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

Abstract

The objective of this invention is to provide a substrate with a multilayer reflective film for manufacturing a reflective mask having a protective film with high resistance to etching gases and high resistance to cleaning. To this end, the substrate with a multilayer reflective film of this invention comprises a substrate, a multilayer reflective film disposed on the substrate, and a protective film disposed on the multilayer reflective film, wherein the protective film contains ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf), and the content of the additive material is 5 atomic% or more and less than 50 atoms.

Description

[0001] This application is a divisional application of the application filed on September 30, 2020, with application number 202011059191.0 and entitled "Substrate with Multilayer Reflective Film, Reflective Mask Blank, Reflective Mask and Manufacturing Method, and Semiconductor Device Manufacturing Method". Technical Field

[0002] This invention relates to reflective masks used in the manufacture of semiconductor devices, as well as substrates with multilayer reflective films and reflective mask blanks used in the manufacture of reflective masks. Furthermore, this invention relates to a method for manufacturing a semiconductor device using the aforementioned reflective mask. Background Technology

[0003] With the increasing demands for higher density and precision in ultra-low light index (ULI) equipment in recent years, EUV lithography, an exposure technology that uses extreme ultraviolet (EUV) light, has become highly anticipated. EUV light refers to light in the soft X-ray region or vacuum ultraviolet region, specifically light with a wavelength of approximately 0.2 to 100 nm.

[0004] Reflective masks include: a multilayer reflective film formed on a substrate for reflecting exposure light, and an absorber pattern formed on the multilayer reflective film as a patterned absorber film for absorbing exposure light. Light incident on the reflective mask mounted in an exposure machine for pattern transfer on a semiconductor substrate is absorbed in the areas with the absorber pattern and reflected by the multilayer reflective film in the areas without the absorber pattern. The image of the light reflected by the multilayer reflective film is then transferred onto a semiconductor substrate such as a silicon wafer after passing through a reflective optical system.

[0005] In order to achieve high density and high precision in semiconductor devices using reflective masks, the reflective areas (the surface of the multilayer reflective film) in the reflective mask need to have high reflectivity to EUV light, which is used as the exposure light.

[0006] As a multilayer reflective film, a multilayer film with elements of different refractive indices is usually used. For example, as a multilayer reflective film for EUV light with wavelengths of 13 to 14 nm, a Mo / Si periodic laminated film with approximately 40 alternating Mo and Si films can be preferred.

[0007] As a reflective photomask used in EUV lithography, there is, for example, the reflective photomask described in Patent Document 1. Patent Document 1 describes a reflective photomask comprising: a substrate, a reflective layer formed on the substrate, a buffer layer formed of a ruthenium film formed on the reflective layer, and an absorber pattern having a given pattern shape formed on the buffer layer. The reflective layer is formed of a multilayer film having two different films alternately stacked, and the absorber pattern is formed of a material capable of absorbing soft X-rays. The buffer layer described in Patent Document 1 is generally also referred to as a protective film.

[0008] Patent Document 2 discloses a substrate with a multilayer reflective film, wherein the substrate has a multilayer reflective film on the substrate to reflect exposure light. Furthermore, Patent Document 2 discloses that a protective film for protecting the multilayer reflective film is formed on the multilayer reflective film, and that the protective film is formed by sequentially stacking a reflectivity reduction suppression layer, a blocking layer, and an etch stop layer. Additionally, Patent Document 2 discloses that the etch stop layer is formed of ruthenium (Ru) or an alloy thereof, and that specific examples of ruthenium alloys include ruthenium-niobium (RuNb) alloy, ruthenium-zirconium (RuZr) alloy, ruthenium-rhodium (RuRh) alloy, ruthenium-cobalt (RuCo) alloy, and ruthenium-rhenium (RuRe) alloy.

[0009] Patent documents 3 and 4 disclose a substrate with a multilayer reflective film, comprising a substrate, a multilayer reflective film, and a Ru-based protective film formed on the multilayer reflective film for protecting the multilayer reflective film. Patent documents 3 and 4 also disclose that the surface layer of the multilayer reflective film on the side opposite to the substrate is a Si-containing layer.

