Substrate with multilayered reflection film, reflection type mask blank, reflection type mask, and method for producing semiconductor device

Abstract

To provide a substrate with a multilayered reflection film for producing a reflection type mask blank capable of suppressing film peeling at a peripheral part of a multilayered reflection film when drawing a resist film having a predetermined pattern using a drawing apparatus in a production process of a reflection type mask.SOLUTION: A substrate with a multilayered reflection film includes: a substrate; and a multilayered reflection film provided on the substrate, wherein the multilayered reflection film includes a multilayered film obtained by alternately laminating a low refractive index layer and a high refractive index layer, and a skewness of at least a part of the multilayered reflection film within a range of 6 mm toward a center from a side face of the substrate is 1.3 or lower when a degree of crystallinity of the multilayered film is expressed by the skewness.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 in the area where the absorber pattern is not formed is transferred onto a semiconductor substrate (transfer target) such as a silicon wafer through a reflection optical system.

[0004] The absorber pattern of the reflective mask can be formed by etching a part of the absorber film of the reflective mask blank, which is the original, into a predetermined pattern using a lithography process.

[0005] Patent Document 1 describes a mask blank, which is an original plate for producing an exposure mask. The mask blank described in Patent Document 1 is a mask blank for electron beam lithography in which a resist pattern is formed by electron beam lithography. The mask blank described in Patent Document 1 is a mask blank in which a transfer pattern formation thin film and an etching mask film made of an inorganic material that is resistant to etching of the transfer pattern formation thin film are formed in this order on a substrate. Patent Document 1 describes that the transfer pattern formation thin film of the mask blank is made of a material that is conductive to the extent that it does not charge up during electron beam lithography and patterning, and is formed from the main surface of the substrate to the side surface or chamfered surface of the substrate.

[0006] Patent Document 2 describes a method for manufacturing a multilayer reflective film-coated substrate for EUV lithography, in which a multilayer reflective film having a configuration in which high-refractive-index layers and low-refractive-index layers are alternately stacked on a main surface of the substrate. The manufacturing method described in Patent Document 2 includes a multilayer reflective film formation step of forming a multilayer reflective film on the main surface of the substrate so as to provide a film thickness gradient region in which the film thickness decreases from the inside to the outside of the substrate at the peripheral portion of the main surface, and a fiducial mark formation step of forming a fiducial mark, which serves as a reference for defect positions in defect information on the surface of the multilayer reflective film-coated substrate, in the film thickness gradient region by removing at least a portion of the multilayer reflective film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-238014 [Patent Document 2] International Publication No. WO2013 / 146488 Summary of the Invention [Problem to be solved by the invention]

[0008] The absorber pattern of a reflective mask can be formed by etching a portion of the absorber film of a reflective mask blank into a predetermined pattern using a lithography process. In the lithography process for manufacturing a reflective mask from a reflective mask blank, a resist film is first formed on the absorber film of the reflective mask blank. The reflective mask blank with the resist film is set in a lithography device to write a predetermined pattern on the resist film. By using an electron beam lithography device as the lithography device and a resist for electron beam lithography as the resist film material, a predetermined fine pattern can be written on the resist film. By using the fine pattern formed in the resist film as a mask, a reflective mask having a fine absorber pattern can be manufactured.

[0009] When a predetermined pattern is written on a resist film using an electron beam lithography system, a reflective mask blank may become charged up. If the reflective mask blank becomes charged up, the trajectory of the electron beam used for writing changes, making it difficult to write the pattern as designed on the resist film. Therefore, it is necessary to prevent the reflective mask blank from becoming charged up when writing using an electron beam lithography system. In an electron beam lithography system, the reflective mask blank can be prevented from becoming charged up by pressing a conductive pin against the peripheral edge of the reflective mask blank set on the stage to ground it.

[0010] A multilayer film including a reflective multilayer film is formed on the peripheral portion of a reflective mask blank. When a conductive pin for preventing charge-up is pressed against the multilayer film during lithography using an electron beam lithography apparatus, peeling of the multilayer reflective film may occur at the peripheral portion depending on the shape of the tip of the conductive pin.

[0011] Furthermore, even when a lithography system other than an electron beam lithography system is used, the reflective mask blank may be pressed down with pins to prevent the reflective mask blank from moving during lithography. In this case, film peeling may occur at the peripheral portion of the multilayer reflective film, as in the case of using an electron beam lithography system.

[0012] Therefore, an object of the present invention is to provide a multilayer reflective film coated substrate for manufacturing a reflective mask blank that can suppress film peeling at the peripheral portion of the multilayer reflective film when a resist film of a predetermined pattern is written using a writing device in the manufacturing process of a reflective mask.Another object of the present invention is to provide a reflective mask blank that can suppress film peeling at the peripheral portion of the multilayer reflective film when a resist film of a predetermined pattern is written using a writing device in the manufacturing process of a reflective mask. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention has the following configuration.

[0014] (Configuration 1) Configuration 1 is a multilayer reflective film-coated substrate including a substrate and a multilayer reflective film provided on the substrate, the multilayer reflective film includes a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked, This is a multilayer reflective film-coated substrate, characterized in that when the crystallinity of the multilayer reflective film is expressed as distortion, the distortion in at least a portion of the multilayer reflective film within a range of 6 mm from the side of the substrate toward the center is 1.3 or less.

[0015] (Configuration 2) Configuration 2 is the multilayer reflective film coated substrate of Configuration 1, wherein the difference between the maximum and minimum distortion values ​​in the multilayer reflective film within a range of 1.8 mm to 2.4 mm from the side surface of the substrate is 0.7 or less.

[0016] (Configuration 3) In a third aspect, the multilayer reflective film has a peripheral portion, the peripheral portion of the multilayer reflective film has a gradient thickness region in which the film thickness decreases along a direction from the center toward the outside of the main surface of the substrate, 3. The multilayer reflective film coated substrate according to claim 1, wherein the gradient of the gradient film thickness region is 100 nm / mm or more and 400 nm / mm or less.

[0017] (Configuration 4) A fourth aspect of the present invention is the multilayer reflective film coated substrate of any one of the first to third aspects, further comprising a protective film on the multilayer reflective film.

[0018] (Configuration 5) Configuration 5 is a reflective mask blank including an absorber film provided on the multilayer reflective film-coated substrate of any one of Configurations 1 to 4.

[0019] (Configuration 6) Configuration 6 is a reflective mask including an absorber pattern formed by patterning the absorber film in the reflective mask blank of configuration 5.

[0020] (Configuration 7) Configuration 7 is a method for manufacturing a semiconductor device, characterized by including a step of performing a lithography process using an exposure apparatus with the reflective mask of configuration 6 to form a transfer pattern on a transfer target. [Effects of the Invention]

[0021] An object of the present invention is to provide a multilayer reflective film coated substrate for manufacturing a reflective mask blank that can suppress film peeling at the peripheral portion of the multilayer reflective film when a resist film of a predetermined pattern is written using a writing device in the manufacturing process of a reflective mask.Furthermore, the present invention can provide a reflective mask blank that can suppress film peeling at the peripheral portion of the multilayer reflective film when a resist film of a predetermined pattern is written using a writing device in the manufacturing process of a reflective mask. [Brief explanation of the drawings]

[0022] [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] 1 is a cross-sectional view schematically illustrating a portion of a peripheral portion of an example of a multilayer reflective film coated substrate of the present embodiment. [Figure 8] FIG. 2 is a cross-sectional schematic view showing a part of the peripheral portion of an example of a reflective mask blank of the present embodiment. [Figure 9] FIG. 1 is a schematic diagram illustrating an example of an EUV exposure apparatus. [Figure 10]1 is a schematic diagram showing an example of an optical system of a dark-field scanning transmission electron microscope (DF-STEM). DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] FIG. 1 is a cross-sectional view schematically illustrating an example of a multilayer reflective film-coated substrate 90 according to this embodiment. The multilayer reflective film-coated substrate 90 according to this embodiment includes a substrate 1 and a multilayer reflective film 2 provided on 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 transfer pattern formation region 24 and a peripheral portion 22 located outside the transfer pattern formation region 24. A multilayer reflective film-coated substrate 90 according to another embodiment, as shown in FIG. 2, also has a transfer pattern formation region 24 and a peripheral portion 22, similar to the embodiment shown in FIG. 1. 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 main surface opposite to the side on which the multilayer reflective film 2 is formed; also referred to as the "second main surface").

