Apparatus and method for improving EUV mask inspection accuracy

Abstract

An apparatus for improving EUV mask inspection accuracy is provided. The apparatus for improving EUV mask inspection accuracy may comprise a light source which generates EUV light, a beam splitter which splits the EUV light generated by the light source into first EUV light and second EUV light, an optical system which controls the path of the first EUV light split by the beam splitter so as to radiate the first EUV light onto an EUV mask, a first detector which collects diffracted light diffracted from the EUV mask by the first EUV light radiated onto the EUV mask and acquires a diffraction pattern for the EUV mask, a second detector which collects the second EUV light split by the beam splitter and detects the intensity value of the second EUV light, and an image acquisition unit which corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected by the second detector and acquires an image of the EUV mask using the corrected intensity value of the diffraction pattern.

Description

Device and method for improving EUV mask inspection accuracy

[0001] The present invention relates to an apparatus and method for improving the accuracy of EUV mask inspection.

[0002] EUV light has a short wavelength of 13.5 nm and, due to the high photon energy associated with it, possesses optical characteristics that allow it to be easily absorbed by most materials, including air. Accordingly, since EUV masks are fabricated in the form of more than 40 pairs of Mo / Si-based multilayer thin films, it is possible to evaluate the presence or absence of surface defects using DUV (deep Ultraviolet) or E-beam. However, phase defects occurring within the multilayer thin film can only be detected through inspection using EUV light, which enables the measurement of the mask space image—the intensity profile of the EUV light formed on the wafer—and this is called actinic inspection technology.

[0003] Conventionally, to improve the mask imaging performance transferred to the wafer inside the exposure machine, methods were used to increase the numerical aperture (NA) to secure the resolution of the optical system (resolution ∝ λ / NA) or to reconstruct the optical system.

[0004] For example, Korean Patent Publication No. 10-2693199 (April 24, 2023) describes an EUV (Extreme Ultraviolet) light source that outputs EUV light with a wavelength between 5 nm and 15 nm; a multilayer reflection zone plate having an EUV reflective multilayer film and a zone plate pattern formed on a planar substrate; and an EUV illumination unit that generates EUV illumination light by acquiring the first-order diffracted light reflected after irradiating the EUV light output from the EUV light source onto the multilayer reflection zone plate; an aperture that reduces the linewidth of the light wavelength irradiated from the EUV illumination unit to provide monochromatic light or reduces the light irradiation area; a transmissive zone plate that focuses the reflected or scattered light after the light passing through the aperture is irradiated onto an EUV mask to form magnified light; and an EUV mask corresponding to the light passing through the transmissive zone plate. An EUV mask inspection device is disclosed, comprising an image sensor that measures the intensity of light through a measurement light.

[0005] As another example, Korean Patent Publication No. 10-2211513 (October 26, 2020) describes a Coherent EUV light source generated through the generation of higher-order harmonics, an X-ray toroidal mirror that focuses the generated EUV light at different focal lengths in the direction perpendicular to the incident plane and the direction perpendicular to the incident plane, an X-ray planar mirror that directs the light reflected from the X-ray toroidal mirror to a mask, an X-ray beam splitter that transmits a portion of the beam focused by the X-ray toroidal mirror and reflects a portion of it, a photodetector that detects the beam reflected by the X-ray beam splitter, an anamorphic zoneplate lens that focuses the beam transmitted by the X-ray beam splitter onto a mask and has the same focal length in the direction perpendicular to the incident plane and simultaneously has different numerical apertures (NA) in the direction perpendicular to the incident plane and the direction perpendicular to the incident plane, and a reflective type on the top An EUV (extreme ultra-violet) mask pattern image measuring device is disclosed, comprising a stage for scanning the reflective EUV mask in the y-axis or y-axis direction to acquire an image, and a detector array for detecting the energy of the reflected interference EUV light when reflected by the EUV mask, and comprising anamorphic photo sensors of different sizes in the direction horizontal and perpendicular to the incident plane of the detector array.

[0006] However, expanding the optical system is essential to reconfigure the optical system or use methods to increase the NA of the optical system, and the expansion of the optical system is depth of focus (depth of focus ∝ λ / NA 2In relation to ), there is a problem in that not only is the tolerance for ultra-precision alignment reduced, but the manufacturing process of the optical system is also very difficult, and the associated cost amounts to tens of millions of won.

[0007] As a means to overcome these problems, coherent diffractive imaging (CDI) technology is being actively researched, which captures light scattered (reflected and diffracted) from an object (e.g., a mask) in the form of a diffraction pattern and restores the original image of the object (e.g., a mask) by phase restoration. However, CDI technology is limited in that its field of view (FOV) is confined to the pattern area irradiated at once, and there is a limitation in that the image shape becomes blurry depending on the shape of the probe. In other words, conventional CDI technology has the problem of low resolution of the mask image. Accordingly, the present invention aims to provide an apparatus and method that can improve the accuracy of mask inspection by utilizing CDI technology while improving the resolution of the mask image.

