Multilayer reflective film-equipped substrate, reflective mask blank, reflective mask, and method for manufacturing semiconductor device

Abstract

Provided is a multilayer reflective film-equipped substrate capable of forming a light shielding band having a good shape.　The multilayer reflective film-equipped substrate includes a substrate, and a multilayer reflective film that is provided on the substrate and reflects EUV light. The multilayer reflective film-equipped substrate is characterized in that: the multilayer reflective film includes a transfer pattern forming region and an outer peripheral region disposed outside the transfer pattern forming region; and when the crystallinity of the multilayer reflective film is indicated by a skewness, the skewness in at least a part of the outer peripheral region is 1.5 or less.

Description

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

[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.

[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 technique using extreme ultraviolet (hereinafter referred to as EUV) light, has been proposed.

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

[0004] In such reflective masks, a dedicated shading band may be provided to sufficiently reduce the effects of reflection of exposure light from adjacent exposures. Here, the shading band is a shading frame (area) provided to surround the area on the reflective mask where the transfer pattern (circuit pattern) is formed. The shading band is intended to prevent exposure light from leaking into areas adjacent to the block on the wafer where the pattern is transferred, such as the adjacent circuit pattern area. If the shading band cannot sufficiently reduce the reflected light, exposure light may overlap the adjacent area, causing problems such as reduced resolution of the pattern in the adjacent area and / or reduced dimensional accuracy of the transfer. This problem can result in reduced yield.

[0005] A typical light-shielding band of a reflective mask is a recessed light-shielding band formed by etching a multilayer reflective film corresponding to the light-shielding band portion. As an example of a reflective mask having such a light-shielding band, Patent Document 1 describes a reflective mask comprising a substrate, a multilayer reflective film formed on the substrate, a light-absorbing layer formed on the multilayer reflective film, a circuit pattern region formed in the light-absorbing layer, and a light-shielding region provided outside the circuit pattern region.

[0006] Furthermore, in order to achieve high density and high precision in semiconductor devices using a reflective mask, it is necessary for the reflective region of the reflective mask (the surface of the multilayer reflective film) to have a high reflectivity with respect to EUV light, which is the exposure light. As such a multilayer reflective film, a multilayer film in which elements with different refractive indices are periodically stacked is generally used. For example, as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm (e.g., a wavelength of 13.5 nm), a Mo / Si multilayer film is used in which Mo films with a low refractive index and Si films with a high refractive index are alternately stacked for 40 to 60 periods. Furthermore, as disclosed in Patent Document 2, a Ru / Si multilayer film is also being considered as a multilayer reflective film.

[0007] Patent Document 2 describes an EUV blank mask including a substrate, a reflective film laminated on the substrate, and an absorbing film laminated on the reflective film. Patent Document 2 describes that the reflective film has a structure in which pairs each including a first layer and a second layer are laminated multiple times. Patent Document 2 also describes that the first layer is composed of Ru or a Ru compound in which one or more elements selected from Mo, Nb, and Zr are added to Ru, and the second layer is composed of Si.

[0008] JP 2009-212220 A JP 2021-110953 A

[0009] When forming the recessed light-shielding band by etching the multilayer reflective film, dry etching is generally used to remove the light-shielding band portion of the multilayer reflective film. However, particularly when a Ru / Si multilayer film is used as the multilayer reflective film, it is difficult to obtain etching selectivity between the Ru / Si multilayer film and the resist when forming the light-shielding band by general dry etching due to the inertness of Ru against halogen gas.

[0010] Therefore, the present inventors investigated the formation of a light-shielding zone by wet etching. Wet etching of a Ru / Si multilayer film requires the use of a strong acid solution such as hydrofluoric acid-hydrogen peroxide (FPM). Therefore, when a light-shielding zone is formed in a Ru / Si multilayer film, the sidewalls of the multilayer reflective film of the light-shielding zone may be damaged by the strong acid etching solution, allowing the etching solution to seep in, making it impossible to obtain a light-shielding zone with the designed processing width.

[0011] Therefore, an object of the present invention is to provide a substrate with a multilayer reflective film, a reflective mask blank, and a reflective mask that are capable of forming a light-shielding band with a good shape, and a method for manufacturing a semiconductor device using the reflective mask.

[0012] In order to solve the above problems, the present invention has the following configuration.

[0013] (Structure 1) Structure 1 is a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film provided on the substrate and reflecting EUV light, wherein the multilayer reflective film has a transfer pattern formation region and a peripheral region arranged outside the transfer pattern formation region, and when the crystallinity of the multilayer reflective film is expressed as skewness, the skewness in at least a part of the peripheral region is 1.5 or less.

[0014] (Configuration 2) Configuration 2 is the substrate with a multilayer reflective film according to Configuration 1, wherein the multilayer reflective film is a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked, the low refractive index layers contain at least one selected from molybdenum (Mo) and ruthenium (Ru), and the high refractive index layers contain silicon (Si).

[0015] (Configuration 3) Configuration 3 is the multilayer reflective film coated substrate according to configuration 1 or 2, wherein the degree of distortion in the transfer pattern formation region is equal to or greater than the degree of distortion in the outer peripheral region.

[0016] (Configuration 4) Configuration 4 is the multilayer reflective film-coated substrate according to any one of Configurations 1 to 3, wherein the degree of distortion in the transfer pattern formation region is 0.3 or more.

