Mask blank, reflective mask, and method for manufacturing semiconductor devices

Abstract

Provided is a mask blank capable of manufacturing a reflective mask that can exhibit excellent transfer characteristics when performing exposure transfer with an EUV exposure apparatus. 【Solution means】The thin film is made of a material containing at least one selected from chromium (Cr), vanadium (V), palladium (Pd), titanium (Ti), iridium (Ir), Rh (rhodium), tantalum (Ta), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tin (Sn), and platinum (Pt). The film thickness of the thin film is 32.40 nm or more and 98 nm or less. The refractive index of the thin film with respect to light having a wavelength λ L = 13.0 nm is n L , the refractive index of the thin film with respect to light having a wavelength λ M = 13.5 nm is n M , the refractive index of the thin film with respect to light having a wavelength λ H = 14.0 nm is n H , when the coefficient P = [(1 - n H ) / λ H - (1 - n L ) / λ L / [(1 - n M ) / λ M , the absolute value of the coefficient P is 0.15 or less.

Description

[Technical Field]

[0001] This invention relates to a mask blank, a reflective mask, and a method for manufacturing semiconductor devices, which are master plates for manufacturing exposure masks used in the manufacture of semiconductor devices. [Background technology]

[0002] Exposure equipment used in semiconductor device manufacturing has evolved by gradually shortening the wavelength of the light source. To achieve finer pattern transfer, EUV lithography, which uses extreme ultraviolet (EUV) light with a wavelength of around 13.5 nm, has been developed. In EUV lithography, reflective masks are used because there are few materials that are transparent to EUV light. Typical reflective masks include reflective binary masks and reflective phase-shift masks (reflective halftone phase-shift masks).

[0003] Such reflective masks for EUV lithography and technologies related to mask blanks for fabricating them are described in Patent Documents 1 and 2.

[0004] Patent Document 1 discloses an extreme ultraviolet exposure mask comprising a highly reflective portion made of a multilayer film formed on a substrate and a low-reflective portion made of a single-layer film formed on a part of the multilayer film. In this mask, the reflected light from the low-reflective portion has a reflectivity of 5 to 15% of the reflected light from the highly reflective portion and has a phase difference of 175 to 185 degrees with respect to the reflected light from the highly reflective portion. The refractive index (1-δ) and extinction coefficient β of the single-layer film constituting the low-reflective portion with respect to the exposure wavelength are located within a region connecting predetermined point coordinates (1-δ, β) in a planar coordinate system with the refractive index (1-δ) and extinction coefficient β as the coordinate axes.

[0005] Patent Document 2 discloses a reflective mask blank having a multilayer reflective film, a protective film, and a phase-shifting film that shifts the phase of EUV light on a substrate in that order. This reflective mask blank is characterized in that the reflectivity of the phase-shifting film surface is greater than 3% and less than or equal to 20%, and the phase-shifting film is composed of a material made of an alloy containing two or more metals, such that it has a predetermined phase difference of 170 to 190 degrees. The metal elements satisfying a refractive index n of k > α*n + β and an extinction coefficient k are designated as group A, and the metal elements satisfying a refractive index n of k < α*n + β and an extinction coefficient k are designated as group B. The alloy is characterized by selecting one or more metal elements from group A and group B respectively, and adjusting the composition ratio such that the change in phase difference is within ±2 degrees and the change in reflectivity is within ±0.2% when the film thickness of the phase-shifting film fluctuates by ±0.5% relative to a set film thickness. (where α is a proportionality constant and β is a constant.) [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2006-228766 [Patent Document 2] Japanese Patent Publication No. 2018-146945 [Overview of the project] [Problems that the invention aims to solve]

[0007] The finer the pattern, and the higher the precision of the pattern dimensions and position, the better the electrical characteristics and performance of the semiconductor device, and the higher the integration density and the smaller the chip size. Therefore, EUV lithography is required to have a higher level of precision and finer pattern transfer performance than before. Currently, there is a demand for ultra-fine and high-precision pattern formation compatible with the hp16nm (half pitch 16nm) generation. To meet these demands, there is a need for reflective masks that use EUV light as exposure light and further utilize the phase shift effect.

[0008] In reflective masks that utilize such a phase shift effect, a multilayer reflective film is prepared on the main surface of the substrate at 13.5 nm, which is the central wavelength of EUV light. The thin film used for pattern formation (e.g., an absorber film) prepared on top of this multilayer reflective film is then designed to have a phase shift effect. In reflective masks, there is a need for further improvement in exposure transfer characteristics. In particular, in the case of reflective masks equipped with a thin film (e.g., an absorber pattern) on which a transfer pattern utilizing the phase shift effect is formed, there is a need for further improvement in the optical properties of this thin film.

[0009] Therefore, the present invention aims to provide a mask blank that can be used to manufacture a reflective mask that exhibits excellent transfer characteristics when exposure transfer is performed using an EUV exposure apparatus.

[0010] Furthermore, the present invention aims to provide a reflective mask that exhibits excellent transfer characteristics when exposure transfer is performed using an EUV exposure apparatus, and to provide a method for manufacturing a semiconductor device using the reflective mask. [Means for solving the problem]

[0011] To solve the above problems, the present invention has the following configuration.

[0012] (Composition 1) A mask blank in which a multilayer reflective film and a thin film for pattern formation are provided in this order on the main surface of the substrate, The thin film is made of a material containing metal, The wavelength λ of the thin film L = The refractive index for light at 13.2 nm is n L , The wavelength λ of the thin film M = The refractive index for light at 13.5 nm is n M , The wavelength λ of the thin film H = The refractive index for light at 13.8 nm is n H , Coefficient P = [(1-n H) / λ H -(1 - n L ) / λ L / [(1 - n M ) / λ M when, the absolute value of the coefficient P is 0.09 or less a mask blank characterized by this.

[0013] (Configuration 2) For the refractive index n of the thin film with respect to light of wavelength λ M is 0.96 or less, the mask blank according to Configuration 1. M

[0014] (Configuration 3) The thickness of the thin film is less than 100 nm, the mask blank according to Configuration 1 or 2.

[0015] (Configuration 4) A mask blank according to any one of Configurations 1 to 3, characterized by having a protective film between the multilayer reflective film and the thin film.

[0016] (Configuration 5) The thin film causes a phase difference of 130 degrees to 230 degrees between the reflected light from the thin film and the reflected light from the multilayer reflective film with respect to light of the wavelength λ M A mask blank according to any one of Configurations from 1 to 4.

