Reflective mask blank, reflective mask, method for manufacturing a reflective mask, and method for manufacturing a semiconductor device

Abstract

To provide a reflection type mask blank, a reflection type mask, a method for manufacturing a reflection type mask, and a method for manufacturing a semiconductor device which can prevent occurrence of electrostatic breakdown in a substrate peripheral part.SOLUTION: A reflection type mask blank 100 includes a substrate 10, a multilayer reflection film 12 on the substrate 10, a protective film 14 on the multilayer reflection film 12, and an absorber film 16 on the protective film 14. The absorber film 16 has a buffer layer 18, and an absorption layer 20 provided on the buffer layer 18. When a distance between a center of the substrate 10 and an outer peripheral end of the protective film 14 is represented by Lcap and a distance between the center of the substrate 10 and an outer peripheral end of the buffer layer 18 is represented by Lbuf, Lcap≤Lbuf is satisfied. In a range within 0.5 mm from the side face of the substrate 10 toward the center of the substrate 10, there exists at least one part in which the total film thickness of the protective film 14 and the buffer layer 18 is 4.5 nm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device. [Background technology]

[0002] In recent years, with the increasing demand for higher density and precision in VLSI devices, EUV lithography, an exposure technology using extreme ultraviolet (EUV) light, is seen as a promising option. EUV light refers to light in the wavelength range of soft X-rays or vacuum ultraviolet light, specifically light with a wavelength of approximately 0.2 to 100 nm.

[0003] A reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film to absorb the exposure light. Light incident on the reflective mask mounted on an exposure machine for transferring a pattern onto a semiconductor substrate is absorbed in the areas with the absorber pattern and reflected by the multilayer reflective film in areas without the absorber pattern. The light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflection optical system.

[0004] Generally, a multilayer reflective film is used in which elements with different refractive indices are periodically stacked. For example, a Mo / Si periodic stacked film in which Mo films and Si films are alternately stacked for about 40 periods is preferably used as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm.

[0005] Patent Document 1 describes a reflective mask blank in which a multilayer reflective film that reflects EUV light, a protective film for protecting the multilayer reflective film, an absorber film that absorbs EUV light, and a resist film are formed in this order on a substrate, wherein the distance from the center of the substrate to the outer circumferential edge of the multilayer reflective film is L(ML), the distance from the center of the substrate to the outer circumferential edge of the protective film is L(Cap), the distance from the center of the substrate to the outer circumferential edge of the absorber film is L(Abs), and the distance from the center of the substrate to the outer circumferential edge of the resist film is L(Res), where L(Abs)>L(Res)>L(Cap)≧L(ML), and the outer circumferential edge of the resist film is located inside the outer circumferential edge of the substrate.

[0006] Patent Document 2 describes a reflective mask blank for exposure comprising a substrate, a multilayer reflective film that reflects exposure light and an absorbing film that absorbs exposure light, which are sequentially formed on the substrate, the multilayer reflective film being formed by alternately laminating heavy element material films and light element material films that have different refractive indices, and characterized in that the multilayer reflective film has a protective layer that protects at least the peripheral edge of the heavy element material film. Patent Document 2 also describes forming an absorbing film in a film formation area that is larger than the film formation area of ​​the multilayer reflective film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 021235 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-257824 Summary of the Invention [Problem to be solved by the invention]

[0008] A reflective mask blank generally has a structure in which a multilayer reflective film that reflects exposure light (EUV light) is formed on one main surface of a substrate, and an absorber film that absorbs exposure light (EUV light) is formed on this multilayer reflective film. When a reflective mask is manufactured using a reflective mask blank, a resist film for electron beam lithography is first formed on the surface of the reflective mask blank. Next, a desired pattern is written on this resist film with an electron beam, and the pattern is developed to form a resist pattern. Next, using this resist pattern as a mask, the absorber film is dry-etched to form an absorber pattern (transfer pattern). This allows the manufacture of a reflective mask in which an absorber pattern is formed on the multilayer reflective film.

[0009] FIG. 14 is an enlarged cross-sectional view of the outer peripheral edge of a conventional reflective mask blank 200. As shown in FIG. 14, the reflective mask blank 200 includes a substrate 210, a multilayer reflective film 212 formed on the substrate 210, a protective film 214 formed on the multilayer reflective film 212, an absorber film 216 formed on the protective film 214, an etching mask film 218 formed on the absorber film 216, and a resist film 220 formed on the etching mask film 218. The protective film 214 functions to protect the multilayer reflective film 212 from dry etching and cleaning in the manufacturing process of the reflective mask. The etching mask film 218 is a film for dry etching the absorber film 216 to form an absorber pattern (transfer pattern). The resist film 220 is a film for forming a pattern in the etching mask film 218. When the etching mask film 218 is not provided, a resist pattern is formed in the resist film 220, and the absorber film 216 is dry-etched using this resist pattern as a mask to form the absorber pattern (transfer pattern).

[0010] The resist film 220 is formed over the entire surface of the reflective mask blank 200, but to prevent the resist film 220 from peeling off and generating dust at the peripheral edge of the substrate 210, the resist film 220 is usually removed from the peripheral edge of the substrate where no mask pattern is formed (edge ​​rinse). This edge rinse is performed, for example, by removing a width of about 1 to 1.5 mm of the resist film 220 along the peripheral edge of the substrate 210 using a resist stripper. As shown in FIG. 14 , in the region R where the resist film 220 has been removed by edge rinse, the etching mask film 218 underneath the resist film 220 is exposed.

[0011] In a reflective mask that uses EUV light as exposure light, it is important to accurately control the positions of defects present on the multilayer reflective coating. This is because defects present on the multilayer reflective coating are almost impossible to repair and can result in serious phase defects in the transferred pattern. For this reason, a mark that serves as a reference for controlling the positions of defects on the multilayer reflective coating 212 may be formed in the reflective mask blank 200. This reference mark is also called a fiducial mark.

[0012] Figure 15 is an enlarged cross-sectional view of the outer peripheral edge of the reflective mask blank 200 on which the fiducial marks FM are formed. As shown in Figure 15, the fiducial marks FM are formed in an area outside the area PA where a pattern is formed in the absorber film 216. When forming the fiducial marks FM, first, a resist pattern 220a for forming the fiducial marks FM is formed in the resist film 220 by electron beam lithography, and then, using this resist pattern 220a as a mask, the etching mask film 218 and the absorber film 216 are etched by dry etching to form the fiducial marks FM.

