Reflective mask blank, reflective mask, manufacturing method of reflective mask blank, and manufacturing method of reflective mask

Abstract

To provide a structure equipped with a protective film that exhibits excellent etching resistance and reduced mixing with a multi-layered reflective film.SOLUTION: A reflective mask blank for EUV lithography comprises a substrate, a multi-layered reflective film that reflects EUV light, a protective film that protects the multi-layered reflective film, and an absorption film that absorbs EUV light, in this order from bottom to top. The protective film is provided with an upper layer that comprises a rhodium-based material and contains Rh, or Rh and at least one element selected from the group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr, and Ti, and a lower layer that, in the EUV region, satisfies k<-0.15n+0.16 (where n is the index of refraction and k is the extinction coefficient).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, with the miniaturization of semiconductor devices, EUV lithography (EUVL), an exposure technology using extreme ultraviolet (EUV), has been developed. EUV includes soft X-rays and vacuum ultraviolet light, and specifically refers to light with a wavelength of about 0.2 nm to 100 nm. At present, EUV with a wavelength of about 13.5 nm is mainly being considered.

[0003] A reflective mask is used in EUVL. The reflective mask includes, in this order, a substrate, a multilayer reflective film, and an absorbing film with an aperture pattern formed therein. In EUVL, the aperture pattern of the reflective mask is transferred to a target substrate such as a semiconductor substrate.

[0004] A known reflective mask configuration has a protective film provided between the reflective multilayer film and the absorbing film. The protective film protects the reflective multilayer film from etching and other processes that are performed when forming an aperture pattern in the absorbing film during mask manufacturing, and is a film that remains on the reflective mask after manufacturing.

[0005] For example, Patent Document 1 describes a reflective mask blank comprising a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light, an absorbing film formed on the multilayer reflective film and selectively absorbing the exposure light, and an intermediate layer formed between the multilayer reflective film and the absorbing film and having resistance to the etching environment of the absorbing film, wherein the material of the intermediate layer contains at least one element selected from Cr, Ru, and Rh, and Si. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent No. 4346656 Summary of the Invention [Problem to be solved by the invention]

[0007] The material of the protective film is selected in consideration of the material of the absorbing film and the etching conditions according to the absorbing film. However, in recent years, various materials have been considered as the absorbing film. Depending on the material of the absorbing film and the etching conditions of the absorbing film, the resistance of the conventional protective film material may not be sufficient, and the multilayer reflective film may not be sufficiently protected. On the other hand, when selecting the material of the protective film, it is also necessary to consider the mixing between the protective film and the multilayer reflective film directly below, and the effect on the reflectance of the exposure light.

[0008] Therefore, an object of one embodiment of the present disclosure is to provide a configuration including a protective film that has excellent etching resistance and is suppressed from mixing with a multilayer reflective film. [Means for solving the problem]

[0009] A reflective mask blank according to one embodiment of the present disclosure is a reflective mask blank for EUV lithography having, in this order from bottom to top, a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and an absorbing film that absorbs the EUV light, wherein the protective film contains Rh. Contains 50 to 100 atomic percent The electrode comprises an upper layer made of a rhodium-based material and a lower layer containing at least one element selected from the group consisting of Ru, Nb, Mo, Zr, Y, C, and B. Effect of the Invention

[0010] According to one aspect of the present disclosure, it is possible to provide a configuration including a protective film that has excellent etching resistance and is suppressed from mixing with a multilayer reflective film. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a cross-sectional view showing a reflective mask blank according to an embodiment. [Diagram 2] FIG. 1 is a cross-sectional view showing a reflective mask according to an embodiment. [Diagram 3] 3 is a cross-sectional view showing an example of EUV light reflected by the reflective mask of FIG. 2. [Figure 4] FIG. 4 is a diagram showing an example of the refractive index and extinction coefficient of each substance. [Diagram 5] 1 is a flowchart showing a method for manufacturing a reflective mask blank according to an embodiment. [Figure 6] 1 is a flowchart showing a method for manufacturing a reflective mask according to an embodiment. [Figure 7] FIG. 2 is a diagram showing the analysis and observation results of the reflective mask blank of Example 1. [Figure 8] FIG. 1 shows the analysis and observation results of the reflective mask blank of Example 2. [Figure 9] FIG. 13 is a diagram showing the analysis and observation results of the reflective mask blank of Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and the description may be omitted. In the specification, the symbol "~" indicating a range of values ​​means that the values ​​before and after the symbol are included as the lower and upper limits.

[0013] 1 to 3, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The Z-axis direction is perpendicular to the surface direction of the substrate 10, with the positive direction of the Z axis (+Z direction) being the upward direction and the negative direction of the Z axis (-Z direction) being the downward direction. Here, the side irradiated with the EUV light is the upper side, and the opposite side is the lower side. The X-axis direction is perpendicular to the incidence surface of the EUV light (the surface including the incident light beam and the reflected light beam). As shown in FIG. 3, when viewed from the X-axis direction, the incident light beam and the reflected light beam are inclined toward the Y-axis direction as they approach the -Z axis direction or the -Z axis direction.

[0014] A reflective mask blank 1 according to one embodiment will be described with reference to Fig. 1. The reflective mask blank 1 has at least a substrate 10, a multilayer reflective film 11, a protective film 12, an absorbing film 13, and an etching mask film 14, in this order from bottom to top. As shown in Fig. 1, in this embodiment, the protective film 12 has at least a lower layer 12L and an upper layer 12U formed on the lower layer 12L. The multilayer reflective film 11, the lower layer 12L of the protective film 12, the upper layer 12U of the protective film 12, the absorbing film 13, and the etching mask film 14 are formed on the upper main surface (upper surface) 10a of the substrate 10, in this order from bottom to top.

[0015] The reflective mask blank 1 may further have a functional film not shown in Fig. 1. For example, the reflective mask blank 1 may have a conductive film on the underside. For example, the conductive film may be formed on the underside 10b, which is the surface opposite to the upper surface 10a of the substrate 10. The conductive film is used, for example, to attach the reflective mask 2 to an electrostatic chuck of an exposure tool.

