Reflective mask blank, reflective mask, and method for producing reflective mask blank

Abstract

To provide a reflective mask blank, a reflective mask, and a method for producing a reflective mask blank, which include a multilayer reflective film exhibiting a reduced BGL at the time of phase defect inspection and exhibiting low film stress.SOLUTION: The reflective mask blank of the present invention includes a substrate 10, and a multilayer reflective film 50 provided on the substrate 10 and configured to reflect exposure light, the multilayer reflective film 50 having a periodic laminated structure portion 51 including a low refractive index layer 30 and a high refractive index layer 20, wherein the low refractive index layer 30 contains ruthenium (Ru) and further contains one or both of carbon (C) and silicon (Si).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective mask blank, which is a material for a reflective mask used in the manufacture of semiconductor devices such as LSIs, a reflective mask, and a method for manufacturing a reflective mask blank. [Background technology]

[0002] In the manufacturing process of semiconductor devices (semiconductor devices), photolithography technology is repeatedly used, in which exposure light is irradiated onto a transfer mask and the circuit pattern formed on the mask is transferred onto a semiconductor substrate (semiconductor wafer) via a reduced projection optical system. Conventionally, the wavelength of the exposure light has mainly been 193 nm, using argon fluoride (ArF) excimer laser light, and a process called multi-patterning, which combines exposure and processing processes multiple times, has been used to ultimately form patterns with dimensions smaller than the exposure wavelength.

[0003] However, as device patterns continue to become finer, the formation of even finer patterns is becoming necessary. Therefore, extreme ultraviolet (EUV) lithography technology, which uses EUV light, which has an even shorter wavelength than ArF excimer laser light, as exposure light, has begun to be used. EUV light is light with a wavelength of approximately 0.2 to 100 nm, more specifically, light with a wavelength of approximately 13.5 nm. EUV light has extremely low transmittance through materials, making conventional transmission-type projection optics and masks incompatible, so reflective optical elements are used. Therefore, reflective masks have been proposed as masks for pattern transfer.

[0004] A typical reflective mask has a multilayer reflective film that reflects EUV light formed on a substrate, and an absorber film that absorbs EUV light formed in a pattern on the multilayer reflective film. Generally, a mask in the state before the absorber film is patterned (including a state where a resist film is formed) is called a reflective mask blank, and this is used as the material for a reflective mask. A reflective mask blank has a basic structure that includes a substrate and a multilayer reflective film that reflects EUV light formed on the substrate, and in many cases, further includes an absorber film that absorbs EUV light formed on the multilayer reflective film.

[0005] The multilayer reflective film is usually formed by alternately stacking molybdenum (Mo) films and silicon (Si) films to obtain the required reflectivity for EUV light. Furthermore, a ruthenium (Ru) film is formed on the outermost layer of the multilayer reflective film as a protective film to protect the multilayer reflective film. On the other hand, tantalum (Ta) or the like, which has a relatively large extinction coefficient for EUV light, is used as the absorber film (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-246299 Summary of the Invention [Problem to be solved by the invention]

[0007] In EUV lithography, the EUV light used as exposure light is incident on a reflective mask at an oblique angle, typically at an angle of 6 degrees relative to the normal to the main surface of the reflective mask. Part of the obliquely incident exposure light is blocked by the sidewalls of the absorber pattern, resulting in the so-called 3D effect (three-dimensional effect, shadowing effect). The 3D effect can cause positional and dimensional deviations in the transferred pattern, and a smaller 3D effect is preferable for miniaturizing patterns. The thinner the absorber pattern, the smaller the 3D effect, so a thinner absorber pattern is desirable.

[0008] Meanwhile, in addition to the thickness of the absorber pattern, the 3D effect also varies depending on the structure of the multilayer reflective film. The reflection of EUV light, the exposure light, by the multilayer reflective film occurs due to the overlapping of reflections from the interfaces of each layer within the multilayer reflective film. However, if the contribution of reflections from positions deeper than the surface of the multilayer reflective film to the reflection of exposure light by the multilayer reflective film is large, the 3D effect becomes larger. Therefore, for multilayer reflective films, increasing the relative contribution of reflections from positions closer to the surface is advantageous for reducing the 3D effect and contributes to improving transfer performance.

[0009] Generally, a multilayer reflective film has a periodic stacking structure in which low-refractive index layers and high-refractive index layers are alternately stacked. In this periodic stacking structure, molybdenum (Mo) and silicon (Si) are alternately stacked for, for example, 40 cycles to form a Mo / Si multilayer reflective film. Mo / Si multilayer reflective films are known to efficiently reflect EUV light, and are currently used as the mainstream multilayer reflective film in EUV mask blanks.

[0010] Ruthenium (Ru) has a lower refractive index and a larger extinction coefficient for EUV light with a wavelength of 13.5 nm, which is the exposure light, compared to molybdenum (Mo). Therefore, a low refractive index layer of ruthenium (Ru) has a higher reflection coefficient than a low refractive index layer of molybdenum (Mo) at an ideal interface (an interface without interdiffusion or roughness) with a high refractive index layer made of silicon (Si) or other materials.

[0011] Therefore, in a reflective multilayer film, a reflective multilayer film using ruthenium (Ru) as a low refractive index layer (Ru / Si reflective multilayer film) can obtain a higher reflectance than a reflective multilayer film using a smaller number of layers.

[0012] However, phase defects must be detected in reflective mask blanks, and even smaller defects must be detected. Phase defect inspection of the multilayer reflective film of a reflective mask blank or reflective mask uses an inspection light with the same wavelength as the exposure light to capture the intensity and changes in scattered and reflected light (defect signal) caused by defects. In phase defect inspection, the defect signal intensity in areas where no defects exist exhibits a finite value (background level: BGL) due to scattered light and noise. If the BGL is large, defects are recognized even in areas where no defects exist, resulting in so-called false defects. Therefore, to detect smaller defects, the BGL must be minimized. If the BGL is large, false defects are more likely to occur, increasing the total number of detected defects, including false defects. A process of distinguishing between false and real defects is required for detected defects. An increase in false defects increases inspection time, and if there are too many false defects, defect inspection becomes virtually impossible. Therefore, the BGL must be reduced.

[0013] Furthermore, warpage of a reflective mask blank due to large film stress causes a decrease in positional accuracy when forming a pattern on the reflective mask blank. Furthermore, when a pattern is transferred onto a wafer using a reflective mask fabricated from a reflective mask blank with a large amount of warpage, there is a greater risk of misalignment of the transferred pattern or pattern defects. Therefore, it is desirable to have a smaller film stress.

