KR102649358B1 - EUV mask inspection device and EUV mask inspection method - Google Patents

Abstract

An EUV mask inspection device is provided. The EUV mask inspection device includes a stage on which an EUV mask is placed, a light source for irradiating EUV light to the EUV mask, a first group of EUV light reflected and diffracted after being irradiated to a target area of the EUV mask at a first angle, An objective lens for focusing the second group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a second angle, collecting the first group EUV light focused through the objective lens to form a first spatial area A detection array for acquiring an image, collecting the second group of EUV light to obtain a second spatial domain image, and converting the first and second spatial domain images to the frequency domain to produce first and second frequency domain images, respectively. It may include an image conversion unit configured to obtain a target frequency domain image by combining the first and second frequency domain images, and to obtain a target spatial domain image by converting the target frequency domain image into a spatial domain.

Description

EUV mask inspection device and EUV mask inspection method {EUV mask inspection device and EUV mask inspection method}

The present invention relates to an EUV mask inspection device and an EUV mask inspection method, and more specifically, to an EUV mask inspection device and an EUV mask inspection method using EUV light.

The application of high-NA (0.55 NA) EUV exposure equipment to the mass production process to manufacture semiconductors more finely is imminent. Due to the nature of EUV exposure equipment using the Step & Scan system, defects in the EUV mask are repeatedly transferred to the wafer, so the introduction of a device that can verify mask defects and contamination in advance can increase the yield of the process.

Even when defects and contamination of the mask are identified during the EUV exposure process, semiconductor manufacturing costs can be lowered by applying the repaired mask to the mass production process through a process of correcting pattern defects or cleaning contaminants rather than remanufacturing the mask. . Even if the mask correction and cleaning process is carried out, there is a way to check whether the correction was successful through SEM review after directly exposing the wafer with an exposure machine.

However, because the cost and verification period are long, it is necessary to verify in advance the effect of mask defects on the wafer by measuring the EUV mask aerial image using a microscope that can depict the optical system of the High NA EUV exposure machine. In addition, the mask for the EUV exposure process is made of 40 pairs of Mo/Si multilayer thin films based on Bragg's law to maximize EUV reflection efficiency according to the EUV light characteristics of the 13.5nm wavelength. EUV masks can be evaluated for surface defects using existing DUV (deep ultraviolet) or E-beam, but phase defects occurring inside a multilayer thin film can only be accurately measured in the mask space through inspection using EUV light, which can be measured through EUV actinic inspection. It is called technology.

Conventionally, high-NA EUV mask inspection technology using EUV light and an objective lens with NA of 0.55 is being studied. Conventional high-NA EUV mask inspection technology is conducting research to image EUV mask space images using a multi-layer thin film mirror-based projection optical system, and research is being conducted on EUV mask space image measurement technology using a 0.55 NA zone plate lens for EUV. there is. In order to image a high-NA EUV mask space image using a multi-layer thin film mirror, multiple mirrors must be used and many technologies are required to install and manufacture the mirrors. For this reason, research is mainly conducted using a high-NA Fresnel zone plate lens, which uses the principle of diffraction to collect EUV light and form an image, as an objective lens. The Fresnel zone plate is composed of a transmittance zone and an opaque zone, and the two zones are referred to as the grating zone. The grating zone acts as a diffraction grating for the incident EUV light and forms a mask space image through constructive interference at the focal point to form a mask. inspect.

However, in order to apply a high-NA Fresnel zone plate lens to a mask inspection device, there are limitations due to the high level of difficulty in manufacturing the lens, as is the case with multilayer thin film mirrors. In order to converge the EUV light incident on the outside of the Fresnel zone plate, a grating zone with a pitch size of several tens of nanometers is required, and because it is sensitive to manufacturing errors, its manufacturing cost is also tens of millions of won. The EUV mask inspection device using the High-NA Fresnel zone plate has a very short depth of focus of about 360 nm as the size of the lens increases, and if it exceeds this, spherical aberration and image contrast deteriorate. occurs and if the angle deviates by more than 0.02° with respect to the incident EUV light, aspheric aberration and field curvature aberration occur, so even if a High-NA Fresnel zone plate is manufactured and applied to an inspection device, there are limits to ultra-precision alignment.