[0013] As described above, in the region R from which the resist film 220 has been removed by edge rinsing, the etching mask film 218 underlying the resist film 220 is exposed. Therefore, the dry etching performed when forming the fiducial mark FM removes the etching mask film 218 and the absorber film 216 in the region R from which the resist film 220 has been removed, exposing the protective film 214 underlying the absorber film 216. At this time, the exposed protective film 214 may be damaged by the etching, resulting in the formation of an isolated island-shaped protective film 214a, as shown in FIG. 16 . This isolated island-shaped protective film 214a is a portion that is separated from the periphery and is not connected to the protective film 214b on the central side of the substrate 210.

[0014] When an isolated island-shaped protective film 214a is formed, the isolated island-shaped protective film 214a becomes charged during electron beam lithography to form a pattern on the absorber film 216. When the isolated island-shaped protective film 214a becomes charged, the isolated island-shaped protective film 214a is not provided with means for dissipating the charge (for example, a conductive pin), and therefore, the charge may be suddenly released from the isolated island-shaped protective film 214a, causing electrostatic breakdown. When the reflective mask blank 200 is damaged by electrostatic breakdown, the reflective mask blank 200 becomes unusable as a product, which has been a problem.

[0015] The present invention has been made to solve the above-mentioned problems, and aims to provide a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device that can prevent electrostatic breakdown from occurring at the peripheral edge of a substrate. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention has the following configuration.

[0017] (Configuration 1) A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, a protective film on the multilayer reflective film, and an absorber film on the protective film, The absorber film has a buffer layer and an absorption layer provided on the buffer layer. When the distance from the center of the substrate to the outer peripheral end of the protective film is Lcap and the distance from the center of the substrate to the outer peripheral end of the buffer layer is Lbuf, Lcap ≤ Lbuf. A reflective mask blank, wherein at least one location exists within a range of 0.5 mm or less from the side surface of the substrate toward the center of the substrate where the total film thickness of the protective film and the buffer layer is 4.5 nm or more.

[0018] (Configuration 2) The reflective mask blank according to Configuration 1, wherein the buffer layer contains at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y).

[0019] (Configuration 3) The reflective mask blank according to Configuration 1 or 2, wherein the total film thickness of the protective film and the buffer layer at the center of the substrate is 4.5 nm or more and 35 nm or less.

[0020] (Configuration 4) The reflective mask blank according to any one of Configurations 1 to 3, wherein when the distance from the center of the substrate to the outer peripheral end of the absorption layer is Labs, Lcap ≤ Labs.

[0021] (Configuration 5) The reflective mask blank according to any one of Configurations 1 to 4, wherein the protective film contains ruthenium (Ru).

[0022] (Configuration 6) A resist film is provided on the absorber film. When the distance from the center of the substrate to the outer peripheral end of the resist film is Lres, the reflective mask blank according to any one of Claims 1 to 5, wherein Lres < Lcap ≤ Lbuf.

[0023] (Configuration 7) 7. A reflective mask having an absorber pattern formed by patterning the absorber layer in the reflective mask blank according to any one of configurations 1 to 6.

[0024] (Configuration 8) The reflective mask according to configuration 7, wherein a reference mark is formed in the absorbing layer of the absorber film.

[0025] (Configuration 9) A method for producing a reflective mask, comprising patterning the absorber layer of the reflective mask blank according to any one of configurations 1 to 6 to form an absorber pattern.

[0026] (Configuration 10) 9. A method for manufacturing a semiconductor device, comprising the steps of: setting the reflective mask according to Structure 7 or 8 in an exposure apparatus having an exposure light source that emits EUV light; and transferring a transfer pattern to a resist film formed on a transfer substrate. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device that can prevent electrostatic breakdown from occurring at the peripheral edge of a substrate. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a cross-sectional schematic view showing an example of a reflective mask blank of the present embodiment, and is an enlarged view of the outer peripheral edge of a substrate. [Figure 2] FIG. 2 is a cross-sectional schematic view showing another example of a reflective mask blank of the present embodiment, in which the outer peripheral edge of the substrate is enlarged. [Figure 3] FIG. 2 is an enlarged cross-sectional view of the outer peripheral edge of a reflective mask blank on which a reference mark is formed. [Figure 4] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 5]3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 6] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 7] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 8] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 9] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 10] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 11] 3A and 3B are schematic diagrams for explaining the size relationships among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. [Figure 12] 1A to 1C are schematic diagrams showing an example of a method for manufacturing a reflective mask. [Figure 13] FIG. 1 is a diagram showing a schematic configuration of an EUV exposure apparatus. [Figure 14] FIG. 1 is an enlarged cross-sectional view of the outer peripheral edge of a conventional reflective mask blank. [Figure 15] FIG. 10 is an enlarged cross-sectional view of the outer peripheral edge of a conventional reflective mask blank on which a reference mark FM is formed. [Figure 16] FIG. 1 is an enlarged cross-sectional view of the outer peripheral edge of a conventional reflective mask blank on which an isolated island-shaped protective film is formed. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are intended to specifically explain the present invention, and are not intended to limit the scope of the present invention.

[0030] FIG. 1 is a schematic cross-sectional view showing an example of a reflective mask blank 100 of this embodiment, and is an enlarged view of the outer peripheral edge of a substrate 10. The reflective mask blank 100 shown in FIG. 1 has a substrate 10, a multilayer reflective film 12 formed on the substrate 10, a protective film 14 formed on the multilayer reflective film 12, and an absorber film 16 formed on the protective film 14. The absorber film 16 has a two-layer structure, including a buffer layer 18 formed in contact with the protective film 14, and an absorber layer 20 formed on the buffer layer 18. A back surface conductive film 22 for electrostatic chucking may be formed on the back surface of the substrate 10 (the surface opposite to the side on which the multilayer reflective film 12 is formed).

[0031] In this specification, "on" a substrate or a film includes not only cases where it is in contact with the upper surface of the substrate or film, but also cases where it is not in contact with the upper surface of the substrate or film. In other words, "on" a substrate or a film includes cases where a new film is formed above the substrate or film, or cases where another film is interposed between the substrate or film. Furthermore, "on" does not necessarily mean the upper side in the vertical direction. "On" merely indicates the relative positional relationship of the substrate, film, etc.