[0010] Patent Document 3 describes a barrier layer between the multilayer reflective film and the Ru-based protective film that prevents Si from transferring to the Ru-based protective film. Patent Document 3 describes that Ru and its alloys can be listed as constituent materials of the Ru-based protective film 18, and that Ru alloys preferably contain Ru and at least one metal element selected from Nb, Zr, Rh, Ti, Co and Re.

[0011] In addition, Patent Document 4 describes a Ru-based protective film containing a Ru compound containing Ru and Ti, and the Ru compound contains more Ru than the stoichiometric composition of RuTi.

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: Japanese Patent Application Publication No. 2002-122981

[0015] Patent Document 2: Japanese Patent Application Publication No. 2014-170931

[0016] Patent Document 3: International Publication No. 2015 / 012151

[0017] Patent Document 4: International Publication No. 2015 / 037564 Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] In the manufacturing process of reflective masks, the absorber film is etched through a resist film and / or an etch mask film while forming the absorber pattern. To ensure the absorber pattern conforms to the design, some over-etching is required during the etching of the absorber film. Therefore, the film beneath the absorber film (the film on the substrate side) is also etched. To prevent damage to the multilayer reflective film beneath the absorber film during over-etching, a protective film can be applied. Therefore, the protective film must have high resistance to the etching gases emitted by the absorber film.

[0020] Materials used for protective films with high resistance to etching gases on the absorber film include, for example, Ru or RuNb. When the etching mask film formed on the absorber film is a Cr-based material, a mixture of chlorine and oxygen is used as the etching gas to peel it off. The protective films of Ru and RuNb have low resistance to oxygen-containing mixtures. Therefore, the multilayer reflective film formed beneath the protective film may be damaged during the peeling off of the etching mask film. Furthermore, the protective film damaged during the peeling off process may become insufficiently resistant to subsequent absorber pattern correction processes.

[0021] In EUV lithography, a technique used in semiconductor device manufacturing, there are few materials that are transparent to the exposure light. Therefore, the EUV protective film used to prevent foreign matter adhesion to the patterned surface of reflective masks is technically complex. Furthermore, EUV lithography can cause exposure contamination, such as carbon film deposition or oxide film growth, due to EUV exposure. Therefore, during the stage of using the mask in semiconductor device manufacturing, it is necessary to repeatedly clean the mask using cleaning solutions such as sulfuric acid / hydrogen peroxide (SPM) to remove foreign matter and contaminants. However, protective films for Ru and RuNb exhibit insufficient resistance to SPM cleaning.

[0022] Films made of Ru and RuNb are prone to crystallization and exhibit high crystallinity. Compared to amorphous films, highly crystalline films are less dense. Therefore, it can be considered that protective films made of Ru and RuNb may have problems such as low resistance to given etching gases and insufficient resistance to cleaning processes such as SPM cleaning.

[0023] Therefore, an object of the present invention is to provide a reflective mask having a protective film with high resistance to etching gases and high resistance to cleaning. Furthermore, an object of the present invention is to provide a substrate with a multilayer reflective film and a reflective mask blank for manufacturing a reflective mask, the reflective mask having a protective film with high resistance to etching gases and high resistance to cleaning.

[0024] Problem Solving Methods

[0025] To address the above problems, the present invention includes the following solutions.

[0026] (Option 1)

[0027] Solution 1 of the present invention relates to a substrate with a multilayer reflective film, comprising: a substrate, a multilayer reflective film disposed on the substrate, and a protective film disposed on the multilayer reflective film.

[0028] The protective film contains ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf), wherein the content of the additive material is more than 5 atomic% and less than 50 atomic%.

[0029] (Option 2)

[0030] Scheme 2 of the present invention relates to the substrate with multilayer reflective film described in Scheme 1, wherein,

[0031] The aforementioned protective film comprises a first layer and a second layer from the substrate side.

[0032] The first layer contains ruthenium (Ru) and at least one element selected from magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf), and tungsten (W).

