Reflection-type mask blank and method for manufacturing reflection-type mask

Abstract

A reflective mask blank according to the present invention comprises: a substrate 10; and a multilayer reflective film (50) that is formed on one main surface of the substrate (10) and reflects exposure light. The multilayer reflective film (50) has a periodic laminated structure in which a low refractive index layer (30) containing ruthenium (Ru), a high refractive index layer (20) containing silicon (Si), and a diffusion prevention layer (40) for preventing mutual diffusion of ruthenium (Ru) and silicon (Si) are periodically laminated. The diffusion prevention layer (40) is formed in contact with the low-refractive-index layer (30) on both or either one of the side of the low-refractive-index layer (30) that is close to the substrate (10) and the side of the low-refractive-index layer (30) that is away from the substrate (10). The diffusion prevention layer (40) is composed of one or more sub-layers selected from the group consisting of a silicon nitride (SiN)-containing layer, a silicon carbide (SiC)-containing layer, a molybdenum (Mo)-containing layer, a molybdenum nitride (MoN)-containing layer, and a molybdenum carbide (MoC)-containing layer.

Description

Technical Field

[0001] The present invention relates to a reflective mask used for manufacturing semiconductor devices such as LSI, a reflective mask blank as a raw material thereof, and a method for manufacturing the reflective mask blank. Background Art

[0002] In the manufacturing process of semiconductor devices (semiconductor apparatuses), photolithography technology is widely used to repeatedly irradiate a transfer mask with exposure light and transfer the circuit pattern formed on the mask to a semiconductor substrate (semiconductor wafer) through a reduced projection optical system. In the past, the wavelength of exposure light was mainly 193nm using argon fluoride (ArF) excimer laser, and by adopting a process called multi-patterning that combines multiple exposure processes and processing processes, a pattern with a size smaller than the exposure wavelength was finally formed.

[0003] However, as the industry continues to demand the miniaturization of device patterns, it is necessary to form further fine patterns. Therefore, as exposure light, EUV lithography technology that uses extreme ultraviolet (hereinafter referred to as "EUV") light with a shorter wavelength than ArF excimer laser is increasingly recognized by the industry. EUV light refers to light with a wavelength of about 0.2 to 100nm, more specifically, light with a wavelength of around 13.5nm. EUV light has extremely low transmittance to matter, and the previous transmission-type projection optical system and mask cannot be used, so reflective optical elements are used. Therefore, reflective masks are also proposed as masks for pattern transfer.

[0004] A general reflective mask is a multilayer reflective film that reflects EUV light formed on a substrate, and an absorber film that absorbs EUV light is patterned on the multilayer reflective film. On the other hand, generally speaking, a film in a state before a pattern is formed on the absorber film (including a state in which a resist film is formed) is called a reflective mask blank, which is used as a material for a reflective mask.

[0005] The reflective mask blank generally has a basic structure including a substrate having low thermal expansion and a multilayer reflective film formed thereon for reflecting EUV light, and further includes an absorber film formed on the multilayer reflective film for absorbing EUV light.

[0006] As a multilayer reflective film, a multilayer reflective film having a necessary reflectivity for EUV light obtained by alternately stacking molybdenum (Mo) films and silicon (Si) films is generally used. In addition, as a protective film for protecting the multilayer reflective film, a ruthenium (Ru) film is formed on the outermost layer of the multilayer reflective film. On the other hand, as an absorber film, tantalum (Ta) or the like having a relatively large extinction coefficient for EUV light is used (Patent Document 1: Japanese Patent Application Publication No. 2002-246299).

[0007] In EUV lithography, the exposure light is incident obliquely with respect to the reflective mask, and the incident angle of 6 degrees with respect to the normal of the main surface of the reflective mask has become the mainstream. Part of the obliquely incident exposure light is blocked by the side wall of the absorber pattern, producing the so-called 3D effect (three-dimensional effect, shadow effect). The 3D effect is the cause of the positional and dimensional displacement of the transfer pattern. The smaller the 3D effect, the more ideal the pattern is in terms of miniaturization. The thinner the absorber pattern, the smaller the 3D effect, so it is desirable to make it thinner.

[0008] On the other hand, 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 the exposure light by the multilayer reflective film is caused by the overlap of reflections generated from the interfaces of each layer inside the multilayer reflective film, but the main reason for the increase in the 3D effect is that the influence of reflection from a position deeper from the surface of the multilayer reflective film is greater. Therefore, in the multilayer reflective film, relatively increasing the contribution of reflection from a position shallow from the surface is conducive to reducing the 3D effect.

[0009] Generally, it is known that a multilayer reflective film has a periodic stacking structure in which low refractive index layers and high refractive index layers are alternately stacked. It is known that a multilayer reflective film (Mo / Si multilayer reflective film) with about 40 cycles of alternating stacking efficiently reflects EUV light and is currently used as the mainstream multilayer reflective film in EUV masks.

[0010] Ruthenium (Ru) is a material with a lower refractive index and a larger absorption coefficient at a wavelength of 13.5nm compared to molybdenum (Mo). Ruthenium (Ru) has a higher reflection coefficient at an ideal interface with silicon (Si) (an interface without mutual diffusion and roughness). Therefore, in a multilayer reflective film, when ruthenium (Ru) is used as a low refractive index layer, the contribution of reflection from the interface located at a shallow position from the surface of the multilayer reflective film becomes larger, and the increase in reflectivity is saturated with a smaller number of layers relative to the increase in the number of layers of the multilayer reflective film. On the other hand, due to the larger absorption coefficient, the more layers of the multilayer reflective film, the greater the loss caused by the absorption effect. As a result, when the number of layers of the multilayer reflective film is small, the reflectivity of the Ru / Si multilayer reflective film is higher, but when the number of layers increases, the reflectivity of the Mo / Si multilayer reflective film shows a tendency to increase.

[0011] If the comparison is made with the same number of layers, it is considered that the Ru / Si multilayer reflective film has a relatively greater contribution from reflection at a position closer to the surface, and the Ru / Si multilayer reflective film is more advantageous from the viewpoint of the 3D effect.

[0012] However, in the Ru / Si multilayer reflective film, ruthenium (Ru) and silicon (Si) easily form an interdiffusion layer, and the reflectivity of each interface decreases, and the desired reflectivity cannot be obtained.