[0017] (Configuration 5) Configuration 5 is a reflective mask blank having a substrate, a multilayer reflective film provided on the substrate and reflecting EUV light, and an absorber film on the multilayer reflective film, wherein the multilayer reflective film has a transfer pattern formation region and a peripheral region disposed outside the transfer pattern formation region, and when the crystallinity of the multilayer reflective film is expressed as a distortion, the distortion in at least a part of the peripheral region is 1.5 or less.

[0018] (Structure 6) Structure 6 is the reflective mask blank of Structure 5, wherein the multilayer reflective film is a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked, the low refractive index layers contain at least one selected from molybdenum (Mo) and ruthenium (Ru), and the high refractive index layers contain silicon (Si).

[0019] (Configuration 7) Configuration 7 is the reflective mask blank according to configuration 5 or 6, wherein the distortion in the transfer pattern formation region is equal to or greater than the distortion in the outer peripheral region.

[0020] (Configuration 8) Configuration 8 is the reflective mask blank according to any one of configurations 5 to 7, wherein the degree of distortion in the transfer pattern formation region is 0.3 or more.

[0021] (Structure 9) Structure 9 is a reflective mask characterized by having an absorber pattern formed by patterning the absorber film in the transfer pattern formation region of the reflective mask blank of any one of Structures 5 to 8, and a light-shielding band formed on the multilayer reflective film in the outer circumferential region.

[0022] (Configuration 10) Configuration 10 is a method for manufacturing a semiconductor device, characterized by comprising a step of performing a lithography process using an exposure apparatus with the reflective mask of configuration 9 to form a transfer pattern on a transfer target.

[0023] According to the present invention, it is possible to provide a multilayer reflective film-coated substrate, a reflective mask blank, and a reflective mask that are capable of forming a light-shielding band with a good shape. Also, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device using the above-mentioned reflective mask.

[0024] FIG. 1 is a cross-sectional view schematically showing an example of a multilayer reflective film-coated substrate of this embodiment. FIG. 2 is a cross-sectional view schematically showing another example of a multilayer reflective film-coated substrate of this embodiment. FIG. 3 is a cross-sectional view schematically showing an example of a reflective mask blank of this embodiment. FIG. 4 is a cross-sectional view schematically showing another example of a reflective mask blank of this embodiment. FIG. 5 is a cross-sectional view schematically showing yet another example of a reflective mask blank of this embodiment. FIG. 6 is a cross-sectional view schematically showing an example of a method for manufacturing a reflective mask of this embodiment. FIG. 7 is a plan view schematically showing an example of a multilayer reflective film-coated substrate of this embodiment. FIG. 8 is a schematic diagram showing an example of an EUV exposure apparatus. FIG. 9 is a schematic diagram showing an example of an optical system of a scanning transmission electron microscope (DF-STEM) using a dark-field method. FIG. 10 is a view showing an example of a DF-STEM image of a multilayer reflective film.

[0025] 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.

[0026] FIG. 1 is a cross-sectional schematic diagram showing 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 region 22 disposed 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 region 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 electrostatic chucking may be formed on the back surface of the substrate 1 (the surface opposite to the side on which the multilayer reflective film 2 is formed).

[0027] Fig. 2 is a cross-sectional schematic view showing another example of a multilayer reflective film-coated substrate 90 of this embodiment. The multilayer reflective film-coated substrate 90 shown in Fig. 2 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a protective film 3 formed on the multilayer reflective film 2. A back surface conductive film 5 for electrostatic chuck use may be formed on the back surface of the substrate 1 (the surface opposite to the side on which the multilayer reflective film 2 is formed).

[0028] 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 the upper side in the vertical direction. "on" merely indicates the relative positional relationship between the thin film, the substrate, etc.

[0029] The multilayer reflective film coated substrate 90 of this embodiment will be specifically described.

[0030] <<Substrate 1>> The substrate 1 preferably has a low thermal expansion coefficient within the range of 0±5 ppb / °C to prevent distortion of the transferred pattern due to heat during exposure to EUV light. Examples of materials having a low thermal expansion coefficient within this range include SiO ２ -TiO ２ Glasses and multi-component glass ceramics can be used.

[0031] The main surface (first main surface) of the substrate 1 on which a transfer pattern (the absorber pattern 4a described below) is formed is preferably processed to increase its flatness. Increasing the flatness of the main surface of the substrate 1 can improve the positional accuracy and / or transfer accuracy of the pattern. For example, in the case of EUV exposure, in a 132 mm × 132 mm area of ​​the main surface of the substrate 1 on which the transfer pattern is formed, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Furthermore, 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 amount) 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 a reference, and the lowest point on the surface of substrate 1 below this focal plane.

[0032] 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.

[0033] The substrate 1 preferably has high rigidity to prevent deformation due to film stress of the thin films (such as the multilayer reflective film 2) formed thereon. In particular, it is preferable that the substrate 1 has a high Young's modulus of 65 GPa or more.

[0034] <<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 provides the reflective mask 200 with the function of reflecting EUV light. The multilayer reflective film 2 is a multilayer film in which low-refractive index layers and high-refractive index layers, each containing elements with different refractive indices as main components, are alternately stacked.

[0035] Generally, the multilayer reflective film 2 is a multilayer film in which thin films of high refractive index materials, i.e., light elements or compounds thereof (high refractive index layers), and thin films of low refractive index materials, i.e., heavy elements or compounds thereof (low refractive index layers), are alternately stacked in approximately 40 to 60 cycles.