[0016] Although not shown, the reflective mask blank 1 may have a buffer film between the protective film 12 and the absorbing film 13. The buffer film protects the protective film 12 from an etching gas that forms an opening pattern 13a in the absorbing film 13. The buffer film is etched more slowly than the absorbing film 13. Unlike the protective film 12, the buffer film will ultimately have the same opening pattern as the opening pattern 13a of the absorbing film 13.

[0017] Next, a reflective mask 2 according to one embodiment will be described with reference to Figures 2 and 3. The reflective mask 2 is, for example, a reflective mask blank 1 shown in Figure 1 in which an opening pattern 13a corresponding to a desired semiconductor device pattern is formed in an absorbing film 13. Note that the etching mask film 14 shown in Figure 1 is removed after the opening pattern 13a is formed in the absorbing film 13. In EUVL, the opening pattern 13a of the absorbing film 13 is transferred to a target substrate such as a semiconductor substrate. Transferring includes reducing and transferring.

[0018] The substrate 10, the multilayer reflective film 11, the protective film 12, the absorbing film 13, and the etching mask film 14 will be described below.

[0019] The substrate 10 is, for example, a glass substrate. The material of the substrate 10 is preferably quartz glass containing TiO2. Quartz glass has a smaller linear expansion coefficient and a smaller dimensional change due to temperature change than general soda-lime glass. Quartz glass may contain 80% to 95% by mass of SiO2 and 4% to 17% by mass of TiO2. When the TiO2 content is 4% to 17% by mass, the linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. Quartz glass may contain a third component or impurity other than SiO2 and TiO2. The material of the substrate 10 may be crystallized glass in which a β-quartz solid solution is precipitated, silicon, metal, or the like.

[0020] As described above, the multilayer reflective film 11 and the like are formed on the upper surface 10a of the substrate 10. The size of the substrate 10 in plan view (viewed in the Z-axis direction) is, for example, 152 mm long and 152 mm wide. The vertical and horizontal dimensions may be 152 mm or more. The upper surface 10a and the lower surface 10b of the substrate 10 each have a square quality assurance area, for example, 142 mm long and 142 mm wide, in the center of each. The quality assurance area of ​​the upper surface 10a preferably has a root-mean-square roughness (RMS) of 0.15 nm or less and a flatness of 100 nm or less. In addition, it is preferable that the quality assurance area of ​​the upper surface 10a does not have any defects that cause phase defects.

[0021] The multilayer reflective film 11 is a film that reflects EUV light, and is, for example, a film in which high-refractive index layers and low-refractive index layers are alternately laminated. The high-refractive index layers are made of, for example, silicon (Si), and the low-refractive index layers are made of, for example, molybdenum (Mo). Therefore, a Mo / Si multilayer reflective film can be used as the multilayer reflective film. Note that Ru / Si multilayer reflective film, Mo / Be multilayer reflective film, Mo compound / Si compound multilayer reflective film, Si / Mo / Ru multilayer reflective film, Si / Mo / Ru / Mo multilayer reflective film, Si / Ru / Mo / Ru multilayer reflective film, etc. can also be used as the multilayer reflective film 11.

[0022] The thickness of each layer constituting the multilayer reflective film 11 and the number of layer repetition units can be appropriately selected according to the material of each layer and the reflectivity with respect to EUV light. When the multilayer reflective film 11 is a Mo / Si multilayer reflective film, in order to achieve a reflectivity of 60% or more with respect to EUV light with an incident angle θ (Figure 3) of 6°, a Mo layer with a thickness of 2.3 ± 0.1 nm and a Si layer with a thickness of 4.5 ± 0.1 nm may be laminated so that the number of repetition units is 30 or more and 60 or less. The multilayer reflective film 11 preferably has a reflectivity of 60% or more with respect to EUV light with an incident angle θ of 6°. More preferably, the reflectivity is 65% or more.

[0023] The film formation method of each layer constituting the multilayer reflective film 11 is, for example, a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like. When forming a Mo / Si multilayer reflective film using the ion beam sputtering method, an example of the film formation conditions for each of the Mo layer and the Si layer is as follows. <Film formation conditions for Si layer> Target: Si target Sputtering gas: Ar gas Gas pressure: 1.3×10 -2 Pa ~ 2.7×10 -2 Pa Ion acceleration voltage: 300V ~ 1500V Film formation rate: 0.030 nm / sec ~ 0.300 nm / sec Thickness of Si layer: 4.5 ± 0.1 nm <Film formation conditions for Mo layer> Target: Mo target Sputtering gas: Ar gas Gas pressure: 1.3×10 -2 Pa ~ 2.7×10 -2 Pa Ion acceleration voltage: 300V ~ 1500V Film formation rate: 0.030 nm / sec ~ 0.300 nm / sec Thickness of Mo layer: 2.3 ± 0.1 nm <Repetition unit of Si layer and Mo layer> Number of repetition units: 30 to 60 (preferably 40 to 50).

[0024] The protective film 12 is a film formed between the multilayer reflective film 11 and the absorbing film 13, and has the function of protecting the multilayer reflective film 11. The protective film 12 protects the multilayer reflective film 11 from an etching gas that forms an opening pattern 13a (FIGS. 2 and 3) in the absorbing film 13. The protective film 12 is not removed during the manufacture of the reflective mask 2, but remains on the multilayer reflective film 11. The protective film 12 does not interfere with the reflection of EUV light by the multilayer reflective film 11, or minimizes a decrease in reflectance.

[0025] The etching gas for forming the opening pattern 13a in the absorbing film 13 may be, for example, an oxygen-based gas, a halogen-based gas, or a mixed gas thereof, and is preferably an oxygen-based gas. The oxygen-based gas is preferably used when the absorbing film 13 contains a ruthenium-based material. Examples of the oxygen-based gas include O2 gas and O3 gas. Examples of the halogen-based gas include chlorine-based gas and fluorine-based gas. The above-mentioned etching gas, particularly the oxygen-based gas, can be used not only during the manufacturing process of the reflective mask, but also for cleaning the surface of the reflective mask during maintenance after the use of the reflective mask has begun.