[0008] The technical problem that the present invention aims to solve is to provide an EUV mask inspection device and an inspection method.

[0009] Another technical problem that the present invention aims to solve is to provide an apparatus and a method for improving the accuracy of EUV mask inspection.

[0010] Another technical problem that the present invention aims to solve is to provide an apparatus and method for improving the accuracy of EUV mask inspection capable of realizing high-resolution images of EUV masks.

[0011] Another technical problem that the present invention aims to solve is to provide an apparatus and method for improving the accuracy of EUV mask inspection that can improve the accuracy of an implemented mask image.

[0012] Another technical problem that the present invention aims to solve is to provide an apparatus and method for improving the accuracy of EUV mask inspection that can improve the reliability of the implemented mask image.

[0013] Another technical problem that the present invention aims to solve is to provide an apparatus and method for improving the accuracy of EUV mask inspection that can improve the productivity of EUV lithography equipment.

[0014] Another technical problem that the present invention aims to solve is to provide an apparatus and method for improving the accuracy of EUV mask inspection that can improve the yield of EUV lithography equipment.

[0015] The technical problems that the present invention aims to solve are not limited to those described above.

[0016] To solve the technical problems described above, the present invention provides an EUV mask inspection accuracy improvement device.

[0017] According to one embodiment, the EUV mask inspection accuracy enhancement device may include a light source that generates EUV light, a beam splitter that separates the EUV light generated from the light source into a first EUV light and a second EUV light, an optical system that controls the path of the first EUV light separated from the beam splitter to irradiate the first EUV light onto an EUV mask, a first detector that collects diffracted light diffracted from the EUV mask by the first EUV light irradiated onto the EUV mask and obtains a diffraction pattern for the EUV mask, a second detector that collects the second EUV light separated from the beam splitter and detects an intensity value of the second EUV light, and an image acquisition unit that corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected through the second detector and obtains an image of the EUV mask using the corrected intensity value of the diffraction pattern.

[0018] According to one embodiment, the first detector collects diffracted light from different regions of the EUV mask to obtain diffraction patterns for each region, and the image acquisition unit may include correcting each intensity value of the obtained diffraction pattern and then using the corrected intensity values ​​of each diffraction pattern as input values ​​for a phase restoration algorithm to obtain an image of the EUV mask.

[0019] According to one embodiment, the second detector may detect the intensity value of the second EUV light whenever the diffracted light is collected from different regions of the EUV mask, and the intensity value of the corrected diffraction pattern may be calculated according to <Equation 1> below.

[0020] <Mathematical Formula 1>

[0021]

[0022] (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region)

[0023] According to one embodiment, the first EUV light is irradiated onto each of the different regions of the EUV mask, wherein the first EUV light irradiated onto adjacent regions among the different regions of the EUV mask may include at least a portion of the overlap.

[0024] According to one embodiment, the beam splitter transmits and reflects the EUV light generated from the light source, wherein the EUV light transmitted through the beam splitter is defined as the first EUV light and the EUV light reflected from the beam splitter is defined as the second EUV light.

[0025] According to one embodiment, the method further includes a mask stage on which the EUV mask is placed, wherein the mask stage may control the position of the EUV mask so that the first EUV light is irradiated to different regions of the EUV mask.

[0026] According to one embodiment, the first EUV light may be irradiated onto the EUV mask at an angle of 6° with respect to the normal direction of the upper surface of the EUV mask.

[0027] According to another embodiment, the EUV mask inspection accuracy enhancement device may include a beam splitter that transmits a portion of EUV light and reflects the remainder; a first detector that collects diffracted light diffracted from an EUV mask by the first EUV light transmitted through the beam splitter and obtains a diffraction pattern for the EUV mask; a second detector that collects a second EUV light reflected from the beam splitter and detects an intensity value of the second EUV light; and an image acquisition unit that corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected through the second detector and obtains an image of the EUV mask using the corrected intensity value of the diffraction pattern.

[0028] According to another embodiment, the first detector collects diffracted light from different regions of the EUV mask to obtain diffraction patterns for each region, the second detector detects the intensity value of the second EUV light whenever diffracted light is collected from different regions of the EUV mask, and the image acquisition unit may include correcting each of the intensity values ​​of the obtained diffraction pattern according to <Equation 1> below and then using the corrected intensity values ​​of each diffraction pattern as input values ​​for a phase restoration algorithm to obtain an image of the EUV mask.

[0029] <Mathematical Formula 1>

[0030]

[0031] (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region)

[0032]

[0033] To solve the technical problems described above, the present invention provides a method for improving the accuracy of EUV mask inspection.

[0034] According to one embodiment, the method for improving the accuracy of EUV mask inspection may include the steps of: generating EUV light; separating the EUV light into a first EUV light and a second EUV light; irradiating the first EUV light onto an EUV mask; collecting diffracted light diffracted from the EUV mask by the first EUV light irradiated onto the EUV mask to obtain a diffraction pattern for the EUV mask; collecting the second EUV light to detect an intensity value of the second EUV light; correcting the intensity value of the diffraction pattern using the intensity value of the second EUV light; and obtaining an image of the EUV mask using the corrected intensity value of the diffraction pattern.

