Phase shift mask for extreme ultraviolet lithography and method of manufacturing a semiconductor device therewith

Abstract

A phase shift mask for extreme ultraviolet lithography, comprising: a substrate; a reflective layer on the substrate; a capping layer on the reflective layer; a buffer pattern on the capping layer, the buffer pattern comprising openings exposing a surface of the capping layer; and an absorber pattern on the buffer pattern, the absorber pattern comprising a refractive index less than a refractive index of the buffer pattern and a thickness greater than a thickness of the buffer pattern. The buffer pattern comprises a material having etch selectivity relative to the absorber pattern and the capping layer.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Korean Patent Application No. 10-2020-0073145, filed on June 16, 2020, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments of the present invention relate to a phase-shifting mask for extreme ultraviolet lithography (EUV) and a method for manufacturing semiconductor devices using the same. Background Technology

[0004] As semiconductor devices shrink in size and design rules decrease, there is an increasing need for technologies to form smaller patterns. To meet these requirements, the wavelengths of light sources used in photolithography processes have been shortened. For example, light sources used in photolithography processes have been developed in the order of g-line (436 nm), i-line (365 nm), KrF laser (248 nm), and ArF laser (193 nm). Recently, extreme ultraviolet (EUV) lithography processes have been proposed that utilize extreme ultraviolet light with a full width at half maximum (FWHM) wavelength of 13.5 nm as the light source.

[0005] However, most refractive optical materials commonly used in other lithography processes can absorb extreme ultraviolet light. Therefore, EUV lithography can typically use reflective optical systems instead of refractive optical systems. Summary of the Invention

[0006] Some exemplary embodiments of the present invention can provide a phase-shifting mask for extreme ultraviolet lithography that enables high-resolution images.

[0007] Some exemplary embodiments of the present invention may also provide a method for manufacturing a semiconductor device that can improve productivity.

[0008] In one aspect, a phase-shifting mask for extreme ultraviolet lithography may include: a substrate; a reflective layer on the substrate; a capping layer on the reflective layer; a buffer pattern on the capping layer, the buffer pattern including openings exposing surfaces of the capping layer; and an absorber pattern on the buffer pattern, the absorber pattern including a refractive index less than that of the buffer pattern and a thickness greater than that of the buffer pattern. The buffer pattern may include a material having etch selectivity relative to the absorber pattern and the capping layer.

[0009] In an aspect, a phase shift mask for extreme ultraviolet lithography can include a substrate on a conductive layer; a reflective layer on the substrate; a capping layer on the reflective layer; and an absorber pattern on the capping layer, the absorber pattern including openings exposing a surface of the capping layer. The absorber pattern can include nitrogen and chromium. A content of nitrogen in the absorber pattern can range from 5 at% to 70 at%.

[0010] In an aspect, a phase shift mask for extreme ultraviolet lithography can include a substrate; a reflective layer on the substrate; a capping layer on the reflective layer; a buffer pattern on the capping layer, the buffer pattern including openings exposing a surface of the capping layer; and an absorber pattern on the buffer pattern, the absorber pattern including nitrogen and chromium. The buffer pattern can include a material having etch selectivity with respect to the absorber pattern. A content of nitrogen in the absorber pattern can vary discontinuously or gradually according to a distance from the buffer pattern.

[0011] In an aspect, a method of manufacturing a semiconductor device can include sequentially stacking an etch target layer and a photoresist layer on a wafer; and performing an exposure process on the photoresist layer with a phase shift mask for extreme ultraviolet lithography. The phase shift mask for extreme ultraviolet lithography can include a substrate; a reflective layer on the substrate; a capping layer on the reflective layer; a buffer pattern on the capping layer, the buffer pattern including openings exposing a surface of the capping layer; and an absorber pattern on the buffer pattern, the absorber pattern including a refractive index less than a refractive index of the buffer pattern and a thickness greater than a thickness of the buffer pattern. The buffer pattern can include a material having etch selectivity with respect to the absorber pattern and the capping layer. BRIEF DESCRIPTION OF DRAWINGS

[0012] The inventive concept will become more apparent from the detailed description in conjunction with the accompanying drawings.

[0013] Figure 1 FIG. 1 is a conceptual diagram illustrating an extreme ultraviolet (EUV) lithography apparatus using a phase shift mask according to some example embodiments of the inventive concept.

[0014] Figure 2 FIG. 2 is a plan view schematically illustrating a phase shift mask according to some example embodiments of the inventive concept.

[0015] Figure 3 FIG. 3 is a cross-sectional view schematically illustrating a phase shift mask according to some example embodiments of the inventive concept.

[0016] Figures 4A-4C FIG. 4 illustrates a detailed structure of an absorber pattern according to some example embodiments of the inventive concept.

[0017] Figure 5 FIG. 5 is a cross-sectional view illustrating a portion of a phase shift mask according to some example embodiments of the inventive concept.

[0018] Figure 6A is a plot showing normalized image log-slope (NILS) values of the thickness of an absorber pattern according to a phase shift mask according to some example embodiments of the inventive concept.

[0019] Figure 6B is a plot showing transmittance and phase difference of the thickness of an absorber pattern according to a phase shift mask according to some example embodiments of the inventive concept.

[0020] Figure 6C is a plot showing NILS values of a dose according to a phase shift mask according to example embodiments and comparative examples of the inventive concept.

[0021] Figures 7A-7C is a cross-sectional view showing a process of manufacturing a phase shift mask according to some example embodiments of the inventive concept. Figure 3

[0022] Figure 8 is a cross-sectional view of a phase shift mask according to some example embodiments of the inventive concept.

[0023] Figure 9 is a cross-sectional view showing a process of manufacturing a phase shift mask according to some example embodiments of the inventive concept. Figure 8 DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the inventive concept will be described in detail with reference to the accompanying drawings.

