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

Abstract

To provide a reflective mask blank including a phase shift film with reduced side etching.SOLUTION: A reflective mask blank has, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film, and a phase shift film, wherein the phase shift film contains Cr and B, and the content of N in the phase shift film is less than 10 atom% relative to all atoms in the phase shift film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, in order to further miniaturize semiconductor devices, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been considered.

[0003] Due to the characteristics of EUV light, EUV exposure uses a reflective optical system and a reflective mask. A reflective mask has a multilayer reflective film that reflects EUV light formed on a substrate, and an absorber film that absorbs EUV light is patterned on the multilayer reflective film.

[0004] EUV light incident on a reflective mask from the illumination optical system of an exposure tool is reflected by areas without an absorber film (openings) and absorbed by areas with an absorber film (non-openings). As a result, the mask pattern is transferred as a resist pattern onto a wafer through the reduced projection optical system of the exposure tool, and subsequent processing is carried out. The absorber film may also be a phase shift film, which shifts the phase of EUV light to reduce the reflectance of EUV light. The phase shift film reduces the reflectance of EUV light by causing interference between the EUV light reflected by the surface of the absorber film opposite the multilayer reflective film side and the EUV light reflected by the surface of the absorber film facing the multilayer reflective film side. As materials for forming such a phase shift film, for example, Patent Document 1 discloses a material containing ruthenium (Ru) and chromium (Cr), and a material containing Ru, Cr, and nitrogen (N). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 225736 Summary of the Invention [Problem to be solved by the invention]

[0006] When fabricating a reflective mask, the absorber film (phase shift film) of a reflective mask blank is patterned. The patterning of the phase shift film is performed, for example, by dry etching using a pattern provided on the phase shift film as a mask. By the dry etching, the phase shift film is etched at the openings of the mask pattern, and the phase shift film is patterned into a shape corresponding to the pattern of the mask used. Here, when patterning the phase shift film, it is desirable to process it into a shape corresponding to the pattern of the mask used. For example, it is desirable to suppress the phenomenon (side etching) in which the phase shift film existing under the non-opening part of the mask is etched in the in-plane direction by the etchant that has entered through the opening of the mask. The present inventors have studied the phase shift film of the embodiment described in the above patent document and found that side etching is likely to occur and that improvement in this respect is necessary.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a reflective mask blank including a phase shift film that suppresses side etching. Another object of the present invention is to provide a reflective mask and a method for manufacturing the reflective mask. [Means for solving the problem]

[0008] As a result of extensive research into the above-mentioned problems, the inventors discovered that side etching of a phase shift film can be suppressed by including chromium and boron and setting the nitrogen content to a predetermined amount or less, and thus arrived at the present invention. That is, the inventors have found that the above problems can be solved by the following configuration. [1] A substrate; A multilayer reflective film that reflects EUV light, A protective film; a phase shift film in this order, the phase shift film contains chromium and boron; A reflective mask blank, wherein the nitrogen content in the phase shift film is less than 10 atomic % based on the total atoms in the phase shift film. [2] The reflective mask blank according to [1], wherein the phase shift film further contains ruthenium. [3] The content of ruthenium in the phase shift film is 1 to 95 atomic % based on the total atoms in the phase shift film; the content of chromium in the phase shift film is 4 to 98 atomic % based on the total atoms in the phase shift film; The reflective mask blank according to [2], wherein the content of boron in the phase shift film is 1 to 40 atomic % based on the total atoms in the phase shift film. [4] The reflective mask blank according to any one of [1] to [3], wherein the protective film contains rhodium. [5] The content of one specific element Q contained in the phase shift film is P PQ , the atomic weight of the specific element Q is M PQ , the density value of the single substance of the specific element Q is d PQ As a result, V is calculated from equation (2Q) PQ The specific volume V of the specific element Q Q year, The content of one specific element R contained in the protective film is P PR , the atomic weight of the specific element R is M PR , the density value of the single substance of the above specific element R is d PR V calculated from equation (2R) PR The specific volume V of the specific element R R When I said, Each element contained in the retardation film is designated as the specific element Q, and the specific volume amount V of each element is designated as the specific element Q. Q Calculate the specific volume V of each element. Q The specific volume of boron VQ The ratio is calculated, and the value obtained by multiplying the ratio by the thickness of the phase shift film is L B and, Each element contained in the protective film is designated as the specific element R, and the specific volume amount V of each element is designated as the specific element R. R Calculate the specific volume V of each element. R The specific volume of rhodium V R The ratio is calculated, and the value obtained by multiplying the ratio by the thickness of the protective film is L Rh and satisfy the relationship of formula (1). Formula (1) L B < 10×L Rh Formula (2Q) V PQ = P PQ M PQ / d PQ Formula (2R) V CR = P CR M CR / d CR In formula (2Q), P PQ The unit of is atomic %, and d PQ The unit is g / cm 3 is. In formula (2R), P CR The unit of is atomic %, and d CR The unit is g / cm 3 is. [6] The reflective mask blank according to any one of [1] to [5], wherein the phase shift film has a thickness of 70.0 nm or less. [7] The reflective mask blank according to any one of [1] to [6], wherein the protective film has a thickness of 1.0 to 5.0 nm. [8] A reflective mask having a phase shift film pattern formed by patterning the phase shift film of the reflective mask blank according to any one of [1] to [7]. [9] A method for producing a reflective mask, comprising a step of patterning the phase shift film of the reflective mask blank according to any one of [1] to [7]. [Effects of the Invention]

[0009] According to the present invention, a reflective mask blank can be provided that includes a phase shift film that suppresses side etching. The present invention also provides a reflective mask and a method for manufacturing the reflective mask. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. [Figure 2] 1A to 1C are cross-sectional views showing an example of a manufacturing process for a reflective mask using the reflective mask blank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0012] The meaning of each description in this specification is as follows. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. 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 (B, C, N, O, Si, Ti, Cr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, etc.).