One technical problem to be solved by the present invention is to provide an EUV mask inspection device and an EUV mask inspection method using a 0.33NA Fresnel zone plate.

Another technical problem to be solved by the present invention is to provide an EUV mask inspection device and an EUV mask inspection method that can derive results using a 0.55NA Fresnel zone plate through a 0.33NA Fresnel zone plate.

Another technical problem that the present invention aims to solve is to provide an EUV mask inspection device and an EUV mask inspection method that can be used in the 5 nm node or lower level semiconductor manufacturing process.

The technical problems to be solved by the present invention are not limited to those described above.

In order to solve the above-mentioned technical problems, the present invention provides an EUV mask inspection device.

According to one embodiment, the EUV mask inspection device includes a stage on which an EUV mask is placed, a light source for irradiating EUV light to the EUV mask, and a light source that is irradiated to a target area of the EUV mask at a first angle and then reflected and diffracted. An objective lens for focusing group 1 EUV light, a second group EUV light irradiated to the target area of the EUV mask at a second angle and then reflected and diffracted, and collecting the first group EUV light focused through the objective lens. a detection array for acquiring a first spatial domain image, collecting the second group EUV light to obtain a second spatial domain image, and converting the first and second spatial domain images into the frequency domain to obtain first and second spatial domain images, respectively. An image conversion unit for obtaining a second frequency domain image, combining the first and second frequency domain images to obtain a target frequency domain image, and converting the target frequency domain image into a spatial domain to obtain a target spatial domain image. It can be included.

According to one embodiment, the first group EUV light and the second group EUV light focused by the objective lens may include diffracted light of different orders.

According to one embodiment, the first group EUV light focused by the objective lens includes 0th order diffraction light and nth order diffraction light, and the second group EUV light includes 0th order diffraction light and mth order diffraction light. May include light. (n and m are different natural numbers)

According to one embodiment, the target spatial domain image may include a spatial domain image acquired through an objective lens having a higher numerical aperture (NA) than the objective lens.

According to one embodiment, the first and second spatial domain images include spatial domain images acquired through an objective lens of 0.33NA, and the target spatial domain image includes a spatial domain image acquired through an objective lens of 0.55NA. may include.

According to one embodiment, the target spatial domain image may include a higher resolution than the first and second spatial domain images.

According to one embodiment, the first and second spatial domain images are respectively converted into the first and second frequency domain images through Fourier transform, and the target frequency domain image is converted into the first and second frequency domain images through an inverse Fourier transform. It may include being converted into the target spatial region image through (transform).

According to one embodiment, the EUV mask inspection device includes a concave multilayer thin film mirror that focuses the EUV light emitted from the light source, and a planar multilayer thin film that guides the EUV light focused from the concave multilayer thin film mirror to the EUV mask. It may further include a reflection unit including a mirror.

According to one embodiment, the EUV mask inspection device further includes a control unit that inversely calculates the angle of the EUV light irradiated to the EUV mask and controls the positions and angles of the concave multilayer thin film mirror and the planar multilayer thin film mirror. can do.

According to one embodiment, the objective lens may include a Fresnel Zone Plate.

In order to solve the above-mentioned technical problems, the present invention provides an EUV mask inspection method.

According to one embodiment, the EUV mask inspection method includes first group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a first angle, and then being irradiated to the target area of the EUV mask at a second angle. Focusing the reflected and diffracted second group EUV light through an objective lens, collecting the focused first group EUV light to obtain a first spatial domain image, and collecting the second group EUV light to obtain a second spatial domain image. Obtaining a domain image, converting the first and second spatial domain images to a frequency domain to obtain first and second frequency domain images, respectively, and synthesizing the first and second frequency domain images to target After acquiring the frequency domain image, the method may include converting the target frequency domain image into a spatial domain to obtain a target spatial domain image.

According to one embodiment, in the step of focusing the first group and the second group EUV light, the first group and the second group EUV light focused through the objective lens may include diffracted light of different orders. there is.