[0013] The inventors discovered that, in a multilayer reflective film in which Ru and Si, which contribute greatly to reflection from a shallower position, are alternately stacked on the surface of the multilayer reflective film, by providing a diffusion prevention layer that effectively prevents mutual diffusion of Ru and Si to prevent a decrease in reflectivity, a reflective mask blank with a high contrast mask can be produced while improving the 3D effect, thereby completing the present invention. Summary of the invention

[0014]

Concept 1

[0015] The reflective mask blank of the present invention is characterized by comprising:

[0016] substrate; and

[0017] a multilayer reflective film formed on one main surface of the substrate for reflecting exposure light,

[0018] The multilayer reflective film has a periodic stacked structure in which a low refractive index layer containing ruthenium (Ru), a high refractive index layer containing silicon (Si), and an anti-diffusion layer for preventing mutual diffusion of ruthenium (Ru) and silicon (Si) are periodically stacked.

[0019] The diffusion prevention layer is formed in contact with the low refractive index layer on both or one of the sides of the low refractive index layer close to the substrate and the side of the low refractive index layer far from the substrate.

[0020] The diffusion prevention layer is composed of one or more sub-layers selected from a layer containing silicon nitride (SiN), a layer containing silicon carbide (SiC), a layer containing molybdenum (Mo), a layer containing molybdenum nitride (MoN), and a layer containing molybdenum carbide (MoC).

[0021]

Concept 2

[0022] In the reflective mask blank based on Concept 1,

[0023] The ruthenium content of the low refractive index layer may be 70 atomic % or more.

[0024]

Concept 3

[0025] In the reflective mask blank based on Concept 1,

[0026] The diffusion prevention layer comprises a first diffusion prevention layer disposed in contact with a side of the low refractive index layer close to the substrate,

[0027] The first diffusion prevention layer comprises a first sub-layer formed in contact with the high refractive index layer and a second sub-layer formed in contact with the low refractive index layer.

[0028] The first sub-layer is a sub-layer including at least one material selected from silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN), and molybdenum carbide (MoC),

[0029] The second sub-layer is a sub-layer containing molybdenum (Mo),

[0030] The thickness of the second sub-layer is greater than or equal to 0.2 nm and less than or equal to 0.8 nm.

[0031]

Concept 4

[0032] In a reflective mask blank based on Concept 3,

[0033] The diffusion prevention layer comprises a second diffusion prevention layer disposed in contact with a side of the low refractive index layer away from the substrate,

[0034] The second diffusion prevention layer includes a layer containing molybdenum (Mo) formed in contact with the low refractive index layer, and the thickness of the layer is not less than 0.2 nm and not more than 0.8 nm.

[0035]

Concept 5

[0036] In a reflective mask blank based on Concept 2,

[0037] The diffusion prevention layer comprises a first diffusion prevention layer disposed in contact with a side of the low refractive index layer close to the substrate,

[0038] The first diffusion prevention layer comprises a first sub-layer formed in contact with the high refractive index layer and a second sub-layer formed in contact with the low refractive index layer.

[0039] The first sub-layer is a sub-layer including at least one material selected from silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN), and molybdenum carbide (MoC),

[0040] The second sub-layer is a sub-layer containing molybdenum (Mo),

[0041] The thickness of the second sub-layer is greater than or equal to 0.2 nm and less than or equal to 0.8 nm.

[0042] Concept 6

[0043] In a reflective mask blank based on Concept 5,

[0044] The diffusion prevention layer comprises a second diffusion prevention layer disposed in contact with a side of the low refractive index layer away from the substrate,

[0045] The second diffusion prevention layer includes a layer containing molybdenum (Mo) formed in contact with the low refractive index layer, and the thickness of the layer is not less than 0.2 nm and not more than 0.8 nm.

[0046]

Concept 7

[0047] The method for manufacturing a reflective mask blank of the present invention,

[0048] The multilayer reflective film of the reflective mask blank according to any one of Concepts 1 to 6 may be formed by a sputtering film forming method using a sputtering device in which a plurality of targets can be installed in a chamber.

[0049] Effects of the Invention

[0050] According to the present invention, in a multilayer reflective film having a structure in which Ru and Si are alternately stacked and which is capable of increasing the contribution of reflection from a position shallower than the surface of the multilayer reflective film, a diffusion prevention layer that effectively prevents mutual diffusion of Ru and Si is provided to prevent a decrease in reflectivity and reduce the 3D effect, thereby obtaining a reflective mask blank capable of producing a mask with a high contrast when transferring a pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1A This is a longitudinal sectional view of an example in which a first diffusion prevention layer and a second diffusion prevention layer are provided in a reflective mask blank according to an embodiment of the present invention.

[0052] Figure 1B 1 is a longitudinal cross-sectional view of an example in which a first diffusion prevention layer and a second diffusion prevention layer including a first sub-layer and a second sub-layer are provided in a reflective mask blank according to an embodiment of the present invention.

[0053] Figure 2 It is a longitudinal sectional view of an example in which a first diffusion prevention layer is provided in a reflective mask blank according to an embodiment of the present invention.

[0054] Figure 3 It is a longitudinal sectional view of an example of the second diffusion prevention layer of the reflective mask blank according to the embodiment of the present invention.

[0055] Figure 4 This is a longitudinal cross-sectional view showing a state in which a pattern of an absorption film is formed in a reflective mask blank according to an embodiment of the present invention.

[0056] Figure 5 This is a longitudinal sectional view showing a state in which an etching mask film is provided in a reflective mask substrate according to an embodiment of the present invention.

[0057] Figure 6 It is a longitudinal sectional view showing a state in which an etching mask film and a resist film are provided on a reflective mask blank according to an embodiment of the present invention.

[0058] Figure 7 It is a longitudinal sectional view showing a state in which a pattern of an etching mask film is formed using a resist pattern as an etching mask in a reflective mask blank according to an embodiment of the present invention.

[0059] Figure 8 is a cross-sectional view of exemplary embodiment 1 of the present invention.

[0060] Fig. 9 These are cross-sectional views of Examples 9 to 12 of the present invention.

[0061] Fig.10 is Figure 1A The longitudinal cross-sectional view of each embodiment shown is an embodiment in which a high refractive index layer is provided as the uppermost layer of the multilayer reflective film. DETAILED DESCRIPTION

[0062] Hereinafter, embodiments of the present invention will be described in more detail.