[0025] Fig. 2 is a cross-sectional view schematically illustrating another example of a multilayer reflective film-coated substrate 90 according to 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. A back surface conductive film 5 for use in an electrostatic chuck may be formed on the back surface (second main surface) of the substrate 1.

[0026] 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.

[0027] <Substrate with multilayer reflective film 90> The multilayer reflective film coated substrate 90 of this embodiment will be specifically described.

[0028] <<Board 1>> To prevent distortion of the transferred pattern due to heat during exposure to EUV light, the substrate 1 preferably has a low thermal expansion coefficient within the range of 0±5 ppb / °C. Materials having a low thermal expansion coefficient within this range include, for example, SiO2-TiO2-based glass and multi-component glass ceramics.

[0029] The main surface 1a (first main surface 1a) 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 1a 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.

[0030] 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.

[0031] 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.

[0032] <<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 is formed on a main surface 1a (first main surface 1a) of the substrate 1. The multilayer reflective film 2 provides the reflective mask 200 with the function of reflecting EUV light. The multilayer reflective film 2 is a multilayer film formed by alternately laminating low-refractive index layers and high-refractive index layers, each of which mainly contains elements with different refractive indices. In this specification, of the surfaces of the multilayer reflective film-coated substrate 90 of this embodiment, the main surface 1a on which the multilayer reflective film 2 is formed may be referred to as the "first main surface of the multilayer reflective film-coated substrate 90."

[0033] 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 40 to 60 cycles.

[0034] 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, thereby 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.

[0035] The high-refractive index layer is preferably a layer containing silicon (Si). Examples of Si-containing materials 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 may be a metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof. These metals or alloys may also contain 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 40 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., 13.5 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., 13.5 nm).

[0036] 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 enhance the reflectivity with respect to EUV light. Conventional Mo / Si multilayer reflective films have been used as multilayer reflective films for reflective masks and are highly reliable. Furthermore, compared to Mo / Si multilayer reflective films, Ru / Si multilayer reflective films can provide a shallower effective reflective surface, which is advantageous for suppressing the 3D effect.

[0037] 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), molybdenum (Mo), 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.

[0038] 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.

[0039] In the multilayer reflective film coated substrate 90 of this embodiment, the crystallinity of the multilayer reflective film 2 is defined by skewness (Ssk). The cross-sectional schematic diagrams of the multilayer reflective film coated substrate 90 shown in FIGS. 1 and 2 show a peripheral portion 22 of the multilayer reflective film 2 and a transfer pattern formation region 24. The transfer pattern formation region 24 is a region where an absorber pattern 4a of a reflective mask 200 (described later) is disposed. In this specification, the "periphery 22 of the multilayer reflective film 2" refers to the region of the multilayer reflective film 2 that is outside (around) the transfer pattern formation region 24. The peripheral portion 22 is a region that does not contribute to the transfer of a circuit pattern in EUV lithography.

[0040] On the first main surface of the multilayer reflective film-coated substrate 90, the transfer pattern formation region 24 of the multilayer reflective film 2 is an area surrounded by, for example, 104 mm × 104 mm or 132 mm × 132 mm. The peripheral edge portion 22 is the area of ​​the multilayer reflective film 2 from the outer boundary of the transfer pattern formation region 24 to the chamfered surface 1c formed between the main surface 1a and the side surface 1b of the substrate 1 of the multilayer reflective film-coated substrate 90, and is, for example, the portion outside the 104 mm × 104 mm area or the 132 mm × 132 mm area. The peripheral edge portion 22 can include the chamfered surface 1c.

[0041] In the multilayer reflective film-coated substrate 90 of this embodiment, when the crystallinity of the multilayer reflective film 2 is expressed as strain, the strain is within a predetermined range in at least a portion of the multilayer reflective film 2 within a range of a predetermined distance from the side surface 1b toward the center of the substrate 1. Specifically, in the multilayer reflective film-coated substrate 90 of this embodiment, when the crystallinity is expressed as strain, the strain is 1.3 or less in at least a portion of the multilayer reflective film 2 within a range of 6 mm from the side surface 1b toward the center of the substrate 1.

[0042] When a reflective mask 200 is manufactured from a reflective mask blank 100 using the multilayer reflective film coated substrate 90 of this embodiment, a predetermined pattern is written on a resist film 11 (see FIG. 6A) using an electron beam lithography system. During this writing, the reflective mask blank 100 may become charged up. If the reflective mask blank 100 becomes charged up, the trajectory of the electron beam used for writing changes, making it impossible to write an accurate pattern. Therefore, when writing using an electron beam lithography system, it is necessary to prevent the reflective mask blank 100 from becoming charged up. When the reflective mask blank 100 is set on the stage of the electron beam lithography system, a conductive pin is pressed against the peripheral edge 22 of the reflective mask blank 100 to ground it, thereby preventing the reflective mask blank 100 from becoming charged up.

[0043] A multilayer film including a multilayer reflective film 2 is formed on a peripheral edge portion 22 of the reflective mask blank 100. In a conventional reflective mask blank 100, when a conductive pin is pressed against the multilayer film, film peeling may occur at the peripheral edge portion 22 of the multilayer reflective film 2. The multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment can enhance the crystallinity of the peripheral edge portion 22 of the multilayer reflective film 2 by setting the strain index, which indicates the degree of crystallinity of the peripheral edge portion 22 of the multilayer reflective film 2, within a predetermined range. As a result, in the process of manufacturing a reflective mask 200 using the reflective mask blank 100 including the multilayer reflective film-coated substrate 90 of this embodiment, film peeling at the peripheral edge portion 22 of the multilayer reflective film 2 can be suppressed when a resist film 11 having a predetermined pattern is written using a writing device.

[0044] The strain, which indicates the degree of crystallinity of the multilayer reflective coating 2, is related to the size of the crystallized region. A smaller strain means an increased crystallized region. By reducing the strain of the peripheral portion 22 of the multilayer reflective coating 2, the crystallinity of the peripheral portion 22 of the multilayer reflective coating 2 can be increased. As a result, peeling of the multilayer reflective coating 2 at the peripheral portion 22 can be suppressed when a resist film 11 having a predetermined pattern is drawn using a drawing device.

[0045] FIG. 7 is a schematic cross-sectional view showing a part of the peripheral edge portion 22 of an example of a multilayer reflective film coated substrate 90 of this embodiment.

