Substrate with multilayer reflection film, reflection type mask blank, reflection type mask, and method for manufacturing semiconductor device

Abstract

To provide a multilayer reflection film substrate, a reflection type mask blank and a reflection type mask which can improve the controllability of reflectance of a multilayer reflection film for EUV light having the wavelength 13.53 nm.SOLUTION: A substrate with multilayer reflection film comprises a substrate and a multilayer reflection film provided on a main surface of the substrate, where the multilayer reflection film has a lower part closer to the main surface of the substrate and an upper part farther from the main surface, and in a cross-sectional image of the multilayer reflection film captured by a dark-field scanning transmission electron microscope, the multilayer reflection film includes a first region where the skewness SkL of the brightness of the upper part is larger than the skewness SkL of the brightness of the lower part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer reflective film-coated substrate, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device. [Background technology]

[0002] 2. Description of the Related Art In recent years, with the increasing demand for higher density and higher precision in VLSI devices, EUV lithography, an exposure technology using extreme ultraviolet (hereinafter referred to as EUV) light, has been proposed.

[0003] A reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film to absorb the exposure light. The optical image reflected by the multilayer reflective film is transferred onto a semiconductor device substrate (transfer target) such as a silicon wafer through a reflective optical system.

[0004] As an example of a reflective mask, a reflective exposure mask used in EUV lithography is described in Cited Document 1. The reflective exposure mask described in Cited Document 1 has a mask pattern made of a nitrogen-containing metal film on a multilayer film formed on a reflective exposure mask substrate.

[0005] Cited Document 2 describes a multilayer reflector including a Mo / Si multilayer film having a structure in which layers mainly composed of Mo and layers mainly composed of Si are alternately and periodically formed on a substrate surface, and a diffusion prevention layer is formed on the Si-based layer. Cited Document 2 also describes that the diffusion prevention layer is composed of atoms having a covalence radius that is 80% or more of the radius of the largest sphere that can fit into the interatomic gaps in the Si-based layer. Cited Document 2 also describes that the formation of a diffusion layer made of a MoSi compound at the interface of the Mo / Si multilayer film leads to deterioration of optical properties such as a decrease in reflectance and a decrease in half-value width, and that the formation of the diffusion prevention layer can be suppressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-237174 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-140147 Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned EUV lithography is an exposure technology that uses extreme ultraviolet light (EUV light). EUV light is light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of approximately 0.2 to 100 nm. Generally, EUV lithography can use EUV light with a wavelength of 13 to 14 nm. A specific wavelength is exemplified as 13.5 nm. Therefore, it is said that the performance of the multilayer reflective film of a reflective mask needs to be such that the maximum reflectance at wavelengths of 13 to 14 nm, near the wavelength of 13.5 nm, is high.

[0008] FIG. 11 shows a schematic configuration of an EUV exposure tool 50, which is an apparatus for transferring a transfer pattern to a resist film formed on a semiconductor substrate 60. In the EUV exposure tool 50, when tin droplets emitted from a tin droplet generator 53 are irradiated with a high-power carbon dioxide laser from a laser light source 52, the tin droplets are converted into plasma, generating EUV light. The EUV light emitted by the tin droplets is generated by the 4d-4f transition of electrons excited from the 4d orbital of the ground state of tin to the 4f orbital, as they return from the excited state to the ground state. The emission wavelength at this time is 13.53 nm. To manufacture next-generation semiconductor devices with high yield and throughput, improved controllability of reflectance at a wavelength of 13.53 nm is required.

[0009] Therefore, an object of the present invention is to provide a multilayer reflective film substrate, a reflective mask blank, and a reflective mask that can improve the controllability of the reflectance of a multilayer reflective film for EUV light with a wavelength of 13.53 nm.

[0010] Another object of the present invention is to provide a method for manufacturing a semiconductor device using a reflective mask that can improve the controllability of the reflectance of a multilayer reflective film for EUV light with a wavelength of 13.53 nm. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention has the following configuration.

[0012] (Configuration 1) Configuration 1 includes a substrate, a multilayer reflective film provided on a main surface of the substrate, the multilayer reflective film has a lower portion closer to the major surface of the substrate and an upper portion farther from the major surface; The multilayer reflective film substrate is characterized in that, in a cross-sectional image of the multilayer reflective film taken with a dark-field scanning transmission electron microscope, the multilayer reflective film includes a first region in which the brightness distortion SkU of the upper portion is larger than the brightness distortion SkL of the lower portion.

[0013] (Configuration 2) Configuration 2 is the multilayer reflective film coated substrate of Configuration 1, wherein the first region is positioned so as to include at least a portion of the multilayer reflective film when viewed from above.

[0014] (Configuration 3) Configuration 3 is the multilayer reflective film-coated substrate of Configuration 1 or 2, characterized in that the first region is positioned so as to contain a square with sides of 132 mm, with the center of the main surface of the substrate as the intersection of diagonals, when viewed from above.

[0015] (Configuration 4) Configuration 4 is the substrate with a multilayer reflective film according to any one of Configurations 1 to 3, characterized in that the lower part corresponds to the lower half of the multilayer reflective film, which is 50% of the thickness of the multilayer reflective film on the substrate side, and the upper part corresponds to the upper half excluding the lower half.

[0016] (Configuration 5) Configuration 5 is the substrate with a multilayer reflective film according to any one of Configurations 1 to 4, wherein the multilayer reflective film has low refractive index layers and high refractive index layers alternately stacked, the low refractive index layers contain at least one selected from molybdenum and ruthenium, and the high refractive index layers contain silicon.

[0017] (Configuration 6) A sixth aspect of the present invention is a multilayer reflective film-coated substrate according to any one of the first to fifth aspects, an absorber film provided on the multilayer reflective film of the multilayer reflective film-coated substrate.

[0018] (Configuration 7) A seventh aspect of the present invention is a multilayer reflective film-coated substrate according to any one of the first to fifth aspects, an absorber pattern provided on the multilayer reflective film of the multilayer reflective film-coated substrate.

[0019] (Configuration 8) A twelfth aspect of the present invention is a reflective mask blank according to the sixth aspect, characterized in that the reflective mask blank has an absorber pattern formed by patterning the absorber film on the multilayer reflective film.

[0020] (Configuration 9) Configuration 9 is a method for manufacturing a semiconductor device, characterized by including using the reflective mask of configuration 7 or 8 to transfer the absorber pattern onto a transfer target formed on a substrate for a semiconductor device. [Effects of the Invention]

[0021] An object of the present invention is to provide a multilayer reflective film substrate, a reflective mask blank, and a reflective mask that can improve the controllability of the reflectance of a multilayer reflective film for EUV light with a wavelength of 13.53 nm.

[0022] Another object of the present invention is to provide a method for manufacturing a semiconductor device using a reflective mask that can improve the controllability of the reflectance of a multilayer reflective film for EUV light with a wavelength of 13.53 nm. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a multilayer reflective film-coated substrate according to the present embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating another example of a multilayer reflective film-coated substrate according to the present embodiment. [Figure 3] FIG. 1 is a cross-sectional view schematically illustrating an example of a reflective mask blank according to an embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view schematically illustrating another example of a reflective mask blank according to the present embodiment. [Figure 5] FIG. 10 is a cross-sectional view schematically illustrating yet another example of the reflective mask blank of the present embodiment. [Figure 6A-D] 5A to 5C are cross-sectional views illustrating an example of a method for manufacturing a reflective mask according to the present embodiment. [Figure 7] 3 is an enlarged schematic cross-sectional view of the multilayer reflective film and its vicinity in the example of the multilayer reflective film coated substrate of the present embodiment shown in FIG. 2. FIG. [Figure 8] FIG. 1 is a plan view schematically illustrating an example of a multilayer reflective film coated substrate of the present embodiment, viewed from above, showing an example of a first region. [Figure 9] FIG. 2 is a plan view schematically illustrating the top surface of an example of a multilayer reflective film coated substrate of the present embodiment, showing another example of a first region. [Figure 10] FIG. 2 is a plan view schematically illustrating the top surface of an example of a multilayer reflective film coated substrate of the present embodiment, showing yet another example of the first region. [Figure 11] FIG. 1 is a schematic diagram illustrating an example of an EUV exposure apparatus. [Figure 12] 1 is a schematic diagram showing an example of an optical system of a dark-field scanning transmission electron microscope (DF-STEM). [Figure 13] FIG. 1 is a diagram showing an example of a DF-STEM image of a multilayer reflective film. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are intended to specifically explain the present invention, and are not intended to limit the scope of the present invention.

[0025] FIG. 1 is a cross-sectional schematic diagram showing an example of a multilayer reflective film-coated substrate 90 of this embodiment. The multilayer reflective film-coated substrate 90 of this embodiment includes a substrate 1 and a multilayer reflective film 2 provided on the substrate 1. The multilayer reflective film 2 is provided on one main surface (also referred to as the "first main surface") of the substrate 1. The multilayer reflective film 2 includes a multilayer film in which predetermined low-refractive index layers and predetermined high-refractive index layers are alternately stacked. The multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 has a predetermined first region 20. The same applies to a reflective mask blank 100 described later. A back surface conductive film 5 for an electrostatic chuck may be formed on the back surface of the substrate 1. The back surface of the substrate 1 is the surface opposite to the side on which the multilayer reflective film 2 is formed, and is also referred to as the "second main surface."

[0026] Fig. 2 is a cross-sectional schematic view showing another example of a multilayer reflective film-coated substrate 90 of this embodiment. The multilayer reflective film-coated substrate 90 shown in Fig. 2 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a protective film 3 formed on the multilayer reflective film 2. Like the multilayer reflective film-coated substrate 90 shown in Fig. 1, the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of the embodiment shown in Fig. 2 also has a predetermined first region 20. A back surface conductive film 5 for an electrostatic chuck may be formed on the back surface (second main surface) of the substrate 1.