[0035] According to one embodiment, the step of irradiating the first EUV light onto an EUV mask includes irradiating the first EUV light onto each of different regions of the EUV mask, and the step of obtaining intensity values ​​of the diffraction pattern for the EUV mask may include collecting the diffracted light from each of the different regions of the EUV mask and obtaining intensity values ​​of the diffraction pattern for each region.

[0036] According to one embodiment, the step of collecting the second EUV light and detecting the intensity value of the second EUV light may include detecting the intensity value of the second EUV light whenever the first EUV light is irradiated onto each of the different regions of the EUV mask.

[0037] According to one embodiment, the step of correcting the intensity value of the diffraction pattern using the intensity value of the second EUV light may include correcting the intensity values ​​of the multiple diffraction patterns obtained from different regions of the EUV mask using multiple intensity values ​​of the second EUV light detected for different regions of the EUV mask.

[0038] According to one embodiment, the step of acquiring an image of the EUV mask may include acquiring an image of the EUV mask by using a plurality of corrected intensity values ​​of the diffraction patterns as input values ​​for a phase restoration algorithm.

[0039] An EUV mask inspection accuracy enhancement device according to an embodiment of the present invention may include a light source that generates EUV light, a beam splitter that separates the EUV light generated from the light source into a first EUV light and a second EUV light, an optical system that controls the path of the first EUV light separated from the beam splitter to irradiate the first EUV light onto an EUV mask, a first detector that collects diffracted light diffracted from the EUV mask by the first EUV light irradiated onto the EUV mask and obtains a diffraction pattern for the EUV mask, a second detector that collects the second EUV light separated from the beam splitter and detects an intensity value of the second EUV light, and an image acquisition unit that corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected through the second detector and obtains an image of the EUV mask using the corrected intensity value of the diffraction pattern. Accordingly, high-resolution, high-accuracy, and high-reliability mask imaging inspection can be performed.

[0040] That is, the EUV mask inspection accuracy enhancement device according to an embodiment of the present invention can compensate for photon-flux fluctuations caused by EUV light through a simple configuration using a beam splitter, thereby enabling high-resolution, high-accuracy, and high-reliability mask imaging inspection.

[0041] FIG. 1 is a drawing for illustrating an EUV mask inspection accuracy improvement device according to an embodiment of the present invention.

[0042] FIG. 2 is a diagram illustrating EUV light separation using a beam splitter of an EUV mask inspection accuracy improvement device according to an embodiment of the present invention.

[0043] Figure 3 is a diagram for comparing a mask image obtained using an uncorrected diffraction pattern intensity value and a mask image obtained using a corrected diffraction pattern intensity value.

[0044] Figure 4 is a diagram illustrating an example of a state in which regions of an EUV mask are separated.

[0045] Figure 5 is an image of an EUV mask.

[0046] FIG. 6 is a diagram illustrating an example of a state in which first EUV light is irradiated onto separated regions of an EUV mask.

[0047] FIG. 7 is a diagram illustrating an example of a diffraction pattern obtained from each of the separated regions of an EUV mask through a first detector.

[0048] Figure 8 is a diagram illustrating the process of correcting the intensity value of a diffraction pattern.

[0049] Figure 9 is a diagram illustrating the computational processing of the phase restoration algorithm.

[0050] FIG. 10 is a flowchart illustrating a method for improving the accuracy of EUV mask inspection according to an embodiment of the present invention.

[0051] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept 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 to ensure that the disclosed content is thorough and complete and to sufficiently convey the concept of the present invention to those skilled in the art.

[0052] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the films and regions are exaggerated for the effective description of the technical content.

[0053] Additionally, although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. Accordingly, what is referred to as the first component in one embodiment may be referred to as the second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. Furthermore, in this specification, "and / or" is used to mean including at least one of the components listed before and after it.

[0054] In the specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, terms such as "include" or "have" are intended to specify the existence of the features, numbers, steps, components, or combinations thereof described in the specification, and should not be understood as excluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof. Additionally, in this specification, "connection" is used to include both indirectly connecting multiple components and directly connecting them.

[0055] Furthermore, in describing the present invention below, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0056]

[0057] FIG. 1 is a diagram for explaining an EUV mask inspection accuracy enhancement device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining EUV light separation using a beam splitter of an EUV mask inspection accuracy enhancement device according to an embodiment of the present invention, FIG. 3 is a diagram for comparing a mask image obtained using an intensity value of an uncorrected diffraction pattern with a mask image obtained using an intensity value of a corrected diffraction pattern, FIG. 4 is a diagram for explaining an example of a state in which regions of an EUV mask are separated, FIG. 5 is an image of an EUV mask, FIG. 6 is a diagram for explaining an example of a state in which a first EUV light is irradiated onto the separated regions of an EUV mask, FIG. 7 is a diagram for explaining an example of a diffraction pattern obtained from each of the separated regions of an EUV mask through a first detector, FIG. 8 is a diagram for explaining a process of correcting the intensity value of a diffraction pattern, and FIG. 9 is a diagram for explaining a phase restoration algorithm operation processing process.