[0014] In order to alleviate the warpage of a reflective mask blank due to film stress, it is effective to subject the reflective mask blank to a heat treatment, and the higher the heat treatment temperature, the better the alleviation of warpage. However, heat treatment at a high temperature promotes interdiffusion at the interfaces of the layers of the multilayer reflective film, thereby reducing the reflectance of the multilayer reflective film for exposure light.

[0015] Therefore, it is preferable that the film stress of the multilayer reflective film can be reduced even by heat treatment at a relatively low temperature, and it is particularly preferable that the film stress is small even without heat treatment.

[0016] The present invention provides a reflective mask blank having a multilayer reflective film with a small BGL during phase defect inspection and small film stress, a reflective mask, and a method for manufacturing a reflective mask blank. [Means for solving the problem]

[0017] As a result of extensive research to solve the above problems, the inventors discovered that in a multilayer reflective film having a low refractive index layer containing ruthenium (Ru), the crystallinity of the low refractive index layer changes when the low refractive index layer contains one or both of carbon (C) and silicon (Si) in addition to ruthenium (Ru), thereby reducing the BGL during phase defect inspection and reducing film stress, and thus achieved the present invention.

[0018] [Concept 1] The reflective mask blank according to the present invention comprises: A substrate; a multilayer reflective film provided on the substrate for reflecting exposure light, the multilayer reflective film having a periodic stack structure including low refractive index layers and high refractive index layers; Equipped with The low refractive index layer may contain ruthenium (Ru) and one or both of carbon (C) and silicon (Si).

[0019] [Concept 2] In the reflective mask blank according to concept 1, The periodic stacked structure may have an intermediate layer containing at least one selected from carbon (C), nitrogen (N), and oxygen (O) between at least one of the low refractive index layer and the high refractive index layer.

[0020] [Concept 3] In the reflective mask blank according to concept 1 or 2, The periodic stacked structure may have an intermediate layer containing at least one selected from molybdenum (Mo), niobium (Nb), and zirconium (Zr) between at least one of the low refractive index layer and the high refractive index layer.

[0021] [Concept 4] In a reflective mask blank according to any one of concepts 1 to 3, When the low refractive index layer contains carbon (C), the carbon (C) content of the low refractive index layer may be 4 atomic % or more and 40 atomic % or less, and when the low refractive index layer contains silicon (Si), the silicon (Si) content may be 4 atomic % or more and 40 atomic % or less.

[0022] [Concept 5] In a reflective mask blank according to any one of concepts 1 to 4, In an X-ray diffraction pattern using CuKα radiation obtained by an out-of-plane measurement method for the multilayer reflective film, the diffraction peak with the highest intensity observed between diffraction angles 2θ of 41° and 47° may have a half-value width corresponding to a diffraction angle 2θ of 4.0° or more.

[0023] [Concept 6] In a reflective mask blank according to any one of concepts 1 to 5, The absolute value of the film stress of the multilayer reflective film may be 500 MPa or less.

[0024] [Concept 7] In a reflective mask blank according to any one of concepts 1 to 6, The multilayer reflective film may include a protective film containing ruthenium (Ru) provided on the multilayer reflective film.

[0025] [Concept 8] A reflective mask blank according to any one of concepts 1 to 7 is The optical element may further include an absorber film provided on the multilayer reflective film.

[0026] [Concept 9] The reflective mask according to the present invention comprises: A reflective mask blank according to any one of concepts 1 to 7; a patterned absorber film provided on the multilayer reflective film; may also be provided.

[0027] [Concept 10] In the method for producing a reflective mask blank according to the present invention, The multilayer reflective film of the reflective mask blank according to any one of Concepts 1 to 7 may be formed by a sputtering film formation method using a sputtering apparatus capable of mounting a plurality of targets in a chamber. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a reflective mask blank having a multilayer reflective film with a small BGL during phase defect inspection and a small film stress, a reflective mask, and a method for manufacturing a reflective mask blank. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 2 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention in which an intermediate layer and a hard mask film are not provided. [Figure 2] FIG. 1 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention in which no intermediate layer is provided. [Figure 3] FIG. 1 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention, in which a first intermediate layer and a second intermediate layer are provided. [Figure 4] FIG. 2 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention, in which a first intermediate layer is provided. [Figure 5] FIG. 2 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention, in which a second intermediate layer is provided. [Figure 6] FIG. 2 is a longitudinal sectional view showing an aspect in which an absorber film is patterned in a reflective mask blank according to an embodiment of the present invention. [Figure 7] 1 is a longitudinal sectional view showing one aspect of a reflective mask blank according to an embodiment of the present invention. [Figure 8] FIG. 2 is a longitudinal sectional view showing an aspect in which a resist film is provided in a reflective mask blank according to an embodiment of the present invention. [Figure 9]FIG. 10 is a longitudinal sectional view showing an aspect in which a pattern of a hard mask film is formed using a patterned resist film as an etching mask in a reflective mask blank according to an embodiment of the present invention. [Figure 10] FIG. 1 is a longitudinal sectional view showing a reflective mask blank according to an embodiment of the present invention, in which a low refractive index layer is provided on a substrate and no intermediate layer is provided. [Figure 11] FIG. 1 is a longitudinal cross-sectional view showing a reflective mask blank according to an embodiment of the present invention, in which a low refractive index layer is provided on a substrate, a low refractive index layer is provided in a periodic stacking structure, and no intermediate layer is provided. [Figure 12] FIG. 1 is a longitudinal sectional view showing a reflective mask blank according to Example 1 and Comparative Example 1. [Figure 13] FIG. 1 is a longitudinal sectional view showing a reflective mask blank according to Examples 2 to 8. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, the embodiments of the present invention will be described in more detail. 1 to 11, the reflective mask blank of this embodiment has a substrate 10 and a multilayer reflective film 50 that reflects exposure light and is formed on the substrate 10 (on one main surface (front surface) of the substrate 10). The reflective mask blank of this embodiment is suitable as a material (EUV mask blank) for a reflective mask (EUV mask) used in EUV lithography using EUV light as the exposure light. The wavelength of EUV light used in EUV lithography using EUV light as the exposure light is 13 to 14 nm, and typically light with a wavelength of about 13.5 nm.

[0031] The substrate 10 preferably has low thermal expansion characteristics for use in EUV light exposure, and has a thermal expansion coefficient of, for example, ±2×10 -8 / ℃, preferably ±5×10 -9 It is preferable that the glass be made of a material having a temperature within the range of 1 / ° C. / ° C. Such a material includes titania-doped quartz glass (SiO2-TiO2-based glass).