[0032] <Substrate> To prevent distortion of the transferred pattern due to heat during exposure to EUV light, the substrate 10 preferably has a low thermal expansion coefficient within the range of 0±5 ppb / ° C. Materials having a low thermal expansion coefficient within this range include, for example, SiO2-TiO2-based glass and multi-component glass ceramics.

[0033] The main surface of the substrate 10 on which a transfer pattern (an absorber pattern, described later) is to be formed is preferably processed to increase its flatness. Increasing the flatness of the main surface of the substrate 10 can improve the positional accuracy and transfer accuracy of the pattern. For example, in the case of EUV exposure, the flatness in a 132 mm × 132 mm area of ​​the main surface of the substrate 10 on which the transfer pattern is to be formed is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Furthermore, the main surface (back surface) opposite the side on which the transfer pattern is to be formed is fixed to an exposure apparatus by an electrostatic chuck, and in a 142 mm × 142 mm area thereof, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is a value that represents the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading), and is the absolute value of the difference in height between the highest point on the substrate surface above the focal plane, which is determined by the least squares method with the substrate surface as the reference plane, and the lowest point on the substrate surface below this focal plane.

[0034] In the case of EUV exposure, the surface roughness of the main surface of the substrate 10 on which the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured using an atomic force microscope.

[0035] The substrate 10 preferably has high rigidity to prevent deformation due to film stress of the films (such as the multilayer reflective film 12) formed thereon, and particularly preferably has a high Young's modulus of 65 GPa or more.

[0036] <Multilayer reflective film> The multilayer reflective film 12 has a structure in which a plurality of layers whose main components are elements with different refractive indices are periodically laminated. Generally, the multilayer reflective film 12 is made of a multilayer film in which thin films (high refractive index layers) of light elements or their compounds, which are high refractive index materials, and thin films (low refractive index layers) of heavy elements or their compounds, which are low refractive index materials, are alternately laminated for about 40 to 60 periods. To form the multilayer reflective film 12, high refractive index layers and low refractive index layers may be laminated in this order multiple times from the substrate 10 side. In this case, one laminate structure (high refractive index layer / low refractive index layer) constitutes one period.

[0037] It is preferable that the top layer of the multilayer reflective film 12, i.e., the surface layer of the multilayer reflective film 12 opposite the substrate 10, be a high refractive index layer. When a high refractive index layer and a low refractive index layer are stacked in this order from the substrate 10 side, the top layer is a low refractive index layer. However, when a low refractive index layer is the surface of the multilayer reflective film 12, the low refractive index layer is easily oxidized, reducing the reflectance of the surface of the multilayer reflective film, so it is preferable to form a high refractive index layer on the low refractive index layer. On the other hand, when a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 10 side, the top layer is a high refractive index layer. In that case, the top high refractive index layer becomes the surface of the multilayer reflective film 12.

[0038] The high refractive index layer included in the multilayer reflective film 12 is a layer made of a material containing Si. The high refractive index layer may contain elemental Si or a Si compound. The Si compound may contain Si and at least one element selected from the group consisting of B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film with excellent reflectance for EUV light can be obtained.

[0039] The low refractive index layer included in the multilayer reflective film 12 is a layer made of a material containing a transition metal. The transition metal included in the low refractive index layer is preferably at least one transition metal selected from the group consisting of Mo, Ru, Rh, and Pt. The low refractive index layer is more preferably a layer made of a material containing Mo.

[0040] For example, as the multilayer reflective film 12 for EUV light with a wavelength of 13 to 14 nm, a Mo / Si multilayer film in which Mo films and Si films are alternately stacked in about 40 to 60 periods can be preferably used.

[0041] The reflectance of such a single multilayer reflective film 12 is, for example, 65% or more. The upper limit of the reflectance of the multilayer reflective film 12 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 12 can be selected so as to satisfy Bragg's law.

[0042] The multilayer reflective film 12 can be formed by a known method, for example, ion beam sputtering.

[0043] For example, when the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film having a thickness of about 3 nm is formed on the substrate 10 by ion beam sputtering using a Mo target. Next, a Si film having a thickness of about 4 nm is formed using a Si target. By repeating this process, the multilayer reflective film 12 can be formed in which 40 to 60 periods of Mo / Si films are stacked. In this case, the surface layer of the multilayer reflective film 12 on the side opposite to the substrate 10 is a layer containing Si (Si film). The thickness of one period of the Mo / Si film is 7 nm.

[0044] <Protective film> The reflective mask blank 100 of this embodiment has a protective film 14 formed on the multilayer reflective film 12. The protective film 14 has the function of protecting the multilayer reflective film 12 from dry etching and cleaning in the manufacturing process of the reflective mask 110, which will be described later. The protective film 14 also has the function of protecting the multilayer reflective film 12 when repairing opacity defects in a transfer pattern using an electron beam (EB). By forming the protective film 14 on the multilayer reflective film 12, damage to the surface of the multilayer reflective film 12 can be suppressed when manufacturing the reflective mask 110. As a result, the multilayer reflective film 12 has good reflectance characteristics for EUV light.

[0045] The protective film 14 can be formed by a known method. Examples of methods for forming the protective film 14 include ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition. The protective film 14 may be formed by ion beam sputtering continuously after the formation of the multilayer reflective film 12.

[0046] The protective film 14 can be formed of a material with etching selectivity different from that of the buffer layer 18. Examples of materials that can be used for the protective film 14 include Ru, Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo), Si-(Ru, Rh, Cr, B), Si, Zr, Nb, La, and B. Among these, using a material containing ruthenium (Ru) improves the reflectivity characteristics of the multilayer reflective film 12. Specifically, Ru and Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo) are preferred. Such a protective film 14 is particularly effective when patterning the buffer layer 18 using chlorine-based or fluorine-based dry etching.

[0047] <Absorbent membrane> As described above, the absorber film 16 includes the buffer layer 18 formed in contact with the protective film 14 and the absorber layer 20 formed on the buffer layer 18 . The basic function of the absorber film 16 (including the absorber layer 20 and the buffer layer 18) is to absorb EUV light. The absorber film 16 may be an absorber film 16 designed to absorb EUV light, or an absorber film 16 with a phase shift function that also takes into account the phase difference of EUV light. The absorber film 16 with a phase shift function absorbs EUV light and reflects a portion of it to shift its phase. That is, in a reflective mask patterned with an absorber film 16 with a phase shift function, the portion where the absorber film 16 is formed absorbs and attenuates EUV light while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Furthermore, in the region where the absorber film 16 is not formed (the field portion), the EUV light is reflected by the multilayer reflective film 12 via the protective film 14. Therefore, a desired phase difference is generated between the light reflected from the absorber film 16 with a phase shift function and the light reflected from the field portion. The absorber film 16 having a phase shift function is preferably formed so that the phase difference between the light reflected from the absorber film 16 and the light reflected from the multilayer reflective film 12 is 170 to 190 degrees. Light beams with an inverted phase difference of approximately 180 degrees interfere with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast increases the resolution and can increase various exposure latitudes, such as exposure dose latitude and focus latitude.

