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

Abstract

To provide a reflective mask blank in which the ratio of the etching rate of the absorber film to the etching rate of the hard mask film is large when etching the absorber film. [Solution] The reflective mask blank of the present invention is a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, an absorber film, and a hard mask film in this order, The absorber membrane contains platinum and at least one metal element X selected from the group consisting of tantalum and tungsten, and the total content of the metal element X in the absorber membrane is 5 atomic percent or more relative to the total content of platinum and the metal element X. The hard mask film described above contains chromium, and the chromium content in the hard mask film is 70 atomic percent or more relative to the total atoms of the hard mask film.

Description

[Technical Field]

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

[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 the 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 as a resist pattern onto the wafer through the reduction projection optical system of the exposure apparatus, and subsequent processing is carried out. As for materials used in absorber membranes, for example, Patent Document 1 discloses an absorber membrane containing platinum and tantalum. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 7553735 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the manufacturing of reflective masks, when etching and patterning the absorber film, sometimes the hard mask film is etched and patterned first, and the resulting hard mask film pattern is used as a mask to etch the absorber film. When the present inventors investigated the manufacture of a reflective mask using an absorber film containing platinum and tantalum as described in Patent Document 1, they found that the etching selectivity ratio was low depending on the combination of materials between the absorber film and the hard mask film, and that further investigation was necessary.

[0007] The present invention has been made in view of the above problems, and aims to provide a reflective mask blank in which the ratio of the etching rate of the absorber film to the etching rate of the hard mask film is large when etching the absorber film. Furthermore, the present invention also aims to provide a reflective mask and a method for manufacturing a reflective mask. [Means for solving the problem]

[0008] As a result of diligent research into the above-mentioned problems, the present inventors discovered that by combining an absorber film of a predetermined composition with a hard mask film of a predetermined composition, the ratio of the etching rate of the absorber film to the etching rate of the hard mask film during etching of the absorber film can be increased, leading to the present invention.

[0009] In other words, the inventors found that the above problem could be solved by the following configuration. [1] A circuit board and A multilayer reflective film that reflects EUV light, Absorbent membrane and A reflective mask blank having a hard mask film in this order, The absorber film comprises platinum and at least one metallic element X selected from the group consisting of tantalum and tungsten. The total content of the metal element X in the absorber membrane is 5 atomic percent or more relative to the total content of platinum and the metal element X. The above hard mask film contains chromium, A reflective mask blank, wherein the chromium content in the hard mask film is 70 atomic% or more based on all the atoms of the hard mask film. 〔2〕 The reflective mask blank according to 〔1〕, wherein in the absorber film, the value of M obtained by the following formula (1) is 550 °C or lower. 〔3〕 The reflective mask blank according to 〔1〕 or 〔2〕, wherein the absorber film further contains at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon. 〔4〕 The metal element X contains tungsten, The reflective mask blank according to any one of 〔1〕 to 〔3〕, wherein the tungsten content in the absorber film is 80 atomic% or less based on all the atoms of the absorber film. 〔5〕 The metal element X contains tantalum, The reflective mask blank according to any one of 〔1〕 to 〔3〕, wherein the tantalum content in the absorber film is 5 atomic% or more and 60 atomic% or less based on all the atoms of the absorber film. 〔6〕 The refractive index of the absorber film at a wavelength of 13.5 nm is 0.9 30 or lower, The reflective mask blank according to any one of 〔1〕 to 〔5〕, wherein the attenuation coefficient of the absorber film at a wavelength of 13.5 nm is 0.040 or more. 〔7〕 The absorber film further has a second absorber film on the surface on the side of the multilayer reflective film, The reflective mask blank according to any one of 〔1〕 to〔6〕, wherein the second absorber film contains at least one element selected from the group consisting of ruthenium, chromium, and tantalum and at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon. 〔8〕 A protective film is further provided between the absorber film and the antireflection film, The reflective mask blank according to any one of 〔1〕 to 〔7〕, wherein the rhodium content in the protective film is 50 atomic% or more based on all the atoms of the protective film. 〔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 〔8〕. 〔10〕 A method for manufacturing a reflective mask, including the step of patterning the absorber film of the reflective mask blank according to any one of 〔1〕 to 〔8〕.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a reflective mask blank in which the ratio of the etching rate of the absorber film to the etching rate of the hard mask film when etching the absorber film is large. Further, according to the present invention, it is also possible to provide a reflective mask and a method for manufacturing the reflective mask.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. [Figure 2] It is a cross-sectional view showing an example of a manufacturing process of a reflective mask using the reflective mask blank of the present invention.

Modes for Carrying Out the 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 this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, 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, Re, Os, Ir, and Pt, etc.). Also, in this specification, silicon (Si) is included in metal elements.