[0032] Furthermore, it is preferable to use a substrate 10 having a sufficiently flat surface, and the surface roughness of the main surface of the substrate 10 is preferably 0.2 nm or less, more preferably 0.15 nm or less, in terms of RMS value. Such a surface roughness can be obtained by polishing the substrate 10, for example. Furthermore, the substrate 10 preferably has a flatness of 100 nm or less. The size of the main surface of the substrate 10 is preferably 152 mm square, and the thickness of the substrate 10 is preferably 6.35 mm. A substrate 10 of this size is a so-called 6025 substrate (a substrate with a main surface size of 6 inches square and a thickness of 0.25 inches).

[0033] The multilayer reflective film 50 is a film that reflects EUV light, which is the exposure light, in a reflective mask. The multilayer reflective film 50 may be provided in contact with one main surface (e.g., the front surface) of the substrate 10. The present invention is not limited to this embodiment, and an undercoat film may be provided between the substrate 10 and the multilayer reflective film 50. The multilayer reflective film 50 is a film that reflects EUV light, which is the exposure light, in a reflective mask. The multilayer reflective film 50 has a periodic stacking structure in which high-refractive index layers 20, which have a relatively high refractive index for EUV light, and low-refractive index layers 30, which have a relatively low refractive index for EUV light compared to the high-refractive index layers 20, are alternately stacked. The high-refractive index layers 20 have a relatively high refractive index at the wavelength of the exposure light, and the low-refractive index layers 30 have a relatively low refractive index at the wavelength of the exposure light. The number of cycles in the periodic stacking structure is preferably 10 or more, particularly 20 or more, and 50 or less, particularly 40 or less, and even more preferably 30 or less. The reflectance value is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and even more preferably 65% ​​or more. In this embodiment, the portion having a periodic stacking structure including the low refractive index layer 30 and the high refractive index layer 20 is referred to as a periodic stacking structure portion 51.

[0034] The uppermost layer of the multilayer reflective film 50 may be a protective layer having a function of protecting the multilayer reflective film 50. In this case, a high refractive index layer 20 may be provided as the uppermost layer of the multilayer reflective film 50, and the high refractive index layer 20 may have a function of protecting the multilayer reflective film 50. When the high refractive index layer 20 is provided as the uppermost layer of the multilayer reflective film 50 in this manner, a protective film 110, an absorber film 120, etc., which will be described later, may be provided on the high refractive index layer 20.

[0035] The high refractive index layer 20 of the present embodiment may be a layer containing silicon (Si). The high refractive index layer 20 may further contain at least one additive element selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H), or may be configured as a multilayer of layers containing additive elements and layers not containing additive elements. The thickness of the high refractive index layer 20 is preferably 2.5 nm or more and 5.5 nm or less, and more preferably 3 nm or more and 5 nm or less.

[0036] The low refractive index layer 30 of the present embodiment may be a layer containing ruthenium (Ru). The low refractive index layer 30 preferably has a microcrystalline or amorphous structure, and in particular, the crystallite size of ruthenium (Ru) is preferably 2.5 nm or less, more preferably 2 nm or less. This allows the surfaces and interfaces of the multilayer reflective film 50 to be smoothed.

[0037] The crystallite size can be determined by the Scherrer equation shown below. Crystallite diameter (nm) = Kλ / βcosθ (In the formula, K is the Scherrer constant (here, 0.95), λ is the measurement X-ray wavelength (0.154 nm), β is the half-width of the diffraction peak in radians, and θ is the Bragg angle of the diffraction peak (here, the midpoint of the half-width).)

[0038] The half-width is the width of the peak at a height that indicates the average intensity between the intensity considered to be the background and the maximum intensity of the peak when a diffraction peak is plotted with the diffraction angle 2θ on the horizontal axis and the diffraction intensity on the vertical axis, and is a value with the same units as the diffraction angle 2θ.

[0039] To achieve the above-described preferred crystallite size, it is necessary that the half-width of the most intense diffraction peak derived from Ru observed between diffraction angles 2θ of 41° and 47° be 4° or more in an X-ray diffraction pattern using CuKα radiation obtained by out-of-plane measurement of the multilayer reflective film 50. If no diffraction peak appears in that region, the ruthenium (Ru) has an amorphous structure, and the half-width of the diffraction peak in this case is defined as 180°.

[0040] The multilayer reflective film 50 of the present embodiment preferably has a half-width of 4° or more, and more preferably has a half-width of 5° or more.

[0041] The low refractive index layer 30 can contain either or both of carbon (C) and silicon (Si). Carbon (C) and silicon (Si) each have the effect of changing the crystallinity of the low refractive index layer 30 containing ruthenium (Ru), making the low refractive index layer 30 microcrystalline or amorphous, and improving the smoothness of the surface and interface of the multilayer reflective film 50. This not only reduces BGL during phase defect inspection, but also has the effect of reducing film stress in the multilayer reflective film 50, making it possible to improve the amount of warpage of reflective mask blanks and reflective masks.

[0042] The BGL can be evaluated by phase defect inspection using an EUV mask blank defect inspection / review device (ABICS E120, manufactured by Lasertec Corporation), and its value is preferably 250 or less, more preferably 230 or less, even more preferably 210 or less, and even more preferably 200 or less.

[0043] The amount of warpage of a reflective mask blank or a reflective mask is preferably 300 nm or less. To achieve this, the absolute value of the film stress of the multilayer reflective film 50 is preferably 500 MPa or less, more preferably 400 MPa or less, and even more preferably 300 MPa or less. Here, compressive film stress is indicated by a negative sign, and tensile stress is indicated by a positive sign.

[0044] If the carbon (C) content in the low refractive index layer 30 containing ruthenium (Ru) is too low, the effect of microcrystalline or amorphousizing the low refractive index layer 30 cannot be obtained, and if it is too high, the reflectance of the multilayer reflective film 50 to the exposure light (EUV light) decreases. The carbon (C) content is preferably 2 atomic % or more and 40 atomic % or less, more preferably 4 atomic % or more and 25 atomic % or less, and even more preferably 4 atomic % or more and 20 atomic % or less.

[0045] If the content of silicon (Si) contained in the low refractive index layer 30 containing ruthenium (Ru) is too low, the effect of microcrystalline or amorphousizing the low refractive index layer 30 cannot be obtained. On the other hand, if the content of silicon (Si) contained in the low refractive index layer 30 containing ruthenium (Ru) is too high, the reflectivity of the multilayer reflective film 50 to the exposure light (EUV light) decreases. Therefore, the content of silicon (Si) is preferably 4 atomic % or more and 40 atomic % or less, more preferably 6 atomic % or more and 25 atomic % or less, and even more preferably 8 atomic % or more and 20 atomic % or less.

