Substrate provided with multilayer reflective film, reflective mask blank, method for manufacturing reflective mask blank, and reflective mask

Abstract

Provided is a substrate provided with a multilayer reflective film that has excellent reproducibility of measurement coordinates based on reference marks.　A substrate provided with a multilayer reflective film comprising a substrate and a multilayer reflective film, wherein the surface of the multilayer reflective film has recesses that serve as reference marks, the inclination angle of the recesses is greater than 45.0° and not greater than 80.0°, the bottom surfaces of the recesses each have a protrusion, and the ratio D / H is 80.0 or less, where D is the average depth from the opening positions of the recesses to the surfaces of the protrusions and H is the average height of the protrusions.

Description

Multilayer reflective substrate, reflective mask blank, method for manufacturing a reflective mask blank, reflective mask

[0001] The present invention relates to a reflective mask used in EUV (Extreme Ultra Violet) exposure, which is used in the exposure process of semiconductor manufacturing; a reflective mask blank, which is the original plate for the reflective mask; and a multilayer reflective film substrate used in the manufacture of the reflective mask blank.

[0002] In recent years, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been investigated for further miniaturization of semiconductor devices.

[0003] In EUV lithography, reflective optics and reflective masks are used due to the characteristics of EUV light. In a reflective mask, a multilayer reflective film that reflects EUV light is formed on the substrate, and an absorbent film that absorbs EUV light is patterned on the multilayer reflective film.

[0004] EUV light incident on the reflective mask from the illumination optical system of the exposure apparatus is reflected in areas without the absorber film (apertures) and absorbed in areas with the absorber film (non-apertures). As a result, the mask pattern is transferred as a resist pattern onto the wafer through the reduction projection optical system of the exposure apparatus, and subsequent processing is carried out.

[0005] In multilayer reflective films that reflect EUV light, defects may occur during the manufacturing process. When defects occur in a multilayer reflective film, the reflectivity of EUV light changes, which can cause problems in pattern transfer. To form a mask pattern while avoiding defects in the multilayer reflective film, it is necessary to accurately identify the location of these defects.

[0006] One method for identifying the location of the above-mentioned defects is to form a reference mark on a reflective mask blank. For example, Patent Document 1 below discloses a substrate with a multilayer reflective film having a reference mark having a predetermined shape.

[0007] Japanese Patent Publication No. 2013-179270

[0008] In recent years, with the further miniaturization of circuit patterns formed on wafers and the like, there has been a demand for improved accuracy in identifying defect locations in multilayer reflective films. Improving the accuracy of defect location identification requires excellent reproducibility of coordinates measured based on the above-mentioned reference marks. When the present inventors examined a substrate with a multilayer reflective film on which the reference marks described in Patent Document 1 are formed, they found that there is room for improvement in the reproducibility of coordinates measured based on the reference marks.

[0009] This invention has been made in view of the above problems, and aims to provide a substrate with a multilayer reflective film that exhibits excellent reproducibility of measurement coordinates based on reference marks. Furthermore, this invention also aims to provide a reflective mask blank, a method for manufacturing a reflective mask blank, and a reflective mask.

[0010] As a result of diligent research into the above-mentioned problems, the inventors of the present invention discovered that the reproducibility of measurement accuracy can be improved by adjusting the inclination angle of the recess that forms the reference mark, and by having a protrusion of a predetermined shape in the recess, thus completing the present invention.

[0011] In other words, the inventors have found that the above problem can be solved by the following configurations: [1] A multilayer reflective substrate comprising a substrate and a multilayer reflective film, wherein a recess forming a reference mark is arranged on the surface of the multilayer reflective film, the inclination angle of the recess is greater than 45.0° and less than or equal to 80.0°, the bottom surface of the recess has a convex portion, and the D / H ratio, which is the ratio of the average depth D from the opening position of the recess to the surface of the convex portion to the average height H of the convex portion, is 80.0 or less. [2] The multilayer reflective substrate according to [1], wherein the D / H ratio is 1.0 to 40.0. [3] The multilayer reflective substrate according to [1] or [2], wherein the maximum depth of the recess is 91.5 to 150.0 nm. [4] The multilayer reflective substrate according to any one of [1] to [3], wherein the average height H is 2.0 to 50.0 nm. [5] A substrate with a multilayer reflective film according to any one of [1] to [4], wherein the shape of the reference mark when viewed from the normal direction of the surface of the multilayer reflective film is cross-shaped. [6] A substrate with a multilayer reflective film according to any one of [1] to [5], wherein it has three or more of the reference marks. [7] A substrate with a multilayer reflective film according to any one of [1] to [6], wherein the reference marks are arranged in an area other than the exposure area. [8] A reflective mask blank having a substrate with a multilayer reflective film according to any one of [1] to [7] and an absorber film arranged on the opposite side of the multilayer reflective film from the substrate side. [9] A reflective mask blank according to [8], wherein the absorber film contains one or more metallic elements selected from the group consisting of chromium, tantalum, niobium, iridium, cobalt, nickel, copper, tin, platinum, palladium, gold, and ruthenium.

[10] A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank described in [8] or [9].

[11] A method for manufacturing a reflective mask blank as described in [8] or [9], comprising: forming a multilayer reflective film on one surface of a substrate; forming the recesses that make up the reference marks on the multilayer reflective film by a focused ion beam method or a dry etching method; and forming the absorber film on the multilayer reflective film on which the reference marks have been formed by a sputtering method.

[0012] According to the present invention, a substrate with a multilayer reflective film that exhibits excellent reproducibility of measurement coordinates based on reference marks can be provided. Furthermore, according to the present invention, a reflective mask blank, a method for manufacturing a reflective mask blank, and a reflective mask can also be provided.