[0036] The multilayer film used as the multilayer reflective film 2 can have a structure in which multiple periods of a high-refractive-index layer / low-refractive-index layer stacked in this order from the substrate 1 side are stacked. Alternatively, the multilayer film can have a structure in which multiple periods of a low-refractive-index layer / high-refractive-index layer stacked in this order from the substrate 1 side are stacked. 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 multiple periods of a high-refractive-index layer / low-refractive-index layer stacked in this order from the substrate 1 side are stacked, 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.

[0037] The high-refractive index layer can be a layer containing silicon (Si). Examples of materials containing Si include elemental Si and Si compounds containing boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H). By using a high-refractive index layer containing Si, a reflective mask 200 with excellent reflectivity for EUV light can be obtained. The low-refractive index layer can be a metal element selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof. These metal elements or alloys may also be doped with boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H). In a preferred example of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment, the low-refractive index layer is a molybdenum (Mo) layer, and the high-refractive index layer is a silicon (Si) layer. For example, a Mo / Si periodic stacked film in which Mo layers and Si layers are alternately stacked 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 nm 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 stacked film in which Ru layers and Si layers are alternately stacked 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 nm to 14 nm (e.g., 13.5 nm).

[0038] 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, so a multilayer film in combination with a high-refractive-index layer containing Si, a high-refractive-index material, can increase the reflectivity for EUV light. Furthermore, conventional Mo / Si multilayer reflective films have long 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.

[0039] 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) as main components, the low refractive index layer may further contain an additive element other than Mo and Ru. The additive element contained in the low refractive index layer may be 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.

[0040] In the multilayer reflective film-coated substrate 90 of this embodiment, the multilayer reflective film 2 may further include an intermediate layer between the low-refractive-index layer and the high-refractive-index layer. For example, if the low-refractive-index layer is a Ru film containing Ru as its main component and the high-refractive-index layer is a Si film containing Si as its main component, an intermediate layer may be disposed between the Ru film and the Si film. Furthermore, if the low-refractive-index layer is a Mo film containing Mo as its main component and the high-refractive-index layer is a Si film containing Si as its main component, an intermediate layer may be disposed between the Mo film and the Si film. The intermediate layer may contain at least one selected from nitrogen (N), carbon (C), oxygen (O), and boron (B). The intermediate layer may contain at least one selected from SiN, SiO, SiC, SiON, SiCN, SiOC, SiOCN, and BC. A SiN film or a C film may be preferably used as the intermediate layer. By disposing an intermediate layer such as a SiN film between the low refractive index layer and the high refractive index layer, atomic diffusion between the main component of the low refractive index layer (e.g., a Ru film) and the main component of the high refractive index layer (e.g., a Si film) can be suppressed.

[0041] In this embodiment, the crystallinity of the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 is defined by skewness. The schematic plan view of an example of the multilayer reflective film-coated substrate 90 in FIG. 7 shows the outer circumferential region 22 and the transfer pattern formation region 24 of the multilayer reflective film 2. The transfer pattern formation region 24 is a region where an absorber pattern 4 a of a reflective mask 200 (described later) is disposed. In this specification, the "outer circumferential region 22 of the multilayer reflective film 2" refers to a region of the multilayer reflective film 2 that is disposed outside (around) the transfer pattern formation region 24. The outer circumferential region 22 is a region that does not contribute to the transfer of a circuit pattern in EUV lithography. The outer circumferential region 22 is composed of a light-shielding band formation region 26, which is a band-shaped region that forms a light-shielding band 20 (see FIG. 6G) for preventing reflection of EUV light, and an outermost circumferential region 28 that is disposed outside (around) the light-shielding band formation region 26.

[0042] The transfer pattern formation region 24 is, for example, a region surrounded by 104 mm × 104 mm. The light-shielding band formation region 26 is, for example, a band-shaped region between the 104 mm × 104 mm region and the 138 mm × 138 mm region. The outermost periphery region 28 is the region from the 138 mm × 138 mm region to the edge of the substrate 1.

[0043] In the multilayer reflective film-coated substrate 90 of this embodiment, the strain of crystallinity in at least a portion of the outer peripheral region 22 of the multilayer reflective film 2 is within a predetermined range. Specifically, in the multilayer reflective film-coated substrate 90 of this embodiment, when the strain of crystallinity is expressed as strain, the strain is 1.5 or less in at least a portion of the outer peripheral region 22 of the multilayer reflective film 2. When the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 is within the above-mentioned range, this means that the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 is high, and that the crystalline state of the outer peripheral region 22 has a crystalline structure rather than an amorphous structure.

[0044] By setting the crystallinity of the peripheral region 22 of the multilayer reflective coating 2 within the above-described range, the crystallinity of the peripheral region 22 of the multilayer reflective coating 2 can be increased. As a result, the film density of the peripheral region 22 of the multilayer reflective coating 2 can be increased. In the reflective mask 200, reflection of EUV light from areas other than the transfer pattern formation region 24 adversely affects the transfer of the transfer pattern. Therefore, it is necessary to form a light-shielding band 20 with an EUV light reflectivity of 0.05% or less in the light-shielding band formation region 26 of the peripheral region 22. FIG. 6G illustrates the light-shielding band 20. Wet etching can be used to remove the multilayer reflective coating 2 in the light-shielding band formation region 26 when forming the light-shielding band 20. In the multilayer reflective coating-coated substrate 90 of this embodiment, the crystallinity and film density of the peripheral region 22 of the multilayer reflective coating 2 are high, which prevents the etchant for wet etching from seeping into the light-shielding band 20 formed on the multilayer reflective coating 2 from the sidewall 29 of the multilayer reflective coating 2. As a result, the light-shielding zone 20 can be formed in a shape that is exactly as designed, and the light-shielding zone 20 can be formed in a good shape.