According to one embodiment, the first and second spatial domain images include spatial domain images acquired through an objective lens of 0.33NA, and the target spatial domain image includes a spatial domain image acquired through an objective lens of 0.55NA. may include.

According to one embodiment, focusing the first group and the second group EUV light includes irradiating the first EUV light at a first angle to a target area of the EUV mask, to the target area of the EUV mask, Irradiating second EUV light at a second angle different from the first angle, focusing the first group EUV light reflected and diffracted after the first EUV light is irradiated to the EUV mask, and the second EUV light After EUV light is irradiated to the EUV mask, it may include focusing the reflected and diffracted second group EUV light.

An EUV mask inspection device according to an embodiment of the present invention includes a stage on which an EUV mask is placed, a light source for irradiating EUV light to the EUV mask, and a target area of the EUV mask that is irradiated at a first angle and then reflected and diffracted. An objective lens (0.33NA Fresnel zone plate) for focusing the first group EUV light and the second group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a second angle, and focused through the objective lens. a detection array for collecting the first group EUV light to obtain a first spatial domain image, and collecting the second group EUV light to obtain a second spatial domain image, and the first and second spatial domain images First and second frequency domain images are obtained by converting to the frequency domain, respectively, the first and second frequency domain images are synthesized to obtain a target frequency domain image, and the target frequency domain image is converted to the spatial domain to obtain a target frequency domain image. It may include an image conversion unit that acquires a spatial domain image.

Additionally, the first group EUV light and the second group EUV light focused by the objective lens may include diffracted light of different orders. Specifically, the first group EUV light focused by the objective lens includes 0th order diffraction light and nth order diffraction light, and the second group EUV light includes 0th order diffraction light and mth order diffraction light. It can be done (n and m are different natural numbers). Accordingly, although a 0.33NA objective lens (Fresnel zone plate) is used for EUV mask inspection, results using a 0.55NA objective lens (Fresnel zone plate) can be obtained.

Figure 1 is a diagram for explaining a conventional EUV mask inspection device using a Fresnel zone plate.
Figure 2 is a diagram for explaining mask inspection through a 0.55NA Fresnel zone plate.
Figure 3 is a diagram for explaining mask inspection through a 0.33NA Fresnel zone plate.
Figure 4 is a diagram for explaining an EUV mask inspection device according to an embodiment of the present invention.
Figure 5 is a diagram for explaining the first EUV light and the second EUV light irradiated to the EUV mask at different angles.
Figure 6 is a diagram for explaining the angle of the first EUV light irradiated to the EUV mask.
Figure 7 is a diagram for explaining the angle of the second EUV light irradiated to the EUV mask.
Figure 8 is a diagram for explaining the first group EUV light reflected and diffracted from the EUV mask.
Figure 9 is a diagram for explaining the second group EUV light reflected and diffracted from the EUV mask.
FIG. 10 is a diagram illustrating first and second spatial domain images acquired through a detection array included in an EUV mask inspection device according to an embodiment of the present invention.
FIG. 11 is a diagram illustrating first and second frequency domain images obtained through an image conversion unit included in the EUV mask inspection device according to an embodiment of the present invention.
FIG. 12 is a diagram illustrating a target frequency domain image acquired through an image conversion unit included in the EUV mask inspection device according to an embodiment of the present invention.
FIG. 13 is a diagram illustrating a target spatial region image acquired through an image conversion unit included in the EUV mask inspection device according to an embodiment of the present invention.
Figure 14 is a diagram to explain an example of an algorithm used to acquire a target frequency domain.
Figure 15 is a diagram for explaining the position adjustment algorithm among the algorithms used to acquire the target frequency domain.
Figure 16 is a flowchart for explaining an EUV mask inspection method according to an embodiment of the present invention.
Figure 17 is a flowchart specifically explaining step S100 of the EUV mask inspection method according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical idea of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and so that the spirit of the invention can be sufficiently conveyed to those skilled in the art.

In this specification, when an element is referred to as being on another element, it means that it may be formed directly on the other element or that a third element may be interposed between them. Additionally, in the drawings, the thicknesses of films and regions are exaggerated for effective explanation of technical content.

