KR20100088957A - An apparatus for detecting surface defects - Google Patents

Abstract

PURPOSE: An apparatus for inspecting surface defects is provided to reduce an inspection time using an enlarged optical image in order to inspect the surface of a target. CONSTITUTION: Light source(10) radiates light for transferring information related to an image which is formed on a substrate(31). A target is loaded on a stage(30). An illuminating optical system(20) condenses light from the light source and radiates the light toward the target. An imaging optical system(100) takes an optical phase from the reflected light from the substrate and obtains an image.

Description

Surface defect inspection device {AN APPARATUS FOR DETECTING SURFACE DEFECTS}

The present invention relates to a surface defect inspection apparatus, and more particularly, to a surface defect inspection apparatus for inspecting the presence or absence of defects on the surface of the semiconductor substrate or mask used in the manufacture of semiconductors.

In general, lithographic processes are widely used to form circuit patterns of semiconductor devices. In such a lithography process, the pattern of the mask is transferred onto a substrate through an exposure and etching process using a mask having a pattern formed to correspond to a circuit pattern to form a pattern.

In recent years, as the degree of integration of semiconductor devices increases, the size of patterns required for semiconductor devices has gradually decreased. As such, as the size of the pattern is reduced, surface defects such as pattern bridges and pinch defects may occur on the actual substrate due to limitations in the semiconductor device manufacturing process.

However, in the case of the conventional inspection apparatus, as the surface shape of the inspected object is gradually miniaturized, it is not easy to find a defect and a problem arises in that a considerable time is required to find it.

The present invention is to provide a surface defect inspection apparatus that can enlarge and inspect the shape information from the target pattern to solve the above problems.

In order to achieve the above object, the present invention provides a light source, a stage on which an inspected object is fixed and seated, an illumination optical system that collects incident light incident from the light source, and illuminates the surface of the inspected object, and reflects from the surface of the inspected object. Provided is a surface defect inspection apparatus having a plurality of paths through which the reflected light passes, and including an imaging optical system for expanding and imaging the reflected light traveling in each path.

Here, the imaging optical system further includes a plurality of image detectors capable of detecting an image of the reflected light, and the reflected light is preferably imaged in each of the image detectors corresponding to the traveling path. In this case, the image detector may be made of a CCD sensor.

The imaging optical system may include a plurality of zone plates each configured to enlarge and image the reflected light traveling along the plurality of paths.

In this case, the plurality of zone plates may be disposed in parallel to correspond to respective paths through which the reflected light travels, and may image reflected light traveling along the corresponding paths with the corresponding image detector.

Here, the imaging optical system includes a plurality of fine mirrors, and the reflected light reflected from the surface of the inspected object is incident on each of the fine mirrors and divided into the plurality of paths by the position and inclination of the fine mirrors. Can be configured to

In this case, the imaging optical system may further include a plurality of fine mirrors branching the path of the reflected light, and the reflected light reflected from the surface of the inspected object may be formed in a plurality of paths while being reflected in each micromirror. Do.

Alternatively, the capillary may include a multi capillary tube branching the path of the reflected light, and the reflected light reflected from the surface of the test object may be incident into the multi capillary tube and divided along the path formed by each capillary tube. .

In this case, the reflected light traveling along each path is preferably irradiated in the vertical direction to the corresponding zone plate.

Meanwhile, the zone plate may form a plurality of two-dimensional images having different focal points in the image detector, and the image detector may be configured to acquire a three-dimensional shape using the plurality of two-dimensional images.

In this case, the zone plate may be configured as a zone plate doublet including diffraction gratings having different focal lengths.

Alternatively, the zone plate may be configured as a Zernike zone plate which generates a phase difference of 0.5π with respect to the light transmitted while being diffracted without being diffracted.

Alternatively, a phase plate may be provided in front of the zone plate to induce a phase difference of reflected light passing through the zone plate.

Further, the zone plate may be configured as a volume zone plate having a diffraction grating formed to be inclined with the direction in which the reflected light is irradiated.

On the other hand, the light source used in the present invention is preferably irradiated with electromagnetic waves in the range of 10 to 15nm.

According to the present invention, it is possible to inspect the defect on the surface of the inspected object through the enlarged image, thereby reducing the time required for inspecting the defect. In addition, since the image is divided and divided into zones to enlarge the image, the image distortion is significantly reduced, so that the inspection can be easily performed.