[0046] The low refractive index layer 30 can be made microcrystalline or amorphous by adding an additive element such as boron (B), nitrogen (N), or oxygen (O) in addition to carbon (C) and silicon (Si). However, from the viewpoint of the reflectivity of the multilayer reflective film 50, it is preferable to add only one or both of carbon (C) and silicon (Si) other than ruthenium (Ru). The low refractive index layer 30 may also be configured as a multilayer of layers containing additive elements and layers not containing additive elements. The thickness of the low refractive index layer 30 is preferably 1.5 nm to 4.5 nm, and more preferably 2 nm to 4 nm.

[0047] 3 to 5, intermediate layers 40, 45 may be provided between each of the low-refractive-index layers 30 and the high-refractive-index layers 20, or between some of the low-refractive-index layers 30 and the high-refractive-index layers 20, in order to prevent the formation of a reaction layer that occurs during the formation of the multilayer reflective film 50 or the formation of an interdiffusion layer due to heat treatment or the like after the formation of the multilayer reflective film 50. Materials that can be used for the intermediate layers 40, 45 include silicon nitride (SiN), silicon carbide (SiC), silicon oxide (SiO), molybdenum (Mo), molybdenum nitride (MoN), molybdenum carbide (MoC), molybdenum oxide (MoO), niobium (Nb), niobium nitride (NbN), niobium carbide (NbC), niobium oxide (NbO), zirconium (Zr), zirconium nitride (ZrN), zirconium carbide (ZrC), and zirconium oxide (ZrO). The thickness of the intermediate layers 40, 45 is preferably 0.2 nm or more and 2 nm or less, and more preferably 0.3 nm or more and 1 nm or less. In this embodiment, the intermediate layer provided on the surface of the high-refractive-index layer 20 facing away from the substrate 10 is called the first intermediate layer 40, and the intermediate layer provided on the surface of the low-refractive-index layer 30 facing away from the substrate 10 is called the second intermediate layer 45.

[0048] 1 to 5 show an embodiment in which a high refractive index layer 20 is provided on the substrate 10, but as shown in Figures 10 and 11, an embodiment in which a low refractive index layer 30 is provided on the substrate 10 can also be adopted. In Figure 11, the low refractive index layer 30 is provided on the upper surface of a periodic stacked structure portion 51. On the other hand, in Figures 1 to 5 and 10, the periodic stacked structure portion 51 constitutes a multilayer reflective film 50.

[0049] Methods for forming the multilayer reflective film 50 include sputtering, in which power is supplied to a target, the supplied power is used to convert the ambient gas into plasma (ionize) the gas, and sputtering, and ion beam sputtering, in which an ion beam is irradiated onto the target. Sputtering methods include DC sputtering, in which a direct current voltage is applied to the target, and RF sputtering, in which a radio frequency voltage is applied to the target. Magnetron sputtering, which uses a magnetic field to promote gas ionization and perform efficient sputtering, is particularly advantageous in terms of productivity. The power applied to the target may be DC or RF, and DC also includes pulse sputtering, in which a negative bias applied to the target is reversed for a short period of time to prevent the target from charging up.

[0050] The multilayer reflective film 50 can be formed by a sputtering method using, for example, a sputtering device capable of mounting multiple targets. Specifically, the target can be appropriately selected from a ruthenium (Ru) target for forming a layer containing ruthenium (Ru), a silicon (Si) target for forming a layer containing silicon (Si), a carbon (C) target for forming a layer containing carbon (C), a molybdenum (Mo) target for forming a layer containing molybdenum (Mo), and the like, and can be formed using a rare gas such as neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as the sputtering gas.

[0051] When forming a layer containing nitrogen (N), it can be formed by reactive sputtering using a nitrogen-containing gas such as nitrogen (N2) gas together with a rare gas. When forming a layer containing oxygen (O), it can be formed by reactive sputtering using an oxygen-containing gas such as oxygen (O2) gas together with a rare gas.

[0052] When forming a layer containing carbon (C), it can be formed by simultaneously using a carbon (C) target and other targets (such as a ruthenium (Ru) target, a silicon (Si) target, a molybdenum (Mo) target, a niobium (Nb) target, or a zirconium (Zr) target). Alternatively, it can be formed by reactive sputtering using a carbon oxide gas such as carbon monoxide (CO) gas or carbon dioxide (CO2) gas, or a hydrocarbon gas such as methane (CH4) gas, simultaneously with a rare gas.

[0053] Furthermore, when forming a layer containing boron (B), a boron carbide (BC) target, a ruthenium target doped with boron (B) (ruthenium boride (RuB) target), a silicon (Si) target doped with boron (B) (silicon boride (SiB) target), or the like can be used.

[0054] 1 to 11, a protective film 110 for protecting the multilayer reflective film 50 may be provided on the multilayer reflective film 50. A material containing ruthenium (Ru) is preferably used as the material for the protective film 110. The protective film 110 is required to have the function of protecting the multilayer reflective film 50 from various dry etchings and cleanings in the reflective mask manufacturing process, the exposure environment when the reflective mask is used, and cleaning treatments in the recycling process after use. Therefore, a film containing an additive element such as niobium (Nb), zirconium (Zr), titanium (Ti), or rhodium (Rh) that has resistance to various processes is preferably used, or a multilayer structure made of these materials may be used.

[0055] The protective film 110 may be formed with another film interposed between it and the multilayer reflective film 50, but is usually formed in contact with the multilayer reflective film 50.

[0056] The protective film 110 can be formed by, for example, a sputtering method. A ruthenium (Ru) target or a ruthenium (Ru) alloy target can be used to form a film or layer containing ruthenium (Ru), and a niobium (Nb) target or a niobium (Nb) alloy target can be used to form a film or layer containing niobium (Nb). Specifically, a ruthenium (Ru) target, a niobium (Nb) target, or an alloy target of ruthenium (Ru) and niobium (Nb) can be appropriately selected and used. The protective film 110 (each layer constituting the protective film 110) can be formed by sputtering using a rare gas such as neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as a sputtering gas, or by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, or a carbon-containing gas together with the rare gas. The thickness of the protective film 110 is not particularly limited, but is typically about 2 to 5 nm.

[0057] 1 to 11, the reflective mask blank of this embodiment may further have an absorber film 120 that absorbs exposure light and functions as a pattern formation film on the protective film 110. A reflective mask blank (EUV mask blank) may be formed having a substrate 10, a multilayer reflective film 50, the protective film 110, and the absorber film 120, and a reflective mask (EUV mask) may be manufactured by patterning the absorber film 120.