Additionally, in various embodiments of the present specification, terms such as first, second, and third are used to describe various components, but these components should not be limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. Additionally, in this specification, 'and/or' is used to mean including at least one of the components listed before and after.

In the specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "include" or "have" are intended to designate the presence of features, numbers, steps, components, or a combination thereof described in the specification, but are not intended to indicate the presence of one or more other features, numbers, steps, or components. It should not be understood as excluding the possibility of the presence or addition of elements or combinations thereof. Additionally, in this specification, “connection” is used to mean both indirectly connecting and directly connecting a plurality of components.

Additionally, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Conventional EUV mask inspection

Figure 1 is a diagram for explaining a conventional EUV mask inspection device through a Fresnel zone plate, Figure 2 is a diagram for explaining mask inspection through a 0.55NA Fresnel zone plate, and Figure 3 is a diagram for explaining a 0.33NA Fresnel zone. This is a drawing to explain mask inspection through a plate.

Referring to FIG. 1, in the conventional EUV mask inspection device, the EUV light (L) emitted from the light source 200 is guided to the EUV mask (EM) through a reflection portion consisting of a plurality of mirrors 310 and 320, The EUV light reflected and diffracted by the EUV mask (EM) is focused through the Fresnel zone plate 400, and the light focused on the Fresnel zone plate 400 is collected through the detection array 500 to create a spatial domain image. By acquiring this, defects in the EUV mask can be inspected.

In the case of a conventional device for inspecting defects in an EUV mask using the above-described method, the spatial area obtained through the detection array 500 according to the numerical aperture (NA) of the Fresnel zone plate 400. The resolution of the image may vary. Specifically, when a Fresnel zoneplate 400 with a relatively high NA (e.g., 0.55NA) is used, the Fresnel zoneplate 400 with a relatively low NA (e.g., 0.33NA) is used. Compared to the case where is used, a relatively wide range of diffracted light can be focused, so a relatively high-resolution spatial domain image can be obtained.

For example, when the 0.55NA Fresnel zone plate 400 is used, as shown in FIG. 2, among the light diffracted through the EUV mask 400, 0th order diffracted light, ±1st order diffracted light, and As all ±2nd order diffracted light can be focused, relatively high-resolution spatial domain images can be obtained. In contrast, when the 0.33NA Fresnel zone plate 400 is used, as shown in FIG. 3, the 0th order diffraction light and the ±1st order diffraction light among the light diffracted through the EUV mask 400 are focused. As a result, a relatively low-resolution spatial domain image can be obtained.

As a result, when the 0.55NA Fresnel zone plate 400 is used, relatively high-resolution spatial domain images can be acquired compared to when the 0.33NA Fresnel zone plate 400 is used, allowing defect inspection of EUV masks Reliability can be improved.

However, in the case of the 0.55NA Fresnel zone plate 400, the manufacturing difficulty and price are significantly high, and there are problems such as a decrease in depth of focus due to an increase in NA and technical limitations for ultra-precision alignment.

Accordingly, the EUV mask inspection device and inspection method according to an embodiment of the present invention uses a 0.33NA Fresnel zone plate in inspecting the EUV mask, but produces the same results as when a 0.55NA Fresnel zone plate was used. Provides an EUV mask inspection device and inspection method that can be used.

EUV mask inspection according to an embodiment of the present invention

FIG. 4 is a diagram for explaining an EUV mask inspection device according to an embodiment of the present invention, and FIG. 5 is a diagram for explaining the first EUV light and the second EUV light irradiated to the EUV mask at different angles, and FIG. 6 is a diagram for explaining the angle of the first EUV light irradiated to the EUV mask, FIG. 7 is a diagram for explaining the angle of the 2nd EUV light irradiated to the EUV mask, and FIG. 8 is a diagram for explaining the angle of the 2nd EUV light irradiated to the EUV mask. This is a diagram for explaining the first group EUV light, and FIG. 9 is a diagram for explaining the second group EUV light reflected and diffracted from the EUV mask.

Referring to FIG. 4, the EUV mask inspection device according to an embodiment of the present invention includes a stage 100, a light source 200, reflectors 310 and 320, an objective lens 400, a detection array 500, and an image. It may include a change unit (not shown) and a control unit (not shown). Below, each configuration is explained.