[0033] The second layer mentioned above contains the aforementioned ruthenium (Ru) and the aforementioned additives.

[0034] (Option 3)

[0035] Scheme 3 of the present invention relates to a substrate with a multilayer reflective film of Scheme 1 or 2, wherein the protective film, the first layer or the second layer further contains nitrogen (N).

[0036] (Option 4)

[0037] Scheme 4 of the present invention relates to a substrate with a multilayer reflective film as described in any one of Schemes 1 to 3, wherein the Ru content of the second layer is less than the Ru content of the first layer.

[0038] (Option 5)

[0039] Scheme 5 of the present invention relates to a reflective mask blank having an absorber film on a protective film of a substrate with a multilayer reflective film as described in any one of Schemes 1 to 4.

[0040] (Option 6)

[0041] Solution 6 of the present invention relates to the reflective mask blank of Solution 5, which includes an etched mask film on the absorber film, the etched mask film containing chromium (Cr).

[0042] (Option 7)

[0043] Scheme 7 of the present invention relates to a reflective mask comprising an absorber pattern, which is obtained by patterning the absorber film in the reflective mask blank of Scheme 5 or 6.

[0044] (Option 8)

[0045] Solution 8 of the present invention relates to a method for manufacturing a reflective mask, the method comprising:

[0046] The etched mask film of the reflective mask blank in Scheme 6 is patterned to form an etched mask pattern;

[0047] Using the above-mentioned etching mask pattern as a mask, the above-mentioned absorber film is patterned to form an absorber pattern;

[0048] The etched mask pattern is removed using a mixture of chlorine-based gases and oxygen.

[0049] (Option 9)

[0050] Solution 9 of the present invention relates to a method for manufacturing a semiconductor device, the method comprising the following steps:

[0051] The reflective mask of Scheme 7 is placed in an exposure device with an exposure light source that emits EUV light to transfer a pattern onto the resist film formed on the substrate to be transferred.

[0052] The effects of the invention

[0053] According to the present invention, a reflective mask having a protective film with high resistance to etching gases and high resistance to cleaning can be provided. Furthermore, according to the present invention, a substrate with a multilayer reflective film and a reflective mask blank for manufacturing a reflective mask having a protective film with high resistance to etching gases and high resistance to cleaning can be provided. Attached Figure Description

[0054] Figure 1 This is a cross-sectional schematic diagram of an example of a substrate with a multilayer reflective film according to this embodiment.

[0055] Figure 2 This is a cross-sectional schematic diagram of another example of a substrate with a multilayer reflective film according to this embodiment.

[0056] Figure 3 This is a cross-sectional schematic diagram of an example of a reflective mask blank according to this embodiment.

[0057] Figure 4 This is a cross-sectional schematic diagram of another example of a reflective mask blank in this embodiment.

[0058] Figure 5 The graph shows the relationship between the Rh content and the etching rate of the protective film using the mixed gas.

[0059] Figure 6 This is a graph showing the measurement results of the diffraction X-ray intensity (CPS) relative to the diffraction angle 2θ.

[0060] Figure 7 This is a graph showing the results of the measurement of the diffraction X-ray intensity (CPS) relative to the diffraction angle 2θ for a nitrogen (N) introduced film during film formation.

[0061] Figure 8 The cross-sectional schematic diagram shows a process diagram of an example of the manufacturing method of the reflective mask of this embodiment.

[0062] Symbol Explanation

[0063] 1. Mask blank substrate (substrate)

[0064] 2. Back conductive film

[0065] 5. Multilayer reflective film

[0066] 6. Protective film

[0067] 7 Absorbent membrane

[0068] 7a Absorber Pattern

[0069] 8. Anti-corrosion film

[0070] 8a Anti-corrosion pattern

[0071] 9. Etching mask film

[0072] 9a Etched Mask Pattern

[0073] 62 First Floor

[0074] 64. Second Floor

[0075] 100 Reflective Mask Blank

[0076] 110 Substrate with multilayer reflective film

[0077] 200 reflective mask Detailed Implementation

[0078] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments are for the purpose of specifically describing the present invention, and the present invention is not limited thereto.