[0046] The conductive pins used to prevent charge-up in an electron beam lithography system are typically pressed against a position within 6 mm of the side surface 1b of the substrate 1 of the reflective mask blank 100, more often within 4 mm. Therefore, to prevent film peeling at the peripheral edge 22 of the multilayer reflective coating 2, it is necessary to increase the crystallinity of the multilayer reflective coating 2 in the peripheral edge 22 of the multilayer reflective coating 2, particularly in a range within 6 mm from the side surface 1b of the substrate 1 toward the center, and it is more preferable to increase the crystallinity of the multilayer reflective coating 2 within a range within 4 mm. Therefore, in the reflective mask blank 100 of this embodiment, it is necessary for the distortion of at least a portion of the multilayer reflective coating 2 within a range within 6 mm, preferably within 4 mm, from the side surface 1b of the substrate 1 toward the center to be within a predetermined range. The range within 6 mm (preferably within 4 mm) from the side surface 1b of the substrate 1 toward the center is included in the peripheral edge 22 of the multilayer reflective coated substrate 90, and is the portion of the peripheral edge 22 close to the side surface 1b of the substrate 1.

[0047] Specifically, in the multilayer reflective film coated substrate 90 of this embodiment, when the degree of crystallinity is expressed as skewness in at least a portion of the peripheral portion 22 of the multilayer reflective film 2 (a range of 6 mm or less (preferably 4 mm or less) from the side surface 1b of the substrate 1 toward the center), the skewness is 1.3 or less, and preferably 1.0 or less. Furthermore, if the skewness is too small, elements from the low refractive index layer may diffuse excessively into the high refractive index layer, resulting in an expanded region of high crystallinity and a deterioration in cleaning resistance. Therefore, the lower limit of the skewness is preferably -1.3 or more, and more preferably -1.0 or more.

[0048] When the crystallinity (skewness) of at least a portion of the peripheral portion 22 of the multilayer reflective coating 2 is within the above-described range, this means that the peripheral portion 22 of the multilayer reflective coating 2 has a high degree of crystallinity. The crystalline state of the peripheral portion 22 means that it has a crystalline structure rather than an amorphous structure. By increasing the crystallinity of the peripheral portion 22 of the multilayer reflective coating 2, the film density of the peripheral portion 22 of the multilayer reflective coating 2 can be increased. When a conductive pin is pressed against the multilayer film, including the multilayer reflective coating 2, of the reflective mask blank 100 to prevent charge-up during writing using an electron beam writing apparatus, film peeling may occur at the peripheral portion 22 of the multilayer reflective coating 2. By using the multilayer reflective coated substrate 90 of this embodiment, film peeling at the peripheral portion 22 of the multilayer reflective coating 2 can be suppressed during writing of a predetermined pattern of the resist film 11 using a writing apparatus.

[0049] The strain index indicating the degree of crystallinity can be within the above-mentioned predetermined range in at least a portion of the multilayer reflective film 2 within a range of 6 mm (preferably within 4 mm) from the side surface 1b toward the center of the substrate 1. Furthermore, the strain index indicating the degree of crystallinity can be within the above-mentioned predetermined range over the entire peripheral portion 22 of the multilayer reflective film 2.

[0050] Furthermore, the strain indicating the degree of crystallinity in the peripheral portion 22 of the multilayer reflective film 2 does not have to be constant in the film thickness direction of the multilayer reflective film 2, and can have a distribution that is inclined in the film thickness direction. For example, the crystallinity of the upper portion of the multilayer reflective film 2 can be made lower (the strain is larger) than the crystallinity of the lower portion (the substrate 1 side of the multilayer reflective film 2).

[0051] Next, the skewness, which indicates the degree of crystallinity of the multilayer reflective film 2, will be described.

[0052] The peripheral portion 22 of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment has a high degree of crystallinity. In the multilayer reflective film coated substrate 90 of this embodiment, the degree of crystallinity of the multilayer reflective film 2 can be indicated by skewness.

[0053] In this specification, the skewness (Ssk), which indicates the degree of crystallinity, is 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 histogram of the number of pixels in the grayscale gradation of the DF-STEM image. In this specification, the term "DF-STEM image" refers to a dark-field scanning transmission electron microscope image obtained by observation using a scanning transmission electron microscope (STEM) using the dark-field (DF) method. The skewness, which indicates the degree of crystallinity of the multilayer reflective film 2, can be obtained by analyzing the histogram of the number of pixels in the grayscale gradation obtained by image analysis of the DF-STEM image of the multilayer reflective film 2. The skewness, which indicates the degree of crystallinity of the multilayer reflective film 2, will be further explained below.

[0054] FIG. 10 shows a schematic diagram of the optical system 300 of a dark-field scanning transmission electron microscope (DF-STEM). To measure the strain, which indicates the crystallinity of the multilayer reflective film 2, the multilayer reflective film 2 is first measured using 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, a scanning transmission electron microscope ARM200F (manufactured by JEOL Ltd.) is used, and the accelerating voltage of the incident electrons 302 is set to 200 kV. FIG. 10 shows a schematic diagram of 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 in the range from β1 to β2 (e.g., β1 = 68 mrad and β2 = 280 mrad) and inelastically scattered electrons 306 shown in FIG. 10 in four regions of the annular detector 310, and forming an image using signals detected in one or more of the four regions. The four regions are the right region 310a, the bottom region 310b, the left region 310c, and the top region 310d of the annular detector 310. In terms of a clock, the four regions are the 3 o'clock region 310a, the 6 o'clock region 310b, the 9 o'clock region 310c, and the 12 o'clock region 310d. To obtain a DF-STEM image, the measurement signal from at least one of the four regions of the 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.

[0055] In DF-STEM measurements, incident electrons 302 are irradiated 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.

[0056] Next, the obtained DF-STEM image is subjected to image analysis. The area for image analysis can be a square area on the cross section of the multilayer reflective coating 2. Because the skewness is a statistically obtained value, the size of the area for image analysis on the cross section of the multilayer reflective coating 2 can be any size. Specifically, the area for image analysis (referred to as the "image analysis area") can be a square area of ​​80 nm x 80 nm on the cross section of the multilayer reflective coating 2.

[0057] In image analysis of a DF-STEM image, the pixels in the image analysis region of the DF-STEM image are quantified as a grayscale ranging from 0 to 255. During image analysis, a higher grayscale value can be considered closer to white, and a lower grayscale value can be considered closer to black. The number of pixels in the image analysis region of the DF-STEM image is set to 1024 x 1024 pixels. The number of pixels at a given grayscale level in the image analysis region can be expressed as a histogram graph (distribution of grayscale and pixel count) by plotting the grayscale level on the horizontal axis.

[0058] In this embodiment, the skewness, which indicates the degree of crystallinity, is a value obtained by acquiring a DF-STEM image of the multilayer reflective film 2 and analyzing the histogram of the number of pixels in the grayscale gradation obtained by performing image analysis.

[0059] In this manner, the degree of distortion of a given multilayer reflective film 2 can be determined.

[0060] In calculating the skewness, it is preferable to statistically calculate the skewness using only data from 120 to 255 gradations, which is a region with high crystallinity. The present inventors have found that using only data from 120 to 255 gradations when calculating the skewness results in a stronger correlation between the skewness and the crystallinity of the multilayer reflective film 2. Therefore, by using only data from 120 to 255 gradations, the skewness can be considered to be a value indicating the crystallinity.

[0061] The present inventors discovered that by increasing the crystallinity in a predetermined range of the peripheral portion 22 of the multilayer reflective coating 2, the film density in the predetermined range of the peripheral portion 22 of the multilayer reflective coating 2 can be increased, and film peeling caused by pressing a conductive pin against the peripheral portion 22 of the multilayer reflective coating 2 can be suppressed, leading to the present invention. Furthermore, the present inventors discovered that, in order to increase the crystallinity of the peripheral portion 22 of the multilayer reflective coating 2, the strain index, which indicates the degree of crystallinity of the peripheral portion 22 of the multilayer reflective coating 2, can be set within a predetermined range, leading to the present invention. Therefore, by using the multilayer reflective coated substrate 90 of this embodiment, film peeling in the peripheral portion 22 of the multilayer reflective coating 2 can be suppressed when a resist film 11 having a predetermined pattern is written using a writing device.