Hereinafter, a surface defect inspection apparatus according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the present exemplary embodiment, a pattern defect inspection apparatus for inspecting a pattern formed on a semiconductor substrate will be described as an example. However, the present invention is not limited to the pattern defect inspection apparatus of the substrate, and may be widely used for inspecting other defects formed on the surface of the substrate, inspecting the pattern of the mask for risk repetition, and inspecting the pattern during liquid crystal display such as LCD. have. In addition to the above, it will be apparent that the light beam can be applied to various inspection apparatuses for identifying shape images by reflecting light waves.

1 is a schematic diagram showing an internal configuration of a pattern defect inspection apparatus according to a first preferred embodiment of the present invention. The pattern defect inspection apparatus according to the present embodiment will be described in more detail with reference to FIG. 1.

The pattern defect inspection apparatus of the present embodiment includes a light source 10, an illumination optical system 20 that forms a path through which light emitted from the light source 10 travels to the stage 30, and a substrate on which a pattern (not shown) is formed. 31) and an imaging optical system 100 for acquiring an image of a pattern by imaging the stage 30 on which the back is seated and the light reflected from the substrate 31.

The light source 10 irradiates light for transmitting image information of a pattern formed on the substrate 31. At this time, the light source 10 may be configured to irradiate extreme ultraviolet (EUV), so that even patterns consisting of nodes of several nanometers can be inspected. It is possible to generate light using a laser produced plasma or a discharge produced plasma. As the target substance, Sn, Xe, or the like can be used.

For this reason, the light waves generated by the light source 10 may have a wavelength in the range of 10 to 15 nm, and may be extreme ultraviolet rays having a wavelength of 13.5 nm. And, the average laser pulse energy is 0.1~1 mJ, a repetition rate is 1~10Hz, the resolution of the spectrum band is 1 × 10 ^- can have a range of ⁴ or less.

The light irradiated from the light source 10 travels in the direction of the stage 30 through the illumination optical system 20. It is preferable that the illumination optical system 20 collects the light irradiated from the light source 10 and enters the pattern of the substrate 31. This is because the higher the degree to which incident light incident on the substrate 31 is focused, the pattern image information with clear resolution can be obtained. In this embodiment, as an example of the condensing optical system, a Schwarzchild optical system is included. Therefore, incident light irradiated from the light source 10 may be irradiated onto the substrate 31 in a state where light is collected while passing through the illumination optical system 20.

The stage 30 is a structure which mounts the board | substrate 31 which is the to-be-tested object of this embodiment, and the board | substrate 31 is fixed in the state mounted on the said stage 30. Therefore, the incident light irradiated from the light source 10 is incident toward the substrate 31 and reflected by the substrate 31 on which the pattern is formed, and proceeds in the opposite direction.

In this case, the stage 30 may include a separate driver (not shown) to finely adjust the position of the seated substrate 31. In addition, the stage 30 may be configured to move in the horizontal or vertical direction or to adjust the inclination by the driving unit. In this case, when the pattern inspection of the corresponding region is completed, the pattern inspection of the next inspection region of the substrate 31 may be performed by adjusting the position of the stage 30 without adjusting the positions of the light source 10 and other optical systems.

The reflected light reflected from the substrate 31 is reflected in a state including image information on the pattern of the substrate 31, and then is imaged while passing through the imaging optical system 100. Specifically, when the light irradiated from the light source 10 is reflected from the substrate 31, the reflected light is divided into a plurality of paths while passing through the imaging optical system 100, and the reflected light traveling through each path is enlarged and imaged. The image detector 130 forms an image while passing through the optical device. Hereinafter, the imaging optical system 100 according to the present invention will be described in more detail with reference to FIGS. 2 to 6.

2 is an enlarged view illustrating an enlarged portion A of FIG. 1. As shown in FIG. 2, the imaging optical system 100 according to the present exemplary embodiment includes a multi-capillary tube 110 forming a plurality of paths and a zone plate 121 to enlarge and image the reflected light traveling through each path. Can be configured.

That is, in the present invention, expanding and magnifying the light means not only naturally expanding the focused light while passing the focal length, but also including an additional optical device for expanding the imaging. Therefore, in the present embodiment, the zone plate 121 can be used as an optical device for enlarged imaging. In this case, it is possible to form an enlarged image as desired even with a short optical system length, and it is possible to construct a small-scale inspection apparatus.

As shown in FIG. 2, in the present embodiment, a zone plate array 120 in which a plurality of zone plates 121 is formed may be included. Each zone plate 121 may be located in parallel to correspond to a plurality of paths through which the reflected light travels. Therefore, the reflected light divided into a plurality of paths may pass through the zone plate 121 corresponding to the path and may have an enlarged image. In this case, the distortion of the image due to the enlarged image can be reduced as compared with the case of integrally magnifying the one reflected light.