[0025] When the term "about" or "substantially" is used in this specification in connection with a numerical value, it means that the associated numerical value includes manufacturing tolerances (e.g., ±10%) around the listed numerical value. Also, when the words "generally" and "substantially" are used in connection with a geometry, it means that precision of the geometry is not required, but latitude of the shape is within the scope of the disclosure. Further, whether a numerical value or a shape is modified by "about" or "substantially," it should be understood that these values and shapes should be understood to include manufacturing tolerances or operating tolerances (e.g., ±10%) around the listed numerical value or shape.

[0026] Although the terms "first," "second," "third," etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the scope of the present disclosure.

[0027] ​​For convenience in description, spatially relative terms such as "upper," "lower," "top," "bottom," and the like can be used for the purpose of clarity in understanding the apparatus described in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. The apparatus can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly. Also, when an element is referred to as being "between" two elements, it can be the only element between the two elements, or one or more other elements can be between the two elements.

[0028] Figure 1 is a conceptual diagram showing an extreme ultraviolet (EUV) lithography apparatus using a phase shift mask according to some example embodiments of inventive concepts.

[0029] Referring to Figure 1 The EUV lithography apparatus 1000 can include a light source unit 10, a condenser unit 20, a projection unit 40, and a controller 90.

[0030] The light source unit 10 can be configured to generate extreme ultraviolet light 11 (EUV light; e.g., light having a full width at half maximum (FWHM) wavelength of about 13.5 nm). The condenser unit 20 can be configured to direct the EUV light 11 generated from the light source unit 10 so that the EUV light 11 is radiated to the phase shift mask 500. The condenser unit 20 can include condenser optics 22 (e.g., lenses and / or mirrors). The condenser optics 22 can be configured to converge and / or reflect the EUV light 11 to direct the EUV light 11 to the phase shift mask 500. The EUV light 11 can be obliquely incident to the phase shift mask 500 by the condenser unit 20.

[0031] The phase shift mask 500 can be arranged on a mask stage 32, which can be configured to move the phase shift mask 500. For example, the mask stage can be configured to move in a first axis and / or a second axis parallel to the incident surface of the EUV light 11 (e.g. front-to-back and / or left-to-right), in a third axis perpendicular to the incident surface of the EUV light 11 (e.g. up-to-down), and / or to tilt the phase shift mask 500 about the first axis, the second axis and / or the third axis (e.g. roll, pitch and / or yaw). The light source unit 10 and the mask stage 32 can be controlled by a controller 90. The controller 90 can be an electronic controller configured to control the operation of the EUV lithography apparatus 1000, and, for example, it can comprise processing circuitry, such as hardware (including logic circuitry), hardware / software combinations, such as a processor executing software, or combinations thereof. For example, the processing circuitry can more specifically include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) and programmable logic unit, a microprocessor, an application-specific integrated circuit (ASIC), etc.

[0032] The phase shift mask 500 can be configured to reflect the EUV light 11 and to include a mask pattern image in the reflected EUV light. The phase shift mask 500 can be incident to the projection unit 40. The projection unit 40 can be configured to project the mask pattern image of the phase shift mask 500 onto the wafer 50. The projection unit 40 can include projection optics 42 (e.g., lenses and / or mirrors). The projection optics 42 can be configured to reduce the mask pattern image of the phase shift mask 500 by using the EUV light 11 reflected from the phase shift mask 500 with a predetermined (and / or, alternatively, desired) magnification (e.g., 1 / 4, 1 / 6, or 1 / 8) and to project the reduced mask pattern image onto the wafer 50. The etching target layer 1 and the photoresist layer 2 can be sequentially stacked on the wafer 50. The EUV light 11 can pass through the projection unit 40 and then can be radiated onto the wafer 50, and thus a pattern corresponding to the mask pattern image of the phase shift mask 500 can be transferred to the photoresist layer 2. After this exposure process, a development process can be performed to form a photoresist pattern. The etching target layer 1 can be etched using the photoresist pattern. The wafer 50 can be loaded on a wafer stage 52, and the wafer stage 52 can be configured to move the wafer 50 to change an exposure area in the wafer 50. For example, the wafer stage 52 can be configured to move in a first axis and / or a second axis (e.g., front and back and / or left and right) parallel to an incident surface of the EUV light 11 projected onto the wafer, to move in a third axis (e.g., up and down) perpendicular to the incident surface of the EUV light 11 projected onto the wafer, and / or to tilt (e.g., roll, pitch, and / or yaw) the wafer stage 52 about the first axis, the second axis, and / or the third axis. The loading, unloading, and movement of the wafer stage 52 can be controlled (e.g., independently controlled and / or controlled by the controller 90). The exposure process using the phase shift mask 500 can be performed in a vacuum state.

[0033] Figure 2 is a plan view schematically illustrating a phase shift mask according to some example embodiments of the inventive concepts. Figure 3 is a cross-sectional view schematically illustrating a phase shift mask according to some example embodiments of the inventive concepts.

[0034] Referring to Figure 2 and Figure 3 , the phase shift mask 500 can include a substrate 100, a reflective layer 120, a capping layer 130, a buffer pattern 140, an absorber pattern 150, and a lower conductive layer 110. The phase shift mask 500 can be a reflective attenuated phase shift mask.

[0035] The substrate 100 can include a material having a low coefficient of thermal expansion. For example, the substrate 100 can include glass and / or silicon (Si). The substrate 100 can include a pattern area PA on which a pattern (e.g., a mask pattern image) to be transferred and / or projected onto a wafer is disposed, and a border area BA around the pattern area PA. The border area BA can be configured to prevent and / or reduce reflection of EUV light from the border area BA, and can be referred to as a black border area, for example, due to the lack of reflected light. The pattern area PA can include a main pattern area 102 and a sub-pattern area 104. The main pattern area 102 can be an area configured to transfer and / or project a main pattern for forming an integrated circuit onto a chip area of the wafer 50 (see Figure 1 ). The sub-pattern area 104 can be an area configured to transfer and / or project a sub-pattern onto a scribe line area of the wafer 50 (see Figure 1 ). The border area BA can surround the pattern area PA when viewed in a plan view. Even though not shown in the drawings, an alignment mark for aligning the phase shift mask 500 in the lithography apparatus 1000 and / or an identification mark for identifying the phase shift mask 500 can be disposed on the border area BA. Figure 1