[0062] In the multilayer reflective film coated substrate 90 of this embodiment, the difference between the maximum and minimum values ​​of distortion in the multilayer reflective film 2 within a range of 1.8 mm to 2.4 mm from the side surface 1b of the substrate 1 is preferably 0.7 or less.

[0063] FIG. 7 is a cross-sectional schematic diagram showing a portion of the peripheral portion 22 of an example of a multilayer reflective film-coated substrate 90 according to this embodiment. FIG. 7 illustrates distances D1 and D2 from the side surface 1b of the substrate 1. In the multilayer reflective film-coated substrate 90 according to this embodiment, D1 = 1.8 mm and D2 = 2.4 mm. In the multilayer reflective film-coated substrate 90 according to this embodiment, the difference between the maximum and minimum strain values ​​in the multilayer reflective film 2 within the range from distance D1 to distance D2 from the side surface 1b of the substrate 1 is preferably 0.7 or less, more preferably 0.6 or less, and even more preferably 0.5 or less. If the difference between the maximum and minimum strain values ​​in the multilayer reflective film 2 within the range from distance D1 to distance D2 from the side surface 1b of the substrate 1 falls within a predetermined range, the film stress of the multilayer reflective film 2 becomes substantially constant, thereby more effectively suppressing film peeling at the peripheral portion 22 of the multilayer reflective film-coated substrate 90.

[0064] In this specification, the portion of the multilayer reflective film 2 ranging from the distance D1 to the distance D2 from the side surface 1b of the substrate 1 may be referred to as the "end 26 of the multilayer reflective film 2." In order to find the maximum and minimum values ​​of the distortion at the end 26 of the multilayer reflective film 2, it is preferable to measure the distortion at at least three points at the end 26 of the multilayer reflective film 2.

[0065] 8, also in a reflective mask blank 100 described later, peeling of the multilayer reflective film 2 can be more effectively suppressed by keeping the difference between the maximum and minimum values ​​of the distortion in the multilayer reflective film 2 in the range from distance D1 to distance D2 from the side surface 1b of the substrate 1 (edge ​​26) within a predetermined range. The same applies to a reflective mask 200 described later.

[0066] 1 and 2, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment has a peripheral edge portion 22. Fig. 7 shows an enlarged schematic cross-sectional view of the vicinity of the peripheral edge portion 22 of the multilayer reflective film coated substrate 90 of this embodiment. In the multilayer reflective film coated substrate 90 of this embodiment, the peripheral edge portion 22 of the multilayer reflective film 2 can have a gradient thickness region 28 in which the film thickness decreases in a direction from the center toward the outside of the main surface 1a of the substrate.

[0067] FIG. 7 shows the gradient thickness region 28 of the multilayer reflective coating 2. FIG. 7 also shows the thicknesses t0, t1, and t2 of the multilayer reflective coating 2. The thickness t0 of the multilayer reflective coating 2 is the thickness of the transfer pattern formation region 24 of the multilayer reflective coating 2. The thickness t1 is 80% of the thickness t0. The thickness t2 is 20% of the thickness t0. The gradient thickness region 28 of the multilayer reflective coating 2 is at least a part of the peripheral portion 22 of the multilayer reflective coating 2, and is a region where the thickness of the multilayer reflective coating 2 ranges from the thickness t1 to the thickness t2. As shown in FIG. 7, the thickness of the peripheral portion 22 of the multilayer reflective coating 2 can be formed so that it gradually decreases toward the outside of the substrate 1. In this case, in the gradient thickness region 28 of the peripheral portion 22 of the multilayer reflective coating 2, the cross section of the multilayer reflective coating 2 has an inclined shape with a predetermined gradient. In this specification, the gradient of the gradient thickness region 28 of the multilayer reflective coating 2 can be calculated as a positive value from the distance d between the position on the first main surface 1a of the substrate 1 where the thickness of the multilayer reflective coating 2 is t1 and the position on the first main surface 1a of the substrate 1 where the thickness is t2, and the difference between the thicknesses t1 and t2. That is, the gradient of the gradient thickness region 28 of the multilayer reflective coating 2 can be expressed as (t1-t2) [nm] / d [mm].

[0068] The film thickness of the multilayer reflective film 2 in the gradient film thickness region 28 can be measured by observing the cross section of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 with a scanning transmission electron microscope.

[0069] The gradient of the gradient thickness region 28 of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of this embodiment preferably has a predetermined gradient magnitude. Specifically, the gradient of the gradient thickness region 28 of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of this embodiment is preferably 100 nm / mm or more and 400 nm / mm or less, more preferably 115 nm / mm or more and 250 nm / mm or less, and even more preferably 118 nm / mm or more and 142 nm / mm or less.

[0070] Since the gradient of the gradient thickness region 28 of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of the embodiment is within a predetermined range, the crystallinity of the peripheral portion 22 of the multilayer reflective coating 2 can be maintained and the degree of crystallinity of the peripheral portion 22 can be increased. That is, the degree of crystallinity indicated by the degree of distortion of the peripheral portion 22 of the multilayer reflective coating 2 can be made equal to or less than a predetermined value. As a result, in the manufacturing process of the reflective mask 200, when a resist film 11 having a predetermined pattern is written using a writing device, peeling of the multilayer reflective coating 2 at the peripheral portion 22 can be more effectively suppressed.

[0071] Next, a method for forming the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment will be described.

[0072] 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 multilayer film described above, for example, a 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 a Mo film having a thickness of about 3 nm is deposited using a Mo target. This constitutes one period, and 40 to 60 periods are stacked to form the multilayer reflective film 2 (the outermost layer is a Si film). The thickness of one period is preferably 7 nm. Although 60 periods requires more steps than 40 periods, the reflectivity for EUV light can be increased.

[0073] The reflectance of the multilayer reflective film 2 used in this embodiment alone is, for example, 65% 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 13.5 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.

[0074] The multilayer reflective film coated substrate 90 of this embodiment is preferably heat-treated after the formation of the multilayer reflective film 2, or after the formation of the multilayer reflective film 2 and the protective film 3, in order to adjust the stress of the multilayer reflective film 2. The heat treatment method is not particularly limited. Heat treatment devices that can be used include, for example, a heating furnace (electric furnace), a flash lamp, and laser heating. Heat treatment conditions include heating in an air atmosphere at a temperature in the range of 100 to 250°C for 10 to 60 minutes. One example of heat treatment conditions is heating in an air atmosphere at 200°C for 10 minutes.

[0075] Next, a method for forming the gradient thickness region 28 in the peripheral portion 22 of the multilayer reflective film 2 during the manufacture of the multilayer reflective film coated substrate 90 of this embodiment will be described. When forming the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment, a shielding member (also referred to as a "mask shield") is provided at a distance from the peripheral portion 22 of the substrate 1, thereby making it possible to form the gradient thickness region 28 in the peripheral portion 22 of the multilayer reflective film 2.