[0048] The absorber layer 20 in the absorber film 16 is a film that primarily functions as the absorber film 16 described above and may be a single-layer film or a multilayer film consisting of multiple films. A single-layer film reduces the number of steps in mask blank manufacturing, improving production efficiency. A multilayer film allows the optical constants and film thickness of the upper absorber layer to be appropriately set so that it functions as an anti-reflection film during optical mask pattern defect inspection. This improves inspection sensitivity during optical mask pattern defect inspection. Furthermore, using a film containing oxygen (O) or nitrogen (N), which improves oxidation resistance, as the upper absorber layer improves stability over time. Thus, by forming the absorber layer 20 into a multilayer film, various functions can be added to the absorber layer 20. When the absorber layer 20 has a phase shift function, forming it into a multilayer film increases the range of optical adjustment, making it easier to obtain the desired reflectance.

[0049] The material of the absorption layer 20 is not particularly limited as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity relative to the buffer layer 18. As a material having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or a compound thereof, can be preferably used.

[0050] The absorber layer 20 can be formed by magnetron sputtering such as DC sputtering and RF sputtering. For example, the absorber layer 20 made of a tantalum compound or the like can be formed by reactive sputtering using a target containing tantalum and boron and argon gas to which oxygen or nitrogen is added.

[0051] The tantalum compound for forming the absorber layer 20 includes an alloy of Ta and the above-mentioned metals. When the absorber layer 20 is an alloy of Ta, the crystalline state of the absorber layer 20 is preferably an amorphous or microcrystalline structure in terms of smoothness and flatness. If the surface of the absorber layer 20 is not smooth or flat, the edge roughness of the absorber pattern described below may increase, resulting in poor dimensional accuracy of the pattern. The surface roughness of the absorber layer 20 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in root-mean-square roughness (Rms).

[0052] Examples of tantalum compounds for forming the absorption layer 20 include a compound containing Ta and B, a compound containing Ta and N, a compound containing Ta, O and N, a compound containing Ta and B and further containing at least one of O and N, a compound containing Ta and Si, a compound containing Ta, Si and N, a compound containing Ta and Ge, and a compound containing Ta, Ge and N.

[0053] Ta has a large absorption coefficient for EUV light and is a material that can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, Ta can be said to be a material with excellent processability for the absorber layer 20. Furthermore, by adding B, Si, and / or Ge, etc. to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber layer 20 can be improved. Furthermore, by adding N and / or O to Ta, the oxidation resistance of the absorber layer 20 can be improved, thereby improving stability over time.

[0054] <Etching mask film> 2 is a schematic cross-sectional view showing another example of the reflective mask blank 100 of this embodiment, and is an enlarged view of the outer peripheral edge of the substrate 10. As shown in FIG. 2, the reflective mask blank 100 can further have another thin film, such as a resist film 26, on the absorber film 16. Furthermore, the reflective mask blank 100 may further have an etching mask film 24 between the absorber layer 20 and the resist film 26. The etching mask film 24 is preferably made of a material that has a high etching selectivity of the absorbing layer 20 to the etching mask film 24. The etching selectivity of the absorbing layer 20 to the etching mask film 24 is preferably 1.5 or more, and more preferably 3 or more.

[0055] The reflective mask blank 100 of this embodiment preferably has an etching mask film 24 containing chromium (Cr) on the absorber layer 20. When the absorber layer 20 is etched with a fluorine-based gas, it is preferable to use chromium or a chromium compound as the material for the etching mask film 24. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. The etching mask film 24 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and it is particularly preferable to use a material containing Cr and N and / or O. Specific examples of such materials include CrN, CrO, and CrON.

[0056] When etching the absorption layer 20 with a chlorine-based gas that is substantially oxygen-free or a mixed gas of a chlorine-based gas and oxygen gas, it is preferable to use silicon or a silicon compound as the material for the etching mask film 24. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as metal silicon (metal silicides) and metal silicon compounds (metal silicide compounds) that contain a metal in silicon and silicon compounds. Examples of metal silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C, and H. Among these, it is particularly preferable to use a material containing Si and N and / or O as the material for the etching mask film. Specific examples of such materials include SiN and SiO. When etching the absorption layer 20 with a chlorine-based gas that does not substantially contain oxygen or when etching with a mixed gas of a chlorine-based gas and oxygen gas, an etching mask film 24 containing tantalum (Ta) can be used. Examples of materials containing Ta include materials containing Ta and one or more elements selected from O, N, C, B, and H. Among these, it is particularly preferable to use a material containing Ta and O as the material for the etching mask film. Specific examples of such materials include TaO, TaON, TaBO, and TaBON. Furthermore, the material of the etching mask film may be at least one metal selected from iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf) and yttrium (Y), or a compound thereof.

[0057] The thickness of the etching mask film 24 is preferably 3 nm or more in order to form a pattern with high precision in the absorber layer 20. Moreover, the thickness of the etching mask film 24 is preferably 15 nm or less in order to make the thickness of the resist film 26 thin.

[0058] <Backside conductive film> A backside conductive film 22 for electrostatic chuck may be formed on the backside of the substrate 10 (the surface opposite to the surface on which the multilayer reflective film 12 is formed). The sheet resistance required for the backside conductive film 22 for electrostatic chuck use is typically 100 Ω / □ (Ω / square) or less. The backside conductive film 22 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material for the backside conductive film 22 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material for the backside conductive film 22 is preferably a Cr compound containing Cr and at least one element selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the back surface conductive film 22 is preferably Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0059] The thickness of the back surface conductive film 22 is not particularly limited as long as it functions as a film for an electrostatic chuck, but is, for example, 10 nm to 200 nm.

