KR20210096993A - Sample inspection apparatus and sample inspection method - Google Patents

Abstract

According to one embodiment, a sample testing apparatus includes a vision assembly that is relatively movable along a first straight line with respect to a sample, and tests the sample by acquiring an image of the sample using a time delay integration method. The vision assembly comprises: an optical system having an optical axis inclined at a first tilting angle with respect to a direction perpendicular to a reference plane of the sample on a first virtual surface including the first straight line; and a camera sensor disposed to be inclined at a second tilting angle with respect to a second virtual surface perpendicular to the optical axis. Through this configuration, high resolution, high depth of focus and normal image aspect ratio can be obtained at the same time.

Description

Sample testing device and sample testing method

The following description relates to a sample testing device and a sample testing method.

The sample inspection device is a device that can check various states including flatness of a sample through vision. Here, the sample may include various objects such as an image sensor of a portable terminal.

In order to improve the accuracy of inspection, a high resolution optical system is required. However, as there is a limit to the resolution of the optical system, there are attempts to improve the precision of the examination, such as photographing an object locally and synthesizing it.

For example, in order to precisely observe a sample, a sample inspection apparatus having an optical system having a high resolution may be used. However, an optical system having a high resolution has a short depth of focus due to its optical characteristics. When the depth of focus is short, the area defocused from the focal plane is defocused, making it difficult to check the shape. Therefore, when an optical system having high resolution (ie, an optical system having a short depth of focus) is used, an area located on the focal plane can be inspected with very high resolution, but in an area deviating from the focal plane, an optical system having low resolution (ie, an optical system having a long depth of focus), there is a problem in that the level of inspection is lowered than when inspection is performed. More specifically, in the case of checking the state of the sample using an optical system having an optical axis in a direction perpendicular to the reference plane of the sample, the part out of the designed focal plane (ie, protruding or recessed from the reference plane of the sample) part) is defocused and looks hazy, so it becomes difficult to check the state of the part. Therefore, in the case of observing a part deviating from the focal plane, when observing using an optical system having a high resolution, compared to when observing using an optical system having a low resolution, there is a problem that the accuracy of inspection is lowered. there was.

Accordingly, there has been a demand for a sample inspection apparatus capable of observing a portion coincident with the focal plane to a portion partially deviating from the focal plane without distortion at high resolution.

The above-mentioned background art is possessed or acquired by the inventor in the process of derivation of the present invention, and cannot necessarily be said to be a known technology disclosed to the general public prior to the filing of the present invention.

An object of the embodiment is to provide a sample test apparatus and a sample test method capable of performing a more precise test, and to compensate for the difference in aspect ratio of the TDI Tilt vision.

According to an embodiment, in the sample inspection apparatus comprising a vision assembly relatively movable along a first straight line with respect to the sample, and obtaining an image of the sample by using a time delay integration method, the sample inspection apparatus comprising: The vision assembly may include: an optical system having an optical axis inclined at a first tilting angle with respect to a direction perpendicular to a reference plane of the sample on a first virtual surface including the first straight line; and a camera sensor disposed to be inclined at a second tilting angle with respect to a second virtual surface perpendicular to the optical axis.

According to an embodiment, a direction in which the optical system is tilted with respect to the reference plane of the sample and a direction in which the camera sensor is tilted with respect to the optical system may be opposite to each other.

According to an embodiment, the sizes of the first tilting angle and the second tilting angle may be the same.

According to an embodiment, the longitudinal magnification of the optical system may not be 1.

According to an embodiment, the optical system may cause an inverted image of the sample to be formed on the camera sensor.

According to an embodiment, at least one of the first tilt angle and the second tilt angle may be adjusted.

According to an embodiment, when any one of the first tilting angle and the second tilting angle is changed by the user, the other angle may be automatically changed in response to the amount of change of the one angle. there is.

According to an embodiment, the camera sensor may include a rotation axis relatively rotatable with respect to the optical system, and the rotation axis may be orthogonal to the optical axis.

According to an embodiment, the camera sensor may be disposed parallel to the reference plane of the sample.

According to an embodiment, the aspect ratio of the partial image with respect to the sample in an uncorrected state obtained by the camera sensor may be equal to 1:1.

According to an embodiment of the present disclosure, the sample testing apparatus may further include a controller for synthesizing the partial images using a time delay integration method, and the controller may synthesize the partial images without correcting an aspect ratio of the partial images.