[0058] Referring to FIG. 1, an EUV mask inspection accuracy enhancement device according to an embodiment of the present invention may include a light source (100), a filter (200), a beam splitter (300), an optical system (410, 420), a mask stage (500), a first detector (610), a second detector (620), and an image acquisition unit (not shown). Each component is described below.

[0059] The light source (100) can generate and emit EUV light (L0). According to one embodiment, the light source (100) can emit 13.56 nm coherent EUV light generated in a higher harmonic manner. For example, the light source (100) can generate EUV light through plasma discharge. More specifically, the light source (100) can generate the EUV light (L0) using laser plasma, discharge plasma, or high-temperature plasma.

[0060] Meanwhile, for laser plasma, a femtosecond laser device may be used. More specifically, the femtosecond laser device may include, for example, a femtosecond titanium sapphire laser device. The femtosecond titanium sapphire laser device can generate pulsed laser light with a frequency of tens of megahertz and may be connected to a correlator. Laser light from the femtosecond laser device may be irradiated into a discharge chamber using a focusing lens. A gas for generating plasma, for example, neon gas, may be stored in the discharge chamber. By irradiating the neon gas stored in the discharge chamber with laser light, plasma is generated, and light of various wavelengths, including EUV light, may be emitted from the plasma.

[0061] According to another embodiment, the light source (100) may generate and emit light other than EUV light. That is, the light used in the EUV mask inspection device according to an embodiment of the present invention may include not only EUV light but also other light (odd-order harmonics of the wavelength of a femtosecond laser).

[0062] The filter (200) can receive light emitted from the light source (100) and filter it. According to one embodiment, the filter (200) can remove light other than the EUV wavelength range and transmit only light having the EUV wavelength range. That is, the filter (200) can selectively pass only EUV light among the light emitted from the light source (100) and remove other light. More specifically, the light emitted from the light source (100) may include light of various wavelengths such as EUV light and vacuum ultraviolet (VUV) light. Accordingly, the filter (200) can block light other than EUV light among the light emitted from the EUV light source (100), thereby allowing only EUV light to be irradiated onto the EUV mask (M) described later. Such a filter (200) can function to improve the spectral coherence of light. For example, the filter (200) may include a zirconium filter. Meanwhile, the EUV light output through the filter (200) may be EUV light having a center wavelength of 13.5 nm.

[0063] The beam splitter (300) receives the EUV light (L0) filtered through the filter (200) and can separate it into a first EUV light (L1) and a second EUV light (L2). According to one embodiment, as shown in FIG. 2, the beam splitter (300) transmits and reflects the EUV light (L0), wherein the EUV light (L0) transmitted through the beam splitter (300) is defined as the first EUV light (L1), and the EUV light (L0) reflected from the beam splitter (300) is defined as the second EUV light (L2).

[0064] The optical system (410, 420) can control the path of the first EUV light (L1) that has passed through the beam splitter (300) to irradiate the first EUV light (L1) onto an EUV mask (M). According to one embodiment, the EUV mask (M) is a reflective mask used in an EUV process and may include a multilayer reflective layer composed of Mo / Si pairs and an absorption pattern disposed on the multilayer reflective layer.

[0065] According to one embodiment, the optical system (410, 420) may include a first mirror (410) and a second mirror (420). For example, the first mirror (410) may include a concave multilayer thin film mirror for focusing the first EUV light (L1). Alternatively, the second mirror (420) may include a planar multilayer thin film mirror for guiding the first EUV light (L1) focused from the first mirror (410) to be irradiated onto the EUV mask (M).

[0066] According to one embodiment, the first EUV light (L1) irradiated onto the EUV mask (M) may be irradiated such that the direction in which the first EUV light (L1) is irradiated forms an angle of 6° with the normal direction of the upper surface of the EUV mask (M). That is, the first EUV light (L1) may be irradiated onto the EUV mask (M) to satisfy the condition of oblique incidence of 6°.

[0067] The first EUV light (L1) irradiated onto the EUV mask (M) may be reflected and diffracted by the EUV mask (M). The first EUV light (L1) reflected and diffracted from the EUV mask (M) may be defined as diffracted light (DL).

[0068] The mask stage (500) supports the EUV mask (M), and the EUV mask (M) can be placed on the mask stage (500). According to one embodiment, the mask stage (500) can move the position of the EUV mask (M). More specifically, the mask stage (500) can move the position of the EUV mask (M) to control the first EUV light (L1) to be irradiated on different regions of the EUV mask (M).