[0017] (Configuration 6) A reflective mask in which a multilayer reflective film and a thin film on which a transfer pattern is formed are provided in this order on the main surface of a substrate, the thin film is made of a material containing a metal, for the refractive index n of the thin film with respect to light of wavelength λ L = 13.2 nm, L , for the refractive index n of the thin film with respect to light of wavelength λ M = 13.5 nm, M |, for the refractive index n of the thin film with respect to light of wavelength λ H = 13.8 nm,H , Coefficient P = [(1-n H ) / λ H -(1-n L ) / λ L ] / [(1-n M ) / λ M When ], The absolute value of the coefficient P is 0.09 or less. A reflective mask characterized by the following features.

[0018] (Composition 7) wavelength λ M The refractive index n of the thin film with respect to light M The reflective mask according to configuration 6, characterized in that the value is 0.96 or less.

[0019] (Composition 8) The reflective mask according to configuration 6 or 7, characterized in that the thickness of the thin film is less than 100 nm.

[0020] (Composition 9) A reflective mask according to any one of configurations 6 to 8, characterized in that a protective film is provided between the multilayer reflective film and the thin film.

[0021] (Composition 10) The thin film has the wavelength λ M A reflective mask according to any one of configurations 6 to 9, characterized in that a phase difference of 130 to 230 degrees is generated between the reflected light from the thin film and the reflected light from the multilayer reflective film with respect to light.

[0022] (Composition 11) A method for manufacturing a semiconductor device, comprising the step of using a reflective mask described in any of configurations 6 to 10 to expose and transfer the transfer pattern onto a resist film on a semiconductor substrate. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a mask blank that can be used to manufacture a reflective mask that exhibits excellent transfer characteristics when exposure transfer is performed using an EUV exposure apparatus.

[0024] Furthermore, according to the present invention, it is possible to provide a reflective mask that can exhibit excellent transfer characteristics when exposure transfer is performed with an EUV exposure apparatus, a method for manufacturing the same, and a method for manufacturing a semiconductor device using the reflective mask. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic cross-sectional view of a key part illustrating an example of the schematic configuration of a reflective mask blank according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional diagram illustrating an example of the general configuration of a reflective mask based on a reflective mask blank. [Figure 3] This graph shows the relationship between the reflectance on a multilayer reflective film and the wavelength when EUV light is used as the exposure light in a reflective mask blank according to an embodiment of the present invention. [Modes for carrying out the invention]

[0026] The embodiments of the present invention will be described below, but first, the background to the present invention will be explained. The inventors diligently studied means that can exhibit excellent transfer characteristics when exposure transfer is performed with an EUV exposure apparatus. The inventors of this invention hypothesized that by considering wavelength bands other than the central wavelength of EUV light when selecting the material for the absorber film constituting the pattern-forming thin film, the optical properties of the absorber pattern of the reflective mask can be improved. This will be explained using Figure 3. Figure 3 is a graph showing the relationship between the reflectance on the multilayer reflective film and the wavelength when EUV light is used as the exposure light in a reflective mask blank according to an embodiment of the present invention. As can be seen from the figure, the EUV light incident on the multilayer reflective film in an EUV exposure apparatus has a certain amplitude not only at the central wavelength of 13.5 nm, but also in the wavelength bands near it. As shown in the figure, the multilayer reflective film has a high reflectance of over 70% at the central wavelength of 13.5 nm, but it also has a reflectance that cannot be ignored in the wavelength bands near it. For example, it has a reflectance of over 10% in the wavelength band from 13.0 nm to 14.0 nm, and a reflectance of over 30% in the wavelength band from 13.2 nm to 13.8 nm.

[0027] The refractive index n of the film material changes with the wavelength of the exposure light. On the other hand, in a reflective mask, the phase difference φ between the EUV light reflected from the multilayer reflective film and the EUV light reflected from the absorber film can be calculated using the following relation (1) with respect to the wavelength of light λ, the refractive index n at that wavelength λ, and the film thickness d (the optical path difference is 2d because it is a reflective type). Phase difference φ between EUV light reflected from a multilayer reflective film and EUV light reflected from an absorbing film: 2π(1-n)×2d / λ=4π(1-n)d / λ…(1) It is hypothesized that the phase shift effect improves as the phase difference φ approaches the same value for each wavelength of EUV light with a wavelength band (i.e., the variation Δφ in the phase difference φ for each wavelength of EUV light with a wavelength band is small).

[0028] In equation (1) above, the film thickness d is constrained from the viewpoint of optical properties. For this reason, we focused on the 4π(1-n) / λ portion of equation (1) above, excluding the film thickness d. After thorough consideration, the wavelength λ L =13.2nm, λ M=13.5nm, λ H = The refractive indices of the thin film for each light at 13.8 nm are n L , n M , n H Let the coefficient A L = 4π × (1-n L ) / λ L , A M = 4π × (1-n M ) / λ M , A H = 4π × (1-n H ) / λ H , coefficient P=(A H -A L ) / A M When a thin film satisfying the condition |P|≦0.09 is used, then when exposure transfer is performed using an EUV lithography apparatus, the wavelength band of EUV light λ L =13.2nm~λ H = Phase difference φ at 13.8 nm L ~φ H Variation Δφ(=φ H -φ L Hereafter, this will also simply be referred to as "phase difference Δφ". We concluded that the magnitude of () can be kept below 20 degrees, and excellent transcription characteristics can be expressed. Here, the coefficient P can be expanded as follows. Coefficient P = (A H -A L ) / A M =[(1-n H ) / λ H -(1-n L ) / λ L ] / [(1-n M ) / λ M ]

[0029] This invention was made as a result of the diligent research described above. The method for deriving the coefficient P described above does not limit the scope of the rights of this invention (coefficient A L , A M , A H (This is not an essential element of the present invention.) In this embodiment, the central wavelength λ of EUV light M Phase difference φ MThe design is such that the angle is approximately 1.2π (approximately 216 degrees). This is because, due to the occurrence of double diffraction by the reflective optical system, the absorber pattern, and the influence of the multilayer film, the effective reflective surface is located closer to the substrate than the interface between the absorber film and the multilayer reflective film. However, the present invention is not limited to this, and for example, the central wavelength λ of EUV light M Phase difference φ M It can also be applied to thin films for pattern formation designed so that the phase difference is π (180 degrees). M If we set it so that it is π (180 degrees), then the wavelength band of EUV light (λ L ~λ H In this case, by making the absolute value of the coefficient P 0.09 or less, the phase difference Δφ(=φ H -φ L The size of the ) can be kept below 17 degrees.