According to one embodiment, in the sample inspection apparatus comprising a vision assembly relatively movable with respect to the sample, and for examining the sample by acquiring an image of the sample using a time delay integration method, the vision assembly comprises: a camera sensor spaced apart from the reference plane of the sample and disposed parallel to the reference plane of the sample; and an optical system positioned between the reference plane of the sample and the camera sensor and having an optical axis inclined with respect to a normal of the camera sensor.

According to the specimen inspection apparatus and specimen inspection method according to the embodiment, a more precise inspection may be performed by securing a sufficient depth of focus while having a high resolution, and acquiring an accurate image in which aspect ratio distortion is compensated.

According to the embodiment, by setting the tilting angle of each of the camera sensor and the optical system according to a predetermined relationship, by offsetting the change in the effective magnification and pixel width in the TDI scan direction of the image, it is better to correct the aspect ratio to 1:1. possible. What is characteristic is that, while correcting the aspect ratio to 1:1 in the above-mentioned offsetting process, the effect of expanding the depth of focus (DOF), which is the original purpose of the TDI tilt vision method, is achieved at the same time.

1 is a diagram illustrating a process of performing a sample test using a sample test apparatus according to an exemplary embodiment.
2 is a block diagram of a sample testing apparatus according to an exemplary embodiment.
3 is a diagram for explaining a process of acquiring an image using a time delay integration (TDI) method.
4 and 5 are diagrams conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is 0 degrees and the tilt angle tc of the camera sensor is 0 degrees. am.
6 is a diagram conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is greater than 0 degrees and the tilt angle tc of the camera sensor is 0 degrees.
7 is a diagram conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is 0 degrees and the tilt angle tc of the camera sensor is greater than 0 degrees. .
8 and 9 are diagrams for explaining that when the tilting angle tc of the camera sensor is greater than 0 degrees, the angle of the focal plane varies according to the size of the longitudinal magnification Ml of the optical system.
10 is a table comparing actual measurement results using the complex TDI tilt vision type sample inspection apparatus according to an embodiment and the actual measurement results using the TDI vision type sample inspection apparatus according to a comparative example.

This patent application claims priority on the basis of Patent Application No. 2020-0010160 filed on January 29, 2020, and the entire contents of the application are incorporated herein by reference.

Hereinafter, embodiments will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in the description of the embodiment, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment, the detailed description thereof will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the components from other components, and the essence, order, or order of the components are not limited by the terms. When it is described that a component is “connected”, “coupled” or “connected” to another component, the component may be directly connected or connected to the other component, but another component is between each component. It will be understood that may also be "connected", "coupled" or "connected".

Components included in one embodiment and components having a common function will be described using the same names in other embodiments. Unless otherwise stated, a description described in one embodiment may be applied to another embodiment, and a detailed description in the overlapping range will be omitted.

1 is a diagram illustrating a process of performing a sample test using a sample test apparatus according to an exemplary embodiment.

Referring to FIG. 1 , a sample testing apparatus 1 according to an exemplary embodiment may test a sample S by acquiring an image of the sample S using a time delay integration (TDI) method. can The time delay integration method (TDI) will be described later with reference to FIG. 3 . The specimen inspection device 1 may include a vision assembly 11 and a transport means 12 .

The vision assembly 11 is relatively movable along a first straight line L1 (a straight line parallel to the y-axis of FIG. 1 ) with respect to the sample S, and information about the surface of the sample S is collected during the movement process. It can be obtained by video. 1 illustrates a state in which the vision assembly 11 is relatively moved along a first straight line L1 with respect to the sample S as the transport means 12 transports the sample S. Alternatively, it can be understood by those skilled in the art that the transfer means 12 is not separately provided and the vision assembly 11 may move along the first straight line L1 while the sample S is fixed. There will be.

The vision assembly 11 may be disposed to be inclined with respect to the normal direction N of the reference plane of the sample S. 1 illustrates a state in which the vision assembly 11 is tilted by a first tilt angle tv with respect to the normal direction N of the reference plane of the sample S. Referring to FIG. Here, the reference plane of the sample S is a plane parallel to the sample support surface (eg, the upper surface of the transfer means 12 ) supporting the sample S, and is to be understood as a plane spaced apart by a preset height from the sample support surface. can For example, a surface spaced apart from the sample support surface by the expected thickness of the sample S may be set as the reference surface of the sample S. The vision assembly 11 may include a camera sensor 111 and an optical system 112 .