[0069] The first detector (610) can collect the diffracted light (DL) to obtain a diffraction pattern for the EUV mask (M). Alternatively, the second detector (620) can collect the second EUV light (L2) to detect the intensity value of the second EUV light (L2). That is, the first detector (610) can collect the light diffracted by the mask (M) from the first EUV light (L1) that has passed through the beam splitter (300) to obtain the intensity value of the diffraction pattern, and the second detector (620) can collect the second EUV light (L2) reflected from the beam splitter (300) to detect the intensity value of the second EUV light (L2).

[0070] The image acquisition unit (not shown) can acquire an image of the EUV mask using the intensity value of the diffraction pattern acquired through the first detector (610). According to one embodiment, the image acquisition unit can acquire an image of the EUV mask by using the intensity value of the diffraction pattern as an input value for a phase restoration algorithm, and an inspection of the EUV mask can be performed through the image of the EUV mask.

[0071] The present invention can obtain an image of the EUV mask by collecting diffracted light from different regions of the EUV mask, obtaining intensity values ​​of diffraction patterns for each region, and using the obtained intensity values ​​of the patterns as input values ​​for a phase restoration algorithm, in order to improve the resolution of the image of the EUV mask. That is, a high-resolution image can be obtained by dividing the EUV mask into a plurality of regions, irradiating each divided region with the first EUV light (L1), and thereby obtaining intensity values ​​of diffraction patterns for each divided region.

[0072] However, as described above, when the first EUV light (L1) is irradiated on each of the different regions of the EUV mask, photon-flux fluctuation occurs in each region due to the sensitivity of the first EUV light (L1), and when an image of the EUV mask is obtained using the intensity values ​​of the diffraction patterns obtained from each region where photon-flux fluctuation occurred, a problem of reduced resolution may occur.

[0073] Accordingly, the present invention can obtain a high-resolution image of the EUV mask by using the intensity value of the second EUV light (L2) detected through the second detector (620) to correct the intensity values ​​of the diffraction pattern, and then using the corrected intensity values ​​of the diffraction pattern as input values ​​for a phase restoration algorithm. Since the intensity value of the second EUV light (L2) contains relative intensity information regarding the photon flux of different regions of the EUV mask, a high-resolution image can be obtained by performing correction using the intensity value of the second EUV light (L2).

[0074] More specifically, when acquiring diffraction patterns from each of the different regions of the EUV mask, photon-flux fluctuation may occur due to the characteristics of the light source (sensitivity of EUV light). Furthermore, since the intensity value of the diffraction pattern detected by the first detector (610) varies depending on the position of the EUV mask, it may be difficult to determine whether the change is due to the position of the EUV mask or due to photon-flux fluctuation based solely on the intensity information of the acquired diffraction pattern. Therefore, if the photon-flux fluctuation occurring during the process of acquiring the intensity value of the diffraction pattern is not compensated for, the image may be restored using diffraction patterns having different intensity information for each of the different regions of the EUV mask, resulting in a restoration that differs from the original EUV mask image. In this case, this may cause problems with accuracy and measurement reliability in terms of image and defect inspection of masks for short-wavelength EUV exposure processes.

[0075] Accordingly, the present invention can correct the intensity values ​​of the diffraction pattern using the intensity value of the second EUV light (L2) which includes relative intensity information regarding the photon flux of different regions of the EUV mask as described above, and then restore the image of the EUV mask using the corrected intensity values ​​of the diffraction pattern.

[0076] That is, as shown in FIG. 3(a), the mask image obtained using uncorrected diffraction pattern intensity values ​​has low resolution, but as shown in FIG. 3(b), the resolution of the mask image can be improved by using corrected diffraction pattern intensity values.

[0077] As a result, since a high-resolution image can be obtained, the inspection accuracy and reliability of the EUV mask (M) can be further improved. According to one embodiment, the intensity value of the corrected diffraction pattern can be calculated according to the following <Equation 1>.

[0078] <Mathematical Formula 1>

[0079]

[0080] (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region)

[0081] Hereinafter, with reference to FIGS. 4 to 9, the EUV mask (M) is in regions 1 to 49 (A1 to A 49 For cases where the area is divided into ), the process of acquiring an image of the EUV mask (M) is described by way of example. The division of the area of ​​the EUV mask (M) into 49 areas is merely an example, and the number of divisions of the area of ​​the EUV mask (M) is not limited.

[0082] As described above, the EUV mask (M) is the first to fourth 9 regions (A1~A 49 In the case of including ), the above 1st to 49th regions (A1~A 49 For each of the above, the first EUV light (L1) can be irradiated, and the first to 49 regions (A1~A) can be irradiated through the first detector (610). 49Diffracted light can be collected for each of the above 1 to 49 regions (A1~A 49 Intensity values ​​of the diffraction pattern can be obtained for each of the following. Additionally, the second detector (620) [determines] the first to 49 regions (A1 to A 49 The intensity value of the second EUV light (L2) can be detected whenever the diffracted light is collected from each of the regions.