The reflected light traveling along each path passes through each zone plate 121 and forms an image on the image detector 130. In the present exemplary embodiment, a CCD sensor may be used as the image detector 130.

As shown in FIG. 1, a plurality of image detectors 130 including a CCD sensor according to the present embodiment are provided, and each image detector 130 may be installed to correspond to each path through which reflected light travels. have. Therefore, the reflected light traveling along the corresponding path may pass through the corresponding zone plate 121 and may be imaged on the corresponding image detector 130.

If the image detector in which an image is imaged is composed of a single CCD sensor, there is a limit in enlarging the size of the CCD sensor. Therefore, it may be difficult to obtain a sufficiently enlarged image. In addition, even if the CCD sensor can be configured with a sufficient size, there is a concern that the cost will increase significantly. Therefore, it is preferable to configure the plurality of image detectors 130 by using the plurality of CCD sensors as in the present embodiment, to divide the reflected light into zones, and to magnify them independently to form images on the image detectors 130.

As such, according to the present invention, the size of the image to be enlarged and imaged may not be limited, and the cost may be reduced. In addition, as compared to processing image information using a large-area CCD sensor, the processing speed of the image can be improved in parallel in each CCD sensor.

Hereinafter, the components constituting the imaging optical system of the present embodiment will be briefly described.

FIG. 3 shows the shape of a general zone plate, and FIG. 4 is a schematic diagram showing the principle of enlarged image formation by the zone plate.

As described above, in the present invention, another optical device for expanding and forming the reflected light is provided. In this embodiment, the zone plate is used as an example.

A general principle of the zone plate 121 is a configuration in which a plurality of diffraction gratings form concentric circles (see FIG. 3B). Between each diffraction grating 121a, an open window 121b having a concentric shape is repeatedly formed. Diffraction occurs while light passes through the opened window 121b. At this time, it is preferable to design the interval and thickness of each diffraction grating 121a so that the light passing through the adjacent window 121b can cause constructive interference with each other. (See Figure 3A)

Here, the light passing through the zone plate 121 may travel not only in the optical axis direction but also in the direction inclined with the optical axis. Accordingly, the zone plate 121 may focus or enlarge the beam while simultaneously serving as a convex lens and a concave lens.

In this case, each of the diffraction gratings 121a of the zone plate 121 may block incident light or induce phase inversion. In general, the phase zone plate has a higher condensing efficiency than the amplitude zone plate, and is utilized. The radius of each diffraction grating is a concentric structure having alternating phase inversion of π and 0 ㅀ. It can be determined to cause constructive interference at.

가 되고, 이미지 확대 비율

가 될 수 있는 것이다. 통상적인 존 플레이트는 지름이 약 0.5mm, 최외곽의 폭은 약 10∼100nm이며, 초점거리는 2mm 내외로서 통상적으로 480배 이상으로 확대 결상하는 것이 가능하다. As shown in FIG. 4, the zone plate 121 may enlarge and image the light passing therethrough using the above-described properties. If the distance between the sample and the zone plate is a, the distance between the zone plate and the imaging plane is b, and the focal length is f.

Image magnification

Can be. A typical zone plate has a diameter of about 0.5 mm, an outermost width of about 10 to 100 nm, and a focal length of about 2 mm, and can be enlarged and formed to an image of 480 times or more.

Therefore, the zone plate 121 can be provided in the path through which the reflected light reflected from the substrate 31 proceeds, and the reflected light can be enlarged and formed. In this case, the reflected light divided into a plurality of paths are preferably incident to each other so as to pass through the corresponding zone plate 121 in the vertical direction. Accordingly, the imaging optical system 100 of the present embodiment uses the multiple capillary tubes 110 to form the plurality of paths through which the reflected light travels, and to allow the reflected light passing through the respective paths to enter the zone plate 121 in the vertical direction. Can be configured.

5 is a cross-sectional view showing a cross section of a general multiple capillary tube, and FIG. 6 is a schematic diagram illustrating a principle of light traveling along each path of the multiple capillary tube.

As shown in FIG. 5, the general multiple capillary tube 110 is composed of a plurality of capillary tubes 111 through which light can pass. Then, when light is introduced into one end (110a) in which the multi-capillary tube (110) is densely formed, it can be separated and proceed along the path formed by each capillary tube. Therefore, the light traveling in one direction flows along different paths along the path formed by each capillary tube 111 while flowing into the multiple capillary tube 110.