[0013] <Reflective Mask Blank> The reflective mask blank of the present invention comprises, in this order, a substrate, a multilayer reflective film that reflects EUV light, an absorber film, and a hard mask film, wherein the absorber film contains at least one metal element X selected from the group consisting of platinum, tantalum, and tungsten, and the total content of the metal element X in the absorber film is 5 atomic percent or more relative to the total content of platinum and the metal element X, and the hard mask film contains chromium, and the chromium content in the hard mask film is 70 atomic percent or more relative to the total atoms of the hard mask film.

[0014] The reflective mask blank of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional view showing an example of a reflective mask blank. The reflective mask blank 10 shown in Figure 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, an absorber film 18, and a hard mask film 20 in that order. Although the reflective mask blank 10 has a protective film 16, the reflective mask blank does not necessarily have to have a protective film. Furthermore, although not shown in Figure 1, the reflective mask blank 10 may have a back surface conductive film, described later, on the side opposite to the hard mask film side of the substrate 12. Also, the reflective mask blank 10 may have a second absorber film, described later, on the surface of the absorber film 18 on the multilayer reflective film 14 side. For example, the reflective mask blank 10 may have a second absorber film, described later, between the protective film 16 and the absorber film 18, and if the reflective mask blank does not have a protective film 16, it may have a second absorber film between the absorber film 18 and the multilayer reflective film 14.

[0015] The reflective mask blank of the present invention exhibits a high ratio of the etching rate of the absorber film to the etching rate of the hard mask film when etching the absorber film (hereinafter also simply referred to as the "etching selectivity ratio"). The detailed reason for this is unknown, but it is presumed to be as follows. In etching an absorber film containing platinum, it is preferable to perform etching with a gas containing a fluorine compound. When etching with such a gas, it is presumed that an excellent etching selectivity ratio can be achieved by combining an absorber film containing at least one metal element X selected from the group consisting of tantalum and tungsten, which have low fluoride melting points and are easily etched, with a hard mask film containing a predetermined amount or more of chromium, which has a high fluoride melting point and is difficult to etch.

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

[0017] [substrate] The substrate of the reflective mask blank of the present invention preferably has a small coefficient of thermal expansion. A smaller coefficient of thermal expansion of the substrate helps to suppress distortion of the absorber film pattern due to heat during exposure with EUV light. The thermal expansion coefficient of the substrate is 0 ± 1.0 × 10 at 20°C. -7 A temperature of / ℃ is preferred, and 0±0.3×10 -7 / ℃ is preferable. Materials with a low coefficient of thermal expansion include SiO2-TiO2 glass, but are not limited to this; crystallized glass with precipitated β-quartz solid solution, quartz glass, metallic silicon, and metal substrates can also be used. For SiO2-TiO2 glass, it is preferable to use quartz glass containing 90-95% by mass of SiO2 and 5-10% by mass of TiO2. When the TiO2 content is 5-10% by mass, the coefficient of linear expansion at room temperature is approximately zero, and there is almost no dimensional change at room temperature. Note that SiO2-TiO2 glass may also contain trace components other than SiO2 and TiO2.

[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 the surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to achieve a predetermined flatness, which is advantageous for the pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. Specifically, the substrate 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). The flatness can be measured using a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate can be determined as appropriate by the mask design, 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). Circuit boards are often rectangular or square in shape. The substrate preferably has high rigidity in order 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] Because multilayer reflective films can achieve high reflectivity of EUV light, they typically use a multilayer reflective film in which a high refractive index layer, which exhibits a high refractive index for EUV light, and a low refractive index layer, which exhibits a low refractive index for EUV light, are alternately stacked multiple times. The multilayer reflective film may be constructed by stacking multiple layers in a layered structure in which a high refractive index layer and a low refractive index layer are stacked in that order from the substrate side, with each layer forming one period, or by stacking multiple layers in a layered structure in which a low refractive index layer and a high refractive index layer are stacked in that order from the substrate side, with each layer forming one period. A layer containing Si can be used as the high refractive index layer. The Si-containing material can be elemental Si, or a Si compound containing Si and at least one element selected from the group consisting of B, C, N, and O. By using a high refractive index layer containing Si, a reflective mask with high EUV light reflectivity can be obtained. As the low refractive index layer, 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. Si is widely used in the high refractive index layer, and Mo is widely used in the low refractive index layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to these, 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 etching. It is also preferable that the protective film protects the multilayer reflective film when the hard mask film, which will be described later, is removed.