[0083] For example, when the first EUV light (L1) is irradiated onto the first region (A1), the intensity value (DP1) of the first diffraction pattern is obtained through the first detector (610), and the first intensity value (IT1) can be detected through the second detector (620). This process is performed in the second region to the 49th region (A2~A 49 It can also be performed on ), and as a result of the performance, the intensity values ​​of the 2nd to 49th diffraction patterns (DP2~DP 49 ) and 2nd to 49th century values ​​(IT2~IT 49 ) can be detected.

[0084] According to one embodiment, the first to 49 regions (A1~A 49 The first EUV light (L1) is irradiated onto each of the above regions, and as shown in FIG. 6, the first to 49 regions (A1~A 49 The first EUV light (L1) irradiated in adjacent regions among the ) may overlap at least partially. Accordingly, the resolution of the image described below may be further improved. Alternatively, the first to 49 regions (A1~A 49 If the first EUV light (L1) irradiated in adjacent areas among the ) does not overlap, a problem may occur in which the resolution of the image described later is reduced.

[0085] The above-mentioned first to fourth-ninth regions (A1~A 49 The intensity values ​​of the first to 49th diffraction patterns (DP1~DP) obtained from )49 Each of the ) can be corrected through the above <Mathematical Formula 1>.

[0086] <Mathematical Formula 1>

[0087]

[0088] (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region)

[0089] More specifically, the intensity value (DP1) of the first diffraction pattern obtained from the first region (A1) is corrected by multiplying it by A / B to obtain the intensity value (DP1) of the first diffraction pattern (DP1). 1a ) is calculated, wherein the above 1st to 49th century values ​​(IT1~IT 49 The maximum value among ) or the above 1st to 49th intensity values ​​(IT1~IT 49 The average value of ) is applied as A, and when the intensity value (DP1) of the first diffraction pattern is obtained from the first region (A1), the first intensity value (IT1) detected through the second detector (620) can be applied as B. This process is applied to the intensity values ​​(DP2~DP) of the second to fourth diffraction patterns. 49 It can also be performed for each of the ) and the intensity values ​​(DP) of the corrected 2nd to 49th diffraction patterns as a result of the performance 2a ~DP 49a ) can be produced.

[0090] Finally, the intensity values ​​(DP) of the corrected 1st to 49th diffraction patterns above 1a~DP 49a By using the above as input data for the phase restoration algorithm, a high-resolution image of the EUV mask (M) can be obtained. As illustrated in FIG. 9, the computational processing process using the phase restoration algorithm may include the steps of: assigning arbitrary values ​​to the Probe function P(r) and the object function O(r) (S10); calculating the amplitude and phase in the Fourier domain through the Fourier transform (S20); replacing the calculated amplitude with the amplitude value of the measured diffraction pattern (S30); applying an update function to the P(r) and O(r) obtained through the Inverse Fourier transform to reduce the error between the calculated value and the measured value (S40); and repeating steps S10 through S40 until the error between the measured value and the calculated value becomes less than or equal to a reference value (S50). According to one embodiment, P(r) can be defined as the first EUV light (L1) irradiated onto the EUV mask (M), and O(r) can be defined as an image of the EUV mask (M).

[0091] Consequently, that is, the EUV mask inspection accuracy enhancement device according to the embodiment of the present invention can compensate for photon-flux fluctuations caused by EUV light through a simple configuration using a beam splitter (300), so that high resolution, high accuracy, and high reliability mask imaging inspection can be performed.

[0092]

[0093] The above describes an EUV mask inspection accuracy enhancement device according to an embodiment of the present invention. The following describes a method for enhancing EUV mask inspection accuracy according to an embodiment of the present invention. According to one embodiment, the method for enhancing EUV mask inspection accuracy according to the embodiment may be performed through an EUV mask inspection accuracy enhancement device different from the embodiment described with reference to FIGS. 1 to 9.

[0094] FIG. 10 is a flowchart illustrating a method for improving the accuracy of EUV mask inspection according to an embodiment of the present invention.

[0095] Referring to FIG. 10, EUV light (L0) can be generated (S110). According to one embodiment, coherent EUV light of 13.56 nm can be generated in a higher harmonic manner through a light source (100), and the light source (100) can emit the generated EUV light (L0).

[0096] The above EUV light (L0) can be separated into a first EUV light (L1) and a second EUV light (L2) through a beam splitter (300) (S120). According to one embodiment, the beam splitter (300) transmits and reflects the EUV light (L0), wherein the EUV light (L0) transmitted through the beam splitter (300) is defined as the first EUV light (L1), and the EUV light (L0) reflected from the beam splitter (300) is defined as the second EUV light (L2).

[0097] The first EUV light (L1) can be irradiated onto an EUV mask (M) via an optical system (410, 420) (S130). According to one embodiment, the first EUV light (L1) irradiated onto the EUV mask (M) can be irradiated such that the direction in which the first EUV light (L1) is irradiated forms an angle of 6° with the normal direction of the upper surface of the EUV mask (M). That is, the first EUV light (L1) can be irradiated onto the EUV mask (M) to satisfy the condition of oblique incidence of 6°.

