Reflective mask blank, method for producing reflective mask blank, reflective mask, and method for producing reflective mask

Abstract

Provided are: a reflective mask blank having an absorber film excellent in SPM resistance; and a method for producing the reflective mask blank.　A reflective mask blank according to the present invention has a substrate, a multilayer reflective film that reflects EUV light, and an absorber film in this order, wherein: the absorber film contains ruthenium and tungsten; the tungsten content is 50 atom% or greater with respect to all atoms of the absorber film; in an XRD chart obtained by performing in-plane XRD measurement, among diffraction peaks that are derived from the absorber film and in which 2θ is observed in the range of 37-42°, 2θ of the peak having the highest intensity is 40.0° or greater; and the surface roughness of the surface of the absorber film is 0.45 nm or less.

Description

Reflective mask blank, method for manufacturing a reflective mask blank, reflective mask, method for manufacturing a reflective mask

[0001] This invention relates to a reflective mask used in EUV (Extreme Ultra Violet) exposure, which is used in the exposure process of semiconductor manufacturing, and a method for manufacturing the same, as well as a reflective mask blank, which is the original plate for the reflective mask, and a method for manufacturing the same.

[0002] In recent years, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been investigated for further miniaturization of semiconductor devices.

[0003] In EUV lithography, reflective optics and reflective masks are used due to the characteristics of EUV light. In a reflective mask, a multilayer reflective film that reflects EUV light is formed on the substrate, and an absorber film that absorbs EUV light is patterned on the multilayer reflective film.

[0004] EUV light incident on a reflective mask from the illumination optical system of an exposure apparatus is reflected in areas without an absorber film (apertures) and absorbed in areas with an absorber film (non-apertures). As a result, the mask pattern is transferred onto the wafer as a resist pattern through the reduction projection optical system of the exposure apparatus, and subsequent processing is carried out. As a material used for the absorber film, for example, Patent Document 1 discloses a material containing ruthenium (Ru) and tungsten (W).

[0005] International Publication No. 2022 / 118762

[0006] When patterning a reflective mask blank for use as a mask, sulfuric acid peroxide (SPM) is sometimes used as a processing solution during mask manufacturing, and the absorbent membrane is required to have excellent SPM resistance. In the above-mentioned literature, an absorbent membrane containing Ru and W is disclosed, but the inventors have found that increasing the W content in the absorbent membrane from the standpoint of optical properties may result in SPM resistance not meeting the standards required today, indicating room for improvement.

[0007] The present invention has been made in view of the above problems and aims to provide a reflective mask blank having an absorbent membrane with excellent SPM resistance and a method for manufacturing a reflective mask blank. The present invention also aims to provide a reflective mask and a method for manufacturing a reflective mask.

[0008] As a result of diligent research into the above-mentioned problems, the present inventors have found that when using an absorber film containing ruthenium and tungsten, with a tungsten content of 50 atomic percent or more, the absorber film having a 2θ of 40.0° or higher for the highest intensity peak in the diffraction peaks originating from the absorber film observed in the range of 37 to 42° by X-ray diffraction, and having a surface roughness of 0.45 nm or less, exhibits excellent SPM resistance, leading to the present invention.

[0009] In other words, the present inventors have found that the above problems can be solved by the following configurations: [1] A reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, and an absorber film in this order, wherein the absorber film contains ruthenium and tungsten, the tungsten content is 50 atomic percent or more with respect to the total atoms of the absorber film, in an XRD chart obtained by performing an in-plane XRD measurement, the 2θ of the peak with the highest intensity among the diffraction peaks originating from the absorber film observed in the range of 2θ to 42° is 40.0° or more, and the surface roughness of the surface of the absorber film is 0.45 nm or less. [2] The reflective mask blank according to [1], wherein the absorber film has an oxide layer on the surface opposite to the multilayer reflective film side, and the thickness of the oxide layer is 2.0 nm or less. [3] The reflective mask blank according to [2], wherein the ratio of the thickness of the oxide layer to the thickness of the absorber film is 0.050 or less. [4] The reflective mask blank according to any one of [1] to [3], wherein the tungsten content is 55 to 80 atomic percent with respect to the total atoms of the absorber film. [5] The reflective mask blank according to any one of [1] to [4], wherein the ruthenium content is 20 to 45 atomic percent with respect to the total atoms of the absorber film. [6] The tungsten content with respect to the total atoms of the absorber film is A Ｗ (Atomic %), and the amount of ruthenium relative to the total atoms of the absorber membrane is A Ｒｕ (When expressed as atomic %), A Ｗ / A Ｒｕ[1] to [5], wherein the ratio is 2.00 to 4.00. [7] A reflective mask blank according to any one of [1] to [6], wherein a protective film is provided between the multilayer reflective film and the absorber film, and the protective film contains rhodium. [8] A method for manufacturing a reflective mask blank comprising, in this order, a substrate, a multilayer reflective film that reflects EUV light, and an absorber film containing ruthenium and tungsten, wherein the tungsten content is 50 atomic percent or more with respect to the total atoms of the absorber film, the absorber film is formed in a vacuum chamber, and the pressure in the vacuum chamber when forming the absorber film is 0.10 Pa or more and less than 0.15 Pa. [9] A reflective mask having an absorber film pattern formed by patterning the absorber film of the reflective mask blank according to any one of [1] to [7].

[10] A method for manufacturing a reflective mask, comprising the step of patterning the absorbent membrane of the reflective mask blank described in any of [1] to [7] to form an absorbent membrane pattern.

[0010] According to the present invention, a reflective mask blank having an absorbent membrane with excellent SPM resistance and a method for manufacturing a reflective mask blank can be provided. Furthermore, according to the present invention, a reflective mask and a method for manufacturing a reflective mask can also be provided.