[0027] In this specification, "thin film B is disposed (formed) on thin film A (or substrate)" not only means that thin film B is disposed (formed) in contact with the surface of thin film A (or substrate), but also means that another thin film C is present between thin film A (or substrate) and thin film B. Furthermore, in this specification, for example, "thin film B is disposed in contact with the surface of thin film A (or substrate)" means that thin film A (or substrate) and thin film B are disposed so as to be in direct contact with each other, without any other thin film interposed between them. Furthermore, in this specification, "on" does not necessarily mean above in the vertical direction. "On" merely indicates the relative positional relationship between the thin film, the substrate, etc.

[0028] <Substrate with multilayer reflective film 90> The multilayer reflective film-coated substrate 90 of this embodiment will be specifically described. The multilayer reflective film-coated substrate 90 of this embodiment includes a substrate 1 and a multilayer reflective film 2 provided on a main surface of the substrate 1. The multilayer reflective film-coated substrate 90 of this embodiment may further include a protective film 3 and / or a back surface conductive film 5.

[0029] <<Board 1>> The substrate 1 is set to a thickness of 0±1.0×10 in order to prevent distortion of the transferred pattern due to heat during exposure to EUV light. -7 / °C, and preferably has a low thermal expansion coefficient within the range of 0±0.3×10 -7 It is more preferable that the thermal expansion coefficient is within the range of 0.05×10 / °C. -7 Materials having a low thermal expansion coefficient within the range of 0±5 ppb / °C are preferably used. Materials having a low thermal expansion coefficient within this range include, for example, SiO2-TiO2 glass and multi-component glass ceramics. As the material for substrate 1, a SiO2-TiO2 glass substrate in which TiO2 is added to SiO2 in the range of 3 to 12 wt % is preferred, and a SiO2-TiO2 glass substrate in which TiO2 is added in the range of approximately 5 to 10 wt % is more preferred. As substrate 1, for example, "ULE" glass (manufactured by Corning Incorporated) can be used.

[0030] The main surface (first main surface) of the substrate 1 on which a transfer pattern (the absorber pattern 4a described below) is formed is preferably processed to increase its flatness. Increasing the flatness of the main surface of the substrate 1 can improve the positional accuracy and transfer accuracy of the pattern. For example, in the case of EUV exposure, the flatness in a 132 mm × 132 mm area of ​​the main surface of the substrate 1 on which the transfer pattern 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 (rear surface) opposite the side on which the transfer pattern is formed is the surface fixed to the exposure apparatus by an electrostatic chuck. In a 142 mm × 142 mm area of ​​the rear surface, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is a value representing the warpage (deformation) of the surface indicated by TIR (Total Indicated Reading). The flatness (TIR) ​​is the absolute value of the difference in height between the highest point on the surface of substrate 1 above the focal plane, which is determined by the least squares method using the surface of substrate 1 as the reference plane, and the lowest point on the surface of substrate 1 below this focal plane.

[0031] In the case of EUV exposure, the surface roughness of the main surface of the substrate 1 on which the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured using an atomic force microscope.

[0032] The substrate 1 preferably has high rigidity to prevent deformation due to film stress of the thin film (such as the multilayer reflective film 2) formed thereon, and particularly preferably has a high Young's modulus of 65 GPa or more.

[0033] When a light irradiation treatment described below is performed after forming the multilayer reflective film 2, the substrate 1 preferably has high transmittance for light of a wavelength for performing the light irradiation treatment (for example, light with a wavelength of 300 nm to 800 nm). Specifically, when the thickness of the substrate 1 is 6.35 mm, the transmittance of the substrate 1 in the thickness direction for light with a wavelength of 300 nm to 800 nm is preferably 80% or more, and more preferably 85% or more.

[0034] Since the substrate 1 has high transmittance for light of a predetermined wavelength for the light irradiation treatment, the Ti of the substrate 1 3+ The concentration is preferably 5 ppm by weight or less, more preferably below the detection limit, as measured by electron spin resonance (ESR). 3+ The measurement limit of the concentration is generally 0.1 ppm by weight. 3+ The concentration can be measured at the center of the substrate 1 (the intersection of the diagonals of the rectangular substrate 1).

[0035] <<Multilayer reflective film 2>> The multilayer reflective film coated substrate 90 of this embodiment includes a multilayer reflective film 2. The multilayer reflective film 2 has a function of reflecting EUV light in the reflective mask 200. The multilayer reflective film 2 is a multilayer film in which low refractive index layers and high refractive index layers, each containing elements with different refractive indexes as main components, are alternately stacked.

[0036] Generally, the multilayer reflective film 2 is a multilayer film in which thin films (high refractive index layers) of light elements or their compounds, which are high refractive index materials, and thin films (low refractive index layers) of heavy elements or their compounds, which are low refractive index materials, are alternately stacked in approximately 30 to 60 cycles.

[0037] The multilayer film used as the multilayer reflective film 2 can have a structure in which a high-refractive index layer and a low-refractive index layer are stacked in this order from the substrate 1 side, with each cycle consisting of a high-refractive index layer / low-refractive index layer stacked in this order. The multilayer film can also have a structure in which a low-refractive index layer and a high-refractive index layer are stacked in this order from the substrate 1 side, with each cycle consisting of a low-refractive index layer / high-refractive index layer stacked in this order. The topmost layer of the multilayer reflective film 2, i.e., the surface layer of the multilayer reflective film 2 opposite the substrate 1 side, is preferably a high-refractive index layer. In the above-described multilayer film, when a high-refractive index layer and a low-refractive index layer are stacked in this order from the substrate 1 side, with each cycle consisting of a high-refractive index layer / low-refractive index layer stacked in this order from the substrate 1 side, the topmost layer is the low-refractive index layer. In this case, if the low-refractive index layer constitutes the topmost surface of the multilayer reflective film 2, it will be easily oxidized, potentially reducing the reflectivity of the reflective mask 200. Therefore, it is preferable to form the multilayer reflective film 2 by further forming a high-refractive index layer on the topmost low-refractive index layer. On the other hand, in the above-mentioned multilayer film, when a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 1 side, and a stack structure of low refractive index layer / high refractive index layer is defined as one cycle, the uppermost layer is the high refractive index layer, and in this case, there is no need to form an additional high refractive index layer.

[0038] The reflectance of the multilayer reflective film 2 used in this embodiment alone for light with a wavelength of 13.53 nm is, for example, 62% or more. The upper limit of the reflectance of the multilayer reflective film 2 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 2 can be selected so as to satisfy Bragg's law. In the case of a multilayer reflective film 2 for reflecting EUV light with a wavelength of 13.53 nm, the film thickness of one period (one pair of high-refractive-index layer and low-refractive-index layer) is preferably about 7 nm. The multilayer reflective film 2 has multiple high-refractive-index layers and multiple low-refractive-index layers, but the film thicknesses of the high-refractive-index layers and the low-refractive-index layers do not necessarily have to be the same.

[0039] The high-refractive index layer can be a layer containing silicon (Si). Examples of materials containing Si include elemental Si and Si compounds containing boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H). The use of a high-refractive index layer containing Si provides a reflective mask 200 with excellent EUV light reflectivity. The low-refractive index layer can be a metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof. These metals or alloys may also be doped with boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H). In a preferred example of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment, the low-refractive index layer is a molybdenum (Mo) layer and the high-refractive index layer is a silicon (Si) layer. For example, a Mo / Si periodic laminated film in which Mo layers and Si layers are alternately laminated for approximately 30 to 60 periods can be preferably used as the multilayer reflective film 2 for reflecting EUV light with a wavelength of 13 to 14 nm (e.g., 13.53 nm). A preferred example of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment is one in which the low refractive index layers are ruthenium (Ru) layers and the high refractive index layers are silicon (Si) layers. For example, a Ru / Si periodic laminated film in which Ru layers and Si layers are alternately laminated for approximately 30 to 40 periods can be preferably used as the multilayer reflective film 2 for reflecting EUV light with a wavelength of 13 to 14 nm (e.g., 13.53 nm).

[0040] In the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment, the low-refractive index layer preferably contains at least one selected from molybdenum (Mo) and ruthenium (Ru), and the high-refractive index layer preferably contains silicon (Si). Molybdenum (Mo) and ruthenium (Ru) have appropriate refractive indices for low-refractive index layers with respect to EUV light, and a multilayer film in combination with a high-refractive index layer containing Si, a high-refractive index material, can increase the reflectivity with respect to EUV light. Mo / Si multilayer reflective films have traditionally been used as multilayer reflective films 2 for reflective masks and are highly reliable. Ru / Si multilayer reflective films can provide a shallower effective reflective surface than Mo / Si multilayer reflective films, which is advantageous in suppressing the 3D effect.

[0041] In the multilayer reflective film coated substrate 90 of this embodiment, when the low refractive index layer of the multilayer reflective film 2 contains molybdenum (Mo) and ruthenium (Ru), the low refractive index layer may further contain an additive element other than Mo and Ru. Examples of the additive element contained in the low refractive index layer include at least one selected from thallium (Tl), hafnium (Hf), titanium (Ti), zirconium (Zr), manganese (Mn), indium (In), gallium (Ga), cadmium (Cd), bismuth (Bi), tantalum (Ta), lead (Pb), silver (Ag), aluminum (Al), vanadium (V), niobium (Nb), tin (Sn), zinc (Zn), mercury (Hg), chromium (Cr), iron (Fe), antimony (Sb), tungsten (W), and copper (Cu). By including these additive elements, the phenomenon of Si atoms diffusing from the high-refractive-index layer containing Si to the low-refractive-index layer can be suppressed, and the adhesion between the low-refractive-index layer and the high-refractive-index layer can be improved.

[0042] In the multilayer reflective film-coated substrate 90 of this embodiment, the multilayer reflective film 2 can further include an intermediate layer between the low-refractive-index layer and the high-refractive-index layer. For example, when the low-refractive-index layer is a Ru film and the high-refractive-index layer is a Si film, an intermediate layer can be disposed between the Ru film and the Si film. The intermediate layer can include at least one selected from SiN, SiO, SiC, SiON, SiCN, SiOC, SiOCN, and BC. A SiN film can be preferably used as the intermediate layer. By disposing a SiN film intermediate layer between the Ru film and the Si film, atomic diffusion between the Ru film, which is the low-refractive-index layer, and the Si film, which is the high-refractive-index layer, can be suppressed.