[0063] The reflective mask blank of the present embodiment includes a substrate 10 and a multilayer reflective film 50 formed on the substrate 10 (on one main surface (surface) of the substrate 10) to reflect exposure light. The reflective mask blank of the present embodiment is suitable for use as a raw material (EUV mask template) of a reflective mask (EUV mask) used in EUV lithography using EUV light as exposure light. The wavelength of EUV light used in EUV lithography using EUV light as exposure light is 13 to 14 nm, and is generally light with a wavelength of about 13.5 nm.

[0064] The substrate 10 is preferably used for EUV light exposure and has low thermal expansion characteristics. For example, the thermal expansion coefficient is preferably within ±2×10 -8 / ℃, preferably within ±5×10 -9 / ℃ range of materials. Examples of such materials include titanium dioxide-doped quartz glass (SiO2-TiO2 glass) and the like. In addition, the substrate 10 preferably uses a substrate with a sufficiently flat surface, and the surface roughness of the main surface of the substrate 10 is preferably less than 0.5nm, more preferably less than 0.2nm, in terms of RMS value. Such surface roughness can be obtained by grinding the substrate 10, etc. The size of the substrate 10 is preferably that the size of the main surface of the substrate 10 is 152mm square, and the thickness of the substrate 10 is 6.35mm. The substrate 10 of this size is a so-called 6025 substrate (a substrate having a main surface size of 6 inches square and a thickness of 0.25 inches).

[0065] The multilayer reflective film 50 is a film that reflects EUV light as exposure light in a reflective mask. The multilayer reflective film 50 may be provided in contact with one main surface of the substrate 10, or a base film (not shown) 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 as exposure light in a reflective mask. The multilayer reflective film 50 has a periodic stacking structure in which a high refractive index layer 20 having a relatively high refractive index for EUV light and a low refractive index layer 30 having a relatively low refractive index for EUV light are alternately stacked. The number of cycles of the periodic stacking structure is preferably 10 cycles or more, particularly preferably 20 cycles or more, preferably 50 cycles or less, particularly preferably 40 cycles or less, and further preferably 30 cycles or less. The reflectivity value is preferably 50% or more, particularly preferably 55% or more, and further preferably 60% or more.

[0066] In addition, the top layer of the multilayer reflective film 50 may also serve as a protective layer having the function of protecting the multilayer reflective film 50. In this case, a high refractive index layer may also be provided on the top layer of the multilayer reflective film 50 (see Fig.10 The high refractive index layer has the function of protecting the multilayer reflective film 50. In this way, when the high refractive index layer is provided on the uppermost layer of the multilayer reflective film 50, the protective film 110 and the absorber film 120 described later are provided on the high refractive index layer.

[0067] The multilayer reflective film 50 of this embodiment has a layer containing silicon (Si) as the high refractive index layer 20 and a layer containing ruthenium (Ru) as the low refractive index layer 30, and further has a diffusion prevention layer 40 for preventing silicon (Si) and ruthenium (Ru) from diffusing each other.

[0068] The high refractive index layer 20 contains silicon (Si) and may contain at least one additive element selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H), and may also be composed of a multilayer containing an additive element layer and a layer not containing the additive element. The thickness of the high refractive index layer 20 is preferably 2.5 nm or more and 5.5 nm or less, more preferably 3 nm or more and 5 nm or less.

[0069] The low refractive index layer 30 is made of a material containing ruthenium (Ru), and may be a simple substance of ruthenium (Ru), an alloy of ruthenium (Ru) and molybdenum (Mo), etc. The ruthenium content of the low refractive index layer 30 is preferably 70 atomic % or more, and more preferably 80 atomic % or more. By increasing the ruthenium content of the low refractive index layer 30, the refractive index of the low refractive index layer 30 can be further reduced, and the contribution to reflection from a position shallower than the surface of the multilayer reflective film 50 can be increased. The thickness of the low refractive index layer 30 is preferably 1 nm or more and 4 nm or less, and more preferably 1.5 nm or more and 3.5 nm or less.

[0070] The diffusion prevention layer 40 has the effect of preventing mutual diffusion of ruthenium (Ru) and silicon (Si), and can be composed of one or more sublayers selected from a layer containing silicon nitride (SiN), a layer containing silicon carbide (SiC), a layer containing molybdenum (Mo), a layer containing molybdenum nitride (MoN), and a layer containing molybdenum carbide (MoC). The diffusion prevention layer 40 may also contain hydrogen (H), boron (B), and oxygen (O). The thickness of the diffusion prevention layer 40 is preferably not less than 0.2nm and not more than 1.3nm.

[0071] The diffusion barrier layer 40 may be provided at any one of the interfaces of the low refractive index layer 30 on the side close to the substrate 10 and the side away from the substrate 10, or at both interfaces, but is preferably provided at both interfaces. In the case where the diffusion prevention layer 40 is provided at both interfaces of the low refractive index layer 30, the number, material, and thickness of the sub-layers constituting the diffusion prevention layer 40 may be the same or different. In addition, the number, material, and thickness of the sub-layers constituting the diffusion prevention layer 40 in each layer of a multilayer reflective film 50 may be the same or different.

[0072] For example, in the case where the anti-diffusion layer 40 includes only one sub-layer, the anti-diffusion layer 40 can be formed in contact with the low refractive index layer 30 on: one or both of the side close to the substrate 10 and the side away from the substrate 10 of at least one low refractive index layer 30 of the multilayer reflective film 50.

[0073] Alternatively, in the case of providing a diffusion prevention layer 40 composed of two sub-layers, a diffusion prevention layer 40 composed of a first sub-layer 46 and a second sub-layer 47 is formed on either or both of the side close to the substrate 10 and the side away from the substrate 10 of at least one low refractive index layer 30 of the multilayer reflective film 50 so as to be in contact with the low refractive index layer 30.

[0074] The diffusion barrier layer 40 is preferably provided on both the side of the low refractive index layer 30 close to the substrate 10 and the side of the low refractive index layer 30 far from the substrate 10 .