[0026] The etching selectivity, i.e., the ratio (ER1 / ER2) of the etching rate ER1 of the absorbing film 13 by the etching gas to the etching rate ER2 of the protective film 12 by the etching gas, may be preferably 10 or more, more preferably 30 or more, and also preferably 200 or less, more preferably 100 or less.

[0027] 1 to 3, the protective film 12 has a lower layer 12L and an upper layer 12U. The lower layer 12L is a layer formed in contact with the uppermost surface of the multilayer reflective film 11, and the upper layer 12U is in contact with the lowermost surface of the absorbing film 13. By forming the protective film 12 in this manner with a multi-layer structure, materials having excellent predetermined functions can be used for each layer, and therefore the protective film 12 as a whole can be made multifunctional.

[0028] The upper layer 12U may be a rhodium (Rh)-based material. The rhodium-based material may contain only Rh, or may contain Rh and an element other than Rh. It is preferable that the material contained in the upper layer 12U contains Rh most in at% (atomic %). In addition, the rhodium-based material is preferably one that contains Rh as a main component, that is, the Rh content is 50 at% or more. The Rh content in the rhodium-based material may be preferably 50 at% to 100 at%, more preferably more than 50 at% to 100 at%. Since the upper layer 12U is a rhodium-based material, the protective film 12 can have high etching resistance against etching gas in the etching process of the absorbing film 13 during the manufacture of the reflective mask 2. For example, when the upper layer 12U is a rhodium-based material, a high dry etching resistance, particularly against oxygen-based etching gas, can be obtained compared to when the upper layer 12U is a ruthenium-based material. This makes it possible to prevent the protective film 12 from being scraped off and damage to the multilayer reflective film 11 from occurring when the opening pattern 13a is formed in the absorbing film 13. Furthermore, even when an etching gas, particularly an oxygen-based etching gas, is used to clean the surface of the reflective mask 2 after the reflective mask has started to be used, the etching resistance of the protective film 12 can be increased, and the service life of the reflective mask 2 can be extended.

[0029] Furthermore, by forming upper layer 12U from a rhodium-based material, the resistance of protective film 12 to a sulfuric acid-hydrogen peroxide mixture (SPM cleaning solution) and the like is improved. Therefore, even in a process such as removing the resist film (described later) or cleaning the reflective mask 2, protective film 12 is maintained and damage to multilayer reflective film 11 can be suppressed. Furthermore, by using a rhodium-based material for upper layer 12U, a relatively high reflectance for EUV light can be maintained.

[0030] In addition, when the upper layer 12U contains an element other than Rh, it is preferable that the element other than Rh contains at least one element selected from the group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr, and Ti. Among them, when the element other than Rh contained in the upper layer 12U is at least one selected from the group consisting of N, O, C, and B, it is preferable from the viewpoint of reducing the crystallinity of the upper layer 12U and improving the smoothness. In addition, when the element other than Rh contained in the upper layer 12U contains at least one element selected from the group consisting of Ru, Nb, Mo, Zr, and Ti, it is preferable from the viewpoint of reducing the extinction coefficient k while suppressing an increase in the refractive index n, and improving the reflectance for EUV light.

[0031] When the upper layer 12U contains Rh and an element other than Rh, the element ratio of Rh to the element other than Rh contained in the upper layer 12U may be preferably 50:50 to 99:1, more preferably 70:30 to 95:5. In this specification, the element ratio means a molar ratio. By setting the element ratio of Rh to the element other than Rh in the above range, it is possible to reduce the extinction coefficient k while suppressing an increase in the refractive index n, thereby improving the reflectance to EUV light and suppressing crystallization of the upper layer 12U.

[0032] From the viewpoint of improving resistance to etching gas, it is preferable to use the above-mentioned rhodium-based material as the material for the protective film 12. However, when a layer made of a rhodium-based material is formed directly on the multilayer reflective film 11, mixing may occur between the protective film 12 and the multilayer reflective film 11 depending on the film formation method of each layer, the material of the multilayer reflective film 11, etc. Mixing between layers in the reflective mask blank 1 or the reflective mask 2 can be recognized by analyzing and observing the distribution state of elements by depth analysis using XPS or Rutherford backscattering spectrometry, etc., and can also be visually recognized as disturbance of the interface in electron microscope photographs, etc.

[0033] The present inventors have found that the following is provided between the upper layer 12U of the protective film 12 and the multilayer reflective film 11: k<-0.15n+0.16 (I) It has been found that by providing the lower layer 12L that satisfies the above formula (I) in the EUV range, mixing between the protective film 12 and the multilayer reflective film 11 can be suppressed. That is, it has been found that by providing the lower layer 12L that satisfies the above formula (I) in this embodiment, it is possible to prevent the substance contained in the upper layer 12U from diffusing downward toward the multilayer reflective film 11, and also that the substance contained in the lower layer 12L is unlikely to diffuse into the multilayer reflective film 11. When the multilayer reflective film 11 is a Si / Mo multilayer reflective film, mixing between the protective film 12 and the Si layer that constitutes the uppermost layer of the multilayer reflective film 11 can be suppressed. Mixing between layers leads to a decrease in reflectance and a decrease in durability, but by suppressing mixing between layers with the configuration of this embodiment, the reflectance of the reflective mask 2 for EUV light can be maintained.

[0034] Furthermore, as shown in FIG. 4, a substance (element and / or compound) that satisfies k<-0.15n+0.16 can reduce both the refractive index n and the extinction coefficient k, and therefore the effect of the lower layer 12L itself on the reflectance of EUV light can be reduced.