[0011] This is a schematic cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. This is a schematic cross-sectional view showing an example of a manufacturing process for a reflective mask using the reflective mask blank of the present invention.

[0012] The meanings of the terms in the present invention are as follows. A numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the present specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, hafnium, tantalum, tungsten, iridium, tin, vanadium, silver, nickel, cobalt, and platinum may be represented by their corresponding element symbols (such as B, C, N, O, Si, Ti, Cr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Ir, Sn, V, Ag, Ni, Co, and Pt, etc.). Also, in the present specification, silicon (Si) is included in metal elements.

[0013] <Reflective mask blank> The reflective mask blank of the present invention is a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light (hereinafter, also simply referred to as "multilayer reflective film"), and an absorber film in this order, wherein the absorber film contains Ru and W. Also, in the reflective mask blank of the present invention, the content of W is 50 atomic% or more with respect to all atoms of the absorber film. Also, in the reflective mask blank of the present invention, among the diffraction peaks derived from the absorber film observed in the XRD chart obtained by performing In-plane XRD measurement, the 2θ of the peak with the highest intensity is 40.0° or more in the range of 2θ being 37 to 42°. Also, in the reflective mask blank of the present invention, the surface roughness of the surface of the absorber film is 0.45 nm or less.

[0014] The reflective mask blank of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. The reflective mask blank 10 shown in FIG. 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in this order. Note that the reflective mask blank 10 shown in FIG. 1 may have a hard mask film, which will be described later, on the side opposite to the substrate 12 side of the absorber film 18. Also, the reflective mask blank 10 shown in FIG. 1 may have a conductive film, which will be described later, on the side opposite to the multilayer reflective film 14 side of the substrate 12. The reflective mask blank 10 shown in FIG. 1 has a protective film 16, but the protective film 16 may be omitted.

[0015] The absorber film in the reflective mask blank of the present invention is excellent in SPM resistance. Although the details of the reason are unknown, the present inventor speculates as follows. When an absorber film containing ruthenium and tungsten and having a tungsten content of 50 atomic% or more is used, in the diffraction peak derived from the absorber film observed in the range of 2θ of 37 to 42° by X-ray diffraction method, a peak of 40.0° or more appears, so it is presumed that an oxide layer of W is less likely to occur on the surface of the absorber film (the surface opposite to the multilayer reflective film side). Since the formation of an oxide layer of W with low SPM resistance is less likely to occur, the SPM resistance of the absorber film is considered to be improved. Also, if the surface roughness of the surface of the absorber film is within the above range, the surface area of the absorber film in contact with SPM becomes small, so the SPM resistance of the absorber film is considered to be improved. It is presumed that an absorber film excellent in SPM resistance can be obtained by these synergistic effects.

[0016] Hereinafter, the configuration of the reflective mask blank of the present invention will be described in detail.

[0017] [Substrate] The substrate of the reflective mask blank of the present invention preferably has a small coefficient of thermal expansion. If the coefficient of thermal expansion of the substrate is small, distortion of the absorber film pattern due to heat during exposure with EUV light can be suppressed. The coefficient of thermal expansion of the substrate is preferably 0 ± 1.0×10 －７ / °C at 20°C, and 0 ± 0.3×10 －７ / °C is more preferable. As a material having a small coefficient of thermal expansion, SiO ２ -TiO ２ -based glass and the like can be mentioned, but it is not limited thereto, and crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, and substrates such as metals can also be used. SiO ２ -TiO ２ -based glass preferably uses quartz glass containing 90 to 95% by mass of SiO ２ and 5 to 10% by mass of TiO ２ . When the content of TiO ２ is 5 to 10% by mass, the linear expansion coefficient near room temperature is substantially zero, and almost no dimensional change occurs near room temperature. Note that SiO ２ -TiO ２ -based glass may contain trace components other than SiO ２ and TiO ２ .

[0018] The side of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first main surface") preferably has high surface smoothness. The surface smoothness of the first main surface can be evaluated by its surface roughness. The surface roughness of the first main surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. Surface roughness can be measured with an atomic force microscope, and surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to have a predetermined flatness, in terms of excellent pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. Specifically, the substrate preferably has a flatness of 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less in a predetermined area of ​​the first main surface (for example, an area of ​​132 mm × 132 mm). Flatness can be measured with a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate can be appropriately determined by the design of the mask, etc. Examples of substrate dimensions include an outer diameter of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm). Substrates are often rectangular or square in shape. It is preferable that the substrate has high rigidity to prevent deformation due to film stress in the films (multilayer reflective films and absorber films, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0019] [Multilayer Reflective Film] The multilayer reflective film of the reflective mask blank of the present invention is not particularly limited as long as it has the desired properties as a reflective film for an EUV mask blank. The multilayer reflective film preferably has a high reflectivity of EUV light. Specifically, the maximum reflectivity of EUV light around a wavelength of 13.5 nm when EUV light is incident on the multilayer reflective film at an incident angle of 6° is preferably 60% or more, and more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0020] Multilayer reflective films typically utilize alternating layers of high refractive index (FRF) layers and low refractive index (DRF) layers, which exhibit a high refractive index for EUV light, multiple times, as they can achieve high reflectivity for EUV light. The multilayer reflective film may be constructed by stacking layers in this order from the substrate side, forming one period of stacking, or by stacking layers in this order from the substrate side, forming one period of stacking, forming one period of stacking. A layer containing Si can be used as the FRF layer. Si-containing materials include pure Si and Si compounds containing Si and at least one element selected from the group consisting of B, C, N, and O. Using a FRF layer containing Si provides a reflective mask with high reflectivity for EUV light. A layer containing at least one metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof, can be used as the DRF layer. Si is widely used for the FRF layer, and Mo is widely used for the DRF layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to this, and Ru / Si multilayer reflective films, Mo / Be multilayer reflective films, Mo compound / Si compound multilayer reflective films, Si / Mo / Ru multilayer reflective films, Si / Mo / Ru / Mo multilayer reflective films, Si / Ru / Mo multilayer reflective films, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0021] The film thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layer can be appropriately selected according to the materials used and the required EUV light reflectance of the multilayer reflective film. Taking a Mo / Si multilayer reflective film as an example, in order to obtain a multilayer reflective film with a maximum EUV light reflectance of 60% or more, a Mo film with a film thickness of 2.3 ± 0.1 nm and a Si film with a film thickness of 4.5 ± 0.1 nm should be stacked so that the number of repeating units is between 30 and 60. The reflectance of the multilayer reflective film for EUV light with an incident angle θ of 6° is preferably 60% or more, and more preferably 65% ​​or more.