[0076] When forming the multilayer reflective coating 2 by sputtering, a shielding member (mask shield) is provided to prevent sputtered particles generated by the target from depositing in a portion of the substrate 1 corresponding to the peripheral edge 22. Therefore, in the peripheral edge 22, the sputtered particles are deposited at an angle oblique to the normal to the main surface 1a of the substrate 1. As a result, in the peripheral edge 22 of the multilayer reflective coating-coated substrate 90, the material of the multilayer reflective coating 2 (high refractive index layer and low refractive index layer) is deposited so as to have a film thickness distribution in which the film thickness decreases from the inside to the outside of the substrate 1. In this way, by providing a shielding member spaced apart from the peripheral edge 22, a gradient thickness region 28 of the multilayer reflective coating 2 can be formed. By providing the shielding member, the gradient thickness region 28 can be formed by a process similar to that of a conventional multilayer reflective coating 2 formation method.

[0077] When the multilayer reflective film 2 is formed by ion beam sputtering or magnetron sputtering using a shielding member (mask shield), the crystallinity (distortion) of the multilayer reflective film 2 (particularly, the crystallinity (distortion) of the multilayer reflective film 2 in the peripheral portion 22) can be controlled by adjusting the distance h between the main surface 1a of the substrate 1 and the shielding member, the shielding length L by the shielding member (the length of the area above the substrate 1 that is shielded by the shielding member from the side surface 1b of the substrate 1), the opening diameter of the shielding member (mask shield), the incident angle α of the sputtered particles of the material of the multilayer reflective film 2 (the material of the high refractive index layer and the low refractive index layer) relative to the normal to the main surface 1a of the substrate 1, and other sputtering film formation conditions. This allows for control of the film thickness and gradient angle of the multilayer reflective film 2 in the film thickness gradient region 28, and also the crystallinity (distortion) of the peripheral portion 22 of the multilayer reflective film 2 (particularly, the crystallinity (distortion) of the multilayer reflective film 2 in the peripheral portion 22). Other film formation conditions for the sputtering method include the distance between the target and the substrate 1, the discharge conditions, the film formation pressure, and the type of film formation gas, such as a rare gas. During film formation, the substrate 1 can be rotated by placing it on a rotation stage. Therefore, film formation can be performed at a predetermined incident angle α in the film thickness gradient region 28 on all sides of the rectangular substrate 1 in accordance with the rotation of the substrate 1.

[0078] In a sputtering method using a shielding member (mask shield), the incident angle α of sputtered particles of the material of the multilayer reflective film 2 (the material of the high-refractive index layer and the low-refractive index layer) relative to the normal to the main surface 1a of the substrate 1 is preferably 5 degrees or more and less than 90 degrees, more preferably 10 degrees or more and 80 degrees or less, 15 degrees or more and 70 degrees or less, or 20 degrees or more and 60 degrees or less, in order to achieve a predetermined film thickness in the film thickness gradient region 28. The distance h between the main surface 1a of the substrate 1 and the shielding member (mask shield) is preferably 0.1 mm to 1.0 mm, more preferably 0.2 mm to 0.6 mm. The shielding length L by the shielding member (mask shield) is preferably 0.5 mm to 4.0 mm, more preferably 1.0 mm to 2.0 mm. The opening diameter of the shielding member (mask shield) is preferably 145 mm to 151 mm.

[0079] FIG. 7 shows the gradient thickness region 28 included within the end 26 of the multilayer reflective coating 2, but this is not necessarily limited to this. Depending on the slope of the gradient thickness region 28, a portion of the range of the gradient thickness region 28 may be included within the end 26 of the multilayer reflective coating 2. Depending on the slope of the gradient thickness region 28, the range of the gradient thickness region 28 may include the entire end 26 of the multilayer reflective coating 2. Depending on the slope of the gradient thickness region 28, the gradient thickness region 28 and the end 26 of the multilayer reflective coating 2 may be in the same range. Depending on the slope of the gradient thickness region 28, the range of the gradient thickness region 28 and the end 26 of the multilayer reflective coating 2 may not overlap but may be different ranges. The slope shape of the gradient thickness region 28 of the multilayer reflective coating 2 from the center side to the outside of the substrate 1 may be not only a linearly sloped shape as shown in FIG. 7 but also a convexly curved slope.

[0080] 8, in a reflective mask blank 100 described later, the gradient of the gradient thickness region 28 of the multilayer reflective coating 2 has a predetermined gradient, thereby making it possible to more effectively suppress film peeling of the multilayer reflective coating 2. The same applies to a reflective mask 200 described later.

[0081] In the multilayer reflective film-coated substrate 90 of this embodiment, the crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2 is preferably lower than that in the peripheral edge portion 22. The multilayer reflective film 2 in the transfer pattern formation region 24 is required to have high smoothness and flatness in order to obtain a high reflectivity for EUV light. If the crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2 is high, problems with smoothness and flatness may occur. Therefore, if the multilayer reflective film 2 in the transfer pattern formation region 24 has a high crystallinity like the peripheral edge portion 22, this may have an adverse effect on the smoothness and flatness of the transfer pattern formation region 24. Therefore, it is preferable that the crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2 is lower than that in the peripheral edge portion 22.

[0082] Specifically, in the multilayer reflective film-coated substrate 90 of this embodiment, the strain index, which indicates the degree of crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2, is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 1.0 or more. Furthermore, the upper limit of the strain index, which indicates the degree of crystallinity, is preferably 2.4 or less, more preferably 2.0 or less. By setting the strain index, which indicates the degree of crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2, within the above-mentioned range, problems with the smoothness and flatness of the multilayer reflective film 2 in the transfer pattern formation region 24 can be avoided. The strain index does not need to be constant in the thickness direction of the multilayer reflective film 2, and can have a gradient distribution in the thickness direction. For example, to improve the surface smoothness and flatness of the multilayer reflective film 2, the crystallinity of the upper portion of the transfer pattern formation region 24 of the multilayer reflective film 2 can be made lower (the strain index is larger) than that of the lower portion.

[0083] <<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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] <<Backside conductive film 5>> The multilayer reflective film coated substrate 90 of this embodiment can have a back surface conductive film 5 for electrostatic chuck on the back surface (second main surface) of the substrate 10.

[0090] The sheet resistance required for the back surface conductive film 5 for use in an electrostatic chuck is typically 100 Ω / □ (Ω / square) or less. The back surface conductive film 5 can be formed, for example, 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 back surface conductive film 5 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back surface 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 back surface conductive film 5 is preferably Ta (tantalum), a Ta-containing alloy, or a Ta compound containing any of these elements 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.

[0091] 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.

[0092] <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. Similar to the multilayer reflective film-coated substrate 90 described above, the multilayer reflective film 2 of the reflective mask blank 100 of this embodiment has a transfer pattern formation region 24 and a peripheral portion 22 that is arranged outside the transfer pattern formation region 24. That is, the reflective mask blank 100 of this embodiment has a structure in which the absorber film 4 is provided on a thin film (such as the multilayer reflective film 2) formed on the first main surface 1a of the substrate 1 of the multilayer reflective film-coated substrate 90 described above.

[0093] The multilayer reflective film 2 of the reflective mask blank 100 of this embodiment includes a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked, similar to the above-mentioned multilayer reflective film-coated substrate 90. Furthermore, when the crystallinity of the multilayer reflective film 2 is expressed as distortion, the distortion in at least a part of the multilayer reflective film 2 within a range of 6 mm (preferably within a range of 4 mm) from the side surface 1b of the substrate 1 toward the center is within a predetermined range similar to that of the above-mentioned multilayer reflective film-coated substrate 90 of this embodiment.

[0094] Furthermore, in the reflective mask blank 100 of this embodiment, similar to the multilayer reflective film-coated substrate 90 of this embodiment described above, it is preferable that the difference between the maximum and minimum values ​​of distortion in the multilayer reflective film 2 in the range of 1.8 mm to 2.4 mm from the side surface 1b of the substrate 1 is within a predetermined range.