[0035] The refractive index n and extinction coefficient k of the film or layer may be values ​​in the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or values ​​calculated from the "dependence of the incident angle" of the reflectance below. The incident angle θ of the EUV light, the reflectance R for the EUV light, the refractive index n of the film, and the extinction coefficient k of the film satisfy the following formula (1). R = |(sinθ-((n+ik) 2 -cos 2 θ) 1 / 2 ) / (sinθ+((n+ik) 2 -cos 2 θ) 1 / 2 )|···(1) The refractive index n and extinction coefficient k can be calculated by measuring multiple combinations of the incident angle θ and the reflectance R and fitting the multiple measurement data to minimize the error between the multiple measurement data and equation (1).

[0036] The lower layer 12L preferably contains at least one element selected from the group consisting of Ru, Nb, Mo, Zr, Y, C, and B, and more preferably contains Ru. The lower layer 12L is preferably a ruthenium-based material. The ruthenium-based material may contain only Ru, or may contain Ru and an element other than Ru. The content of Ru in the ruthenium-based material is preferably 50 at% to 100 at%. When the lower layer 12L contains the above-mentioned element, it is possible to further promote the suppression of mixing with the multilayer reflective film 11 and the suppression of a decrease in reflectance.

[0037] The refractive index n of the lower layer 12L is preferably 0.875 to 0.930, more preferably 0.875 to 0.920, even more preferably 0.875 to 0.910, and particularly preferably 0.875 to 0.900. The extinction coefficient k of the lower layer 12L is preferably 0.005 to 0.03.

[0038] The lower layer 12L satisfying the above formula (I) in this embodiment can be prepared, for example, by ion beam sputtering or reactive sputtering. The lower layer 12L prepared by ion beam sputtering becomes a dense film, and can suppress mixing between the protective film 12 and the multilayer reflective film 11 with a thinner film thickness. In addition, when the lower layer 12L is prepared by reactive sputtering, the multilayer reflective film 11 can be inactivated by active plasma species during the formation of the lower layer 12L, and mixing between the protective film 12 and the multilayer reflective film 11 can be suppressed. The gas used in reactive sputtering is preferably one or more of nitrogen, oxygen, CO2, and CH4, and more preferably nitrogen.

[0039] In this manner, in the present embodiment, by forming the protective film 12 from a combination of the upper layer 12U and the lower layer 12L, it is possible to provide a configuration including a protective film 12 that has high resistance to etching gases, particularly oxygen-based etching gases, and that suppresses mixing with the underlying multilayer reflective film 11, thereby maintaining good reflectivity for EUV light.

[0040] The thickness of the upper layer 12U is preferably 0.5 nm to 3.5 nm, more preferably 0.9 nm to 3.0 nm, and even more preferably 1.0 nm to 2.5 nm. By setting the thickness of the upper layer 12U within the above range, the protective function of the multilayer reflective film 11 during the etching process in manufacturing the reflective mask can be sufficiently ensured, and the decrease in the reflectance of the multilayer reflective film 11 can be suppressed. Furthermore, the thickness of the lower layer 12L is preferably 0.4 nm to 2.5 nm, more preferably 0.5 nm to 2.5 nm, and even more preferably 0.5 nm to 1.6 nm. By setting the thickness of the lower layer 12L within the above range, the material of the upper layer 12U can be sufficiently suppressed from diffusing into the multilayer reflective film 11, and the decrease in the reflectance of the multilayer reflective film 11 can also be suppressed. Furthermore, the thickness of the entire protective film 12 is preferably 1.0 nm to 5.0 nm, and more preferably 2.0 nm to 3.5 nm.

[0041] The root mean square roughness (RMS) of the upper surface of the protective film 12 (the surface on which the absorbing film is formed), ie, the upper surface of the upper layer 12U, is preferably 0.3 nm or less, and more preferably 0.1 nm or less.

[0042] The film formation method of the protective film 12 is not particularly limited for both the upper layer 12U and the lower layer 12L. For example, it may be a DC sputtering method, a magnetron sputtering method (hereinafter, may also be referred to as the MS method), an ion beam sputtering method (hereinafter, may also be referred to as the IBD method), or the like. It is preferable that the upper layer 12U and the lower layer 12L are continuously formed without being exposed to the atmosphere during film formation (that is, without opening to the atmosphere). Further, it is more preferable to continuously form the upper layer 12U and the lower layer 12L without opening to the atmosphere from after the formation of the multilayer reflective film 11 until the formation of the upper layer 12U and the lower layer 12L is completed. That is, although it may be opened to the atmosphere once after the formation of the multilayer reflective film 11 is completed, it is more preferable to continuously form the film without opening to the atmosphere from the start of the formation of the multilayer reflective film 11 until the formation of the upper layer 12U of the protective film is completed. By continuously forming the film without being exposed to the atmosphere, the formation of oxides that can cause a decrease in reflectance can be suppressed. Further, it is even more preferable to continuously form the film without opening to the atmosphere from after the formation of the multilayer reflective film 11 until the formation of the upper layer 12U and the lower layer 12L is completed and then until the formation of the absorption film 13 is completed.

[0043] When forming a Rh film as the upper layer 12U using the magnetron sputtering method, an example of the film formation conditions is as follows. <Film formation conditions of Rh film> Target: Rh target Sputtering gas: Ar gas Gas pressure: 0.10 Pa to 0.20 Pa Output density of target: 1.0 W / cm 2 ~2.0 W / cm 2 Film formation rate: 0.02 nm / sec to 0.07 nm / sec Film thickness of Rh film: 0.5 nm to 3.5 nm.

[0044] When forming a Ru film as the lower layer 12L using the ion beam sputtering method, an example of the film formation conditions is as follows. <Film formation conditions of Ru film> Target: Ru target Sputtering gas: Ar gas Gas pressure: 0.010 Pa to 0.020 Pa Deposition rate: 0.01nm / sec~0.10nm / sec Ru film thickness: 0.5nm to 2.5nm.