[0045] The outer peripheral region 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 represented by skewness.

[0046] As used herein, the skewness (Ssk) of crystallinity refers to a value obtained by obtaining a DF-STEM image of a sample through measurement using a scanning transmission electron microscope (STEM) using the dark-field (DF) method, and analyzing a histogram of the number of pixels in the grayscale gradation of the DF-STEM image. As used herein, 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 of crystallinity of the multilayer reflective film 2 can be obtained by analyzing a 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 of crystallinity of the multilayer reflective film 2 will be further described below.

[0047] FIG. 9 shows a schematic diagram of the optical system 300 of a dark-field scanning transmission electron microscope (DF-STEM). To measure the degree of distortion of the crystallinity of the multilayer reflective film 2, the multilayer reflective film 2 is first measured using the DF-STEM, and a DF-STEM image of a predetermined position on the multilayer reflective film 2 (sample 304) is obtained. To obtain the DF-STEM image, 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. 9 illustrates the 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. The 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., the range from β1 = 68 mrad to β2 = 280 mrad) shown in FIG. 9 and inelastically scattered electrons 306 in four regions of the annular detector 310, and forming an image using a signal detected in one of the four regions. The four regions are the right region 310a, the downward region 310b, the left region 310c, and the upward 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 the formed DF-STEM image, the measurement signal of at least one of the four regions of the annular detector 310 can be used. In the examples described below, the 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 the measurement signals from the rightward region 310a or the leftward region 310c to obtain a DF-STEM image.

[0048] Measurements using DF-STEM can be performed by irradiating incident electrons 302 onto a cross section at a predetermined position of a multilayer reflective film 2 stacked with a predetermined number of periods, for example, 30 to 60 periods. Therefore, a sample 304 cut out to a thickness of 50 nm to 100 nm can be used so that the cross section of the multilayer reflective film 2 stacked with a predetermined number of periods can be seen. Therefore, the DF-STEM image obtained can have a shape that allows the cross section of the multilayer reflective film 2 to be seen. Figure 10 shows an example of a DF-STEM image obtained in this way.

[0049] Next, the obtained DF-STEM image is subjected to image analysis. The region for image analysis can be a square region including six periods of the multilayer reflective film 2. In the example of the DF-STEM image shown in FIG. 10, the region for image analysis is the area enclosed by the dotted line. Note that one period of the multilayer reflective film 2 is approximately 7 nm, so the region for image analysis (referred to as the "image analysis region") can be a square region of 42 nm x 42 nm.

[0050] 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. In FIG. 10, a higher grayscale value indicates a color closer to white, and a lower grayscale value indicates a color closer to black. The number of pixels in the image analysis region of the DF-STEM image is 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 number) by plotting the grayscale level on the horizontal axis.

[0051] In this embodiment, the skewness of the 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 of grayscale gradations obtained by performing image analysis.

[0052] In this manner, the degree of distortion of a given multilayer reflective film 2 can be determined.

[0053] In determining the skewness, it is preferable to statistically determine the skewness using only data from 120 to 255 gradations, which is a region with a high degree of crystallinity. The inventors have found that by using only data from 120 to 255 gradations when determining the skewness, the skewness exhibits a stronger correlation with 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 degree of crystallinity.

[0054] The present inventors have discovered that a light-shielding band 20 having a good shape can be formed by increasing the crystallinity of at least a part of the outer peripheral region 22 of the multilayer reflective film 2, and have arrived at the present invention. Furthermore, the present inventors have discovered that the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 can be increased by setting the skewness of the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 within a predetermined range, and have arrived at the present invention.

[0055] In conventional reflective masks 200, Mo / Si multilayer films are often used as the multilayer reflective film 2. In Mo / Si multilayer films, dry etching is generally used to form the light-shielding band 20. On the other hand, using a Ru / Si multilayer film as the multilayer reflective film 2 is expected to improve lithography performance in high-NA EUV exposure tools. In Ru / Si multilayer films, Ru is inert to halogen gas. Therefore, it is difficult to achieve the etching selectivity between the multilayer reflective film 2 and the resist required to form the Ru / Si multilayer light-shielding band 20 using typical dry etching. Therefore, it is necessary to wet-etch the Ru / Si multilayer film using a strong acid solution. Thus, there is an increasing need to form the light-shielding band 20 by wet etching. However, when the light-shielding band 20 is formed in the multilayer reflective film 2 by wet etching, a problem arises in that the light-shielding band 20 cannot be obtained with a good shape due to the adverse effects of the wet etching solution. The multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of this embodiment has an appropriate degree of crystallinity, so that when manufacturing the reflective mask 200, a shading zone 20 having a processing width according to the design value can be formed.

[0056] The degree of distortion of the crystallinity of the multilayer reflective film 2 is related to the size of the crystallized region. A smaller degree of distortion means an increase in the crystallized region. By reducing the degree of distortion, it is possible to suppress erosion of the sidewall 29 of the multilayer reflective film 2 by the light-shielding band 20 when the light-shielding band 20 is formed by wet etching.

[0057] Specifically, in the multilayer reflective film coated substrate 90 of this embodiment, when the degree of crystallinity is expressed as a skewness, the skewness is 1.5 or less, preferably 1.3 or less, in at least a part of the outer peripheral region 22 of the multilayer reflective film 2. The lower limit of the skewness is preferably 0.3 or more, more preferably 0.5 or more.