[0058] A specific example of such a reflective mask blank includes a substrate 10, a multilayer reflective film 50 formed on one main surface of the substrate 10 and reflecting exposure light, a protective film 110 formed on the multilayer reflective film 50, and an absorber film 120 formed on the protective film 110 and absorbing exposure light. From the reflective mask blank having the multilayer reflective film 50, the protective film 110, and the absorber film 120, a reflective mask can be manufactured that includes the substrate 10, the multilayer reflective film 50 formed on one main surface of the substrate 10 and reflecting exposure light, the protective film 110 formed on the multilayer reflective film 50, and a pattern (absorber pattern) of the absorber film 120 formed on the protective film 110 and absorbing exposure light (see FIG. 6). The absorber film 120 is a film that absorbs exposure light, specifically EUV light, and reduces reflectance. The absorber film 120 may also be a phase shift film having a phase shift function that absorbs part of the exposure light and reflects the part of the exposure light as reflected light with the phase shifted by approximately 150 to 250°.

[0059] The material of the absorber film 120 is not limited as long as it absorbs EUV light and can be patterned. Examples of the material of the absorber film 120 include materials containing tantalum (Ta) or chromium (Cr). Furthermore, materials containing Ta or Cr may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Examples of materials containing Ta include elemental Ta and tantalum compounds such as TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, and TaCONB. Specific examples of materials containing Cr include elemental Cr and chromium compounds such as CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB, CrOB, CrNB, CrONB, CrCB, CrCNB, CrCOB, and CrCONB.

[0060] Furthermore, when the absorber film 120 is a phase shift film having a phase shift function, the material may be, for example, a material containing ruthenium (Ru). The material containing ruthenium (Ru) may be an alloy with other metal elements, may contain light elements such as oxygen (O) and nitrogen (N), or may be a multilayer with other material layers.

[0061] The absorber film 120 can be formed by sputtering, preferably magnetron sputtering. Specifically, the absorber film 120 can be formed by sputtering using a metal target such as a chromium (Cr) target, a tantalum (Ta) target, or a ruthenium (Ru) target, or a metal compound target such as a chromium compound target, a tantalum compound target, or a ruthenium compound target (a target containing a metal such as Cr, Ta, or Ru, and other metal elements or light elements such as oxygen (O), nitrogen (N), carbon (C), or boron (B)). The absorber film 120 can be formed by sputtering using a rare gas such as neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as a sputtering gas, or by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, or a carbon-containing gas together with a rare gas. The thickness of the absorber film 120 is not particularly limited, but is typically about 20 to 80 nm.

[0062] As shown in FIGS. 2 to 5 and 7 to 11, a hard mask film 130 (an etching mask film for the absorber film 120) having etching characteristics different from those of the absorber film 120 may be provided on the side of the absorber film 120 away from the substrate 10, preferably in contact with the absorber film 120. This hard mask film 130 functions as an etching mask when dry etching the absorber film 120. After forming the absorber pattern, the hard mask film 130 may be left as a part of the absorber film 120, for example, as a reflectance reduction layer for reducing reflectance at wavelengths of light used in inspections such as pattern inspections, or may be removed so that it does not remain on the reflective mask. Materials for the hard mask film 130 include materials containing chromium (Cr). A hard mask film 130 made of a material containing Cr is particularly suitable when the absorber film 120 is made of a material containing Ta but not Cr. When a layer (reflectance reduction layer) that mainly serves to reduce reflectance at the wavelength of light used in inspections such as pattern inspections is formed on the absorber film 120, the hard mask film 130 can be formed on the reflectance reduction layer of the absorber film 120. The hard mask film 130 can be formed by, for example, magnetron sputtering. There are no particular limitations on the film thickness of the hard mask film 130, but it is usually about 5 to 20 nm.

[0063] As shown in Figures 1 to 11, the reflective mask blank may further have a conductive film 150 on the other main surface (back surface) of the substrate 10, which is the surface opposite to the one main surface, preferably in contact with the other main surface, used to electrostatically chuck the reflective mask to an exposure tool.

[0064] The conductive film 150 preferably has a sheet resistance of 100 Ω / □ or less, and there are no particular limitations on the material. Examples of materials for the conductive film 150 include materials containing tantalum (Ta) or chromium (Cr). Furthermore, materials containing tantalum (Ta) or chromium (Cr) may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Examples of materials containing tantalum (Ta) include elemental Ta and tantalum (Ta) compounds such as TaO, TaN, TaON, TaC, TaCO, TaCN, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCOB, TaCNB, and TaCONB. Examples of materials containing chromium (Cr) include elemental Cr and chromium (Cr) compounds such as CrO, CrN, CrON, CrC, CrCO, CrCN, CrCON, CrB, CrOB, CrNB, CrONB, CrCB, CrCOB, CrCNB, and CrCONB.

[0065] The thickness of the conductive film 150 is not particularly limited as long as it functions as an electrostatic chuck, but is typically about 20 to 300 nm. The thickness of the conductive film 150 is preferably determined so as to balance the film stress with the patterns (absorber patterns) of the multilayer reflective film 50 and the absorber film 120 after forming the reflective mask, particularly after forming the pattern (absorber pattern) of the absorber film 120. The conductive film 150 may be formed before forming the multilayer reflective film 50 or after forming all of the films on the multilayer reflective film 50 side of the substrate 10. Alternatively, the conductive film 150 may be formed after forming a portion of the films on the multilayer reflective film 50 side of the substrate 10, and then the remaining films on the multilayer reflective film 50 side of the substrate 10 may be formed. The conductive film 150 may be formed, for example, by magnetron sputtering.

[0066] 8, the reflective mask blank may further have a resist film 140 on the side farthest from the substrate 10. In this embodiment, the resist film 140 is preferably an electron beam (EB) resist. Also, it is preferable that the resist film 140 can be removed by SPM cleaning. [Example]

[0067] EXAMPLES The present invention will be specifically explained below by showing examples and comparative examples, but the present invention is not limited to the following examples.

[0068] [Example 1] A low-thermal expansion glass substrate (SiO2-TiO2-based glass substrate) measuring 152 mm square and 6.35 mm thick was used as the substrate 10. The sputtering device used was capable of mounting multiple targets and discharging the targets one by one or multiple targets simultaneously. The targets and the main surface of the substrate 10 were placed opposite each other, and the multilayer reflective film 50 was formed by DC magnetron sputtering while the substrate 10 was rotated. The Young's modulus of the substrate 10 was 67.6 GPa, the Poisson's ratio was 0.17, and the flatness within a central 142 mm square area of ​​the main surface of the substrate 10 was 100 nm or less.