[0079] Figure 1 This is a cross-sectional schematic diagram showing an example of a substrate 110 with a multilayer reflective film according to this embodiment. Figure 1 The substrate 110 shown has a multilayer reflective film 5 and a protective film 6. It should be noted that the substrate 110 with the multilayer reflective film may further have other thin films such as a back conductive film 2.

[0080] Figure 2 Is with Figure 1 A cross-sectional schematic diagram of the same substrate 110 with multi-layer reflective films. However... Figure 2 In the substrate 110 with multilayer reflective film shown, the protective film 6 includes a first layer 62 and a second layer 64.

[0081] Figure 3 This is a cross-sectional schematic diagram showing an example of the reflective mask blank 100 of this embodiment. Figure 3 The reflective mask blank 100 shown includes a back conductive film 2, a multilayer reflective film 5, a protective film 6, and an absorber film 7. It should be noted that the reflective mask blank 100 may further include other thin films such as a resist film 8.

[0082] Figure 4 It shows except Figure 3 The diagram shows a cross-sectional view of an example of a reflective mask blank 100 that further includes an etching mask film 9 in addition to the configuration shown. It should be noted that the reflective mask blank 100 may further include other thin films such as a resist film 8.

[0083] In this specification, the main surface of the substrate 1 for which the multilayer reflective film 5 is to be formed is sometimes referred to as the "front-side main surface" (or "first main surface"). Additionally, the main surface on which the multilayer reflective film 5 is not formed is sometimes referred to as the "back-side main surface" (or "second main surface"). A back conductive film 2 may be formed on the "back-side main surface" (or "second main surface").

[0084] In this specification, the phrase "having a given thin film on the main surface of the mask blank substrate 1" includes not only the case where the given thin film is grounded to the main surface of the mask blank substrate 1, but also the case where other films are present between the mask blank substrate 1 and the given thin film. Similarly, the phrase "having a film B on film A" includes not only the case where film A and film B are arranged in direct contact, but also the case where other films are present between film A and film B. Furthermore, in this specification, for example, "the surfaces of film A and film B are grounded" means arranged in such a way that film A and film B are in direct contact without any other films being inserted between film A and film B.

[0085] Next, the surface roughness (Rms) will be explained as a parameter characterizing the surface morphology of the substrate 1 for the mask blank and the surface morphology of the thin film constituting the reflective mask blank 100, etc.

[0086] Rms (Root mean square), a representative index of surface roughness, is the square root of the value obtained by averaging the squares of the deviations from the mean line to the measured curve. Rms is represented by the following equation (1).

[0087] [Mathematical Expression 1]

[0088]

[0089] In equation (1), l is the reference length and Z is the height from the average line to the measured curve.

[0090] Rms has previously been used to manage the surface roughness of substrate 1 for mask blanks, and the surface roughness can be controlled numerically.

[0091] <Substrate 110 with multilayer reflective film>

[0092] The substrate 1 and each thin film of the substrate 110 with a multilayer reflective film, which constitutes a type of thin film substrate 1 in this embodiment, will be described.

[0093] <<Substrate 1>>

[0094] In this embodiment, the substrate 1 of the substrate 110 with a multilayer reflective film needs to prevent deformation of the absorber pattern 7a caused by heat during EUV exposure. Therefore, as the substrate 1, it is preferable to use a substrate with a low coefficient of thermal expansion in the range of 0±5 ppb / ℃. As a material with a low coefficient of thermal expansion in this range, for example, SiO2-TiO2 type glass, multi-component glass ceramics, etc., can be used.