[0024] The protective film preferably contains at least one element selected from the group consisting of Si, Ru, and Rh. Furthermore, the protective film may also contain Rh. If the protective film contains Rh, the Rh content is preferably 50 atomic% 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, Ze, 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. Additionally, adding Ra, Ir, Pd, or Y to Rh can improve resistance to etching processes. Materials that can be used for the protective film include elemental Al metal, nitrides containing Al and N, and Al2O3, etc. In particular, Ru elemental metal, Ru alloy, Rh elemental metal, or Rh alloy are preferred as materials 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 same method as for the absorber membrane can be used for detailed XPS measurements.

[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, from the viewpoint 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 measurements. CuKα rays are used as the X-ray source, with a tube voltage of 40kV and a tube current of 30mA. The accompanying software (GlobalFit) is used for analysis.

[0028] The protective film may be a single-layer film 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. Furthermore, if the protective film is a multilayer film, it is preferable that the total film thickness of the multilayer film satisfies the preferred range described above. When the protective film is a multilayer film, it is preferable that the layer located closest to the absorber film contains Rh. Furthermore, if the layer 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.

[0030] [Absorbing membrane] 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 patterned absorber film (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 and interferes with EUV light from a multilayer reflective film to produce contrast. In other words, the absorber film may also be a phase-shift film.

[0031] The absorber membrane contains Pt and at least one metal element X selected from the group consisting of Ta and W. The Pt content is preferably less than 95 atomic percent relative to the total content of Pt and metal element X, more preferably 90 atomic percent or less, even more preferably 85 atomic percent or less, particularly preferably 75 atomic percent or less, and most preferably 60 atomic percent or less, from the viewpoint of the etchability and etching selectivity ratio of the absorber film. Furthermore, the Pt content is preferably 10 atomic percent or more, more preferably 20 atomic percent or more, even more preferably 30 atomic percent or more, particularly preferably 40 atomic percent or more, and most preferably 50 atomic percent or more, relative to the total content of Pt and metal element X, from the viewpoint of the refractive index n and extinction coefficient k of the absorber film. It is also preferable that the Pt content relative to the total atoms of the absorber film satisfies the above preferred range. The content of metal element X is 5 atomic percent or more relative to the total content of Pt and metal element X. From the viewpoint of the etchability and etching selectivity of the absorber film, it is preferably 10 atomic percent or more, more preferably 20 atomic percent or more, even more preferably 30 atomic percent or more, and particularly preferably 40 atomic percent or more. Furthermore, from the viewpoint of the refractive index n and extinction coefficient k of the absorber film, the content of metal element X relative to the total content of Pt and metal element X is preferably 90 atomic percent or less, more preferably 70 atomic percent or less, even more preferably 60 atomic percent or less, particularly preferably 50 atomic percent or less, and most preferably 45 atomic percent or less. It is also preferable that the content of metal element X relative to the total atoms of the absorber film satisfies the above preferred range. When metal element X contains W, the W content in the absorber film is preferably 80 atomic% or less, more preferably 70 atomic% or less, even more preferably 60 atomic% or less, particularly preferably 50 atomic% or less, and most preferably 45 atomic% or less, relative to the total atoms of the absorber film. Furthermore, when metal element X contains W, the W content in the absorber film is preferably 5 atomic% or more, more preferably 10 atomic% or more, even more preferably 20 atomic% or more, particularly preferably 30 atomic% or more, and most preferably 40 atomic% or more, relative to the total atoms of the absorber film. When metal element X contains Ta, the Ta content in the absorber film is preferably 2 atomic% or more, more preferably 5 atomic% or more, even more preferably 10 atomic% or more, particularly preferably 30 atomic% or more, and most preferably 40 atomic% or more, relative to the total atoms of the absorber film, from the viewpoint of the etchability and etching selectivity of the absorber film. Furthermore, when metal element X contains Ta, the Ta content in the absorber film is preferably 80 atomic% or less, more preferably 70 atomic% or less, and even more preferably 60 atomic% or less, relative to the total atoms of the absorber film, from the viewpoint of the optical properties of the absorber film. The total content of Pt and metal element X is preferably 80 atomic% or more, and more preferably 90 atomic% or more, relative to the total atoms of the absorber film. The upper limit may be 100 atomic%. In other words, the absorber film may be a film made of Pt and metal element X. The total content of Pt and metal element X may be 99 atomic percent or less, or 95 atomic percent or less.