The stage 100 may provide a place where an EUV mask (EM) is placed. That is, the EUV mask (EM) may be placed on the stage 100.

The light source 200 may emit EUV light. According to one embodiment, the light source 200 may emit coherent EUV light with a wavelength of 13.5 nm, which is emitted by a high-order harmonic wave generation method.

The reflection units 310 and 320 may include a concave multilayer thin film mirror 310 and a planar multilayer thin film mirror 320. The concave multilayer thin film mirror 310 can focus the EUV light emitted from the light source 200. In contrast, the planar multilayer thin film mirror 320 may guide the EUV light focused from the concave multilayer thin film mirror 310 to the target area (TA) of the EUV mask (EM). According to one embodiment, the target area (TA) may be defined as an area to be inspected within the EUV mask (EM).

That is, the EUV light emitted from the light source 200 sequentially passes through the concave multilayer thin film mirror 310 and the planar multilayer thin film mirror 320 and then is provided to the target area (TA) of the EUV mask (EM). It can be.

According to one embodiment, a plurality of EUV lights may be provided to the target area (TA) of the EUV mask (EM). For example, as shown in FIG. 5 , the first EUV light L ₁ and the second EUV light L ₂ may be provided to the target area TA of the mask EM. The first EUV light L ₁ and the second EUV light L ₂ may have different angles at which they are irradiated to the target area TA of the EUV mask EM. For example, the first EUV light L ₁ may be irradiated to the target area TA of the mask EM at a first angle θ ₁ . In contrast, the second EUV light L ₂ may be irradiated to the target area TA of the mask EM at a second angle θ ₂ .

More specifically, as shown in FIG. 6, the first EUV light L ₁ may be irradiated to form a first angle θ ₁ with the normal line Z of the upper surface of the EUV mask EM. . Alternatively, as shown in FIG. 7 , the second EUV light L ₂ may be irradiated to form a second angle θ ₂ with the normal line Z of the upper surface of the EUV mask EM. According to one embodiment, the second angle (θ ₂ ) may be greater than the first angle (θ ₁ ). In contrast, according to another implementation, the second angle (θ ₂ ) may be smaller than the first angle (θ ₁ ).

According to one embodiment, the angle of EUV light irradiated to the EUV mask (EM) may be controlled through the concave multilayer thin film mirror 310 and the planar multilayer thin film mirror 320. The positions and angles of the concave multilayer thin film mirror 310 and the planar multilayer thin film mirror 320 may be controlled through the control unit (not shown). The control unit inversely calculates the angle of the EUV light irradiated to the EUV mask (EM) to control the positions and angles of the concave multilayer thin film mirror 310 and the planar multilayer thin film mirror 320. .

EUV light irradiated to the EUV mask (EM) may be reflected and diffracted by the EUV mask (EM). According to one embodiment, the first EUV light L ₁ reflected and diffracted in the target area TA of the EUV mask EM may be defined as the first group EUV light GL ₁ . In contrast, the second EUV light (L ₂ ) reflected and diffracted in the target area (TA) of the EUV mask (EM) may be defined as second group EUV light (GL ₂ ).

The objective lens 400 may focus EUV light reflected and diffracted in the target area (TA) of the EUV mask (EM). For example, the objective lens 400 may include a 0.33NA Fresnel Zone Plate.

The objective lens 400 may focus the first group EUV light (GL ₁ ) and the second group EUV light (GL ₂ ). According to one embodiment, the first group EUV light (FL ₁ ) and the second group EUV light (FL ₂ ) focused through the objective lens 400 may include diffracted light of different orders.

For example, as shown in FIG. 8 , the focused first group EUV light FL ₁ may include 0th order diffraction light, -1st order diffraction light, and +1st order diffraction light. In contrast, as shown in FIG. 9 , the focused second group EUV light (FL ₂ ) may include 0th order diffraction light, -1st order diffraction light, and -2nd order diffraction light.