[0013] <Reflective mask blank> The reflective mask blank of the present invention is a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, a protective film, and a phase shift film in this order. In the reflective mask blank of the present invention, the phase shift film contains Cr and B, and the N content in the phase shift film is less than 10 atomic % based on the total atoms in the phase shift film. The reflective mask blank of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a cross-sectional view showing one embodiment of a reflective mask blank of the present invention. The reflective mask blank 10 shown in Fig. 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18, in this order. The phase shift film 18 contains Cr and B, and the content of N in the phase shift film 18 is less than 10 atomic % with respect to all atoms in the phase shift film 18. The reflective mask blank 10 shown in FIG. 1 may have a conductive film, which will be described later, on the side of the substrate 12 opposite to the multilayer reflective film 14 side. The reflective mask blank 10 may also have an etching mask film, which will be described later, on the side of the phase shift film 18 opposite to the substrate 12 side.

[0015] In the reflective mask blank of the present invention, the mechanism by which side etching of the phase shift film is suppressed is not entirely clear, but the present inventors speculate as follows. When the phase shift film is patterned, the phase shift film is processed by, for example, dry etching. When dry etching the phase shift film, a pattern provided on the phase shift film is used as a mask, and the phase shift film arranged at a position corresponding to an opening of the mask is etched. When dry etching is performed, a potential is usually applied to the reflective mask blank, and processing is performed using a combination of the chemical action of an etchant and the physical action of ion collisions. Here, when processing of the phase shift film is mainly performed by the chemical action of an etchant, etching tends to proceed isotropically regardless of the application of a potential. This tends to cause etching to proceed in the in-plane direction of the phase shift film, and the phase shift film in positions corresponding to non-openings in the mask is also easily etched. In other words, when processing of the phase shift film is mainly performed by the chemical action of an etchant, side etching of the phase shift film tends to occur. As a result of extensive research, the inventors have found that when Cr is contained, the processing of the phase shift film is more likely to proceed due to the chemical action of the etchant, and side etching of the phase shift film is more likely to occur. Here, when the phase shift film contains B and the N content is less than 10 atomic % of all atoms in the phase shift film, the chemical bonding strength between Cr and B is thought to suppress the progress of processing due to chemical action, thereby suppressing side etching of the phase shift film. As a result, it is believed that side etching is suppressed in the phase shift film of the reflective mask blank of the present invention.

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

[0017] [substrate] The substrate of the reflective mask blank of the present invention preferably has a small thermal expansion coefficient, which can prevent distortion of the phase shift film pattern due to heat generated during exposure to EUV light. The thermal expansion coefficient of the substrate is 0±1.0×10 at 20℃. -7 / ℃ is preferred, 0±0.3×10 -7 / °C is more preferred. Materials with a low thermal expansion coefficient include SiO2-TiO2-based glass, but are not limited to this. Substrates such as crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, and metal can also be used. The SiO2-TiO2-based glass preferably uses silica 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 linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. Note that the SiO2-TiO2-based glass may contain trace components other than SiO2 and TiO2.

[0018] The surface of the substrate on which the multilayer reflective film is to be laminated (hereinafter also referred to as the "first principal surface") preferably has high surface smoothness. The surface smoothness of the first principal surface can be evaluated by surface roughness. The surface roughness of the first principal surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. The surface roughness can be measured using an atomic force microscope, and will be described as the root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to have a predetermined flatness, which improves the pattern transfer accuracy and positional accuracy of a reflective mask obtained using the reflective mask blank. In a predetermined region of the first main surface (e.g., a 132 mm × 132 mm region), the substrate preferably has a flatness of 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a Fujinon flatness measuring instrument. The size and thickness of the substrate are determined appropriately depending on the design values ​​of the mask, etc. For example, the outer shape is 6 inches (152 mm) square and the thickness is 0.25 inches (6.3 mm). The substrate is often rectangular or square. Furthermore, the substrate preferably has high rigidity to prevent deformation due to film stress of films (such as multilayer reflective films and phase shift films) formed on the substrate. For example, the substrate preferably has a Young's modulus of 65 GPa or more.

[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 high reflectivity for 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 for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more.

[0020] Multilayer reflective films can achieve high reflectivity for EUV light, so multilayer reflective films are usually used that are made by alternately stacking high-refractive index layers that have a high refractive index for EUV light and low-refractive index layers that have a low refractive index for EUV light multiple times. The multilayer reflective film may be formed by stacking multiple periods, each period being a stack structure in which a high refractive index layer and a low refractive index layer are stacked in this order from the substrate side, or may be formed by stacking multiple periods, each period being a stack structure in which a low refractive index layer and a high refractive index layer are stacked in this order. The high refractive index layer can be a layer containing Si. As the Si-containing material, in addition to simple Si, a Si compound containing Si and one or more elements selected from the group consisting of B, C, N, and O can be used. By using a high refractive index layer containing Si, a reflective mask with excellent reflectance to EUV light can be obtained. The low refractive index layer may be a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof. Si is commonly used for the high-refractive index layer, and Mo is commonly used for the low-refractive index layer. That is, Mo / Si reflective multilayer films are the most common. However, the reflective multilayer film is not limited to this, and Ru / Si reflective multilayer films, Mo / Be reflective multilayer films, Mo compound / Si compound reflective multilayer films, Si / Mo / Ru reflective multilayer films, Si / Mo / Ru / Mo reflective multilayer films, Si / Ru / Mo reflective multilayer films, and Si / Ru / Mo / Ru reflective multilayer films can also be used.