[0022] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when fabricating a multilayer reflective film using ion beam sputtering, ion particles are supplied from an ion source to a target made of a high refractive index material and a target made of a low refractive index material. If the multilayer reflective film is a Mo / Si multilayer reflective film, for example, it can be fabricated by ion beam sputtering in the following way: First, a Si layer of a predetermined thickness is deposited on a substrate using a Si target. Then, a Mo layer of a predetermined thickness is deposited using a Mo target. These Si and Mo layers are stacked for, for example, 30 to 60 periods (preferably 40 to 50 periods) to form a Mo / Si multilayer reflective film.

[0023] [Protective Film] The reflective mask blank of the present invention may have a protective film between the multilayer reflective film and the absorber film. The protective film is provided to protect the multilayer reflective film from damage during the etching process (usually a dry etching process) when a pattern is formed on the absorber film by the etching process. It is also preferable that the protective film protects the multilayer reflective film when the hard mask film described later is removed.

[0024] The protective film preferably contains at least one element selected from the group consisting of Si, Ru, and Rh. The protective film may also preferably contain Rh. If the protective film contains Rh, the Rh content is preferably 50 atomic percent or more relative to the total atoms of the protective film. Specific examples of protective film materials include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Rh, Pd, Ta, and Ir, elemental Rh metal, and Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Ru, Pd, Ta, and Ir. Adding Ru, Nb, Mo, Zr, Y, or Ti to Rh can suppress the increase in refractive index while reducing the extinction coefficient, making it easier to increase the reflectivity of EUV light. Furthermore, adding Ta, Ir, Pd, or Y to Rh tends to improve resistance to etching processes. Suitable materials for the protective film include elemental Al metal, nitrides containing Al and N, and Al ２ O ３ Other materials can also be used. Among these, Ru metal alone, Ru alloy, Rh metal alone, or Rh alloy are preferred as the material for the protective film.

[0025] The protective film may contain at least one element selected from the group consisting of B, C, N, and O.

[0026] The types and content of elements contained in the protective film are obtained by X-ray photoelectron spectroscopy (XPS). When measuring the types and content of elements in the protective film using XPS, the layer on the opposite side of the protective film from the substrate side is removed by sputtering or other means before measurement. The detailed XPS measurement method can be the same as that used for the absorber film in the subsequent step.

[0027] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In terms of maintaining the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 10.0 nm or less, more preferably 6.0 nm or less, even more preferably 5.0 nm or less, and particularly preferably 3.5 nm or less. Furthermore, in terms of etching resistance, the thickness of the protective film is preferably 1.0 nm or more, more preferably 1.5 nm or more, and even more preferably 2.0 nm or more. In particular, it is preferable that the material of the protective film is elemental Ru metal, Ru alloy, elemental Rh metal, or Rh alloy, and that the thickness of the protective film satisfies the above preferred range. The thickness of the protective film is determined by X-ray reflectivity (XRR). Rigaku's Smart Lab HTP is used for XRR measurement. CuKα rays will be used as the X-ray source, with a tube voltage of 40 kV and a tube current of 30 mA. The accompanying software (GlobalFit) will be used for the analysis.

[0028] The protective film may be a single layer or a multilayer film consisting of multiple layers. If the protective film is a multilayer film, it is preferable that each layer constituting the multilayer film is made of the material described above. Also, if the protective film is a multilayer film, it is preferable that the total thickness of the multilayer film satisfies the preferred range described above. If the protective film is a multilayer film, it is preferable that the layer of the multilayer film that is located closest to the absorber film contains Rh. Also, if the layer of the multilayer film that is located closest to the absorber film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0029] The protective film can be deposited using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. When depositing an Rh film by magnetron sputtering, it is preferable to use an Rh target as the target and Ar gas as the sputtering gas. The sputtering gas may also contain Kr or Xe.

[0030] [Absorber Film] The absorber film of the reflective mask blank of the present invention is required to have a high contrast between the EUV light reflected by the multilayer reflective film and the EUV light reflected by the absorber film when a pattern is formed on the absorber film. The absorber film with a pattern formed on it (absorber film pattern) may function as a binary mask by absorbing EUV light, or it may function as a phase-shift mask that reflects EUV light while interfering with the EUV light from the multilayer reflective film to produce contrast. In other words, the absorber film may be a phase-shift film.

[0031] The absorber film contains Ru and W. The Ru content is preferably 20 atomic% or more, more preferably 23 atomic% or more, even more preferably 25 atomic% or more, and particularly preferably 27 atomic% or more, relative to the total atoms of the absorber film, in terms of superior SPM resistance. Furthermore, the Ru content is preferably 50 atomic% or less, more preferably 45 atomic% or less, even more preferably 35 atomic% or less, and particularly preferably 30 atomic% or less, relative to the total atoms of the absorber film, in terms of superior optical properties. The W content is 50 atomic% or more, relative to the total atoms of the absorber film, and is preferably 55 atomic% or more, more preferably 60 atomic% or more, and even more preferably 70 atomic% or more, in terms of superior optical properties. Furthermore, the W content is preferably 80 atomic% or less, more preferably 76 atomic% or less, even more preferably 74 atomic% or less, and particularly preferably 72 atomic% or less, relative to the total atoms of the absorber film, in terms of superior SPM resistance. The total content of Ru and W is preferably 90 atomic% or more, and more preferably 95 atomic% or more, relative to the total atoms of the absorber membrane. The upper limit may be 100 atomic%. That is, the absorber membrane may be a membrane made of Ru and W.