[0095] Furthermore, in the reflective mask blank 100 of this embodiment, similar to the multilayer reflective film-coated substrate 90 of this embodiment described above, the peripheral portion 22 of the multilayer reflective film 2 has a film thickness gradient region 28 in which the film thickness decreases in a direction from the center toward the outside of the main surface 1a of the substrate, and it is preferable that the gradient of the film thickness gradient region 28 is within a predetermined range.

[0096] Furthermore, the reflective mask blank 100 of this embodiment can have a predetermined protective film 3 on the multilayer reflective film 2 .

[0097] Next, the thin films other than the multilayer reflective film 2 included in the reflective mask blank 100 of this embodiment will be specifically described.

[0098] <<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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 8 is a schematic cross-sectional view showing a part of the peripheral edge portion 22 of an example of the reflective mask blank 100 of this embodiment. As described above, the multilayer reflective film 2 included in the reflective mask blank 100 has the same characteristics as the multilayer reflective film-coated substrate 90 described above.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] Furthermore, from the viewpoint of smoothness and flatness, the crystalline state of the absorber film 4 is preferably an amorphous or microcrystalline structure. If the surface of the absorber film 4 is not smooth or flat, the edge roughness of the absorber pattern 4a increases, which may result in poor dimensional accuracy of the pattern. 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).

[0109] <<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.

[0110] The reflective mask blank 100 of this embodiment preferably has an etching mask film 6 on the absorber film 4 .

[0111] 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).

[0112] 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.

[0113] 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.

[0114] 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.

[0115] <<Backside conductive film 5>> The reflective mask blank 100 of the embodiment can have a back surface conductive film 5 for electrostatic chucking on the back surface of the substrate 10 (the surface opposite to the side on which the multilayer reflective film 2 is formed), similar to the multilayer reflective film coated substrate 90 of the embodiment. Specific examples of the back surface conductive film 5 are the same as the back surface conductive film 5 of the multilayer reflective film coated substrate 90 of the embodiment described above.

[0116] <Reflective mask 200> This embodiment is a reflective mask 200 having a substrate 1, a multilayer reflective film 2 that is provided on the substrate 1 and reflects EUV light, and an absorber pattern 4a obtained by patterning an absorber film 4 on the multilayer reflective film 2. That is, the reflective mask 200 of this embodiment has a structure in which the absorber film 4 of the above-mentioned reflective mask blank 100 is patterned.

[0117] The multilayer reflective film 2 of the reflective mask 200 of this embodiment includes a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked, similar to the above-mentioned multilayer reflective film-coated substrate 90. Furthermore, when the crystallinity of the multilayer reflective film 2 is expressed as distortion, the distortion in at least a part of the multilayer reflective film 2 within a range of 6 mm (preferably within a range of 4 mm) from the side surface 1b of the substrate 1 toward the center is within a predetermined range similar to that of the above-mentioned multilayer reflective film-coated substrate 90 of this embodiment.

[0118] Furthermore, in the reflective mask 200 of this embodiment, similar to the multilayer reflective film-coated substrate 90 of this embodiment described above, it is preferable that the difference between the maximum and minimum values ​​of distortion in the multilayer reflective film 2 in the range of 1.8 mm to 2.4 mm from the side surface 1b of the substrate 1 is within a predetermined range.

[0119] Furthermore, in the reflective mask 200 of this embodiment, similar to the multilayer reflective film-coated substrate 90 of this embodiment described above, the peripheral portion 22 of the multilayer reflective film 2 has a film thickness gradient region 28 in which the film thickness decreases in a direction from the center toward the outside of the main surface 1a of the substrate, and it is preferable that the gradient of the film thickness gradient region 28 is within a predetermined range.

[0120] Furthermore, the reflective mask 200 of this embodiment can have a predetermined protective film 3 on the multilayer reflective film 2 .

[0121] Next, the reflective mask 200 of this embodiment will be described in detail.

[0122] 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.

[0123] 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 transfer pattern formation region 24 and a peripheral edge portion 22. 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).

[0124] 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).

[0125] 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.

[0126] After the absorber pattern 4a is formed, the resist pattern 11a is removed with a resist remover. After the resist pattern 11a is removed, a wet cleaning process using an acidic or alkaline aqueous solution is performed, thereby obtaining the reflective mask 200 of this embodiment (FIG. 6D).

[0127] 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.

[0128] The reflective mask 200 obtained in this manner has a distortion indicating the crystallinity of the peripheral portion 22 of the multilayer reflective film 2 within the above-mentioned specified range, and therefore, in the manufacturing process of the reflective mask 200, peeling of the film at the peripheral portion 22 of the multilayer reflective film 2 can be suppressed when drawing a resist film 11 of a specified pattern using a drawing device.

[0129] <Method of manufacturing a semiconductor device> The method for manufacturing a semiconductor device according to this embodiment includes a step of forming a transfer pattern on a transfer target object by performing a lithography process using an exposure apparatus, using the reflective mask 200 according to this embodiment described above.

[0130] A transfer pattern can be formed on a semiconductor 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 a semiconductor substrate using the reflective mask 200, a semiconductor device can be manufactured.

[0131] The reflective mask 200 of this embodiment can suppress film peeling at the peripheral edge 22 of the multilayer reflective film 2 when a predetermined pattern is written on the resist film 11 using a writing device in the manufacturing process of the reflective mask 200. Therefore, by using the reflective mask 200 of this embodiment, the defective rate in the manufacturing process of the reflective mask 200 can be reduced.

[0132] A method for transferring a pattern onto a semiconductor substrate 60 with a resist by using EUV light will be described with reference to FIG.

[0133] 9 shows a schematic configuration of an EUV exposure tool 50, which is an apparatus for transferring a transfer pattern onto a resist film 11 formed on a semiconductor 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.

[0134] 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 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. The EUV light generation unit 51 generates EUV light with a wavelength of, for example, 13.53 nm.

[0135] 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 substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred onto the resist film on the semiconductor substrate 60. A resist pattern can be formed on the semiconductor substrate 60 by developing the exposed resist film. An integrated circuit pattern can be formed on the semiconductor substrate 60 by etching the semiconductor substrate 60 using the resist pattern as a mask. A semiconductor device is manufactured through these and other necessary processes. [Example]

[0136] Examples and comparative examples of this embodiment will be described below. In the following description, examples 1 to 6 are examples of this embodiment, and example 7 is a comparative example.

[0137] (Preparation of multilayer reflective film coated substrate 90 of Examples 1 to 7) First, a substrate 1 having a 6025 size (152.4 mm × 152.4 mm × 6.35 mm) and having a polished first main surface 1a and second main surface was prepared as the substrate 1 for Examples 1 to 7. This substrate 1 was made of low thermal expansion glass (SiO2-TiO2-based glass). The main surface 1a of the substrate 1 was polished through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0138] 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 1a (first main surface 1a) of the substrate 1. Table 1 shows the materials and compositions of the multilayer reflective film 2 of Examples 1 to 7. In Table 1, the column "Material of multilayer reflective film 2 (low refractive index layer / high refractive index layer)" for Examples 1 to 3, 6, and 7 lists "Mo / Si," which means that the material of the low refractive index layer was Mo and the material of the high refractive index layer was Si. In Table 1, the column "Material of multilayer reflective film 2 (low refractive index layer / high refractive index layer)" for Examples 4 and 5 lists "Ru / Si," which means that the material of the low refractive index layer was Ru and the material of the high refractive index layer was Si.