[0036] The reflective layer 120 can be located on the first surface 100a of the substrate 100. The reflective layer 120 can be located on the pattern area PA and can extend onto the border area BA. The reflective layer 120 can be configured to reflect light (e.g., the EUV light 11 of Figure 1 ). The reflective layer 120 can include a Bragg reflector. For example, the reflective layer 120 can include a multilayer structure in which low refractive index layers 122 and high refractive index layers 124 are alternately and repeatedly stacked. For example, the low refractive index layers 122 and the high refractive index layers 124 can be alternately stacked about 40 times to about 60 times. The low refractive index layers 122 can include, for example, molybdenum (Mo), and the high refractive index layers 124 can include, for example, silicon (Si). In some embodiments, the lowermost low refractive index layer 122 can correspond to the lowermost layer of the reflective layer 120, and the uppermost high refractive index layer 124 can correspond to the uppermost layer of the reflective layer 120.

[0037] ​According to some embodiments, the reflective layer 120 can include a first portion S1 and a second portion S2. The first portion S1 can include a multilayer structure in which the low refractive index layers 122 and the high refractive index layers 124 are alternately stacked on the pattern area PA, and the second portion S2 can include a structure in which the low refractive index layers 122 and the high refractive index layers 124 are intermingled with each other on the boundary area BA. For example, the boundary and / or interface between the alternately stacked low refractive index layers 122 and the high refractive index layers 124 can be indistinct and / or non-uniform in the second portion S2 of the reflective layer 120 on the boundary area BA; and a composite including a gradient of materials having the low refractive index layers 122 and the high refractive index layers 124 can be formed at the interface. For example, in an example embodiment in which the low refractive index layers 122 and the high refractive index layers 124 include Mo and Si, respectively, a silicide such as MoSi2 can be included and / or intermingled between the layers. Reflection of light (e.g., EUV light 11) incident to the second portion S2 of the reflective layer 120 can be reduced by the intermingled structure, and thus the second portion S2 can function as a black boundary area. Figure 1

[0038] The lower conductive layer 110 can be located on a second surface 100b of the substrate 100, the second surface 100b being opposite to the first surface 100a of the substrate 100. The lower conductive layer 110 can be spaced apart from the reflective layer 120 with the substrate 100 interposed between the lower conductive layer 110 and the reflective layer 120. The lower conductive layer 110 can include a conductive material (e.g., CrN). The lower conductive layer 110 can be configured to be used in operation of an electrostatic chuck, and can be used, for example, to load a phase shift mask (e.g., phase shift mask 500) for EUV lithography on a mask stage (e.g., mask stage 32). Figure 1 Figure 1

[0039] The capping layer 130 can be located on the reflective layer 120. For example, the reflective layer 120 can be interposed between the capping layer 130 and the substrate 100. The capping layer 130 can be located on the pattern area PA, and can extend onto the boundary area BA. The capping layer 130 can be configured to protect the reflective layer 120, and to prevent the surface of the reflective layer 120 from being oxidized. The capping layer 130 can include a metal (e.g., ruthenium (Ru)).

[0040] The absorber pattern 150 can be located on the capping layer 130. For example, the capping layer 130 can be interposed between the reflective layer 120 and the absorber pattern 150. The absorber pattern 150 can be located on the pattern area PA and the boundary area BA, and an opening 150P included in the absorber pattern 150 can expose a top surface of the capping layer 130.

[0041] ​​​The buffer pattern 140 can be interposed between the capping layer 130 and the absorber pattern 150. Each of the buffer patterns 140 can be interposed between the capping layer 130 and each of the absorber patterns 150. The openings 150P can extend between structures included in the buffer pattern 140 to expose the top surface of the capping layer 130.

[0042] The buffer pattern 140 can include a material different from materials included in the capping layer 130 and / or the absorber pattern 150. For example, the buffer pattern 140 can include a material having etch selectivity with respect to the capping layer 130 and the absorber pattern 150. The buffer pattern 140 can be referred to as an etch stop pattern. The buffer pattern 140 can include a silicon-containing material, a metal-containing material, a metal nitride, and / or a metal oxide. For example, the buffer pattern 140 can include at least one of silicon (Si), silicon nitride (SiN), silicon oxide (SiO2), silicon oxynitride (SiON), tantalum borate (TaBO), tantalum oxide (TaO), tantalum oxynitride (TaON), tantalum nitride (TaN), tantalum boron nitride (TaBN), titanium nitride (TiN), niobium (Nb), and tantalum (Ta).

[0043] The top surface of the absorber pattern 150 can be exposed. For example, the absorber pattern 150 can be an upper layer of the phase shift mask 500 and be exposed without being covered by anything. The absorber pattern 150 can be referred to as a phase shift pattern. The absorber pattern 150 can include nitrogen (atoms) and chromium (atoms). The absorber pattern 150 can further include oxygen (atoms). For example, the absorber pattern 150 can include at least one of chromium nitride (CrN) and chromium oxynitride (CrON). The refractive index and extinction coefficient of the absorber pattern 150 can vary depending on the nitrogen content, density, and / or deposition conditions of the absorber pattern 150. For example, the content of nitrogen (atoms) in the absorber pattern 150 can range from 5 at% to 70 at%. The refractive index of the absorber pattern 150 with respect to EUV light can range from 0.925 to 0.935, for example, and the extinction coefficient of the absorber pattern 150 with respect to EUV light can range from 0.03 to 0.04.

[0044] The nitrogen content in the absorber pattern 150 can vary stepwise, discontinuously, gradually, and / or continuously depending on the distance from the top surface of the capping layer 130. For example, the absorber pattern 150 can have a single layer structure in which the constituent components of nitrogen and chromium are uniform throughout, and / or the absorber pattern 150 can have a multi-layer structure including two or more layers having different constituent components of nitrogen and chromium. The multi-layer structure will be described below with reference to Figure 4A and Figure 4B The multi-layer structure.

[0045] Figures 4A-4CDetailed structures of absorber patterns according to some example embodiments of the inventive concepts are shown.