[0060] The above-mentioned buffer layer 18 will be described in detail below. 2, the resist film 26 is formed on the entire surface of the reflective mask blank 100, but in order to prevent the resist film 26 from peeling off and generating dust at the peripheral edge of the substrate 10, the resist film 26 is usually removed from the peripheral edge of the substrate where no mask pattern is formed (edge ​​rinse). In the region R from which the resist film 26 has been removed by edge rinse, the etching mask film 24 underneath the resist film 26 is exposed. In the case of a reflective mask blank 100 without the etching mask film 24, the absorbing layer 20 is exposed.

[0061] In a reflective mask that uses EUV light as exposure light, it is important to accurately control the positions of defects present on the multilayer reflective film 12. This is because defects present on the multilayer reflective film 12 are almost impossible to repair and can become serious phase defects in the transferred pattern. For this reason, a mark that serves as a reference for controlling the positions of defects on the multilayer reflective film 12 may be formed in the reflective mask blank 100. This reference mark is sometimes called a fiducial mark.

[0062] Fig. 3 is an enlarged cross-sectional view of the outer peripheral edge of the reflective mask blank 100 on which the fiducial marks FM are formed. As shown in Fig. 3, the fiducial marks FM are formed in an area outside the area PA where a pattern is formed in the absorber layer 20. When forming the fiducial marks FM, first, a resist pattern 26a for forming the fiducial marks FM is formed in the resist film 26 by electron beam lithography, and then, using this resist pattern 26a as a mask, the etching mask film 24 and the absorber layer 20 are etched by dry etching to form the fiducial marks FM.

[0063] As described above, in the region R from which the resist film 26 has been removed by edge rinsing, the etching mask film 24 (or the absorbing layer 20) underlying the resist film 26 is exposed. Therefore, the etching mask film 24 and the absorbing layer 20 in the region R from which the resist film 26 has been removed are removed by dry etching when the fiducial marks FM are formed in the absorbing layer 20.

[0064] In the reflective mask blank 100 of this embodiment, the absorber film 16 includes a buffer layer 18 formed so as to be in contact with the protective film 14, and an absorbing layer 20 formed on the buffer layer 18. The buffer layer 18 is a layer that has etching resistance with respect to the absorbing layer 20, and also serves to prevent the formation of isolated islands of the protective film. Therefore, even if the etching mask film 24 and the absorption layer 20 are removed by dry etching when forming the reference mark FM in the region R where the resist film 26 has been removed by edge rinsing, the buffer layer 18 remains on the protective film 14, so it is possible to prevent the protective film 14 from being damaged by the etching.

[0065] The buffer layer 18 can be formed by a known film formation method, for example, by magnetron sputtering such as DC sputtering or RF sputtering.

[0066] The material of the buffer layer 18 is not particularly limited, but is preferably a material that is resistant to an etchant used in the dry etching that occurs when the fiducial marks FM are formed in the absorption layer 20. The buffer layer 18 can be formed, for example, from the same material as the etching mask film 24 described above. The buffer layer 18 preferably contains at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y). In addition, in the case of a reflective mask blank 100 that has an etching mask film 24, the buffer layer 18 is preferably formed from the same material as the etching mask film 24.

[0067] According to the reflective mask blank 100 of this embodiment, the buffer layer 18 remains on the protective film 14, and therefore it is possible to prevent the protective film 14 from being damaged by dry etching when forming the fiducial marks FM. This makes it possible to prevent the occurrence of "isolated islands of protective film" that conventionally occurred when forming the fiducial marks FM, and to prevent electrostatic breakdown caused by the isolated islands of protective film becoming charged.

[0068] In the reflective mask blank 100 of this embodiment, when the distance from the center of the substrate 10 to the outer circumferential edge of the protective film 14 is Lcap and the distance from the center of the substrate 10 to the outer circumferential edge of the buffer layer 18 is Lbuf, Lcap≦Lbuf holds. When the protective film 14 and the buffer layer 18 satisfy these conditions, the buffer layer 18 remains on the protective film 14 in the region R from which the resist film 26 has been removed by edge rinsing. Because the buffer layer 18 remains on the protective film 14, it is possible to prevent the generation of isolated islands of the protective film 14 in the region R from which the resist film 26 has been removed by edge rinsing.

[0069] In the reflective mask blank 100 of this embodiment, there is at least one location within a range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10 where the total thickness T of the protective film 14 and the buffer layer 18 is 4.5 nm or more. When the protective film 14 and the buffer layer 18 satisfy these conditions, in a region R from which the resist film 26 has been removed by edge rinsing (region R is typically a region with a width of about 1 to 1.5 mm from the side surface of the substrate 10 toward the center of the substrate 10), the buffer layer 18 remains on the protective film 14, and there is at least one location where the total thickness T of the protective film 14 and the buffer layer 18 is 4.5 nm or more. As a result, it is possible to ensure a sufficiently large total thickness T of the protective film 14 and the buffer layer 18 in the region R from which the resist film 26 has been removed by edge rinsing, making it possible to more reliably prevent the formation of isolated islands of the protective film 14. In the range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10, the total thickness T of the protective film 14 and the buffer layer 18 is preferably 5.0 nm or more, and more preferably 5.5 nm or more. The total thickness T is preferably 35 nm or less, and more preferably 30 nm or less.

[0070] In the reflective mask blank 100 of this embodiment, the total film thickness of the protective film 14 and buffer layer 18 at the center of the substrate 10 is preferably 4.5 nm or more, and more preferably 5.5 nm or more. Furthermore, the total film thickness is preferably 35 nm or less, and more preferably 30 nm or less. When the protective film 14 and buffer layer 18 satisfy these conditions, it is possible to ensure a sufficiently large total film thickness T of the protective film 14 and buffer layer 18 even in the region R where the resist film 26 has been removed by edge rinsing, thereby more reliably preventing the formation of isolated islands of the protective film 14.

[0071] In this specification, the center of the substrate 10 means the position of the center of gravity of a rectangular (e.g., square) substrate 10 (the position of the point on the main surface 10a of the substrate 10 corresponding to the position of the center of gravity). The side surface 10b of the substrate 10 is a plane that is approximately perpendicular to the two main surfaces of the substrate 10, and is sometimes called a "T-plane." The outer peripheral edge of a film or layer means the end of the film or layer that is located farthest from the center of the substrate 10. In addition, the deposition area (distance from the center of the substrate to the outer edge) and inclined cross-sectional shape (gradient profile) of the protective film 14, buffer layer 18, absorption layer 20 and etching mask film 24 at the outer edge of the substrate 10 can be appropriately adjusted by the opening dimensions of the PVD shield, the tapered shape of the opening, the distance between the shield and the substrate, etc.