[0139] The multilayer reflective films 2 in Examples 1 to 7 were formed by magnetron sputtering using a Si target and a Ru or Mo target under Kr gas. First, a high-refractive index layer of Si was formed to a thickness of 4.2 nm in contact with the main surface 1a of the substrate 1 using a Si target. Subsequently, a low-refractive index layer of Ru or Mo was formed to a thickness of 2.8 nm using a Ru or Mo target. The multilayer reflective films 2 in Examples 1 to 7 were formed to have different degrees of crystallinity. Specifically, the degree of crystallinity of the multilayer reflective films 2 was controlled by varying the film formation conditions, such as the distance between the mask shield (shielding member) and the substrate 1, the opening diameter of the mask shield (shielding member), and the pressure inside the chamber during film formation. By appropriately controlling these film formation conditions, multilayer reflective films 2 having the desired distortion at predetermined positions, as shown in Table 1, could be formed. The multilayer reflective film 2 was formed by laminating 40 periods (pairs) of one high refractive index layer and one low refractive index layer on the main surface 1a of the substrate 1, with one period consisting of one high refractive index layer and one low refractive index layer.

[0140] After the deposition of the multilayer reflective coatings 2 of Examples 1 to 7, they were subjected to a heat treatment by heating in the air at 200° C. for 10 minutes.

[0141] In this manner, the multilayer reflective film coated substrates 90 of Examples 1 to 7 were produced.

[0142] (Measurement of distortion of the edge 26 of the multilayer reflective film 2) The distortion of the edge 26 of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of Examples 1 to 7 prepared as described above was measured. The measurement method was as follows.

[0143] First, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of each of Examples 1 to 7 was observed with a dark-field scanning transmission electron microscope (DF-STEM) to obtain a DF-STEM image.

[0144] For DF-STEM observation, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of Examples 1 to 7 was cut out to a thickness of 50 nm to 100 nm so that the cross section of the 40-period stacked multilayer reflective film 2 at a position 1.8 to 2.4 mm from the side surface of the substrate 1 (i.e., the edge 26 of the multilayer reflective film 2) could be observed. This was used as sample 304. DF-STEM observation was performed at predetermined positions on the multilayer reflective film 2 of Sample 304 of Examples 1 to 7. Specifically, when the center coordinates of the 152.4 mm × 152.4 mm multilayer reflective film coated substrate 90 in a plan view were set to (0 mm, 0 mm), Sample 304 was cut out so that the cross sections at the positions (0 mm, 74.4 mm), (0 mm, 74.1 mm), and (0 mm, 73.8 mm) could be observed. These three positions correspond to positions where the distance D from the side surface of the substrate 1 was 1.8 mm, 2.1 mm, and 2.4 mm, respectively.

[0145] Next, using a DF-STEM optical system as shown in Figure 9, 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

[0146] 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) of the four regions of the annular detector 310. To obtain the DF-STEM image, a scanning transmission electron microscope ARM200F (manufactured by JEOL Ltd.) was used, and measurements were taken at an accelerating voltage of 200 kV for the incident electrons 302.

[0147] Next, the obtained DF-STEM image was analyzed. The region of the DF-STEM image of the sample 304 (multilayer reflective film 2) that was subjected to image analysis was a square region of 80 nm × 80 nm on the cross section of the multilayer reflective film 2.

[0148] 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 number of pixels at a given grayscale level in the image analysis region can be expressed as a histogram graph (distribution of grayscale and pixel count) by plotting the grayscale level on the horizontal axis.

[0149] Next, skewness was calculated by a known statistical method using only data from the distribution of gradation and pixel count in the image analysis area, where the grayscale gradation ranged from 120 to 255. The skewness obtained using data from 120 to 255 can be regarded as a value indicating the crystallinity of the multilayer reflective film 2.

[0150] The "Distortion degree at the end of the multilayer reflective film" column in Table 1 shows the distortion degree at the positions (end 26) of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of Examples 1 to 7, determined as described above, where the distance D from the side of the substrate 1 is D = 1.8 mm, 2.1 mm, and 2.4 mm.

[0151] (difference between maximum and minimum skewness values) The column "Difference between maximum and minimum distortion values" in Table 1 shows the difference between the maximum and minimum distortion values ​​at three positions (edge ​​26) where the distance D from the side of substrate 1 is D = 1.8 mm, 2.1, and 2.4 mm.

[0152] (Slope of gradient thickness region 28) The magnitude of the gradient of the gradient thickness region 28 is shown in the "Slope of gradient thickness region" column of Table 1. The measurement of the gradient of the gradient thickness region 28 was carried out as follows.

[0153] First, samples were cut out of the multilayer reflective film coated substrates 90 of Examples 1 to 7 so that the cross section of a part of the transfer pattern forming region 24 and the peripheral edge portion 22 of the multilayer reflective film 2 could be seen. Next, the film thickness t0 of the multilayer reflective film 2 in the transfer pattern forming region 24 was measured. Next, the position where the film thickness t1 was 80% of the film thickness t0 and the position where the film thickness t2 was 20% of the film thickness t0 were determined, and the distance d was measured. Note that a scanning transmission electron microscope was used to observe the cross sections of the multilayer reflective film coated substrates 90 of Examples 1 to 7. The gradient (t1-t2) [nm] / d [mm] of the gradient film thickness region 28 was calculated.

[0154] (film peeling measurement) The multilayer reflective films 2 of the mask blanks of Examples 1 to 7 were measured for peeling when a conductive pin of an electron beam lithography device was pressed against them.

[0155] First, the multilayer reflective film coated substrates 90 of Examples 1 to 7 were produced as described above.

[0156] Next, a protective film 3 containing a Ru compound was formed on the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of Examples 1 to 7. Specifically, using a RuNb target (Ru: 80 atomic %, Nb: 20 atomic %), the protective film 3 made of a RuNb film was formed on the multilayer reflective film 2 by DC magnetron sputtering in an Ar gas atmosphere. The thickness of the protective film 3 was 2.5 nm.

[0157] Next, an absorber film 4 was formed on the surface of the protective film 3, thereby producing the reflective mask blanks 100 of Examples 1 to 7.

[0158] Specifically, an absorber film 4 consisting of a laminated film of TaBN (thickness 56 nm) and TaBO (thickness 14 nm) was formed by DC magnetron sputtering. The TaBN film was formed by reactive sputtering using a TaB target in a mixed gas atmosphere of Ar gas and N2 gas. The TaBO film was formed by reactive sputtering using a TaB target in a mixed gas atmosphere of Ar gas and O2 gas. In this way, the reflective mask blanks 100 of Examples 1 to 7 were produced.

[0159] Next, the reflective mask blanks 100 of Examples 1 to 7 were set in an electron beam lithography system MBMW-101 (manufactured by JEOL Ltd.). Next, a conductive pin of the electron beam lithography system was pressed against the peripheral edge 22 of the reflective mask blank 100 for 30 seconds. The position where the conductive pin contacted the reflective mask blank 100 was 2 mm from the side surface 1a of the substrate 1 of the reflective mask blank 100. With each of the reflective mask blanks 100 of Examples 1 to 7 set in the electron beam lithography system, the pressing of the conductive pin against the peripheral edge 22 as described above was repeated 100 times for each of the reflective mask blanks 100 of Examples 1 to 7. Thereafter, the reflective mask blanks 100 of Examples 1 to 7 were removed from the electron beam lithography system and observed with an optical microscope or a scanning electron microscope to determine whether peeling had occurred in the absorber film 4, the protective film 3, and / or the multilayer reflective film 2. The "Film Peeling" column in Table 1 shows the measurement results of film peeling for the reflective mask blanks 100 of Examples 1 to 7. In the reflective mask blanks 100 of Examples 1 to 6, film peeling of the multilayer reflective film 2 did not occur. On the other hand, in the multilayer reflective mask blank 100 of Example 7, film peeling of the multilayer reflective film 2 occurred.