[0045] 1, the absorbing film 13 in the reflective mask blank 1 is a film in which an aperture pattern 13a is to be formed. That is, in the manufacturing process of the reflective mask 2, the aperture pattern 13a is formed in the absorbing film 13, whereby the reflective mask blank 1 is processed to obtain the reflective mask 2.

[0046] The absorbing film 13 absorbs EUV light. The absorbing film 13 may be a phase shift film, and may not only absorb EUV light but also shift the phase of the second EUV light L2 relative to the first EUV light L1, as shown in FIG. 3. The first EUV light L1 is light that passes through the opening pattern 13a without passing through the absorbing film 13, is reflected by the multilayer reflective film 11, and passes through the opening pattern 13a without passing through the absorbing film 13 again. The second EUV light L2 is light that passes through the absorbing film 13 while being partially absorbed by the absorbing film 13, is reflected by the multilayer reflective film 11, and passes through the absorbing film 13 while being partially absorbed by the absorbing film 13 again.

[0047] The phase difference (≧0) between the first EUV light L1 and the second EUV light L2 is, for example, 170° to 250°. The phase of the first EUV light L1 may be ahead of or behind the phase of the second EUV light L2. The phase shift film can improve the contrast of the transferred image by utilizing the interference between the first EUV light L1 and the second EUV light L2. The transferred image is an image obtained by transferring the opening pattern 13a of the absorbing film 13 onto the target substrate.

[0048] In EUVL, a so-called projection effect (shadowing effect) occurs. The shadowing effect refers to a region in which the sidewall of the opening pattern 13a blocks the EUV light due to the incident angle θ of the EUV light being not 0° (for example, 6°), resulting in a positional or dimensional shift of the transferred image. In order to reduce the shadowing effect, it is effective to lower the sidewall of the opening pattern 13a and to thin the absorbing film 13.

[0049] The thickness of the absorbing film 13 is, for example, 60 nm or less, and preferably 50 nm or less, in order to reduce the shadowing effect, while it is preferably 20 nm or more, and more preferably 30 nm or more, in order to ensure the phase difference between the first EUV light L1 and the second EUV light L2.

[0050] The absorbing film 13 is not particularly limited, but preferably contains at least one metal element selected from the group consisting of Ru, Ir, Pt, Pd, Au, Ta, and Cr. The above metal elements have a relatively small refractive index (FIG. 4), so the thickness of the absorbing film (phase shift film) 13 can be reduced. This makes it possible to reduce the above-mentioned shadowing effect while ensuring the phase difference between the first EUV light L1 and the second EUV light L2. Among the above metal elements, the absorbing film 13 preferably contains Ru. Even if the absorbing film 13 contains Ru in this way, in this embodiment, since the upper layer 12U of the protective film 12 contains a rhodium-based material as described above, a good etching selectivity between the absorbing film 13 and the protective film 12, particularly a good etching selectivity to oxygen-based gas, can be obtained. The absorbing film 13 may have a two-layer structure of an absorbing film lower layer and an absorbing film upper layer. The absorbing film lower layer is a layer formed in contact with the uppermost surface of the protective film 12. The two-layer structure makes it possible to adjust the phase difference between the first EUV light L1 and the second EUV light L2. From the viewpoint of processing characteristics, it is preferable that the absorbing layer 13 contains Ta in the lower absorbing film layer and Ru in the upper absorbing film layer, or that the lower absorbing film layer contains Ru and the upper absorbing film layer contains Ir.

[0051] The absorbing film 13 may further contain at least one nonmetallic element selected from N, O, B, and C in addition to the above metal elements. By containing the above nonmetallic elements, crystallization of the absorbing film 13 can be suppressed, and roughness of the sidewall of the opening pattern 13a can be reduced. The nonmetallic element preferably contains at least oxygen, and more preferably contains oxygen and nitrogen. When the absorbing film 13 further contains a nonmetallic element in addition to a metal element, the absorbing film 13 may be a RuN film, a TaN film, a RuTaON film, a TaON film, or the like.

[0052] The method for forming the absorption film 13 may be a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, a reactive sputtering method, or the like.

[0053] When forming a RuTaON film as the absorption film 13 using the reactive sputtering method, an example of the film formation conditions is as follows. <Film formation conditions of RuTaON film> Target: Ru target and Ta target Output density of Ru target: 8.8 W / cm 2 Output density of Ra target: 0.41 W / cm 2 Sputtering gas: Mixed gas of Ar gas, O2 gas, and N2 gas Volume ratio of O2 gas in the sputtering gas (O2 / (Ar + O2 + N2)): 0.06 Volume ratio of N2 gas in the sputtering gas (N2 / (Ar + O2 + N2)): 0.21.

[0054] The etching mask film 14 is formed on the absorption film 13 and is used to form the opening pattern 13a in the absorption film 13. A resist film (not shown) is provided on the etching mask film 14. In the manufacturing process of the reflective mask 2, first, a first opening pattern is formed in the resist film, then a second opening pattern is formed in the etching mask film 14 using the first opening pattern, and then a third opening pattern 13a is formed in the absorption film 13 using the second opening pattern. The first opening pattern, the second opening pattern, and the third opening pattern 13a have the same dimensions and the same shape in a plan view (viewed in the Z-axis direction). The etching mask film 14 enables thinning of the resist film.

[0055] The etching mask film 14 preferably contains at least one element selected from the group consisting of Al, Hf, Y, Cr, Nb, Ti, Mo, Ta, and Si. The etching mask film 14 may contain at least one element selected from the group consisting of O, N, and B in addition to the above elements.

[0056] The thickness of the etching mask film 14 is preferably 2 nm to 30 nm, more preferably 2 nm to 25 nm, and further preferably 2 nm to 10 nm. The method for forming the etching mask film 14 is, for example, a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like.

[0057] Furthermore, one embodiment of the present disclosure may be a method for producing a reflective mask blank, comprising forming a multilayer reflective film that reflects EUV light, forming a protective film that protects the multilayer reflective film, and forming an absorbing film that absorbs the EUV light, on a substrate, wherein the formation of the protective film comprises forming (i) a lower layer that satisfies k<-0.15n+0.16 in the EUV range, where n is the refractive index and k is the extinction coefficient, and (ii) an upper layer made of a rhodium-based material containing Rh, or Rh and at least one element selected from the group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr, and Ti.