[0075] In this embodiment, the diffusion prevention layer 40 disposed on the side of the low refractive index layer 30 close to the substrate 10 is referred to as the first diffusion prevention layer 41. The first diffusion barrier layer 41 is preferably composed of a first sub-layer 46 formed in contact with the high refractive index layer 20 and a second sub-layer 47 formed in contact with the low refractive index layer 30 (see Figure 1B). At this time, it is preferred that the first sublayer 46 is a sublayer containing at least one material selected from silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN) and molybdenum carbide (MoC), and the second sublayer 47 is a sublayer containing molybdenum (Mo). It is effective to use molybdenum (Mo), which is a material that is particularly difficult to form an interdiffusion layer with ruthenium (Ru) and has a low refractive index and a small absorption coefficient of EUV light, as the material of the second sublayer 47. After forming the high refractive index layer 20 containing silicon (Si) and forming the diffusion prevention layer 40 containing molybdenum (Mo), the first sublayer 46 has the effect of preventing molybdenum (Mo) from diffusing into the silicon (Si) layer, and as its material, silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN), molybdenum carbide (MoC), etc. are effective.

[0076] In such a structure, the thickness of the second sublayer 47 is preferably 0.2 nm or more and 0.8 nm or less. This can largely maintain the contribution of reflection from a position shallower than the surface of the multilayer reflective film 50 (the depth of the effective reflection surface becomes shallower).

[0077] In this embodiment, the diffusion prevention layer 40 provided on the side of the low refractive index layer 30 away from the substrate 10 is referred to as a second diffusion prevention layer 42. The second diffusion prevention layer 42 is preferably a layer containing molybdenum (Mo), and from the viewpoint of the reflectivity of the multilayer reflective film 50 or the effective reflection surface depth, the thickness is preferably 0.2 nm or more and 0.8 nm or less.

[0078] As a method for forming the multilayer reflective film 50, there can be listed a sputtering method in which power is supplied to a target, and the atmosphere gas is plasmatized (ionized) with the supplied power to perform sputtering, and an ion beam sputtering method in which an ion beam is irradiated onto a target. As a sputtering method, there is a DC sputtering method in which a direct current voltage is applied to a target, and an RF sputtering method in which a high-frequency voltage is applied to a target. The sputtering method is a film-forming method in which a voltage is applied to a target in a state where a sputtering gas is introduced into a chamber to ionize the gas, and the magnetron sputtering method is particularly advantageous in terms of productivity. The power applied to the target can be DC or RF, and DC also includes pulse sputtering to reverse the negative bias applied to the target for a short time to prevent the target from being charged.

[0079] The multilayer reflective film 50 can be formed by a sputtering method, for example, using a sputtering device that can be equipped with multiple targets. Specifically, as a target, it can be appropriately selected from a ruthenium (Ru) target for forming a ruthenium (Ru) layer, a silicon (Si) target for forming a silicon (Si) layer, a molybdenum (Mo) target for forming a molybdenum (Mo) layer, etc., and as a sputtering gas, it can be formed using rare gases such as neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0080] When forming a layer containing molybdenum carbide (MoC) or a layer containing silicon carbide (SiC), a carbon (C) target can be used simultaneously with a molybdenum (Mo) target or a silicon (Si) target, or a molybdenum (Mo) target to which carbon (C) is added (molybdenum carbide (MoC) target), a silicon (Si) target to which carbon (C) is added (silicon carbide (SiC) target), etc. can be used. Alternatively, a hydrocarbon gas such as methane (CH4) gas can be used together with a rare gas to form a carbon source through reactive sputtering.

[0081] When forming a layer containing molybdenum nitride (MoN) or a layer containing silicon nitride (SiN), it can be formed by reactive sputtering using a nitrogen-containing gas such as nitrogen gas together with a rare gas.

[0082] In addition, when forming a layer containing boron (B), a boron carbide (B4C) target, a molybdenum (Mo) target to which boron (B) is added (molybdenum boride (MoB) target), a silicon (Si) target to which boron (B) is added (silicon boride (SiB) target), etc. can be used.

[0083] A protective film 110 for protecting the multilayer reflective film 50 may be provided on the multilayer reflective film 50 (see FIGS. 1 to 5 ). Figure 7 ). As the material of the protective film 110, a material containing ruthenium (Ru) is preferably used. The protective film 110 is required to have the function of protecting the multilayer reflective film 50 from various dry etching or cleaning in the reflective mask manufacturing process, the exposure environment when the reflective mask is used, or the cleaning treatment in the regeneration process after use. It is preferable to use a material containing niobium (Nb), zirconium (Zr), titanium (Ti), rhodium (Rh) and other additive elements to make it resistant to various processes. In addition, it can also be set to a multilayer structure composed of these materials.

[0084] The protection film 110 may be formed with another film between it and the multilayer reflective film 50 , but is usually formed in contact with the multilayer reflective film 50 .

[0085] The protective film 110 can be formed, for example, by a sputtering method. As a target, 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, a ruthenium (Ru) and niobium (Nb) alloy target, etc. can be appropriately selected for use. The protective film 110 (the layers constituting the protective film 110) is formed by sputtering using a rare gas such as neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas as a sputtering gas, or as a reactive gas, it can be formed by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, and a carbon-containing gas together with a rare gas. As the reactive gas, specifically, oxygen (O2) gas, nitrogen (N2) gas, nitrous oxide (N2O) gas, nitric oxide (NO) gas, nitrogen dioxide (NO2) gas and other nitrogen oxide gases, carbon monoxide (CO) gas, carbon dioxide (CO2) gas and other carbon dioxide gases can be cited. The thickness of the protective film 110 is not particularly limited, and is usually about 2 to 5 nm.

[0086] The reflective mask blank of this embodiment may further include an absorber film 120 that absorbs exposure light and functions as a pattern forming film on the protective film 110 (see FIGS. 1 to 3 ). Figure 7 ). Generally, a reflective mask blank (EUV mask blank) having a substrate 10, a multilayer reflective film 50, a protective film 110, and an absorber film 120 is used, and the absorber film 120 is patterned (see Figure 4 ) to manufacture a reflective mask (EUV mask).

[0087] As such a reflective mask blank, specifically, there can be mentioned a reflective mask blank having a substrate 10, a multilayer reflective film 50 formed on one main surface of the substrate 10 and reflecting the 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 the 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 having a pattern (absorber pattern) of the substrate 10, the multilayer reflective film 50 formed on one main surface of the substrate 10 and reflecting the exposure light, the protective film 110 formed on the multilayer reflective film 50, and the absorber film 120 formed on the protective film 110 and absorbing the exposure light can be manufactured (see Figure 4 ). The absorber film 120 absorbs exposure light, specifically EUV light, to reduce reflectivity.