[0046] Referring to Figure 4A , the absorber pattern 150 can include a first absorber portion 150a and a second absorber portion 150b on the first absorber portion 150a. The first absorber portion 150a and the second absorber portion 150b can each include nitrogen and chromium. The nitrogen content of the first absorber portion 150a can be different from the nitrogen content of the second absorber portion 150b. For example, the nitrogen content of the first absorber portion 150a can be greater than the nitrogen content of the second absorber portion 150b. Although shown as a clear portion, the interface between the first absorber portion 150a and the second absorber portion 150b can be visible, invisible, and / or blurred, for example, due to some migration of the nitrogen and / or chromium content at the interface.

[0047] Referring to Figure 4B , the absorber pattern 150 can further include a third absorber portion 150c on the second absorber portion 150b. The first to third absorber portions 150a, 150b, and 150c can include nitrogen and chromium. The nitrogen content of the first absorber portion 150a can be greater than the nitrogen content of the third absorber portion 150c and can be less than the nitrogen content of the second absorber portion 150b. The boundary portion between the first to third absorber portions 150a, 150b, and 150c can be visible, invisible, and / or blurred. In Figure 4A and Figure 4B , one of the first to third absorber portions 150a, 150b, and 150c can further include oxygen. The first to third absorber portions 150a, 150b, and 150c can be referred to as first to third sub-absorber layers, respectively. In other words, the absorber pattern 150 can include the first to third sub-absorber layers 150a, 150b, and 150c stacked sequentially, and the nitrogen content in the first to third sub-absorber layers 150a, 150b, and 150c can be different from each other.

[0048] Alternatively, for example Figure 4C , the nitrogen content in the absorber pattern 150 can gradually and continuously increase as the distance from the top surface of the cap layer 130 increases, and / or the nitrogen content in the absorber pattern 150 can gradually and continuously decrease as the distance from the top surface of the cap layer 130 increases.

[0049] Figure 5 is a cross-sectional view showing a portion of a phase shift mask according to some example embodiments of the inventive concepts.

[0050] Referring to Figure 5The capping layer 130 can have a first thickness T1 in a direction perpendicular to the first surface 100a of the substrate 100. The buffer pattern 140 can have a second thickness T2 in the direction perpendicular to the first surface 100a of the substrate 100. The absorber pattern 150 can have a third thickness T3 in the direction perpendicular to the first surface 100a of the substrate 100. The third thickness T3 can be greater than the first thickness T1 and the second thickness T2. The refractive index n2 of the absorber pattern 150 can be less than the refractive index n1 of vacuum. For example, in a refractive index scale normalized to the refractive index n1 of vacuum, the refractive index n2 can be less than 1. The refractive index n2 of the absorber pattern 150 can be less than the refractive index of the buffer pattern 140. The extinction coefficient of the absorber pattern 150 can be greater than the extinction coefficients of the capping layer 130 and the buffer pattern 140.

[0051] When the absorber pattern 150 is formed of chromium nitride and has a nitrogen content of, for example, about 10 at%, an experimental value (n) of the refractive index of the chromium nitride calculated by the Fresnel equation is determined to be about 0.927 and the extinction coefficient of the chromium nitride is determined to be about 0.039. When the buffer pattern 140 is formed of silicon, the refractive index of the buffer pattern 140 can be about 1. When the buffer pattern 140 is formed of TaBN, the refractive index of the buffer pattern 140 can be about 0.949.

[0052] Referring to Figure 5 The first EUV light IL1 and the second EUV light IL2 can be incident to the first surface 100a of the substrate 100. The first EUV light IL1 and the second EUV light IL2 can have, for example, a first wavelength λ1 (e.g., a first FWHM wavelength of about 13.5 nm). The first EUV light IL1 can pass through the opening 150P and then can be reflected from the surface of the reflective layer 120 to form the first reflected EUV light RL1. The second EUV light IL2 can pass through the absorber pattern 150 and then can be reflected from the surface of the reflective layer 120 to form the second reflected EUV light RL2. A portion of the second EUV light IL2 can be absorbed in the absorber pattern 150, and thus, the amplitude of the second reflected EUV light RL2 can be less than the amplitude of the second EUV light IL2.

[0053] The absorber pattern 150 can be configured to absorb a portion of the second EUV light IL2. Accordingly, a reflectivity of the second EUV light IL2 incident to the absorber pattern 150 can be less than a reflectivity of the first EUV light ILl incident to the opening 150P. The reflectivity of the second EUV light IL2 incident to the absorber pattern 150 can vary based on an extinction coefficient (k) of a material of the absorber pattern 150 and / or a thickness of the absorber pattern 150. For example, the reflectivity of the second EUV light IL2 incident to the absorber pattern 150 can increase as the extinction coefficient (k) of the material of the absorber pattern 150 decreases and / or as the thickness of the absorber pattern 150 decreases.

[0054] The absorber pattern 150 can be configured to shift a phase of the second reflected EUV light RL2. For example, a wavelength of light passing through a material can increase as a refractive index of the material decreases. As the refractive index of the absorber pattern 150 is less than the refractive index of a vacuum, the first wavelength λl of the second EUV light IL2 in a vacuum can increase to a second wavelength λ2 in the absorber pattern 150. As a result of the change in wavelength in the absorber pattern 150, the phase of the second reflected EUV light RL2 exiting the absorber pattern 150 can be different than the phase of the first reflected EUV light RLl. This phase difference can increase as the refractive index of the material of the absorber pattern 150 decreases and / or as the thickness of the absorber pattern 150 increases.

[0055] The first thickness Tl of the capping layer 130 and the second thickness T2 of the buffer pattern 140 can be less than the first wavelength λl. Accordingly, the capping layer 130 and the buffer pattern 140 can have a relatively weak influence on the phase shift of the second reflected EUV light RL2. The third thickness T3 of the absorber pattern 150 can be greater than the first wavelength λl. Accordingly, the absorber pattern 150 can dominantly influence the phase shift of the second reflected EUV light RL2.