[0032] The amount of W relative to all atoms in the absorber membrane is A Ｗ (Assuming atomic %), the amount of Ru relative to the total atoms of the absorber membrane is A Ｒｕ (When expressed as atomic %), A Ｗ / A Ｒｕ In terms of superior optical properties, a value of 2.00 or higher is preferred, 2.15 or higher is more preferred, 2.30 or higher is even more preferred, and 2.50 or higher is particularly preferred. Ｗ / AＲｕ In terms of superior SPM resistance, a value of 4.00 or less is preferred, 3.50 or less is more preferred, 3.00 or less is even more preferred, and 2.80 or less is particularly preferred.

[0033] The absorber membrane may contain elements other than Ru and W. These other elements include metallic elements other than Ru and W (hereinafter also referred to as "other metallic elements") and nonmetallic elements. Examples of other metallic elements include Ir, Pt, Pd, Ag, Ni, Co, Al, Cr, Mo, Nb, Si, Sn, Ta, Ti, Zr, and V. The content of other metallic elements in the absorber membrane is preferably 10 atomic percent or less, more preferably 5 atomic percent or less, and even more preferably 3 atomic percent or less, relative to the total atoms of the absorber membrane. Furthermore, it is also preferable that the content of other metallic elements in the absorber membrane be 0 atomic percent relative to the total atoms of the absorber membrane. In other words, it is preferable that the absorber membrane does not contain any metallic elements other than Ru and W.

[0034] Examples of nonmetallic elements include one or more elements selected from the group consisting of B, C, N, and O. That is, the absorber membrane may further contain one or more elements selected from the group consisting of B, C, N, and O. When the absorber membrane contains nonmetallic elements, the content is preferably 10 atomic percent or less, more preferably 5 atomic percent or less, and even more preferably 3 atomic percent or less, relative to the total atoms of the absorber membrane. When the absorber membrane contains nonmetallic elements, the content is preferably 0.5 atomic percent or more, and more preferably 1.0 atomic percent or more, relative to the total atoms of the absorber membrane.

[0035] The types and content of elements contained in the absorber film can be measured by XPS. When measuring the types and content of elements in an absorber film using XPS, the layer on the opposite side of the absorber film from the substrate side should be removed by sputtering or similar methods before measurement. A detailed measurement method is described below.

[0036] For XPS analysis, the "PHI 5000 VersaProbe" analyzer manufactured by ULVAC-PHI, Inc. is used. The above instrument is calibrated in accordance with JIS K 0145. First, a measurement sample of approximately 1 cm square is cut out from a reflective mask blank. The obtained measurement sample is set in the measurement holder so that the absorber film side (or the hard mask film side if the reflective mask blank has a hard mask film) is the measurement surface. After loading the measurement holder into the above instrument, the hard mask film is removed from the outermost surface of the hard mask film to a thickness equal to half the thickness of the absorber film. The sputtering rate during the above removal can be measured using a separately prepared sample. After removing a portion of the absorber film, the removed portion is irradiated with X-rays (monochromatic AlKα rays), and the analysis is performed with a photoelectron extraction angle (angle between the surface of the measurement sample and the direction of the detector) of 45°. In addition, a neutralization gun is used to suppress charge-up during the analysis. The analysis involves first performing a wide scan in the binding energy range of 1000 to 0 eV to identify the elements present, and then performing a narrow scan depending on the elements present (e.g., Ru and W). The narrow scan is performed, for example, with a pass energy of 58.7 eV, an energy step of 0.1 eV, a time / step of 50 ms, and 5 integrations. The wide scan is performed with a pass energy of 58.7 eV, an energy step of 1 eV, a time / step of 50 ms, and 2 integrations. The content of each element in the absorber film is determined by analyzing the spectrum obtained from the narrow scan during the XPS analysis using the above procedure, using relative sensitivity coefficients specific to each element and each orbital. Alternatively, the analysis may be performed using the same procedure as above with a model sample formed under the same conditions as those used to form the absorber film.

[0037] When using an absorber film pattern as a binary mask, it is preferable that the absorber film absorbs EUV light and has a low reflectivity of EUV light. Specifically, when EUV light is irradiated onto the surface of the absorber film, the maximum reflectivity of EUV light around 13.5 nm is preferably 2% or less. When using an absorber film pattern as a binary mask, the film thickness of the absorber film is preferably 40 to 70 nm, and more preferably 50 to 65 nm. The film thickness of the absorber film is determined by XRR. The measurement conditions for XRR can be the same as those for the protective film described above.

[0038] When an absorber film pattern is used as a phase shift mask, the reflectivity of the absorber film to EUV light is preferably 2% or more, and more preferably 9-15% in order to obtain a sufficient phase shift effect. Using an absorber film pattern as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. When an absorber film pattern is used as a phase shift mask, the film thickness of the absorber film is preferably 30-75 nm, and more preferably 35-55 nm. The film thickness of the absorber film is determined by XRR. The measurement conditions for XRR can be the same as those for the protective film described above.