[0088] As the material of the absorber film 120, there is no limitation as long as it is a material that can absorb EUV light and can be patterned. As the material of the absorber film 120, for example, a material containing tantalum (Ta) or chromium (Cr) can be cited. In addition, the material containing Ta or Cr may also contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. As the material containing Ta, Ta element, TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, TaCONB and other tantalum compounds can be listed. As the material containing Cr, specifically, Cr element, CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB, CrOB, CrNB, CrONB, CrCB, CrCNB, CrCOB, CrCONB and other chromium compounds can be listed.

[0089] The absorber film 120 can be formed by sputtering, and magnetron sputtering is preferred. Specifically, metal targets such as chromium (Cr) targets and tantalum (Ta) targets, metal compound targets such as chromium compound targets and tantalum compound targets (metals such as Cr and Ta, and targets containing oxygen (O), nitrogen (N), carbon (C), boron (B), etc.) can be used. As sputtering gas, neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, xenon (Xe) gas and other rare gas sputtering can be used. In addition, reactive sputtering using reactive gases such as oxygen-containing gas, nitrogen-containing gas, carbon-containing gas, etc. together with the rare gas can be used to form the absorber film 120. There is no particular limitation on the film thickness of the absorber film 120, which is usually about 40 to 80 nm.

[0090] On the side of the absorber film 120 away from the substrate 10, a hard mask film 130 (etching mask film of the absorber film 120) having etching characteristics different from those of the absorber film 120 is preferably provided in contact with the absorber film 120 (see Figure 5). The hard mask film 130 is a film used as an etching mask when the absorber film 120 is dry-etched. After the absorber pattern is formed, the hard mask film 130 is retained, for example, as a reflectivity reducing layer for reducing the reflectivity of the wavelength of light used in inspections such as pattern inspection, and can also be removed as a part of the absorber film 120 without remaining on the reflective mask. As a material of the hard mask film 130, a material containing chromium (Cr) can be cited. The hard mask film 130 formed of a material not containing Cr is particularly suitable for the case where the absorber film 120 is formed of a material containing Ta but not Cr. When a layer (reflectivity reducing layer) that mainly performs the function of reducing the reflectivity of the wavelength of light used in inspections such as pattern inspection is formed on the absorber film 120, the hard mask film 130 can be formed on the reflectivity reducing layer of the absorber film 120. The hard mask film 130 can be formed, for example, by magnetron sputtering. There is no particular limitation on the film thickness of the hard mask film 130, but it is generally about 5 to 20 nm.

[0091] The reflective mask blank may also be provided with a conductive film 150 (see FIGS. 1 to 3 ) on the other main surface (back surface) of the substrate 10, which is opposite to the one main surface, and preferably in contact with the other main surface, for electrostatically chuck the reflective mask to the exposure device. Figure 7 ).

[0092] The thin film resistance of the conductive film 150 is preferably less than 100Ω / □, and there is no particular restriction on the material. As the material of the conductive film 150, for example, a material containing tantalum (Ta) or chromium (Cr) can be cited. In addition, the material containing tantalum (Ta) or chromium (Cr) can contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. As the material containing tantalum (Ta), Ta element, TaO, TaN, TaON, TaC, TaCO, TaCN, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCOB, TaCNB, and other tantalum (Ta) compounds can be cited. As the material containing chromium (Cr), specifically, Cr element, CrO, CrN, CrON, CrC, CrCO, CrCN, CrCON, CrB, CrOB, CrNB, CrONB, CrCB, CrCOB, CrCNB, CrCONB, and other chromium (Cr) compounds can be cited.

[0093] The thickness of the conductive film 150 is not particularly limited as long as it functions as an electrostatic chuck, and is generally about 20 to 300 nm. The thickness of the conductive film 150 is preferably formed so that the film stress is balanced with the multilayer reflective film 50 and the pattern (absorber pattern) of the absorber film 120 after forming the reflective mask, especially 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 may be formed after forming all the films on the multilayer reflective film 50 side of the substrate 10, or 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 portion of the films on the multilayer reflective film 50 side of the substrate 10 is formed. The conductive film 150 may be formed, for example, by magnetron sputtering.

[0094] The reflective mask blank may also be formed with a resist film 140 on the side farthest from the substrate 10 (see Figure 6 In this embodiment, the resist film 140 is preferably an electron beam (EB) resist. In addition, the resist film 140 is preferably removable by SPM cleaning. In addition, Figure 7 The patterned resist film 140 and the hard mask film 130 are shown.

[0095] Figures 4 to 7 The multilayer reflective film 50 shown may be formed using Figure 1A , Figure 1B , Figure 2 and Figure 3 Any of the methods shown. That is, Figures 4 to 7 The multilayer reflective film 50 shown can be Figure 1A and Figure 1B As shown, the high refractive index layer 20, the first diffusion prevention layer 41, the low refractive index layer 30 and the second diffusion prevention layer 42 are arranged as a repeating unit, or as Figure 2 As shown, the high refractive index layer 20, the first diffusion barrier layer 41 and the low refractive index layer 30 are arranged as a repeating unit, and the Figure 3 As shown, the high refractive index layer 20, the low refractive index layer 30 and the second diffusion prevention layer 42 may be arranged as a repeating unit.

[0096] Hereinafter, the present invention will be specifically described by way of Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0097] [Example 1]

[0098] In Example 1, a low thermal expansion glass substrate (SiO2-TiO2 glass substrate) of 152 mm square and 6.35 mm thick can be set as the substrate 10, and multiple targets can be installed, and a sputtering device that can discharge the targets one by one or multiple targets at the same time is used. The target and the main surface of the substrate 10 are made to face each other, and the substrate 10 is rotated while the multilayer reflective film 50 is formed by DC magnetron sputtering. Figure 8 The state of Example 1 is shown in FIG.