[0013] This is a top view showing an example of an embodiment of the multilayer reflective film substrate of the present invention. This is a cross-section A-A of the multilayer reflective film substrate shown in Figure 1. This is an enlarged view of the recess in the cross-section A-A shown in Figure 2. This shows examples of the shape of the recess when the shape of the recess differs in the cross-section A-A of the embodiments shown in Figures 1 and 2. This shows examples of the shape of the recess when the shape of the recess differs in the cross-section A-A of the embodiments shown in Figures 1 and 2. This is the shape profile corresponding to the recess in the embodiment shown in Figure 3. This is a schematic cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. This is a schematic cross-sectional view showing an example of a method for manufacturing a reflective mask.

[0014] The present invention will now be described in detail. The following descriptions of constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0015] The meaning of each description in this specification is as follows. In this specification, a numerical range expressed using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. In this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, tin, hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum may be represented by their corresponding element symbols (B, C, N, O, Si, Ti, Cr, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Sn, Hf, Ta, W, Re, Os, Ir, and Pt, etc.).

[0016] In the drawings of this specification, identical or corresponding components may be denoted by the same or corresponding reference numerals, and their descriptions may be omitted. Furthermore, the dimensional ratios in the drawings of this specification do not necessarily represent the ratios of actual dimensions.

[0017] <Multilayer Reflective Film Substrate> The multilayer reflective film substrate of the present invention comprises a substrate and a multilayer reflective film. In the multilayer reflective film substrate of the present invention, recesses forming reference marks are arranged on the surface of the multilayer reflective film. Furthermore, the inclination angle of the recesses is greater than 45.0° and less than or equal to 80.0°, and the bottom surface of the recesses has a protrusion, and the D / H ratio, which is the ratio of the average depth D from the opening position of the recess to the surface of the protrusion to the average height H of the protrusion, is 80.0 or less. The multilayer reflective film substrate of the present invention will be described with reference to the drawings.

[0018] Figure 1 is a top view showing an example of an embodiment of the multilayer reflective film substrate of the present invention. The top view shown in Figure 1 is a view of the multilayer reflective film substrate 10 as seen from the multilayer reflective film 14 side. Four recesses 20 forming reference marks are formed on the surface of the multilayer reflective film 14. The shape of the recesses 20 forming reference marks is a cross shape when viewed from the direction normal to the multilayer reflective film 14 of the multilayer reflective film substrate 10. The area enclosed by the dashed line in Figure 1 indicates the exposure area. The four recesses 20 are located in the area other than the exposure area. A substrate (not shown) is placed on the back side of the multilayer reflective film 14.

[0019] Figure 2 is a cross-section along line A-A of the multilayer reflective substrate shown in Figure 1. The multilayer reflective substrate 10 shown in Figure 2 comprises a substrate 12 and a multilayer reflective film 14. A recess 20 is formed in the multilayer reflective film 14. As shown in Figure 2, the recess 20 is formed from the surface of the multilayer reflective film 14 opposite to the substrate 12, extending toward the substrate 12. Note that the recess 20 shown in Figure 2 is exaggerated and shown as larger than the recess 20 shown in Figure 1.

[0020] Figure 3 is an enlarged view of the recess 20 in the A-A cross-section shown in Figure 2. In the A-A cross-section of the recess 20 shown in Figure 3, the recess 20 has a bottom surface that is below the plane of the paper in Figure 3, and side surfaces that are in the left-right direction of the paper in Figure 3. The bottom surface of the recess 20 also has a protrusion 24. In the multilayer reflective substrate of the present invention, the inclination angle of the recess (angle α in Figure 3), which is the angle between the side surface and the bottom surface, is greater than 45.0° and less than or equal to 80.0°. In the multilayer reflective substrate 10 of the present invention, the D / H ratio, which is the ratio of the average depth D (depth D1 in Figure 3) from the opening position of the recess 20 (dashed line at the top of the paper in Figure 3) to the surface of the protrusion 24 to the average height H (height H1 in Figure 3) of the protrusion 24, is 80.0 or less. Here, the reading of the reference mark on the multilayer reflective substrate 10 may be performed, for example, with inspection light (more specifically, EUV light). In the multilayer reflective substrate 10 of the present invention, the inclination angle of the recess 20 is within the above range, which causes the inspection light to scatter at the edge portion of the protrusion 24, resulting in better contrast and easier identification by inspection light. Furthermore, since the protrusion 24 is located on the bottom surface of the recess 20 and the above D / H ratio is within a predetermined range, the reflection of the inspection light is more likely to occur at the bottom surface, resulting in an inspection light image with higher contrast. Due to the above mechanism, the multilayer reflective substrate of the present invention is considered to have excellent reproducibility of measurement coordinates based on reference marks.

[0021] The recess 20 may have a shape other than that shown in Figure 3. For example, the shape of the recess that forms a reference mark placed on the multilayer reflective film substrate of the present invention may be as shown in Figure 4. Figure 4 shows an example of the shape of the recess when the shape of the recess differs in the A-A cross section in the embodiments shown in Figures 1 and 2. The recess 20a shown in Figure 4 has a bottom surface that is below the plane of the paper in Figure 4 and a side surface in the left-right direction of the paper in Figure 4. The bottom surface of the recess 20a also has a protrusion 24a. In the recess 20a shown in Figure 4, the shape of the bottom surface is different from that of the recess 20 shown in Figure 3. Otherwise, the recess 20a shown in Figure 4 is the same as the recess 20 shown in Figure 3. Specifically, in the recess 20a of the embodiment shown in Figure 4, the inclination angle of the recess (angle α2 in Figure 4), which is the angle between the side surface and the bottom surface, is greater than 45° and less than or equal to 80°. Furthermore, the D / H ratio, which is the ratio of the average depth D (depth D2 in Figure 4) from the opening position of the recess 20a (dashed line at the top of the paper in Figure 4) to the surface of the protrusion 24a to the average height H (height H2 in Figure 4) of the protrusion 24a, is 80 or less.