FIG. 10 is a diagram for explaining first and second spatial domain images obtained through a detection array included in an EUV mask inspection device according to an embodiment of the present invention, and FIG. 11 is a diagram illustrating an EUV mask according to an embodiment of the present invention. It is a diagram for explaining the first and second frequency domain images acquired through the image conversion unit included in the inspection device, and Figure 12 shows the target acquired through the image conversion unit included in the EUV mask inspection device according to an embodiment of the present invention. It is a diagram for explaining a frequency domain image, FIG. 13 is a diagram for explaining a target spatial domain image acquired through an image conversion unit included in the EUV mask inspection device according to an embodiment of the present invention, and FIG. 14 is a target frequency domain image. This is a diagram to explain an example of an algorithm used for acquisition, and FIG. 15 is a diagram to explain a position adjustment algorithm among the algorithms used to acquire a target frequency region.

EUV light focused through the objective lens 400 may be collected through the detection array 500. The detection array 500 can acquire a spatial domain image through collected EUV light. More specifically, the detection array 500 may acquire a first spatial domain image (SI ₁ ) through the first group EUV light (FL ₁ ) focused through the objective lens 400. Additionally, the detection array 500 may acquire a second spatial domain image (SI ₂ ) through the second group EUV light (FL ₂ ) focused through the objective lens 400.

As described above, the focused first group EUV light (FL ₁ ) and the focused second group EUV light (FL ₂ ) include diffracted light of different orders, and thus the first spatial domain image (SI ₁ ) And the second spatial region image SI ₂ , as shown in FIG. 10 , may display images of the same region (eg, target region) but with different appearances.

The image converter (not shown) may convert the first and second spatial domain images (SI ₁ and SI ₂ ) into the frequency domain. More specifically, the image converter may convert the first spatial domain image (SI ₁ ) into a first frequency domain image (FI ₁ ). Additionally, the image converter may convert the second spatial domain image (SI ₂ ) into a second frequency domain image (FI ₂ ). According to one embodiment, the first and second spatial domain images (SI ₁ , SI ₂ ) are converted into the first and second frequency domain images (FI ₁ , FI ₂ ) through Fourier transform. You can. The first and second frequency domain images FI ₁ and FI ₂ may be displayed as shown in FIG. 11 .

In addition, the image converter obtains a target frequency domain image (TFI) by combining the first and second frequency domain images (FI ₁ and FI ₂ ), and converts the target frequency domain image (TFI) into a spatial domain. A target spatial image (TSI) can be acquired. According to one embodiment, the target frequency domain image (TFI) may be converted into the target spatial domain image (TSI) through an inverse Fourier transform. The target frequency domain image (TFI) may be displayed as shown in FIG. 12, and the target spatial domain image (TSI) may be displayed as shown in FIG. 13. According to one embodiment, the target frequency domain image may be obtained through an algorithm as shown in FIGS. 14 and 15.

The target frequency domain image (TFI) and the target spatial domain image (TSI) are images acquired through an objective lens (0.55NA Fresnel zone plate) having a higher numerical aperture than the objective lens (0.33NA Fresnel zone plate). It may be the same as Accordingly, the target spatial domain image (TFI) may have higher resolution than the first and second spatial domain images (SI ₁ and SI ₂ ).

As a result, the EUV mask inspection device according to an embodiment of the present invention acquires a plurality of spatial domain images through an objective lens (0.33NA Fresnel zone plate) with a relatively low numerical aperture, and then Each domain image can be converted to a frequency domain image. Additionally, a target frequency domain image can be obtained by combining a plurality of converted frequency images, and a target spatial domain image can be obtained by inversely transforming the obtained target frequency domain image.

In particular, as multiple spatial domain images are acquired through group EUV light containing diffracted light of different orders, spatial domain images acquired through an objective lens (0.55NA Fresnel zone plate) with a relatively high numerical aperture A target spatial area image such as can be obtained.

More specifically, for an objective lens with a relatively high numerical aperture (0.55NA Fresnel zone plate), a relatively wide range of diffracted light (e.g., 0th order diffracted light, ±1st order diffracted light, and ±2 By being able to focus diffracted light, relatively high-resolution spatial domain images can be obtained.