[0160] (Measurement of crack initiation load) To evaluate the mechanical strength of the thin film formed on the reflective mask blank 100, the crack initiation load was measured for the reflective mask blanks 100 of Examples 1 to 7 produced in the same manner as in the measurement of film peeling.

[0161] The crack initiation load can be measured as follows. First, the reflective mask blank 100 is placed on the stage of a crack initiation load measuring device. Next, an indenter is placed so as to contact the peripheral portion 22 of the multilayer reflective film 2 of the reflective mask blank 100. The indenter is configured so that a predetermined load F can be applied to press the tip of the indenter against the absorber film 4 of the reflective mask blank 100. The tip of the indenter has a shape with a predetermined radius of curvature. Next, the load applied to the indenter is increased at a predetermined speed while the stage of the crack initiation load measuring device is moved at a predetermined speed Vsub. The indenter load when a crack occurs in the absorber film 4, the protective film 3, and / or the multilayer reflective film 2 of the reflective mask blank 100 is defined as the crack initiation load. The "Crack initiation load" column in Table 1 shows the crack initiation loads of the reflective mask blanks 100 of Examples 1 to 7.

[0162] The conditions for measuring the crack initiation load are as follows. Initial load: 20mN Final load: 1000mN Indenter load increase rate: 400 mN / min Stage movement speed: 1mm / min Indenter type: Rockwell Curvature radius of the indenter tip: 20 μm

[0163] (Evaluation results) As shown in Table 1, the distortion of the multilayer reflective coating 2 of the multilayer reflective coated substrates 90 of Examples 1 and 3 to 6 was 1.3 or less at all three positions on the peripheral edge 22. The distortion of the multilayer reflective coating 2 of the multilayer reflective coated substrate 90 of Example 2 was 1.3 or less at two positions on the peripheral edge 22. As a result, no film peeling was observed in the measurements of the reflective mask blanks 100 of Examples 1 to 6. Therefore, it is believed that when a reflective mask 200 is manufactured using the reflective mask blanks 100 of Examples 1 to 6, it is possible to avoid fatal film peeling that can occur during the manufacturing process of the reflective mask 200.

[0164] In contrast, the distortion of the multilayer reflective coating 2 of the multilayer reflective film coated substrate 90 of Example 7 exceeded 1.3 at all three positions in the peripheral edge 22. As a result, film peeling was found in the measurement of film peeling of the reflective mask blank 100 of Example 7. Therefore, when the reflective mask 200 is manufactured using the reflective mask blank 100 of Example 7, it may be impossible to avoid fatal film peeling that can occur during the manufacturing process of the reflective mask 200.

[0165] As shown in Table 1, the difference between the maximum and minimum values ​​of the distortion at the edge 26 of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of Examples 1 to 5 was 0.60 or less. On the other hand, the difference between the maximum and minimum values ​​of the distortion at the edge 26 of the multilayer reflective coating 2 of the multilayer reflective coating coated substrate 90 of Example 6 was 0.73. For this reason, it is considered that the crack initiation load of the reflective mask blank 100 of Example 6 was lower than the crack initiation load of the reflective mask blank 100 of Examples 1 to 5. Therefore, it is considered that Examples 1 to 5 can more effectively suppress film peeling at the peripheral edge 22 of the multilayer reflective coating coated substrate 90 compared to Example 6.

[0166] [Table 1] [Explanation of symbols]

[0167] 1 board 1a Main surface (1st main surface) 1b side 1c Chamfered surface 2 Multilayer reflective film 3 Protective film 4. Absorber membrane 4a Absorber pattern 5 Backside conductive film 6 Etching mask film 11 Resist film 11a Resist pattern 22 Periphery 24 Transcription patterning region 26 End 28 Film Thickness Gradient Region 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 Semiconductor substrate 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 multilayer reflective film-coated substrate including a substrate and a multilayer reflective film provided on the substrate, the multilayer reflective film includes a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated, A substrate with a multilayer reflective film, characterized in that, when the crystallinity of the multilayer reflective film is expressed as a distortion, the distortion of at least a portion of the multilayer reflective film within a range of 6 mm from the side of the substrate toward the center is 1.3 or less.

2. 2. The multilayer reflective film coated substrate according to claim 1, wherein the difference between the maximum and minimum distortion values ​​in the multilayer reflective film within a range of 1.8 mm to 2.4 mm from the side surface of the substrate is 0.7 or less.

3. the multilayer reflective film has a peripheral portion, the peripheral portion of the multilayer reflective film has a thickness gradient region in which the thickness decreases along a direction from a center side to an outer side of the main surface of the substrate, 3. The multilayer reflective film coated substrate according to claim 1, wherein the gradient of the film thickness gradient region is 100 nm / mm or more and 400 nm / mm or less.

4. 3. The multilayer reflective film coated substrate according to claim 1, further comprising a protective film on the multilayer reflective film.

5. A reflective mask blank comprising: a substrate; a multilayer reflective film provided on the substrate and reflecting EUV light; and an absorber film on the multilayer reflective film, the multilayer reflective film includes a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated, A reflective mask blank, characterized in that, when the crystallinity of the multilayer reflective film is expressed as a distortion, the distortion of at least a portion of the multilayer reflective film within a range of 6 mm from the side surface of the substrate toward the center is 1.3 or less.

6. 6. The reflective mask blank according to claim 5, wherein the difference between the maximum and minimum distortion values ​​in the multilayer reflective film within a range of 1.8 mm to 2.4 mm from the side surface of the substrate is 0.7 or less.

7. the multilayer reflective film has a peripheral portion, the peripheral portion of the multilayer reflective film has a thickness gradient region in which the thickness decreases along a direction from a center side to an outer side of the main surface of the substrate, 7. The reflective mask blank according to claim 5, wherein the gradient of the thickness gradient region is 100 nm / mm or more and 400 nm / mm or less.

8. 7. The reflective mask blank according to claim 5, further comprising a protective film on the multilayer reflective film.

9. A reflective mask including a substrate, a multilayer reflective film provided on the substrate and reflecting EUV light, and an absorber pattern in which an absorber film is patterned on the multilayer reflective film, the multilayer reflective film includes a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated, A reflective mask characterized in that, when the crystallinity of the multilayer reflective film is expressed as a distortion, the distortion of at least a portion of the multilayer reflective film within a range of 6 mm from the side of the substrate toward the center is 1.3 or less.

10. 10. The reflective mask according to claim 9, wherein the difference between the maximum and minimum values ​​of distortion in the multilayer reflective film within a range of 1.8 mm to 2.4 mm from the side surface of the substrate is 0.7 or less.

11. the multilayer reflective film has a peripheral portion, the peripheral portion of the multilayer reflective film has a thickness gradient region in which the thickness decreases along a direction from a center side to an outer side of the main surface of the substrate, 11. The reflective mask according to claim 9, wherein the gradient of the gradient film thickness region is 100 nm / mm or more and 400 nm / mm or less.

12. 11. The reflective mask according to claim 9, further comprising a protective film on the multilayer reflective film.

13. 11. A method for manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus with the reflective mask according to claim 9, to form a transfer pattern on a transfer target.

Images