[0056] In some example embodiments, each of the first thickness Tl and the second thickness T2 can be in a range of about 29% to about 75% of the first wavelength λl of the EUV light ILl or IL2. The third thickness T3 can be in a range of about 296% to about 408% of the first wavelength λl of the EUV light ILl or IL2. When the first wavelength λl of the EUV light ILl or IL2 is about 13.5 nm, for example, the first thickness Tl and the second thickness T2 can each independently be in a range from about 4 nm to about 10 nm, and the third thickness T3 can be in a range from about 40 nm to about 55 nm. As a result of the absorber pattern 150 having the third thickness T3, the second reflected EUV light RL2 can have a phase difference of about 170 degrees to about 235 degrees relative to the first reflected EUV light RLl.

[0057] Destructive interference can occur between the second reflected EUV light RL2 and the first reflected EUV light RL1 through a phase difference. When... Figure 1 When the photoresist layer 2 is exposed using the phase-shift mask 500, the intensity of EUV light radiated onto the region of the photoresist layer corresponding to the absorber pattern 150 can be reduced by the destructive interference between the reflected EUV light RL1 and RL2. For example, the image projected onto the photoresist layer can have a high normalized image logarithmic slope (NILS), thus high-resolution images can be easily achieved on the photoresist layer.

[0058] Figure 6A This is a graph showing the normalized image logarithmic slope (NILS) values ​​of the thickness of an absorber pattern based on a phase-shift mask according to some embodiments of the present invention.

[0059] Reference Figure 6A Samples were prepared in which a 4 nm thick layer including ruthenium was used as a capping layer 130, a 4 nm thick layer including TaBO was used as a buffer pattern 140, and a layer including chromium nitride (CrN) was used as an absorber pattern 150. Here, the nitrogen content was uniformly fixed at approximately 10 at% throughout the absorber pattern 150. In one sample, the absorber pattern 150 had a line-and-space (L / S) pattern shape with a spacing of 36 nm (1x) (e.g., the width of the line pattern was 18 nm, and the space between the line patterns was 18 nm). In another sample, the absorber pattern 150 had a contact hole structure pattern shape with the same spacing. NILS values ​​based on the thickness of the absorber pattern 150 in the samples were simulated, and the simulation results are shown below. Figure 6A In. Figure 6A In the study, when the thickness of the absorber pattern formed from chromium nitride (CrN) was approximately 48.5 nm, both the L / S pattern and the pore structure pattern exhibited the highest NILS values ​​(e.g., the NILS value of the L / S pattern was approximately 2.75). Additionally, when the absorber pattern thickness was approximately 42 nm, a very high NILS value was observed (e.g., the NILS value of the L / S pattern was approximately 2.70). Overall, when the thickness of the absorber pattern 150 was in the range of approximately 40 nm to approximately 55 nm, excellent NILS values ​​were observed (e.g., the NILS value of the L / S pattern was in the range of approximately 2.35 to approximately 2.75). Therefore, according to... Figure 6A Absorber patterns 150 formed of chromium nitride (CrN) with a thickness between approximately 40 nm and approximately 55 nm can exhibit excellent NILS values.

[0060] Figure 6BThis is a graph showing the transmittance and phase difference of an absorber pattern based on the thickness of a phase-shift mask according to some example embodiments of the present invention.

[0061] Reference Figure 6B The transmittance and phase difference of a phase-shift mask with a thickness based on an absorber pattern having an L / S pattern shape are related to... Figure 6A Simulations were performed under the same conditions, and the simulation results are shown below. Figure 6B In this context, transmittance can be the relative reflectance with respect to the reflective layer 120 (e.g., transmittance = R). ABS / R ML , where R ABS Indicates the reflectivity of absorber pattern 150, and R ML (Indicating the reflectivity of reflective layer 120). According to Figure 6B As the thickness of the absorber pattern increases, the transmittance can decrease, but the phase difference can increase. When the thickness of the absorber pattern 150 is in the range of about 40 nm to about 55 nm, the phase difference can be in the range of about 170 degrees to about 235 degrees, and the transmittance can be in the range of about 0.8% to about 7.5%. When the thickness of the absorber pattern formed of chromium nitride (CrN) is about 48.5 nm, the phase difference can be about 216 degrees, and the transmittance can be about 3.5%. The phase shift mask 500 having an absorber pattern formed of chromium nitride (CrN) with a thickness of about 48.5 nm can suppress sidelobe defects that occur when ruthenium and / or molybdenum are applied to the absorber pattern. Therefore, the phase shift mask 500 can be applied to processes for manufacturing all semiconductor devices, including logic devices.

[0062] Figure 6C This is a graph showing the NILS values ​​of the dose in the phase-shift mask according to an exemplary embodiment and comparative example of the present invention.

[0063] Reference Figure 6C Similar to Figure 6A Under the conditions described in the exemplary embodiment of the present invention, the phase shift mask is configured to include a ruthenium layer with a thickness of 4 nm as a capping layer 130, a TaBO layer with a thickness of 4 nm as a buffer pattern 140, and a chromium nitride (CrN) layer with a thickness of 48.5 nm as an absorber pattern 150. Here, the absorber pattern has an L / S pattern shape. Additionally, the phase shift mask according to the comparative example is configured to include a TaBN layer with a thickness of 54.5 nm as an absorber pattern, and the other structures of the phase shift mask according to the comparative example are the same as the corresponding structures of the phase shift mask according to the exemplary embodiment including CrN described above. The NILS values ​​of the light source dose in the phase shift mask are simulated, and the simulation results are shown below. Figure 6C In the middle. For example Figure 6CAs shown, the NILS values of the phase shift masks according to the embodiments of the inventive concept are generally higher than the NILS values of the phase shift masks according to the comparative examples. For example, the NILS value of the comparative example is about 2.5 at a dose of about 67 mJ, while the NILS value of the embodiment is about 2.725 at the same dose (67 mJ). In other words, the NILS value of the example embodiment can increase by about 9% compared to the comparative example. In addition, the example embodiment can require a dose of about 50 mJ to have the same NILS value (about 2.5) as the comparative example, so the dose can decrease by about 25%. As a result, when the phase shift mask 500 according to the example embodiment is used, productivity can be improved by increasing throughput. In addition, the patterning quality can be improved. For example, line edge roughness (LER), local critical dimension uniformity (LCDU), single line open (SLO), and / or missing contact can be reduced. Thus, when an exposure process is performed on a photoresist layer by using the phase shift mask 500, a photoresist pattern having a fine pitch and an accurate shape can be formed. The photoresist pattern can be used to etch an etching target layer. Since the patterning process is performed using the photoresist pattern, a method of manufacturing a semiconductor device capable of reducing process defects and improving productivity can be provided and / or implemented.

