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

Abstract

To provide a reflective mask blank in which, when etching the absorber film, the etching selectivity ratio of the absorber film to the hard mask film is increased, and the occurrence of side etching is suppressed. [Solution] 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, wherein the absorber film contains ruthenium and at least one of platinum and iridium, and satisfies requirement 1 or requirement 2 below. Requirement 1: The hard mask film contains chromium, and the chromium content is 70 atomic percent or more of the total atoms of the hard mask film. Requirement 2: The hard mask film mentioned above contains aluminum.

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.

[0005] As for the material of the absorber membrane mentioned above, for example, Patent Document 1 discloses a material containing platinum (Pt) and ruthenium (Ru). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-119143 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The above-mentioned literature discloses absorber films containing Pt and Ru, but their etching characteristics are not specifically investigated. Furthermore, when etching absorber films, a hard mask film may be patterned, and the hard mask film pattern may be used as a mask to etch the absorber film. When the inventors attempted to etch an absorber film containing Pt and Ru with a gas containing a fluorine compound, they found that depending on the material of the hard mask film, the etching selectivity ratio was low, and the hard mask film pattern did not function as an etching mask for the absorber film, indicating that improvement was needed. Furthermore, during etching of the absorber film, a phenomenon sometimes occurred in which the absorber film located below the non-openings of the mask was etched in the in-plane direction (hereinafter also referred to as "side etching"). When side etching occurs, the absorber film is etched into a shape different from that of the etching mask film, so it is preferable to suppress side etching.

[0008] The present invention has been made in view of the above problems, and aims to provide a reflective mask blank in which, when etching the absorber film, the etching selectivity ratio of the absorber film to the hard mask film is increased, and the occurrence of side etching is suppressed. Furthermore, the present invention also aims to provide a reflective mask and a method for manufacturing a reflective mask. [Means for solving the problem]

[0009] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that when the hard mask film contains a predetermined element in a predetermined ratio or higher, or when the hard mask film contains a predetermined element, the etching selectivity ratio with the absorber film containing Ru increases, and when the absorber film contains at least one of Pt and iridium (Ir), side etching is suppressed, leading to the completion of the present invention.

[0010] 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, an absorber film, and a hard mask film, in this order, which is a reflective mask blank, where the absorber film contains ruthenium and at least one of platinum and iridium, a reflective mask blank that satisfies the following requirement 1 or requirement 2. Requirement 1: The hard mask film contains chromium, and the chromium content is 70 atomic% or more with respect to all atoms of the hard mask film. Requirement 2: The hard mask film contains aluminum. 〔2〕 The reflective mask blank according to 〔1〕, wherein the hard mask film contains nitrogen. 〔3〕 When the metal elements contained in the absorber film are defined as a metal element group MA, G, which is the sum of the calculated values obtained by multiplying the standard Gibbs energy of formation of the oxide of each metal element in the metal element group MA by the atomic ratio of the content of each metal element in the metal element group MA to the total content of the metal element group MA, ABS is -230.0 kJ / mol or more, which is the reflective mask blank according to 〔1〕 or 〔2〕. 〔4〕 The reflective mask blank according to any one of 〔1〕 to 〔3〕, wherein the absorber film contains platinum. 〔5〕 The reflective mask blank according to any one of 〔1〕 to 〔4〕, wherein the absorber film further contains at least one element selected from the group consisting of boron, carbon, nitrogen, and oxygen. 〔6〕 The reflective mask blank according to any one of 〔1〕 to 〔5〕, wherein the absorber film contains platinum and the platinum content is 15 atomic% or more with respect to all atoms of the absorber film. 〔7〕 The reflective mask blank according to any one of ί1〕 to 〔6〕, wherein the absorber film contains iridium and the iridium content is 20 atomic% or more with respect to all atoms of the absorber film. 〔8〕 The reflective mask blank according to any one of 〔1〕 to 〔7〕, further having a protective film between the multilayer reflective film and the absorber film. [9] The reflective mask blank described in [8], wherein the protective film contains rhodium.