[0021] The thickness of each layer constituting the multilayer reflective film and the number of layer repeat units can be appropriately selected depending on the film material used and the EUV light reflectivity required for the reflective layer. Taking a Mo / Si multilayer reflective film as an example, a multilayer reflective film with a maximum EUV light reflectivity of 60% or more can be obtained by stacking a Mo film with a thickness of 2.3±0.1 nm and a Si film with a thickness of 4.5±0.1 nm so that the number of repeat units is 30 to 60. The multilayer reflective film preferably has a reflectivity of 60% or more for EUV light at an incident angle θ of 6°. The reflectivity is more preferably 65% ​​or more.

[0022] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using a known deposition method, such as DC sputtering, magnetron sputtering, or 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 of a high refractive index material and a target of a low refractive index material. When the multilayer reflective film is a Mo / Si multilayer reflective film, for example, a Si layer with a predetermined thickness is first deposited on a substrate using an ion beam sputtering method, for example, using a Si target. Then, a Mo layer with a predetermined thickness is deposited using a Mo target. This Si layer and Mo layer constitute one cycle, and for example, 30 to 60 cycles (preferably 40 to 50 cycles) are stacked to form a Mo / Si multilayer reflective film.

[0023] [Protective film] The reflective mask blank of the present invention has a protective film between the multilayer reflective film and the phase shift film, which is provided for the purpose of protecting the multilayer reflective film from damage during an etching process (usually a dry etching process) to form a pattern on the phase shift film. 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. More specifically, the above-mentioned materials include Ru metal alone, 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 Rh metal alone, 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 reduce the extinction coefficient while suppressing an increase in the refractive index, and can easily improve the reflectance to EUV light. Also, adding Ta, Ir, Pd, or Y to Rh can easily improve resistance to etching processes. Further, examples of materials that can achieve the above object include Al and nitrides containing these metals and nitrogen, and Al2O3. Among these, the materials that can achieve the above object are preferably Ru metal alone, Ru alloys, Rh metal alone, or Rh alloys.

[0024] When 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. Addition of such an element tends to reduce the crystallinity of the protective film and tends to improve the surface smoothness of the protective film on the buffer layer side. A protective film having low crystallinity means that the crystallite diameter calculated using a diffraction chart obtained by X-ray diffraction (XRD) is small. The crystallite diameter is calculated using Scherrer's equation. The full half-width of the diffraction peak with the highest intensity in the 2θ range of 30 to 55° is used to calculate the crystallite diameter using Scherrer's equation. If no clear diffraction peak is observed in the diffraction chart, the protective film can be said to be amorphous. The crystallite diameter of the protective film is preferably 10 nm or less, more preferably 6.0 nm or less, and even more preferably 5.0 nm or less. There is no particular lower limit to the crystallite diameter, but it is often 0.1 nm or more. The protective film may also be amorphous.

[0025] The thickness of the protective film is not particularly limited as long as it can 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, in order to obtain good 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. It is also preferable that the material of the protective film is Ru metal alone, a Ru alloy, Rh metal alone, or a Rh alloy, and that the thickness of the protective film is the above-mentioned preferable thickness. The thickness of the protective film is determined by X-ray reflectivity (XRR).

[0026] The density of the protective film is preferably 10.0 to 14.0 g / cm 3 The density of the protective film is 10.0 g / cm 3 When the density of the protective film is 14.0 g / cm or more, good etching resistance is easily obtained. 3 If it is equal to or less than this, it is easy to suppress a decrease in reflectance to EUV light. The density of the protective film is determined by X-ray reflectometry.

[0027] The protective film may be a film consisting of a single layer, or may be a multilayer film consisting of multiple layers. When the protective film is a multilayer film, each layer constituting the multilayer film is preferably made of the above-mentioned preferred material. Furthermore, when the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the above-mentioned preferred range. When the protective film is a multilayer film, it is preferable that the layer of the multilayer film closest to the phase shift film contains Rh. Furthermore, when the layer of the multilayer film closest to the phase shift film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0028] The protective film can be formed by known film formation methods such as DC sputtering, magnetron sputtering, ion beam sputtering, etc. When forming an Rh film by magnetron sputtering, it is preferable to use an Rh target as the target and Ar gas as the sputtering gas.

[0029] [Phase shift film] The phase shift film of the reflective mask blank of the present invention is required to have a high contrast between the EUV light reflected by the openings in the phase shift film (multilayer reflective film) and the EUV light reflected by the remaining portions of the phase shift film when the phase shift film is patterned to obtain a phase shift film pattern. Since the phase shift film pattern is used as a phase shift mask, the reflectance of the phase shift film to EUV light is preferably 2% or more. To obtain a sufficient phase shift effect, the reflectance of the phase shift film is preferably 9 to 15%. When a phase shift film is used as a phase shift mask, the contrast of the optical image on the wafer is improved, and the exposure margin is likely to increase.

[0030] The phase shift film of the reflective mask blank of the present invention contains Cr and B. The Cr content in the phase shift film is preferably 1 atomic % or more, more preferably 4 atomic % or more, even more preferably 5 atomic % or more, particularly preferably 10 atomic % or more, and may be 20 atomic % or more, based on the total atoms in the phase shift film. The Cr content in the phase shift film is preferably 99 atomic % or less, more preferably 98 atomic % or less, even more preferably 80 atomic % or less, and may be 70 atomic % or less, based on the total atoms in the phase shift film. The B content in the phase shift film is preferably 1 atomic % or more, more preferably 2 atomic % or more, even more preferably 4 atomic % or more, and particularly preferably 5 atomic % or more, based on the total atoms in the phase shift film. The B content in the phase shift film is preferably 40 atomic % or less, more preferably 25 atomic % or less, even more preferably 15 atomic % or less, and particularly preferably 12 atomic % or less. The N content in the phase shift film is less than 10 atomic % of all atoms in the phase shift film, preferably 5 atomic % or less, and more preferably 1 atomic % or less. It is also preferable that the phase shift film does not contain N. In other words, the N content may be 0 atomic % of all atoms in the phase shift film.