The optical system 112 may be positioned between the reference plane of the sample S and the camera sensor 111 and may have an optical axis OA inclined with respect to the normal direction N of the reference plane of the sample S. In other words, the optical system 112 first tilts with respect to the direction N perpendicular to the reference plane of the sample S on the first virtual plane (yz plane in FIG. 1 ) including the first straight line L1 . It may have an optical axis OA inclined at an angle tv.

In this way, by arranging the optical axis OA of the optical system 112 inclined with respect to the direction N perpendicular to the reference plane of the sample S, and inspecting it using a time delay integration (TDI) method, a non-flat defective area is formed. It is possible to prevent complete defocusing and to inspect the corresponding area over a certain level. Such a method may be referred to as a time-delay integral tilt vision (TDI Tilt vision) method. According to this method, it is possible to inspect both an area having an appropriate focal length and an area deviating from the focal length to a certain level or more. More specifically, in the region where the focal lengths exactly match, the resolution of the image obtained by this method is slightly lower than when photographing using an optical system having an optical axis in a direction perpendicular to the reference plane of the sample. However, in a region deviating from the focal length, the resolution of the image obtained by this method is significantly higher than when photographing using an optical system having an optical axis in a direction perpendicular to the reference plane of the sample. Therefore, using this method, when observing a generally flat sample, it is possible to observe a protruding portion and/or a depressed portion on the sample with a sufficiently high resolution. On the other hand, as the longitudinal (TDI direction of the optical system) spacing and the horizontal (LINE direction of the optical system) spacing of the sample are different from each other, there may be a difference in the aspect ratio. It causes a problem that reduces the accuracy of vision. However, according to an embodiment proposed in the present specification, such a problem can be reduced or eliminated.

The optical system 112 may be fixedly positioned in the case of the vision assembly 11 as shown in FIG. 1 . In this case, the optical system 112 may tilt together with the vision assembly 11 at the first tilt angle tv.

The camera sensor 111 is spaced apart from the reference plane of the sample S. The camera sensor 111 has a second tilting angle ( tc) and may be inclinedly disposed. The second tilting angle tc is an angle measured assuming that the case where the normal direction of the camera sensor 111 coincides with the optical axis OA of the optical system 112 is 0 degrees. In other words, the meaning that the second tilting angle tc is not 0 can be understood as meaning that the optical system 112 has the optical axis OA in a direction inclined with respect to the normal direction of the camera sensor 111 .

The camera sensor 111 may be rotatably installed in the case of the vision assembly 11 as shown in FIG. 1 . In other words, the camera sensor 111 may include a rotation shaft 1113 that is relatively rotatable with respect to the optical system 112 . For example, the rotation axis 1113 may be orthogonal to the optical axis OA. For example, the rotation shaft 1113 may rotatably connect the case of the vision assembly 11 and the camera sensor 111 to each other. According to such a structure, the camera sensor 111 may be tilted together with the vision assembly 11 at a first tilting angle tv, and based on the tilted state as described above, the camera sensor 111 may be tilted with respect to the vision assembly 11 . The second tilt angle tc may be further tilted. In other words, the camera sensor 111 may be tilted relative to the already tilted optical system 112 . Such a method will be defined as a "composite TDI tilt vision method".

For example, as shown in FIG. 1 , a direction in which the optical system 112 is tilted with respect to the reference plane of the sample S (a clockwise direction based on FIG. 1 ), and the camera sensor 111 is tilted with respect to the optical system 112 . The directions (counterclockwise direction based on FIG. 1 ) may be opposite to each other.

For example, the sizes of the first tilting angle tv and the second tilting angle tc may be the same.

For example, the first tilt angle tv and the second tilt angle tc may have absolute values based on the same coordinate system and may have different signs. For example, the camera sensor 111 may be disposed parallel to the reference plane of the sample S regardless of the first tilt angle tv of the optical system 112 .

The transport means 12 may relatively move the sample S with respect to the vision assembly 11 . For example, the transport means 12 may transport the sample S along the first straight line L1 while the vision assembly 11 is fixed at a specific point. In such a transfer process, sequentially acquired images may be collected to generate an image of the entire sample S. The conveying means 12, for example, may be a conveyor belt as shown in FIG. It should be noted that the type is not necessarily limited in this way.

2 is a block diagram of a sample testing apparatus according to an exemplary embodiment.