[10] A reflective mask having an absorbent membrane pattern formed by patterning the absorbent membrane of the reflective mask blank described in any one of [1] to [9].

[11] A method for manufacturing a reflective mask, comprising the step of patterning the absorbent membrane of a reflective mask blank described in any one of [1] to [9]. [Effects of the Invention]

[0011] According to the present invention, when etching the absorber film, the etching selectivity ratio of the absorber film to the hard mask film is increased, and the occurrence of side etching is suppressed, thereby providing a reflective mask blank. Furthermore, the present invention can also provide a reflective mask and a method for manufacturing a reflective mask. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. [Figure 2] This is a cross-sectional view showing an example of the manufacturing process for a reflective mask using the reflective mask blank of the present invention. [Modes for carrying out the invention]

[0013] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0014] The meaning of each term used in this specification is shown below. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, tantalum, rhenium, iridium, and platinum may be represented by their corresponding element symbols (B, C, N, O, Si, Ti, Cr, Zr, Nb, Mo, Ru, Rh, Pd, Ta, Re, Ir, and Pt, etc.).

[0015] In this specification, the standard Gibbs free energy of formation of an oxide of a metal element refers to the standard free energy required to produce a metal oxide containing 1 mole of the metal element by combining the metal element with oxygen under standard conditions (298.15 K (25°C), 1 atm (101325 Pa)). For example, since the chemical formula Cr2O3 contains 2 atoms of Cr, the standard Gibbs free energy of formation of Cr oxide (Cr2O3) is calculated by dividing the standard Gibbs free energy of Cr2O3 by 2. Unless otherwise specified, the term "metal oxide" refers to the oxide of the metal element that is most stable under standard conditions.

[0016] In this specification, the standard Gibbs free energy of formation for oxides of metallic elements is as given in the values ​​listed in "Chemical Handbook," 4th revised edition, Basic Volume II, edited by The Chemical Society of Japan, Maruzen Co., Ltd., September 30, 1993, pp. 285-294. For standard Gibbs free energy of formation of oxides of metallic elements not listed in the above literature, the literature values ​​can be used. For example, in this specification, the standard Gibbs free energy of formation for oxides of the following metal elements shall be the values ​​shown below, based on the respective references listed below. • Ru: -253.0 kJ / mol (See Japanese Patent Publication No. 2024-038390, paragraphs 0037-0040) • Ir: -193.0 kJ / mol (See Japanese Patent Publication No. 2024-038390, paragraphs 0037-0040) • Pt: -81.0 kJ / mol (See Japanese Patent Publication No. 2023-141692, paragraph 0072)

[0017] <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. Furthermore, the absorber film contains Ru and at least one of Pt and Ir, and satisfies requirement 1 or 2 below. Requirement 1: The hard mask film contains chromium, and the chromium content is 70 atomic percent or more of the total atoms of the hard mask film. Requirement 2: The hard mask film contains aluminum. The reflective mask blank of the present invention will be described with reference to the drawings.

[0018] Figure 1 is a 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 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 this order. The absorber membrane 18 comprises Ru and at least one of Pt and Ir. The hard mask membrane 20 satisfies requirement 1 or 2 described above. The reflective mask blank 10 shown in Figure 1 may have a conductive film, described later, on the side of the substrate 12 opposite to the multilayer reflective film 14. Furthermore, although the reflective mask blank 10 shown in Figure 1 has a protective film 16, the protective film 16 may be omitted.