[0030] The embodiments of the present invention will be described in detail below with reference to the drawings. The following embodiments are merely examples of how the present invention can be implemented, and do not limit the present invention to their scope. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and their descriptions may be simplified or omitted.

[0031] <Construction of reflective mask blank 100 and method for manufacturing the same> Figure 1 is a schematic cross-sectional view of the main parts illustrating the configuration of the reflective mask blank 100 of this embodiment. As shown in Figure 1, the reflective mask blank 100 has a substrate 1, a multilayer reflective film 2, a protective film 3, and an absorber film 4, which are stacked in this order. The multilayer reflective film 2 is formed on the first main surface (front surface) and reflects EUV light, which is the exposure light, with high reflectivity. The protective film 3 is provided to protect the multilayer reflective film 2 and is made of a material that is resistant to the etchant and cleaning solution used when patterning the absorber film 4, which will be described later. The absorber film 4 absorbs EUV light and has a phase shift function. In addition, a conductive film (not shown) for an electrostatic chuck is formed on the second main surface (back surface) of the substrate 1. Note that an etching mask film may be provided on the absorber film 4.

[0032] In this specification, "having a multilayer reflective film 2 on the main surface of the substrate 1" means that the multilayer reflective film 2 is placed in contact with the surface of the substrate 1, as well as meaning that there is another film between the substrate 1 and the multilayer reflective film 2. The same applies to other films. For example, "having a film B on a film A" means that film A and film B are placed in direct contact, as well as meaning that there is another film between film A and film B. Also, in this specification, for example, "film A is placed in contact with the surface of film B" means that film A and film B are placed in direct contact without any other film in between them.

[0033] The following describes this embodiment layer by layer.

[0034] <<Circuit Board 1>> To prevent distortion of the absorber pattern (transfer pattern) 4a (see Figure 2) due to heat during exposure with EUV light, the substrate 1 preferably has a low thermal expansion coefficient within the range of 0 ± 5 ppb / °C. Examples of materials with a low thermal expansion coefficient in this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0035] The first main surface of the substrate 1 on the side where the transfer pattern (corresponding to the absorber pattern 4a described later) is formed is surface-processed to achieve high flatness, at least from the viewpoint of obtaining pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness of the 132 mm × 132 mm area of ​​the main surface (first main surface) on the side where the transfer pattern of the substrate 1 is formed is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. The second main surface on the side opposite to the side where the transfer pattern is formed is the surface that is electrostatically chucked when set in the exposure apparatus, and the flatness of the 132 mm × 132 mm area is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Furthermore, the flatness of the second main surface side of the reflective mask blank 100 is preferably 1 μm or less in a 142 mm × 142 mm area, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.

[0036] Furthermore, the surface smoothness of the substrate 1 is also an extremely important factor. The surface roughness of the first main surface of the substrate 1 is preferably 0.1 nm or less in terms of root mean square roughness (RMS). Surface smoothness can be measured using an atomic force microscope.

[0037] Furthermore, it is preferable that the substrate 1 has high rigidity in order to suppress deformation due to film stress of the film (such as the multilayer reflective film 2) formed thereon. In particular, it is preferable that the substrate 1 has a high Young's modulus of 65 GPa or more.

[0038] <<Multilayer reflective film 2>> The multilayer reflective film 2 provides the reflective mask 200 with the function of reflecting EUV light, and is a multilayer film in which each layer, mainly composed of elements with different refractive indices, is periodically stacked.

[0039] Generally, a multilayer film is used as the multilayer reflective film 2, in which thin films of light elements or compounds that are high refractive index materials (high refractive index layer) and thin films of heavy elements or compounds that are low refractive index materials (low refractive index layer) are alternately stacked for about 40 to 60 periods. The multilayer film may be stacked in multiple periods, with a high refractive index layer / low refractive index layer stacking structure, where the high refractive index layer and low refractive index layer are stacked in this order from the substrate 1 side, as one period. Alternatively, the multilayer film may be stacked in multiple periods, with a low refractive index layer / high refractive index layer stacking structure, where the low refractive index layer and high refractive index layer are stacked in this order from the substrate 1 side, as one period. It is preferable that the outermost layer of the multilayer reflective film 2, i.e., the surface layer of the multilayer reflective film 2 opposite to the substrate 1, be a high refractive index layer. In the above-described multilayer film, when multiple periods are stacked with a high refractive index layer / low refractive index layer stacking structure, where the high refractive index layer and low refractive index layer are stacked in this order from the substrate 1 side, the uppermost layer becomes a low refractive index layer. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 2, it will be easily oxidized, and the reflectivity of the reflective mask 200 will decrease. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form a multilayer reflective film 2. On the other hand, in the above-described multilayer film, if a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 1 side, and multiple periods of stacking are performed with this low refractive index layer / high refractive index layer structure as one period, the uppermost layer will be the high refractive index layer, so it is fine as is.

[0040] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. As the Si-containing material, in addition to elemental Si, Si compounds containing boron (B), carbon (C), nitrogen (N), and oxygen (O) can be used. By using a Si-containing layer as the high refractive index layer, a reflective mask 200 for EUV lithography with excellent EUV light reflectivity can be obtained. Furthermore, in this embodiment, a glass substrate is preferably used as the substrate 1. Si also exhibits excellent adhesion to the glass substrate. As the low refractive index layer, elemental metals selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, can be used. For example, as the multilayer reflective film 2 for EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic multilayer film is preferably used, in which Mo films and Si films are alternately stacked for approximately 40 to 60 periods. The high refractive index layer, which is the uppermost layer of the multilayer reflective film 2, may also be formed of silicon (Si).

[0041] The reflectivity of the multilayer reflective film 2 alone is typically 65% ​​or higher, with an upper limit of typically 73%. The film thickness and period of each constituent layer of the multilayer reflective film 2 can be appropriately selected according to the exposure wavelength, and are chosen to satisfy Bragg's law of reflection. While multiple high-refractive-index layers and low-refractive-index layers exist in the multilayer reflective film 2, the film thicknesses of the high-refractive-index layers and the low-refractive-index layers do not necessarily have to be the same. Furthermore, the film thickness of the outermost Si layer of the multilayer reflective film 2 can be adjusted within a range that does not reduce reflectivity. The film thickness of the outermost Si layer (high-refractive-index layer) can be in the range of 3 nm to 10 nm.