[0022] Furthermore, the shape of the recess that forms a reference mark placed on the substrate with the multilayer reflective film of the present invention may be as shown in Figure 5. Figure 5 shows an example of the shape of the recess when the shape of the recess differs in the A-A cross section in the embodiments shown in Figures 1 and 2. The recess 20b shown in Figure 5 has a bottom surface that is below the plane of the paper in Figure 5 and side surfaces in the left-right direction of the paper in Figure 5. The bottom surface of the recess 20b also has a protrusion 24b. Compared with the recess 20 shown in Figure 3, the recess 20b shown in Figure 5 has a different shape for the bottom surface and a different shape for the protrusion 24b. Otherwise, the recess 20b shown in Figure 5 is the same as the recess 20 shown in Figure 3. Specifically, in the recess 20b of the embodiment shown in Figure 5, the inclination angle of the recess (angle α3 in Figure 5), which is the angle between the side surface and the bottom surface, is greater than 45° and less than or equal to 80°. Furthermore, the D / H ratio, which is the ratio of the average depth D (depth D3 in Figure 5) from the opening position of the recess 20b (dashed line at the top of the paper in Figure 5) to the surface of the protrusion 24b to the average height H (height H3 in Figure 5) of the protrusion 24b, is 80 or less.

[0023] The multilayer reflective film substrate of the present invention will be described in detail below.

[0024] [Substrate] The substrate with a multilayer reflective film of the present invention includes a substrate. It is preferable that the substrate has a small coefficient of thermal expansion. When the coefficient of thermal expansion of the substrate is small, for example, it is possible to suppress the occurrence of distortion in the absorber film pattern due to heat during exposure with EUV light. The coefficient of thermal expansion of the substrate is preferably 0 ± 1.0 × 10 －７ / °C at 20°C, and more preferably 0 ± 0.3 × 10 －７ / °C. Examples of materials with a small coefficient of thermal expansion include SiO ２ -TiO ２ -based glass, etc., but are not limited thereto, and substrates such as crystallized glass with β-quartz solid solution precipitated, quartz glass, metallic silicon, and metals can also be used. For SiO ２ -TiO ２ -based glass, it is preferable to use quartz glass containing 90 to 95% by mass of SiO ２ and 5 to 10% by mass of TiO ２ . When the content of TiO ２ is 5 to 10% by mass, the linear expansion coefficient near room temperature is substantially zero, and almost no dimensional change occurs near room temperature. Note that the SiO ２ -TiO ２ -based glass may contain trace components other than SiO ２ and TiO ２ .

[0025] The surface of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first main surface") preferably has high surface smoothness. The surface smoothness of the first main surface can be evaluated by its surface roughness. The surface roughness of the first main surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. The surface roughness can be measured with an atomic force microscope, and the surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to a predetermined flatness in order to improve the pattern transfer accuracy and positional accuracy of the reflective mask obtained using the reflective mask blank of the present invention, which will be described later. In a predetermined area of ​​the first main surface (for example, an area of ​​132 mm × 132 mm), the flatness of the substrate is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured with a flatness measuring instrument manufactured by Fujinon Co., Ltd. The size and thickness of the substrate are appropriately determined by the design values ​​of the mask, etc. For example, the external dimensions may be 6 inches (152 mm) square, and the thickness 0.25 inches (6.3 mm). The substrate is often rectangular or square. Furthermore, it is preferable that the substrate has high rigidity in order to prevent deformation due to film stress of the film (multilayer reflective film, absorber film, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0026] [Multilayer Reflective Film] The substrate with a multilayer reflective film of the present invention comprises a multilayer reflective film. Preferably, the multilayer reflective film is a multilayer reflective film that reflects EUV light. The multilayer reflective film is not particularly limited as long as it has the desired properties as, for example, a reflective film for an EUV mask blank. Preferably, the multilayer reflective film has a high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0027] Since multilayer reflective films can achieve high reflectivity of EUV light, a multilayer reflective film is usually used in which a high refractive index layer exhibiting a high refractive index for EUV light and a low refractive index layer exhibiting a low refractive index for EUV light are alternately stacked multiple times. The multilayer reflective film may be stacked in multiple periods, with one period consisting of a stacked structure in which the high refractive index layer and the low refractive index layer are stacked in this order from the substrate side, or it may be stacked in multiple periods, with one period consisting of a stacked structure in which the low refractive index layer and the high refractive index layer are stacked in this order. A layer containing Si can be used as the high refractive index layer. As a material containing Si, in addition to pure Si, a Si compound containing Si and one or more elements selected from the group consisting of B, C, N, and O can be used. By using a high refractive index layer containing Si, a reflective mask with excellent reflectivity of EUV light can be obtained. As a low refractive index layer, a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof, can be used. Si is widely used for the high refractive index layer, and Mo is widely used for the low refractive index layer. In other words, Mo / Si multilayer reflective coatings are the most common. However, multilayer reflective coatings are not limited to this, and Ru / Si multilayer reflective coatings, Mo / Be multilayer reflective coatings, Mo compound / Si compound multilayer reflective coatings, Si / Mo / Ru multilayer reflective coatings, Si / Mo / Ru / Mo multilayer reflective coatings, Si / Ru / Mo multilayer reflective coatings, and Si / Ru / Mo / Ru multilayer reflective coatings can also be used.

[0028] The film thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layer can be appropriately selected according to the film material used and the required EUV light reflectance of the reflective layer. Taking a Mo / Si multilayer reflective film as an example, to obtain a multilayer reflective film with a maximum EUV light reflectance of 60% or more, a Mo film with a film thickness of 2.3 ± 0.1 nm and a Si film with a film thickness of 4.5 ± 0.1 nm should be stacked so that the number of repeating units is between 30 and 60. It is preferable that the multilayer reflective film has a reflectance of 60% or more for EUV light with an incident angle θ of 6°. More preferably, the above reflectance is 65% or more. The film thickness of the multilayer reflective film is often 200 nm or more, and preferably 250 nm or more. Also, the film thickness of the multilayer reflective film is often 450 nm or less, and preferably 350 nm or less.