Referring to FIG. 2 , a sample inspection apparatus 1 according to an embodiment includes a vision assembly 11 , a transport means 12 , an input unit 13 , and a vision assembly 11 (or an optical system 112 ). A vision tilting driving unit 14 capable of tilting the , a camera tilting driving unit 15 capable of tilting the camera sensor 111, a display 16 for outputting an image of the sample S, and a memory capable of storing various information (17) and may include a control unit (18).

The input unit 13 may receive various types of information and/or commands from the user. For example, the user receives, through the input unit 13 , information about an angle tv at which the vision assembly 11 or the optical system 112 is tilted or an angle tc at which the camera sensor 111 is tilted. can The information may include, for example, a set depth of focus (DOF). This will be described later.

The controller 18 may store the image of the sample S acquired by the camera sensor 111 in the memory 17 . Here, it should be noted that the control unit 18 may be, for example, built into the vision assembly 11 or located outside the vision assembly 11 . For convenience of understanding, it is described that the control unit 18 is one, but those of ordinary skill in the art will find that the control unit 18 is composed of a plurality of processing elements, and the vision assembly 11 It will be understood that the inside and outside of the may be provided separately from each other, respectively. The controller 18 may generate an image of the entire sample S by synthesizing partial images of the sample S acquired at every moment by the camera sensor 111 using the time delay integration method (TDI). . According to an embodiment, the aspect ratio of the partial image with respect to the sample S in an uncorrected state obtained from the camera sensor 111 may be physically equal to 1:1. Accordingly, according to this embodiment, the controller 18 may generate an image having a high resolution while synthesizing the partial images without correcting the aspect ratio of the partial images in software. The controller 18 may output an image of all or at least a part of the sample S through the display 16 .

The control unit 18, for example, based on the information about the first tilting angle tv and/or the second tilting angle tc received from the input unit 13, the vision tilting driving unit 14 and/or The camera tilting driving unit 15 may be controlled. In other words, the controller 18 may adjust at least one of the first tilting angle tv and the second tilting angle tc. For example, when any one of the first tilting angle tv and the second tilting angle tc is changed by the user, the controller 18 determines that the other angle corresponds to the change amount of any one angle. The vision tilting driving unit 14 or the camera tilting driving unit 15 may be controlled to automatically change accordingly.

For example, when a set depth of focus is input through the input unit 13, the control unit 18 calculates the first tilting angle tv and the second tilting angle tc according to a relational expression to be described later, and calculates the calculated The vision tilting driver 14 and the camera sensor 111 may be tilted according to the first tilting angle tv and the second tilting angle tc. According to such a structure, it becomes possible to observe the sample S with the depth of focus desired by a user. Therefore, when the height of the protruding or recessed portion on the sample S is high, the sample S is observed using a long depth of focus, and when the height of the protruding or recessed portion is low, a short depth of focus is used. This makes it possible to observe the sample S.

Meanwhile, unlike described with reference to FIG. 2 , the first tilting angle tv of the optical system 112 and the second tilting angle tc of the camera sensor 111 may be provided in a fixed state. In this case, those skilled in the art will understand that the vision tilting driving unit 14 and the camera tilting driving unit 15 may be omitted.

3 is a diagram for explaining a process of acquiring an image using a time delay integration (TDI) method.

Referring to FIG. 3 , in the TDI method, the sample S may be photographed for each line by using the optical system 112 having a field of view (FOV) that is narrow in the width direction and wide in the width direction. 3 exemplarily illustrates a case of photographing by three lines.

As shown on the left, while the vision assembly 11 moves in one direction (the width direction), a plurality of partial images of the sample S may be acquired. For example, the vision assembly 11 may photograph the sample S while continuously moving at a constant speed in one direction. According to such a configuration, since it is possible to solve the vibration problem generated in the process of moving and stopping the vision assembly 11 , it is helpful to acquire a precise vision.

Meanwhile, as shown in FIG. 3 , the vision assembly 11 may acquire an image by photographing a plurality of lines instead of one line at a time, and overlapping and synthesizing overlapping lines from the obtained partial images. there is. More specifically, the adjacent partial images among the plurality of partial images include overlapping areas such as hatched areas, and the control unit 18 synthesizes the overlapped areas with each other, so as to You can create an entire image. According to the method of synthesizing overlapping regions as described above, since the exposure time for each individual line is increased by a multiple of the TDI resolution, sufficient exposure time is ensured to move the optical system at a high speed while moving the optical system at high speed. It becomes possible to obtain

On the other hand, when the vision assembly 11 is tilted to secure a sufficient depth of focus, an aspect ratio of an acquired image is changed.