As shown in FIG. 6, each capillary tube 111 may be formed of a glass tube having a hollow path formed therein. Therefore, when the reflected light is incident at an angle equal to or less than the critical angle, the reflected light proceeds while causing total reflection inside the capillary tube 111.

The multi-capillary tube 110 of the present embodiment may be installed to be adjacent to the position where the reflected light is reflected from the substrate 31. (See FIG. 2) In this case, at the position adjacent to the substrate 31, each end of the capillary tube 111 Are dense and formed, the reflected light may be incident to each of the capillaries 111 separately. Each capillary tube 111 forms a plurality of paths through which the reflected light travels to the position where the zone plate array 120 is installed. At this time, each end of the capillary tube 111 adjacent to the zone plate array 120 is preferably installed to face the vertical direction with the respective zone plate 121. Therefore, the reflected light which is totally reflected inside each capillary tube 111 may be incident perpendicularly to the corresponding zone plate 121 after passing through the capillary tube.

As described above, in the present embodiment, the multi-capillary tube 110 is configured to separate the reflected light into sections. However, the present invention is not limited thereto, and it is also possible to configure a plurality of optical paths using other components.

As another example, the path of the reflected light may be divided using the micro mirror array 210 having the plurality of micro mirrors 211. As shown in FIG. 7, the micromirror array 210 is disposed on a path through which the reflected light is reflected from the substrate 31 and travels. The reflected light may be irradiated onto the micro mirror array 210 to reflect the light by the plurality of micro mirrors 211.

At this time, each micro mirror array 210 reflects the reflected light at different positions. Further, each micro mirror 211 is preferably configured to be able to adjust the inclination individually. Therefore, the reflected light incident from the substrate 31 is irradiated into the plurality of micromirrors 211, respectively, and reflected in different directions by the positions and the inclination angles of the micromirrors 211. In addition, the reflected light divided into a plurality of paths may be incident on the corresponding zone plate 121 to enlarge an image.

Although not specifically illustrated in FIG. 7, an additional optical device may be additionally disposed on the path where the reflected light is reflected by the micromirror 211 and may adjust a traveling direction of the reflected light. Accordingly, the path may be controlled to be incident on the corresponding zone plate 121 in the vertical direction.

As described above, the present invention may divide the paths of the reflected light reflected from the substrate 31 into a plurality of methods using various methods, and enlarge and image each of the paths of the reflected light to obtain an image from the corresponding image detector 130. In this case, the processing speed is improved by providing the plurality of image detectors 130, and the enlarged image is formed by dividing the reflected light so that inspection can be easily performed.

Hereinafter, a second preferred embodiment according to the present invention will be described with reference to FIG. 8. However, the same name and the same reference numerals are used for similar configurations to the above-described embodiment, and descriptions of common contents will be omitted in order to avoid duplicate descriptions.

In the present exemplary embodiment, when the light emitted from the light source 10 is reflected on the substrate 31 as in the above-described embodiment, the defect of the pattern may be inspected in such a manner that the reflected light is divided and magnified and imaged on the plurality of image detectors 130. Can be. However, in the above-described embodiment, the image detector 130 may acquire only one image, but in the present embodiment, it is possible to configure each image detector 130 to acquire two or more images. To this end, in the above-described embodiment, a special zone plate may be used in the present embodiment, as compared with a general zone plate.

FIG. 8 is a view showing a zone plate doublet and a video image according to a second preferred embodiment of the present invention. As shown in a of FIG. 8, in the present embodiment, a zone plate doublet 320 may be used to enlarge and reflect the reflected light. Here, the zone plate doublet has a configuration in which two zone plates ZP1 and ZP2 having different center points are combined.

The reflected light passing through the zone plate doublet 320 has different focal positions O1 and O2 depending on the position where diffraction occurs. Therefore, as shown in FIG. 8, two different images may be formed in the image detector.

As described above, one reflected light accompanying the pattern image information of the predetermined area may be formed into a plurality of different images. In this case, the image detector may process the plurality of images to form a three-dimensional image of the pattern. Therefore, the defect of the pattern can be easily inspected using the three-dimensional image. (See b of FIG. 8)

In the present exemplary embodiment, the zone plate doublet 320 is used to acquire a plurality of different images by using one reflected light. However, the zone plate doublet 320 may be configured using another zone plate.

