one of the upper and lower surfaces 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 controller,
The distance measuring sensor receives an electrical signal according to the distance between the upper surface of the transparent film and the reference surface of the image acquiring means, and receives signals regarding X, Y coordinates and rotation angles of the inspection object from the conveying means, and the image. A signal receiving unit for receiving the image signal from the acquisition means,
A signal processor which processes signals received from the signal receiver,
A control signal generation unit receiving a calculation result from the signal processing unit, and generating a control signal capable of controlling the transfer means, the distance adjustment means, and the image acquisition means;
And a control signal transmitter for transmitting the control signal generated by the control signal generator to the transfer means, the distance adjusting means, and the image acquisition means. delete According to claim 1,
The signal processing unit,
And a corner coordinate calculating unit which finds a center point of the corner of the support frame from the image signal and calculates a coordinate value of the center point of the corner using X and Y coordinate values received from the transfer means. According to claim 3,
The signal processing unit,
A surface including a correction value calculation unit for calculating a correction value used for position correction for arranging the inspection object at a correct position for surface inspection by using coordinate values of the center points of the four corners calculated by the corner coordinate calculation unit. Defect inspection device. According to claim 1,
The signal processing unit,
When the image captured in the state of focusing the image acquisition means on the upper surface of the transparent film is clear, it is judged as a contaminant attached to the upper surface, and when it is cloudy, it is judged as a contaminant attached to the lower surface. Surface defect inspection device comprising a part. The method of claim 5,
The contaminant attachment surface determination unit,
A surface defect inspection device that determines that the image captured in the state where the image acquisition means is focused on the lower surface of the transparent film is contaminant attached to the lower surface, and when it is cloudy, determines that it is a contaminant attached to the upper surface. According to claim 1,
The object to be inspected is a pellicle or a surface defect inspection device which is a pellicle attached mask.

Images