[0072] 4 to 11 are schematic diagrams for explaining the size relationships among the protective film 14, buffer layer 18, absorption layer 20, etching mask film 24, and resist film 26 in the reflective mask blank 100 of this embodiment. In order to simplify the drawings, in Figs. 4 to 11, the thickness of each layer is made approximately constant toward its outer periphery.

[0073] Here, the distance from the center of the substrate 10 to the outer peripheral edge of each layer is defined as follows. Lcap: distance from the center of the substrate 10 to the outer edge of the protective film 14 Lbuf: distance from the center of the substrate 10 to the outer edge of the buffer layer 18 Labs: distance from the center of the substrate 10 to the outer edge of the absorption layer 20 Letc: distance from the center of the substrate 10 to the outer circumferential edge of the etching mask film 24 Lres: distance from the center of the substrate 10 to the outer circumferential edge of the resist film 26

[0074] In Figure 4, Lres <Lcap<Lbuf<Labs<Letcとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 and the absorption layer 20 that are not covered by the resist film 26 are removed by etching, resulting in the removal of the area surrounded by the dotted line in Fig. 4. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and resulting in the generation of "isolated islands of the protective film."

[0075] In Figure 5, Lres <Lcap<Labs<Lbuf<Letcとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 that is not covered by the resist film 26 is removed by dry etching. If the etching mask film 24 and the buffer layer 18 are etched with the same etchant (for example, if the etching mask film 24 and the buffer layer 18 are made of the same material), the buffer layer 18 that is not covered by the absorption layer 20 is etched with the same etchant as the etching mask film 24 (that is, the buffer layer 18 and the etching mask film 24 are etched simultaneously). Thereafter, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, and the region surrounded by the dotted line in FIG. 5 is removed. Even in this case, the entire protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in "isolated islands of protective film."

[0076] In Figure 6, Lres <Lcap<Lbuf<Letc<Labsとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 and the absorption layer 20 that are not covered by the resist film 26 are removed by etching, resulting in the removal of the area surrounded by the dotted line in Fig. 6. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in the generation of "isolated islands of the protective film."

[0077] In Figure 7, Lres <Lcap<Labs<Letc<Lbufとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 that is not covered by the resist film 26 is removed by dry etching. If the etching mask film 24 and the buffer layer 18 are etched with the same etchant (for example, if the etching mask film 24 and the buffer layer 18 are made of the same material), the buffer layer 18 that is not covered by the absorption layer 20 is etched with the same etchant as the etching mask film 24 (that is, the buffer layer 18 and the etching mask film 24 are etched simultaneously). Thereafter, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, and the region surrounded by the dotted line in FIG. 7 is removed. Even in this case, the entire protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in "isolated islands of protective film."

[0078] In Figure 8, Lres <Lcap<Letc<Lbuf<Labsとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 and the absorption layer 20 that are not covered by the resist film 26 are removed by etching, resulting in the removal of the region surrounded by the dotted line in Fig. 8. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and resulting in the generation of "isolated islands of the protective film."

[0079] In Figure 9, Lres <Lcap<Letc<Labs<Lbufとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 that is not covered by the resist film 26 is removed by dry etching. If the etching mask film 24 and the buffer layer 18 are etched with the same etchant (for example, if the etching mask film 24 and the buffer layer 18 are made of the same material), the buffer layer 18 that is not covered by the absorption layer 20 is etched with the same etchant as the etching mask film 24 (that is, the buffer layer 18 and the etching mask film 24 are etched simultaneously). Thereafter, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, and the region surrounded by the dotted line in FIG. 9 is removed. Even in this case, the entire protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in "isolated islands of protective film."

[0080] In Figure 10, Lres <Letc<Lcap<Lbuf<Labsとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 and the absorption layer 20 that are not covered by the resist film 26 are removed by etching, resulting in the removal of the region surrounded by the dotted line in Fig. 10. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in the generation of "isolated islands of the protective film."

[0081] In Figure 11, Lres <Letc<Lcap<Labs<Lbufとなっている。 During dry etching to form the fiducial marks FM, the etching mask film 24 that is not covered by the resist film 26 is removed by dry etching. If the etching mask film 24 and the buffer layer 18 are etched with the same etchant (for example, if the etching mask film 24 and the buffer layer 18 are made of the same material), the buffer layer 18 that is not covered by the absorption layer 20 is etched with the same etchant as the etching mask film 24 (that is, the buffer layer 18 and the etching mask film 24 are etched simultaneously). Thereafter, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, and the region surrounded by the dotted line in FIG. 11 is removed. Even in this case, the entire protective film 14 remains covered by the buffer layer 18, which prevents the protective film 14 from being damaged by etching and resulting in "isolated islands of protective film."

[0082] In the reflective mask blank 100 of this embodiment, it is preferable that Lcap≦Labs. When Lcap≦Labs, even when the etching mask film 24 and the buffer layer 18 are etched with the same etchant, the entire surface of the protective film 14 remains covered with the buffer layer 18, and therefore it is possible to more reliably prevent the protective film 14 from being damaged by etching and resulting in the generation of "isolated islands of protective film."

[0083] In the reflective mask blank 100 of the present embodiment, it is preferable that Lres < Lcap ≤ Lbuf. When the resist film 26 at the peripheral portion of the substrate 10 is removed by the edge rinse, Lres < Lcap often occurs. Even in this case, during the dry etching for forming the reference mark FM, since the entire surface of the protective film 14 is maintained covered with the buffer layer 18, it is possible to more reliably prevent the occurrence of "island-shaped protective films" due to the protective film 14 being damaged by etching.

[0084] <Method for manufacturing a reflective mask> Using the reflective mask blank 100 of the present embodiment, the reflective mask 110 of the present embodiment can be manufactured. Hereinafter, an example of a method for manufacturing a reflective mask will be described.