[0042] The method for forming the multilayer reflective film 2 is known in the art. For example, it can be formed by depositing each layer of the multilayer reflective film 2 using an ion beam sputtering method. In the case of the Mo / Si periodic multilayer film described above, for example, a Si film with a thickness of about 4 nm is first deposited on the substrate 1 using a Si target by an ion beam sputtering method. Then, a Mo film with a thickness of about 3 nm is deposited using a Mo target. This Si film / Mo film is considered as one period, and 40 to 60 periods are stacked to form the multilayer reflective film 2 (the outermost layer is the Si layer). For example, if the multilayer reflective film 2 has 60 periods, the number of steps increases compared to 40 periods, but the reflectivity to EUV light can be increased. Furthermore, it is preferable to form the multilayer reflective film 2 by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering during the deposition of the multilayer reflective film 2.

[0043] <<Protective film 3>> In this embodiment, the reflective mask blank 100 preferably includes a protective film 3 between the multilayer reflective film 2 and the absorber film 4.

[0044] To protect the multilayer reflective film 2 from dry etching and cleaning during the manufacturing process of the reflective mask 200 described later, a protective film 3 can be formed on or in contact with the surface of the multilayer reflective film 2. The protective film 3 is made of a material that is resistant to the etchant used when patterning the absorber film 4 and to cleaning solutions. By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 can be suppressed when manufacturing the reflective mask 200 (EUV mask) using the substrate 1 having the multilayer reflective film 2 and the protective film 3. As a result, the reflectivity characteristics of the multilayer reflective film 2 to EUV light are improved.

[0045] If the absorber film 4 in contact with the surface of the protective film 3 is a thin film made of a ruthenium (Ru)-containing material (Ru-based material), then the material of the protective film 3 can be selected from silicon-based materials such as silicon (Si), silicon (Si) and oxygen (O), silicon (Si) and nitrogen (N), or silicon (Si), oxygen (O) and nitrogen (N). On the other hand, if the absorber film 4 in contact with the surface of the protective film 3 is a thin film made of a tantalum-based material or a chromium-based material, it is preferable that the protective film 3 contains ruthenium. The material of the protective film 3 may be pure Ru metal, or it may be a Ru alloy containing Ru and at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and may also contain nitrogen.

[0046] In EUV lithography, since there are few materials that are transparent to exposure light, the EUV pellicle, which prevents foreign matter from adhering to the mask pattern surface, is not technically easy to manufacture. For this reason, pellicle-less operation is the mainstream. In addition, in EUV lithography, exposure contamination occurs, such as the deposition of carbon films or the growth of oxide films on reflective masks due to EUV exposure. Therefore, when using the reflective mask 200 for EUV exposure in the manufacturing of semiconductor devices, it is necessary to frequently clean the mask to remove foreign matter and contamination. For this reason, the reflective mask 200 for EUV exposure requires a level of mask cleaning resistance that is orders of magnitude higher than that of transmissive masks for photolithography. By having a protective film 3 in the reflective mask 200, its cleaning resistance to cleaning solutions can be increased.

[0047] The thickness of the protective film 3 is not particularly limited as long as it can perform the function of protecting the multilayer reflective film 2. From the viewpoint of EUV light reflectance, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0048] The method for forming the protective film 3 can be any known film formation method without any particular limitations. Specific examples include sputtering and ion beam sputtering.

[0049] <<Absorbing membrane>> In the reflective mask blank 100 of this embodiment, an absorber film (a thin film for pattern formation) 4 is formed on the multilayer reflective film 2, or on the protective film 3 formed on the multilayer reflective film 2. In the state of the reflective mask 200, an absorber pattern 4a is formed on the absorber film 4, and this absorber pattern 4a constitutes the transfer pattern. The relative reflectance R of the absorber film 4 with respect to the reflectance of the multilayer reflective film 2 at EUV exposure light (center wavelength of 13.5 nm) is preferably 1% or more, and more preferably 2% or more. Furthermore, this relative reflectance R is preferably 40% or less. This is to ensure sufficient contrast in mask inspection with respect to EUV exposure light and to ensure sufficient contrast in the pattern image during exposure transfer.

[0050] In the reflective mask 200 described later in this embodiment, the portion where the absorber film 4 (absorber pattern 4a) is provided absorbs EUV light and attenuates it while reflecting some of the light at a level that does not adversely affect pattern transfer. On the other hand, in the aperture (the portion where the absorber film 4 is not present), EUV light is reflected from the multilayer reflective film 2 (or from the multilayer reflective film 2 via the protective film 3, if present). The reflected light from the portion where the absorber film 4 is formed forms a desired phase difference with the reflected light from the aperture. The absorber film 4 has a wavelength λ M For light of 13.5 nm, the phase difference between the reflected light from the absorber film 4 and the reflected light from the multilayer reflective film 2 is formed to be between 130 and 230 degrees. The light with inverted phase differences of around 180 degrees or around 220 degrees interferes with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast leads to increased resolution, and various exposure-related margins such as exposure margin and focus margin are expanded.

[0051] The absorber film 4 is made of a material containing a metal element. This metal element can be a metal element in a broad sense and can be selected from alkali metals, alkaline earth metals, transition metals, and metalloids. The absorber film 4 can be selected from the above-mentioned broad sense of metal elements as long as it has an etching selectivity with the multilayer reflection film 2 (in the case where the protective film 3 is formed, the etching selectivity with the protective film 3). For example, chromium (Cr), vanadium (V), palladium (Pd), titanium (Ti), iridium (Ir), Rh (rhodium), tantalum (Ta), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tin (Sn), platinum (Pt), etc. can be used as the metal element contained in the absorber film 4. In addition, the absorber film 4 can contain at least one selected from oxygen, nitrogen, carbon, and boron without departing from the effects of the present invention.