[0064] Figures 7A-7C is a cross-sectional view illustrating a process of manufacturing a phase shift mask according to some example embodiments of the inventive concept. Figure 3

[0065] Referring to FIG. 1A, Figure 7A A substrate 100 can be provided. The substrate 100 can include a material having a low coefficient of thermal expansion. For example, the substrate 100 can include glass and / or silicon (Si). The substrate 100 can include a pattern area PA and a black border area BA, as described with reference to FIG. 1B. Figure 2 A lower conductive layer 110 can be formed on the second surface 100b of the substrate 100. The lower conductive layer 110 can include, for example, CrN, and the lower conductive layer 110 can be formed using a sputter deposition process.

[0066]

[0067] ​​A reflective layer 120 can be formed on the first surface 100a of the substrate 100. The formation of the reflective layer 120 can include alternately and repeatedly forming a low refractive index layer 122 and a high refractive index layer 124 on the first surface 100a of the substrate 100. The low refractive index layer 122 and the high refractive index layer 124 can be, for example, alternately stacked about 40 times to about 60 times, and the low refractive index layer 122 and the high refractive index layer 124 can be formed using, for example, a sputter deposition process. In some example embodiments, the formation of the reflective layer 120 can include performing a laser annealing process on a second portion S2 of the reflective layer 120 on the boundary area BA. Accordingly, the low refractive index layer 122 and the high refractive index layer 124 of the second portion S2 can be intermingled with each other by the laser annealing process. Accordingly, the reflective layer 120 can include a first portion S1 in which the low refractive index layer 122 and the high refractive index layer 124 are alternately stacked on the pattern area PA, and a second portion S2 in which the low refractive index layer 122 and the high refractive index layer 124 are intermingled with each other on the boundary area BA.

[0068] A capping layer 130 can be formed on the reflective layer 120. The capping layer 130 can include, for example, ruthenium, and the capping layer 130 can be formed using a sputter deposition process. The capping layer 130 can be formed to have a first thickness T1, as described with reference to FIG. 2. Figure 5

[0069] A buffer layer 140L can be formed on the capping layer 130. The buffer layer 140L can be formed to have a second thickness T2, as described with reference to FIG. 2. Figure 5 The buffer layer 140L can include a material having etch selectivity with respect to the capping layer 130. The buffer layer 140L can be referred to as an etch stop layer. In addition, the buffer layer 140L can include a material having etch selectivity with respect to an absorber layer 150L to be described later. For example, the buffer layer 140L can include at least one of Si, SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. For example, the material of the buffer layer 140L can be selected based on a type of etching gas to be used in forming an absorber pattern 150 in a subsequent process. For example, the buffer layer 140L can be formed using a chemical vapor deposition (CVD) process and / or a sputter deposition process.

[0070] An absorber layer 150L can be formed on the buffer layer 140L. The absorber layer 150L can be formed to have a third thickness T3, as described with reference to FIG. 2. Figure 5 ​The absorber layer 150L can be formed to include nitrogen and chromium. The absorber layer 150L can also include oxygen. The absorber layer 150L can be formed as a single layer in which the constituent elements of nitrogen and chromium are uniformly distributed, and / or the absorber layer 150L can be formed as a multi-layer in which the constituent elements of nitrogen and chromium vary according to height. The absorber layer 150L can be formed to have a nitrogen content profile described with reference to Figure 4A , Figure 4B and / or Figure 4C described with reference to FIG. 2. To achieve this, the flow rate of a gas including nitrogen and / or sputtering conditions can be varied when depositing the absorber layer 150L. The absorber layer 150L can also include oxygen. The absorber layer 150L can include at least one of chromium nitride (CrN) and chromium oxynitride (CrON).

[0071] With reference to Figure 7B , the laser can be radiated to the second portion S2 of the reflective layer 120 on the boundary area BA, and thus the second portion S2 can be annealed to form a hybrid structure.

[0072] With reference to Figure 7B and Figure 7C , a mask pattern MK can be formed on the absorber layer 150L. The mask pattern MK can be formed of the same material as the material of the buffer layer 140L or of a different material from the material of the buffer layer 140L. For example, the mask pattern MK can be a photoresist pattern. Alternatively, the mask pattern MK can be a hard mask pattern, and the mask pattern MK can include a silicon-containing material, a metal-containing material, a metal nitride, and / or a metal oxide. For example, the mask pattern MK can include at least one of SiN, SiO2, SiON, TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. For example, the material of the mask pattern MK can be selected based on the type of etching gas to be used in forming the absorber pattern 150 in a subsequent process.

[0073] The absorber layer 150L can be etched with the mask pattern MK as an etching mask to form the absorber pattern 150 and an opening 150P exposing a top surface of the buffer layer 140L between structures included in the absorber pattern 150. The etching of the absorber layer 150L can include using an etching gas, such as a fluorine-based etching gas including fluorine and / or a chlorine-based etching gas including chlorine. The fluorine-based etching gas can be, for example, SF6, CF4, and / or CHF3. The chlorine-based etching gas can be, for example, Cl2. When the absorber layer 150L is etched with the fluorine-based etching gas, the mask pattern MK and the buffer layer 140L can include, for example, SiN, SiO2, SiON, TaBO, TaO, and / or TaON. When the absorber layer 150L is etched with the chlorine-based etching gas, the mask pattern MK and the buffer layer 140L can include, for example, TaN, TaBN, TiN, Nb, and / or Ta.