[0029] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when fabricating a multilayer reflective film using ion beam sputtering, ion particles are supplied from an ion source to a target made of a high refractive index material and a target made of a low refractive index material. When the multilayer reflective film is a Mo / Si multilayer reflective film, for example, using ion beam sputtering, first a Si layer of a predetermined thickness is deposited on the substrate using a Si target. Then, a Mo layer of a predetermined thickness is deposited using a Mo target. These Si and Mo layers are stacked for, for example, 30 to 60 periods (preferably 40 to 50 periods) to form a Mo / Si multilayer reflective film.

[0030] Furthermore, as described above, recesses that form reference marks are arranged on the surface of the multilayer reflective film of the present invention. The recesses that form reference marks will be described in detail below.

[0031] It is preferable that three or more recesses forming reference marks are arranged. It is also preferable that the three or more recesses forming reference marks are formed such that their centers do not lie on the same straight line on the surface of the multilayer reflective film. Furthermore, it is also preferable that the reference marks be placed in areas other than the exposure area. The exposure area is, for example, if the shape of the substrate is 152.0 mm square, an area of ​​132 × 104 mm located at the center in the in-plane direction of the substrate. The shape of the reference marks when viewed from the normal direction of the surface of the multilayer reflective film (hereinafter also referred to as the "planar shape of the reference marks" or "planar shape of the recesses") is not particularly limited, but may be a cross shape as shown in Figure 1, a rectangle, a square, or a circle. Furthermore, the planar shape of the reference marks may be T-shaped or L-shaped. A cross shape refers to a shape formed by combining two rectangles such that their longitudinal directions are perpendicular and the sides of the two rectangles intersect. Furthermore, a T-shape is a shape formed by combining two rectangles such that their longitudinal directions are perpendicular, the shorter side of one rectangle overlaps with the longer side of the other rectangle, and the longer side of one rectangle does not overlap with the shorter side of the other rectangle. Similarly, an L-shape is a shape formed by combining two rectangles such that their longitudinal directions are perpendicular, the longer side of one rectangle overlaps with the shorter side of the other rectangle, and the shorter side of one rectangle overlaps with the longer side of the other rectangle. It is preferable that the reference marks be used as reference positions for identifying the location of defects present in the multilayer reflective film. By identifying the relative position of the defect based on the reference marks, a mask pattern can be formed while avoiding that defect.

[0032] The planar shape of the reference mark can be identified by observing it with a scanning electron microscope (SEM: Scanning Electron Microscope) from the normal direction of the surface of the multilayer reflective film. When the planar shape of the reference mark is a cross shape, a T shape or an L shape, the short side (i.e., width) of the rectangle forming the cross shape, T shape or L shape is preferably 1.5 μm or less, more preferably 1.2 μm or less. Also, the short side of the rectangle is preferably 0.10 μm or more, more preferably 0.12 μm or more. Also, the maximum length in the planar shape of the reference mark (for example, the length of the long side of the rectangle forming the cross shape) is often 40 μm or less, preferably 35 μm or less, more preferably 32 μm or less. Also, the maximum length in the planar shape of the reference mark is often 0.10 μm or more.

[0033] In the substrate with the multilayer reflective film of the present invention, the shape of the recess forming the reference mark satisfies the above-mentioned requirements, and the shape of the recess forming the reference mark is obtained by the following method. First, prepare a substrate with a multilayer reflective film in which a recess forming a reference mark is arranged. Next, identify the position where the recess is arranged in the substrate with the multilayer reflective film.Next, at the identified position of the recess, measurement is performed using an atomic force microscope (AFM: Atomic Force Microscope). In this specification, the AFM uses the AFM (L-trace II) manufactured by Hitachi High-Tech Corporation. The detailed measurement conditions are as follows. ・ Cantilever: SI-DF40 ・ Measurement mode: DFM ・ Scanning speed: 0.2 Hz The measurement by the AFM is performed in either one of the following measurement regions, region 1 and region 2. Region 1: A linear region at the position of half of the length of the planar shape in the longitudinal direction, which is the direction in which the planar shape of the recess extends the longest, and orthogonal to the longitudinal direction. Region 2: A linear region at the position of 1 / 4 of the length of the planar shape in the longitudinal direction, which is the direction in which the planar shape of the recess extends the longest, and orthogonal to the longitudinal direction.

[0034] For example, if the planar shape of the recess is rectangular, square, or L-shaped, AFM measurement is performed in area 1. If the planar shape of the recess is cross-shaped or T-shaped, AFM measurement is performed in area 2. However, if the shorter side of a rectangle with a longer side perpendicular to the longitudinal direction overlaps with area 2, the measurement is performed using the following area 2A as the measurement area. Area 2A: A linear area perpendicular to the longitudinal direction, located at 3 / 4 of the length of the planar shape in the longitudinal direction, which is the direction in which the planar shape of the recess extends the longest.

[0035] When AFM measurements are performed in the above measurement area, a shape profile is obtained in which the horizontal axis represents the position in a direction perpendicular to the longitudinal direction and the vertical axis represents the depth. In the above shape profile, the relationship between the position in a direction perpendicular to the longitudinal direction and the depth, corresponding to the shape of the recess shown in Figure 3, is obtained. By analyzing the above shape profile, the average height H of the convex portion and the average depth D from the opening position of the recess to the convex portion are calculated. The method for calculating the average height H and average depth D will be explained below with reference to a specific example of a shape profile.

[0036] Figure 6 shows the shape profile corresponding to the recess 20 in the embodiment shown in FIG. 3. In the shape profile shown in FIG. 6, the relationship between the position in the direction orthogonal to the longitudinal direction (x, unit: nm) and the depth (d, unit: nm) is illustrated. In the shape profile shown in FIG. 6, the portion between position Xa and position Xd is a recess, and the depth is calculated with reference to the depths (opening positions) at position Xa and position Xd (reference depth position Db). Also, in the shape profile shown in FIG. 6, at position Xb and position Xc, the maximum depth position Dmax, which is the maximum depth from the reference depth position Db, is shown. Next, at each measurement point between position Xb and position Xc, the absolute value of the value obtained by subtracting the measured value of the depth in the shape profile from the maximum depth position Dmax is calculated, and the arithmetic mean value thereof is defined as the average height H (height H1 in FIG. 6). Also, the absolute value of the value obtained by subtracting the maximum depth position Dmax from the reference depth position Db is defined as the maximum depth (maximum depth Dt in FIG. 6). Then, the value obtained by subtracting the calculated average height H from the calculated maximum depth is defined as the average depth D (depth D1 in FIG. 6). By the above procedure, the average height H and the average depth D are calculated, and the above-described D / H ratio can be calculated.