[0019] In the reflective mask blank of the present invention, the mechanism by which the etching selectivity ratio of the absorber film to the hard mask film increases and the occurrence of side etching is suppressed when etching the absorber film is not entirely clear, but the inventors speculate as follows. When etching the absorber film of a reflective mask blank with a hard mask film, the hard mask film is usually patterned first to obtain a hard mask film pattern. Then, the absorber film is etched using the hard mask film pattern as a mask. Ru compounds (e.g., Ru oxides) are generated during etching through the chemical action of the etchant. These generated Ru compounds volatilize, making etching more likely to proceed in the in-plane direction. On the other hand, Pt or Ir have high chemical stability and do not easily generate volatile compounds. Therefore, it is thought that absorber films containing Pt or Ir suppress the occurrence of side etching. In this case, when etching an absorber film containing Pt or Ir in addition to Ru, it is preferable to perform the etching with a gas containing a fluorine compound. When etching with the gas described above, we found that if the hard mask film contains Cr and the Cr content is 70 atomic percent or more of the total atoms of the hard mask film (satisfying requirement 1), the boiling point of the Cr fluoride generated during etching is high, making it difficult to etch the hard mask film, and thus increasing the etching selectivity ratio. Furthermore, we found that, similar to the case where requirement 1 is met, when the hard mask film contains Al, the boiling point of the Al fluoride generated during etching is high, making the hard mask film difficult to etch and increasing the etching selectivity ratio.

[0020] The configuration of the reflective mask blank of the present invention will be described below. In the following, when etching the absorber film, a high etching selectivity ratio of the absorber film to the hard mask film will also be simply referred to as "high etching selectivity."

[0021] [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.

[0022] 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, in order to improve the pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. In a predetermined area of ​​the first main surface of the substrate (for example, an area of ​​132 mm × 132 mm), the flatness is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate are determined as appropriate based on the design values ​​of the mask, etc. For example, the outer dimensions may be 6 inches (152 mm) square and the thickness 0.25 inches (6.3 mm). Circuit boards are often rectangular or square in shape. Furthermore, the substrate preferably has high rigidity in order to prevent deformation due to film stress of the film (multilayer reflective film, absorber film, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0023] [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 of the EUV mask blank. The multilayer reflective film preferably has a high reflectivity to EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity of EUV light around a wavelength of 13.5 nm 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.

[0024] 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 a high refractive index layer and a low refractive index layer in that order from the substrate side, with each stacking period comprising multiple cycles, or by stacking a low refractive index layer and a high refractive index layer in that order, with each stacking period comprising multiple cycles. A layer containing Si can be used as the high refractive index layer. In addition to pure Si, Si compounds containing one or more elements selected from the group consisting of B, C, N, and O can be used as the Si-containing material. By using a high refractive index layer containing Si, a reflective mask with excellent EUV light reflectivity can be obtained. As the low refractive index layer, a layer containing a 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.

[0025] 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 film material used and the required EUV light reflectance of the reflective layer. Taking a Mo / Si multilayer reflective film as an example, 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. It is preferable that the multilayer reflective film has a reflectance of 60% or more for EUV light with an incident angle θ of 6°. More preferably, the above reflectance is 65% or more.

[0026] 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. When the multilayer reflective film is a Mo / Si multilayer reflective film, for example, using ion beam sputtering, first a Si layer of a predetermined thickness is deposited on the 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.

[0027] [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 is removed.

[0028] Materials that can achieve the above objective include materials containing at least one element selected from the group consisting of Si, Ru, and Rh. That is, the protective film preferably contains at least one element selected from the group consisting of Si, Ru, and Rh. Furthermore, the protective film preferably contains Rh. If the protective film contains Rh, it is also preferable that it contains 50 atomic percent or more of Rh relative to the total atoms of the protective film. More specifically, the above 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, and elemental Rh metal, 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 improve reflectivity to EUV light. Adding Ta, Ir, Pd, or Y to Rh can improve resistance to etching processes. Furthermore, examples of materials that can achieve the above objectives include Al, nitrides containing these metals and nitrogen, and Al2O3. Among these, Ru elemental metal, Ru alloy, Rh elemental metal, or Rh alloy are preferred materials that can achieve the above objectives.

[0029] If the protective film contains Ru or Rh, the protective film may also contain at least one element selected from the group consisting of B, C, N, and O.

[0030] 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. Detailed information on the XPS measurement method will be provided later.