[0058] When the crystallinity (distortion) of the outer peripheral region 22 of the multilayer reflective film 2 is within the above-mentioned range, it means that the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 is high. The crystalline state of the outer peripheral region 22 means that it has a crystalline structure rather than an amorphous structure. Therefore, by using the multilayer reflective film-coated substrate 90 of this embodiment, it is possible to manufacture a reflective mask 200 having a light-shielding band 20 with a good shape.

[0059] The degree of crystallinity distortion in the entire outer peripheral region 22 (the light-shielding band forming region 26 and the outermost peripheral region 28) of the multilayer reflective film 2 can be within the above-mentioned predetermined range. In addition, the degree of crystallinity distortion in at least the light-shielding band forming region 26 can be within the above-mentioned predetermined range.

[0060] Furthermore, the skewness of the crystallinity in the outer peripheral region 22 (the light-shielding band forming region 26 and the outermost peripheral region 28) of the multilayer reflective film 2 does not have to be constant in the thickness direction of the multilayer reflective film 2, and can have a distribution that is inclined in the thickness direction. For example, the crystallinity of the upper part of the multilayer reflective film 2 can be made lower (skewness is larger) than the crystallinity of the lower part (the substrate 1 side of the multilayer reflective film 2).

[0061] 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 region 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 that of the peripheral region 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 region 22.

[0062] Specifically, in the multilayer reflective film-coated substrate 90 of this embodiment, the skewness 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 skewness of crystallinity is preferably 2.4 or less, more preferably 2.0 or less. By ensuring that the skewness of crystallinity in the transfer pattern formation region 24 of the multilayer reflective film 2 is 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 skewness does not need to be constant in the film thickness direction of the multilayer reflective film 2, and can have a gradient distribution in the film 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 (skewness is greater) than that of the lower portion.

[0063] 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.

[0064] When the multilayer reflective film 2 is formed by ion beam sputtering or magnetron sputtering, the crystallinity (distortion) of the multilayer reflective film 2 can be controlled by changing the film formation conditions, such as the discharge conditions, film formation pressure, the type of film formation gas such as a rare gas, the distance between the mask shield and the substrate 1, and / or the angle between the substrate 1 and the target.

[0065] 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 includes 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.

[0066] 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.

[0067] <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.

[0068] 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.

[0069] 2 shows a case where the protective film 3 is a single layer. However, the protective film 3 may have a stacked 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.

[0070] 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 reflectivity 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.

[0071] 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 of 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.

[0072] Any known film formation method can be used without any particular limitation as a 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.

[0073] <Reflective mask blank 100> This embodiment is a reflective mask blank 100 having a substrate 1, a multilayer reflective film 2 that is provided on the substrate 1 and reflects EUV light, and an absorber film 4 on the multilayer reflective film 2. The multilayer reflective film 2 of the reflective mask blank 100 has a transfer pattern formation region 24 and a peripheral region 22 that is arranged outside the transfer pattern formation region 24, similar to the multilayer reflective film-coated substrate 90 shown in FIG.

[0074] <<Absorber film 4>> The reflective mask blank 100 of this embodiment includes an absorber film 4 on the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 described above, or on the protective film 3 formed on the multilayer reflective film 2. The multilayer reflective film 2 included in the reflective mask blank 100 has the same characteristics as the multilayer reflective film-coated substrate 90 described above, such as the crystallinity in at least a part of the outer circumferential region 22 being a predetermined degree of distortion, as described above.

[0075] 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 can further have another thin film, such as a resist film 11, on the absorber film 4.

[0076] 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 can further have another thin film, such as a resist film 11, on the absorber film 4.

[0077] Fig. 5 is a cross-sectional schematic diagram showing another example of the 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.

[0078] The absorber film 4 of the reflective mask blank 100 of this embodiment can absorb EUV light. 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.

[0079] 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 absorbs EUV light and 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 portion where the absorber film 4 is formed absorbs and attenuates EUV light while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Furthermore, in a region (field portion) 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 portion. 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 light beams with inverted phase differences 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 makes it possible to increase various latitudes related to exposure, such as exposure dose latitude and focus latitude.

[0080] 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 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 forming the absorber film 4 into a multilayer film, various functions can be added to the absorber film 4. When the absorber film 4 has a phase shift function, forming it into a multilayer film can increase the range of optical adjustment, making it easier to obtain the desired reflectance.

[0081] 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 can be etched 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 addition to the above metal or alloy.

[0082] 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 has been added.

[0083] Furthermore, in terms 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 4 a 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 root mean square roughness (Rms).

[0084] 5 , the reflective mask blank 100 of this embodiment can have an etching mask film 6 on the 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.

[0085] The reflective mask blank 100 of this embodiment preferably has an etching mask film 6 on the absorber film 4 .

[0086] 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).

[0087] 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.

[0088] 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 compounds (metal silicide compounds) containing a metal in silicon or a silicon compound. Examples of metal silicon compounds include a material containing a metal, Si, and at least one element selected from N, O, C, and H.

[0089] The thickness of the etching mask film 6 is preferably 3 nm or more in order to form a pattern with high precision 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.

[0090] <<Back Conductive Film 5>> A back conductive film 5 for electrostatic chucks can be formed on the back surface of the substrate 10 (the surface opposite to the surface on which the multilayer reflective film 2 is formed). The sheet resistance required for the back conductive film 5 for electrostatic chucks is typically 100 Ω / □ (Ω / square) or less. The back 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 back conductive film 5 is preferably made of a material containing chromium (Cr) or tantalum (Ta). For example, the back conductive film 5 is preferably made of a Cr compound containing Cr and at least one element 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), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. 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, and is, for example, 10 nm to 200 nm.