It can be understood that the following FIGS. 4 to 9 are comparative examples for explaining the embodiment described in FIG. 1 .

4 and 5 are diagrams conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is 0 degrees and the tilt angle tc of the camera sensor is 0 degrees am.

4 and 5 , the camera sensor 111 may include an imaging area 1111 capable of receiving actual light and a frame 1112 supporting the imaging area 1111 . Even if the image of the sample S passes through the optical system 112 and is incident toward the camera sensor 111 , the image incident to the frame 1112 deviated from the imaging area 1111 may actually be acquired by the camera sensor 111 . does not exist. The solid line to which an arrow is added in FIG. 5 indicates a path of light passing through the optical system 112 , and indicates a boundary point of a region where an image can be acquired in the imaging region 1111 among regions on the sample S. Make it clear that it is for In other words, the solid line to which an arrow is added may be understood as a path of light flowing into the camera sensor 111 from a boundary point of an image obtainable area on the sample S.

5, the optical system 112 is arranged such that the optical axis of the optical system 112 is parallel to the normal direction of the reference plane R of the sample S (ie, tv = 0), and the camera sensor 111 When the camera sensor 111 is disposed such that the normal direction of is parallel to the optical axis of the optical system 112 (that is, tc = 0), the focal plane F of the vision assembly 11 is It may be arranged to coincide with the reference plane R of the desired sample S. In this case, as the depth of focus is short, a blurred image is inevitably generated for the protruding/recessed portion that deviates from the reference plane R of the sample S.

Hereinafter, each term will be defined as follows with reference to FIGS. 4 and 5 . Unless there is an opposite expression, the definition of each term may be commonly applied to other drawings.

- Camera pixel size (Pc): the length of one side of each pixel of the camera sensor 111

- TDI resolution (stg): the number of camera pixels arranged along the TDI scan direction (ie, y-axis direction) in the camera sensor 111

- Camera width (Sizey): The length in the TDI scan direction of the image pickup area 1111 of the camera sensor 111, which can be expressed by the following equation

- Actual size of the image pixel (P): the length measured along the TDI scan direction, the actual width of the area on the sample S corresponding to the image pixel obtained from the individual pixel of the camera sensor 111 . P is a length measured in a state in which both the optical system 112 and the camera 111 are not tilted (ie, tv = 0, tc = 0), and can be expressed by the following equation

Here, the lateral magnification Mt is a design specification of the optical system 112 and means a magnification in the TDI scan direction (ie, the y-axis direction). Typically, in the optical system 112 , the lateral magnification Mt has the same value in both the TDI scan direction (width direction, ie, y-axis direction) and line direction (width direction, ie, x-axis direction), and theoretically The relationship between the longitudinal magnification Ml and the lateral magnification Mt of the optical system 112 is optically known as the following equation.

On the other hand, it should be noted that the actual values of the vertical magnification Ml and the horizontal magnification Mt are much larger than 1 due to the characteristics of the sample inspection apparatus 1 . In the case of the verification result to be described later, it is revealed that the result is the result of using the optical system 112 having a horizontal magnification Mt and a vertical magnification Ml of 7 and 49, respectively. However, in order to make it easier to understand the relationship according to the complex geometric orthogonal projection, FIGS. 5 to 7 are illustrated based on the case where the vertical magnification (Ml) and the horizontal magnification (Mt) are 1, and the actual vertical magnification (Ml) ) and the difference that may occur as the lateral magnification (Mt) is not 1 reveals that it has been described with reference to FIGS. 8 and 9 .

- Actual width of the acquired image (FOVy): The length measured along the TDI scan direction, and the actual width of the area on the sample S corresponding to the partial image acquired through the camera sensor 111 . FOVy is a length measured in a state in which both the optical system 112 and the camera 111 are not tilted (ie, tv = 0, tc = 0), and can be expressed by the following equation

On the other hand, as shown in FIG. 6 , only the optical system 112 is tilted, and based on a state in which the camera sensor 111 is not tilted with respect to the optical system 112 (ie, tv > 0, tc = 0), the camera sensor 111 ), in the area on the sample S corresponding to the partial image obtained through ), the length measured along the actual scan direction will be defined as "FOVyv".

On the other hand, as shown in FIG. 7 , the optical system 112 is not tilted, and only the camera sensor 111 is tilted with respect to the optical system 112 based on the tilted state (ie, tv = 0, tc > 0), the camera sensor 111 ), in the area on the sample S corresponding to the partial image obtained through ), the length measured along the actual scan direction will be defined as "FOVyc".