[0031] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In order to maintain 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, 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, from the standpoint of obtaining good etching resistance. It is also 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 is the preferred thickness described above. The thickness of the protective film is determined by the X-ray reflectivity method (XRR).

[0032] 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 preferred material described above. Furthermore, if the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within 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.

[0033] 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.

[0034] [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 the absorber film is patterned. A 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 while interfering with EUV light from a multilayer reflective film to produce contrast. The absorber membrane pattern may be used as a binary mask as described later, or as a phase-shift mask as described later. In other words, the absorber membrane may be a phase-shift membrane. The absorbent membrane, as described above, includes Ru and at least one of Pt and Ir.

[0035] The Ru content in the absorber membrane is preferably 5 atomic% or more, more preferably 8 atomic% or more, may be 12 atomic% or more, may be 15 atomic% or more, may be 20 atomic% or more, may be 30 atomic% or more, may be 40 atomic% or more, or may be 45 atomic% or more, relative to the total atoms contained in the absorber membrane. Furthermore, the Ru content in the absorber membrane is preferably 90 atomic% or less, more preferably 80 atomic% or less, even more preferably 70 atomic% or less, and particularly preferably 60 atomic% or less, in terms of further suppressing side etching.

[0036] The absorber film preferably contains Pt. As mentioned above, when the absorber film contains Pt, the side etching described above is more easily suppressed. The absorbent membrane contains Pt, and it is preferable that the Pt content is 10 atomic% or more, more preferably 15 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 absorbent membrane. The absorbent membrane contains Pt, and it is preferable that the Pt content is 90 atomic% or less, more preferably 80 atomic% or less, even more preferably 70 atomic% or less, particularly preferably 60 atomic% or less, and most preferably 50 atomic% or less, relative to the total atoms of the absorbent membrane.

[0037] The absorber film may also preferably contain Ir. As mentioned above, when the absorber film contains Ir, the side etching described above is more easily suppressed. The absorbent membrane contains Ir, and it is preferable that the Ir content is 10 atomic percent or more, more preferably 15 atomic percent or more, even more preferably 20 atomic percent or more, and particularly preferably 30 atomic percent or more, relative to the total atoms of the absorbent membrane. It is also preferable that the absorbent membrane contains Ir, and the Ir content is 90 atomic percent or less, relative to the total atoms of the absorbent membrane.

[0038] The absorber membrane may contain elements other than Ru, Pt, and Ir. Elements other than Ru, Pt, and Ir include other metallic elements and nonmetallic elements. Other metallic elements include one or more elements selected from the group consisting of W, Ta, Nb, Mo, and Pd. The content of other metallic elements in the absorber membrane is preferably 10 atomic% or less, more preferably 5 atomic% or less, and even more preferably 3 atomic% or less, relative to the total atoms of the absorber membrane. It is also preferable that the absorber membrane does not contain the above-mentioned other metallic elements. That is, the content of other metallic elements in the absorber membrane may be 0 atomic% relative to the total atoms of the absorber membrane. Examples of nonmetallic elements include one or more elements selected from the group consisting of B, C, N, and O. In particular, it is preferable that the absorber membrane contains one or more elements selected from the group consisting of B and N as nonmetallic elements. When the absorber membrane contains nonmetallic elements, the content is preferably 15 atomic% or less, more preferably 10 atomic% or less, and even more preferably 5 atomic% 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% or more, and more preferably 1 atomic% or more, relative to the total atoms of the absorber membrane. When the absorber membrane contains nonmetallic elements, the crystallinity of the absorber membrane tends to decrease.

[0039] The types and amounts of elements contained in the absorber membrane can be measured using the same method as for the protective membrane (XPS method). Detailed measurement methods are described below.

[0040] 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 a reflective mask blank. The obtained measurement sample is then placed in a measurement holder so that the hard mask film side becomes the measurement surface. After the measuring holder is loaded into the apparatus, if another layer is located on the side opposite the substrate side of the absorber film, the other layer is removed with an Ar ion beam to expose the absorber film. After the absorber film is exposed, the absorber film is removed from its outermost surface to a thickness equal to half the film 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., Ru and Pt). 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.