[0031] It is also preferable that the phase shift film further contains Ru. When the phase shift film contains Ru, the Ru content is preferably 1 atomic % or more, more preferably 20 atomic % or more, even more preferably 30 atomic % or more, even more preferably 40 atomic % or more, and particularly preferably 50 atomic % or more, based on the total atoms in the phase shift film. The Ru content is preferably 98 atomic % or less, more preferably 95 atomic % or less, even more preferably 90 atomic % or less, particularly preferably 80 atomic % or less, and most preferably 70 atomic % or less, based on the total atoms in the phase shift film. When the phase shift film contains Ru, the Cr content is preferably 1 atomic % or more, more preferably 4 atomic % or more, even more preferably 10 atomic % or more, particularly preferably 20 atomic % or more, and most preferably 25 atomic % or more. Also, when the phase shift film contains Ru, the Cr content is preferably 98 atomic % or less, more preferably 90 atomic % or less, even more preferably 80 atomic % or less, particularly preferably 70 atomic % or less, and most preferably 60 atomic % or less. When the phase shift film contains Ru, the B content is preferably 1 atomic % or more, more preferably 2 atomic % or more, even more preferably 3 atomic % or more, and particularly preferably 5 atomic % or more. Also, when the phase shift film contains Ru, the B content is preferably 40 atomic % or less, more preferably 20 atomic % or less, even more preferably 15 atomic % or less, and particularly preferably 12 atomic % or less. When the phase shift film contains Ru, it is also preferable that the Ru content is 1 to 95 atomic % relative to all atoms in the phase shift film, the Cr content is 4 to 98 atomic % relative to all atoms in the phase shift film, and the B content is 1 to 40 atomic % relative to all atoms in the phase shift film.

[0032] Furthermore, the inventors' investigations have revealed that side etching is more likely to occur when the ratio of the Cr content to the Ru content (Cr content / Ru content) is close to 1. Here, it has been found that even if the content ratio is 1:1, side etching can be suppressed as long as the B content is 3 atomic % or more. Here, when the content ratio is close to 1 (for example, 0.5 to 1.2), the B content is preferably 3 atomic % or more, more preferably 5% or more, and even more preferably 7 atomic % or more, in that side etching is further suppressed. When the content ratio is close to 1 (for example, 0.5 to 1.2), the upper limit of the B content is not particularly limited, and may be, for example, 40 atomic % or less. When the content ratio is close to 1, it is thought that the higher the B content, the more easily side etching is suppressed. On the other hand, it is believed that the more the ratio of the above contents is away from 1, the smaller the content of B required to suppress side etching tends to be.

[0033] If the phase shift film does not contain Ru, the Cr content is preferably 50 atomic % or more, more preferably 60 atomic % or more, and even more preferably 65 atomic % or more, based on the total atoms in the phase shift film.If the phase shift film does not contain Ru, the Cr content is preferably 95 atomic % or less, more preferably 90 atomic % or less, and even more preferably 80 atomic % or less, based on the total atoms in the phase shift film. When the phase shift film does not contain Ru, the B content is preferably 5 atomic % or more, more preferably 10 atomic % or more, and even more preferably 20 atomic % or more, based on the total atoms in the phase shift film. When the phase shift film does not contain Ru, the B content is preferably 50 atomic % or less, more preferably 40 atomic % or less, and even more preferably 35 atomic % or less.

[0034] It is also preferable that the phase shift film and the protective film satisfy the following relationship: First, the content of one specific element Q contained in the phase shift film (unit: atomic %) is defined as P PQ , the atomic weight of a specific element Q is MPQ , the density value of a specific element Q (unit: g / cm 3 ) to d PQ As a result, V is calculated from equation (2Q) PQ A specific volume of a specific element Q is V Q Let's say. In addition, the content of one specific element R contained in the protective film (unit: atomic %) is defined as P PR , the atomic weight of a specific element R is M PR , the density value of a specific element R (unit: g / cm 3 ) to d PR V calculated from equation (2R) PR V is the specific volume of a specific element R R Let's say. In this case, each element contained in the phase shift film is designated as a specific element Q, and the specific volume of each element is designated as V. Q Calculate the specific volume of each element V Q The specific volume V of B relative to the total amount of Q The ratio is calculated, and the value obtained by multiplying this ratio by the thickness of the phase shift film (unit: nm) is L B Furthermore, each element contained in the protective film is designated as a specific element R, and the specific volume of each element V is calculated. R Calculate the specific volume of each element V R The specific volume of Rh V relative to the total amount of R The ratio is calculated, and the value obtained by multiplying this ratio by the thickness of the protective film (unit: nm) is L Rh Calculate the above calculated L B and L Rh It is also preferable that the relationship of formula (1) is satisfied. Formula (1) L B < 10×L Rh Formula (2Q) V PQ = P PQ M PQ / d PQ Formula (2R) V CR = P CR M CR / d CR

[0035] The above specific volume V Qcorresponds to the volume of the specific element Q when only the specific element Q contained in the phase shift film is extracted. B represents the thickness of the B film when only the B contained in the phase shift film is extracted. In addition, the above specific volume V R corresponds to the volume of the specific element R alone when only the specific element R contained in the protective film is extracted. That is, L in the above formula (1) Rh represents the thickness of the Rh film when only the Rh contained in the protective film is extracted. Therefore, the above formula (1) is the thickness of the B alone when the B contained in the phase shift film is extracted (L B ) is the thickness of the Rh alone when the Rh contained in the protective film is extracted (L Rh ) is less than 10 times higher. When the above formula (1) is satisfied, the time required for etching the protective film tends to be longer than the time required for etching the phase shift film, and the multilayer reflective film is more likely to be protected. In other words, when the above formula (1) is satisfied, the reflectance of the multilayer reflective film is less likely to decrease due to processing of the phase shift film. The value obtained by subtracting the value on the left side of the formula (1) from the value on the right side is preferably 1.0 or more, more preferably 5.0 or more, and even more preferably 10.0 or more. The value obtained by subtracting the value on the left side of the formula (1) from the value on the right side is often 20.0 or less.