[0099] More specifically, a ruthenium (Ru) target and a silicon (Si) target were mounted on a sputtering device, and a substrate 10 was set. First, while argon (Ar) (flow rate: 12 SCCM) was flowed into the chamber, power was applied to the silicon (Si) target, and a 3.5 nm thick silicon (Si) layer was formed as the high refractive index layer 20, and the power application to the silicon (Si) target was stopped. Next, while argon (flow rate: 15 SCCM) and nitrogen (N2) (flow rate: 50 SCCM) were flowed into the chamber, power was applied to the silicon (Si) target, and a 0.5 nm thick silicon nitride (SiN) layer was formed as the first diffusion prevention layer 41 on the side close to the substrate 10 of the low refractive index layer 30, and the power application to the silicon (Si) target was stopped. Next, while argon (flow rate: 15 SCCM) was flowed into the chamber, power was applied to the ruthenium (Ru) target, and a 2.5 nm thick ruthenium (Ru) layer was formed as the low refractive index layer 30, and the power application to the ruthenium (Ru) target was stopped. Next, while argon gas (flow rate: 15 SCCM) and nitrogen gas (N2) (flow rate: 50 SCCM) are flowing in the chamber, power is applied to the silicon (Si) target to form a silicon nitride (SiN) layer with a thickness of 0.5 nm, and the application of power to the silicon (Si) target is stopped. These operations of forming the high refractive index layer 20, the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, the low refractive index layer 30, and the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10 are repeated as a cycle to form a periodic stacking structure. The number of repetitions of the periodic stacking structure is 40 cycles or 20 cycles. In the last cycle, after the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10 is formed, finally, a silicon (Si) layer of 4 nm (at Figure 8 denoted by reference numeral 25) is formed by the above method and serves as a multilayer reflective film 50.

[0100] When the EUV reflectivity of the obtained reflective mask blank composed of the substrate 10 and the multilayer reflective film 50 at a wavelength of 13.1 to 14 nm was measured at an incident angle of 6 degrees, the reflectivity was the maximum at 13.5 nm, and the value at 40 cycles of the periodic stacking structure was 62.6%. In addition, the difference (R40-R20) between the reflectivity (R40) at 40 cycles of the periodic stacking structure and the reflectivity (R20) at 20 cycles was 3.3%.

[0101] [Example 2]

[0102] A periodic stacking structure was formed in the same manner as in Example 1, except that a 4 nm thick silicon (Si) layer was formed as the high refractive index layer 20, and the second diffusion prevention layer 42 on the side away from the substrate 10 of the low refractive index layer 30 was not formed. The number of repetitions of the periodic stacking structure was 40 cycles or 20 cycles. A 4.5 nm silicon (Si) layer was formed as the top layer of the multilayer reflective film 50, and a reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50 was obtained as the multilayer reflective film 50.

[0103] When the EUV reflectivity of the obtained reflective mask blank was evaluated by the same method as in Example 1, the reflectivity was the highest at 13.5 nm, and the value was 62.1% when the periodic stacking structure was repeated 40 times. In addition, the difference (R40-R20) between the reflectivity (R40) at 40 cycles and the reflectivity (R20) at 20 cycles of the periodic stacking structure was 3.0%. Comparison with Example 1 shows that the reflectivity (R40) value is larger when the second diffusion prevention layer 42 is provided.

[0104] [Example 3]

[0105] In addition to installing a ruthenium (Ru) target, a silicon (Si) target, and a molybdenum (Mo) target in a sputtering device to form a 4.5 nm thick silicon (Si) layer as the high refractive index layer 20 and a first diffusion prevention layer 41 on the side close to the substrate 10 as the low refractive index layer 30, while applying power to the molybdenum (Mo) target while flowing argon gas (flow rate: 30 SCCM) into the chamber to form a 0.5 nm thick molybdenum (Mo) layer, a 1.5 nm thick ruthenium (Ru) layer as the low refractive index layer 30, and a low refractive index layer 30, a 1.5 nm thick ruthenium (Ru) layer as the low refractive index layer 30, and a low refractive index layer 30 as the low refractive index layer 30. 30 is a second diffusion prevention layer 42 on the side away from the substrate 10, and while argon gas (flow rate: 30 SCCM) is flowed into the chamber, power is applied to the molybdenum (Mo) target to form a molybdenum (Mo) layer with a thickness of 0.5 nm, and as the uppermost layer of the multilayer reflective film 50, in addition to forming a 4.5 nm silicon (Si) layer on the second diffusion prevention layer 42 on the side away from the substrate 10 of the low refractive index layer 30 in the final cycle, a reflective mask blank is obtained by repeating the periodic stacking structure 20 times in the same manner as in Example 1.

[0106] When the EUV reflectivity of the obtained reflective mask blank was measured by the same method as in Example 1, the reflectivity was the maximum at 13.5 nm, which was 60.2%.

[0107] [Example 4]

[0108] A reflective mask blank was obtained in the same manner as in Example 3, except that a first diffusion prevention layer 41 as the low refractive index layer 30 on the side close to the substrate 10 was formed by applying power to a molybdenum (Mo) target while flowing argon gas (flow rate: 15 SCCM) and nitrogen gas (flow rate: 50 SCCM) into the chamber to form a molybdenum nitride (MoN) layer with a thickness of 0.5 nm, and a second diffusion prevention layer 42 as the low refractive index layer 30 on the side away from the substrate 10 was formed by applying power to a molybdenum (Mo) target while flowing argon gas (flow rate: 15 SCCM) and nitrogen gas (flow rate: 50 SCCM) into the chamber to form a molybdenum nitride (MoN) layer with a thickness of 0.5 nm.

[0109] When the EUV reflectivity of the obtained reflective mask blank was evaluated in the same manner as in Example 1, the reflectivity was the highest at 13.5 nm, which was 59.7%.

[0110] [Example 5]

[0111] A reflective mask blank was obtained in the same manner as in Example 3, except that a molybdenum carbide (MoC) target was used instead of a molybdenum (Mo) target, and electric power was applied to the molybdenum carbide (MoC) target while argon gas (flow rate: 30 SCCM) was flowed into the chamber as the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, thereby forming a molybdenum carbide (MoC) layer with a thickness of 0.5 nm; and electric power was applied to the molybdenum carbide (MoC) target while argon gas (flow rate: 30 SCCM) was flowed into the chamber as the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10, thereby forming a molybdenum carbide (MoC) layer with a thickness of 0.5 nm.

[0112] When the EUV reflectivity of the obtained reflective mask blank was evaluated in the same manner as in Example 1, the reflectivity was the highest at 13.5 nm, which was 61.2%.