[0041] Further, when the metal element group MA is a group consisting of all the metal elements contained in the absorber film, G is a value obtained by summing up the calculated values obtained by multiplying the standard Gibbs energy of formation of the oxide of each metal element in the metal element group MA by the atomic ratio of the content of each metal element in the metal element group MA in the absorber film to the total content of the metal element group MA in the absorber film. ABS It is also preferable that G is -230.0 kJ / mol or more. ABS When it is within the above range, the above-described side etching is likely to be suppressed, which is preferable. Incidentally, G ABS is the value of the standard Gibbs energy of formation of the oxide of the metal element in the metal element group MA when the metal element group MA consists of only one kind of metal element.

[0042] Regarding the above G ABS more specifically, when the absorber film contains, as the metal element group MA, the metal element M1, the metal element M2,..., the metal element M n (n is a positive integer of 1 or more), it is calculated by the following formula (a).

[0043]

Equation

[0044] In formula (a), G i is the standard Gibbs energy of formation of the oxide of the metal element M i . In formula (a), c i is the atomic ratio of the content of the metal element M i to the total content of the metal element group MA.

[0045] Hereinafter, as an example, when the absorber film contains Ru and Pt as the metal element group MA and the ratio of the content of Ru in the absorber film to the total content of Ru and Pt in the absorber film is 65 atomic%, the calculation of G ABS will be described. First, the standard Gibbs energy G of Ru oxide (RuO2) RuThe calculated value is obtained by multiplying by 0.65. Next, the standard Gibbs free energy of formation G of Pt oxide (PtO2) is calculated. Pt Multiply this by 0.35 to calculate the value. Add the two calculated values ​​above and G ABS Calculate G ABS is 0.65 × G Ru +0.35×G Pt It is calculated as follows.

[0046] G calculated using the above procedure ABS As mentioned above, the value of is preferably -230.0 kJ / mol or higher, and more preferably -200.0 kJ / mol or higher. ABS The value is often 0.0 kJ / mol or less.

[0047] When using an absorber film pattern as a binary mask, the absorber film must absorb EUV light and have a low reflectivity of EUV light. Specifically, when EUV light is shone onto the surface of the absorber film, the maximum reflectivity of EUV light around 13.5 nm should ideally be 2% or less. Furthermore, it is preferable that the absorber membrane does not contain the metal elements found in the hard mask membrane. The crystalline state of the absorber membrane is preferably amorphous. This improves the smoothness and flatness of the absorber membrane. Furthermore, higher smoothness and flatness of the absorber membrane reduce the edge roughness of the absorber membrane pattern, thereby improving the dimensional accuracy of the absorber membrane pattern. 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.

[0048] When using an absorber film pattern as a phase shift mask, the reflectivity of the absorber film to EUV light is preferably 2% or higher. To obtain a sufficient phase shift effect, the reflectivity of the absorber film is preferably 9-15%. Using an absorber film as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. Furthermore, it is preferable that the absorber membrane does not contain the metal elements found in the hard mask membrane. When using an absorber film pattern as a phase shift mask, the thickness of the absorber film is preferably 30 to 75 nm, and more preferably 35 to 55 nm. The thickness of the absorber film can be determined by the X-ray reflectance method.

[0049] The refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.885 or higher, and more preferably 0.890 or higher. 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 0.920 or lower, more preferably 0.910 or lower, and even more preferably 0.900 or lower, as this allows for a thinner phase-shift film. The extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.060 or less, more preferably 0.058 or less, and even more preferably 0.055 or less. When the absorber film is used as a phase-shift film, the extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.010 or more, more preferably 0.015 or more, and even more preferably 0.020 or more, as this makes it easier to adjust the reflectance of the phase-shift film to a lower value.

[0050] The refractive index n and extinction coefficient k mentioned above can be taken from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or from the "dependence of reflectance on the angle of incidence" 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-cos2θ)1 / 2) / (sinθ+((n+ik)2-cos2θ)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 them and equation (1), the refractive index n and extinction coefficient k can be calculated.