[0069] More specifically, a silicon (Si) target, a ruthenium (Ru) target, and a carbon (C) target were loaded into the chamber of a sputtering apparatus, and the substrate 10 was then placed therein. First, while argon (Ar) gas (flow rate: 12 SCCM) was flowing into the chamber, power was applied to the silicon (Si) target to form a 4 nm-thick silicon (Si) layer as the high-refractive-index layer 20, and the application of power to the silicon (Si) target was then stopped. Next, while argon (Ar) gas (flow rate: 15 SCCM) was flowing into the chamber, power was applied to the ruthenium (Ru) target and the carbon (C) target to form a 3 nm-thick ruthenium (Ru) layer containing carbon (C) (RuC layer) as the low-refractive-index layer 30, and the application of power to the ruthenium (Ru) target and the carbon (C) target was then stopped. The carbon (C) content in the low-refractive-index layer 30 was set to 15 atomic %. The operation of forming these high refractive index layers 20 and low refractive index layers 30 constituted one cycle, and this was repeated 30 times to form a periodic stacked structure (periodic stacked structure portion 51). After forming the 30th cycle of the low refractive index layer 30, a 4 nm silicon (Si) layer was finally formed as the top layer of the multilayer reflective film 50 by the above-mentioned method, thereby forming the multilayer reflective film 50 (see FIG. 12).

[0070] When the X-ray diffraction pattern of the obtained multilayer reflective film 50 was measured using CuKα radiation by an out-of-plane measurement method, a diffraction peak was observed at a diffraction angle (2θ) of 43.1°, with a half-width of 6.0°.

[0071] The crystallite size calculated from the Scherrer equation below was 1.5 nm. Crystallite diameter (nm) = Kλ / βcosθ (In the formula, K is the Scherrer constant (here, 0.95), λ is the measurement X-ray wavelength (0.154 nm), β is the half-width of the diffraction peak in radians, and θ is the Bragg angle of the diffraction peak (here, the midpoint of the half-width).)

[0072] For the obtained reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50, the change in the amount of warpage (ΔTIR) within a 142 mm square at the center of the substrate 10 before and after forming the multilayer reflective film 50 was measured. The change in the amount of warpage due to compressive stress was taken as negative, and the change in the amount of warpage due to tensile stress was taken as positive. The change in the amount of warpage (ΔTIR) of the reflective mask blank according to Example 1 was -0.83 μm, and the film stress was -420 MPa when compressive stress was taken as negative and tensile stress was taken as positive.

[0073] The resulting reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50 was subjected to phase defect inspection using an EUV mask blank defect inspection / review device (ABICS E120, manufactured by Lasertec Corporation), and the background level (BGL) was confirmed to be 194.

[0074] [Examples 2 to 5] A low-thermal expansion glass substrate (SiO2-TiO2-based glass substrate) measuring 152 mm square and 6.35 mm thick was used as the substrate 10. The sputtering device used was capable of mounting multiple targets and discharging the targets one by one or multiple targets simultaneously. The targets and the main surface of the substrate 10 were placed opposite each other, and the multilayer reflective film 50 was formed by DC magnetron sputtering while the substrate 10 was rotated. The Young's modulus of the substrate 10 was 67.6 GPa, the Poisson's ratio was 0.17, and the flatness within a central 142 mm square area of ​​the main surface of the substrate 10 was 100 nm or less.

[0075] More specifically, a silicon (Si) target, a ruthenium (Ru) target, and a carbon (C) target were loaded into the chamber of a sputtering device, and the substrate 10 was placed therein. First, power was applied to the silicon (Si) target while argon (Ar) gas (flow rate: 12 SCCM) was flowed into the chamber, and a silicon (Si) layer having a thickness of 3.5 nm was formed as the high refractive index layer 20, and then the application of power to the silicon (Si) target was stopped.

[0076] Next, while argon (Ar) gas (flow rate: 15 SCCM) and nitrogen (N2) gas (flow rate: 50 SCCM) were flowing into the chamber, power was applied to the silicon (Si) target to form a 0.5 nm thick silicon nitride (SiN) layer as the first intermediate layer 40 on the side of the high refractive index layer 20 facing away from the substrate 10, and the application of power to the silicon (Si) target was then stopped.

[0077] Next, while argon (Ar) gas (flow rate: 15 SCCM) was flowing into the chamber, power was applied to the ruthenium (Ru) target and the carbon (C) target to form a ruthenium (Ru) layer (RuC layer) containing carbon (C) with a thickness of 2.5 nm as the low refractive index layer 30, and then the application of power to the ruthenium (Ru) target and the carbon (C) target was stopped. The carbon (C) contents contained in the low refractive index layer 30 were 4 atomic %, 15 atomic %, 25 atomic %, and 40 atomic % in Examples 2, 3, 4, and 5, respectively.

[0078] Next, while argon (Ar) gas (flow rate: 15 SCCM) and nitrogen (N2) gas (flow rate: 50 SCCM) were flowing into the chamber, power was applied to the silicon (Si) target to form a 0.5 nm thick silicon nitride (SiN) layer as the second intermediate layer 45 on the side of the low refractive index layer 30 facing away from the substrate 10, and the application of power to the silicon (Si) target was then stopped.

[0079] The operation of forming the high refractive index layer 20, the first intermediate layer 40 on the side of the high refractive index layer 20 away from the substrate 10, the low refractive index layer 30, and the second intermediate layer 45 on the side of the low refractive index layer 30 away from the substrate 10 constitutes one cycle, and this cycle was repeated 30 times to form a periodic stacked structure (periodic stacked structure portion 51). After forming the second intermediate layer 45 on the side of the low refractive index layer 30 away from the substrate 10 in the 30th cycle, finally, a 4 nm silicon (Si) layer was formed as the top layer of the multilayer reflective film 50 by the above-mentioned method, thereby forming the multilayer reflective film 50 (see FIG. 13).

[0080] The X-ray diffraction patterns of the obtained multilayer reflective film 50 were measured in the same manner as in Example 1. Diffraction peaks were observed at diffraction angles (2θ) of 42.4°, 43.3°, 44.1°, and 45.3°, respectively, in Examples 2, 3, 4, and 5, with half-widths of 4.0°, 5.5°, 6.9°, and 9.0°, respectively. Furthermore, the crystallite sizes calculated from the Scherrer equation were 2.2nm, 1.6nm, 1.3nm, and 1.0nm, respectively, in Examples 2, 3, 4, and 5.