[0092] <Reflective Mask 200> This embodiment is a reflective mask 200 having a substrate 1, a multilayer reflective film 2 provided on the substrate 1 and reflecting EUV light, and an absorber pattern 4a obtained by patterning an absorber film 4 on the multilayer reflective film 2. As described above, the multilayer reflective film 2 included in the reflective mask 200 has similar characteristics, such as the crystallinity in at least a part of the outer peripheral region 22 (outermost peripheral region 28) being a predetermined degree of distortion.

[0093] As shown in Figure 6G, the reflective mask 200 of this embodiment comprises an absorber pattern 4a formed by patterning the absorber film 4 in the transfer pattern forming region 24 of the above-mentioned reflective mask blank 100, and a multilayer reflective film-coated substrate 90 and a light-shielding band 20 formed in the multilayer reflective film 2 in a portion corresponding to the light-shielding band forming region 26 of the reflective mask blank 100.

[0094] 6A to 6G are schematic views 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.

[0095] 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 a 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 region 22. The peripheral region 22 also has a light-shielding band formation region 26 and an outermost peripheral region 28. A pattern is written on the resist film 11 using an electron beam lithography system, and a development and rinsing process is then performed to form a resist pattern 11a ( FIG. 6B ).

[0096] Using the resist pattern 11a as a mask, the absorber film 4 is dry-etched, whereby the portions of the absorber film 4 that are not covered by the resist pattern 11a are etched, and an absorber pattern 4a is formed (FIG. 6C).

[0097] As an etching gas for the absorber film 4, for example, a fluorine-based gas and / or a chlorine-based gas can be used. As the fluorine-based gas, CF ４ , CHF ３ , C2F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ , C.H. ２ F ２ , C.H. ３ F, C ３ F ８ , SF ６ , and F ２ The chlorine-based gas may be Cl ２ , SiCl ４ , CHCl ３ , CCl ４ , and BCl ３ In addition, a fluorine-based gas and / or a chlorine-based gas and O ２ In this case, a mixed gas containing a predetermined ratio of these may be used. These etching gases may further contain an inert gas such as He and / or Ar, if necessary.

[0098] After the absorber pattern 4a is formed, the resist pattern 11a is removed with a resist remover (FIG. 6D).

[0099] Next, a resist film 11 is formed on the absorber pattern 4a and the protective film 3. A pattern of the light-shielding band 20 is drawn (exposed) on the resist film 11, followed by development and rinsing to form a resist pattern 11b for forming the light-shielding band 20 ( FIG. 6E ). Next, to form the light-shielding band 20, dry etching is performed using the resist pattern 11b as a mask and the same etching gas as used to dry-etch the absorber pattern 4a, thereby removing the absorber film 4 corresponding to the light-shielding band formation region 26. Thereafter, the protective film 3 and the multilayer reflective film 2 are removed by wet etching using an etching solution appropriate for the materials of the protective film 3 and the multilayer reflective film 2, thereby forming the light-shielding band 20 ( FIG. 6F ). In this embodiment, the high crystallinity of the outer peripheral region 22 (light-shielding band formation region 26) of the multilayer reflective film 2 can suppress the adverse effects of wet etching when forming the light-shielding band 20.

[0100] Next, the resist pattern 11b is removed using a resist remover. After the resist pattern 11b 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. 6G).

[0101] 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.

[0102] The reflective mask 200 obtained in this manner has a degree of distortion of the crystallinity of the outer peripheral region 22 of the multilayer reflective film 2 within the above-mentioned predetermined range, so that the shape of the light-shielding band 20 can be formed well.

[0103] <Method for Manufacturing Semiconductor Device> The method for manufacturing a semiconductor device of this embodiment includes a step of performing a lithography process using an exposure apparatus and the reflective mask 200 of this embodiment described above to form a transfer pattern on a transfer target object.

[0104] A transfer pattern can be formed on a semiconductor substrate (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.

[0105] The reflective mask 200 of this embodiment can have a good-shaped light-shielding band 20. Therefore, by using the reflective mask 200 of this embodiment, it is possible to increase the density and precision of semiconductor devices.

[0106] 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.

[0107] 9 shows a schematic configuration of an EUV exposure apparatus 50, which is an apparatus for transferring a transfer pattern onto a resist film 11 formed on a semiconductor substrate 60. The EUV exposure apparatus 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 apparatus 50 is filled with hydrogen gas.

[0108] 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 irradiates 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.

[0109] The EUV light reflected by the reflective mask 200 is reduced by the projection optical system 57 to a pattern image light, typically about one-fourth the original size, and projected onto the semiconductor substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred onto a 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 required processes.

[0110] Examples and comparative examples will be described below.

[0111] (Fabrication of Multilayer Reflective Film-Coated Substrate 90 in Examples 1 to 5 and Comparative Examples 1 and 2) First, a substrate 1 having a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) and having a polished first main surface and a polished second main surface was prepared as the substrate 1 in the examples and comparative examples. This substrate 1 was made of low thermal expansion glass (SiO ２ -TiO ２ The substrate 1 is made of a glass (based glass). The main surface of the substrate 1 is polished by a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0112] Next, a multilayer reflective film 2 consisting of a low refractive index layer and a high refractive index layer was formed on the main surface (first main surface) of the substrate 1. Table 1 shows the materials and compositions of the multilayer reflective film 2 of Examples 1 to 5. In Table 1, the "Material of multilayer reflective film" column for Example 1 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. Note that Example 3 lists "Ru / SiN / Si / SiN," which means that a SiN film was formed as an intermediate layer between the low refractive index layer (Ru film) and the high refractive index layer (Si film).