[0037] In FIG. 6, when the depths at position Xb and position Xc are different, the one with the larger depth from the reference depth position Db is defined as the maximum depth position Dmax. Also, the position Xa for calculating the reference depth position Db is the position at which the slope on the shape profile first becomes negative when the value of position x is increased in the direction indicating the maximum depth position Dmax from the left side of the drawing. The position Xd for calculating the reference depth position Db is the position at which the slope on the shape profile first becomes positive when the value of position x is decreased in the direction indicating the maximum depth position Dmax from the right side of the drawing. When the depth values at position Xa and position Xd are different, the reference depth position Db is the arithmetic mean value of the depth at position Xa and the depth at position Xd.

[0038] Alternatively, the shape profile may be obtained by performing measurements using AFM in two dimensions to obtain a two-dimensional mapping, and then extracting the shape profile at the position corresponding to the measurement area in a linear fashion from the obtained two-dimensional mapping.

[0039] As described above, in the substrate with a multilayer reflective film of the present invention, the D / H ratio is 80.0 or less, and in terms of superior reproducibility of measurement coordinates, it is preferably 40.0 or less, more preferably 20.0 or less, even more preferably 10.0 or less, particularly preferably 5.0 or less, and most preferably 3.0 or less. Furthermore, the lower limit of the above D / H ratio is not particularly limited and may be 0, often 0.5 or more, and may also be 1.0 or more.

[0040] Furthermore, the average height H is preferably 1.5 nm or more, more preferably 2.0 nm or more, even more preferably 5.0 nm or more, particularly preferably 10.0 nm or more, and most preferably 30.0 nm or more. The average height H is often less than or equal to the average depth D described later, preferably 60.0 nm or less, and more preferably 50.0 nm or less. The average depth D is often 0.0 nm or more, preferably 30.0 nm or more, more preferably 50.0 nm or more, and even more preferably 70.0 nm or more. The average depth D is often 200.0 nm or less, preferably 150.0 nm or less, and more preferably 100.0 nm or less.

[0041] The maximum depth is preferably 50.0 nm or more, more preferably 70.0 nm or more, even more preferably 90.0 nm or more, and particularly preferably 91.5 nm or more. Furthermore, the maximum depth is often 300.0 nm or less, preferably 200.0 nm or less, and more preferably 150.0 nm or less.

[0042] Furthermore, the inclination angle of the recess, which is the angle between the side surface and the bottom surface of the recess described above, is determined by the following method. First, the shape profile is obtained using the method described above. The method for calculating the inclination angle will be explained below with reference to Figure 6. Positions Xa, Xb, Xc, and Xd are as described above. In the shape profile shown in Figure 6, a straight line is drawn connecting positions Xb and Xc to indicate the bottom surface. Furthermore, a first approximate straight line is found and drawn between positions Xa and Xb that best fits the portion of the shape profile that is linear. The first approximate straight line can be found, for example, by using the least squares method on the shape profile. The angle between the straight line indicating the bottom surface and the first approximate straight line is determined. Similarly, a second approximate straight line is drawn between positions Xc and Xd, and the angle between the straight line indicating the bottom surface and the second approximate curve is determined. The arithmetic mean of the two angles found above is defined as the inclination angle of the recess in this specification.

[0043] The inclination angle of the recess is greater than 45.0°, may be 47.0° or more, or 50.0° or more. Furthermore, the inclination angle of the recess is 80.0° or less, preferably 70.0° or less, and more preferably 60.0° or less.

[0044] The substrate with a multilayer reflective film of the present invention can be manufactured, for example, by forming the multilayer reflective film using the procedure described above, and then processing the multilayer reflective film. Examples of methods for processing the multilayer reflective film include the focused ion beam (FIB) method and the dry etching method. More specifically, a method for processing the multilayer reflective film by the FIB method involves first uniformly irradiating an ion beam to form a recess of the desired shape, thereby creating a recess with a flat bottom surface. Then, the ion beam is irradiated only near the periphery of the recess to cut the periphery of the recess. More specifically, a method for processing the multilayer reflective film by the dry etching method involves first preparing a mask in which only the periphery of the recess of the desired shape is open, and then processing only the periphery of the recess by dry etching. Then, the mask formed inside the periphery of the recess is removed, and the entire interior of the recess is processed by dry etching.

[0045] The substrate with the multilayer reflective film of the present invention may have configurations other than those described above. For example, it may have a conductive film as detailed in the section on the reflective mask blank of the present invention. The conductive film is located on the side of the substrate opposite to the multilayer reflective film side (the second main surface side).

[0046] The multilayer reflective film substrate of the present invention is suitably used in the manufacture of the reflective mask blank of the present invention, as described later.

[0047] <Reflective Mask Blank> The reflective mask blank of the present invention comprises the multilayer reflective film substrate of the present invention described above, and an absorbent film disposed on the side of the multilayer reflective film opposite to the substrate side. The reflective mask blank of the present invention will be described with reference to the drawings.

[0048] Figure 7 is a schematic cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. The schematic cross-sectional view shown in Figure 7 is a cross-sectional view at the position where the recesses forming the reference marks of the multilayer reflective film substrate of the present invention described above are formed. The reflective mask blank 30 of the present invention shown in Figure 7 has a substrate 12, a multilayer reflective film 14, and an absorber film 18 in this order. The multilayer reflective film 14 has recesses forming reference marks that satisfy the above requirements, and the absorber film 18 has transfer recesses 32 formed along the shape of the recesses. The reflective mask blank of the present invention has excellent reproducibility of measurement coordinates based on the reference marks of the multilayer reflective film substrate of the present invention, and it is easy to accurately identify the defect positions of the multilayer reflective film, so it is easy to form a desired resist pattern on the wafer in a reflective mask formed using the reflective mask blank.