[0074] Referring to Figure 7C and Figure 3 An anisotropic etching process can be performed to remove the mask pattern MK. At this time, the buffer layer 140L can also be etched to form the buffer pattern 140 and expose a top surface of the capping layer 130. The capping layer 130 can have excellent etching selectivity with respect to the buffer layer 140L, and thus the capping layer 130 can be hardly damaged by the anisotropic etching process. Accordingly, a phase shift mask 500 having a high quality capable of reducing process defects and improving productivity can be manufactured. Figure 3

[0075] Next, the phase shift mask 500 can be cleaned, and an inspection process can be performed to inspect whether there is a portion damaged by etching on a surface of the phase shift mask 500. When there is a portion damaged by etching, a repair process can be performed. The repair process can be performed using a repair gas including xenon (Xe) gas and / or fluorine (F) gas.

[0076] Meanwhile, if there is no buffer layer 140L, since there is almost no etching selectivity between chromium nitride of the absorber layer 150L and ruthenium of the capping layer 130, for example, the etching process of forming the absorber pattern 150 can damage the top surface of the capping layer 130. In this case, the ruthenium of the capping layer 130 can not react with the repair gas used in the repair process, and thus it is difficult to repair the damaged portion of the top surface of the capping layer 130. However, according to some example embodiments of the inventive concept, the buffer layer 140L having excellent etching selectivity with respect to the capping layer 130 and the absorber layer 150L can be used to prevent etching damage of the top surface of the capping layer 130, and thus a high-quality phase shift mask capable of reducing process defects and improving productivity can be manufactured.

[0077] ​If the absorber pattern 150 is formed of different materials (e.g., ruthenium, molybdenum, palladium, rhodium, platinum, and / or silver) rather than chromium nitride (CrN) and / or chromium oxynitride (CrON), it can be difficult to perform an etching process with an etching gas including fluorine and / or chlorine. Accordingly, process defects can increase and productivity can decrease. Accordingly, in some example embodiments of the inventive concept, chromium nitride, which has high feasibility, can be used as the absorber pattern 150, and thus productivity can be improved.

[0078] Figure 8 is a cross-sectional view illustrating a phase shift mask according to some example embodiments of the inventive concept.

[0079] Referring to Figure 8 In the phase shift mask 501 according to the current embodiment, the buffer layer 140L can be located directly on the reflective layer 120. For example, the entire top surface of the reflective layer 120 can directly contact the buffer layer 140L. Here, the buffer layer 140L can be formed of a silicon-containing layer. For example, the buffer layer 140L can include at least one of Si, SiN, SiO2, and SiON. The absorber pattern 150 can have the same materials and structures as the absorber pattern 150 described with reference to Figures 3-5 The absorber pattern 150 described with reference to Figure 5 may be located on the buffer layer 140L. For example, the absorber pattern 150 can be located directly on the buffer layer 140L. When the absorber pattern 150 is formed, the buffer layer 140L can serve as an etch stop layer, and can also serve as a capping layer that prevents etching damage of and / or protects the reflective layer 120. For example, the buffer layer 140L can prevent oxidation of the reflective layer. In the current embodiment, the buffer layer 140L can be referred to as an etch stop layer and / or a capping layer. The buffer layer 140L can have the second thickness T2 described with reference to Figure 5 The absorber pattern 150 can have the third thickness T3 described with reference to Figures 3-5 The second thickness T2 and the third thickness T3 can be the same as described above. The refractive index of the buffer layer 140L can be greater than the refractive index of the absorber pattern 150. The top surface of the buffer layer 140L can be exposed through the openings 150P between the structures included in the absorber pattern 150. The other structures can be the same / similar as described with reference to

[0080] Figure 9 is a cross-sectional view illustrating a process of manufacturing Figure 8 the phase shift mask. Additional descriptions related to the processes of manufacturing components having the same reference numerals will be omitted to avoid redundancy, and differences between the processes will be mainly described.

[0081] Referring to Figure 9The lower conductive layer 110 can be formed on the second surface 100b of the substrate 100. The reflective layer 120, the buffer layer 140L, and the absorber layer 150L can be sequentially formed on the first surface 100a of the substrate 100. At this time, the cap layer 130 can be omitted. The reflective layer 120 can be irradiated with, for example, a laser to form a hybrid structure in the second portion S2 of the reflective layer 120. A mask pattern MK can be formed on the absorber layer 150L. The mask pattern MK can be formed of a material having etching selectivity with respect to both the absorber layer 150L and the buffer layer 140L. For example, the mask pattern MK can be a photoresist pattern. Alternatively, the mask pattern MK can include at least one of TaBO, TaO, TaON, TaN, TaBN, TiN, Nb, and Ta. The absorber layer 150L can be etched with the mask pattern MK as an etching mask to form an absorber pattern 150 and expose a top surface of the buffer layer 140L through openings 150P between structures included in the absorber pattern 150. Next, referring to Figure 8 The mask pattern MK can be selectively removed to expose a top surface of the absorber pattern 150.

[0082] The cap layer 130 formed of ruthenium can be omitted in the phase shift mask 501 according to the current embodiment (see Figure 3 Thus, the process can be simplified and the yield can be improved.

[0083] The phase shift mask for EUV lithography according to the inventive concept can include an absorber pattern including chromium and nitrogen, and thus, a high-resolution image can be implemented. The absorber pattern can have a smaller refractive index and a larger thickness than a buffer pattern, and thus, a phase shift degree of EUV light can be increased. Thus, a high-resolution image can be easily implemented with the phase shift mask. In addition, when a silicon-containing layer is used as a buffer layer, a cap layer formed of ruthenium can be omitted. In this case, the structure and the process can be simplified. As a result, a phase shift mask for EUV lithography capable of implementing a high-resolution image can be provided.

[0084] The method of manufacturing a semiconductor device according to the inventive concept can use a phase shift mask for EUV lithography to reduce process defects and improve the yield.

[0085] In the method of manufacturing a phase shift mask for EUV lithography, according to some example embodiments of the inventive concept, a buffer layer and a mask pattern can be formed of a material having excellent etching selectivity with respect to an absorber pattern and a cap layer. Thus, process defects can be reduced and the yield can be improved.