[0113] The multilayer reflective coatings 2 of the examples and comparative examples were formed by magnetron sputtering using a Si target and a Ru or Mo target with Kr gas. First, a high-refractive index layer of Si was formed to a thickness of 4.2 nm using a Si target so as to be in contact with the main surface of the substrate 1. 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 coatings 2 of the examples and comparative examples were formed to have different degrees of crystallinity. Specifically, the crystallinity of the multilayer reflective coating 2 was controlled by changing the distance between the mask shield and the substrate 1 among the film formation conditions. When the distance between the mask shield and the substrate 1 in Example 1 was set to 1, the distance in Example 2 was set to 1.3. In Examples 3 and 4, the distance was the same as in Example 1. In Example 5, the distance was the same as in Example 2. The distances in Comparative Examples 1 and 2 were set to 0.4 and 0.7, respectively. 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 of the substrate 1 .

[0114] In the multilayer reflective film 2 of Example 3, after the high refractive index layer and the low refractive index layer were formed, nitrogen gas was introduced and a SiN film having a thickness of 0.8 nm was formed by reactive sputtering using a Si target.

[0115] After the formation of the multilayer reflective film 2 of each of the examples and comparative examples, the film was subjected to a heat treatment by heating at 200° C. for 10 minutes in an air atmosphere.

[0116] In this manner, the multilayer reflective film coated substrates 90 of Examples 1 to 5 and Comparative Examples 1 and 2 were manufactured.

[0117] (Measurement of Distortion of Multilayer Reflective Film 2) The distortion of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of the example and comparative example prepared as described above was measured. The measurement method is as follows.

[0118] First, the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of each of the examples and comparative examples was observed with a scanning transmission electron microscope (DF-STEM) using a dark field method to obtain a DF-STEM image.

[0119] For DF-STEM observation, the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 of the example and comparative example was cut out to a thickness of 50 nm to 100 nm so that the cross section of the 40-period laminated multilayer reflective film 2 could be seen, and this was used as sample 304. In the multilayer reflective film 2 of the example and comparative example, DF-STEM observation was performed on samples 304 at two locations: one in the peripheral region 22 (light-shielding band formation region 26) and one in the transfer pattern formation region 24. When the center of the 152 mm × 152 mm multilayer reflective film-coated substrate 90 is defined as coordinates (0 mm, 0 mm), the position of the sample 304 in the peripheral region 22 was (-65 mm, -65 mm), and the position of the sample 304 in the transfer pattern formation region 24 was (0 mm, 0 mm), and the multilayer reflective film 2 at these two locations was cut out as sample 304.

[0120] Next, using the DF-STEM optical system shown in FIG. 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 (β1 to β2) measured by the annular detector 310: β1 = 68 mrad, β2 = 280 mrad

[0121] Of the four regions of the annular detector 310, 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).

[0122] Next, the obtained DF-STEM image was subjected to image analysis. In the DF-STEM image of sample 304 (multilayer reflective coating 2), the region for image analysis was a square region including six periods of the multilayer reflective coating 2. FIG. 10 shows an example of a DF-STEM image of the multilayer reflective coating 2. In the example shown in FIG. 10, the region for image analysis (image analysis region) is the inner region surrounded by the dotted line. Note that one period of the multilayer reflective coating 2 is approximately 7 nm, so the image analysis region was a square region of 42 nm x 42 nm.

[0123] Next, the DF-STEM image was subjected to image analysis, and the pixels in the image analysis region of the DF-STEM image were quantified as a grayscale ranging from 0 to 255. A higher grayscale value indicates a color closer to white, and a lower grayscale value indicates a color closer to black. The number of pixels in the image analysis region of the DF-STEM image was 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 number) by plotting the grayscale level on the horizontal axis.

[0124] Next, skewness was calculated by a known statistical method using only data from the distribution of gradation and pixel count in the image analysis region, where the grayscale gradation ranged from 120 to 255. The skewness obtained using the data in the range from 120 to 255 can be regarded as a value indicating the crystallinity of the multilayer reflective film 2.

[0125] Table 1 shows the distortions of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of the examples and comparative examples in the outer peripheral region 22 (light-shielding band forming region 26) and the transfer pattern forming region 24, determined as described above.

[0126] In addition, when the skewness was calculated in the same manner as above for the positions (65 mm, 65 mm), (-65 mm, 65 mm) and (65 mm, -65 mm) of the sample 304 in the outer peripheral region 22 in Examples 1 to 5 and Comparative Examples 1 and 2, it was confirmed that the skewness was similar to that of (-65 mm, -65 mm) (within the range of ±0.10).

[0127] Furthermore, when the skewness was calculated in the same manner as above for the positions (-40 mm, -40 mm) and (40 mm, 40 mm) of the sample 304 in the transfer pattern forming region 24 in Examples 1 to 5 and Comparative Examples 1 and 2, it was confirmed that the skewness was similar to that for (0 mm, 0 mm) (within the range of ±0.10).