[0049] The configuration of the reflective mask blank of the present invention and configurations that the reflective mask blank of the present invention may have will be described below. Note that the substrate and multilayer reflective film of the reflective mask blank of the present invention are the same as the configuration of the substrate with the multilayer reflective film of the present invention described above, so their description will be omitted.

[0050] [Absorber Film] The reflective mask blank of the present invention has an absorber film disposed on the side of the multilayer reflective film opposite to the substrate side. When the absorber film is patterned, it is required that the contrast between the EUV light reflected by the multilayer reflective film and the EUV light absorbed by the absorber film is high. The patterned absorber film (absorber film pattern) may function as a binary mask by absorbing EUV light, or it may function as a phase-shift mask that reflects EUV light and interferes with the EUV light from the multilayer reflective film to produce contrast. The absorber film pattern may be used as a binary mask as described later, or as a phase-shift mask as described later. That is, the absorber film may be a phase-shift film. The absorber film preferably contains one or more metallic elements selected from the group consisting of Cr, Ta, Nb, Ir, Co, Ni, Cu, Sn, Pt, Pd, Au, and Ru.

[0051] When an absorber film pattern is used as a binary mask, the absorber film must absorb EUV light and have a low reflectivity of EUV light. Specifically, when EUV light is irradiated onto the surface of the absorber film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 2% or less. The absorber film may contain one or more metals selected from the group consisting of Ta, Ti, Sn, and Cr, as well as one or more components selected from the group consisting of O, N, B, Hf, and H. Among these, it is preferable that the absorber film contains Ta and also contains N or B. By including N or B, the crystalline state of the absorber film can be made amorphous or microcrystalline. The crystalline state of the absorber film is preferably amorphous. This improves the smoothness and flatness of the absorber film. Furthermore, when the smoothness and flatness of the absorber film are high, the edge roughness of the absorber film pattern is reduced, and the dimensional accuracy of the absorber film pattern can be improved. When using an absorber membrane pattern as a binary mask, the thickness of the absorber membrane is preferably 40 to 70 nm, and more preferably 50 to 65 nm.

[0052] When an absorber film pattern is used as a phase shift mask, the reflectivity of the absorber film for EUV light is preferably 2% or more. To obtain a sufficient phase shift effect, the reflectivity of the absorber film is preferably 9 to 15%. When an absorber film is used as a phase shift mask, the contrast of the optical image on the wafer is improved and the exposure margin is increased. Examples of materials for forming a phase shift mask include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Cr, Au, Pt, Re, Hf, Ta, Ti, and Si, alloys of Ta and Nb, oxides containing Ru alloy or TaNb alloy and oxygen, nitrides containing Ru alloy or TaNb alloy and nitrogen, and oxynitrides containing Ru alloy or TaNb alloy, oxygen, and nitrogen. When an absorber film pattern is used as a phase shift mask, the film thickness of the absorber film is preferably 30 to 60 nm, and more preferably 35 to 55 nm.

[0053] The absorber film may be a single layer or a multilayer film consisting of multiple layers. If the absorber film is a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. If the absorber film is a multilayer film, the layer located on the side of the absorber film opposite the substrate side may be an anti-reflective film used when inspecting the absorber film pattern using inspection light (for example, wavelength 193-248 nm). Examples of materials for forming the anti-reflective film include materials containing Ta and O.

[0054] The absorber film can be formed using known film deposition methods such as magnetron sputtering and ion beam sputtering. For example, when forming a Ta nitride film as an absorber film using magnetron sputtering, a Ta target is used, and sputtering is performed by supplying a gas containing Ar gas and nitrogen gas to form the absorber film. When an absorber film is formed by the above method, an absorber film is obtained in which the shape of the recesses forming the reference marks arranged on the multilayer reflective film is transferred.

[0055] [Protective Film] The reflective mask blank of the present invention may have a protective film provided between the multilayer reflective film and the absorber film. The protective film is provided to protect the multilayer reflective film from damage during the etching process (usually a dry etching process) when a pattern is formed on the absorber film by the etching process. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectance of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0056] Materials that can achieve the above objective include materials containing at least one element selected from the group consisting of Ru and Rh. That is, the protective film preferably contains at least one element selected from the group consisting of Ru and Rh. More specifically, as the above materials, examples of Rh-based materials include elemental Ru, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Ti, Nb, Rh, and Zr, elemental Rh, Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Ti, Nb, Ru, Ta, and Zr, Rh-containing nitrides containing the above Rh alloy and nitrogen, and Rh-containing oxynitrides containing the above Rh alloy, nitrogen, and oxygen. Furthermore, as materials that can achieve the above objective, examples of Rh-based materials include Al and nitrides containing these metals and nitrogen, and Al ２ O ３ Examples include the following. Among these, Ru metal element, Ru alloy, Rh metal element, or Rh alloy are preferred as materials that can achieve the above objectives. As Ru alloys, Ru-Si alloys are preferred, and as Rh alloys, Rh-Si alloys are preferred.

[0057] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In order to maintain the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 1 to 10 nm, more preferably 1.5 to 6 nm, and even more preferably 2 to 5 nm. It is also preferable that the material of the protective film is elemental Ru metal, Ru alloy, elemental Rh metal, or Rh alloy, and that the thickness of the protective film is the above preferred thickness.

[0058] The protective film may be a single layer or a multilayer film consisting of multiple layers. If the protective film is a multilayer film, it is preferable that each layer constituting the multilayer film is made of the preferred material described above. Furthermore, if the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the preferred range described above. If the protective film is a multilayer film, it is preferable that the layer of the multilayer film that is located closest to the absorber film contains Rh. Furthermore, if the layer of the multilayer film that is located closest to the absorber film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0059] The protective film can be deposited using known deposition methods such as magnetron sputtering and ion beam sputtering. When depositing a Ru film by magnetron sputtering, it is preferable to use a Ru target as the target and Ar gas as the sputtering gas.