[0039] The refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.885 or higher, more preferably 0.893 or higher, even more preferably 0.895 or higher, and most preferably 0.904 or higher. Furthermore, when the absorber film is used as a phase-shift film, the refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.930 or lower, more preferably 0.920 or lower, and even more preferably 0.910 or lower, as this allows for a thinner film thickness of the absorber film. The extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.022 or higher, more preferably 0.035 or higher, even more preferably 0.040 or higher, most preferably 0.045 or higher, and most preferably 0.049 or higher, as this allows for easier adjustment of the reflectance of the absorber film. Furthermore, the extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.058 or less, more preferably 0.056 or less, and more preferably 0.050 or less, as this allows for easier adjustment of the reflectance of the absorber film. The refractive index n and extinction coefficient k can be values ​​from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or values ​​calculated from the "incident angle dependence" of reflectance described below. The incident angle θ of EUV light, the reflectance R for EUV light, the refractive index n of the film, and the extinction coefficient k of the film satisfy the following equation (1): R = |(sinθ - ((n + ik)) ２ -cos ２ θ) １／２ ) / (sinθ+((n+ik) ２ -cos ２ θ) １／２ ) | ... (1) By measuring multiple combinations of incident angle θ and reflectance R, and fitting the multiple measurement data to minimize the error between equation (1), the refractive index n and extinction coefficient k can be calculated.

[0040] The reflective mask blank of the present invention has a 2θ of 40.0° or higher among the diffraction peaks originating from the absorber film observed in the range of 37 to 42° in the XRD chart obtained by in-plane XRD measurement. Here, XRD means X-ray diffraction. In this specification, "In-plane XRD" is a method of obtaining an XRD chart by incidenting X-rays at a very close distance to the surface of the sample to be measured, and rotating the detector of the incident X-rays and diffracted X-rays around the normal direction of the surface of the sample to be measured as an axis. In-plane XRD is also called φ-2θχ scan.

[0041] In this specification, in-plane XRD is measured using a Bruker D8 DISCOVER under the following conditions. When in-plane XRD measurement is performed, an XRD chart is obtained in which the horizontal axis is the angle (2θ) and the vertical axis is the detected X-ray intensity. For measurement, a measurement sample is used in which the hard mask film is removed from the outermost surface of the hard mask film by a thickness equal to half the thickness of the absorber film, so that the absorber film side (or the hard mask film side if the reflective mask blank has a hard mask film) becomes the measurement surface. X-ray source: Cu-Kα rays Output: 45kV-120mA Incident optical system: Multilayer mirror, 0.2mm slit, and solar slit (0.5°) Receiver optical system: Solar slit (0.5°) Detector: Multimode detector EIGER 0D mode scanning range (2θ): 35-50° Step width: 0.1° Step time: 8.0s / step Incident angle: 0.3° relative to the surface of the measurement surface

[0042] One example of a method for obtaining an absorber film exhibiting the aforementioned peaks is to maintain a pressure of 0.10 Pa or higher inside the vacuum chamber when depositing the absorber film.

[0043] The surface roughness of the absorber film is 0.45 nm or less, preferably 0.43 nm or less, more preferably 0.41 nm or less, and even more preferably 0.39 nm or less, for superior SPM resistance. While a smaller surface roughness is preferable, specific examples of its lower limit include 0.1 nm, 0.2 nm, and 0.3 nm. The surface roughness of the absorber film refers to the root mean square roughness (Rms), and the measurement target is the surface of the absorber film opposite to the multilayer reflective film side. If the absorber film has an oxide layer as described later, the measurement target is the surface of the oxide layer opposite to the multilayer reflective film side. Details of the method for measuring the surface roughness of the absorber film are described in the Examples section below.

[0044] One example of a method for obtaining an absorber film exhibiting the surface roughness described above is to reduce the pressure inside the vacuum chamber during film formation to less than 0.15 Pa.

[0045] The absorber film may be a single layer or a multilayer film consisting of multiple layers. When the absorber film is a single layer, the number of steps in mask blank manufacturing is reduced, resulting in superior production efficiency. The absorber film may have two layers with different compositions. In this case, the absorber film may include a lower layer positioned on the multilayer reflective film side and an upper layer positioned on the opposite side of the multilayer reflective film. Specific examples of lower and upper layer combinations include a lower layer containing Ru and N and an upper layer containing Ru and W, and a lower layer containing Ru and W and an upper layer containing Ru and N. When the absorber film is a multilayer film, the layer positioned on the opposite side of the absorber film from the protective film side may be an anti-reflective film used when inspecting the absorber film pattern using inspection light (e.g., wavelength 193-248 nm).

[0046] Absorber films can be formed using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when forming a RuW film as an absorber film using magnetron sputtering, a Ru target and a W target are used, and Ar gas is supplied as the sputtering gas to perform sputtering and deposit the absorber film. Alternatively, when forming a RuW film, targets containing Ru and W may be used. The sputtering gas may also contain Kr or Xe.

[0047] (Oxide layer) The absorber film may have an oxide layer on the surface opposite to the multilayer reflective film side. The oxide layer may be a native oxide film formed on the surface of the absorber film during its manufacture.

[0048] The oxide layer preferably contains O and at least one of Ru and W. Specific materials that make up the oxide layer include tungsten oxide (WO). ３ WO ２ ), ruthenium oxide (RuO ２ Examples include tungsten oxide. The oxygen content in the oxide layer may be 50 to 80 atomic percent relative to the total atoms of the absorber film.

[0049] The types and amounts of elements contained in the oxide layer can be measured by XPS. The method for measuring the types and amounts of elements in the oxide layer using XPS is the same as that used for the absorber membrane, except that the removal of the hard mask film is stopped when the surface of the oxide layer is exposed.

[0050] The thickness of the oxide layer is preferably 2.2 nm or less, more preferably 2.0 nm or less, more preferably 1.8 nm or less, and even more preferably 1.4 nm or less, in terms of superior SPM resistance. A smaller oxide layer thickness is preferable, and a specific example of its lower limit is 0.2 nm. The thickness of the oxide layer is determined by XRR. The measurement conditions for XRR can be the same as those for the protective film described above.