[0032] The absorber membrane may contain elements other than Pt and metal element X. These other elements include other metallic elements other than Pt and metal element X, as well as nonmetallic elements. Other metallic elements include, for example, Ir, Ru, Pd, Ag, Ni, Co, Al, Cr, Mo, Nb, Si, Sn, Ti, Zr, and V. The content of other metal 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 metal elements in the absorber membrane is 0 atomic percent, relative to the total atoms of the absorber membrane. In other words, it is preferable that it does not contain any metal elements other than Pt and W. The nonmetallic element is preferably at least one element selected from the group consisting of N, O, B, and C, with N being more preferred. The presence of the above elements in the absorber film tends to reduce the crystallinity of the absorber film. If the absorbent membrane contains nonmetallic elements, the total content of nonmetallic elements is preferably 1 to 20 atomic percent, more preferably 1 to 10 atomic percent, and even more preferably 1 to 5 atomic percent, relative to the total atoms of the absorbent membrane. Furthermore, if the absorbent membrane contains N, the N content is preferably 1 to 20 atomic percent, more preferably 1 to 10 atomic percent, and even more preferably 1 to 5 atomic percent, relative to the total atoms of the absorbent membrane. From the viewpoint of etching selectivity, the oxygen content of the absorber film is preferably 5 atomic percent or less, more preferably 1 atomic percent or less, and even more preferably 0 atomic percent, relative to the total atoms of the absorber film. In other words, it is preferable that the absorber film does not contain oxygen. Furthermore, if the reflective mask blank of the present invention has a hard mask film as described later, it is preferable that the absorber film does not contain metal elements contained in the hard mask film.

[0033] 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 the absorber film using XPS, the layer on the opposite side of the absorber film from the substrate side should be removed by sputtering or other means before measurement. The detailed measurement method is described below.

[0034] For XPS analysis, we use the "PHI 5000 VersaProbe" analyzer manufactured by ULVAC-PHI, Inc. This analyzer is calibrated in accordance with JIS K 0145. First, a measurement sample approximately 1 cm square is cut out from the reflective mask blank. The obtained measurement sample is then placed in the measurement holder so that the absorber membrane side (or the hard mask membrane side if the reflective mask blank has a hard mask membrane) is the measurement surface. After loading the measuring holder into the apparatus, 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 membrane, the removed area is irradiated with X-rays (monochromatic AlKα rays), and the analysis is performed with a photoelectron extraction angle (the angle between the surface of the sample and the direction of the detector) of 45°. In addition, a neutralization gun is used to suppress charge buildup during the analysis. The analysis involves first performing a wide scan in the bond 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., Pt and W). The narrow scan is performed with, for example, 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 membrane is determined by analyzing the spectrum obtained by narrow scan during XPS analysis using the procedure described above, using relative sensitivity coefficients specific to each element and each orbital. Alternatively, the analysis may be performed using a model sample formed under the same conditions as those used to form the absorbent membrane, following the same procedure as described above.

[0035] The absorber film preferably has a value of M, calculated by the following formula (1), of 550°C or less, more preferably 500°C or less, even more preferably 400°C or less, and particularly preferably 370°C or less. When the value of M satisfies the above range, the etchability of the absorber film is excellent, and the etching selectivity ratio tends to be high. Furthermore, the value of M is preferably 30°C or higher, more preferably 100°C or higher, and even more preferably 220°C or higher.

[0036]

number

[0037] In formula (1), M i The absorber membrane contains n types of metal elements (metal element A1, metal element A2, ..., metal element A n ) the i-th type of metallic element A iThe melting point of the fluoride is shown, c i This is the total content of all metal elements contained in the absorber membrane, relative to the content of metal element A. i This indicates the atomic ratio of the content, where i is an integer between 1 and n, and n is an integer greater than or equal to 2. In other words, it is preferable that the sum of the calculated values ​​obtained by multiplying the melting point of the fluoride of each metal element contained in the absorber membrane by the atomic ratio of the content of each metal element to the total content of all metal elements contained in the absorber membrane satisfies the above preferred range.

[0038] Unless otherwise specified, the fluorides of each metal element contained in the absorber film were selected and described based on the inventor's knowledge and etching literature. The melting points of fluorides for each metal element are based on the values ​​listed in the literature (CRC Handbook of Chemistry and Physics, 93rd Edition). For example, in this specification, the melting points of the fluorides of the following metal elements are the values ​​shown in the table below.

[0039] [Table 1]

[0040] For example, if the absorber membrane contains 80 atomic percent of Pt as metal element A1 and 20 atomic percent of Ta as metal element A2, the value of M is calculated as follows. M(℃)=600.0×(80 / (80+20))+96.9×(20 / (80+20))=499.4(℃)

[0041] 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, it is preferable that the maximum reflectivity of EUV light around 13.5 nm is 2% or less. When using an absorber membrane pattern as a binary mask, the thickness of the absorber membrane is preferably 40-70 nm, and more preferably 50-65 nm. The film thickness of the absorber film is determined by XRR.