[0081] The change in warpage (ΔTIR) of the obtained reflective mask blanks was measured in the same manner as in Example 1. The results were −0.92 μm, −0.55 μm, −0.47 μm, and −0.54 μm in Examples 2, 3, 4, and 5, respectively, and the film stresses were −470, −280, −240, and −270 MPa, respectively.

[0082] The background levels (BGL) of the obtained reflective mask blanks were confirmed in the same manner as in Example 1, and were found to be 222, 202, 197, and 192 in Examples 2, 3, 4, and 5, respectively.

[0083] The reflectance of the obtained multilayer reflective film 50 to EUV light with a wavelength of 13 to 14.1 nm was measured at an incident angle of 6 degrees.The central wavelength (midpoint of half-width) was 13.5 nm in all cases, and the reflectance at a wavelength of 13.5 nm was 62.4%, 61.7%, 61.1%, and 59.7% for Examples 2, 3, 4, and 5, respectively.

[0084] A comparison between Example 1 and Example 3 revealed that the provision of intermediate layers 40 and 45 made of SiN further reduced the film stress. Furthermore, the results of Examples 2 to 5 revealed that the amount of carbon contained in low refractive index layer 30 changed the crystallite size, film stress, BGL, and EUV light reflectance.

[0085] [Example 6] As the low refractive index layer 30, power was applied to a ruthenium (Ru) target and a carbon (C) target while flowing xenon (Xe) gas (flow rate: 8.7 SCCM) into the chamber, to form a ruthenium (Ru) layer (RuC layer) containing carbon (C) with a thickness of 2.5 nm, and a reflective mask blank consisting of a substrate 10 and a multilayer reflective film 50 was obtained in the same manner as in Example 2 except that the content of carbon (C) contained in the low refractive index layer 30 was 5 atomic % (see FIG. 13 ).

[0086] The X-ray diffraction pattern of the obtained multilayer reflective film 50 was measured in the same manner as in Example 1. A diffraction peak was observed at a diffraction angle (2θ) of 43.3°, with a half-value width of 5.2°. The crystallite size calculated from the Scherrer equation was 1.7 nm.

[0087] The change in warpage (ΔTIR) of the obtained reflective mask blank was measured in the same manner as in Example 1, and was found to be −0.39 μm, and the film stress was −200 MPa.

[0088] The background level (BGL) of the obtained reflective mask blank was confirmed in the same manner as in Example 1 and was found to be 212.

[0089] The reflectance of the obtained multilayer reflective film 50 to EUV light was measured in the same manner as in Examples 2 to 5. The central wavelength (midpoint of half-width) was 13.5 nm, and the reflectance at a wavelength of 13.5 nm was 61.9%. It was found that the film stress was effectively reduced when xenon (Xe) gas was used as the sputtering gas for forming the RuC layer.

[0090] [Example 7] A low-thermal expansion glass substrate (SiO2-TiO2-based glass substrate) measuring 152 mm square and 6.35 mm thick was used as the substrate 10. The sputtering device used was capable of mounting multiple targets and discharging the targets one by one or multiple targets simultaneously. The targets and the main surface of the substrate 10 were placed opposite each other, and the multilayer reflective film 50 was formed by DC magnetron sputtering while the substrate 10 was rotated. The Young's modulus of the substrate 10 was 67.6 GPa, the Poisson's ratio was 0.17, and the flatness within a central 142 mm square area of ​​the main surface of the substrate 10 was 100 nm or less.

[0091] More specifically, a silicon (Si) target, a ruthenium (Ru) target, a carbon (C) target, and a molybdenum (Mo) target were loaded into the chamber of a sputtering device, and the substrate 10 was placed thereon. First, while argon (Ar) gas (flow rate: 12.5 SCCM) was flowing into the chamber, power was applied to the silicon (Si) target to form a silicon (Si) layer having a thickness of 3.5 nm as the high refractive index layer 20, and then the application of power to the silicon (Si) target was stopped.

[0092] Next, while argon (Ar) gas (flow rate: 15 SCCM) and nitrogen (N2) gas (flow rate: 50 SCCM) were flowing into the chamber, power was applied to the silicon (Si) target to form a 0.5 nm thick silicon nitride (SiN) layer as the first intermediate layer 40 on the side of the high refractive index layer 20 facing away from the substrate 10, and the application of power to the silicon (Si) target was then stopped.

[0093] Next, while argon (Ar) gas (flow rate: 15 SCCM) was flowing into the chamber, power was applied to the ruthenium (Ru) target and the carbon (C) target to form a ruthenium (Ru) layer containing carbon (C) (RuC layer) with a thickness of 2.5 nm as the low refractive index layer 30, and then the application of power to the ruthenium (Ru) target and the carbon (C) target was stopped. The carbon (C) content in the low refractive index layer 30 was set to 15 atomic %.

[0094] Next, while argon (Ar) gas (flow rate: 15 SCCM) was flowing into the chamber, power was applied to the molybdenum (Mo) target to form a 0.5 nm thick molybdenum (Mo) layer as the second intermediate layer 45 on the side of the low refractive index layer 30 facing away from the substrate 10, and the application of power to the molybdenum (Mo) target was then stopped.

[0095] The operation of forming the high refractive index layer 20, the first intermediate layer 40 on the side of the high refractive index layer 20 away from the substrate 10, the low refractive index layer 30, and the second intermediate layer 45 on the side of the low refractive index layer 30 away from the substrate 10 constitutes one cycle, and this cycle was repeated 30 times to form a periodic stacked structure (periodic stacked structure portion 51). After forming the second intermediate layer 45 on the side of the low refractive index layer 30 away from the substrate 10 in the 30th cycle, finally, a 4 nm silicon (Si) layer was formed as the top layer of the multilayer reflective film 50 by the above-mentioned method, thereby forming the multilayer reflective film 50 (see FIG. 13).

[0096] The X-ray diffraction pattern of the obtained multilayer reflective film 50 was measured in the same manner as in Example 1. A diffraction peak was observed at a diffraction angle (2θ) of 43.3°, with a half-value width of 5.3°. The crystallite size calculated from the Scherrer equation was 1.7 nm.

[0097] The change in warpage (ΔTIR) of the obtained reflective mask blank was measured in the same manner as in Example 1, and was found to be −0.94 μm, and the film stress was −480 MPa.

[0098] The background level (BGL) of the obtained reflective mask blank was confirmed in the same manner as in Example 1 and was found to be 228.