[0128] (Formation of Light-Shielding Zone 20) Multilayer reflective film-coated substrates 90 of Examples 1 to 5 and Comparative Examples 1 and 2 were manufactured in the same manner as the samples for measuring distortion. The multilayer reflective film 2 in the light-shielding zone formation region 26 of the multilayer reflective film-coated substrates 90 of the Examples and Comparative Examples was removed by wet etching to form the light-shielding zone 20 for evaluation. Specifically, a 3.5-nm-thick Ru film was first formed as the protective film 3 on the multilayer reflective film 2 of the multilayer reflective film-coated substrates 90 of the Examples and Comparative Examples. The Ru film was formed by DC magnetron sputtering using a Ru target and introducing argon (Ar) gas. Next, a resist film 11 was formed on the protective film 3. A pattern of the light-shielding zone 20 was drawn (exposed) on this resist film 11, and the resist film was then developed and rinsed to form a resist pattern in the areas other than the light-shielding zone 20. Next, to form the light-shielding zone 20, the protective film 3 and the multilayer reflective film 2 were removed by wet etching. Hydrofluoric acid and hydrogen peroxide solution were used as the etchant for the wet etching. Next, the resist pattern was peeled off to obtain a multilayer reflective film coated substrate 90 having a light-shielding zone 20. The processing width deviation of the light-shielding zone 20 of the multilayer reflective film coated substrates 90 of the examples and comparative examples having the light-shielding zone 20 was measured as follows.

[0129] (Measurement of processing width deviation of light-shielding zone 20) The width of the light-shielding zone 20 of the multilayer reflective film-coated substrate 90 of the example and comparative example was measured to obtain the deviation relative to the design value of the processing width of the light-shielding zone 20. Table 1 shows the processing width deviation of the light-shielding zone 20 of the example and comparative example. The processing width deviation is shown as (actual measurement value - design value) / design value x 100.

[0130] As is clear from Table 1, the processing width variation of the light-shielding bands 20 of the multilayer reflective film-coated substrates 90 of Examples 1 to 5 was within an appropriate range. In contrast, the processing width variation of the light-shielding bands 20 of the multilayer reflective film-coated substrates 90 of Comparative Examples 1 and 2 was large. Therefore, when a reflective mask 200 is manufactured using the multilayer reflective film-coated substrates 90 of Comparative Examples 1 and 2, it may not be possible to form a light-shielding band 20 with a good shape.

[0131]

[0132] REFERENCE SIGNS LIST 1 substrate 2 multilayer reflective film 3 protective film 4 absorber film 4a absorber pattern 5 back surface conductive film 6 etching mask film 11 resist film 11a, 11b resist pattern 20 light-shielding zone 22 peripheral region 24 transfer pattern formation region 26 light-shielding zone formation region 28 outermost peripheral region 29 side wall of multilayer reflective film of light-shielding zone 50 EUV exposure device 51 EUV light generation unit 52 laser light source 53 tin droplet generation unit 54 capture unit 55 collector 56 irradiation optical system 57 projection optical system 58 reticle stage 59 wafer stage 60 semiconductor substrate 90 substrate with multilayer reflective film 100 reflective mask blank 200 reflective mask 300 optical system of dark-field scanning transmission electron microscope (DF-STEM) 302 incident electrons 304 sample 306 Diffracted electrons and inelastically scattered electrons 310 Annular detector 310a Region to the right of the annular detector (region in the 3 o'clock direction) 310b Region to the bottom of the annular detector (region in the 6 o'clock direction) 310c Region to the left of the annular detector (region in the 9 o'clock direction) 310d Region to the top of the annular detector (region in the 12 o'clock direction)

Claims

1. A multilayer reflective film-coated substrate having a substrate and a multilayer reflective film provided on the substrate and reflecting EUV light, wherein the multilayer reflective film has a transfer pattern formation area and a peripheral area located outside the transfer pattern formation area, and when the crystallinity of the multilayer reflective film is expressed as a distortion index, the distortion index in at least a portion of the peripheral area is 1.5 or less.

2. The multilayer reflective film coated substrate according to claim 1, wherein the multilayer reflective film is a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated, the low refractive index layers contain at least one selected from molybdenum (Mo) and ruthenium (Ru), and the high refractive index layers contain silicon (Si).

3. The multilayer reflective film coated substrate according to claim 1 or 2, wherein the degree of distortion in the transfer pattern formation region is equal to or greater than the degree of distortion in the outer circumferential region.

4. The multilayer reflective film-coated substrate according to claim 1 or 2, wherein the degree of distortion in the transfer pattern formation region is 0.3 or more.

5. A reflective mask blank having a substrate, a multilayer reflective film provided on the substrate and reflecting EUV light, and an absorber film on the multilayer reflective film, wherein the multilayer reflective film has a transfer pattern formation region and a peripheral region disposed outside the transfer pattern formation region, and when the crystallinity of the multilayer reflective film is expressed as a distortion, the distortion in at least a portion of the peripheral region is 1.5 or less.

6. The reflective mask blank according to claim 5, wherein the multilayer reflective film is a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated, the low refractive index layers contain at least one selected from molybdenum (Mo) and ruthenium (Ru), and the high refractive index layers contain silicon (Si).

7. A reflective mask blank according to claim 5 or 6, wherein the distortion in the transfer pattern formation region is equal to or greater than the distortion in the outer circumferential region.

8. A reflective mask blank according to claim 5 or 6, wherein the degree of distortion in the transfer pattern formation region is 0.3 or more.

9. A reflective mask comprising an absorber pattern formed by patterning the absorber film in the transfer pattern forming region of the reflective mask blank according to claim 5 or 6, and a light-shielding band formed in the multilayer reflective film in the peripheral region.

10. 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 object.

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