[0085] FIG. 12 is a schematic diagram showing an example of a method for manufacturing a reflective mask 110. As shown in FIG. 12, first, a reflective mask blank 100 having a substrate 10, a multilayer reflective film 12 formed on the surface of the substrate 10, a protective film 14 formed on the multilayer reflective film 12, an absorber film 16 (buffer layer 18 and absorber layer 20) formed on the protective film 14, and a back surface conductive film 22 formed on the back surface of the substrate 10 is prepared (FIG. 12(a)). Next, a resist film 26 is formed on the absorber film 16 (FIG. 12(b)). In order to suppress the generation of dust due to the peeling of the resist film 26 at the peripheral portion 27 of the substrate, the resist film 26 at the peripheral portion 27 of the substrate is removed with a solvent in which the resist film 26 dissolves (edge rinse) (FIG. 12(c)). A pattern is drawn on the resist film 26 by an electron beam lithography apparatus, and through further development and rinse steps, a resist pattern 26a is formed (FIG. 12(d)).

[0086] Using the resist pattern 26a as a mask, the absorber layer 20 of the absorber film 16 is dry-etched. As a result, the portion of the absorber layer 20 not covered by the resist pattern 26a is etched, and a pattern is formed in the absorber layer 20 (FIG. 12(e)).

[0087] The etching gas for the absorption layer 20 may be, for example, a fluorine-based gas and / or a chlorine-based gas. Examples of the fluorine-based gas include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2. Examples of the chlorine-based gas include Cl2, SiCl4, CHCl3, CCl4, and BCl3. Alternatively, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 at a predetermined ratio may be used. These etching gases may further contain an inert gas such as He and / or Ar, as necessary.

[0088] After the pattern is formed in the absorber layer 20, the buffer layer 18 is patterned by dry etching to form an absorber pattern 16a. The resist pattern 26a is removed using a resist remover. After the resist pattern 26a is removed, a wet cleaning process using an acidic or alkaline aqueous solution is performed to obtain the reflective mask 110 of this embodiment (FIG. 12(f)).

[0089] In addition, when a reflective mask blank 100 in which an etching mask film 24 is formed on the absorber film 16 is used, an additional process is performed in which a pattern (etching mask pattern) is formed on the etching mask film 24 using the resist pattern 26a as a mask, and then a pattern is formed on the absorber layer 20 using the etching mask pattern as a mask.

[0090] The reflective mask 110 thus obtained has a structure in which a multilayer reflective film 12, a protective film 14, and an absorber pattern 16a are laminated on a substrate 10.

[0091] An area 30 where the multilayer reflective film 12 (including the protective film 14) is exposed has a function of reflecting EUV light. An area 32 where the multilayer reflective film 12 (including the protective film 14) is covered with the absorber pattern 16a has a function of absorbing EUV light.

[0092] <Method of manufacturing a semiconductor device> A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask 110 of this embodiment. This transfer pattern has a shape that is the result of transferring the pattern of the reflective mask 110. By forming a transfer pattern on a semiconductor substrate using the reflective mask 110, a semiconductor device can be manufactured.

[0093] 13 shows a schematic configuration of an EUV exposure tool 50, which is an apparatus for transferring a transfer pattern onto a resist film formed on a semiconductor substrate 60. The EUV exposure tool 50 includes an EUV light generation unit 51, an irradiation optical system 56, a reticle stage 58, a projection optical system 57, and a wafer stage 59, which are precisely arranged along the optical path axis of the EUV light. The container of the EUV exposure tool 50 is filled with hydrogen gas.

[0094] The EUV light generation unit 51 has a laser light source 52, a tin droplet generation unit 53, a capture unit 54, and a collector 55. When the high-power carbon dioxide laser from the laser light source 52 is irradiated onto the tin droplets emitted from the tin droplet generation unit 53, the tin droplets are converted into plasma, and EUV light is generated. The generated EUV light is collected by the collector 55 and passes through an irradiation optical system 56 to be incident on a reflective mask 110 set on a reticle stage 58. The EUV light generation unit 51 generates EUV light with a wavelength of, for example, 13.53 nm.

[0095] The EUV light reflected by the reflective mask 110 is reduced to a pattern image light, usually about 1 / 4, by the projection optical system 57 and projected onto the semiconductor substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred onto the resist film on the semiconductor substrate 60.

[0096] By developing the exposed resist film, a resist pattern can be formed on the semiconductor substrate 60. By etching the semiconductor substrate 60 using the resist pattern as a mask, an integrated circuit pattern can be formed on the semiconductor substrate. By going through these steps and other necessary steps, a semiconductor device can be manufactured. [Example]

[0097] Examples 1 to 3 and Comparative Example 1 will be described below.

[0098] First, a substrate 10 having a polished main surface and a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) was prepared. This substrate 10 was made of low-thermal expansion glass (SiO2-TiO2-based glass). The main surface of the substrate 10 was polished through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0099] Next, a multilayer reflective film 12 was formed on the main surface of the substrate 10. The multilayer reflective film 12 formed on the substrate 10 was a periodic multilayer reflective film 12 made of Mo and Si to be suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 12 was formed by alternately laminating Mo films and Si films on the substrate 10 by ion beam sputtering using a Mo target and a Si target and krypton (Kr) as the process gas. First, a Si film was formed to a thickness of 4.2 nm, followed by a Mo film to a thickness of 2.8 nm. This constitutes one cycle, and 40 cycles were similarly laminated, after which a Si film was finally formed to a thickness of 4.0 nm.

[0100] Next, a protective film 14 made of RuNb was formed on the multilayer reflective film 12. The protective film 14 was formed by magnetron sputtering in an Ar gas atmosphere using a RuNb target. The thickness of the protective film 14 (thickness at the center of the substrate 10) was 3.5 nm.

[0101] Next, a buffer layer 18 was formed on the protective film 14. The composition and film thickness (film thickness at the center of the substrate 10) of the buffer layer 18 are shown in Table 1 below. The buffer layers 18 of Example 1, Example 3, and Comparative Example 1 were formed by magnetron sputtering in a mixed gas atmosphere of Ar gas, O2 gas, and N2 gas using a Cr target. The buffer layer 18 of Example 2 was formed by magnetron sputtering in a mixed gas atmosphere of Ar gas and O2 gas using a TaB target.

[0102] Next, an absorption layer 20 was formed on the buffer layer 18. The composition and film thickness of the absorption layer 20 are shown in Table 1 below. The absorption layers 20 of Example 1, Example 3, and Comparative Example 1 were formed by magnetron sputtering in a mixed gas atmosphere of Ar gas and N2 gas using a TaB target. The absorption layer 20 of Example 2 was formed by magnetron sputtering in an Ar gas atmosphere using a RuCr target.