[0036] The above formula (2Q) will be explained more specifically below. For example, consider the case where the phase shift film contains only Cr, B, and Ru. In this case, the specific volume V calculated for the specific element Q using the above formula (2Q) Q is the specific volume V calculated for Cr Cr and the specific volume V calculated for B B and the specific volume V calculated for Ru Ru This becomes the case. That is, in the above case, L B is calculated using the following formula (3Q):

[0037]

number

[0038] In the above formula (3Q), P B , P Cr and P Ru are the contents of B, Cr and Ru in the phase shift film, respectively, in atomic %. In formula (3Q), M B , M Cr and M Ru are the atomic weights of B, Cr, and Ru, respectively. In formula (3Q), d B , d Cr and d Ru are the density values ​​of B, Cr, and Ru, respectively, in units of g / cm 3 The densities of B, Cr, and Ru are 2.08, 7.19, and 12.45 g / cm, respectively. 3 will be adopted respectively. In formula (3Q), L P is the thickness of the phase shift film, and is expressed in nm.

[0039] The above formula (2R) will be explained in more detail. For example, when the protective film contains only Rh, L is obtained in the same manner as the above formula (3Q). Rh is calculated, and L Rh is the thickness of the protective film, L C The density of Rh is 12.41 g / cm 3 will be adopted.

[0040] The phase shift film may contain metal elements other than Cr, B, and Ru. Examples of the metal elements include elements of Group 4, Group 5, Group 6, and Group 7. In terms of the optical properties and processability of the phase shift film, at least one element selected from the group consisting of Si, Mo, Ta, W, Nb, and Re is preferred. When the phase shift film contains metal elements other than Cr, B, and Ru, the contents of these elements in the phase shift film and the preferred ranges of the contents of Cr, B, and Ru are as described above. When the phase shift film contains a metal element other than Cr, B, and Ru, the content of the metal element is preferably 5 atomic % or more, more preferably 10 atomic % or more, and even more preferably 20 atomic % or more, based on the total atoms in the phase shift film. The content of the metal element is preferably 50 atomic % or less, more preferably 40 atomic % or less, and even more preferably 30 atomic % or less, based on the total atoms in the phase shift film.

[0041] The phase shift film preferably further contains at least one element selected from the group consisting of C, O and Si (hereinafter also referred to as element X2). When the phase shift film contains the element X2, the content of the element X2 is preferably 1 atomic % or more, more preferably 3 atomic % or more, and even more preferably 5 atomic % or more, based on the total atoms of the phase shift film. Also, when the phase shift film contains the element X2, the content of the element X2 is preferably 25 atomic % or less, more preferably 20 atomic % or less, and even more preferably 10 atomic % or less. When the phase shift film contains two or more kinds of element X2, the content of the element X2 is the total content of the element X2. The phase shift film does not necessarily contain the element X2.

[0042] In this specification, the content of an element contained in a phase shift film is determined by analysis using X-ray photoelectron spectroscopy (XPS). For the XPS analysis, an analytical instrument "PHI 5000 VersaProbe" manufactured by ULVAC-PHI, Inc. is used. The instrument is calibrated in accordance with JIS K 0145. First, a measurement sample of approximately 1 cm square is cut out from a reflective mask blank, and the obtained measurement sample is set in a measurement holder so that the phase shift film side becomes the measurement surface. After the measurement holder is loaded into the apparatus, if another layer is disposed on the side of the phase shift film opposite the substrate side, the other layer is removed with an argon ion beam to expose the phase shift film. After exposing the phase shift film, the phase shift film is removed from the outermost surface by a thickness equal to half the thickness of the phase shift film. The sputtering rate during the removal can be measured using a separately prepared sample. After removing the top surface of the phase shift film, the removed area is irradiated with X-rays (monochromated AlKα rays) and analyzed at a photoelectron take-off angle (the angle between the surface of the measurement sample and the direction of the detector) of 45°. During the analysis, a neutralization gun is used to suppress charge buildup. The analysis begins with a wide scan in the binding energy range of 1000 to 0 eV to confirm the elements present, followed by a narrow scan depending on the elements present (e.g., Cr, B, and Ru). The narrow scan is performed with a pass energy of 58.7 eV, an energy step of 0.1 eV, a time step of 50 ms, and five accumulations. 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 two accumulations. The content of each element in the phase shift film is analyzed using the relative sensitivity coefficient specific to each element and each orbital from the spectrum obtained by narrow scanning when XPS analysis is performed according to the above procedure. Alternatively, a model sample formed under the same conditions as those for forming the phase shift film may be used to carry out the analysis in the same manner as above.

[0043] The thickness of the phase shift film is preferably 20.0 nm or more, more preferably 30.0 nm or more, and from the viewpoint of reducing the shadowing effect, the thickness of the phase shift film is preferably 70.0 nm or less, more preferably 60.0 nm or less, even more preferably 55.0 nm or less, and particularly preferably 50.0 nm or less. The thickness of the phase shift film is determined by X-ray reflectometry.