[0043] 7 is an enlarged schematic cross-sectional view of an example of a multilayer reflective film-coated substrate 90 of this embodiment, showing the vicinity of the multilayer reflective film 2. As shown in Fig. 7, the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment has a lower portion 2a closer to the main surface of the substrate 1 and an upper portion 2b farther from the main surface.

[0044] The lower portion 2a of the multilayer reflective film 2 is part of the depth region of the multilayer reflective film 2 and is closer to the main surface of the substrate 1 than the upper portion 2b. The upper portion 2b of the multilayer reflective film 2 is part of the depth region of the multilayer reflective film 2 and is farther from the main surface of the substrate 1 than the lower portion 2a. The multilayer reflective film 2 may have other depth regions in addition to the lower portion 2a and the upper portion 2b. The film thicknesses of the lower portion 2a and the upper portion 2b are not particularly limited, but may be, for example, 10 nm or more, preferably 20 nm or more.

[0045] In the multilayer reflective film-coated substrate 90 of this embodiment, the lower portion 2a preferably corresponds to the lower half of the multilayer reflective film 2, which is 50% of the thickness of the multilayer reflective film 2 on the substrate 1 side, and the upper portion 2b preferably corresponds to the upper half excluding the lower half. In this specification, the "lower half" of a predetermined thin film refers to a region of the predetermined thin film that is half the thickness of the predetermined thin film on the substrate 1 side in the thickness direction. The lower half can also be considered to be a region that is closer to the substrate 1 in the thickness direction of the predetermined thin film and has half the thickness of the predetermined thin film. Also, in this specification, the "upper half" of a predetermined thin film refers to a region of the predetermined thin film that is half the thickness of the predetermined thin film on the opposite side of the substrate 1 in the thickness direction. The upper half can also be considered to be a region that is farther from the substrate 1 in the thickness direction of the predetermined thin film and has half the thickness of the predetermined thin film. The lower portion 2a and upper portion 2b correspond to the lower half (50% of the thickness on the substrate 1 side) and the upper half (50% of the thickness on the opposite side of the substrate 1), respectively, allowing for appropriate measurement of the luminance distortion SkU, which will be described later.

[0046] In the multilayer reflective film-coated substrate 90 of this embodiment, in a cross-sectional image (DF-STEM image) of the multilayer reflective film 2 taken with a dark-field scanning transmission electron microscope (DF-STEM), the multilayer reflective film 2 includes a first region 20 in which the skewness of brightness SkU of the upper portion 2b is larger than the skewness of brightness SkL of the lower portion 2a. By including the predetermined first region 20 in the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment, it is possible to improve the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm. FIG. 13 shows an example of a cross-sectional image (DF-STEM image) of the multilayer reflective film 2 taken with a dark-field scanning transmission electron microscope. The measurement method of the DF-STEM image and the skewness will be described later.

[0047] In this specification, the "controllability of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm" refers to a small absolute value of the first derivative (slope) of R(λ), d / dλ·R(λ) (λ=13.53 nm), of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm, as shown in a graph with wavelength on the horizontal axis and reflectance on the vertical axis, where λ is the wavelength of EUV light and R(λ) is the reflectance. Variations in the reflectance spectrum may occur due to variations in the composition of the multilayer reflective coating 2 and / or variations in the film thickness of each layer of the multilayer reflective coating 2. In such cases, the shape of the reflectance spectrum may generally be maintained, but the wavelength dependence of the reflectance spectrum may vary. In such a case, if the absolute value of the first derivative (slope) d / dλ·R(λ) (λ=13.53 nm) of the wavelength dependency of reflectance R(λ) at the wavelength of 13.53 nm of EUV light is large, a large fluctuation will occur in the reflectance of the multilayer reflective coating 2. Because the absolute value of the first derivative (slope) of R(λ) at the wavelength of 13.53 nm is small, even if a change occurs in the reflection spectrum of the multilayer reflective coating 2, it is possible to reduce the change in reflectance for EUV light with a wavelength of 13.53 nm.

[0048] In the multilayer reflective film-coated substrate 90 of this embodiment, the multilayer reflective film 2 includes a first region 20 in which the skewness of brightness SkU in the upper portion 2b is larger than the skewness of brightness SkL in the lower portion 2a. This reduces the absolute value of the first derivative (slope) d / dλ·R(λ) (λ=13.53 nm) of the reflectance R(λ) of the multilayer reflective film 2. The reason for this is presumed to be as follows, but this embodiment is not bound by this presumption. That is, the skewness of brightness SkL in the lower portion 2a of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment is smaller than the skewness of brightness SkU in the upper portion 2b. This means that the brightness of the lower portion 2a in a DF-STEM image obtained by measurement with a scanning transmission electron microscope is higher than that of the upper portion 2b. The signal obtained in the DF-STEM image is a signal due to diffracted electrons diffracted by a highly crystalline region, and the stronger this signal, the greater the brightness. That is, the brightness of a DF-STEM image is higher in a highly crystalline region. On the other hand, in amorphous regions with low crystallinity, the diffraction of the incident electron beam is small or nonexistent. Therefore, in regions with low crystallinity, the brightness of the DF-STEM image is low. When one of the high-refractive index layer and the low-refractive index layer of the multilayer reflective coating 2 has high crystallinity and the other has low crystallinity, the layer with high crystallinity will have higher brightness in the DF-STEM image. If the material of the high-crystallinity layer diffuses into the low-crystallinity layer, the region of the high-crystallinity layer will appear to expand. Therefore, in regions where the material of the high-crystallinity layer diffuses into the low-crystallinity layer, the signal (brightness) of the DF-STEM image will be higher. Furthermore, in regions where the material of the high-crystallinity layer diffuses into the low-crystallinity layer, the peak shape of the reflection spectrum (the relationship between the wavelength of incident light and the intensity of reflected light) in the diffused region becomes broader than before diffusion. As a result, the absolute value of the first derivative (slope) d / dλ·R(λ) (λ = 13.53 nm) of the reflectance R(λ) of the multilayer reflective coating 2 can be reduced. Therefore, in the lower portion 2a of the multilayer reflective film 2, the material of the highly crystalline layer diffuses into the less crystalline layer, thereby reducing the absolute value of the first derivative (slope) d / dλ·R(λ) (λ=13.53 nm) of the reflectivity R(λ) of the multilayer reflective film 2 as a whole.Therefore, by including a region in the multilayer reflective coating 2 where the signal (brightness) of the DF-STEM image is high, the controllability of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm can be improved. The absolute value of the first derivative (slope) d / dλ·R(λ) (λ=13.53 nm) of the reflectance R(λ) of the multilayer reflective coating 2 is preferably 20% / nm or less, and more preferably 19.5% / nm or less. This makes it possible to better control the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm.

[0049] The upper portion 2b of the multilayer reflective coating 2 is a region that contributes significantly to the reflection of EUV light compared to the lower portion 2a. Therefore, the upper portion 2b of the multilayer reflective coating 2 must have a high reflectivity for EUV light. Meanwhile, the reflectivity of EUV light decreases when materials from highly crystalline layers diffuse into layers with low crystallinity. Therefore, it is preferable to prevent materials from highly crystalline layers from diffusing into layers with low crystallinity in the upper portion 2b of the multilayer reflective coating 2. That is, the signal (brightness) of the DF-STEM image of the upper portion 2b of the multilayer reflective coating 2 is preferably lower than that of the lower portion 2a. A lower signal (brightness) of the DF-STEM image of the upper portion 2b corresponds to a larger brightness skewness SkU of the DF-STEM image of the upper portion 2b. Therefore, by including the first region 20 in which the brightness skewness SkU of the upper portion 2b is larger than the brightness skewness SkL of the lower portion 2a, the multilayer reflective coating 2 can suppress a decrease in the reflectivity of the multilayer reflective coating 2 while minimizing the change in reflectivity for EUV light with a wavelength of 13.53 nm. Therefore, since the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment includes a first region 20 including a predetermined lower portion 2a and upper portion 2b, it is possible to maintain a high reflectivity of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm while improving the controllability of the reflectivity of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm.

[0050] Generally, silicon (Si) thin films formed by sputtering methods such as ion beam sputtering and magnetron sputtering are amorphous. Furthermore, metal thin films formed by sputtering are generally crystalline. Therefore, for example, if the low-refractive index layer of the multilayer reflective film 2 is made of molybdenum (Mo) or ruthenium (Ru) and the high-refractive index layer is made of silicon (Si), the highly crystalline material of the low-refractive index layer (molybdenum (Mo) or ruthenium (Ru)) can be diffused into the low-refractive index layer made of silicon (Si), which has low crystallinity. Therefore, in the lower portion 2a of the multilayer reflective film 2, the material of the highly crystalline high-refractive index layer can be diffused into the low-refractive index layer, which has low crystallinity, to form a predetermined first region 20 in the multilayer reflective film 2. As a result, the controllability of the reflectivity of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm can be improved.

[0051] The brightness of a DF-STEM image obtained by measuring the multilayer reflective coating 2 using a scanning transmission electron microscope can be expressed as an average gray value (middle gray value). The average gray value refers to a numerical value calculated by dividing the sum of the gray values ​​of all pixels in an arbitrary analysis region of the DF-STEM image by the number of pixels. In this case, the brightness of the DF-STEM image can be quantified as an average gray value on a gray scale ranging from 0 to 255. Here, a higher average gray value indicates a color closer to white, and a lower average gray value indicates a color closer to black. High brightness corresponds to a high average gray value, and low brightness corresponds to a low average gray value. Therefore, in the multilayer reflective coating 2 of the multilayer reflective coating-coated substrate 90 of this embodiment, in a cross-sectional image of the multilayer reflective coating 2 captured using a dark-field scanning transmission electron microscope, the multilayer reflective coating 2 can be said to include a first region 20 in which the average gray value of brightness of the upper portion 2b is smaller than the average gray value of brightness of the lower portion 2a. The multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment includes the predetermined first region 20, thereby improving the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm. For example, when the lower portion 2a corresponds to the lower half and the upper portion 2b corresponds to the upper half, the absolute value of the difference between the average gray value of the lower portion 2a and the average gray value of the upper portion 2b is preferably 5.0 or more, and more preferably 6.0 or more.