[0042] 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 less, more preferably 0.925 or less, still more preferably 0.915 or less, and particularly preferably 0.905 or less, in that the film thickness of the absorber film can be made thinner. Further, the refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.895 or more, and more preferably 0.900 or more. The extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.030 or more, more preferably 0.040 or more, still more preferably 0.045 or more, and particularly preferably 0.050 or more, in that the reflectance of the absorber film can be more easily adjusted. Further, the extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.057 or less, and more preferably 0.055 or less, in that the reflectance of the absorber film can be more easily adjusted. The refractive index n and the extinction coefficient k can be the values in the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or the values calculated from the "dependence on the incident angle" of the reflectance described below. The incident angle θ of EUV light, the reflectance R with respect to 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) By measuring a plurality of combinations of the incident angle θ and the reflectance R and fitting them so that the error between the plurality of measurement data and the formula (1) is minimized, the refractive index n and the extinction coefficient k can be calculated.

[0043] The absorber film is preferably low in crystallinity, and more preferably amorphous. Low crystallinity of the absorber film allows for higher smoothness and flatness. High smoothness and flatness of the absorber film reduces the edge roughness of the absorber film pattern, thereby improving the dimensional accuracy of the absorber film pattern.

[0044] The absorbent membrane is preferably a single-layer membrane. When the absorbent membrane is a single-layer membrane, the number of steps in the mask blank manufacturing process is reduced, resulting in superior production efficiency. The absorber film may have an anti-reflective coating on the side opposite to the protective film side of the absorber film, for pattern inspection of the absorber film using inspection light (for example, wavelength 193-248 nm).

[0045] 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 PtW film as an absorber film using magnetron sputtering, a Pt target and a W target are used, and sputtering is performed with Ar gas to deposit the absorber film. Alternatively, when forming a PtW film, targets containing Pt and W may be used.

[0046] [Second Absorbing Membrane] The reflective mask blank of the present invention may further have a second absorber film on the surface of the absorber film on the multilayer reflective film side. Having a second absorber film in the reflective mask blank can suppress the influence on the multilayer reflective film during the etching process of the absorber film (usually a dry etching process). The second absorber film described above is positioned so as to be in contact with the surface of the absorber film on the multilayer reflective film side, and is provided between the absorber film and the protective film, for example, when the reflective mask blank has a protective film.

[0047] The second absorber membrane preferably contains at least one element (element Z1) selected from the group consisting of Ru, Cr, and Ta. The second absorber membrane may contain only one element Z1, or two or more elements Z1. For example, the second absorber membrane may contain Ru and Cr. The second absorber membrane may contain metallic elements other than element Z1. Examples of metallic elements other than element Z1 include Hf, W, and Re. The content of element Z1 in the second absorber membrane is preferably 35 atomic% or more, more preferably 50 atomic% or more, even more preferably 70 atomic% or more, particularly preferably 80 atomic% or more, and most particularly preferably 90 atomic% or more, relative to the total atoms of the second absorber membrane. The upper limit of the content of element Z1 in the second absorber membrane may be 100 atomic%, 95 atomic% or less, 90 atomic% or less, or 85 atomic% or less. If the second absorber membrane contains two or more types of element Z1, the above content of element Z1 refers to the total content of element Z1. The second absorber membrane may also preferably contain at least one element (element Z2) selected from the group consisting of N, O, B, and C. The content of element Z2 in the second absorber membrane is preferably 1 atomic percent or more, more preferably 3 atomic percent or more, and even more preferably 5 atomic percent or more, relative to the total atoms of the second absorber membrane. The upper limit is preferably 25 atomic percent or less, more preferably 20 atomic percent or less, and even more preferably 10 atomic percent or less. If the second absorber membrane contains two or more types of element Z2, the above content of element Z2 refers to the total content of element Z2. The types of elements contained in the second absorber membrane and their content can be measured using the same method as described above for the absorber membrane.

[0048] From the viewpoint of the optical properties of the resulting reflective mask, the thickness of the second absorber film is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more. Furthermore, from the viewpoint of etching resistance, the thickness of the second absorber film is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less. The thickness of the second absorber membrane is determined by XRR.

[0049] The refractive index n of the second absorber film at a wavelength of 13.5 nm is preferably 0.890 to 0.930. Furthermore, the extinction coefficient k of the second absorber film at a wavelength of 13.5 nm is preferably 0.0150 to 0.0400. The refractive index n and extinction coefficient k can be measured in the same manner as the absorber film described above.

[0050] The second absorber film can be deposited using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering.

[0051] [Hard mask film] The reflective mask blank of the present invention has a hard mask film on the side of the absorber film opposite to the substrate side. Having a hard mask film in the reflective mask blank allows dry etching to be performed even when the minimum line width of the absorber film pattern is reduced. Therefore, it is effective for miniaturizing the absorber film pattern.