The actual length in the x-axis direction of the sample S photographed in the image in a state in which the optical system 112 and/or the camera sensor 111 is tilted is constantly fixed by the transverse magnification Mt of the optical system 112, However, the actual length of the sample S in the y-axis direction is not only the horizontal magnification Mt of the optical system 112, but also the vertical magnification Ml, which is the square of the lateral magnification Mt, and the tilted angle tc and/or tv ) according to the complex geometric orthographic relationship.

As a result, the effective magnification in the y-axis direction varies depending on which of the optical system 112 and the camera sensor 111 is tilted, usually by a cosine or inverse multiple of the tilted angle (tc and/or tv). It decreases or increases, and the pixel width in the y-axis direction of the image increases or decreases by the inverse multiple of the changed effective magnification, so that the aspect ratio of the image is not 1:1.

If the error of the aspect ratio is ignored and the TDI scan is performed according to the aspect ratio of 1:1, an error as much as a cosine or inverse multiple per pixel occurs, and the TDI resolution (stg) of the error occurs due to the characteristics of the TDI operation. amplified by multiples. Therefore, in the process of synthesizing the partial images as much as the final amplified value, a clear image cannot be generated, and a blurred image is generated. Considering that the commonly used TDI resolution (stg) is a very large value of about 256, a generally unacceptable level of blurred image is generated, so a process of compensating for the above error according to the aspect ratio is required.

When this is compensated by software, not only time and effort for compensation are required, but also the resolution of the final image is lost due to the increased/decreased magnification and pixel width, and as a result, the accuracy of inspection is deteriorated.

However, according to the embodiment shown in FIG. 1 , by setting the tilt angle of each of the camera sensor 111 and the optical system 112 according to a predetermined relationship, the effective magnification and pixel in the y-axis direction (TDI scan direction) of the image By offsetting the changes in width, it is possible to correct the aspect ratio to 1:1. What is characteristic is that, while correcting the aspect ratio to 1:1 in the above-described offsetting process, the effect of expanding the depth of focus (DOF), which is the original purpose of the TDI tilt method, is achieved at the same time. Hereinafter, it will be described in detail with reference to FIGS. 6 to 9 .

6 is a diagram conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is greater than 0 degrees and the tilt angle tc of the camera sensor is 0 degrees.

6, the optical system 112 is disposed so that the optical axis of the optical system 112 is inclined at a first tilting angle tv with respect to the normal direction of the reference plane R of the sample S (that is, tv>0) , when the camera sensor 111 is disposed such that the normal direction of the camera sensor 111 is parallel to the optical axis of the optical system 112 (ie, tc = 0), the focal plane F of the vision assembly 11 is inspected With respect to the reference plane R of the target sample S, it has an inclined relationship at the first tilting angle tv. On the other hand, such a relationship is independent of the longitudinal magnification (Ml).

Meanwhile, since the camera sensor 111 is not tilted with respect to the optical system 112 , the width and length of the image acquisition area on the focal plane F of the vision assembly 11 becomes FOVy as in FIG. 5 . However, as much as the focal plane F is inclined at the first tilting angle tv with respect to the reference plane R, the width and length FOVyv of the actual area on the sample S corresponding to the image acquired by the camera sensor 111 ) becomes 1/cos(tv) times longer than FOVy, and this is expressed as the following equation.

On the other hand, among the regions indicated by FOVy on the focal plane F inclined with respect to the reference plane R, the lowest position is called the "minimum position of the depth of focus (DOF_min)", and the highest position is the "maximum position of the depth of focus ( DOF_max)". A distance between DOF_min and DOF_max may be referred to as a “depth of focus (DOFv) extended according to tilting of the optical system”, which may be expressed by the following equation.

When the TDI method is performed in such a structure, portions of the sample S passing through the inclined focal plane F are accurately focused in the image. In other words, even if there is a portion of the sample S that protrudes or is recessed from the reference plane R, all portions located between the minimum value of the depth of focus (DOF_min) and the maximum value of the depth of focus (DOF_max) are included in the vision assembly 11 In the process of moving in the scan direction, it must pass through the moving focal plane F. In other words, even if there is a protruding or recessed portion of the sample S, an image having an exact focus is necessarily present among a plurality of partial images obtained in the process of performing the TDI method. As such, it is known that, in the process of performing the TDI method, if an image having an exact focus is included, the resolution is remarkably increased due to the characteristics of the TDI method.