[0098] According to one embodiment, the EUV mask (M) may be divided into different regions, and the first EUV light (L1) may be irradiated into each region. For example, the EUV mask (M) may have regions 1 to 49 (A1 to A 49 It can be divided into ), and the above 1st to 49th regions (A1~A 49 For each of the above, the first EUV light (L1) can be irradiated.

[0099] The first EUV light (L1) irradiated onto the EUV mask (M) can collect the diffracted light (DL) diffracted from the EUV mask (M) to obtain the intensity value of the diffraction pattern for the EUV mask (M) (S140). According to one embodiment, the first to 49 regions (A1~A 49 Diffracted light is collected from each of the above 1 to 49 regions (A1~A 49 For each ) intensity values ​​of the 1st to 49th diffraction patterns (DP1~DP 49 ) can be obtained.

[0100] The second EUV light (L2) can be collected and the intensity of the second EUV light (L2) can be detected (S150). According to one embodiment, the acquisition of the intensity value of the diffraction pattern and the detection of the intensity of the second EUV light (L2) can be performed together. That is, the first to 49 regions (A1~A 49The intensity value of the second EUV light (L2) can be detected whenever the first EUV light (L1) is irradiated onto each of the ) areas. According to one embodiment, the first to 49 regions (A1~A 49 For each of the above, the intensity values ​​of the 1st to 49th diffraction patterns (DP1~DP 49 While ) is being obtained, the 1st to 49th century values ​​(IT1~IT 49 ) can also be detected.

[0101] The intensity value of the diffraction pattern can be corrected using the intensity value of the second EUV light (L2) (S160). More specifically, the intensity values ​​of the diffraction pattern can be corrected through <Equation 1>.

[0102] <Mathematical Formula 1>

[0103]

[0104] (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region)

[0105] For example, the intensity value (DP1) of the first diffraction pattern obtained from the first region (A1) is corrected by multiplying it by A / B to obtain the intensity value (DP1) of the first diffraction pattern (DP1). 1a ) is calculated, wherein the above 1st to 49th century values ​​(IT1~IT 49 The maximum value among ) or the above 1st to 49th intensity values ​​(IT1~IT 49The average value of ) is applied as A, and when the intensity value (DP1) of the first diffraction pattern is obtained from the first region (A1), the first intensity value (IT1) detected through the second detector (620) can be applied as B. This process is applied to the intensity values ​​(DP2~DP) of the second to fourth diffraction patterns. 49 It can also be performed for each of the ) and the intensity values ​​(DP) of the corrected 2nd to 49th diffraction patterns as a result of the performance 2a ~DP 49a ) can be produced.

[0106] An image of the EUV mask (M) can be obtained using the corrected intensity values ​​of the diffraction patterns (S170). According to one embodiment, the intensity values ​​(DP) of the corrected first to forty-ninth diffraction patterns 1a ~DP 49a By using the ) as input data for the phase restoration algorithm, a high-resolution image of the EUV mask (M) can be obtained.

[0107] According to one embodiment, the computational processing using a phase restoration algorithm may include the steps of: assigning arbitrary values ​​to Probe function P(r) and object function O(r) (S10); calculating amplitude and phase in the Fourier domain through Fourier transform (S20); replacing the calculated amplitude with the amplitude value of the measured diffraction pattern (S30); applying an update function to P(r) and O(r) obtained through Inverse Fourier transform to reduce the error between the calculated value and the measured value (S40); and repeating steps S10 through S40 until the error between the measured value and the calculated value becomes less than or equal to a reference value (S50). According to one embodiment, P(r) may be defined as the first EUV light (L1) irradiated onto the EUV mask (M), and O(r) may be defined as an image of the EUV mask (M).

[0108]

[0109] Although the present invention has been described in detail using preferred embodiments, the scope of the invention is not limited to specific embodiments and should be interpreted by the appended claims. Furthermore, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the invention.

[0110] The present invention can be used in the semiconductor industry.

Claims

1. A light source that generates EUV light; A beam splitter that separates the EUV light generated from the above light source into a first EUV light and a second EUV light; An optical system that controls the path of the first EUV light separated from the beam splitter and irradiates the first EUV light onto an EUV mask; A first detector that collects diffracted light diffracted from the EUV mask by the first EUV light irradiated onto the EUV mask and obtains a diffraction pattern for the EUV mask; A second detector that collects the second EUV light separated from the beam splitter and detects the intensity value of the second EUV light; and An EUV mask inspection accuracy improvement device comprising an image acquisition unit that corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected through the second detector, and acquires an image of the EUV mask using the corrected intensity value of the diffraction pattern.