[0052] For the absorber film 4, its wavelength λ L = 13.2 nm, the refractive index for light is n L ; for wavelength λ M = 13.5 nm, the refractive index for light is n M ; for wavelength λ H = 13.8 nm, the refractive index for light is n H ; when the coefficient P = [(1 - n H ) / λ H - (1 - n L ) / λ L / [(1 - n M ) / λ M , the absolute value of the coefficient P is 0.09 or less. Thereby, when performing exposure transfer with an EUV exposure apparatus, the magnitude of the phase difference Δφ (= φ L - φ H ) in the EUV light in the wavelength band λ H - φ L ) can be suppressed to 20 degrees or less. In addition, the absorber film 4 has a wavelength band λ of EUV light L = 13.2 nm to λ HWhen the absolute value of the coefficient P is 0.085 or less at 13.8 nm, it is preferable in that the phase difference Δφ can be suppressed within 18 degrees. And the absorber film 4 is in the wavelength band λ of EUV light L = 13.2 nm to λ H When the absolute value of the coefficient P is 0.07 or less at 13.8 nm, it is more preferable in that the phase difference Δφ can be suppressed within 15 degrees. Furthermore, the absorber film 4 is in the wavelength band λ of EUV light L = 13.2 nm to λ H When the absolute value of the coefficient P is 0.045 or less at 13.8 nm, it is even more preferable in that the phase difference Δφ can be suppressed within 10 degrees. The absorber film 4 has a refractive index n for light with a wavelength λ L = 13.0 nm, a refractive index n for light with a wavelength λ L = 13.5 nm, a refractive index n for light with a wavelength λ M = 14.0 nm, and when the coefficient P = [(1 - n M ) / λ H - (1 - n H ) / λ H / [(1 - n H ) / λ L , the absolute value of the coefficient P is 0.15 or less. Thereby, when performing exposure and transfer with an EUV exposure apparatus, the magnitude of the phase difference Δφ (= φ L - φ M ) in the EUV light in the wavelength band λ M to λ L can be suppressed to 35 degrees or less. H H - φ L Also, when the absolute value of the coefficient P is 0.14 or less at 13.0 nm to λ L = 14.0 nm in the wavelength band λ of the absorber film for EUV light, it is preferable in that the phase difference Δφ can be suppressed within 30 degrees. And the absorber film 4 is in the wavelength band λ of EUV light H = 13.0 nm to λ L = 13.0 nm to λ HAt λ = 14.0 nm, it is more preferable if the absolute value of the coefficient P is 0.11 or less, as this allows the phase difference Δφ to be kept within 25 degrees. Furthermore, the absorber film 4 is in the wavelength band λ of EUV light. L =13.0nm~λ H At 14.0 nm, it is even more preferable if the absolute value of the coefficient P is 0.09 or less, as this allows the phase difference Δφ to be kept within 20 degrees.

[0053] As mentioned above, the material for the absorber membrane 4 is not particularly limited, but tantalum-based materials and chromium-based materials can be preferably used. As for tantalum-based materials, in addition to tantalum metal, it is preferable to use materials containing tantalum (Ta) with one or more elements selected from nitrogen (N), oxygen (O), boron (B), and carbon (C). In particular, it is preferable to use materials containing tantalum (Ta) and at least one element selected from oxygen (O) and boron (B). Furthermore, when the absorber membrane 4 is formed from a chromium-containing material, in addition to chromium metal, it is preferable to use materials containing chromium (Cr) with one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F). Materials containing chromium (Cr) nitride are particularly preferred.

[0054] Furthermore, the wavelength λ of the absorber membrane 4 M Refractive index n for light at (=13.5 nm) M The refractive index n of the absorber film 4 is preferably 0.960 or less, and more preferably 0.955 or less. M It is preferable that the value is 0.850 or higher, and more preferably 0.870 or higher. Wavelength λ of the absorber membrane 4 M Extinction coefficient k for light M The extinction coefficient k of the absorber film 4 is preferably 0.10 or less, more preferably 0.08 or less, and even more preferably 0.05 or less. Based on the results of optical simulations, the light intensity of the reflected light from the multilayer reflective film 2 is stronger than the reflected light from the absorber film 4 for light with a wavelength of 13.5 nm, and the extinction coefficient k of the absorber film 4 is MIt is presumed that as k increases, the reflected light from the absorber membrane 4 decreases. Extinction coefficient k M It is preferable to set the range described above, as this is presumed to suppress the decrease in reflected light from the absorber film 4.

[0055] Depending on the pattern and exposure conditions, the absolute reflectance of the transfer pattern (absorber pattern 4a) to EUV light (center wavelength of 13.5 nm) is preferably 1% to 30%, and more preferably 2% to 25%, in order to obtain a phase shift effect.

[0056] The phase difference and reflectance of the absorber film 4 are determined by the refractive index n in EUV exposure light. L , n M , n H Extinction coefficient k L , k M , k H The film thickness d can be adjusted by changing the film thickness. The film thickness of the absorber film 4 is preferably less than 100 nm, more preferably 98 nm or less, and even more preferably 90 nm or less. The film thickness of the absorber film 4 is preferably 30 nm or more. If a protective film 3 is present, the phase difference and reflectance of the absorber film 4 can also be adjusted by considering the refractive index n, extinction coefficient k, and film thickness of the protective film 3.

[0057] The absorber film 4 of the specified material described above can be formed by known sputtering methods such as DC sputtering and RF sputtering, as well as reactive sputtering methods using oxygen gas, etc. The target may contain one type of metal, and if the absorber film 4 is composed of two or more types of metals, an alloy target containing two or more types of metals (for example, Ru and Cr) can be used. Furthermore, if the absorber film 4 is composed of two or more types of metals, the thin film constituting the absorber film 4 can be formed by coarse sputtering using, for example, a Ru target and a Cr target. The absorber membrane 4 may be a multilayer membrane containing two or more layers. In this case, it is preferable that the absolute value of the coefficient P is 0.09 or less in all layers of the absorber membrane 4.

[0058] <<Etching Mask Film>> An etching mask film (not shown) can be formed on or in contact with the surface of the absorber film 4. The etching mask film is made of a material that increases the etching selectivity ratio of the absorber film 4 to the etching mask film. Here, "etching selectivity ratio of B to A" refers to the ratio of the etching rates of layer A, which does not need to be etched (the mask layer), and layer B, which needs to be etched. Specifically, it is determined by the formula "etching selectivity ratio of B to A = etching rate of B / etching rate of A". Furthermore, "high selectivity ratio" means that the value of the selectivity ratio as defined above is large compared to the comparison target. The etching selectivity ratio of the absorber film 4 to the etching mask film is preferably 1.5 or higher, and more preferably 3 or higher.