In contrast, the EUV mask inspection device according to an embodiment of the present invention uses an objective lens (0.33NA Fresnel zone plate) with a relatively low numerical aperture to detect diffracted light in a relatively narrow range (e.g., 0th order diffraction). Since it focuses light, -1st order diffraction light, +1st order diffraction light), relatively low-resolution spatial domain images can be obtained. However, by irradiating a plurality of EUV lights at different angles to the EUV mask EM, a plurality of low-resolution spatial domain images can be obtained. The acquired plurality of low-resolution spatial domain images may be synthesized (multiple frequency domain images are acquired through Fourier transform and then synthesized into a target frequency domain image). Accordingly, a high-resolution spatial-domain image can be acquired through a plurality of low-resolution spatial-domain images (the target frequency-domain image is converted into a target spatial-domain image through inverse Fourier transform).

In particular, a plurality of low-resolution spatial domain images are acquired through a plurality of EUV lights containing diffracted light of different orders as shown in <Table 1> below, and an objective lens with a relatively high numerical aperture (0.55NA Fresnel It may include diffracted light in the same range as the EUV light focused through the zone plate.

Objective Lens Type Focused EUV light Diffracted light contained by focused group EUV light 0.55NA Group 1 EUV light 0th order diffraction light, ±1st order diffraction light, ±2nd order diffraction light 0.33NA Group 1 EUV light 0th order diffraction light, -1st order diffraction light, +1st order diffraction light 2nd group EUV light 0th order diffraction light, -1st order diffraction light, -2nd order diffraction light Third group EUV light 0th order diffraction light, +1st order diffraction light, +2nd order diffraction light

Accordingly, the EUV mask inspection device according to an embodiment of the present invention inspects the EUV mask through an objective lens (0.33NA Fresnel zone plate) with a relatively low numerical aperture, but uses an objective lens with a relatively high numerical aperture. The same results as those of inspecting the EUV mask can be obtained through (0.55NA Fresnel zone plate).

Above, the EUV mask inspection device according to an embodiment of the present invention has been described. Hereinafter, an EUV mask inspection method according to an embodiment of the present invention will be described.

FIG. 16 is a flowchart for explaining an EUV mask inspection method according to an embodiment of the present invention, and FIG. 17 is a flowchart for specifically explaining step S100 of the EUV mask inspection method according to an embodiment of the present invention.

Referring to Figures 16 and 17, the first group EUV light is reflected and diffracted after being irradiated to the target area of the EUV mask at a first angle, and the first group of EUV lights is reflected and diffracted after being irradiated to the target area of the EUV mask at a second angle. The second group EUV light may be focused through the objective lens (S100).

According to one embodiment, the step of focusing the first and second group EUV lights (S100) includes irradiating the first EUV light at a first angle to a target area of the EUV mask (S110), the EUV mask Irradiating second EUV light to the target area at a second angle different from the first angle (S120), the first group EUV light is reflected and diffracted after the first EUV light is irradiated to the EUV mask. It may include a step of focusing (S130), and a step of focusing the second group EUV light that is reflected and diffracted after the EUV light is irradiated to the EUV mask (S140).

The first group EUV light and the second group EUV light focused through the objective lens may include diffracted light of different orders. For example, the first group of focused EUV light may include 0th order diffraction light, -1st order diffraction light, and +1st order diffraction light. Alternatively, the focused second group EUV light may include 0th order diffraction light, -1st order diffraction light, and -2nd order diffraction light.

The focused first group EUV light may be collected to obtain a first spatial domain image, and the focused second group EUV light may be collected to obtain a second spatial domain image (S200).

Thereafter, the first and second spatial domain images are converted to the frequency domain to obtain first and second frequency domain images, respectively (S300), and the first and second frequency domain images are synthesized to obtain a target frequency domain image. The target frequency domain image can be converted to a spatial domain to obtain a target spatial domain image (S400).

According to one embodiment, the first and second spatial domain images are the same as spatial domain images acquired through an objective lens of 0.33NA, and the target spatial domain image is the spatial domain image acquired through an objective lens of 0.55NA. It can be the same. That is, the EUV mask inspection method according to an embodiment of the present invention inspects the EUV mask through a 0.33NA objective lens, but can obtain the same results as the EUV mask inspection result through a 0.55NA objective lens.