2. In Paragraph 1, The first detector collects diffracted light from different regions of the EUV mask, respectively, and obtains diffraction patterns for each region, and The above image acquisition unit comprises correcting each intensity value of the acquired diffraction pattern and then using each corrected diffraction pattern as an input value for a phase restoration algorithm to acquire an image of the EUV mask.

3. In Paragraph 2, The second detector detects the intensity value of the second EUV light whenever the diffracted light is collected from different regions of the EUV mask, respectively, and EUV mask inspection accuracy enhancement device comprising the above corrected diffraction pattern intensity value calculated according to <Mathematical Formula 1> below. <Mathematical Formula 1> (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region) 4. In Paragraph 2, The first EUV light is irradiated onto each of the different regions of the above EUV mask, EUV mask inspection accuracy enhancement device comprising at least a portion of the first EUV lights irradiated on adjacent regions among different regions of the EUV mask.

5. In Paragraph 1, The beam splitter transmits and reflects the EUV light generated from the light source, EUV mask inspection accuracy enhancement device comprising: the EUV light transmitted through the beam splitter is defined as the first EUV light, and the EUV light reflected from the beam splitter is defined as the second EUV light.

6. In Paragraph 1, The mask stage on which the above-mentioned EUV mask is placed is further included, The above mask stage controls the position of the EUV mask so that the first EUV light is irradiated onto different regions of the EUV mask.

7. In Paragraph 1, An EUV mask inspection accuracy enhancement device comprising irradiating the EUV mask with the first EUV light such that it forms an angle of 6° with the normal direction of the upper surface of the EUV mask.

8. A beam splitter that transmits part of the EUV light and reflects the rest; A first detector that collects diffracted light from an EUV mask, which is diffracted from the first EUV light transmitted through the beam splitter, and obtains a diffraction pattern for the EUV mask; A second detector that collects the second EUV light reflected from the beam splitter and detects the intensity value of the second EUV light; and An EUV mask inspection accuracy improvement device comprising an image acquisition unit that corrects the intensity value of the diffraction pattern using the intensity value of the second EUV light detected through the second detector, and acquires an image of the EUV mask using the corrected intensity value of the diffraction pattern.

9. In Paragraph 8, The first detector collects diffracted light from different regions of the EUV mask, respectively, and obtains intensity values ​​of the diffraction pattern for each region, and The second detector detects the intensity value of the second EUV light whenever the diffracted light is collected from different regions of the EUV mask, respectively, and The above image acquisition unit comprises acquiring an image of the EUV mask by correcting each of the intensity values ​​of the acquired diffraction pattern according to the following <Mathematical Formula 1> and then using each of the corrected intensity values ​​of the diffraction pattern as input values ​​for a phase restoration algorithm. <Mathematical Formula 1> (DP: Intensity value of the diffraction pattern obtained from the target region among the different regions of the above EUV mask, DP a : The intensity value of the diffraction pattern corrected from the intensity value of the diffraction pattern obtained from the target region, A: the maximum value among a plurality of intensity values ​​of the second EUV light obtained from the second detector or the average value of a plurality of intensity values ​​of the second EUV light obtained from the second detector, B: the intensity value of the second EUV light detected through the second detector when the intensity value of the diffraction pattern is obtained from the target region) 10. Step of generating EUV light; A step of separating the above EUV light into a first EUV light and a second EUV light; A step of irradiating the above-mentioned first EUV light onto an EUV mask; A step of collecting diffracted light diffracted from the EUV mask by the first EUV light irradiated onto the EUV mask to obtain a diffraction pattern for the EUV mask; A step of collecting the second EUV light and detecting the intensity value of the second EUV light; A step of correcting the intensity value of the diffraction pattern using the intensity value of the second EUV light; and A method for improving the accuracy of EUV mask inspection, comprising the step of acquiring an image of the EUV mask using the corrected diffraction pattern.

11. In Paragraph 10, The step of irradiating the first EUV light onto an EUV mask includes irradiating the first EUV light onto each of the different regions of the EUV mask, and A method for improving the accuracy of EUV mask inspection, comprising the step of acquiring a diffraction pattern for the EUV mask, collecting diffracted light from each of the different regions of the EUV mask and acquiring a diffraction pattern for each region.

12. In Paragraph 11, A method for improving EUV mask inspection accuracy, comprising the step of collecting the second EUV light and detecting the intensity value of the second EUV light, wherein the intensity value of the second EUV light is detected whenever the first EUV light is irradiated onto each of the different regions of the EUV mask.

13. In Paragraph 12, A method for improving the accuracy of EUV mask inspection, comprising the step of correcting the intensity value of the diffraction pattern using the intensity value of the second EUV light, and correcting the intensity values ​​of the multiple diffraction patterns obtained from different regions of the EUV mask using the multiple intensity values ​​of the second EUV light detected for different regions of the EUV mask.

14. In Paragraph 13, A method for improving the accuracy of EUV mask inspection, comprising the step of acquiring an image of the EUV mask using a plurality of corrected intensity values ​​of the diffraction patterns as input values ​​for a phase restoration algorithm.

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