[0058] A method for manufacturing a reflective mask blank 1 according to one embodiment will be described with reference to Fig. 5. The method for manufacturing the reflective mask blank 1 includes, for example, steps S101 to S105 shown in Fig. 5. In step S101, a substrate 10 is prepared. In step S102, a multilayer reflective film 11 is formed on a first main surface 10a of the substrate 10. In step S103, a protective film 12 is formed on the multilayer reflective film 11. In step S104, an absorbing film 13 is formed on the protective film 12. In step S105, an etching mask film 14 is formed on the absorbing film 13.

[0059] The method for manufacturing the reflective mask blank 1 only needs to include at least steps S101 to S104. The method for manufacturing the reflective mask blank 1 may further include a step of forming a functional film not shown in FIG.

[0060] Furthermore, one aspect of the present disclosure may be a method for manufacturing a reflective mask, including preparing a reflective mask blank and forming an opening pattern in an absorbing film in the reflective mask blank.

[0061] A method for manufacturing a reflective mask 2 according to an embodiment will be described with reference to FIG. 6. The method for manufacturing a reflective mask 2 includes steps S201 to S204 shown in FIG. 6. In step S201, a reflective mask blank 1 is prepared. In step S202, an etching mask film 14 is processed. A resist film (not shown) is provided on the etching mask film 14. First, a first opening pattern is formed in the resist film, and then a second opening pattern is formed in the etching mask film 14 using the first opening pattern. In step S203, a third opening pattern 13a is formed in the absorbing film 13 using the second opening pattern. In step S203, the absorbing film 13 is etched using an etching gas. In step S204, the resist film and the etching mask film 14 are removed. For example, a sulfuric acid-hydrogen peroxide mixture is used to remove the resist film. For example, an etching gas is used to remove the etching mask film 14. The etching gas used in step S204 (removing the etching mask film 14) may be the same as the etching gas used in step S203 (forming the opening pattern 13a). The manufacturing method of the reflective mask 2 only needs to include at least steps S201 and S203. EXAMPLES

[0062] Experimental data will be described below. The following Examples 1, 2, and 6 to 13 are working examples, and Examples 3 to 5 are comparative examples. Film formation conditions and measurement results for the working examples and comparative examples are summarized in Table 1. Examples 14 and 15 are also shown as reference examples.

[0063] [Table 1]

[0064] (Example 1) A reflective mask blank including a substrate, a multilayer reflective film, a protective film, and an absorbing film was prepared. A SiO2-TiO2-based glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared as the substrate. This glass substrate had a thermal expansion coefficient of 0.02×10 at 20°C. -7 / °C, Young's modulus is 67 GPa, Poisson's ratio is 0.17, and specific stiffness is 3.07 × 10 7 m 2 / s 2 The quality assurance area of ​​the front surface (top surface) of the substrate was polished to a root mean square roughness (RMS) of 0.15 nm or less and a flatness of 100 nm or less. A 100 nm thick Cr film was formed on the back surface (bottom surface) of the substrate using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / □.

[0065] A Mo / Si multilayer reflective film was formed as the multilayer reflective film. The Mo / Si multilayer reflective film was formed by fixing the obtained substrate to a flat electrostatic chuck so that the Cr film on the back side faces the substrate, and repeating the formation of a Si layer (thickness 4.5 nm) and a Mo layer (thickness 2.3 nm) on the surface of the substrate by ion beam sputtering 40 times. The total thickness of the Mo / Si multilayer reflective film was 272 nm ((4.5 nm + 2.3 nm) × 40).

[0066] Furthermore, a protective film consisting of a lower Ru film and an upper Rh film was formed on the Si layer, which was the top layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.0 nm) was formed as the lower layer of the protective film using ion beam sputtering, and a Rh film (thickness 1.0 nm) was formed on the Ru film as the upper layer using magnetron sputtering. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). In this example, the lower Ru film was once exposed to the atmosphere after the formation of the lower Ru film.

[0067] After forming the protective film, the reflectance of EUV light (the reflectance of the first EUV light L1 shown in FIG. 3) was measured and found to be a maximum of 65.1%.

[0068] Next, a Ru film, a TaN film, and a TaON film were formed in this order from bottom to top on the protective film as an absorbing film. The Ru film was formed by DC sputtering, and the TaN film and the TaON film were formed by reactive sputtering. The cross section of the obtained reflective mask blank cut along the thickness direction (Z direction) was subjected to elemental analysis and shape observation using a TEM equipped with an energy dispersive X-ray analyzer. Figure 7(a) shows a dark field image of the cross section of the part including the protective film, and Figure 7(b) shows an element mapping image detected for the main elements. In Figure 7(b), the positions of each image in the thickness direction are aligned with each other. In Figure 7(b), the concentration of each element is expressed in grayscale. The brighter the color, the higher the concentration of each element. The same is true for Figures 8(b) and 9(b).

[0069] (Example 2) A reflective mask blank was produced in the same manner as in Example 1, except for the deposition conditions of the protective film. In Example 2, a two-layer protective film having a lower layer of Nb film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Nb film (thickness 0.5 nm) was formed as the lower layer of the protective film by magnetron sputtering, and a Rh film (thickness 2.5 nm) was formed as the upper layer on the Nb film. The Nb used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). After the deposition of the Si / Mo multilayer reflective film, the film was opened to the atmosphere, and the deposition of the lower layer of Nb film and the upper layer of Rh film was completed without opening to the atmosphere.

[0070] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.0% at maximum.

[0071] Furthermore, a reflective mask blank was produced by forming an Ru film, a TaN film, and a TaON film in this order from bottom to top as absorbing films on the protective film in the same manner as in Example 1. A cross section in the thickness direction (Z direction) of the portion including the protective film of the obtained reflective mask blank was analyzed and observed in the same manner as in Example 1. The observation results are shown in Figures 8(a) and (b).