[0052] The first region 20 of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment can be located so as to include at least a portion of the multilayer reflective film 2 when viewed from above. The top view of the multilayer reflective film 2 refers to the plane of the multilayer reflective film 2 when viewed from the side of the first main surface on which the multilayer reflective film 2 is formed. The first region 20 can be located at any position and have any size. By having the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 have a predetermined first region 20, it is possible to improve the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm.

[0053] Fig. 8 is a schematic plan view of an example of a multilayer reflective film-coated substrate 90 of this embodiment, viewed from above. As shown in Fig. 8, the first region 20, which is a region where the luminance distortion factor SkU of the upper portion 2b is larger than the luminance distortion factor SkL of the lower portion 2a, can be a region of any size and at any position when the multilayer reflective film 2 is viewed from above.

[0054] 9 is a plan view schematically illustrating the top view of an example of a multilayer reflective film-coated substrate 90 of this embodiment, showing another example of the first region 20. As shown in Fig. 9, the first region 20, which is a region where the luminance distortion factor SkU of the upper portion 2b is larger than the luminance distortion factor SkL of the lower portion 2a, can be a region including the intersection point of diagonals of the main surface of the substrate 1 (the center of the substrate 1) when the multilayer reflective film 2 is viewed from above.

[0055] The first region 20 of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment is positioned so as to include at least a portion of the multilayer reflective film 2 when viewed from above, thereby improving the controllability of the reflectivity of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm in at least a portion of the multilayer reflective film 2.

[0056] FIG. 10 is a schematic plan view of an example of a multilayer reflective film-coated substrate 90 of this embodiment, viewed from above, showing yet another example of the first region 20. As shown in FIG. 10 , the first region 20 of the multilayer reflective film-coated substrate 90 of this embodiment is preferably positioned to include a square with a diagonal intersection at the center of the main surface of the substrate 1 and a length of 132 mm when viewed from above. The first region 20, in which the luminance distortion SkU of the upper portion 2b is larger than the luminance distortion SkL of the lower portion 2a, is positioned to include a square with a diagonal intersection at the center of the main surface of the substrate 1 and a length of 132 mm when viewed from above. This allows the first region 20 to be formed over the entire transfer pattern formation region. This improves the controllability of the reflectivity of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm over the entire transfer pattern formation region of the multilayer reflective film 2.

[0057] Next, we will explain a method for determining whether or not the predetermined first region 20 is present in the multilayer reflective film 2. The presence or absence of the predetermined first region 20 in the multilayer reflective film 2 can be determined by evaluating the brightness skewness (Ssk) of a DF-STEM image.

[0058] In this specification, the brightness skewness (Ssk) of a DF-STEM image refers to a value obtained by obtaining a DF-STEM image of a sample through measurement using a scanning transmission electron microscope (STEM) using the dark-field (DF) method, and analyzing the brightness histogram when the grayscale shading of the DF-STEM image is expressed in 256 tones. In this specification, the term "DF-STEM image" refers to a dark-field scanning transmission electron microscope (DF) image obtained by observation using a scanning transmission electron microscope (STEM) using the dark-field (DF) method. The brightness skewness of a DF-STEM image of a multilayer reflective film 2 can be obtained by analyzing the brightness histogram when the grayscale shading obtained through image analysis of the DF-STEM image of the multilayer reflective film 2 is expressed in 256 tones. The brightness skewness of a DF-STEM image of a multilayer reflective film 2 will be further explained below.

[0059] FIG. 12 shows a schematic diagram of the optical system 300 of a dark-field scanning transmission electron microscope (DF-STEM). To measure the brightness distortion of a DF-STEM image of the multilayer reflective film 2, the multilayer reflective film 2 is first measured using the DF-STEM, and a DF-STEM image of a predetermined position on the multilayer reflective film 2 (sample 304) is obtained. To obtain the DF-STEM image, an ARM200F scanning transmission electron microscope (manufactured by JEOL Ltd.) is used, and the accelerating voltage of the incident electrons 302 is set to 200 kV. FIG. 12 illustrates how an electron beam (incident electrons 302) with a solid angle α of 18 to 22 mrad converges and strikes the sample 304. A circular detector can also be used to perform measurements using the dark-field method. A DF-STEM image can be obtained by using a dark-field optical system to detect electrons diffracted and inelastically scattered electrons 306 in the range from β1 to β2 (e.g., β1 = 68 mrad and β2 = 280 mrad) shown in FIG. 12 in four regions of annular detector 310, and forming an image using a signal detected in one of the four regions. The four regions are region 310a on the right side of annular detector 310, region 310b on the bottom side, region 310c on the left side, and region 310d on the top side. If we compare it to a clock, the four regions are region 310a at the 3 o'clock position, region 310b at the 6 o'clock position, region 310c at the 9 o'clock position, and region 310d at the 12 o'clock position. To obtain a formed DF-STEM image, the measurement signal from at least one of the four regions of annular detector 310 can be used. In the examples described below, measurement signals from the downward region 310b or the upward region 310d were used to obtain a DF-STEM image. It is also possible to use measurement signals from the rightward region 310a or the leftward region 310c to obtain a DF-STEM image.

[0060] DF-STEM measurements can be performed by irradiating incident electrons 302 onto a cross section at a predetermined position of a multilayer reflective film 2 stacked with a predetermined number of periods, for example, 30 to 60 periods. Therefore, a sample 304 cut out to a thickness of 50 nm to 100 nm can be used so that the cross section of the multilayer reflective film 2 stacked with a predetermined number of periods can be seen. Therefore, a DF-STEM image can be obtained that shows the cross section of the multilayer reflective film 2. Figure 13 shows an example of a DF-STEM image obtained in this way.

[0061] Next, the obtained DF-STEM image is subjected to image analysis. The regions subjected to image analysis are the lower portion 2a and the upper portion 2b of the multilayer reflective film 2. The lower portion 2a of the multilayer reflective film 2 preferably corresponds to the lower half, which is 50% of the thickness of the multilayer reflective film 2 on the substrate 1 side, and the upper portion 2b preferably corresponds to the upper half excluding the lower half. The widthwise length of the lower portion 2a and the upper portion 2b of the multilayer reflective film 2 is preferably 900 nm, for example. For example, in the case of a multilayer reflective film 2 in which the thickness of one period is 7 nm and 40 periods are stacked, the thickness of the multilayer reflective film 2 is 280 nm. In this case, the lower portion 2a used for image analysis of the DF-STEM image can be a 140 nm thick and 900 nm wide region on the substrate 1 side of the cross section of the multilayer reflective film 2. Furthermore, the upper portion 2b used for image analysis of the DF-STEM image in this case can be a 900 nm wide region excluding the lower portion 2a (the 140 nm thick and 900 nm wide region of the upper half). In the DF-STEM image, the regions of the lower part 2a and the upper part 2b where image analysis is performed are referred to as "image analysis regions."

[0062] In image analysis of a DF-STEM image, each pixel in the image analysis region of the DF-STEM image is quantified as a grayscale ranging from 0 to 255. In Figure 13, higher grayscale values ​​represent colors closer to white, while lower grayscale values ​​represent colors closer to black. The number of pixels in the image analysis region of the DF-STEM image is 1024 x 1024. The gray values ​​of a given grayscale level in the image analysis region can be expressed as a histogram graph (distribution of grayscale levels and gray values) by plotting the grayscale level on the horizontal axis.

[0063] In this embodiment, the brightness skewness of a DF-STEM image is a value obtained by acquiring a DF-STEM image of the multilayer reflective film 2, performing image analysis, and statistically analyzing a histogram of gray values ​​from 0 to 255 on the gray scale obtained. Methods for calculating skewness from a histogram are well known.

[0064] In this way, it is possible to determine the skewness of brightness in a DF-STEM image of a given multilayer reflective film 2. By determining the skewness of brightness in a DF-STEM image using the lower part 2a and the upper part 2b of the multilayer reflective film 2 as image analysis regions, it is possible to determine the skewness of brightness in the lower part 2a (referred to as "skewness SkL") and the skewness of brightness in the upper part 2b (referred to as "skewness SkU").

[0065] When determining the skewness of brightness, it is preferable to statistically determine the skewness using only data from 150 to 255 grayscale levels, which are the high-brightness regions of the DF-STEM image. The inventors have found that using only data from 150 to 255 grayscale levels when determining the skewness shows a stronger correlation with the brightness of the DF-STEM image of the multilayer reflective coating 2. Therefore, by using only data from 150 to 255 grayscale levels, the skewness can be considered to be a value indicating the brightness of the DF-STEM image.

[0066] The skewness SkL of the brightness of the lower portion 2a of the multilayer reflective coating 2 obtained using only data from DF-STEM images of 150 to 255 gradations is preferably 0.36 or less, and more preferably 0.28 or less. When the skewness SkL of the brightness of the lower portion 2a is within a predetermined range, it is possible to more reliably improve the controllability of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm.

[0067] The skewness SkU of the brightness of the upper portion 2b of the multilayer reflective coating 2, obtained using only data from 150 to 255 gray levels of the DF-STEM image, is preferably 0.24 or greater, more preferably 0.32 or greater. By keeping the skewness SkU of the brightness of the upper portion 2b within a predetermined range, the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm can be more reliably maintained at a high level. Furthermore, for example, when the upper portion 2b and the lower portion 2a correspond to the upper half and lower half, respectively, the absolute value of the difference between the skewness SkU of the brightness of the upper portion 2b and the skewness SkL of the brightness of the lower portion 2a is preferably greater than 0.01, more preferably 0.02 or greater. This improves the controllability of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm.