[0095] For the first main surface (surface main surface) of the substrate 1 on the side where the transfer pattern (composed of the absorber film 7 described later) is to be formed, surface processing should be performed to achieve a given flatness, at least from the viewpoint of obtaining pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness in the 132mm × 132mm region of the first main surface of the substrate 1 on the side where the transfer pattern is to be formed is preferably 0.1μm or less, more preferably 0.05μm or less, and even more preferably 0.03μm or less. Furthermore, the second main surface (back main surface), which is the side opposite to the side where the absorber film 7 is to be formed, is the surface that is electrostatically attracted when disposed in the exposure apparatus. The flatness of the second main surface in the 132mm × 132mm region is preferably 0.1μm or less, more preferably 0.05μm or less, and even more preferably 0.03μm or less. It should be noted that the flatness of the second main surface of the reflective mask blank 100 in a 142mm×142mm area is preferably less than 1μm, more preferably less than 0.5μm, and even more preferably less than 0.3μm.

[0096] Furthermore, the surface smoothness of the substrate 1 is also a very important factor. The surface roughness of the first main surface of the absorber pattern 7a to be formed for transfer is preferably 0.15 nm or less in terms of root mean square roughness (Rms), more preferably 0.10 nm or less in terms of Rms. It should be noted that the surface smoothness can be measured using an atomic force microscope.

[0097] Furthermore, to prevent deformation caused by film stress of the film (such as the multilayer reflective film 5) formed on the substrate 1, it is preferable that the substrate 1 has high rigidity. It is particularly preferable that the substrate 1 has a high Young's modulus of 65 GPa or higher.

[0098] <<Basement membrane>>

[0099] In this embodiment, the substrate 110 with a multilayer reflective film can have a base film in contact with the surface of the substrate 1. The base film is a thin film formed between the substrate 1 and the multilayer reflective film 5. By having a base film, charging can be prevented when using an electron beam to inspect mask pattern defects, and the multilayer reflective film 5 has fewer phase defects, resulting in high surface smoothness.

[0100] As the material for the base film, materials containing ruthenium or tantalum as the main component are preferred. For example, it can be elemental Ru or elemental Ta, or Ru alloys or Ta alloys containing metals such as titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and / or rhenium (Re). The thickness of the base film is preferably in the range of 1 nm to 10 nm.

[0101] <<Multilayer Reflective Film 5>>

[0102] The substrate 110 with a multilayer reflective film in the embodiment includes a multilayer reflective film 5. The multilayer reflective film 5 provides the function of reflecting EUV light in the reflective mask 200. The multilayer reflective film 5 is a multilayer film formed by periodically stacking layers of elements with different refractive indices as the main components.

[0103] Generally speaking, as a multilayer reflective film 5, a multilayer film can be formed by alternately stacking thin films (high refractive index layer) of light elements or their compounds as high refractive index materials and thin films (low refractive index layer) of heavy elements or their compounds as low refractive index materials for about 40 to 60 cycles.

[0104] The multilayer film used as the multilayer reflective film 5 can be stacked in multiple cycles, with a high refractive index layer and a low refractive index layer stacked sequentially from the substrate 1 side as one cycle, or in multiple cycles, with a low refractive index layer and a high refractive index layer stacked sequentially from the substrate 1 side as one cycle. It should be noted that it is preferable to set the outermost layer of the multilayer reflective film 5, i.e., the surface layer of the multilayer reflective film 5 on the side opposite to the substrate 1 side, as a high refractive index layer. In the above-described multilayer film, when the high refractive index layer and low refractive index layer stacked sequentially from the substrate 1 side is stacked in multiple cycles as one cycle, the uppermost layer is a low refractive index layer. In this case, when the low refractive index layer constitutes the outermost surface of the multilayer reflective film 5, oxidation is likely to occur, resulting in a reduction in the reflectivity of the reflective mask 200. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 5. On the other hand, in the aforementioned multilayer film, when multiple cycles are stacked with a low-refractive-index layer and a high-refractive-index layer sequentially stacked from the substrate 1 side, the topmost layer is a high-refractive-index layer. Therefore, in this case, it is not necessary to form a further high-refractive-index layer.