[0072] (Example 3) In Example 3, a protective film was formed by depositing a Rh film (film thickness 2.5 nm) by magnetron sputtering on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film formed in the same manner as in Example 1.

[0073] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 63.9% at maximum.

[0074] Furthermore, a Ru film was formed as an absorbing film on the protective film by DC sputtering to produce a reflective mask blank. In the same manner as in Example 1, the cross section of the obtained reflective mask blank in the thickness direction (Z direction) of the part including the protective film was analyzed and observed. The observation results are shown in Figures 9(a) and (b).

[0075] As described above, the reflectance of EUV light measured after forming the protective film was a maximum of 65.1% (Example 1) and 65.0% (Example 2) for the configuration in which a protective film was formed consisting of an upper layer made of a Rh film and a lower layer containing a material that satisfied k<-0.15n+0.16, whereas it decreased to 63.9% for the configuration having a protective film made of a single layer of Rh film (Example 3).

[0076] Also, from Figures 7 to 9, the interface between the protective film and the topmost Si film of the Mo / Si multilayer reflective film was flat in Examples 1 and 2 (Figures 7(a) and 8(a)), but disturbance was observed at the interface in Example 3 (Figure 9(a)), indicating the occurrence of mixing. Furthermore, in Examples 1 and 2, it was found that the distribution ranges of Rh and Si hardly overlapped, indicating that the diffusion of Rh was suppressed (Figures 7(b) and 8(b)). In Example 3, the distribution ranges of Rh and Si overlapped, indicating that mixing between Rh and Si occurred (Figure 9(b)).

[0077] (Example 4) A reflective mask blank was fabricated in the same manner as in Example 1, except for the deposition conditions of the protective film. In Example 4, a two-layer protective film having a lower layer of Ta film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ta film (thickness 0.9 nm) was formed as the lower layer of the protective film by magnetron sputtering, and an Rh film (thickness 2.3 nm) was formed as the upper layer on the Ta film. The Ta used for the lower layer is a material that does not satisfy k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). After the deposition of the Si / Mo multilayer reflective film, the system was opened to the atmosphere, and the deposition of the lower layer of Ta film and the upper layer of Rh film was completed without opening to the atmosphere.

[0078] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be a maximum of 63.5%.

[0079] (Example 5) A reflective mask blank was fabricated in the same manner as in Example 4, except for the thickness of the lower layer of the Ta film. In Example 5, a two-layer protective film having a lower layer of a Ta film and an upper layer of a Rh film was formed on the Si layer, which was the top layer of the Si / Mo multilayer reflective film. More specifically, a Ta film (thickness 1.3 nm) was formed as the lower layer of the protective film using a magnetron sputtering method, and a Rh film (thickness 2.4 nm) was formed as the upper layer on the Ta film using an ion beam sputtering method. The Ta used for the lower layer is a material that does not satisfy k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). After the formation of the Si / Mo multilayer reflective film, the film was opened to the atmosphere, and the film formation was continued without opening to the atmosphere from the formation of the Si / Mo multilayer reflective film until the formation of the lower layer of the Ta film and the upper layer of the Rh film was completed.

[0080] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 61.7% at maximum.

[0081] (Example 6) A reflective mask blank was produced in the same manner as in Example 1, except for the deposition conditions of the protective film. In Example 6, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 0.9 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.6 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously deposited without being exposed to the atmosphere from the start of deposition of the Si / Mo multilayer reflective film to the completion of deposition of the lower layer of Ru film and the upper layer of Rh film.

[0082] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.8% at maximum.

[0083] (Example 7) A reflective mask blank was fabricated in the same manner as in Example 6, except for the thickness of the protective film. In Example 7, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 0.9 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.8 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of Ru film and the upper layer of Rh film.

[0084] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.7% at maximum.

[0085] (Example 8) A reflective mask blank was fabricated in the same manner as in Example 6, except for the thickness of the protective film. In Example 8, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 0.9 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 2.0 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of Ru film and the upper layer of Rh film.

[0086] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.3% at maximum.

[0087] (Example 9) A reflective mask blank was prepared in the same manner as in Example 6, except for the thickness of the protective film. In Example 9, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.1 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.6 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of Ru film and the upper layer of Rh film.

[0088] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.7% at maximum.

[0089] (Example 10) A reflective mask blank was prepared in the same manner as in Example 6, except for the thickness of the protective film. In Example 10, a protective film having a two-layer structure, a lower layer of a Ru film and an upper layer of a Rh film, was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.1 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.8 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of the Ru film and the upper layer of the Rh film.

[0090] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.5% at maximum.

[0091] (Example 11) A reflective mask blank was fabricated in the same manner as in Example 6, except for the thickness of the protective film. In Example 11, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.1 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 2.0 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of Ru film and the upper layer of Rh film.

[0092] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.0% at maximum.

[0093] (Example 12) A reflective mask blank was prepared in the same manner as in Example 6, except for the thickness of the protective film. In Example 12, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.6 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.6 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of Ru film and the upper layer of Rh film.

[0094] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.3% at maximum.

[0095] (Example 13) A reflective mask blank was prepared in the same manner as in Example 6, except for the thickness of the protective film. In Example 12, a protective film having a two-layer structure, a lower layer of a Ru film and an upper layer of a Rh film, was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film. More specifically, a Ru film (thickness 1.6 nm) was formed as the lower layer of the protective film by using an ion beam sputtering method, and a Rh film (thickness 1.8 nm) was formed as the upper layer on the Ru film by using an ion beam sputtering method. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). The films were continuously formed without being exposed to the atmosphere from the start of the formation of the Si / Mo multilayer reflective film to the completion of the formation of the lower layer of the Ru film and the upper layer of the Rh film.

[0096] After forming the protective film, the reflectance of EUV light was measured in the same manner as in Example 1, and was found to be 65.0% at maximum.