[0068] Methods for forming the multilayer reflective film 2 are well known in the art. In the multilayer reflective film-coated substrate 90 of this embodiment, the multilayer reflective film 2 can be formed by depositing each layer by, for example, ion beam sputtering or magnetron sputtering. In the case of the Mo / Si periodic stacked film described above, for example, an Si film having a thickness of about 4 nm is first deposited on the substrate 1 using a Si target by ion beam sputtering or magnetron sputtering, and then an Mo film having a thickness of about 3 nm is deposited using a Mo target. This constitutes one cycle, and 30 to 60 cycles are stacked to form the multilayer reflective film 2 (the outermost layer is a Si film). The thickness of one cycle is preferably 7 nm. Although 60 cycles requires more steps than 30 cycles, the reflectivity for EUV light can be increased.

[0069] When the multilayer reflective coating 2 is formed by ion beam sputtering or magnetron sputtering, the brightness (brightness distortion) of the DF-STEM image of the multilayer reflective coating 2 can be controlled by changing the deposition conditions, such as the discharge conditions, deposition pressure, the type of deposition gas (such as a rare gas), the distance between the mask shield and the substrate 1, and / or the angle between the substrate 1 and the target. Therefore, by changing the deposition conditions described above between the lower portion 2a and the upper portion 2b of the multilayer reflective coating 2, the brightness (brightness distortion SkL and distortion SkU) of the DF-STEM images of the lower portion 2a and the upper portion 2b can be controlled.

[0070] Furthermore, the brightness (brightness distortion) of the DF-STEM image of the multilayer reflective film 2 can be controlled by depositing the multilayer reflective film 2 by ion beam sputtering or magnetron sputtering under the same conditions for the upper and lower portions 2b and 2a, and then annealing the multilayer reflective film 2 after deposition. It is preferable to anneal only the lower portion 2a of the multilayer reflective film 2 by irradiating the multilayer reflective film 2 with light from the second main surface of the substrate 1 through the substrate 1. By annealing only the lower portion 2a of the multilayer reflective film 2 in this manner, it is possible to form a first region 20 in which the brightness distortion SkU of the upper portion 2b of the multilayer reflective film 2 is greater than the brightness distortion SkL of the lower portion 2a, even though the entire multilayer reflective film 2 is deposited under the same conditions. Note that in this specification, annealing the multilayer reflective film 2 with light may be referred to as a "light irradiation treatment."

[0071] Next, the light irradiation process will be described. Generally, the optical properties of the multilayer reflective film 2 can be made uniform by performing the light irradiation process.

[0072] In the light irradiation treatment, it is preferable to perform a treatment in which the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 is irradiated with light (high energy rays) emitted from a flash lamp.

[0073] A flash lamp is a light source that can emit light over a wide, continuous wavelength range. For example, a flash lamp can be a lamp that emits light by applying a pulsed high voltage to a tube made of a light-transmitting material such as glass that contains a gas such as xenon.

[0074] The wavelength of the light emitted from the flash lamp preferably includes the range of 300 nm to 800 nm, and more preferably includes the range of 250 nm to 800 nm.

[0075] The irradiation intensity of the flash lamp varies depending on the type and composition of the material of the multilayer reflective film 2, but is generally in the range of 0.1 to 100 J / cm 2 , preferably 1 to 50 J / cm 2 , more preferably 10 to 50 J / cm 2 By keeping the irradiation intensity within this range, it is possible to prevent the film from scattering and the surface from becoming rough. Furthermore, by keeping the irradiation intensity within this range, it is possible to obtain a sufficient effect of adjusting the luminance distortion SkL of the lower portion 2a.

[0076] The light irradiation process can be performed by irradiating the entire surface of the multilayer reflective film 2 with light of the same intensity. Alternatively, the light irradiation process can be performed, if necessary, by irradiating the multilayer reflective film 2 with light having an intensity distribution so that the light intensity varies depending on the position. By irradiating the multilayer reflective film 2 with light having an intensity distribution, the maximum reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm can be controlled, and the in-plane uniformity of the film quality (maximum reflectance, BGL, etc.) of the multilayer reflective film 2 can be improved. BGL refers to the background level during defect inspection.

[0077] The irradiation time of the light from the flash lamp is 1 second or less, preferably 0.1 seconds or less, and more preferably 0.05 seconds or less. By shortening the irradiation time of the light emitted from the flash lamp, the film stress can be reduced without excessively heating the glass substrate 1. This makes it possible to prevent damage to the glass substrate 1.

[0078] For the light irradiation treatment, a xenon lamp was used as the lamp, and 15 J / cm 2 It is preferable to irradiate the target object once with light having an irradiation intensity of 1 to 20 milliseconds and a pulse width of 1 to 20 milliseconds.

[0079] In the present invention, when the multilayer reflective film 2 formed on the main surface of the glass substrate 1 is irradiated with light emitted from a flash lamp, the irradiation may be completed in one go, or may be divided into multiple rounds. Furthermore, when the film has a multilayer structure, irradiation may be performed each time a film is formed, or multiple films may be formed and then irradiated all at once. Furthermore, it is preferable that the light from the flash lamp is irradiated onto the multilayer reflective film 2 from the substrate 1 side. Furthermore, the ambient atmosphere around the location where the glass substrate 1 is placed when irradiated with light from the flash lamp may be any atmosphere, such as an inert gas such as argon, nitrogen, oxygen, or a mixed gas of two or more of these, a vacuum, or the atmosphere.

[0080] When the light irradiation treatment is performed by irradiating the multilayer reflective film 2 with light from the substrate 1 side, it must be performed before forming a back surface conductive film 5 (described later) on the second main surface of the substrate 1. The light irradiation treatment may be performed at any time after forming the multilayer reflective film 2 and before forming the back surface conductive film 5.

[0081] By including the multilayer reflective film-coated substrate 90 of the embodiment, which includes the above-mentioned specified multilayer reflective film 2, it is possible to improve the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm while maintaining a high reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm.

[0082] <<Protective film 3>> As shown in FIG. 2, the multilayer reflective film coated substrate 90 of this embodiment preferably has a protective film 3 provided on the multilayer reflective film 2.

[0083] In order to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200, which will be described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with the surface of the multilayer reflective film 2. The protective film 3 also has the function of protecting the multilayer reflective film 2 when repairing opacity defects in the transfer pattern (absorber pattern 4a) using an electron beam (EB). 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. As a result, the reflectivity characteristics of the multilayer reflective film 2 for EUV light are improved.

[0084] 2 shows the case where the protective film 3 is a single layer. However, the protective film 3 may have a laminated structure of two layers. The protective film 3 is formed, for example, from a material containing ruthenium as a main component. Examples of materials containing ruthenium as a main component include simple Ru metal, Ru alloys containing Ru and at least one metal selected from titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials containing nitrogen in any of these.

[0085] The Ru content of the Ru alloy used for the protective film 3 is 50 atomic % or more and less than 100 atomic %, preferably 80 atomic % or more and less than 100 atomic %, and more preferably 95 atomic % or more and less than 100 atomic %. In this case, the protective film 3 can have sufficient reflectance for EUV light, while also being resistant to mask cleaning, functioning as an etching stopper when the absorber film 4 is etched, and functioning to prevent deterioration of the multilayer reflective film 2 over time.

[0086] The thickness of the protective film 3 is not particularly limited as long as it can function as the protective film 3. From the viewpoint of reflectance to EUV light, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm.

[0087] Any known film formation method can be used without any particular limitation as the method for forming the protective film 3. Specific examples of the method for forming the protective film 3 include ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition.

[0088] <Reflective mask blank 100> This embodiment is a reflective mask blank 100 having a substrate 1, a multilayer reflective film 2 that is provided on the substrate 1 and reflects EUV light, and an absorber film 4 on the multilayer reflective film 2. The multilayer reflective film 2 of the reflective mask blank 100 includes the above-mentioned first region 20, similar to the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 shown in FIG.

[0089] <<Absorber membrane 4>> The reflective mask blank 100 of this embodiment includes an absorber film 4 on the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 described above, or on the protective film 3 formed on the multilayer reflective film 2. The multilayer reflective film 2 included in the reflective mask blank 100 has similar features to the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 described above, such as including a first region 20 in which the luminance distortion SkU of the upper portion 2b is larger than the luminance distortion SkL of the lower portion 2a in a cross-sectional image of the multilayer reflective film 2 captured with a dark-field scanning transmission electron microscope.

[0090] Fig. 3 is a cross-sectional schematic diagram showing an example of a reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Fig. 3 has an absorber film 4 for absorbing EUV light on the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 shown in Fig. 1. The reflective mask blank 100 may further have another thin film, such as a resist film 11, on the absorber film 4.

[0091] Fig. 4 is a cross-sectional schematic diagram showing an example of a reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Fig. 4 has an absorber film 4 for absorbing EUV light on the protective film 3 of the multilayer reflective film-coated substrate 90 shown in Fig. 2. The reflective mask blank 100 may further have another thin film, such as a resist film 11, on the absorber film 4.

[0092] Fig. 5 is a cross-sectional schematic diagram showing another example of a reflective mask blank 100 of this embodiment. As shown in Fig. 5, the reflective mask blank 100 can have an etching mask film 6 on an absorber film 4. The reflective mask blank 100 can further have another thin film, such as a resist film 11, on the etching mask film 6.

[0093] In the reflective mask blank 100 of this embodiment, the absorber film 4 can absorb EUV light, and therefore, by patterning the absorber film 4 of the reflective mask blank 100, the reflective mask 200 (EUV mask) of the present invention can be manufactured.

[0094] The basic function of the absorber film 4 is to absorb EUV light. The absorber film 4 may be an absorber film 4 intended for absorbing EUV light, or an absorber film 4 having a phase shift function that also takes into account the phase difference of EUV light. The absorber film 4 having a phase shift function not only absorbs EUV light but also reflects a portion of the EUV light to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 4 having a phase shift function, the absorber film 4 absorbs and attenuates EUV light in the region where the absorber film 4 is formed, while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Furthermore, in regions (field regions) where the absorber film 4 is not formed, the EUV light is reflected by the multilayer reflective film 2 (via the protective film 3, if present). Therefore, a desired phase difference is generated between the light reflected from the absorber film 4 having a phase shift function and the light reflected from the field region. The absorber film 4 having a phase shift function is preferably formed so that the phase difference between the reflected light from the absorber film 4 and the reflected light from the multilayer reflective film 2 is 170 to 260 degrees. The lights with the inverted phase difference interfere with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast increases the resolution and can increase various exposure latitudes, such as exposure dose latitude and focus latitude.