[0113] [Examples 6 to 8]

[0114] A periodic stacking structure was formed in the same manner as in Example 1, except that a ruthenium (Ru) target, a silicon (Si) target, and a molybdenum (Mo) target were installed in the sputtering device as the low refractive index layer 30, and while argon gas (flow rate: 15 SCCM) was circulated in the chamber, power was applied to the ruthenium (Ru) target and the molybdenum (Mo) target to form a ruthenium molybdenum (RuMo) alloy layer with a thickness of 2.5 nm. The composition ratio (Ru:Mo) of ruthenium (Ru) and molybdenum (Mo) in the ruthenium molybdenum (RuMo) alloy layer was 3:1 in Example 6, 1:1 in Example 7, and 1:3 in Example 8. The number of repetitions of the periodic stacking structure was 40 cycles or 20 cycles. As the uppermost layer of the multilayer reflective film 50, a 4 nm silicon (Si) layer was formed by the above method, and the multilayer reflective film 50 was formed, thereby obtaining a reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50.

[0115] When the EUV reflectivity of the obtained reflective mask blank was evaluated by the same method as in Example 1, the reflectivity was the highest at 13.5 nm, and the values ​​at 40 cycles of the periodic stacking structure were 64.0% in Example 6, 62.1% in Example 7, and 61.2% in Example 8. In addition, the difference (R40-R20) between the reflectivity (R40) at 40 cycles and the reflectivity (R20) at 20 cycles of the periodic stacking structure was 4.7% in Example 6, 5.7% in Example 7, and 7.4% in Example 8. As can be seen from the comparison between Example 1 and Examples 6 to 8, the higher the ruthenium (Ru) content of the low refractive index layer 30, the smaller the difference between the reflectivity at 40 cycles and the reflectivity at 20 cycles, and therefore the contribution of the reflection from the shallow position on the surface of the multilayer reflective film 50 becomes relatively large. In particular, Examples 1 and 6 in which the ruthenium (Ru) content was 70 atomic % or more showed high reflectance after 20 cycles.

[0116] [Examples 9 to 12]

[0117] A ruthenium (Ru) target, a silicon (Si) target, and a molybdenum (Mo) target were installed on a sputtering device, and a substrate 10 was set. First, while argon (Ar) (flow rate: 12 SCCM) was flowing in 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 power application to the silicon (Si) target was stopped. Next, while argon (flow rate: 15 SCCM) and nitrogen (N2) (flow rate: 50 SCCM) were flowing in the chamber, power was applied to the silicon (Si) target to form a 0.5 nm thick silicon nitride (SiN) layer as the first sublayer 46 of the first diffusion prevention layer 41 on the side close to the substrate 10 of the low refractive index layer 30, and the power application to the silicon (Si) target was stopped. Next, while argon gas (flow rate: 30 SCCM) is flowing in the chamber, power is applied to the molybdenum (Mo) target to form a molybdenum (Mo) layer as the second sublayer 47 of the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, and the application of power to the molybdenum (Mo) target is stopped. Next, while argon gas (flow rate: 15 SCCM) is flowing in the chamber, power is applied to the ruthenium (Ru) target to form a ruthenium (Ru) layer as the low refractive index layer 30, and the application of power to the ruthenium (Ru) target is stopped. Next, while argon gas (flow rate: 30 SCCM) is flowing in the chamber, power is applied to the molybdenum (Mo) target to form a molybdenum (Mo) layer as the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10, and the application of power to the molybdenum (Mo) target is stopped. In addition, Fig. 9 The configurations of Examples 9 to 12 are shown.

[0118] The thickness of the second sublayer 47 (molybdenum (Mo) layer) of the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10 is 0.2 nm in Example 9, 0.5 nm in Example 10, 0.8 nm in Example 11, and 1 nm in Example 12.

[0119] The thickness of the low refractive index layer 30 (ruthenium (Ru) layer) was set to 2.1 nm in Example 9, 1.5 nm in Example 10, 0.9 nm in Example 11, and 0.5 nm in Example 12.

[0120] The thickness of the second diffusion prevention layer 42 (molybdenum (Mo) layer) on the side of the low refractive index layer 30 away from the substrate 10 was 0.2 nm in Example 9, 0.5 nm in Example 10, 0.8 nm in Example 11, and 1 nm in Example 12.

[0121] The operation of forming the high refractive index layer 20, the first sublayer 46 of the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, the second sublayer 47 of the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, the low refractive index layer 30, and the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10 is regarded as one cycle, and a periodic stacking structure is formed by repeating this process. The number of repetitions of the periodic stacking structure is 40 cycles or 20 cycles. After the second diffusion prevention layer 42 on the side of the low refractive index layer 30 away from the substrate 10 is formed in the last cycle, a silicon (Si) layer of 4.5 nm (at Fig. 9 The multilayer reflective film 50 is formed by the above method, and a reflective mask blank composed of the substrate 10 and the multilayer reflective film 50 is obtained.

[0122] When the EUV reflectivity of the obtained reflective mask blank was evaluated by the same method as in Example 1, the reflectivity was maximum at 13.5 nm, and the value at 40 cycles of repetition of the periodic stacking structure was 65.1% in Example 9, 66.5% in Example 10, 66.9% in Example 11, and 66.0% in Example 12. In addition, the difference (R40-R20) between the reflectivity (R40) at 40 cycles of repetition of the periodic stacking structure and the reflectivity (R20) at 20 cycles was 3.7% in Example 9, 4.9% in Example 10, 6.0% in Example 11, and 8.2% in Example 12.

[0123] From the comparison between Examples 2 and 9 to 12, it can be seen that the thicker the molybdenum layer of the diffusion prevention layer 40 is, the greater the difference between the reflectivity at 40 cycles and the reflectivity at 20 cycles is, so the contribution of reflection from a shallower position on the surface of the multilayer reflective film 50 becomes relatively smaller.

[0124] In addition, by setting the thickness of the second sublayer 47 (molybdenum (Mo) layer) of the first diffusion prevention layer 41 on the side of the low refractive index layer 30 close to the substrate 10, and the thickness of the second diffusion prevention layer 42 (molybdenum (Mo) layer) on the side of the low refractive index layer 30 away from the substrate 10 to be greater than 0.2nm and less than 0.8nm, the results show that the reflectivity of the 20-cycle periodic structure and the 40-cycle periodic structure are both particularly high values, which can increase the contribution of reflection from a position shallower than the surface of the multilayer reflective film 50, and has a high effect of preventing interlayer diffusion.