As another example, as shown in FIG. 9, the imaging optical system may include a separate phase plate 422. As shown in FIG. 9A, a phase plate 422 may be installed on a back focal plane of the zone plate 421. In this case, only the deflected beam is focused, and the reflected light passing through the phase plate 422 generates a phase difference of 1/4 wavelength compared to the reference light by the phase plate, thereby increasing image contrast. (See b of Figure 9)

As another example, as illustrated in FIG. 10, a Zernike zone plate may be used. Here, the Zenique zone plate may generate a phase difference of 0.5π with respect to the light passing through the zone plate and diffracted with the light passing through the zone plate. Thus, this can be used to improve image contrast.

In addition to this, other types of zone plates may be used to increase the resolution of the image. As an example, FIG. 11 illustrates various examples of volume zone plates. Here, the volume zone plate has a configuration in which the direction in which the diffraction grating is formed is inclined at a predetermined angle with the optical axis.

In the case of using the existing zone plate, in order to improve the resolution, since the outermost width should be reduced to 20 nm or less, it was easy to manufacture. However, by using the above-described volume zone plate, the aspect ratio can be increased to 20: 1 to increase the order of diffraction, and the resolution can be increased by increasing the order of diffraction. As described above, the volume zone plate inclined by the diffraction grating with respect to the optical axis has a 50% or more increase in diffraction efficiency compared to a general zone plate, thereby obtaining a pattern image having improved resolution.

As described above, according to the present invention, it is possible to inspect the state of the surface and the presence or absence of defects by dividing the reflected light with the image information of the surface while reflecting it from the surface of the inspected object. Further, by using various types of zone plates, it is possible to inspect surface defects by obtaining a three-dimensional image for easy identification.

1 is a schematic diagram showing the internal configuration of a surface defect inspection apparatus according to a first embodiment of the present invention,

2 is an enlarged view illustrating an enlarged portion A of FIG. 1;

3 is a view showing a cross section and a shape of a general zone plate,

4 is a schematic diagram showing the principle of enlarged image formation by the zone plate,

5 is a cross-sectional view showing a cross section of a general multiple capillary tube,

6 is a schematic diagram showing the principle of light traveling along each path of multiple capillaries;

7 is a schematic diagram showing an imaging optical system according to another embodiment;

8 is a view showing a zone plate doublet and a video image thereby according to a second embodiment of the present invention;

9 is a view showing an imaging optical system including a phase plate and an image image thereby;

10 is a view showing an image image obtained by the imaging optical system using the jennik zone plate, and

11 is a cross-sectional view showing a cross section of various volume zone plates.

Claims (14)

Light source; A stage on which the subject is seated; An illumination optical system that focuses incident light incident from the light source and irradiates the test object; And, And an imaging optical system having a plurality of paths through which the reflected light reflected from the surface of the test object travels, and expanding and forming the reflected light traveling in each path. The method of claim 1, The imaging optical system further includes a plurality of image detectors installed to correspond to the plurality of paths, respectively, and configured to detect reflected light traveling along the path. The method of claim 2, And the image detector comprises a CCD sensor. The method of claim 2, And the imaging optical system includes a plurality of zone plates each configured to enlarge and image reflected light traveling along the plurality of paths. The method of claim 4, wherein And the plurality of zone plates are arranged in parallel to correspond to respective paths through which the reflected light travels, and image the reflected light traveling along the path with the corresponding image detector. The method of claim 5, The imaging optical system includes a multi-capillary tube branching a path of the reflected light, and the reflected light reflected from the surface of the test object is incident into the multi-capillary tube and splits along a path formed by each capillary. Surface defect inspection apparatus. The method of claim 5, The imaging optical system further includes a plurality of fine mirrors branching the path of the reflected light, wherein the reflected light reflected from the surface of the test object is reflected to each of the fine mirrors to form a plurality of paths. Surface Defect Inspection System The method according to claim 6 or 7, And reflecting light traveling along the respective paths is irradiated in a direction perpendicular to the corresponding zone plate. The method of claim 5, And the zone plate forms a plurality of two-dimensional images having different focal points into the image detector, and the image detector acquires a three-dimensional shape using the plurality of two-dimensional images. 10. The method of claim 9, And the zone plate comprises a zone plate doublet including diffraction gratings having different focal lengths. 10. The method of claim 9, And the zone plate comprises a Zernike zone plate which generates a phase difference of 0.5 [pi] with respect to light transmitted while being diffracted and light diffracted. 10. The method of claim 9, And a phase plate in front of the zone plate for inducing a phase difference of reflected light passing through the zone plate. 10. The method of claim 9, And the zone plate comprises a volume zone plate having a diffraction grating formed to be inclined with a direction in which the reflected light is irradiated. The method of claim 1, And the light source irradiates light having a wavelength in the range of 10 to 15 nm.

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