[0051] The ratio of the oxide layer thickness to the absorber film thickness (oxide layer thickness / absorber film thickness) is preferably 0.050 or less, more preferably 0.040 or less, and even more preferably 0.035 or less, in terms of superior SPM resistance. Furthermore, a smaller ratio is preferable, and a specific example of its lower limit is 0.005.

[0052] [Hard Mask Film] The reflective mask blank of the present invention may have a hard mask film on the side opposite to the substrate side of the absorber film. When the reflective mask blank has a hard mask film, dry etching can be performed even if the minimum line width of the absorber film pattern is reduced. Therefore, it is effective for miniaturizing the absorber film pattern.

[0053] The hard mask film preferably contains one or more metallic elements (hereinafter also referred to as "element X") selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, Ru, and Hf. The total content of element X in the hard mask film is preferably 30 atomic% or more, more preferably 50 atomic% or more, even more preferably 60 atomic% or more, and particularly preferably 70 atomic% or more, relative to the total atoms of the hard mask film. The upper limit may be 100 atomic%. That is, the hard mask film may be a film consisting only of element X. The total content of element X in the hard mask film may be 99 atomic% or less, or 95 atomic% or less.

[0054] The hard mask film may contain elements other than element X. It is also preferable that the hard mask film contain at least one element selected from the group consisting of B, N, C, and O.

[0055] Materials that constitute the hard mask film include element X, nitrogen oxides of element X, nitrides, oxynitrides, carbides, carbonitrides, carbonites, fluorides, and oxyfluorides. The material constituting the hard mask film may also be a composite compound (e.g., a composite oxide) containing two or more elements from element X.

[0056] Examples of Cr-based materials containing Cr include materials containing Cr and at least one element selected from the group consisting of O, N, C, and H, and more specifically, CrO, CrN, and CrON. The notation "CrON" represents a material containing Cr, O, and N, and the following similar notations have the same meaning. Examples of Si-based materials containing Si include materials containing Si and at least one element selected from the group consisting of Si, O, N, C, and H, and more specifically, SiO ２ These include SiO, SiC, SiCO, SiCN, and SiCON.

[0057] The thickness of the hard mask film is preferably 2 nm or more. Preferably, the thickness of the hard mask film is 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less. The thickness of the hard mask film is determined by XRR. The measurement conditions for XRR can be the same as those for the protective film described above.

[0058] Hard mask films can be formed using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when forming a Ta film as a hard mask film, a Ta target can be used, and Ar gas can be supplied as the sputtering gas to perform sputtering and form the hard mask film. The sputtering gas may also contain Kr or Xe. Furthermore, when forming a film containing at least one element selected from the group consisting of N and O as a hard mask film, N may be added to the sputtering gas. ２ Gas and O ２ It is sufficient to introduce at least one of the gases. ２ Gas and O ２ By adjusting the amount of at least one of the gases introduced, the amount of at least one element selected from the group consisting of N and O contained in the formed film can be adjusted.

[0059] [Conductive Film] The reflective mask blank of the present invention may have a conductive film on the side of the substrate opposite to the first main surface described above (hereinafter also referred to as the "second main surface"). Having a conductive film allows the reflective mask blank to be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The constituent material of the conductive film can be broadly selected from those described in known literature. For example, a high dielectric constant coating described in Japanese Patent Publication No. 2003-501823, specifically a coating consisting of Si, Mo, Cr, CrON, or TaSi, can be applied. Alternatively, the constituent material of the conductive film may be a Cr compound containing Cr and one or more selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more selected from the group consisting of B, N, O, and C. The thickness of the conductive film is preferably 10 to 1000 nm, and more preferably 10 to 400 nm. The conductive film may also have a function of adjusting the stress on the second main surface side of the reflective mask blank. That is, the conductive film can adjust the reflective mask blank to be flat by balancing the stress from various films formed on the first main surface side. The conductive film can be formed using known film deposition methods, such as sputtering methods such as DC sputtering, magnetron sputtering, and ion beam sputtering, CVD, vacuum deposition, and electroplating.

[0060] [Method for Manufacturing a Reflective Mask Blank] The present invention provides a method for manufacturing a reflective mask blank comprising, in this order, a substrate, a multilayer reflective film that reflects EUV light, and an absorber film containing ruthenium and tungsten. In the method for manufacturing a reflective mask blank of the present invention, the tungsten content is 50 atomic percent or more relative to the total atoms of the absorber film. In the method for manufacturing a reflective mask blank of the present invention, the absorber film is formed in a vacuum chamber, and the pressure in the vacuum chamber when forming the absorber film is 0.10 Pa or more and less than 0.15 Pa.

[0061] This manufacturing method yields a reflective mask blank having an absorber film with excellent SPM resistance. This is presumed to be because the pressure inside the vacuum chamber during film formation of the absorber film is within a predetermined range, resulting in an absorber film that satisfies the aforementioned values ​​for 2θ and surface roughness measured by the In-plane XRD.

[0062] The method for manufacturing a reflective mask blank of the present invention is suitable for manufacturing the mask blank of the present invention as described above. An example of a preferred embodiment of the method for manufacturing a reflective mask blank of the present invention is shown below.

[0063] One embodiment of the present invention for manufacturing a reflective mask blank includes a step 1 of forming a multilayer reflective film on a substrate to obtain a laminate 1 in which the substrate and the multilayer reflective film are stacked in that order, and a step 2 of forming an absorbent film on the multilayer reflective film in the laminate 1 placed in a vacuum chamber while maintaining the pressure inside the vacuum chamber at 0.10 Pa or more and less than 0.15 Pa.

[0064] The details of the substrate used in step 1 are as described above. Furthermore, the details of the multilayer reflective film obtained in step 1 and the method of its deposition are also as described above.