[0051] The crystalline state of the absorber membrane is preferably amorphous. This improves the smoothness and flatness of the absorber membrane. Furthermore, higher smoothness and flatness of the absorber membrane reduce the edge roughness of the absorber membrane pattern, thereby improving the dimensional accuracy of the absorber membrane pattern.

[0052] The absorber film may be a single layer or a multilayer film consisting of multiple layers. If the absorber film is a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. If the absorber film is a multilayer film, the layer located 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 (for example, wavelength 193-248 nm). Examples of materials used to form the anti-reflective coating include materials containing Ta and O.

[0053] Absorber films can be formed using known film deposition methods such as magnetron sputtering and ion beam sputtering. For example, when forming a RuPt film as an absorber film using magnetron sputtering, a Ru target and a Pt target are used, and sputtering is performed with a gas containing Ar gas to deposit the absorber film. Alternatively, a RuPt alloy target may be used to form the RuPt film.

[0054] [Hard mask film] The reflective mask blank of the present invention includes a hard mask film. The hard mask film satisfies either requirement 1 or requirement 2 below, as described above. Requirement 1: The hard mask film contains chromium, and the chromium content is 70 atomic percent or more of the total atoms of the hard mask film. Requirement 2: The hard mask film contains aluminum.

[0055] If the hard mask film satisfies requirement 1, the Cr content is 70 atomic percent or more relative to the total atoms of the hard mask film, may be 80 atomic percent or more, or 85 atomic percent or more. The Cr content is preferably 99 atomic percent or less, and more preferably 95 atomic percent or less, relative to the total atoms of the hard mask film.

[0056] If the hard mask film satisfies requirement 2, the Al content is preferably 40 atomic% or more, more preferably 50 atomic% or more, and even more preferably 60 atomic% or more, relative to the total atoms of the hard mask film. The Al content is preferably 99 atomic% or less, and more preferably 95 atomic% or less, relative to the total atoms of the hard mask film.

[0057] If the hard mask film satisfies requirement 1, it may contain elements other than Cr. Elements other than Cr that may be included in the hard mask film include B, C, and N, with N being preferred. Furthermore, if the hard mask film satisfies requirement 2, it may contain elements other than Al. Other elements that may be included in the hard mask film besides Al include N and O, with N being preferred. In other words, the hard mask film preferably contains N.

[0058] If the hard mask film satisfies requirement 1, it is preferable that the hard mask film contains N. If the hard mask film contains N, the N content is 30 atomic percent or less, may be 20 atomic percent or less, or 15 atomic percent or less, relative to the total atoms of the hard mask film. If the hard mask film contains N, the N content is preferably 1 atomic percent or more, and more preferably 5 atomic percent or more.

[0059] If the hard mask film satisfies requirement 2, it is preferable that the hard mask film contains N. If the hard mask film contains N, the N content is preferably 50 atomic% or less, may be 40 atomic% or less, or 30 atomic% or less, relative to the total atoms of the hard mask film. If the hard mask film contains N, the N content is preferably 1 atomic% or more, more preferably 5 atomic% or more.

[0060] The oxygen content in the hard mask film is preferably 1 atom% or less relative to the total atoms of the hard mask film, and may even be 0 atom%. In other words, it is also preferable that the hard mask film does not contain oxygen.

[0061] The types of elements contained in the hard mask film and their content can be measured by the same method as described above for the absorber film.

[0062] The thickness of the hard mask film is preferably 3 nm or more, and more preferably 5 nm or more, as this facilitates the formation of fine mask patterns. The thickness of the hard mask film may also be 10 nm or more, or even 15 nm or more. The thickness of the hard mask film is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less. The thickness of the hard mask film can be measured using the same method as for the protective film. The thickness of the hard mask film can be set according to the ratio of the etching rates mentioned above.