[0086] While the inventive concept has been described with reference to some example embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the inventive concept. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all changes and modifications that come within the scope of the inventive concept are desired to be protected.

Claims

1. A phase-shifting mask for extreme ultraviolet lithography, comprising: Substrate; A reflective layer is located on the substrate; A capping layer, which is located on the reflective layer; A buffer pattern located on the capping layer, the buffer pattern including openings that expose the surface of the capping layer; as well as An absorber pattern is located on the buffer pattern, the absorber pattern having a refractive index smaller than that of the buffer pattern and a thickness greater than that of the buffer pattern. The buffer pattern comprises a material that has etch selectivity relative to the absorber pattern and the capping layer. The substrate includes a boundary region and a patterned region. The reflective layer comprises alternately stacked low-refractive-index layers and high-refractive-index layers. In this context, the low-refractive-index layer and the high-refractive-index layer on the boundary region are mixed together, and The thickness of each of the capping layer and the buffer pattern is less than the wavelength of the extreme ultraviolet light incident on the substrate.

2. The phase-shift mask according to claim 1, wherein, The absorber pattern includes at least one of chromium nitride and chromium oxynitride.

3. The phase-shift mask according to claim 2, wherein, The nitrogen content in the absorber pattern ranges from 5 at% to 70 at%.

4. The phase-shift mask according to claim 1, wherein, The absorber pattern comprises a first sub-absorber layer and a second sub-absorber layer stacked sequentially, and The nitrogen content in the first sub-absorber layer is different from the nitrogen content in the second sub-absorber layer.

5. The phase-shift mask according to claim 1, wherein, The thickness of the absorber pattern is in the range of 40 nm to 55 nm, and The thickness of the buffer pattern is in the range of 4 nm to 10 nm.

6. The phase-shift mask according to claim 1, wherein, The buffer pattern includes at least one of silicon, silicon nitride, silicon oxide, silicon oxynitride, tantalum borate, tantalum oxide, tantalum oxynitride, tantalum nitride, nitrided tantalum boride, titanium nitride, niobium, and tantalum.

7. The phase-shift mask according to claim 1, wherein, The absorber pattern is configured such that the extreme ultraviolet light reflected through the absorber pattern includes a phase difference of 170 to 235 degrees relative to the extreme ultraviolet light reflected through the opening.

8. A phase-shifting mask for extreme ultraviolet lithography, comprising: Substrate, which is located on the conductive layer; A reflective layer is located on the substrate; A capping layer, which is located on the reflective layer; An absorber pattern located on the capping layer, the absorber pattern including openings that expose the surface of the capping layer; as well as A buffer pattern, located between the capping layer and the absorber pattern, includes an opening that exposes the surface of the capping layer. The absorber pattern includes nitrogen and chromium, and The nitrogen content in the absorber pattern ranges from 5 at% to 70 at%. The substrate includes a boundary region and a patterned region. The reflective layer comprises alternately stacked low-refractive-index layers and high-refractive-index layers. In this context, the low-refractive-index layer and the high-refractive-index layer on the boundary region are mixed together, and The thickness of each of the capping layer and the buffer pattern is less than the wavelength of the extreme ultraviolet light incident on the substrate.

9. The phase-shift mask according to claim 8, wherein, The capping layer comprises a material with etch selectivity relative to the absorber pattern, and The thickness of the absorber pattern is greater than the thickness of the capping layer.

10. The phase-shift mask according to claim 9, wherein, The capping layer includes at least one of silicon, silicon nitride, silicon oxide, and silicon oxynitride.

11. The phase-shift mask according to claim 8, wherein, The absorber pattern also includes oxygen.

12. The phase-shift mask according to claim 8, wherein, The nitrogen content in the absorber pattern changes discontinuously or gradually depending on the height.

13. The phase-shift mask according to claim 8, wherein, The buffer pattern comprises a material that is etch-selective relative to the absorber pattern.

14. The phase-shift mask according to claim 13, wherein, The buffer pattern includes at least one of silicon, silicon nitride, silicon oxide, silicon oxynitride, tantalum borate, tantalum oxide, tantalum oxynitride, tantalum nitride, nitrided tantalum boride, titanium nitride, niobium, and tantalum. The capping layer includes ruthenium.

15. The phase-shift mask according to claim 13, wherein, The thickness of the absorber pattern is in the range of 40 nm to 55 nm, and The thickness of the buffer pattern is in the range of 4 nm to 10 nm.

16. A phase-shifting mask for extreme ultraviolet lithography, comprising: Substrate; A reflective layer is located on the substrate; A capping layer, which is located on the reflective layer; A buffer pattern located on the capping layer, the buffer pattern including openings that expose the surface of the capping layer; as well as An absorber pattern, located on the buffer pattern, comprising nitrogen and chromium. The buffer pattern comprises a material having etch selectivity relative to the absorber pattern, and The nitrogen content in the absorber pattern varies discontinuously or gradually depending on its distance from the buffer pattern. The substrate includes a boundary region and a patterned region. The reflective layer comprises alternately stacked low-refractive-index layers and high-refractive-index layers. In this context, the low-refractive-index layer and the high-refractive-index layer on the boundary region are mixed together, and The thickness of each of the capping layer and the buffer pattern is less than the wavelength of the extreme ultraviolet light incident on the substrate.

17. The phase-shift mask according to claim 16, wherein, The refractive index of the absorber pattern is less than that of the buffer pattern, and The thickness of the absorber pattern is greater than the thickness of the buffer pattern.

18. The phase-shift mask according to claim 16, wherein, The thickness of the absorber pattern is greater than the full width at half maximum (FWHM) wavelength of extreme ultraviolet (EUV) light, and the thickness of the buffer pattern is less than the FWHM wavelength of EUV light.

19. The phase-shift mask according to claim 16, wherein, The buffer pattern includes at least one of silicon, silicon nitride, silicon oxide, silicon oxynitride, tantalum borate, tantalum oxide, tantalum oxynitride, tantalum nitride, nitrided tantalum boride, titanium nitride, niobium, and tantalum.

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