[0103] In Example 3, an etching mask film 24 made of the same CrON as the buffer layer 18 was further formed on the absorption layer 20. The film thickness of the etching mask film 24 was 6 nm.

[0104] In Examples 1 and 2, the films of each layer were formed such that Lml < Lcap ≤ Lbuf ≤ Labs. In Example 3, the films of each layer were formed such that Lml < Lcap ≤ Lbuf < Labs = Letc. In Comparative Example 1, the films of each layer were formed such that Lml < Lbuf < Lcap. The meaning of each symbol is the same as the meaning defined above. Lml means the distance from the center of the substrate 10 to the outer peripheral end of the multilayer reflection film 12. The adjustment of the film formation range of each layer was performed by a method using a shielding member as disclosed in International Publication No. 2014 / 021235.

[0105] In Examples 1 to 3, the protective film 14 and the buffer layer 18 were formed so that there was at least one location within 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10 where the total thickness of the protective film 14 and the buffer layer 18 was 4.5 nm or more, as shown in Table 1. In Comparative Example 1, the protective film 14 and the buffer layer 18 were formed so that there was no location within 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10 where the total thickness of the protective film 14 and the buffer layer 18 was 4.5 nm or more. The thickness of each layer at the outer periphery was adjusted by adjusting the opening dimensions of the PVD shield using magnetron sputtering.

[0106] [Table 1]

[0107] Next, a reflective mask 110 was fabricated using the reflective mask blank 100 prepared above. Specifically, a resist film 26 was first formed on the absorption layer 20 or the etching mask film 24. After forming the resist film 26, the resist film 26 on the peripheral edge of the substrate was removed with a resist remover (edge ​​rinse). After performing the edge rinse, a pattern was written on the resist film 26 using an electron beam lithography system to form a resist pattern 26a. Using the resist pattern 26a as a mask, the absorption layer 20 was dry-etched to form the fiducial mark FM. Note that the absorption layer 20 in Examples 1 and 3 and Comparative Example 1 was dry-etched using Cl2 gas, while the absorption layer 20 in Example 2 was dry-etched using a mixed gas of Cl2 gas and O2 gas. Furthermore, in Example 3, the etching mask film 24 was dry-etched using a mixed gas of Cl2 gas and O2 gas using the resist pattern 26a as a mask to form an etching mask pattern, and then the absorption layer 20 was dry-etched using this etching mask pattern as a mask to form the fiducial mark FM.

[0108] After forming the fiducial marks FM on the absorber layer 20, the resist pattern 26a on the absorber layer 20 or the etching mask film 24 was removed with a resist remover. A resist film for forming the absorber pattern 16a was then formed on the absorber layer 20 or the etching mask film 24. A pattern was written on the resist film using an electron beam lithography system to form a resist pattern, and then the absorber layer 20 and the buffer layer 18 were dry-etched using the resist pattern as a mask to form the absorber pattern 16a. The absorber layer 20 of Examples 1 and 3 and Comparative Example 1 was dry-etched using Cl2 gas, and the buffer layer 18 was dry-etched using a mixed gas of Cl2 gas and O2 gas. The absorber layer 20 of Example 2 was dry-etched using a mixed gas of Cl2 gas and O2 gas, and the buffer layer 18 was dry-etched using Cl2 gas. In addition, in Example 3, the etching mask film 24 was dry-etched using the resist pattern as a mask to form an etching mask pattern, and then the absorber layer 20 was dry-etched using this etching mask pattern as a mask, and the etching mask pattern was removed simultaneously with the dry etching of the buffer layer 18 to form the absorber pattern 16a.

[0109] The top surface of the outermost periphery of the reflective mask 110 obtained in this manner was observed by TEM. As a result, in the reflective masks of Examples 1 to 3, no isolated island-shaped protective film was observed in region R of the substrate periphery. Furthermore, no traces of electrostatic breakdown due to the isolated island-shaped protective film were observed.

[0110] On the other hand, in the reflective mask of Comparative Example 1, isolated islands of the protective film were generated in the region R at the periphery of the substrate. Also, traces of electrostatic breakdown caused by the isolated islands of the protective film were confirmed. [Explanation of symbols]

[0111] 10 Substrate 12 Multilayer reflective film 14 Protective film 16 Absorber membrane 18 Buffer layer 20 Absorbing layer 16a Absorber pattern 22 Backside conductive film 24 Etching mask film 26a Resist pattern 26 Resist film 50 EUV exposure equipment 100 Reflective Mask Blanks 110 Reflective mask

Claims

1. A reflective mask blank comprising: a substrate; a multilayer reflective film on the substrate; a protective film on the multilayer reflective film; an absorber film on the protective film; and an etching mask film on the absorber film, the absorber film has a buffer layer and an absorber layer provided on the buffer layer, A reflective mask blank characterized in that, when the distance from the center of the substrate to the outer peripheral edge of the protective film is Lcap, the distance from the center of the substrate to the outer peripheral edge of the buffer layer is Lbuf, and the distance from the center of the substrate to the outer peripheral edge of the etching mask film is Letc, Lcap≦Lbuf<Letc.

2. 2. The reflective mask blank according to claim 1, wherein the buffer layer contains at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y).

3. A reflective mask blank as described in claim 1 or 2, characterized in that the etching mask film contains at least one selected from chromium (Cr), silicon (Si), tantalum (Ta), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf) and yttrium (Y).

4. 4. The reflective mask blank according to claim 1, wherein, when the distance from the center of the substrate to the outer peripheral edge of the absorption layer is taken as Labs, Lcap<Labs.

5. 5. The reflective mask blank according to claim 1, wherein the protective film contains ruthenium (Ru).

6. 6. The reflective mask blank according to claim 1, further comprising a resist film on the absorber film, wherein Lres is the distance from the center of the substrate to the outer peripheral edge of the resist film, and Lres<Lcap≦Lbuf.

7. 7. A reflective mask, comprising the reflective mask blank according to claim 1, wherein the absorbing layer has a patterned absorber pattern.

8. 8. The reflective mask according to claim 7, wherein a reference mark is formed in the absorbing layer of the absorber film.

9. A method for manufacturing a reflective mask, comprising patterning the absorber layer of the reflective mask blank according to claim 1 to form an absorber pattern.

10. 9. A method for manufacturing a semiconductor device, comprising the steps of: setting the reflective mask according to claim 7 in an exposure apparatus having an exposure light source that emits EUV light; and transferring a transfer pattern onto a resist film formed on a transfer substrate.

Images