Above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to the specific embodiments and should be interpreted in accordance with the appended claims. Additionally, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

100: Stage
200: light source
310: Concave multilayer thin film mirror
320: Planar multilayer thin film mirror
400: Objective lens
500: detection array

Claims (14)

A stage where the EUV mask is placed;
a light source for irradiating EUV light to the EUV mask;
Collects the first group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a first angle, and the second group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a second angle. belonging to the objective lens;
a detection array configured to collect the first group EUV light focused through the objective lens to obtain a first spatial domain image and to collect the second group EUV light to obtain a second spatial domain image; and
Convert the first and second spatial domain images to the frequency domain to obtain first and second frequency domain images, respectively, synthesize the first and second frequency domain images to obtain a target frequency domain image, and obtain the target frequency domain image. An EUV mask inspection device including an image conversion unit that converts a frequency domain image into a spatial domain to obtain a target spatial domain image.
According to claim 1,
The first group EUV light and the second group EUV light focused by the objective lens include diffracted light of different orders.
According to clause 2,
The first group EUV light focused by the objective lens includes 0th order diffraction light and nth order diffraction light, and the second group EUV light includes 0th order diffraction light and mth order diffraction light. An EUV mask Inspection device.
(n and m are different natural numbers)
According to claim 1,
The target spatial domain image includes a spatial domain image acquired through an objective lens having a higher numerical aperture (NA) than the objective lens.
According to clause 4,
EUV mask inspection wherein the first and second spatial domain images include spatial domain images acquired through a 0.33NA objective lens, and the target spatial domain image includes a spatial domain image acquired through a 0.55NA objective lens. Device.
According to clause 4,
The target spatial region image has a higher resolution than the first and second spatial region images.
According to claim 1,
The first and second spatial domain images are respectively converted into the first and second frequency domain images through Fourier transform,
An EUV mask inspection device comprising converting the target frequency domain image into the target spatial domain image through an inverse Fourier transform.
According to claim 1,
EUV mask inspection further comprising a reflection unit including a concave multilayer thin film mirror for focusing the EUV light emitted from the light source, and a planar multilayer thin film mirror for guiding the EUV light focused from the concave multilayer thin film mirror to the EUV mask. Device.
According to clause 8,
The EUV mask inspection device further includes a control unit configured to inversely calculate the angle of the EUV light irradiated to the EUV mask and control the positions and angles of the concave multilayer thin film mirror and the planar multilayer thin film mirror.
According to claim 1,
The objective lens is an EUV mask inspection device including a Fresnel Zone Plate.
The first group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a first angle and the second group EUV light reflected and diffracted after being irradiated to the target area of the EUV mask at a second angle are transmitted through an objective lens. Focusing through;
acquiring a first spatial domain image by collecting the focused first group EUV light, and acquiring a second spatial domain image by collecting the second group EUV light;
converting the first and second spatial domain images into a frequency domain to obtain first and second frequency domain images, respectively; and
An EUV mask inspection method comprising obtaining a target frequency domain image by combining the first and second frequency domain images, and then converting the target frequency domain image into a spatial domain to obtain a target spatial domain image.
According to claim 11,
In the step of focusing the first group and the second group EUV light, the first group and the second group EUV light focused through the objective lens include diffracted light of different orders.
According to claim 11,
EUV mask inspection wherein the first and second spatial domain images include spatial domain images acquired through a 0.33NA objective lens, and the target spatial domain image includes a spatial domain image acquired through a 0.55NA objective lens. method.
According to claim 11,
The step of focusing the first group and the second group EUV light,
Irradiating first EUV light to a target area of an EUV mask at a first angle;
irradiating second EUV light to the target area of the EUV mask at a second angle different from the first angle;
After the first EUV light is irradiated to the EUV mask, focusing the reflected and diffracted first group EUV light; and
An EUV mask inspection method comprising focusing the reflected and diffracted second group EUV light after the second EUV light is irradiated to the EUV mask.

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