[0105] As a high refractive index layer, a layer containing silicon (Si) can be used. Besides elemental Si, Si compounds containing boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H) can also be used as the Si-containing material. By using a high refractive index layer containing Si, a reflective mask 200 with excellent EUV light reflectivity can be obtained. Alternatively, as a low refractive index layer, elemental metals selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, can be used. Furthermore, boron (B), carbon (C), nitrogen (N), oxygen (O), and / or hydrogen (H) can be added to these elemental metals or alloys. In the substrate 110 with multilayer reflective films of this embodiment, a molybdenum (Mo) layer is preferably used as the low refractive index layer, and a silicon (Si) layer is preferably used as the high refractive index layer. As a multilayer reflective film 5 for reflecting EUV light with wavelengths of, for example, 13 nm to 14 nm, a Mo / Si periodic laminated film formed by alternating Mo and Si layers for approximately 40 to 60 cycles is preferably used. It should be noted that a high refractive index layer can be formed from silicon (Si) as the uppermost layer of the multilayer reflective film 5, and a silicon oxide layer containing silicon and oxygen can be formed between the uppermost layer (Si) and the protective film 6. With this structure, mask cleaning resistance can be improved.

[0106] The reflectivity of the multilayer reflective film 5 is typically above 65%, with an upper limit of 73%. It should be noted that the film thickness and period of each constituent layer of the multilayer reflective film 5 can be appropriately selected based on the exposure wavelength. Specifically, the film thickness and period of each constituent layer of the multilayer reflective film 5 can be selected in a manner that satisfies Bragg's law of reflection. In the multilayer reflective film 5, there are multiple high-refractive-index layers and multiple low-refractive-index layers, but the film thickness between high-refractive-index layers or between low-refractive-index layers does not necessarily have to be the same. Furthermore, the film thickness of the outermost Si layer of the multilayer reflective film 5 can be adjusted within a range that does not reduce reflectivity. The film thickness of the outermost Si (high-refractive-index layer) can be 3nm to 10nm.

[0107] The method for forming the multilayer reflective film 5 is well known in the art; for example, it can be formed by depositing the layers using ion beam sputtering. In the case of the Mo / Si periodic stacked film described above, for example, by ion beam sputtering, a Si film with a thickness of about 4 nm is first deposited on the substrate 1 using a Si target, and then a Mo film with a thickness of about 3 nm is deposited using a Mo target. This is considered one cycle, and the layers are stacked for 40 to 60 cycles to form the multilayer reflective film 5 (with the outermost layer being a Si film). It should be noted that, although the number of steps increases when the number of cycles is set to 60, compared to 40 cycles, the reflectivity for EUV light can be improved.

[0108] <<Protective Film 6>>

[0109] like Figure 1 and Figure 2 As shown, the substrate 110 with a multilayer reflective film in this embodiment has a protective film 6 on the multilayer reflective film 5. By having a protective film 6 on the multilayer reflective film 5, damage to the surface of the multilayer reflective film 5 can be suppressed when manufacturing the reflective mask 200 using the substrate 110 with the multilayer reflective film. Therefore, the reflective mask 200 obtained has good reflectivity characteristics for EUV light.

[0110] The protective film 6 of this embodiment contains ruthenium (Ru) and an additive. The additive is selected from at least one material chosen from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf). Films made of Ru are prone to crystallization and have high crystallinity. Highly crystalline films are less dense than amorphous films. Therefore, by including the additive in the protective film 6, the density of the protective film 6 can be improved, as well as its resistance to etching gases and its resistance to cleaning. It should be noted that this protective film 6 corresponds to the second layer 64 described later. As will be described later, in addition to the protective film 6 corresponding to the second layer 64, the protective film 6 may further include a first layer 62 (for example, see...). Figure 2 ).