[0125] [Comparative Example 1]

[0126] A periodic stacking structure was formed in the same manner as in Example 1, except that a silicon (Si) layer with a thickness of 4.5 nm was formed as the high refractive index layer 20, a first diffusion prevention layer 41 on the side close to the substrate 10 without forming the low refractive index layer 30, and a second diffusion prevention layer 42 on the side away from the substrate 10 of the low refractive index layer 30. The number of repetitions of the periodic stacking structure was 40 cycles. A silicon (Si) layer with a thickness of 4.5 nm was formed as the uppermost layer of the multilayer reflective film 50, and a reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50 was obtained as the multilayer reflective film 50.

[0127] When the EUV reflectivity of the obtained reflective mask blank was evaluated by the same method as in Example 1, the reflectivity was the highest at 13.5 nm, and the value was 58.7% in Comparative Example 1. Thus, the reflectivity was low without providing the diffusion prevention layer 40. By comparing Examples 1, 3, 4 and 5 with Comparative Example 1, it was found that the diffusion prevention effect of the silicon nitride (SiN) layer, the molybdenum (Mo) layer, the molybdenum nitride (MoN) layer and the molybdenum carbide (MoC) layer resulted in an improvement in reflectivity.

[0128] [Comparative Example 2]

[0129] A molybdenum (Mo) target and a silicon (Si) target were mounted on a sputtering device, and as the low refractive index layer 30, an argon gas (flow rate: 15 SCCM) was flowed into the chamber while applying power to the molybdenum (Mo) target to form a molybdenum (Mo) layer with a thickness of 2.5 nm. A periodic stacking structure was formed in the same manner as in Example 2 except that a 4.5 nm silicon (Si) layer was formed as the top layer of the multilayer reflective film 50, and as the multilayer reflective film 50, a reflective mask blank consisting of the substrate 10 and the multilayer reflective film 50 was obtained.

[0130] The reflectivity difference (R40-R20) between the reflectivity (R40) at 40 cycles and the reflectivity (R20) at 20 cycles of the periodic stacking structure of the obtained reflective mask blank was evaluated by the same method as in Example 1 and the result was 11.7%.

[0131] The difference between the reflectivity of the periodic stacking structure of Comparative Example 2 at the repetition number of 40 cycles and the reflectivity of 20 cycles is relatively large, which means that the contribution of reflection from a position shallower than the surface of the multilayer reflective film 50 is relatively small. In contrast, the periodic stacking structure of Example 2 shows that the difference between the reflectivity of 40 cycles and the reflectivity of 20 cycles is relatively small, and the contribution of reflection from a position shallower than the surface of the multilayer reflective film 50 is relatively large.

[0132] Explanation of symbols

[0133] 10 substrates

[0134] 20 High refractive index layer

[0135] 30 Low refractive index layer

[0136] 40 diffusion barrier

[0137] 41First diffusion barrier

[0138] 42 Second diffusion barrier

[0139] 46 First Sub-layer

[0140] 47 Second Sub-layer

[0141] 50 multi-layer reflective film.

Claims

1. A reflective mask blank, characterized in that: include: substrate; as well as a multilayer reflective film formed on one main surface of the substrate for reflecting exposure light, The multilayer reflective film has a periodic stacked structure in which a low refractive index layer containing ruthenium (Ru), a high refractive index layer containing silicon (Si), and an anti-diffusion layer for preventing mutual diffusion of ruthenium (Ru) and silicon (Si) are periodically stacked. The diffusion prevention layer is formed in contact with the low refractive index layer on both or one of the sides of the low refractive index layer close to the substrate and the side of the low refractive index layer far from the substrate. The diffusion prevention layer is composed of one or more sub-layers selected from a layer containing silicon nitride (SiN), a layer containing silicon carbide (SiC), a layer containing molybdenum (Mo), a layer containing molybdenum nitride (MoN), and a layer containing molybdenum carbide (MoC).

2. The reflective mask blank according to claim 1, characterized in that: The ruthenium content of the low refractive index layer is 70 atomic % or more.

3. The reflective mask blank according to claim 1, characterized in that: The diffusion prevention layer comprises a first diffusion prevention layer disposed in contact with a side of the low refractive index layer close to the substrate, The first diffusion prevention layer comprises a first sub-layer formed in contact with the high refractive index layer and a second sub-layer formed in contact with the low refractive index layer. The first sub-layer is a sub-layer containing at least one material selected from silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN), and molybdenum carbide (MoC), and the second sub-layer is a sub-layer containing molybdenum (Mo). The thickness of the second sub-layer is greater than or equal to 0.2 nm and less than or equal to 0.8 nm.

4. The reflective mask blank according to claim 3, characterized in that: The diffusion prevention layer comprises a second diffusion prevention layer disposed in contact with a side of the low refractive index layer away from the substrate, The second diffusion prevention layer includes a layer containing molybdenum (Mo) formed in contact with the low refractive index layer, and the thickness of the layer is not less than 0.2 nm and not more than 0.8 nm.

5. The reflective mask blank according to claim 2, characterized in that: The diffusion prevention layer comprises a first diffusion prevention layer disposed in contact with a side of the low refractive index layer close to the substrate, The first diffusion prevention layer comprises a first sub-layer formed in contact with the high refractive index layer and a second sub-layer formed in contact with the low refractive index layer. The first sub-layer is a sub-layer containing at least one material selected from silicon nitride (SiN), silicon carbide (SiC), molybdenum nitride (MoN), and molybdenum carbide (MoC), and the second sub-layer is a sub-layer containing molybdenum (Mo). The thickness of the second sub-layer is greater than or equal to 0.2 nm and less than or equal to 0.8 nm.

6. The reflective mask blank according to claim 5, characterized in that: The diffusion prevention layer comprises a second diffusion prevention layer disposed in contact with a side of the low refractive index layer away from the substrate, The second diffusion prevention layer includes a layer containing molybdenum (Mo) formed in contact with the low refractive index layer, and the thickness of the layer is not less than 0.2 nm and not more than 0.8 nm.

7. A method for manufacturing a reflective mask blank, characterized in that: The multilayer reflective film of the reflective mask blank according to any one of claims 1 to 6 is formed by a sputtering film forming method using a sputtering device capable of mounting a plurality of targets in a chamber.

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