[0052] The hard mask film contains Cr. The Cr content in the hard mask film is 70 atomic percent or more relative to the total atoms of the hard mask film, preferably 80 atomic percent or more, and more preferably 85 atomic percent or more, in terms of superior etching selectivity. The upper limit may be 100 atomic percent, but in terms of the etchability of the hard mask film, it is preferably less than 100 atomic percent, and more preferably 95 atomic percent or less. The hard mask film may further contain at least one element selected from the group consisting of N, O, C, and H (hereinafter also referred to as element Y), and it is preferable that it contains at least one element selected from the group consisting of N and O, and more preferably that it contains N. When the hard mask film contains element Y, the content of element Y is preferably 1 atomic% or more, more preferably 5 atomic% or more, and even more preferably 10 atomic% or more, relative to the total atoms of the hard mask film. The upper limit is less than 30 atomic%, and preferably 20 atomic% or less. The hard mask film preferably has an O content of 5 atomic percent or less, and more preferably contains no O at all. Examples of materials that make up the hard mask film include Cr, CrO, CrN, and CrON, with CrN being preferred. The notation "CrON" refers to a material containing Cr, O, and N, and similar notations below have the same meaning.

[0053] The hard mask film may contain metallic elements other than Cr. Examples of metallic elements other than Cr include Al, Si, Ti, Y, Nb, Mo, Ta, Ru, and Hf. It is also preferable that the hard mask film does not contain metal elements other than Cr.

[0054] The thickness of the hard mask film is preferably 2 nm or more. The thickness of the hard mask film is preferably 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.

[0055] The dry etching rate of the hard mask film is the dry etching rate of the hard mask film (ER HM ) Dry etching rate of absorber film (ER ABS ), that is, ER ABS / ER HM However, it is preferable that the value be 5 or greater, and more preferably 10 or greater. There is no particular upper limit, but examples include 1000. The dry etching rates of the hard mask film and the absorber film are the etching rates under the gas and conditions used for dry etching the absorber film. More detailed conditions are as described in the examples.

[0056] The hard mask film preferably has low crystallinity, and more preferably is amorphous. When the crystallinity of the hard mask film is low, when etching the hard mask film, the boundary between the etched area and the non-etched area is less likely to become jagged, and a finer mask pattern can be formed.

[0057] 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 Cr film as a hard mask film, a Cr target can be used, and sputtering can be performed with Ar gas to form the hard mask film. Furthermore, when forming a hard mask film containing at least one element selected from the group consisting of N and O, it is sufficient to introduce at least one of N2 gas and O2 gas into the sputtering gas. By adjusting the amount of at least one of the above N2 gas and O2 gas 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.

[0058] [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"). The presence of 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 materials 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 materials of the conductive film may be a Cr compound containing Cr and one or more elements selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more elements 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. Furthermore, 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 the various films formed on the first main surface side. The conductive film can be formed using known film deposition methods, such as sputtering methods including DC sputtering, magnetron sputtering, and ion beam sputtering, as well as CVD, vacuum deposition, and electrolytic plating.

[0059] The reflective mask blank of the present invention can be manufactured, for example, by forming the multilayer reflective film on the substrate, forming an absorber film on the multilayer reflective film, and forming a hard mask film on the absorber film. Furthermore, if the reflective mask blank of the present invention has a protective film, it can be manufactured, for example, by forming the multilayer reflective film on the substrate, forming a protective film on the multilayer reflective film, and forming the absorber film on the protective film. The formation method for each layer is as described above.

[0060] <Method for manufacturing a reflective mask and the reflective mask itself> The reflective mask of the present invention is obtained by patterning the absorbent film of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be described with reference to Figure 2.

[0061] 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, an absorber film 18, and a hard mask film 20 in that order. A known method can be used to form the resist pattern 40. For example, a resist is applied to the hard mask film 20 of the reflective mask blank, and the resist pattern 40 is formed by exposure and development. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Subsequently, the hard mask film 20 is etched using the resist pattern 40 in Figure 2(a) as a mask, and the hard mask film is patterned to the shape corresponding to the resist pattern 40. Then, the resist pattern 40 is removed to obtain the laminate shown in Figure 2(b). The hard mask film 20 can be etched using a known method, such as dry etching using a chlorine-containing gas. Furthermore, the resist pattern 40 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.

[0062] Next, using the patterned hard mask film 20 shown in Figure 2(b) as a mask, the absorber film 18 is etched and patterned to obtain a laminate having the absorber film pattern 18pt shown in Figure 2(c). In the laminate shown in Figure 2(c), the protective film 16 is exposed. Dry etching for forming the absorber film pattern 18pt can be performed using, for example, a gas containing a fluorine compound (F-type gas). As described above, the reflective mask blank of the present invention has a high etching selectivity ratio, and in particular, the etching selectivity ratio is high when dry etching is performed using a gas containing a fluorine compound, making it easy to form the desired absorber film pattern 18pt. Examples of F-type gases include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, F2, SF6, and NF3, as well as mixtures thereof. If necessary, in addition to fluorine-based gases, active gases such as oxygen gas and chlorine gas, and inert gases such as nitrogen gas, helium gas, and argon gas may be mixed. Among these, it is preferable to include oxygen gas as the active gas. It is also preferable that the etching gas be converted into plasma and used to etch the absorber film 18.