In this way, by arranging the optical axis of the optical system 112 inclined with respect to the normal direction of the reference plane R of the sample S, and inspecting using the TDI method, the non-flat defective area on the sample S is completely defocused. It is possible to prevent this from happening, and to inspect the area above a certain level. Such a method can be called a time-delay integral tilt vision (TDI Tilt vision) method. According to this method, it is possible to inspect both an area with an appropriate focal length and an area outside the focal length to a certain level or higher. It was theoretically confirmed that the inspection level in this case was significantly higher than in the case of inspection using an optical system having an optical axis perpendicular to the plane of the sample and having a low resolution.

7 is a diagram conceptually illustrating the relationship between the imaging area of the camera sensor and the image acquisition area on the sample when the tilt angle tv of the vision assembly is 0 degrees and the tilt angle tc of the camera sensor is greater than 0 degrees. , 8 and 9 are diagrams for explaining that when the tilting angle tc of the camera sensor is greater than 0 degrees, the angle of the focal plane varies according to the size of the longitudinal magnification Ml of the optical system.

First, as shown in FIG. 7 , the optical system 112 is arranged such that the optical axis of the optical system 112 is parallel to the normal direction of the reference plane R of the sample S (ie, tv = 0), and the normal of the camera sensor 111 is When the camera sensor 111 is disposed such that the direction is inclined at a second tilting angle tc with respect to the optical axis of the optical system 112 (that is, tc > 0), the camera sensor 111 in the optical axis direction of the optical system 112 The area in which the imaging area 1111 of the optics 112 is orthogonally projected to the optical system 112 is reduced by a factor of cos(tc). Such an effect also affects the width and length FOVyc of the actual area on the sample S corresponding to the image obtained by the camera sensor 111, and is expressed by the following equation.

On the other hand, as shown in the optical system 112 , if an inverted image of the sample S is formed on the camera sensor 111 , the focal plane F of the vision assembly 11 is of the sample S to be inspected. With respect to the reference plane R, the second tilting angle tc has an inclined relationship in the opposite direction.

Meanwhile, unlike the case where only the optical system 112 is tilted, when only the camera sensor 111 is tilted, the longitudinal magnification Ml is involved. 7 exemplarily illustrates a case where the longitudinal magnification Ml is 1 for convenience of understanding, and the focal plane F is shown to be inclined by a second tilting angle tc with respect to the reference plane R, but , actually, when the longitudinal magnification Ml is not 1, the angle of the focal plane F with respect to the reference plane R varies depending on the longitudinal magnification M1.

First, as shown in FIG. 8 , when the longitudinal magnification Ml exceeds 1, the size of the angle θ1 at which the focal plane F is inclined with respect to the reference plane R is smaller than the size of the second tilting angle tc. do. Next, as shown in FIG. 9 , when the longitudinal magnification Ml is less than 1, the size of the angle θ2 at which the focal plane F is inclined with respect to the reference plane R is greater than the size of the second tilting angle tc. . In other words, the angle of the focal plane F with respect to the reference plane R decreases as the vertical magnification M1 increases, and increases as the vertical magnification M1 decreases.

Therefore, unlike FIG. 6, the "depth of focus (DOFc) extended according to the tilting of the camera sensor" includes the longitudinal magnification Ml as a factor as shown in the following equation (DOF_max and DOF_min shown in FIG. 7 are of understanding For convenience, it should be noted that the longitudinal magnification (Ml) is assumed to be 1).

Composite TDI Tilt Vision Method

As described above, in the TDI tilt vision method, (i) as in FIG. 6, only the optical system 112 is tilted (tv > 0), and the camera sensor 111 is not tilted with respect to the optical system 112 (tc = 0) , (ii) as shown in FIG. 7, when only the camera sensor 111 is tilted with respect to the optical system 112 without tilting the optical system 112 (tv = 0) (tc > 0), an aspect ratio of 1:1 is obtained can't

However, as in the embodiment described in FIG. 1, by tilting the camera sensor 111 according to a predetermined relationship with respect to the optical system 112 in a state in which the optical system 112 is tilted (tv > 0) (tc > 0), You can get an aspect ratio of 1:1.

For the convenience of geometrical calculation, first, the relationship in the case of tilting only the camera sensor 111 is calculated as follows (refer to Equations 7 and 8).

FOVyc = FOVy Х cos(tc) (Equation 7)

DOFc = FOVy Х sin(tc) ÷ Mt (Equation 8)

Next, the degree of change by rotation of the entire vision assembly 11 is calculated. First, when the vision assembly 11 is tilted without tilting the camera sensor 111 relative to the optical system 112 , it is as follows (refer to Equations 5 and 6).