[0065] In step 2, the pressure inside the vacuum chamber when forming the absorber film is 0.10 Pa or more and less than 0.15 Pa, preferably 0.11 to 0.14 Pa, and more preferably 0.12 to 0.13 Pa, from the viewpoint of superior SPM resistance. The pressure inside the vacuum chamber is measured by a pressure gauge attached to the vacuum chamber. The pressure inside the vacuum chamber can be adjusted within the above range, for example, by controlling the gas pressure of the sputtering gas introduced into the vacuum chamber. Details of the absorber film obtained in step 2 and the method of forming it are as described above.

[0066] In one embodiment of the method for manufacturing a reflective mask blank of the present invention, step 1A may be further included between step 1 and step 2, in which a protective film is formed on the multilayer reflective film side of the laminate 1 to obtain a laminate 2 in which a substrate, a multilayer reflective film, and a protective film are laminated in this order. Details of the protective film and the method for forming it are as described above. If step 1A is included, in step 2, an absorbent film may be formed on the protective film in the laminate 2.

[0067] In one embodiment of the method for manufacturing a reflective mask blank of the present invention, step 2A may be further included after step 2, in which a hard mask film is formed on the side of the absorber film opposite to the multilayer reflective film side. Details of the hard mask layer and the method for forming it are as described above.

[0068] In one embodiment of the method for manufacturing a reflective mask blank of the present invention, a step 2B may be further included after step 2 (or after step 2A if step 2A is included), in which a conductive film is formed on the side of the substrate on which the multilayer reflective film is laminated. Details of the conductive film and the method for forming it are as described above.

[0069] <Method for Manufacturing a Reflective Mask and the Reflective Mask> The reflective mask of the present invention is obtained by patterning the absorbent membrane of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be explained with reference to Figure 2.

[0070] Figure 2(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in that order. A known method can be used to form the resist pattern 40. For example, a resist is applied to the absorber film 18 of the reflective mask blank, and exposure and development are performed to form the resist pattern 40. The resist pattern 40 corresponds to the pattern formed on the wafer using a reflective mask. Then, using the resist pattern 40 in Figure 2(a) as a mask, the absorber film 18 is etched and patterned, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 18pt shown in Figure 2(b). Next, as shown in Figure 2(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 2(b), and dry etching is performed using the resist pattern 41 in Figure 2(c) as a mask. Dry etching is performed until the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 2(d).

[0071] Dry etching using a gas containing a fluorine compound (F-type gas) is preferred when forming the absorber film pattern 18pt. As described above, the absorber film 18 contained in the reflective mask blank of the present invention has excellent etching resistance, and in particular, excellent etching resistance with gases containing fluorine compounds. Examples of fluorine compounds include CF ４ CHF ３ , C ２ F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ ,CH ２ F ２ ,CH ３ F, C ３ F ８ F ２ SF ６ , and NF ３Examples include gases such as fluorine compounds and mixtures thereof. The gas containing the fluorine compound may, if necessary, be mixed with active gases such as oxygen gas and chlorine gas, and inert gases such as nitrogen gas, helium gas, and argon gas in addition to the fluorine compound gas. In particular, it is preferable to include oxygen gas as the active gas. The etching gas may be plasma-generated and used to etch the absorber film 18.

[0072] The resist patterns 40 and 41 can be removed by known methods, including removal with a cleaning solution. Examples of cleaning solutions include sulfuric acid-hydrogen peroxide aqueous solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide aqueous solution (APM), OH radical cleaning water, and ozonated water, with SPM being the most commonly used. Since the absorbent film of the reflective mask blank of the present invention has excellent SPM resistance, it can be suitably used in the manufacture of reflective masks using SPM.

[0073] If the reflective mask blank has a hard mask film, the hard mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the hard mask film as a mask. The patterning of the hard mask film can be done by known methods, for example, dry etching with an oxygen-containing gas or a chlorine-containing gas (Cl-based gas). If the reflective mask blank has a hard mask film, a step to remove the hard mask film may be performed. In addition, the hard mask film may be removed simultaneously in the step to remove the resist pattern 40 or 41 described above. As a method for removing the hard mask film, for example, it can be done by the same method as etching the hard mask film described above.

[0074] The reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention has the absorber film pattern described above. The reflective mask of the present invention can be suitably applied as a reflective mask used for exposure with EUV light.

[0075] The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Examples 1 to 3 are examples, and Examples 4 to 6 are comparative examples.

[0076] <Example 1> First, we will explain the procedure for obtaining the reflective mask blank shown in Example 1 as a representative example.

[0077] [Substrate] First, as a substrate, SiO ２ -TiO ２ A glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared. This glass substrate has a thermal expansion coefficient of 0.02 × 10⁻¹⁰ at 20°C. －７ The temperature is / °C, the Young's modulus is 67 GPa, the Poisson's ratio is 0.17, and the specific stiffness is 3.07 × 10⁻⁶. ７ I understand ２ / s ２ The quality assurance area of ​​the first main surface of the substrate had a root mean square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less achieved by polishing. A 100 nm thick Cr film was deposited on the second main surface of the substrate using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / □.

[0078] [Multilayer Reflective Film] Next, a Mo / Si multilayer reflective film was formed on the first main surface of the substrate. The Mo / Si multilayer reflective film was obtained by repeatedly depositing a Si film (thickness 4.5 nm) and a Mo film (thickness 2.3 nm) 40 times using the ion beam sputtering method, and after the 40th Mo film was formed, a Si film (thickness 4.5 nm) was further formed. The total thickness of the Mo / Si multilayer reflective film was 276.5 nm ((4.5 nm + 2.3 nm) × 40 + 4.5 nm).