[0059] The thickness of the etching mask film is preferably 2 nm or more, from the viewpoint of obtaining its function as an etching mask that accurately forms the transfer pattern on the absorber film 4. Furthermore, from the viewpoint of reducing the thickness of the resist film, the thickness of the etching mask film is preferably 15 nm or less.

[0060] <<Conductive film>> Generally, a conductive film (not shown) for electrostatic chucks is formed on the second main surface (back surface) of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The electrical properties (sheet resistance) required for the conductive film for electrostatic chucks are usually 100 Ω / □ (Ω / Square) or less. The conductive film can be formed, for example, by magnetron sputtering or ion beam sputtering, using metal and alloy targets such as chromium (Cr) and tantalum (Ta).

[0061] The chromium (Cr)-containing material of the conductive film is preferably a Cr compound that contains Cr and at least one selected from boron (B), nitrogen (N), oxygen (O), and carbon (C).

[0062] As the tantalum (Ta)-containing material for the conductive film, it is preferable to use Ta (tantalum), a Ta-containing alloy, or a Ta compound that contains at least one of boron, nitrogen, oxygen, and carbon in addition to any of the above.

[0063] The thickness of the conductive film is not particularly limited as long as it satisfies its function as an electrostatic chuck. The thickness of the conductive film is usually between 10 nm and 200 nm. Furthermore, this conductive film also serves to adjust the stress on the second main surface side of the mask blank 100. That is, the conductive film is adjusted to balance the stress from the various films formed on the first main surface side so that a flat reflective mask blank 100 can be obtained.

[0064] <Reflective mask 200 and method for manufacturing the same> The reflective mask 200 of this embodiment has a transfer pattern (absorber pattern 4a) formed on the absorber film 4 of the reflective mask blank 100. The absorber film 4 (absorber pattern 4a) on which the transfer pattern is formed is the same as the absorber film 4 of the reflective mask blank 100 of this embodiment described above. The transfer pattern (absorber pattern 4a) can be formed by patterning the absorber film 4 of the reflective mask blank 100 of this embodiment described above. The patterning of the absorber film 4 can be performed with a predetermined dry etching gas. The absorber pattern 4a of the reflective mask 200 absorbs EUV light and can also reflect some EUV light with a predetermined phase difference from the aperture (the part where the absorber pattern 4a is not formed). The predetermined dry etching gas can be a mixture of chlorine-based gas and oxygen gas, oxygen gas, and fluorine-based gas, etc. To pattern the absorber pattern 4a, an etching mask film can be provided on the absorber pattern 4a as needed. In that case, the etching mask pattern can be used as a mask to dry etch the absorber film 4 and form the absorber pattern 4a.

[0065] A method for manufacturing a reflective mask 200 using the reflective mask blank 100 of this embodiment will be described.

[0066] A reflective mask blank 100 is prepared, and a resist film is formed on the absorber film 4 of its first main surface (this step is unnecessary if the reflective mask blank 100 already has a resist film). A desired transfer pattern is drawn (exposed) onto this resist film, and then developed and rinsed to form a predetermined resist pattern (a resist film having a transfer pattern).

[0067] Next, using this resist pattern as a mask, the absorber film 4 is etched to form an absorber pattern 4a (an absorber film 4 having a transfer pattern). After forming the absorber pattern 4a, the remaining resist pattern is removed (if an etching mask film is formed, the etching mask film is etched using the resist pattern as a mask to form an etching mask pattern, this etching mask pattern is used as a mask to form the absorber pattern 4a, and then the etching mask pattern is removed). Finally, the reflective mask 200 of this embodiment is manufactured by wet cleaning using an acidic or alkaline aqueous solution.

[0068] <Manufacturing methods for semiconductor devices> This embodiment is a method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the reflective mask 200 described above, or a reflective mask 200 manufactured by the method for manufacturing the reflective mask 200 described above. By setting the reflective mask 200 of this embodiment in an exposure apparatus having an EUV light exposure source and transferring the transfer pattern onto a resist film formed on the substrate to be transferred, a semiconductor device can be manufactured. Therefore, a semiconductor device having a fine and high-precision transfer pattern can be manufactured.

[0069] [Examples and Comparative Examples] Examples 1-16, Comparative Examples 1, 2 Examples 1 to 16 and Comparative Examples 1 and 2 will be described below with reference to the drawings. This embodiment is not limited to these examples. In the examples, the same reference numerals are used for similar components, and their descriptions are simplified or omitted.

[0070] Examples 1 to 16 and Comparative Examples 1 and 2 describe the method for manufacturing a reflective mask blank 100.

[0071] A SiO2-TiO2 glass substrate, a low thermal expansion glass substrate of size 6025 (approximately 152 mm x 152 mm x 6.35 mm), with both the first and second main surfaces polished, was prepared and designated as substrate 1. Polishing was performed, consisting of a rough polishing process, a precision polishing process, a localized polishing process, and a touch polishing process, to obtain a flat and smooth main surface.

[0072] Next, a conductive film made of CrN was formed on the second main surface (back surface) of the SiO2-TiO2 glass substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. The conductive film was deposited using a Cr target in a mixed gas atmosphere of argon (Ar) gas and nitrogen (N2) gas to a thickness of 20 nm.

[0073] Next, a multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 opposite to the side where the conductive film was formed. To make the multilayer reflective film 2 formed on the substrate 1 suitable for EUV light with a wavelength of 13.5 nm, a periodic multilayer reflective film made of molybdenum (Mo) and silicon (Si) was formed. The multilayer reflective film 2 was formed by alternately stacking Mo layers and Si layers on the substrate 1 using an ion beam sputtering method in a krypton (Kr) gas atmosphere with a Mo target and a Si target. First, a Si film was deposited with a thickness of 4.2 nm, followed by a Mo film with a thickness of 2.8 nm. This constituted one period, and 40 periods were stacked in the same manner, and finally a Si film with a thickness of 4.0 nm was deposited to form the multilayer reflective film 2.

[0074] Subsequently, a protective film 3 was deposited on the surface of the multilayer reflective film 2 to a thickness of 3.5 nm by sputtering in an Ar gas atmosphere. In Examples 1 to 16 and Comparative Examples 1 and 2 described above, the material for the protective film 3 was appropriately selected to have etching resistance to the dry etching gas used when patterning the absorber film 4.