[0044] The refractive index n of the phase shift film is preferably 0.885 or more, and is preferably 0.935 or less, more preferably 0.930 or less, and even more preferably 0.920 or less, in order to make the thickness of the phase shift film thinner. The extinction coefficient k of the phase shift film is preferably 0.050 or less, more preferably 0.040 or less, and even more preferably 0.035 or less. In terms of easier adjustment of the reflectance of the phase shift film, the extinction coefficient k of the phase shift film is preferably 0.018 or more, more preferably 0.020 or more, and even more preferably 0.022 or more. The refractive index n and extinction coefficient k are determined by measuring the incidence angle dependency of reflectance using EUV light with a wavelength of 13.5 nm and performing fitting on the obtained profile using the refractive index n and extinction coefficient k as parameters.

[0045] The crystallite diameter of the phase shift film is preferably 10.0 nm or less, more preferably 6.0 nm or less, and even more preferably 4.0 nm or less. There is no particular lower limit to the crystallite diameter, but it is often 0.1 nm or more. The phase shift film of the present invention may also be amorphous. When the phase shift film contains the element X2, the crystallite size of the phase shift film is easily reduced. The method for measuring the crystallite diameter of the phase shift film is the same as the method for measuring the crystallite diameter of the protective film.

[0046] The phase shift film preferably has resistance to dissolution in cleaning solutions. When the phase shift film has resistance to dissolution in cleaning solutions, the phase shift film is less likely to be removed during the etching process of the etching mask film described later, making it easier to obtain a desired pattern. More specifically, it is preferable that the change in thickness of the phase shift film is small when the phase shift film is brought into contact with a sulfuric acid-hydrogen peroxide aqueous solution (SPM). For example, when the phase shift film is etched with SPM at 100° C. for 20 minutes, the change in film thickness between before and after the etching is preferably 1.0 nm or less, more preferably 0.5 nm or less, and even more preferably 0.2 nm or less. The lower limit of the change in film thickness is 0 nm or more.

[0047] The phase shift film of the reflective mask blank of the present invention can be etched, for example, by plasma generated using a mixed gas containing a Cl-based gas (for example, Cl2 gas) and O2 gas. When etching the phase shift film, side etching is suppressed. Specifically, under the conditions described in the examples below, first, a potential is applied to the reflective mask blank to perform bias etching, and the etching rate (ER I Similarly, the etching rate (ER) was measured by non-bias etching, which involves etching the reflective mask blank without applying a potential. R ) is measured. In this case, the above ER I ER for R Ratio of (ER R / ER I ) is preferably 1.00 or less, more preferably 0.50 or less, even more preferably 0.40 or less, particularly preferably 0.35 or less, and most preferably 0.30 or less. I ER for R The ratio is often 0.01 or more. It should be noted that in bias etching, etching proceeds through chemical and physical actions, whereas in non-bias etching, etching proceeds mainly through chemical actions. Therefore, the above ratio (ER R / ER I ) is small, side etching is likely to be suppressed.

[0048] The phase shift film may be a single layer film or a multilayer film made up of multiple films. When the phase shift film is a multilayer film made up of multiple films, the phase shift film may include a film that does not contain Cr or B.

[0049] The phase shift film can be formed by known film formation methods such as DC sputtering, magnetron sputtering, ion beam sputtering, etc. For example, when forming a RuCrB film as the phase shift film by magnetron sputtering, the phase shift film can be formed by sputtering using a Ru target and a CrB target and supplying a gas containing Ar gas. The ratio of elements contained in the phase shift film can be adjusted by the ratio of elements in the target used, the ratio of power input to the target, and the like. Moreover, instead of the CrB target, a Cr target and a B target may be used.

[0050] [Conductive film] The reflective mask blank of the present invention may have a conductive film on the surface (second main surface) opposite to the first main surface of the substrate. By providing the conductive film, the reflective mask blank can be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance, for example, preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The conductive film may be made of a wide range of materials, including those described in known literature. For example, the high-dielectric-constant coating described in JP-A-2003-501823, specifically a coating made of Si, Mo, Cr, CrON, or TaSi, may be used. The conductive film may also be made of 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, more preferably 10 to 400 nm. The conductive film may also have a function of adjusting stress on the second main surface side of the reflective mask blank. That is, the conductive film can adjust the reflective mask blank to be flat by balancing the stress from various films formed on the first main surface side. The conductive film can be formed by using a known film formation method, for example, a sputtering method such as DC sputtering, magnetron sputtering, or ion beam sputtering, a CVD method, a vacuum deposition method, or an electrolytic plating method.

[0051] [Etching mask film] The reflective mask blank of the present invention may have an etching mask film on the side of the phase shift film opposite to the substrate side. The etching mask film is preferably made of a material that is highly resistant to dry etching. When an etching mask film is formed on a phase shift film, dry etching can be performed even if the minimum line width of the phase shift film pattern is small. Therefore, this is effective for miniaturizing the phase shift film pattern.

[0052] The etching mask film preferably contains one or more elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf (hereinafter also referred to as "element X3"). That is, the material constituting the etching mask film preferably contains element X3. The etching mask film may further contain at least one element selected from the group consisting of B, N and O. Examples of materials constituting the etching mask film include a simple substance of element X3, and oxides, nitrides, oxynitrides, carbides, carbonitrides, carbonates, fluorides, and oxyfluorides of element X3. Note that the material constituting the etching mask film may also be a composite compound (e.g., composite oxide) containing two or more elements of element X3.

[0053] For example, Cr-based materials containing Cr as element X3 include materials containing Cr and one or more elements selected from the group consisting of Cr and O, N, C, and H, and more specifically, include CrO, CrN, and CrON. Note that the notation "CrON" represents a material containing Cr, O, and N, and similar notations below have the same meaning. Furthermore, examples of Si-based materials containing Si as the element X3 include materials containing Si and one or more elements selected from the group consisting of O, N, C, and H, and more specifically, include SiO2, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON.

[0054] The thickness of the etching mask film is preferably 2 nm or more, and is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less.