[0060] [Etching Mask Film] The reflective mask blank of the present invention may have an etching mask film on the side of the absorber film opposite to the substrate side. Preferably, the etching mask film is made of a material that has high resistance to dry etching. When an etching mask film is formed on the absorber film, dry etching can be performed even if the minimum line width of the absorber film pattern is reduced. Therefore, it is effective for miniaturizing the absorber film pattern.

[0061] The etching mask film preferably contains one or more elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf (hereinafter also referred to as "element X3"). That is, the material constituting the etching mask film preferably contains element X3. The etching mask film may further contain at least one element selected from the group consisting of B, N, and O. Examples of materials constituting the etching mask film include element X3, oxides, nitrides, oxynitrides, carbides, carbonitrides, carbonites, fluorides, and oxyfluorides of element X3. The material constituting the etching mask film may also be a composite compound (for example, a composite oxide) containing two or more elements from element X3.

[0062] For example, Cr-based materials containing Cr as element X3 include materials containing Cr and one or more elements selected from the group consisting of Cr and O, N, C, and H, and more specifically, CrO, CrN, and CrON. The notation "CrON" represents a material containing Cr, O, and N, and the following similar notations have the same meaning. Furthermore, Si-based materials containing Si as element X3 include materials containing Si and one or more elements selected from the group consisting of Si and O, N, C, and H, and more specifically, SiO２ Examples include SiO, SiN, SiO, SiC, SiCO, SiCN, and SiCON.

[0063] The thickness of the etching mask film is preferably 2 nm or more. The thickness of the etching mask film is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less.

[0064] The etching mask film can be formed using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering.

[0065] [Conductive Film] The reflective mask blank of the present invention may have a conductive film on the side of the substrate opposite to the first main surface (second main surface). By providing a conductive film, the reflective mask blank can be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The constituent material of the conductive film can be broadly selected from those described in known literature. For example, a high dielectric constant coating described in Japanese Patent Publication No. 2003-501823, specifically a coating consisting of Si, Mo, Cr, CrON, or TaSi, can be applied. Alternatively, the constituent material of the conductive film may be a Cr compound containing Cr and one or more selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more selected from the group consisting of B, N, O, and C. The thickness of the conductive film is preferably 10 to 1000 nm, and more preferably 10 to 400 nm. The conductive film may also have a function of adjusting the stress on the second main surface side of the reflective mask blank. That is, the conductive film can adjust the reflective mask blank to be flat by balancing the stress from various films formed on the first main surface side. The conductive film can be formed using known film deposition methods, such as sputtering methods such as DC sputtering, magnetron sputtering, and ion beam sputtering, CVD, vacuum deposition, and electroplating.

[0066] The reflective mask blank of the present invention is obtained by sequentially carrying out the formation methods for each of the above-described components. For example, a method for manufacturing the reflective mask blank of the present invention is to form a multilayer reflective film on one surface of a substrate using the method described above, to form the above-described recesses that make up the reference marks on the multilayer reflective film by a focused ion beam method or a dry etching method, and to form the above-described absorber film on the multilayer reflective film on which the reference marks have been formed by sputtering.

[0067] <Method for Manufacturing a Reflective Mask and the Reflective Mask> A reflective mask can be obtained by patterning the absorbent membrane of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be explained with reference to Figure 8. Note that in Figure 8, the recesses that form the reference marks are not shown.

[0068] Figure 8(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having a conductive film 22, a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in that order. A known method can be used to form the resist pattern 40. For example, a resist is applied to the absorber film 18 of the reflective mask blank, and exposure and development are performed to form the resist pattern 40. The resist pattern 40 corresponds to the pattern formed on the wafer using a reflective mask. Then, using the resist pattern 40 in Figure 8(a) as a mask, the absorber film 18 is etched and patterned, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 18pt shown in Figure 8(b). Next, as shown in Figure 8(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 2(b), and dry etching is performed using the resist pattern 41 in Figure 8(c) as a mask. Dry etching is performed until the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 8(d).

[0069] Dry etching for forming the absorber film pattern 18pt can be performed using, for example, a Cl-based gas or a F-based gas. The resist pattern 40 or 41 can be removed by known methods, including removal with a cleaning solution. Examples of cleaning solutions include sulfuric acid-hydrogen peroxide aqueous solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide aqueous solution (APM), OH radical cleaning water, and ozonated water. If the reflective mask blank has an etching mask film, the etching mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the etching mask film as a mask. Also, if the reflective mask blank has an etching mask film, the etching mask film may be removed in the process of obtaining the reflective mask. Furthermore, the etching mask film may be removed simultaneously in the process of removing the resist pattern 40 or 41 as described above.

[0070] The reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention can be suitably applied as a reflective mask used for exposure with EUV light.

[0071] The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Examples 1 to 3 described below are examples, and Examples 4 to 6 are comparative examples.

[0072] <Example 1> The procedure for obtaining the substrate with a reflective multilayer film as shown in Example 1 will be explained as a representative example.

[0073] [Substrate] First, as a substrate, SiO ２ -TiO ２ A glass substrate (6 inches (152 mm) square, 6.3 mm thick) was prepared. This glass substrate has a coefficient of thermal expansion of 0.02 × 10⁻¹⁰ at 20°C. －７ The temperature is / °C, the Young's modulus is 67 GPa, the Poisson's ratio is 0.17, and the specific stiffness is 3.07 × 10⁻⁶. ７I understand ２ / s ２ The quality assurance area of ​​the first main surface of the substrate had a root mean square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less achieved by polishing. A 100 nm thick Cr film was deposited on the second main surface of the substrate using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / sq.

[0074] [Multilayer Reflective Film] Next, a Mo / Si multilayer reflective film was formed on the first main surface of the substrate. The Mo / Si multilayer reflective film was obtained by repeatedly depositing a Si film (thickness 4.5 nm) and a Mo film (thickness 2.3 nm) 40 times using the ion beam sputtering method, and after the 40th Mo film was formed, a Si film (thickness 4.5 nm) was further formed. The total thickness of the Mo / Si multilayer reflective film was 276.5 nm ((4.5 nm + 2.3 nm) × 40 + 4.5 nm).