[0079] [Absorber Film] A RuW film (thickness 41.5 nm) was formed as an absorber film on the multilayer reflective film formed by the above procedure. The RuW film was formed by DC sputtering under the following conditions: • Target: Ru target, W target • Sputtering gas: Ar gas (pressure in vacuum chamber: 0.12 Pa) • Deposition rate: 0.049 nm / second • Input power density per target area: 1.3 W / cm² ２ (Ru target), 7.7 W / cm² ２ (Dual target)

[0080] <Examples 2-6> The reflective mask blanks in Examples 2-6 were obtained in the same manner as in Example 1, except that the composition of the absorber film and the pressure inside the vacuum chamber during film formation of the absorber film were as shown in the table below.

[0081] <Evaluation Method and Criteria> [Composition and Film Thickness of Each Layer] The chemical composition of the absorber film was measured by XPS as described above using an ULVAC-PHI X-ray photoelectron spectrometer (PHI 5000 VersaProbe). The film thickness of each film, and the film thickness of the oxide layer on the surface opposite to the multilayer reflective film side of the absorber film, were measured by XRR as described above.

[0082] [In-plane XRD measurement of the absorber membrane] The above-described in-plane XRD measurement was performed to determine the 2θ of the peak with the highest intensity (referred to as "maximum peak 2θ" in the table below) among the diffraction peaks originating from the absorber membrane observed in the range of 2θ to 37-42°.

[0083] [Surface roughness (Rms) of the absorber film] The surface roughness (Rms) of the absorber film on the side opposite to the multilayer reflective film was measured in dynamic force mode using an atomic force microscope (SPI-3800) manufactured by SII Corporation. The measurement area for surface roughness was 1 μm × 1 μm, and an SI-DF40 cantilever manufactured by SII Corporation was used.

[0084] [SPM Resistance] A reflective mask blank was immersed in SPM (sulfuric acid peroxide solution) at 100°C for 20 minutes. The change in film thickness of the absorber film before and after immersion was measured by XRR, and the etching rate of the absorber film by SPM (unit: nm / min) was measured by dividing the result by the immersion time. From the obtained etching rate, the SPM resistance of the absorber film was evaluated according to the following evaluation criteria. SPM was obtained by mixing concentrated sulfuric acid and hydrogen peroxide solution in a ratio of 75 vol%:25 vol% (concentrated sulfuric acid:hydrogen peroxide solution). The concentrated sulfuric acid contained 96 vol% sulfuric acid and 4 vol% water. The hydrogen peroxide solution contained 30-35 vol% hydrogen peroxide and 65-70 vol% water. "A": Etching rate less than 0.020 nm / min "B": Etching rate 0.020 nm / min or more, less than 0.060 nm / min "C": Etching rate 0.060 nm / min or more

[0085]

[0086] The results shown in Table 1 confirm that absorber films containing Ru and W, with a W content of 50 atomic percent or more, where the 2θ value of the maximum peak is 40.0° or higher and the surface roughness is 0.45 nm or less, exhibit excellent SPM resistance (Examples 1-3). On the other hand, absorber films containing Ru and W, with a W content of 50 atomic percent or more, where the 2θ value of the maximum peak is less than 40.0° or the surface roughness is greater than 0.45 nm, exhibited poor SPM resistance (Examples 4-6).

[0087] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2025-008003, filed on January 20, 2025, are incorporated herein by reference as disclosure of the present invention.

[0088] 10 Reflective mask blank 12 Substrate 14 Multilayer reflective film 16 Protective film 18 Absorber film 18pt Absorber film pattern 40, 41 Resist pattern

Claims

1. A reflective mask blank comprising, in this order, a substrate, a multilayer reflective film that reflects EUV light, and an absorber film, wherein the absorber film contains ruthenium and tungsten, the tungsten content is 50 atomic percent or more relative to the total atoms of the absorber film, in an XRD chart obtained by in-plane XRD measurement, the 2θ of the peak with the highest intensity among the diffraction peaks originating from the absorber film observed in the range of 2θ to 37 to 42° is 40.0° or more, and the surface roughness of the surface of the absorber film is 0.45 nm or less.

2. The reflective mask blank according to claim 1, wherein the absorber film has an oxide layer on the surface opposite to the multilayer reflective film side, and the thickness of the oxide layer is 2.0 nm or less.

3. The reflective mask blank according to claim 2, wherein the ratio of the thickness of the oxide layer to the thickness of the absorbent film is 0.050 or less.

4. The reflective mask blank according to claim 1 or 2, wherein the tungsten content is 55 to 80 atomic percent relative to the total atoms of the absorber film.

5. The reflective mask blank according to claim 1 or 2, wherein the ruthenium content is 20 to 45 atomic percent relative to the total atoms of the absorber film.

6. The tungsten content relative to the total atoms of the absorber membrane is A Ｗ (Atomic %), and the ruthenium content relative to the total atoms of the absorber membrane is A Ｒｕ (When expressed as atomic %), A Ｗ / A Ｒｕ A reflective mask blank according to claim 1 or 2, wherein the coefficient of 7. The reflective mask blank according to claim 1 or 2, wherein a protective film is provided between the multilayer reflective film and the absorber film, and the protective film contains rhodium.

8. A method for manufacturing a reflective mask blank, comprising, in this order, a substrate, a multilayer reflective film that reflects EUV light, and an absorber film containing ruthenium and tungsten, wherein the tungsten content is 50 atomic percent or more relative to the total atoms of the absorber film, the absorber film is formed in a vacuum chamber, and the pressure in the vacuum chamber when forming the absorber film is 0.10 Pa or more and less than 0.15 Pa.

9. A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank according to claim 1 or 2.

10. A method for manufacturing a reflective mask, comprising the step of patterning the absorbent membrane of the reflective mask blank according to claim 1 or 2 to form an absorbent membrane pattern.

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