[0063] Next, the hard mask film 20 is removed from the laminate shown in Figure 2(c) to obtain the laminate shown in Figure 2(d). The hard mask film 20 can be removed using the same method as the etching method for the hard mask film 20 described above.

[0064] Next, as shown in Figure 2(e), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 2(d), and dry etching is performed using the resist pattern 41 in Figure 2(e) as a mask. Dry etching is carried out until the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 2(f).

[0065] 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. [Examples]

[0066] The present invention will be described in more detail below based on examples. The materials, quantities, proportions, processing details, 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 1-11 are examples, and Examples 12-18 are comparative examples.

[0067] <Example 1> First, we will explain the procedure for obtaining the reflective mask blank shown in Example 1 as a representative example.

[0068] [substrate] First, a SiO2-TiO2 glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared as the substrate. This glass substrate has a thermal expansion coefficient of 0.02 × 10⁻¹⁰ at 20°C. -7 The temperature is / ℃, the Young's modulus is 67 GPa, the Poisson's ratio is 0.17, and the specific stiffness is 3.07 × 10⁻⁶. 7 m2 / 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 / □.

[0069] [Multilayer reflective film] Next, a Mo / Si multilayer reflective film was formed on the first main surface of the substrate as a multilayer reflective film. 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 then depositing a Si film (thickness 4.5 nm) after the 40th Mo film was 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).

[0070] [Protective film] On the multilayer reflective film formed using the above procedure, a Ru film (thickness 1.0 nm) and an Rh film (thickness 2.5 nm) were formed in that order as protective films. The Ru film and Rh film were formed by ion beam sputtering under the following conditions. Ru film deposition conditions: • Target: Ru target • Sputtering gas: Ar gas • Gas pressure: 0.027 Pa Ion acceleration voltage: 600V ·Deposition speed: 0.056nm / sec Rh film deposition conditions: • Target: Rh target • Sputtering gas: Ar gas • Gas pressure: 0.027 Pa Ion acceleration voltage: 600V ·Deposition speed: 0.077nm / sec

[0071] [Absorbing membrane] A PtW film (thickness 35 nm) was formed as an absorber film on the protective film formed by the above procedure. The PtW film was formed by DC sputtering under the following conditions. • Targets: Pt target, W target • Sputter gas: Ar gas ·Deposition speed: 0.20nm / sec • Power input density per target area: 4.9 W / cm² 2 (Pt target), 3.7 W / cm² 2 (Dual target)

[0072] [Hard mask film] A CrN film (thickness 15 nm) was formed as a hard mask film on the absorber film formed using the above procedure. The CrN film was formed by reactive sputtering under the following conditions. • Target: Cr target • Sputtering gas: Ar gas and N2 gas (flow ratio: Ar gas:N2 gas = 20:1) ·Deposition speed: 0.031nm / sec • Power input density per target area: 4.1 W / cm² 2

[0073] <Examples 2-18> The reflective mask blanks in Examples 2-18 were obtained in the same manner as in Example 1, except that the compositions of the absorber membrane and hard mask membrane were as shown in the table below.

[0074] <Evaluation Methods and Criteria> [Composition and film thickness of each layer] The chemical composition of the absorber membrane was measured using the XPS method described above with an ULVAC-PHI X-ray photoelectron spectrometer (PHI 5000 VersaProbe). The film thickness of each membrane was measured using the XRR method described above.

[0075] [Optical constants] The refractive index n and extinction coefficient k were calculated using the method described above.

[0076] [Etching rate and etching selectivity] Samples for etching rate measurement were prepared by forming only the absorber film and hard mask film, respectively, on a substrate using a reflective mask blank, and the etching rates of the absorber film and hard mask film were measured. Specifically, the above-mentioned etching rate measurement sample was etched by generating plasma using an inductively coupled plasma (ICP) generator and irradiating it with the plasma. The specific etching conditions are as follows. Antenna RF power output: 1200W • Bias RF power output: 50W Etching gas pressure: 1.0 Pa • Etching gas flow rate: CF4 / O2 mixed gas The film thickness before and after etching under the above conditions was measured using XRR, and the etching rate (E / R, unit: nm / min) was calculated by dividing the change in film thickness by the etching time.