[0075] Subsequently, an absorber film 4 was deposited on the surface of the protective film 3 by sputtering in an Ar gas atmosphere. In Examples 1 to 16 and Comparative Examples 1 and 2 described above, the constituent elements of the absorber film 4 are shown in Tables 1-1 and 1-2 below, and a sputtering target suitable for each constituent element was appropriately selected. In Examples 1 to 16 and Comparative Examples 1 and 2 described above, the absorber film 4 was deposited at the center wavelength λ of EUV light. M Phase difference φ M It is designed so that the angle is 1.2π (216 degrees). Subsequently, reflective mask blanks 100 for Examples 1-16 and Comparative Examples 1 and 2 were manufactured by performing predetermined cleaning processes.

[0076] Next, for the reflective mask blanks 100 in Examples 1 to 16 and Comparative Examples 1 and 2, a resist pattern was formed as described in the method for manufacturing the reflective mask 200 above. Using the resist pattern as a mask, the absorber film 4 was etched to form an absorber pattern 4a (absorber film 4 having a transfer pattern), and the reflective masks 200 in Examples 1 to 16 and Comparative Examples 1 and 2 were manufactured by wet cleaning using acidic or alkaline aqueous solutions.

[0077] In Examples 1-16 and Comparative Examples 1 and 2, the constituent elements of the absorber film 4 and the central wavelength λ of EUV light in the reflective mask blank 100 and reflective mask 200 were determined. M (=13.5nm) refractive index n M and the extinction coefficient k M , wavelength λ L =13.2nm, λ M =13.5nm, λ H = Coefficient A at 13.8 nm L= 4π × (1-n L ) / λ L , A M = 4π × (1-n M ) / λ M , A H = 4π × (1-n H ) / λ H , film thickness d, EUV light wavelength band λ L =13.2nm~λ H = At 13.8 nm, coefficient P = (A H -A L ) / A M (=[(1-n H ) / λ H -(1-n L ) / λ L ] / [(1-n M ) / λ M The phase difference Δφ is shown in Tables 1-1 and 1-2.

[0078] [Table 1-1]

[0079] [Table 1-2]

[0080] As shown in Tables 1-1 and 1-2, the absorber films 4 shown in Examples 1 to 16 all have a film thickness of less than 100 nm and are in the wavelength band λ of EUV light. L =13.2nm~λ H At λ = 13.8 nm, the absolute value of the coefficient P is 0.09 or less, and the phase difference Δφ can be kept within 20 degrees. The absorber film 4 shown in Examples 1-11 and 16 further... L =13.2nm~λ H At λ = 13.8 nm, the absolute value of the coefficient P is 0.085 or less, and the phase difference Δφ can be kept within 18 degrees. Furthermore, the absorber film 4 shown in Examples 1-6 and 16 is in the wavelength band λ of EUV light. L =13.2nm~λ HAt λ = 13.8 nm, the absolute value of the coefficient P is 0.07 or less, and the phase difference Δφ can be kept within 15 degrees. Furthermore, the absorber film 4 shown in Examples 1 to 3 is in the wavelength band λ of EUV light. L =13.2nm~λ H At 13.8 nm, the absolute value of the coefficient P is 0.045 or less, and the phase difference Δφ can be kept within 10 degrees.

[0081] On the other hand, in Comparative Example 1, the wavelength band λ of EUV light L =13.2nm~λ H At 13.8 nm, the phase difference Δφ of the absorber film 4 is 22.49, which is more than 20 degrees, indicating a phase difference Δφ that cannot be ignored. Furthermore, in Comparative Example 2, the film thickness of the absorber film 4 is 183.31 nm, which is significantly higher than less than 100 nm.

[0082] Furthermore, Tables 1-1 and 1-2 show the wavelength band λ of EUV light for Examples 1-16 and Comparative Examples 1 and 2. L =13.0nm~λ H = coefficient A at 14.0 nm L = 4π × (1-n L ) / λ L , A H = 4π × (1-n H ) / λ H , coefficient P=(A H -A L ) / A M The phase difference Δφ is also shown. As shown in Tables 1-1 and 1-2, the absorber film 4 shown in Examples 1 to 16 is in the wavelength band λ of EUV light. L =13.0nm~λ H At λ = 14.0 nm, the absolute value of the coefficient P is 0.15 or less, and the phase difference Δφ can be kept within 35 degrees. Furthermore, the absorber film 4 shown in Examples 1-12 and 16 is in the wavelength band λ of EUV light. L =13.0nm~λ H At λ = 14.0 nm, the absolute value of the coefficient P is 0.14 or less, and the phase difference Δφ can be kept within 30 degrees. Furthermore, the absorber film 4 shown in Examples 1-6 and 16 is in the wavelength band λ of EUV light. L=13.0nm~λ H At λ = 14.0 nm, the absolute value of the coefficient P is 0.11 or less, and the phase difference Δφ can be kept within 25 degrees. Furthermore, the absorber film 4 shown in Examples 1-5 and 16 is in the wavelength band λ of EUV light. L =13.0nm~λ H At 14.0 nm, the absolute value of the coefficient P is 0.09 or less, and the phase difference Δφ can be kept within 20 degrees.

[0083] Furthermore, the constituent elements of the absorber film 4 and the wavelength λ in the reflective mask blank 100 and reflective mask 200 in Examples 1-16 and Comparative Examples 1 and 2 are also discussed. L =13.2nm, λ M =13.5nm, λ H = coefficient E at 13.8 nm L =4π×(1-k L ) / λ L , E M =4π×(1-k M ) / λ M , E H =4π×(1-k H ) / λ H , the wavelength band of EUV light λ L =13.2nm~λ H = At 13.8 nm, the coefficient F = (E H -E L ) / E M (=[(1-k H ) / λ H -(1-k L ) / λ L ] / [(1-k M ) / λ M Regarding ]), see Tables 2-1 and 2-2 (k L , k M , k H is the wavelength λ L =13.2nm, λ M =13.5nm, λ H = This is the extinction coefficient at 13.8 nm. Tables 2-1 and 2-2 show the wavelength band λ of EUV light for Examples 1-16 and Comparative Examples 1 and 2. L =13.0nm~λ H = coefficient E at 14.0 nm L=4π×(1-k L ) / λ L , E M =4π×(1-k M ) / λ M , E H =4π×(1-k H ) / λ H , the wavelength band of EUV light λ L =13.0nm~λ H = At 14.0 nm, the coefficient F = (E H -E L ) / E M (=[(1-k H ) / λ H -(1-k L ) / λ L ] / [(1-k M ) / λ M ]) is also shown.