FOVyv = FOVy ÷ cos(tv) (Equation 5)

DOFv = FOVy Х sin(tv) (Equation 6)

On the other hand, when only the camera sensor 111 is tilted primarily and the vision assembly 11 is tilted secondarily, the area on the sample S corresponding to the partial image obtained through the camera sensor 111 In , the length measured along the actual scan direction is defined as "FOVycv". It is calculated as the following equation.

Meanwhile, the finally extended depth of focus is defined as "DOFcv", which is calculated as shown in the following equation.

If tc and tv are set to the same value, FOVycv obtained in Equation 9 becomes the same as FOVy, so that the final aspect ratio can be made 1:1. Meanwhile, even when tc and tv are set to the same value, DOFcv obtained in Equation (10) may be a non-zero value. In other words, it is possible to extend the depth of focus while making the final aspect ratio 1:1.

This is because the aspect ratio difference in each of FIGS. 6 and 7 is equal to each other to cancel the difference in the aspect ratio, and the difference in DOF is different by the aspect ratio and the direction is also different, so even if it is mutually reinforced or canceled, 0 is As a result, the aspect ratio is 1:1 and the depth of focus is expanded.

Verification Results for Examples

10 is a table comparing actual measurement results using the complex TDI tilt vision type sample inspection apparatus according to an embodiment and the actual measurement results using the TDI vision type sample inspection apparatus according to a comparative example.

Referring to FIG. 10 , it can be seen that according to the embodiment, unlike Comparative Examples 2 and 3, it has an aspect ratio of 1:1, and has a sufficiently expanded depth of focus, unlike Comparative Example 1.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiment, or may be known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic such as floppy disks. - includes magneto-optical media, and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with reference to the limited drawings, various modifications and variations are possible from the above description by those of ordinary skill in the art. For example, the described techniques are performed in an order different from the described method, and/or the described components of structures, devices, etc. are combined or combined in a different form than the described method, or other components or equivalents are used. Appropriate results can be achieved even if substituted or substituted by

Claims (12)

A sample inspection apparatus comprising: a vision assembly relatively movable along a first straight line with respect to the sample;
The vision assembly,
an optical system having an optical axis inclined at a first tilting angle with respect to a direction perpendicular to a reference plane of the sample on a first virtual surface including the first straight line; and
and a camera sensor disposed to be inclined at a second tilting angle with respect to a second virtual surface perpendicular to the optical axis.
The method of claim 1,
A direction in which the optical system is tilted with respect to the reference plane of the sample and a direction in which the camera sensor is tilted with respect to the optical system are opposite to each other.
The method of claim 1,
The sample testing apparatus, characterized in that the size of the first tilting angle and the second tilting angle are the same.
The method of claim 1,
The sample inspection device, characterized in that the longitudinal magnification of the optical system is not 1.
The method of claim 1,
The optical system is a sample inspection device, characterized in that the inverted image of the sample is formed on the camera sensor.
The method of claim 1,
At least one of the first tilting angle and the second tilting angle is adjustable.
7. The method of claim 6,
When any one of the first tilting angle and the second tilting angle is changed by the user, the other angle is automatically changed in response to the change amount of the one of the angles. .
The method of claim 1,
The camera sensor includes a rotation axis relatively rotatable with respect to the optical system,
The rotation axis is a sample inspection device, characterized in that orthogonal to the optical axis.
The method of claim 1,
The camera sensor is a sample inspection device, characterized in that disposed parallel to the reference plane of the sample.
The method of claim 1,
Sample inspection apparatus, characterized in that the aspect ratio of the partial image with respect to the sample in an uncorrected state obtained by the camera sensor is equal to 1:1.
11. The method of claim 10,
The sample test device,
Further comprising a control unit for synthesizing the partial image using a time delay integration method,
wherein the control unit synthesizes the partial image without correcting the aspect ratio.
A sample inspection apparatus comprising a vision assembly relatively movable with respect to the sample, and for examining the sample by acquiring an image of the sample using a time delay integration method, the sample inspection apparatus comprising:
The vision assembly,
a camera sensor spaced apart from the reference plane of the sample and disposed parallel to the reference plane of the sample; and
and an optical system positioned between the reference plane of the sample and the camera sensor and having an optical axis inclined with respect to a normal of the camera sensor.

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