[0097] (Example 14) In Example 14, a two-layer protective film having a lower Ru film and an upper Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film formed in the same manner as in Example 1. More specifically, a Ru film (thickness 0.9 nm) was formed as the lower layer of the protective film using ion beam sputtering, and a Rh film (thickness 1.6 nm) was formed as the upper layer on the Ru film using magnetron sputtering. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). In this example, the lower layer of the Ru film was once exposed to the atmosphere after the formation of the lower layer.

[0098] Furthermore, a RuN film, a TaN film, and a TaON film were formed in this order on the protective film as absorbing films, to prepare a reflective mask blank. All of the absorbing films were formed by reactive sputtering.

[0099] (Example 15) In Example 15, a two-layer protective film having a lower layer of Ru film and an upper layer of Rh film was formed on the Si layer, which was the uppermost layer of the Si / Mo multilayer reflective film formed in the same manner as in Example 1. More specifically, a Ru film (thickness 0.9 nm) was formed as the lower layer of the protective film using ion beam sputtering, and a Rh film (thickness 1.6 nm) was formed as the upper layer on the Ru film using magnetron sputtering. The Ru used for the lower layer is a material that satisfies k<-0.15n+0.16 (n=refractive index; k=extinction coefficient) (Figure 4). In this example, the lower layer of the Ru film was once exposed to the atmosphere after the formation of the lower layer.

[0100] Furthermore, a TaON film and a RuTaON film were formed in this order as absorbing films on the protective film to prepare a reflective mask blank. All of the absorbing films were formed by reactive sputtering.

[0101] The reflective mask blank, the reflective mask, the manufacturing method of the reflective mask blank, and the manufacturing method of the reflective mask according to the present disclosure have been described above, but the present disclosure is not limited to the above-mentioned embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure.

[0102] This application claims priority based on Patent Application No. 2021-214753 filed with the Japan Patent Office on December 28, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0103] 1 Reflective mask blank 2 Reflective mask 10 Substrate 11 Multilayer reflective film 12 Protective film 12L Lower layer of protective film 12U Upper layer of protective film 13 Absorbing membrane 13a Opening pattern 14 Etching mask film

Claims

1. A reflective mask blank for EUV lithography comprising, in this order from bottom to top, a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and an absorbing film that absorbs the EUV light, The protective film is an upper layer made of a rhodium-based material containing 50 to 100 atomic % Rh; and a lower layer containing at least one element selected from the group consisting of Ru, Nb, Mo, Zr, Y, C, and B.

2. 2. The reflective mask blank according to claim 1, wherein the upper layer contains Rh and at least one element selected from the group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr and Ti.

3. The lower layer has a structure represented by the following formula (I) in the EUV region: k<-0.15n+0.16...(I) 3. The reflective mask blank according to claim 1 or 2, which satisfies the formula: wherein n is a refractive index, and k is an extinction coefficient.

4. 3. The reflective mask blank according to claim 1, wherein the lower layer has a refractive index n of 0.930 or less and an extinction coefficient k of 0.005 or more.

5. The reflective mask blank according to claim 1 , wherein the lower layer contains at least one element selected from the group consisting of Ru and Nb.

6. The reflective mask blank according to claim 1 , wherein the lower layer contains Ru.

7. The thickness of the upper layer is 0.5 nm or more and 3.5 nm or less, 3. The reflective mask blank according to claim 1, wherein the thickness of the lower layer is 0.4 nm or more and 2.5 nm or less.

8. 3. The reflective mask blank according to claim 2, wherein the upper layer has an element ratio of Rh to elements other than Rh of 50:50 to 99:

1.

9. 3. The reflective mask blank according to claim 1, wherein the lower layer contains 50 to 100 atomic % of Ru.

10. The reflective mask blank according to claim 1 or 2, wherein the upper layer has a root mean square roughness (RMS) of 0.3 nm or less.

11. 3. The reflective mask blank according to claim 1, wherein the absorbing film contains at least one element selected from the group consisting of Ru, Ir, Pt, Pd, Au, Ta and Cr.

12. The reflective mask blank according to claim 1 , wherein the absorbing film contains at least one element selected from the group consisting of Ru, Ir, Ta and Cr.

13. The reflective mask blank according to claim 11 or 12, wherein the absorbing film contains at least one nonmetallic element selected from N, O, B and C.

14. an etching mask film on the absorbing film; 3. The reflective mask blank according to claim 1, wherein the etching mask film contains at least one element selected from the group consisting of Al, Hf, Y, Cr, Nb, Ti, Mo, Ta and Si.

15. A reflective mask, comprising the reflective mask blank according to claim 1 or 2, and a pattern formed in the absorbing film.

16. On the board, forming a multilayer reflective film that reflects EUV light; forming a protective film for protecting the multilayer reflective film; forming an absorbing film that absorbs the EUV light; The formation of the protective film (i) an underlayer comprising at least one element selected from the group consisting of Ru, Nb, Mo, Zr, Y, C, and B; (ii) forming an upper layer made of a rhodium-based material containing 50 to 100 atomic % of Rh.

17. The method for producing a reflective mask blank according to claim 16 , wherein the layers are continuously formed without being exposed to the atmosphere from the start of formation of the lower layer of the protective film to the completion of formation of the upper layer of the protective film.

18. The method for producing a reflective mask blank according to claim 17 , wherein the multilayer reflective film is continuously formed without being exposed to the atmosphere from the start of formation of the multilayer reflective film to the completion of formation of the lower layer and the upper layer of the protective film.

19. 19. The method for producing a reflective mask blank according to claim 17, wherein the lower layer and the upper layer of the protective film are formed by magnetron sputtering or ion beam sputtering.

20. 19. The method for producing a reflective mask blank according to claim 18, wherein the multilayer reflective film and the lower layer and the upper layer of the protective film are each formed by using a magnetron sputtering method or an ion beam sputtering method.

21. A reflective mask blank is prepared by using the manufacturing method according to claim 16, forming an aperture pattern in the absorbing film.

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