[0055] The etching mask film can be formed by using a known film formation method such as DC sputtering, magnetron sputtering, or ion beam sputtering.

[0056] <Reflective mask manufacturing method and reflective mask> The reflective mask of the present invention is obtained by patterning the phase shift film of the reflective mask blank of the present invention. One example of a method for producing a reflective mask will be described with reference to FIG.

[0057] 2(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having, in this order, a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18. The resist pattern 40 can be formed by a known method, for example, by applying a resist to the phase shift film 18 of the reflective mask blank, and then exposing and developing the resist to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Thereafter, the phase shift film 18 is etched and patterned using the resist pattern 40 of FIG. 2(a) as a mask, and the resist pattern 40 is removed to obtain a laminate having the phase shift film pattern 18pt shown in FIG. 2(b). Next, as shown in Fig. 2(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate of Fig. 2(b), and dry etching is performed using the resist pattern 41 of Fig. 2(c) as a mask. Dry etching is performed until it reaches the substrate 12. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Fig. 2(d).

[0058] The dry etching used to form the phase shift film pattern 18pt may be, for example, dry etching using a Cl-based gas or dry etching using an F-based gas. The resist pattern 40 or 41 may be removed by a known method, such as removal with a cleaning solution, such as sulfuric acid-hydrogen peroxide solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide solution (APM), OH radical cleaning water, or ozone water. When the reflective mask blank has an etching mask film as another film, the etching mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the etching mask film as a mask. When the reflective mask blank has an etching mask film as another film, a step of removing the etching mask film may be performed in the step of obtaining the reflective mask. Furthermore, the etching mask film may be removed simultaneously in the step of removing the resist pattern 40 or 41 described above.

[0059] In the phase shift film of the reflective mask blank of the present invention, side etching is suppressed during the dry etching, so that the phase shift film can be easily patterned as designed. A reflective mask obtained by patterning the phase shift film of the reflective mask blank of the present invention can be suitably used as a reflective mask for exposure to EUV light. [Example]

[0060] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples. Examples 1 to 7 and 16 to 18 described below are working examples, and Examples 8 to 15 are comparative examples.

[0061] <Example 1> First, the procedure for obtaining the reflective mask blank of Example 1 will be described as a representative example.

[0062] [substrate] First, a SiO2-TiO2 glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared as a substrate. This glass substrate has a thermal expansion coefficient of 0.02 × 10 at 20 °C. -7 / °C, Young's modulus is 67 GPa, Poisson's ratio is 0.17, and specific stiffness is 3.07 × 10 7 m 2 / s 2 The quality assurance area of ​​the first main surface of the substrate was polished to a root-mean-square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less. A 100 nm thick Cr film was formed on the second main surface of the substrate using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / □.

[0063] [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 repeating the process of depositing a Si film (4.5 nm thick) and a Mo film (2.3 nm thick) using ion beam sputtering 40 times, and after the 40th Mo film was formed, an additional Si film (4.5 nm thick) was deposited. The total thickness of the Mo / Si multilayer reflective film was 276.5 nm ((4.5 nm + 2.3 nm) × 40 + 4.5 nm).

[0064] [Protective film] On the multilayer reflective film formed by the above procedure, a Ru film (thickness: 1.0 nm) and a Rh film (thickness: 2.5 nm) were formed in this order as protective films. The Ru film and the 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: 0.027Pa Ion acceleration voltage: 600V ·Deposition speed: 0.056nm / sec Rh film deposition conditions: Target: Rh target Sputtering gas: Ar gas Gas pressure: 0.027Pa Ion acceleration voltage: 600V ·Deposition speed: 0.077nm / sec

[0065] [Phase shift film] A CrB film (45 nm thick) was formed as a phase shift film on the protective film formed by the above procedure. The CrB film was formed by DC sputtering under the following conditions. Target: CrB target (Cr: 60 atomic %, B: 40 atomic %) Sputtering gas: Ar gas Gas pressure: 2.0 x 10 -1 Pa Input power density per target area: 6.2W / cm 2 The composition of the CrB film formed in Example 1 was analyzed by the above-mentioned method (XPS method), and the Cr content was found to be 65 atomic % and the B content was 35 atomic %.

[0066] Through the above procedure, the reflective mask blank of Example 1 was obtained.

[0067] <Evaluation> [Etching rate] The etching rate of the phase shift film of the reflective mask blank of Example 1 was measured. Specifically, plasma was generated using an inductively coupled plasma (ICP) generator for the reflective mask blank of Example 1, and the reflective mask blank was irradiated with the plasma to perform etching, and the etching rate of the phase shift film was measured. The etching rate (ER) of bias etching, which applies a voltage to a reflective mask blank, is I ), and the etching rate (ER) by non-bias etching without applying voltage to the reflective mask blank. R ) was measured. The specific etching conditions are as follows: Antenna RF power output: 1320W Bias output: 50W (bias etching) or 0W (non-bias etching) Etching gas pressure: 0.4Pa Etching gas: O2 and Cl2 mixed gas Etching gas flow rate: Cl245sccm, O245sccm "sccm" is an abbreviation for "Standard Cubic Centimeter per Minute" and is the gas flow rate (cm) per minute converted to a volume value at 1 atmosphere (1013.25 hPa) and 0°C. 3 / min). The film thickness was measured by XRR before and after etching under the above conditions, and the change in film thickness was divided by the etching time to calculate the etching rate (unit: nm / min). In addition, the ratio of the etching rate by non-bias etching to the etching rate by bias etching (ER R / ER I ) was calculated. The above ratio (ER R / ER I ) is preferably 1.00 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less, from a practical standpoint.