[0095] The absorber film 4 may be a single-layer film or a multilayer film consisting of multiple films (e.g., a lower-layer absorber film and an upper-layer absorber film). In the case of a single-layer film, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constants and film thickness of the upper-layer absorber film can be appropriately set so that it serves as an anti-reflection film during optical mask pattern defect inspection. This improves the inspection sensitivity during optical mask pattern defect inspection. Furthermore, using a film containing oxygen (O) or nitrogen (N), which improves oxidation resistance, as the upper-layer absorber film improves stability over time. Thus, by using a multilayer absorber film 4, various functions can be added to the absorber film 4. When the absorber film 4 has a phase shift function, using a multilayer film can widen the range of optical adjustment, making it easier to obtain a desired reflectance.

[0096] The material of the absorber film 4 is not particularly limited as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity relative to the protective film 3. As a material having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), an alloy containing two or more metals, or a compound thereof can be preferably used. The compound may contain oxygen (O), nitrogen (N), carbon (C) and / or boron (B) in the above metal or alloy.

[0097] The absorber film 4 can be formed by magnetron sputtering such as DC sputtering or RF sputtering. For example, the absorber film 4 made of a tantalum compound or the like can be formed by reactive sputtering using a target containing tantalum and boron and argon gas to which oxygen or nitrogen is added.

[0098] Furthermore, from the viewpoint of smoothness and flatness, the crystalline state of the absorber film 4 is preferably an amorphous or microcrystalline structure. When the surface of the absorber film 4 is smooth and / or flat, the edge roughness of the absorber pattern 4a is reduced, and the dimensional accuracy of the pattern is improved. The surface roughness of the absorber film 4 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in terms of root mean square roughness (Rms).

[0099] <<Etching mask film 6>> 5, the reflective mask blank 100 of this embodiment can have an etching mask film 6 on an absorber film 4. As a material for the etching mask film 6, it is preferable to use a material that has a high etching selectivity of the absorber film 4 to the etching mask film 6 (etching rate of the absorber film 4 / etching rate of the etching mask film 6). The etching selectivity of the absorber film 4 to the etching mask film 6 is preferably 1.5 or more, and more preferably 3 or more.

[0100] The reflective mask blank 100 of this embodiment preferably has an etching mask film 6 on the absorber film 4 .

[0101] Chromium or a chromium compound is preferably used as the material for the etching mask film 6. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. The etching mask film 6 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and further preferably is a CrO-based film containing chromium and oxygen (a CrO film, a CrON film, a CrOC film, or a CrOCN film).

[0102] Tantalum or a tantalum compound is preferably used as the material of the etching mask film 6. Examples of tantalum compounds include a material containing Ta and at least one element selected from N, O, B, and H. More preferably, the etching mask film 6 contains TaN, TaO, TaON, TaBN, TaBO, or TaBON.

[0103] Silicon or a silicon compound is preferably used as the material for the etching mask film 6. Examples of silicon compounds include a material containing Si and at least one element selected from N, O, C, and H, as well as metal silicon (metal silicide) and metal silicon compound (metal silicide compound) in which silicon and silicon compounds contain a metal. Examples of metal silicon compounds include a material containing a metal, Si, and at least one element selected from N, O, C, and H.

[0104] The thickness of the etching mask film 6 is preferably 3 nm or more in order to form a pattern with high accuracy in the absorber film 4. Moreover, the thickness of the etching mask film 6 is preferably 15 nm or less in order to make the thickness of the resist film 11 thin.

[0105] <<Backside conductive film 5>> A backside conductive film 5 for electrostatic chuck use can be formed on the backside (second main surface) of the substrate 10. The sheet resistance required for the backside conductive film 5 for electrostatic chuck use is typically 100 Ω / □ (Ω / square) or less. The backside conductive film 5 can be formed by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material of the backside conductive film 5 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the backside conductive film 5 is preferably a Cr compound containing Cr and at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the backside conductive film 5 is preferably Ta (tantalum), an alloy containing Ta, or a Ta compound containing any of these and at least one of boron, nitrogen, oxygen, and carbon. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0106] The thickness of the back surface conductive film 5 is not particularly limited as long as it functions as a film for an electrostatic chuck. The thickness of the back surface conductive film 5 is, for example, 10 nm to 200 nm.

[0107] <Reflective mask 200> This embodiment is a reflective mask 200 having a substrate 1, a multilayer reflective film 2 provided on the substrate 1 and reflecting EUV light, and an absorber pattern 4a obtained by patterning an absorber film 4 on the multilayer reflective film 2. The multilayer reflective film 2 included in the reflective mask 200 includes the above-mentioned first region 20. The first region 20 of the multilayer reflective film 2 included in the reflective mask 200 has similar characteristics to the first region 20 of the multilayer reflective film 2 of the above-mentioned multilayer reflective film-coated substrate 90, such as the fact that, in a cross-sectional image of the multilayer reflective film 2 captured with a dark-field scanning transmission electron microscope, the brightness distortion SkU of the upper portion 2b is greater than the brightness distortion SkL of the lower portion 2a.

[0108] As shown in FIG. 6D, the reflective mask 200 of this embodiment includes a substrate 1, a predetermined multilayer reflective film 2, and an absorber pattern 4a obtained by patterning the absorber film 4 of the reflective mask blank 100 described above.

[0109] 6A to 6D are schematic diagrams showing an example of a method for manufacturing the reflective mask 200 of this embodiment. The reflective mask blank 100 of this embodiment described above can be used to manufacture the reflective mask 200 of this embodiment. An example of the method for manufacturing the reflective mask 200 will be described below.

[0110] First, a reflective mask blank 100 is prepared, which includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, a protective film 3 formed on the multilayer reflective film 2, and an absorber film 4 formed on the protective film 3. Next, a resist film 11 is formed on the absorber film 4 to obtain the reflective mask blank 100 with the resist film 11 (FIG. 6A). As shown in FIG. 6A, the multilayer reflective film 2 of the reflective mask blank 100 has a predetermined first region 20. A pattern is written on the resist film 11 using an electron beam lithography system, and a developing and rinsing process is then performed to form a resist pattern 11a (FIG. 6B).

[0111] Using the resist pattern 11a as a mask, the absorber film 4 is dry-etched, thereby etching the portions of the absorber film 4 that are not covered by the resist pattern 11a, and an absorber pattern 4a is formed (FIG. 6C).

[0112] The etching gas for the absorber film 4 may be, for example, a fluorine-based gas and / or a chlorine-based gas. Examples of the fluorine-based gas include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2. Examples of the chlorine-based gas include Cl2, SiCl4, CHCl3, CCl4, and BCl3. Alternatively, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 at a predetermined ratio may be used. These etching gases may further contain an inert gas such as He and / or Ar, as necessary.

[0113] Next, the resist pattern 11a is removed with a resist remover. After the resist pattern 11b is removed, a wet cleaning process is performed using an acidic or alkaline aqueous solution, thereby obtaining the reflective mask 200 of this embodiment (FIG. 6D).

[0114] In addition, when a reflective mask blank 100 in which an etching mask film 6 is formed on an absorber film 4 is used, an additional process is performed in which a pattern (etching mask pattern) is formed on the etching mask film 6 using the resist pattern 11a as a mask, and then a pattern is formed on the absorber film 4 using the etching mask pattern as a mask.

[0115] The multilayer reflective film 2 of the reflective mask 200 of this embodiment obtained in this manner includes the above-mentioned predetermined first region 20. By including the predetermined first region 20 in the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment, it is possible to improve the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm. Therefore, by using the reflective mask 200 of this embodiment, it is possible to form a highly accurate transfer pattern on the semiconductor device substrate 60.

[0116] <Method of manufacturing a semiconductor device> The method for manufacturing a semiconductor device of this embodiment is a method for manufacturing a semiconductor device that includes using the reflective mask of this embodiment described above to transfer an absorber pattern 4a to a transfer target formed on a semiconductor device substrate 60. Specifically, the method for manufacturing a semiconductor device of this embodiment includes a step of performing a lithography process using an exposure apparatus and using the reflective mask 200 of this embodiment described above to form a transfer pattern on the transfer target.

[0117] A transfer pattern can be formed on a semiconductor device substrate 60 (transfer receiving body) by lithography using the reflective mask 200 of this embodiment. This transfer pattern has a shape that is the result of transferring the pattern of the reflective mask 200. By forming a transfer pattern on the semiconductor device substrate 60 using the reflective mask 200, a semiconductor device can be manufactured.

[0118] The multilayer reflective film 2 of the reflective mask 200 of this embodiment includes the above-described predetermined first region 20, thereby improving the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm. Therefore, by using the reflective mask 200 of this embodiment, a highly accurate transfer pattern can be formed on the semiconductor device substrate 60. Therefore, by using the reflective mask 200 of this embodiment, semiconductor devices can be made with higher density and higher accuracy.

[0119] A method of transferring a pattern onto a semiconductor device substrate 60 with a resist by using EUV light will be described with reference to FIG.

[0120] 11 shows a schematic configuration of an EUV exposure tool 50, which is an apparatus for transferring a transfer pattern to a resist film 11 formed on a semiconductor device substrate 60. The EUV exposure tool 50 includes an EUV light generation unit 51, an irradiation optical system 56, a reticle stage 58, a projection optical system 57, and a wafer stage 59, which are precisely arranged along the optical path axis of the EUV light. The container of the EUV exposure tool 50 is filled with hydrogen gas.

[0121] The EUV light generation unit 51 has a laser light source 52, a tin droplet generation unit 53, a capture unit 54, and a collector 55. When the high-power carbon dioxide laser from the laser light source 52 is irradiated onto the tin droplets emitted from the tin droplet generation unit 53, the tin droplets are converted into plasma, and EUV light with a wavelength of 13.53 nm is generated. The generated EUV light is collected by the collector 55 and passes through an irradiation optical system 56 to be incident on a reflective mask 200 set on a reticle stage 58.