[0063] 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 defined as the etching rates under the gas and conditions used for dry etching the absorber film. More detailed conditions are described in the examples.

[0064] The crystallinity of the hard mask film is preferably low, and it is also preferable that it be amorphous. When the crystallinity of a hard mask film is low, roughness is less likely to occur at the boundary between the etched and non-etched areas during etching, allowing for the formation of finer mask patterns. The degree of roughness at the boundary is also called edge roughness.

[0065] 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 CrN film as a hard mask film, a Cr target can be used, and the CrN film can be formed by magnetron sputtering while supplying nitrogen gas and Ar gas.

[0066] [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 (second main surface). By providing a conductive film, the reflective mask blank can 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.

[0067] <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.

[0068] 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.

[0069] 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 an absorber film pattern of 18pt can be performed using F-type gas (a gas containing fluorine compounds). 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. In the reflective mask blank of the present invention, when forming the absorber film pattern 18pt, the etching selectivity ratio of the absorber film 18 to the hard mask film 20 is large, making it easy to form the desired absorber film pattern 18pt.

[0070] 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.

[0071] 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).

[0072] The reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention can be suitably applied as a reflective mask used for exposure with EUV light. [Examples]

[0073] 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 to 12, described later, are examples, while Examples 13 to 17 are comparative examples.

[0074] <Example 1> First, we will explain the procedure for obtaining the reflective mask blank shown in Example 1 as a representative example.

[0075] [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 m 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 / □.

[0076] [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).

[0077] [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

[0078] [Absorbing membrane] A RuPt film (thickness 35 nm) was formed as an absorber film on the protective film formed by the above procedure. The RuPt film was formed by DC sputtering under the following conditions. • Targets: Ru target, Pt target • Sputter gas: Ar gas ·Deposition speed: 0.25nm / sec • Power input density per target area: 9.0 W / cm² 2 (Ru target), 1.2 W / cm² 2 (Pt target)

[0079] [Hard mask film] A CrN film (thickness 15 nm) was formed as a hard mask film on the absorber film formed by 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

[0080] Following the above procedure, the reflective mask blank for Example 1 was obtained. The elemental ratios of the absorber film and hard mask film of the obtained reflective mask blanks were measured using the method described above, and the values ​​are shown in the table below.

[0081] <Examples 2-17> The reflective mask blanks in Examples 2-17 were obtained in the same manner as in Example 1, except that the types of absorber membranes and hard mask membranes were as shown in the table below. The elemental ratios of the absorber membranes and hard mask membranes of the obtained reflective mask blanks were measured using the method described above, and the values ​​were as shown in the table below. In Example 8, the absorber film of the reflective mask blank was deposited by introducing N2 gas into the sputtering gas. In Example 9, the absorber film of the reflective mask blank was deposited using a RuB target and a Pt target as targets. The absorber films of the reflective mask blanks in Examples 11 and 12 were deposited using Ru targets and Ir targets, respectively.

[0082] <Rating> [Side etching] For the reflective mask blanks of Examples 1-15, a line-and-space pattern was formed on the hard mask film, and the hard mask film was processed into a line-and-space pattern to form a hard mask film pattern. Next, using the hard mask film pattern as a mask, the absorber film was patterned using an Induced Coupled Plasma (ICP) generator. ICP antenna bias output: 1200W Board bias output: 50W Etching gas: A mixture of CF4 gas and O2 gas. Etching pressure: 1.0 × 10 0 Pa

[0083] After etching the absorber film of each reflective mask blank under the above conditions, the cross-section of the reflective mask blank was observed using a transmission electron microscope. Specifically, thin section samples with the cross-section perpendicular to the longitudinal direction of the line-and-space pattern exposed were prepared using a Helios1200 from FEI Japan. More specifically, thin section samples with a thickness of 50-100 nm were prepared by irradiating them with a Ga ion beam. The thin section samples described above were observed using a transmission electron microscope. A JEOL ARM200F transmission electron microscope was used, with an acceleration voltage of 200kV. In the observed image (dark-field image), the distance in the substrate plane between the edge of the hard mask film pattern and the surface position located furthest inside the absorber film pattern was measured. This observation was performed in 10 fields of view, and the average distance of these 10 locations was defined as the side etching amount. Based on the amount of side etching, the degree of side etching was evaluated according to the following criteria. A rating of A is preferred. A: Side etching amount is less than 5nm B: Side etching amount is 5nm or more