[0099] When the reflectance of the obtained multilayer reflective film 50 to EUV light was measured in the same manner as in Examples 2 to 5, the central wavelength (midpoint of half-width) was 13.5 nm, and the reflectance at a wavelength of 13.5 nm was 65.1%.

[0100] In comparison with Example 3, it was found that using a molybdenum (Mo) layer as the second intermediate layer 45 on the side of the low refractive index layer 30 away from the substrate 10 increases the film stress, but effectively increases the reflectivity of EUV light.

[0101] [Example 8] A reflective mask blank consisting of a substrate 10 and a multilayer reflective film 50 was obtained in the same manner as in Example 7, except that, as the low refractive index layer 30, power was applied to a ruthenium (Ru) target and a silicon (Si) target while argon (Ar) gas (flow rate: 15 SCCM) was flowed into the chamber, and a ruthenium (Ru) layer containing silicon (Si) (RuSi layer) with a thickness of 2.5 nm was formed with a silicon (Si) content of 15 atomic % (see FIG. 13 ).

[0102] The X-ray diffraction pattern of the obtained multilayer reflective film 50 was measured in the same manner as in Example 1. A diffraction peak was observed at a diffraction angle (2θ) of 41.4°, with a half-width of 4.0°. The crystallite size calculated from the Scherrer equation was 2.2 nm.

[0103] The change in warpage (ΔTIR) of the obtained reflective mask blank was measured in the same manner as in Example 1, and was found to be −0.83 μm, and the film stress was −420 MPa.

[0104] The background level (BGL) of the obtained reflective mask blank was confirmed in the same manner as in Example 1 and was found to be 214.

[0105] When the reflectance of the obtained multilayer reflective film 50 to EUV light was measured in the same manner as in Examples 2 to 5, the central wavelength (midpoint of half-width) was 13.5 nm, and the reflectance at a wavelength of 13.5 nm was 63.6%.

[0106] [Comparative Example 1] A reflective mask blank consisting of a substrate 10 and a multilayer reflective film 50 was obtained in the same manner as in Example 1, except that a 3 nm thick ruthenium (Ru) layer containing no carbon (C) was formed as the low refractive index layer 30 (see Figure 12).

[0107] The X-ray diffraction pattern of the obtained multilayer reflective film 50 was measured in the same manner as in Example 1. A diffraction peak was observed at a diffraction angle (2θ) of 42.0°, with a half-width of 3.4°. The crystallite size calculated from the Scherrer equation was 2.7 nm.

[0108] The change in warpage (ΔTIR) of the obtained reflective mask blank was measured in the same manner as in Example 1, and was found to be −1.87 nm, and the film stress was −950 MPa.

[0109] The background level (BGL) of the obtained reflective mask blank was confirmed in the same manner as in Example 1 and was found to be 265.

[0110] According to this embodiment, in a multilayer reflective coating 50 having a low refractive index layer 30 containing ruthenium (Ru), the low refractive index layer 30 contains one or both of carbon (C) and silicon (Si), thereby reducing crystallinity and enabling a reduction in film stress and a reduction in BGL during phase defect inspection. Furthermore, the reduction in film stress of the multilayer reflective coating 50 allows a reduction in or elimination of the heat treatment temperature for alleviating warpage, thereby improving EUV reflectivity. Furthermore, the reduction in BGL allows for highly sensitive phase defect inspection, thereby improving the quality of reflective mask blanks and reflective masks. [Explanation of symbols]

[0111] 10 Substrate 20 High refractive index layer 30 Low refractive index layer 40 First middle layer (middle layer) 45 Second middle layer (middle layer) 50 Multilayer reflective coating 51 Periodic laminated structure part 110 Protective film 120 absorber membrane 130 Hard mask film 140 Resist film

Claims

1. A substrate; a multilayer reflective film provided on the substrate for reflecting exposure light, the multilayer reflective film having a periodic stack structure including low refractive index layers and high refractive index layers; Equipped with The reflective mask blank is characterized in that the low refractive index layer contains ruthenium (Ru) and further contains one or both of carbon (C) and silicon (Si).

2. 2. The reflective mask blank according to claim 1, wherein the carbon (C) content of the low refractive index layer is 4 atomic % or more and 40 atomic % or less.

3. 2. The reflective mask blank according to claim 1, wherein the low refractive index layer has a silicon (Si) content of 4 atomic % or more and 40 atomic % or less.

4. 2. The reflective mask blank according to claim 1, wherein the periodic stacking structure has an intermediate layer containing at least one selected from carbon (C), nitrogen (N), and oxygen (O) between at least one of the low refractive index layer and the high refractive index layer.

5. 5. The reflective mask blank according to claim 4, wherein the carbon (C) content of the low refractive index layer is 4 atomic % or more and 40 atomic % or less.

6. 5. The reflective mask blank according to claim 4, wherein the low refractive index layer has a silicon (Si) content of 4 atomic % or more and 40 atomic % or less.

7. 2. The reflective mask blank according to claim 1, wherein the periodic stacking structure has an intermediate layer containing at least one selected from molybdenum (Mo), niobium (Nb), and zirconium (Zr) between at least one of the low refractive index layer and the high refractive index layer.

8. 8. The reflective mask blank according to claim 7, wherein the carbon (C) content of the low refractive index layer is 4 atomic % or more and 40 atomic % or less.

9. 8. The reflective mask blank according to claim 7, wherein the low refractive index layer has a silicon (Si) content of 4 atomic % or more and 40 atomic % or less.

10. The reflective mask blank according to any one of claims 1 to 9, characterized in that in an X-ray diffraction pattern using CuKα radiation obtained by out-of-plane measurement of the multilayer reflective film, the half-value width corresponding to the diffraction angle 2θ of the diffraction peak with the highest intensity observed between a diffraction angle 2θ of 41° and 47° is 4.0° or more.

11. 10. The reflective mask blank according to claim 1, wherein the absolute value of the film stress of the multilayer reflective film is 500 MPa or less.

12. 10. The reflective mask blank according to claim 1, further comprising a protective film containing ruthenium (Ru) provided on the multilayer reflective film.

13. 10. The reflective mask blank according to claim 1, further comprising an absorber film provided on the multilayer reflective film.

14. A reflective mask blank according to any one of claims 1 to 9; a patterned absorber film provided on the multilayer reflective film; A reflective mask comprising:

15. A method for producing a reflective mask blank, comprising forming the multilayer reflective film of the reflective mask blank according to any one of claims 1 to 9 by a sputtering film formation method using a sputtering apparatus capable of mounting a plurality of targets in a chamber.

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