[0077] The E / R ratio of the absorber membrane was evaluated using the following criteria. "A": E / R is 25.0 nm / min or higher "B": E / R is between 10.0 nm / min and less than 25.0 nm / min "C": E / R is less than 10.0 nm / min

[0078] The etching selectivity ratio = (E / R of absorber film) / (E / R of hard mask film) was calculated from the E / R of the absorber film and the E / R of the hard mask film, and the etching selectivity ratio was evaluated according to the following evaluation criteria. For practical purposes, an etching selectivity ratio of B or higher is preferable. "A": Etching selectivity ratio is 10 or higher. "B": Etching selectivity ratio is 3 or greater, and less than 10. "C": Etching selectivity is less than 3.

[0079] <Result> The composition and characteristics of the absorber membrane of each example's reflective mask blank, the composition of the hard mask membrane, and the evaluation results are shown in Table 2 below. In Table 2, the "M" column shows the value of M calculated from the above formula (1).

[0080] [Table 2]

[0081] The results shown in Table 1 demonstrate that by using an absorber film containing Pt and metal element X, where the total content of metal element X is 5 atomic percent or more relative to the total content of Pt and metal element X, and a hard mask film containing Cr at a ratio of 70 atomic percent or more relative to the total atoms of the hard mask film, a reflective mask blank with a large ratio of the etching rate of the absorber film to the etching rate of the hard mask film during etching of the absorber film can be obtained (Examples 1 to 11). On the other hand, when the content of metal element X in the absorber film was less than a predetermined amount, or when the content of Cr in the hard mask film was less than a predetermined amount, the etching selectivity ratio was small (Examples 12 to 18). When metal element X contains W, it was confirmed that a suitable refractive index n and extinction coefficient k are observed when the W content in the absorber film is 80 atomic percent or less relative to the total atoms of the absorber film (Example 13). When metal element X contains W, it was confirmed that the etching rate and etching selectivity of the absorber film are superior when the W content in the absorber film is 35 atomic percent or more relative to the total atoms of the absorber film (Examples 1 and 2). When the metal element X contains Ta, it was confirmed that a suitable refractive index n is observed when the Ta content in the absorber film is between 5 atomic% and 65 atomic% relative to the total atoms of the absorber film (Example 14). When metal element X contains Ta, it was confirmed that the etching rate and etching selectivity of the absorber film are superior when the Ta content in the absorber film is 40 atomic percent or more relative to the total atoms of the absorber film (Examples 7, 8). [Explanation of Symbols]

[0082] 10 Reflective Mask Blanks 12 circuit boards 14 Multilayer reflective film 16 Protective film 18 Absorbent membrane 18pt Absorber membrane pattern 20 Hard mask film 40,41 Resist Pattern

Claims

1. circuit board and A multilayer reflective film that reflects EUV light, Absorbent membrane and A reflective mask blank having a hard mask film in this order, The absorber film comprises platinum and at least one metallic element X selected from the group consisting of tantalum and tungsten. The total content of the metal element X in the absorber membrane is 5 atomic percent or more relative to the total content of platinum and the metal element X. The hard mask film contains chromium, A reflective mask blank in which the chromium content in the hard mask film is 70 atomic percent or more relative to the total atoms of the hard mask film.

2. The reflective mask blank according to claim 1, wherein the value of M determined by formula (1) in the absorbent membrane is 550°C or less. [Math 1] In formula (1), M ｉ The i-th metal element A is one of the n metal elements contained in the absorber membrane. ｉ The melting point of the fluoride is shown, c ｉ This is the total content of all metal elements contained in the absorber membrane, and the metal element A ｉ This indicates the atomic ratio of the content, where i is an integer between 1 and n, and n is an integer of 2 or greater.

3. The reflective mask blank according to claim 1 or 2, wherein the absorbent film further comprises at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon.

4. The aforementioned metal element X includes tungsten, The reflective mask blank according to claim 1 or 2, wherein the tungsten content in the absorbent membrane is 80 atomic percent or less relative to the total atoms of the absorbent membrane.

5. The aforementioned metal element X includes tantalum, The reflective mask blank according to claim 1 or 2, wherein the tantalum content in the absorbent membrane is 5 atomic percent or more and 60 atomic percent or less with respect to the total atoms of the absorbent membrane.

6. The refractive index of the absorber film at a wavelength of 13.5 nm is 0.930 or less. The reflective mask blank according to claim 1 or 2, wherein the extinction coefficient of the absorber film at a wavelength of 13.5 nm is 0.040 or greater.

7. The absorbent film has a second absorbent film on the surface facing the multilayer reflective film, The reflective mask blank according to claim 1 or 2, wherein the second absorber film comprises at least one element selected from the group consisting of ruthenium, chromium, and tantalum, and at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon.

8. A protective film is further provided between the absorbent film and the anti-reflective film. The reflective mask blank according to claim 1 or 2, wherein the rhodium content in the protective film is 50 atomic percent or more relative to the total atoms of the protective film.

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

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

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