[0084] [Etching rate] Furthermore, measurement samples were prepared in which only the absorber film formed on each reflective mask blank was formed on the substrate under the same conditions, and measurement samples were prepared in which only the hard mask film was formed on the substrate under the same conditions, and etching was performed under the same conditions as for the side etching described above. The etching rates of the absorber film and the hard mask film were calculated from the changes in film thickness before and after etching. Film thickness before and after etching was measured using XRR. The etching selectivity ratio of the absorber film to the hard mask film was calculated from the obtained etching rates. The etching selectivity was evaluated according to the following criteria. A rating of A is preferable in practical applications. A: Etching selectivity ratio of 5.0 or higher B: Etching selectivity is less than 5.0

[0085] <Measurement> Using the measurement sample from which the etching rate was measured, the refractive index n and extinction coefficient k of the absorber film were measured by the method described above. Furthermore, from the elemental ratios measured by the method described above, G ABS The value was calculated. The measurement results mentioned above are also shown in the table below.

[0086] <Result> The compositions of the absorber film and hard mask film in the reflective mask blanks for each example, along with the measurement results and evaluation results described above, are shown in Table 1 below.

[0087] [Table 1]

[0088] As shown in Table 1, the reflective mask blanks of the present invention (Examples 1 to 12), in which the absorber film contains Ru and at least one of Pt and Ir, and which satisfy requirement 1 or 2 above with respect to the hard mask film, were found to have a higher etching selectivity ratio of the absorber film to the hard mask film when etching the absorber film. On the other hand, when the hard mask film did not satisfy requirements 1 and 2 above (Examples 13 to 15), the etching selectivity ratio of the absorber film to the hard mask film was not greater than that of the reflective mask blank of the present invention when etching the absorber film. Furthermore, a comparison of the reflective mask blanks of Examples 16 and 17 with the reflective mask blanks of the present invention (Examples 1 to 12) revealed that side etching is less likely to occur when the absorber film contains Ru and at least one of Pt and Ir. [Explanation of Symbols]

[0089] 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 membrane comprises ruthenium and at least one of platinum and iridium. A reflective mask blank that meets either requirement 1 or requirement 2 below. Requirement 1: The hard mask film contains chromium, and the chromium content is 70 atomic percent or more of the total atoms of the hard mask film. Requirement 2: The hard mask film contains aluminum.

2. The reflective mask blank according to claim 1, wherein the hard mask film contains nitrogen.

3. When the metal elements contained in the absorber membrane are designated as the metal element group MA, G is the sum of the calculated values ​​obtained by multiplying the standard Gibbs free energy of formation of the oxide of each metal element in the metal element group MA by the atomic ratio of each metal element in the metal element group MA to the total content of the metal element group MA. ＡＢＳ A reflective mask blank according to claim 1 or 2, wherein the concentration is -230.0 kJ / mol or higher.

4. The reflective mask blank according to claim 1 or 2, wherein the absorbent membrane contains platinum.

5. 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 boron, carbon, nitrogen, and oxygen.

6. The reflective mask blank according to claim 1 or 2, wherein the absorbent film contains platinum, and the platinum content is 15 atomic percent or more relative to the total atoms of the absorbent film.

7. The reflective mask blank according to claim 1 or 2, wherein the absorbent film contains iridium, and the iridium content is 20 atomic percent or more relative to the total atoms of the absorbent film.

8. The reflective mask blank according to claim 1 or 2, further comprising a protective film between the multilayer reflective film and the absorbent film.

9. The reflective mask blank according to claim 8, wherein the protective film contains rhodium.

10. 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.

11. 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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