[0084] [Table 2-1]

[0085] [Table 2-2]

[0086] Regarding the extinction coefficient k, no significant difference was found in Examples 1-16 and Comparative Examples 1 and 2.

[0087] The reflective masks 200 obtained in Examples 1 to 16 were set in an EUV scanner, and EUV exposure was performed on a wafer on which the workpiece film and the resist film had been formed on the semiconductor substrate. By developing the exposed resist film, the workpiece film formed a resist pattern on the semiconductor substrate.

[0088] The reflective mask 200 obtained in Examples 1 to 16 has a central wavelength λ of EUV light. M Phase difference φ M λ is 1.2π, and the wavelength band of EUV light is λ L =13.2nm~λ HAt λ = 13.8 nm, the absolute value of the coefficient P is 0.09 or less, and the absorber pattern 4a is provided. As a result, when EUV light is used as the exposure light, the wavelength band of the EUV light λ L =13.2nm~λ H At 13.8 nm, the phase difference Δφ could be kept within 20 degrees, enabling the precise formation of the required fine patterns and the manufacture of semiconductor devices with fine and highly accurate transfer patterns.

[0089] Furthermore, by transferring this resist pattern to the workpiece through etching, and then going through various processes such as forming insulating films and conductive films, introducing dopants, or annealing, we were able to manufacture semiconductor devices with desired properties with a high yield.

[0090] The reflective mask 200 of Comparative Example 1 is in the wavelength band λ of EUV light. L =13.2nm~λ H At λ = 13.8 nm, the absorber pattern 4a has an absolute value of coefficient P greater than 0.09. As a result, when EUV light is used as the exposure light, the wavelength band of the EUV light λ L =13.2nm~λ H At 13.8 nm, the phase difference Δφ could not be kept within 20 degrees (22.49 degrees), and the phase shift effect could not be sufficiently obtained. As a result, it was not possible to accurately form the required fine patterns, and semiconductor devices with fine and high-precision transfer patterns could not be manufactured.

[0091] Furthermore, even after transferring this resist pattern to the workpiece by etching, and undergoing various processes such as forming insulating films, conductive films, introducing dopants, or annealing, it was not possible to manufacture semiconductor devices with the desired characteristics with a high yield.

[0092] In Comparative Example 2, the reflective mask 200 had an absorber film 4 made of SiO2 and did not contain any metal elements. As a result, the thickness of the absorber film 4 was 184.31 nm, significantly exceeding 100 nm, making it impossible to obtain good transfer characteristics and thus impossible to manufacture a semiconductor device with a fine and high-precision transfer pattern.

[0093] Furthermore, even after transferring this resist pattern to the workpiece by etching, and undergoing various processes such as forming insulating films, conductive films, introducing dopants, or annealing, it was not possible to manufacture semiconductor devices with the desired characteristics with a high yield. [Explanation of Symbols]

[0094] 1 circuit board 2 Multilayer reflective film 3 Protective film 4. Absorber membrane (thin film for pattern formation) 4a Absorber pattern (transfer pattern) 100 Reflective Mask Blanks 200 Reflective Masks

Claims

1. A mask blank in which a multilayer reflective film and a thin film for pattern formation are provided in this order on the main surface of the substrate, The thin film is made of a material containing at least one selected from chromium (Cr), vanadium (V), palladium (Pd), titanium (Ti), iridium (Ir), Rh (rhodium), tantalum (Ta), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tin (Sn), and platinum (Pt). The thickness of the thin film is 32.40 nm or more and 98 nm or less. The wavelength λ of the thin film L = The refractive index for light at 13.0 nm is n L , The wavelength λ of the thin film M = The refractive index for light at 13.5 nm is n M , The wavelength λ of the thin film H = The refractive index for light at 14.0 nm is n H , Coefficient P = [(1 - n H ) / λ H - (1 - n L ) / λ L / [(1 - n M ) / λ M , when A mask blank characterized in that the absolute value of the coefficient P is 0.15 or less.

2. The wavelength λ M The refractive index n of the thin film with respect to light M The mask blank according to claim 1, characterized in that the value is 0.96 or less.

3. The mask blank according to claim 1 or 2, characterized in that the thin film is a multilayer film comprising two or more layers.

4. The mask blank according to claim 1 or 2, characterized in that a protective film is provided between the multilayer reflective film and the thin film.

5. The thin film has the wavelength λ M The mask blank according to claim 1 or 2, characterized in that a phase difference of 130 to 230 degrees is generated between the reflected light from the thin film and the reflected light from the multilayer reflective film with respect to the light.

6. A reflective mask is provided on the main surface of a substrate in the order of a multilayer reflective film and a thin film on which a transfer pattern is formed. The thin film is made of a material containing at least one selected from chromium (Cr), vanadium (V), palladium (Pd), titanium (Ti), iridium (Ir), Rh (rhodium), tantalum (Ta), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tin (Sn), and platinum (Pt). The thickness of the thin film is 32.40 nm or more and 98 nm or less. The wavelength λ of the thin film L = The refractive index for light at 13.0 nm is n L , The wavelength λ of the thin film M = The refractive index for light at 13.5 nm is n M , The wavelength λ of the thin film H = The refractive index for light at 14.0 nm is n H , Coefficient P = [(1-n H ) / λ H - (1 - n) L ) / λ L ] / [(1-n M ) / λ M When ] A reflective mask characterized in that the absolute value of the coefficient P is 0.15 or less.

7. The wavelength λ M The refractive index n of the thin film with respect to light M The reflective mask according to claim 6, characterized in that the value is 0.96 or less.

8. The reflective mask according to claim 6 or 7, characterized in that the thin film is a multilayer film comprising two or more layers.

9. The reflective mask according to claim 6 or 7, characterized in that a protective film is provided between the multilayer reflective film and the thin film.

10. The thin film has the wavelength λ M A reflective mask according to claim 6 or 7, characterized in that it generates a phase difference of 130 to 230 degrees between the reflected light from the thin film and the reflected light from the multilayer reflective film with respect to light.

11. A method for manufacturing a semiconductor device, comprising the step of using the reflective mask described in claim 6 to expose and transfer the transfer pattern onto a resist film on a semiconductor substrate.

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