[0075] Next, recesses forming reference marks were created in the formed multilayer reflective film using an FIB processing device (Hitachi High-Tech Corporation, FM3100). The shape of the recesses was a cross shape when viewed from the normal direction of the multilayer reflective film, with the long sides of the two rectangles forming the cross shape being 30 μm and the short sides being 1 μm. When forming the above recesses, the amount of ion beam irradiated to the periphery of the cross shape was adjusted to be greater than the amount of ion beam irradiated to the center of the cross shape (the center in the direction of the short side of the rectangle forming the cross shape). Specifically, the "Ratio of Edge" ("RE" in the table below) value was set to 500 in the above FIB device to form the recesses. The processing current value (ion beam irradiation current) was set to the value shown in the table below. Under the same conditions, a total of four recesses forming reference marks were formed. Following the above procedure, the substrate with the multilayer reflective film of Example 1 was obtained.

[0076] Furthermore, the shape profiles obtained for the recesses formed on the multilayer reflective film substrate of Example 1 using the method described above, and the results of measuring each parameter (average depth D, average height H, maximum depth, D / H ratio, and inclination angle) are shown in the table below.

[0077] [Evaluation] Using the reference marks formed on the multilayer reflective substrate obtained in Example 1, the reproducibility of the measurement coordinates based on the reference marks was evaluated. Specifically, using Lasertec's inspection device (ABICS E120), EUV light was irradiated onto the reference marks on the multilayer reflective substrate, and the measurement coordinates were measured 10 times repeatedly. The standard deviation when the repeated measurements were performed is shown in the table below. The smaller the standard deviation when the above repeated measurement coordinates are obtained, the better the reproducibility of the measurement coordinates. In practical terms, the standard deviation of the above measurement coordinates is preferably 0.40 nm or less, and more preferably 0.30 nm or less.

[0078] <Examples 2 to 6> As shown in the table below, except for adjusting the processing current value and RE (Ratio of Edge) parameters, recesses forming reference marks were formed in the multilayer reflective film in the same manner as in Example 1, and multilayer reflective film substrates for Examples 2 to 6 were obtained. The shape profiles of the recesses formed on the obtained multilayer reflective film substrates for Examples 2 to 6 were obtained using the method described above, and the results of measuring each parameter are shown in the table below. In addition, the multilayer reflective film substrates for Examples 2 to 6 were evaluated in the same way as the multilayer reflective film substrate for Example 1, and the reproducibility of the measurement coordinates was evaluated for each.

[0079] <Results> Table 1 shows the processing conditions for the reference marks of the multilayer reflective film substrates in Examples 1 to 6, the measurement results of the shape of the recesses, and the evaluation results of the reproducibility of the measurement coordinates. The definitions and measurement methods of each parameter related to the shape of the recesses are as described above.

[0080]

[0081] From the results shown in Table 1, it was confirmed that the multilayer reflective film substrates of Examples 1 to 3, in which the inclination angle of the recess forming the reference mark is greater than 45.0° and less than or equal to 80.0°, the recess has a protrusion on its bottom surface, and the D / H ratio, which is the ratio of the average depth D from the opening position of the recess to the surface of the protrusion to the average height H of the protrusion, is 80.0 or less, exhibit excellent reproducibility of measurement coordinates. Furthermore, from a comparison of Example 1 with Examples 2 and 3, it was confirmed that when the D / H ratio is 10.0 or less, the reproducibility of measurement coordinates is even better. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-159343, filed on September 13, 2024, are incorporated herein by reference as disclosure of the present invention.

[0082] 10 Multilayer reflective film substrate 12 Substrate 14 Multilayer reflective film 16 Protective film 18 Absorber film 18pt Absorber film pattern 20, 20a, 20b Recessed portion 22 Conductive film 24, 24a, 24b Protruding portion 30 Reflective mask blank 40, 42 Resist pattern

Claims

1. A substrate with a multilayer reflective film, comprising a substrate and a multilayer reflective film, wherein a recess forming a reference mark is arranged on the surface of the multilayer reflective film, the inclination angle of the recess is greater than 45.0° and less than or equal to 80.0°, the bottom surface of the recess has a protrusion, and the D / H ratio, which is the ratio of the average depth D from the opening position of the recess to the surface of the protrusion to the average height H of the protrusion, is 80.0 or less.

2. The multilayer reflective substrate according to claim 1, wherein the D / H ratio is 1.0 to 40.

0.

3. The substrate with a multilayer reflective film according to claim 1, wherein the maximum depth of the recess is 91.5 to 150.0 nm.

4. The multilayer reflective film substrate according to claim 1, wherein the average height H is 2.0 to 50.0 nm.

5. The substrate with a multilayer reflective film according to claim 1, wherein the shape of the reference mark when viewed from the direction normal to the surface of the multilayer reflective film is cross-shaped.

6. A multilayer reflective film substrate according to claim 1, having three or more of the aforementioned reference marks.

7. The substrate with a multilayer reflective film according to claim 1, wherein the reference mark is located in an area other than the exposure area.

8. A reflective mask blank comprising a substrate with a multilayer reflective film according to any one of claims 1 to 7, and an absorbent film disposed on the side of the multilayer reflective film opposite to the substrate side.

9. The reflective mask blank according to claim 8, wherein the absorbent film contains one or more metallic elements selected from the group consisting of chromium, tantalum, niobium, iridium, cobalt, nickel, copper, tin, platinum, palladium, gold, and ruthenium.

10. A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank described in claim 8.

11. A method for manufacturing a reflective mask blank according to claim 8, comprising: forming a multilayer reflective film on one surface of a substrate; forming the recesses that make up the reference marks on the multilayer reflective film by a focused ion beam method or a dry etching method; and forming the absorber film on the multilayer reflective film on which the reference marks have been formed by a sputtering method.

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