[0068] <Examples 2-18> A reflective mask blank was obtained in the same manner as in Example 1, except that the film formation conditions for the phase shift film were adjusted so that the composition and film thickness were as shown in the table below. Specifically, for example, in the reflective mask blank of Example 3, CrB and Ru were used as targets, and the input power density for each target was set to the values ​​shown in the table, to form a phase shift film that was a RuCrB film. Regarding the protective film in each example, the thickness of the Rh film was changed to 1.5 nm in Examples 2 to 16, 1.0 nm in Example 17, and 0 nm in Example 18 (only the Ru film was formed). For the phase shift film containing N, N2 gas was introduced into the sputtering atmosphere and the amount introduced was adjusted to obtain the composition shown in the table below. In addition, in the same manner as in Example 1, the etching rate of the phase shift film of the reflective mask blank of each example was measured. Regarding Examples 6 and 7, R / ER I When calculating, measurements were carried out under the following conditions. Antenna RF power output: 900W Bias output: 80W (bias etching) or 0W (non-bias etching)

[0069] <Result> The composition of the phase shift film in the reflective mask blank of each example and the measurement results of the etching rate are shown in Table 1 below. In Table 1, the column "Cr / Ru" indicates the ratio of the Cr content to the Ru content in the phase shift film. In Table 1, “ER I The " column shows the etching rate by bias etching, and the "ER R The " column indicates the etching rate by non-bias etching. In Table 1, “ER R / ER I The "ER" column shows the ratio of the etching rate by non-bias etching to the etching rate by bias etching. R / ER IThe smaller the value in the "" column, the more difficult it is for the phase shift film to be isotropically etched, and the more easily side etching is suppressed. In Table 1, the notation "at%" means atomic %. In Table 1, “L B " column and "L Rh The values ​​in the "" column are the values ​​calculated by the above formula (2Q) and the above formula (2R). The calculation method for these values ​​is as described above. In Table 1, the column "(Right side) - (Left side) of formula (1)" indicates the value obtained by subtracting the value of the left side from the value of the right side of the above formula (1). Note that if the value in the above column is a positive value, it indicates that the above formula (1) is satisfied.

[0070] [Table 1]

[0071] From the results shown in Table 1, the phase shift films of the reflective mask blanks of Examples 1 to 7 and Examples 16 to 18 have the "ER R / ER I The value in the " " column is small, and it is thought that side etching is easily suppressed. Furthermore, a comparison of Examples 1 to 7 with Examples 16 to 18 suggests that when the relationship of the above formula (1) is satisfied, the time required to etch the protective film tends to be longer than the time required to etch the phase shift film, making it easier to protect the multilayer reflective film. [Explanation of symbols]

[0072] 10 Reflective mask blanks 12 PCB 14 Multilayer reflective film 16 Protective film 18 Phase shift film 18pt phase shift film pattern 40,41 Resist pattern

Claims

1. A substrate; a multilayer reflective film that reflects EUV light; A protective film; a phase shift film in this order, the phase shift film comprises chromium and boron; a reflective mask blank, wherein the nitrogen content in the phase shift film is less than 10 atomic % based on the total atoms in the phase shift film;

2. The reflective mask blank according to claim 1 , wherein the phase shift film further contains ruthenium.

3. the content of ruthenium in the phase shift film is 1 to 95 atomic % based on the total atoms in the phase shift film; the content of chromium in the phase shift film is 4 to 98 atomic % based on the total atoms in the phase shift film; 3. The reflective mask blank according to claim 2, wherein the content of boron in said phase shift film is 1 to 40 atomic % based on the total atoms in said phase shift film.

4. 4. The reflective mask blank according to claim 1, wherein the protective film contains rhodium.

5. The content of one specific element Q contained in the phase shift film is P ＰＱ , the atomic weight of the specific element Q is M ＰＱ , the value of the density of the simple substance of the specific element Q is d ＰＱ V calculated from equation (2Q) ＰＱ The specific volume amount V of the specific element Q Ｑ year, The content of one specific element R contained in the protective film is P ＰＲ , the atomic weight of the specific element R is M ＰＲ , the density value of the simple substance of the specific element R is d ＰＲ V calculated from the formula (2R) ＰＲ The specific volume V of the specific element R Ｒ When I said, Each element contained in the retardation film is designated as the specific element Q, and the specific volume amount V of each element is designated as the specific element Q. Ｑ The specific volume V of each element is calculated. Ｑ The specific volume amount V of boron relative to the total amount Ｑ The ratio is calculated, and the value obtained by multiplying the ratio by the thickness of the phase shift film is determined as L Ｂ and, Each element contained in the protective film is designated as the specific element R, and the specific volume amount V of each element is designated as the specific element R. Ｒ The specific volume V of each element is calculated. Ｒ The specific volume amount V of rhodium relative to the total amount of Ｒ The ratio is calculated, and the value obtained by multiplying the ratio by the thickness of the protective film is determined as L Ｒｈ The reflective mask blank according to claim 4 , wherein Formula (1) L Ｂ < 10×L Ｒｈ Formula (2Q) V ＰＱ = P ＰＱ ・M ＰＱ / d ＰＱ Formula (2R) V ＣＲ = P ＣＲ ・M ＣＲ / d ＣＲ In formula (2Q), P ＰＱ The unit of is atomic %, and d ＰＱ The unit is g / cm ３ is. In formula (2R), P ＣＲ The unit of is atomic %, and d ＣＲ The unit is g / cm ３ is.

6. 4. The reflective mask blank according to claim 1, wherein the phase shift film has a thickness of 70.0 nm or less.

7. 4. The reflective mask blank according to claim 1, wherein the protective film has a thickness of 1.0 to 5.0 nm.

8. A reflective mask having a phase shift film pattern formed by patterning the phase shift film of the reflective mask blank according to any one of claims 1 to 3.

9. A method for producing a reflective mask, comprising the step of patterning the phase shift film of the reflective mask blank according to any one of claims 1 to 3.

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