[0122] The EUV light reflected by the reflective mask 200 is reduced by the projection optical system 57 to a pattern image light, typically about 1 / 4, and projected onto the semiconductor device substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred to a resist film on the semiconductor device substrate 60. A resist pattern can be formed on the semiconductor device substrate 60 by developing the exposed resist film. An integrated circuit pattern can be formed on the semiconductor device substrate 60 by etching the semiconductor device substrate 60 using the resist pattern as a mask. A semiconductor device is manufactured through these and other necessary processes. [Example]

[0123] Examples and comparative examples will be described below.

[0124] (Preparation of Multilayer Reflective Film Coated Substrate 90 of Examples 1 to 3 and Comparative Examples 1 and 2) First, a substrate 1 having a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) with a polished first and second main surfaces was prepared as the substrate 1 for Examples 1 and 3 and Comparative Examples 1 and 2. This substrate 1 was made of low thermal expansion glass (SiO2-TiO2-based glass). The main surfaces of the substrate 1 were polished through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0125] As the substrate 1 of Example 2, a substrate 1 made of low thermal expansion glass (SiO2-TiO2-based glass) different from the substrate 1 of Examples 1 and 3 and Comparative Examples 1 and 2 was prepared. The substrate 1 of Example 2 is a substrate 1 of 6025 size (approximately 152 mm × 152 mm × 6.35 mm) whose first and second main surfaces are polished, similar to the substrate 1 of Examples 1 and 3 and Comparative Examples 1 and 2. As with the substrate 1 of Examples 1 and 3 and Comparative Examples 1 and 2, the main surfaces of the substrate 1 of Example 2 were polished by a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0126] Ti of the substrate 1 in Examples 1 to 3 and Comparative Examples 1 and 2 3+ The concentration was measured by electron spin resonance (ESR) and found to be 3+ The concentration was below the measurement limit of 0.1 ppm by weight. 3+ The concentration was measured by electron spin resonance (ESR) and found to be 3+ The concentration was 0.4 ppm by weight.

[0127] Next, a multilayer reflective film 2 consisting of a low refractive index layer and a high refractive index layer was formed on the main surface (first main surface) of the substrate 1. Table 1 shows the materials and deposition methods of the multilayer reflective film 2 of Examples 1 to 3 and Comparative Examples 1 and 2. In Table 1, the "Material of multilayer reflective film 2" column for Example 1 lists "Mo / Si," which means that the material of the low refractive index layer is Mo and the material of the high refractive index layer is Si. Similarly, the "Material of multilayer reflective film 2" column for Example 3 lists "Ru / Si," which means that the material of the low refractive index layer is Ru and the material of the high refractive index layer is Si. The "Deposition method" column in Table 1 lists the deposition method of the multilayer reflective film 2. In the "Deposition method" column, "ion beam" refers to ion beam sputtering, and "magnetron" refers to magnetron sputtering.

[0128] The multilayer reflective coatings 2 of Examples 1 and 2 and Comparative Examples 1 and 2 were formed by magnetron sputtering using a Si target and a Mo target and Kr gas. First, a high refractive index layer of Si was formed to a thickness of 4.2 nm using the Si target so as to be in contact with the main surface of the substrate 1, and then a low refractive index layer of Mo was formed to a thickness of 2.8 nm using the Mo target.

[0129] The multilayer reflective coating 2 of Example 3 was formed by ion beam sputtering using a Si target and a Ru target and Kr gas. First, a high refractive index layer of Si was formed to a thickness of 4.2 nm using the Si target so as to be in contact with the main surface of the substrate 1, and then a low refractive index layer of Ru was formed to a thickness of 2.8 nm using the Ru target.

[0130] The multilayer reflective film 2 in Examples 1 to 3 and Comparative Examples 1 and 2 was formed by laminating 40 periods (pairs) of one high refractive index layer and one low refractive index layer on the main surface of the substrate 1. The thickness of the 40 periods of the multilayer reflective film 2 was 280 nm.

[0131] Next, light was irradiated from the second main surface of the substrate 1 opposite to the first main surface on which the multilayer reflective film 2 was formed, thereby performing a light irradiation treatment on the multilayer reflective film 2.

[0132] In the light irradiation treatment for the multilayer reflective film 2 in Examples 1 to 3, a xenon lamp was used as a lamp, and 15 J / cm 2 was applied from the second main surface of the substrate 1 to the multilayer reflective film 2. 2 The sample was irradiated once with a pulse width of 5 milliseconds at an irradiation intensity of 1000 kJ / s.

[0133] The light irradiation treatment for Comparative Example 1 was carried out under conditions that provided a lower annealing effect on the multilayer reflective film 2 than the light irradiation treatments for Examples 1 to 3. Specifically, the light irradiation treatment for Comparative Example 1 was carried out using a xenon lamp as the lamp, and irradiating the multilayer reflective film 2 from the second main surface of the substrate 1 with 15 J / cm 2 . 2 The sample was irradiated once with a pulse width of 1 millisecond at an irradiation intensity of 1000 kJ / s.

[0134] The light irradiation treatment for Comparative Example 2 was carried out under conditions that provided a higher annealing effect on the multilayer reflective film 2 than the light irradiation treatments for Examples 1 to 3. Specifically, the light irradiation treatment for Examples 1 and 2 was carried out using a xenon lamp as the lamp, and irradiating the multilayer reflective film 2 from the second main surface of the substrate 1 with 15 J / cm 2 . 2 The sample was irradiated once with a pulse width of 10 milliseconds at an irradiation intensity of 1000 kJ / s.

[0135] In this manner, the multilayer reflective film coated substrates 90 of Examples 1 to 3 and Comparative Examples 1 and 2 were produced.

[0136] (Measurement of the reflection spectrum of the multilayer reflective film 2) The wavelength dependence of reflectance (reflection spectrum) of the multilayer reflective coating 2 of the multilayer reflective film coated substrate 90 of the example and comparative example prepared as described above was measured near EUV light with a wavelength of 13.53 nm. Table 2 shows the reflectance for EUV light with a wavelength of 13.53 nm and the absolute value of the slope of the reflection spectrum at a wavelength of 13.53 nm. The absolute value of the slope at a wavelength of 13.53 nm was obtained by differentiating R(λ), which is the wavelength dependence of the reflectance, with respect to the wavelength λ. The slope of the reflection spectrum at a wavelength of 13.53 nm is d / dλ·R(λ) (λ=13.53 nm).

[0137] (Measurement of the luminance distortion of the multilayer reflective film 2) The distortion of luminance of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of the example and comparative example prepared as described above was measured by the following method.

[0138] First, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of each of the examples and comparative examples was observed with a dark-field scanning transmission electron microscope (DF-STEM) to obtain a DF-STEM image. Fig. 12 shows a schematic diagram of the optical system of the DF-STEM.

[0139] For DF-STEM observation, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of the example and comparative example was cut out so as to be able to see the cross section of the multilayer reflective film 2 stacked 40 times, and this was used as sample 304. For the multilayer reflective film 2 of the example and comparative example, DF-STEM observation was performed on three locations of the sample 304. Specifically, when the center of the 152 mm × 152 mm multilayer reflective film coated substrate 90 is set to coordinates (0 mm, 0 mm), the positions of the sample 304 were (0 mm, 0 mm), (20 mm, 20 mm), and (40 mm, 40 mm), and the multilayer reflective film 2 at these three locations was cut out as sample 304.

[0140] Next, using a DF-STEM optical system as shown in Fig. 12, electrons diffracted from the sample 304 (multilayer reflective film 2) and inelastically scattered electrons 306 were detected by an annular detector 310. To obtain the DF-STEM image, a scanning transmission electron microscope ARM200F (manufactured by JEOL Ltd.) was used. The measurement conditions were as follows: Acceleration voltage of incident electrons 302: 200 kV Angular range measured by the annular detector 310 (β1 to β2): β1 = 68 mrad, β2 = 280 mrad

[0141] Of the four regions of the annular detector 310 shown in FIG. 12, a DF-STEM image was obtained by imaging using the measurement signal from the lower region 310b or the upper region 310d (the 6 o'clock region 310b or the 12 o'clock region 310d).

[0142] FIG. 13 shows an example of a DF-STEM image of the multilayer reflective film 2 obtained as described above.

[0143] Next, the obtained DF-STEM image was subjected to image analysis. In the DF-STEM image of sample 304 (multilayer reflective coating 2), the region for image analysis of the lower part 2a of multilayer reflective coating 2 was a rectangular region with a thickness of 140 nm and a width of 900 nm that contacted the surface on the substrate 1 side of the cross section of 40-period multilayer reflective coating 2. The region for image analysis of the upper part 2b of multilayer reflective coating 2 was a region adjacent to the region for image analysis of the lower part 2a, and was a rectangular region with a thickness of 140 nm and a width of 900 nm that contacted the surface on the opposite side from substrate 1 of the cross section of 40-period multilayer reflective coating 2.

[0144] Next, the DF-STEM image was analyzed, and the pixels in the image analysis region of the DF-STEM image were quantified as a grayscale ranging from 0 to 255. Higher grayscale values ​​indicate colors closer to white, while lower grayscale values ​​indicate colors closer to black. The number of pixels in the image analysis region of the DF-STEM image was set to 1024 x 1024. The gray values ​​of a given grayscale gradation in the image analysis region can be expressed as a histogram graph (distribution of gradation and gray values) by plotting the grayscale gradation on the horizontal axis.

[0145] Next, skewness was calculated by a known statistical method using only data from the gradation and gray value distribution data of the image analysis region in the grayscale gradation range of 150 to 255. The skewness obtained using data in the gradation range of 150 to 255 can be regarded as a value indicating the brightness of the DF-STEM image of the multilayer reflective film 2.

[0146] Table 1 shows the skewness of luminance (skewness SkL and skewness SkU) of the lower portion 2a and upper portion 2b of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of the example and comparative example, which were determined as described above. The skewness of luminance SkL of the lower portion 2a and the skewness of luminance SkU of the upper portion 2b were calculated as the average values ​​of the measurements taken at three locations. Table 1 also shows the average values ​​of the grayscale gradation of the lower portion 2a and upper portion 2b. The average value of the grayscale gradation was also calculated as the average value of the measurements taken at three locations.

[0147] As shown in Table 1, the luminance distortion SkU of the upper portion 2b of the multilayer reflective coating 2 of the multilayer reflective coating substrate 90 of Examples 1 to 3 was larger than the luminance distortion SkL of the lower portion 2a. Therefore, it is clear that the multilayer reflective coating 2 of the multilayer reflective coating substrate 90 of Examples 1 to 3 has the predetermined first region 20. Furthermore, as shown in Table 1, the luminance distortion SkU of the upper portion 2b of the multilayer reflective coating 2 of the multilayer reflective coating substrate 90 of Comparative Examples 1 and 2 was not larger than the luminance distortion SkL of the lower portion 2a. Therefore, it is clear that the multilayer reflective coating 2 of the multilayer reflective coating substrate 90 of Comparative Examples 1 and 2 does not have the predetermined first region 20.

[0148] Furthermore, in the multilayer reflective film-coated substrates 90 of Examples 1 to 3 and Comparative Examples 1 and 2, the lower part 2a of the multilayer reflective film 2 was defined as a region extending from the interface between the main surface of the substrate 1 and the multilayer reflective film 2 in the film thickness direction to 0 nm or more and 30 nm or less, and the upper part 2ba was defined as a region extending from the interface to 140 nm or more and 170 nm or less in the film thickness direction, and the skewness of luminance SkU of the upper part 2b and the skewness of luminance SkL of the lower part 2a were calculated in the same manner as above. As a result, the skewness of luminance SkU of the upper part 2b of the multilayer reflective film 2 of the multilayer reflective film-coated substrates 90 of Examples 1 to 3 was larger than the skewness of luminance SkL of the lower part 2a. Furthermore, the skewness of luminance SkU of the upper part 2b of the multilayer reflective film 2 of the multilayer reflective film-coated substrates 90 of Comparative Examples 1 and 2 was not larger than the skewness of luminance SkL of the lower part 2a. Furthermore, in the multilayer reflective film-coated substrates 90 of Examples 1 to 3 and Comparative Examples 1 and 2, the lower part 2a of the multilayer reflective film 2 was defined as a region extending from the interface between the main surface of the substrate 1 and the multilayer reflective film 2 in the film thickness direction by 70 nm to 140 nm, and the upper part 2b was defined as a region extending from the interface in the film thickness direction by 210 nm to 280 nm. The luminance distortion factor SkU of the upper part 2b and the luminance distortion factor SkL of the lower part 2a were calculated in the same manner as above. As a result, the luminance distortion factor SkU of the upper part 2b of the multilayer reflective film 2 of the multilayer reflective film-coated substrates 90 of Examples 1 to 3 was larger than the luminance distortion factor SkL of the lower part 2a. Furthermore, the luminance distortion factor SkU of the upper part 2b of the multilayer reflective film 2 of the multilayer reflective film-coated substrates 90 of Comparative Examples 1 and 2 was not larger than the luminance distortion factor SkL of the lower part 2a. Therefore, it was clear that the relationship between the skewness SkU of the luminance of the upper portion 2b and the skewness SkL of the luminance of the lower portion 2a does not depend on the film thickness of the upper portion 2b and the lower portion 2a or the position in the film thickness direction.

[0149] As shown in Table 2, the reflectance of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of Examples 1 to 3 to EUV light with a wavelength of 13.53 nm was comparable to or higher than the reflectance of the multilayer reflective coating 2 of Comparative Examples 1 and 2. Therefore, it is clear that the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of Examples 1 to 3 can maintain a high reflectance of the multilayer reflective coating 2 to EUV light with a wavelength of 13.53 nm.

[0150] As shown in Table 2, the absolute values ​​of the slopes of the reflection spectra of the multilayer reflective coatings 2 of the multilayer reflective coating-coated substrates 90 of Examples 1 to 3 at a wavelength of 13.53 nm were smaller than the absolute values ​​of the slopes of the multilayer reflective coatings 2 of Comparative Examples 1 and 2. Therefore, it is clear that the multilayer reflective coatings 2 of the multilayer reflective coating-coated substrates 90 of Examples 1 to 3 can improve the controllability of the reflectance of the multilayer reflective coating 2 for EUV light with a wavelength of 13.53 nm.

[0151] As described above, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of Examples 1 to 3 can improve the controllability of the reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm while maintaining a high reflectance of the multilayer reflective film 2 for EUV light with a wavelength of 13.53 nm. A reflective mask blank and a reflective mask can be manufactured using the multilayer reflective film coated substrate 90 of Examples 1 to 3. It is clear that a high-precision semiconductor device can be manufactured using a reflective mask manufactured in this manner.

[0152] [Table 1]

[0153] [Table 2] [Explanation of symbols]

[0154] 1 board 2 Multilayer reflective film 2a bottom 2b upper part 3 Protective film 4. Absorber membrane 4a Absorber pattern 5 Backside conductive film 6 Etching mask film 11 Resist film 11a, 11b Resist patterns 20 1st area 50 EUV exposure equipment 51 EUV light generation section 52 Laser light source 53 Tin droplet generation part 54 Capture unit 55 Collector 56 Irradiation optical system 57 Projection optical system 58 Reticle Stage 59 Wafer Stage 60 Substrate for semiconductor device 90 Multilayer reflective film substrate 100 Reflective Mask Blanks 200 Reflective Mask 300 Optical system of dark-field scanning transmission electron microscope (DF-STEM) 302 Incident electron 304 Samples 306 Diffracted and Inelastically Scattered Electrons 310 Annular Detector 310a Right area of ​​the annular detector (area at 3 o'clock) 310b The area below the annular detector (the area at 6 o'clock) 310c Left area of ​​the annular detector (area at 9 o'clock) 310d Upper area of ​​the annular detector (area at 12 o'clock)

Claims

1. A substrate; a multilayer reflective film provided on a main surface of the substrate, the multilayer reflective film has a lower portion closer to the major surface of the substrate and an upper portion farther from the major surface; A substrate with a multilayer reflective film, characterized in that in a cross-sectional image of the multilayer reflective film taken with a dark-field scanning transmission electron microscope, the multilayer reflective film includes a first region in which the brightness distortion SkU of the upper portion is greater than the brightness distortion SkL of the lower portion.

2. 2. The multilayer reflective film coated substrate according to claim 1, wherein the first region is positioned so as to include at least a part of the multilayer reflective film when viewed from above.

3. 3. The multilayer reflective film-coated substrate according to claim 1, wherein the first region is positioned so as to include a square having a side length of 132 mm and having a diagonal intersection at the center of the main surface of the substrate when viewed from above.

4. 3. A substrate with a multilayer reflective film as described in claim 1 or 2, characterized in that the lower part corresponds to the lower half, which is 50% of the thickness of the multilayer reflective film on the substrate side, and the upper part corresponds to the upper half excluding the lower half.

5. 3. The multilayer reflective film substrate according to claim 1, wherein the multilayer reflective film has alternating low refractive index layers and high refractive index layers, the low refractive index layers containing at least one selected from molybdenum and ruthenium, and the high refractive index layers containing silicon.

6. A substrate; a multilayer reflective film provided on a main surface of the substrate; an absorber film provided on the multilayer reflective film, the multilayer reflective film has a lower portion closer to the major surface of the substrate and an upper portion farther from the major surface; A reflective mask blank characterized in that, in a cross-sectional image of the multilayer reflective film captured with a dark-field scanning transmission electron microscope, the multilayer reflective film includes a first region in which the brightness distortion SkU of the upper portion is larger than the brightness distortion SkL of the lower portion.

7. 7. The reflective mask blank according to claim 6, wherein the first region is positioned so as to include at least a part of the multilayer reflective film when viewed from above.

8. 8. The reflective mask blank according to claim 6, wherein the first region is positioned so as to include a square having a side length of 132 mm and having a diagonal intersection at the center of the main surface of the substrate when viewed from above.

9. 8. The reflective mask blank according to claim 6, wherein the lower portion corresponds to the lower half of the multilayer reflective film, which is 50% of the thickness of the multilayer reflective film on the substrate side, and the upper portion corresponds to the upper half excluding the lower half.

10. 8. The reflective mask blank according to claim 6, wherein the multilayer reflective film has low refractive index layers and high refractive index layers alternately stacked, the low refractive index layers containing at least one selected from molybdenum and ruthenium, and the high refractive index layers containing silicon.

11. A substrate; a multilayer reflective film provided on a main surface of the substrate; an absorber pattern provided on the multilayer reflective film, the multilayer reflective film has a lower portion closer to the major surface of the substrate and an upper portion farther from the major surface; A reflective mask characterized in that, in a cross-sectional image of the multilayer reflective film taken with a dark-field scanning transmission electron microscope, the multilayer reflective film includes a first region in which the brightness distortion SkU of the upper portion is greater than the brightness distortion SkL of the lower portion.

12. 12. The reflective mask according to claim 11, wherein the first region is positioned so as to include at least a part of the multilayer reflective film when viewed from above.

13. 13. The reflective mask according to claim 11, wherein the first region is positioned so as to include a square having a side length of 132 mm and diagonals intersecting at the center of the main surface of the substrate when viewed from above.

14. 13. The reflective mask according to claim 11, wherein the lower portion corresponds to the lower half of the multilayer reflective film, which is 50% of the thickness of the multilayer reflective film on the substrate side, and the upper portion corresponds to the upper half excluding the lower half.

15. 13. The reflective mask according to claim 11, wherein the multilayer reflective film has alternating low-refractive index layers and high-refractive index layers, the low-refractive index layers containing at least one selected from molybdenum and ruthenium, and the high-refractive index layers containing silicon.

16. 13. A method for manufacturing a semiconductor device, comprising: transferring the absorber pattern onto a transfer target formed on a substrate for a semiconductor device, using the reflective mask according to claim 11 or 12.

Images