[0111] In this embodiment, the content of the additive material in the protective film 6 is 5 atomic% or more and less than 50 atomic%. The content of the additive material is preferably 10 atomic% or more, more preferably 20 atomic% or more. Furthermore, the content of the additive material is preferably 40 atomic% or less, more preferably 35 atomic% or less. By adjusting the amount of additive material, a protective film 6 with high resistance to etching gases and SPM cleaning, and without significantly reducing EUV reflectivity, can be formed. Therefore, by keeping the content of the additive material in the protective film 6 within a given range, the reduction in EUV light reflectivity of the multilayer reflective film 5 with the protective film 6 can be suppressed, and resistance to etching gases and cleaning can be improved. Furthermore, for additive materials with an extinction coefficient k higher than that of ruthenium (Ru), it is preferable to adjust the extinction coefficient of the protective film 6 to be 0.030 or less, more preferably 0.025 or less.

[0112] The content of the additive material in the aforementioned protective film 6 can be the same as the content of the additive material in the second layer 64 described later. That is, the content of the additive material in the second layer 64 can be 5 atomic% or more and less than 50 atomic%. Furthermore, the content of the additive material is preferably 10 atomic% or more, more preferably 20 atomic% or more. Additionally, the content of the additive material is preferably 40 atomic% or less, more preferably 35 atomic% or less.

[0113] Next, we will describe the cases where the additives contained in the protective film 6 are aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf). It should be noted that the protective film 6 described below can be the second layer 64 described later.

[0114] When aluminum (Al) is added to ruthenium (Ru) as an additive (e.g., in the case of a RuAl film), the etching resistance of the protective film 6 against a mixture of chlorine and oxygen gases, its etching resistance against fluorine gases, and its resistance to cleaning with a sulfuric acid / hydrogen peroxide solution (SPM) are improved. If the Al concentration in the protective film 6 is too low, the additive effect is not achieved; if it is too high, the extinction coefficient of the protective film 6 for EUV light increases, and the reflectivity of the reflective mask 200 decreases. Furthermore, if the Al concentration is too high, its resistance to fluorine gases decreases. Therefore, the Al concentration in the protective film 6 is preferably 5 atomic% or more and 40 atomic% or less, more preferably 10 atomic% or more and 25 atomic% or less.

[0115] When yttrium (Y) is added to ruthenium (Ru) as an additive (e.g., in the case of a RuY film), the etching resistance of the protective film 6 against a mixture of chlorine and oxygen gases, as well as against fluorine gases, increases. If the concentration of Y in the protective film 6 is too low, the additive effect is not achieved; if it is too high, the cleaning resistance of the protective film 6 to a sulfuric acid / hydrogen peroxide (SPM) solution decreases. Therefore, the concentration of Y in the protective film 6 is preferably 5 atomic% or more and less than 50 atomic%, more preferably 10 atomic% or more and less than 40 atomic%.

[0116] When zirconium (Zr) is added to ruthenium (Ru) as an additive (e.g., in the case of a RuZr film), the etching resistance of the protective film 6 relative to a mixture of chlorine-based and oxygen gases is improved. If the Zr concentration in the protective film 6 is too low, the additive effect is not achieved; if it is too high, the cleaning resistance of the protective film 6 to a sulfuric acid / hydrogen peroxide (SPM) solution decreases. Furthermore, if the Zr concentration is too high, the resistance relative to chlorine-based gases decreases. Therefore, the Zr concentration in the protective film 6 is preferably 5 atomic% or more and 45 atomic% or less, more preferably 10 atomic% or more and 25 atomic% or less.

[0117] When rhodium (Rh) is added to ruthenium (Ru) as an additive (e.g., in the case of a RuRh film), the etching resistance of the protective film 6 to a mixture of chlorine and oxygen gases, the etching resistance to chlorine gases, the etching resistance to fluorine gases, and the cleaning resistance to a sulfuric acid / hydrogen peroxide (SPM) solution are improved. If the Rh concentration in the protective film 6 is too low, the additive effect is not achieved; if it is too high, the extinction coefficient k of the protective film 6 for EUV light becomes high, thus reducing the reflectivity of the reflective mask 200. Therefore, the Rh concentration in the protective film 6 is preferably 15 atomic% or more and less than 50 atomic%, more preferably 20 atomic% or more and less than 40 atomic%.

[0118] Figure 5 The diagram illustrates the relationship between the Rh content (atomic %) and the etching rate (nm / s) of the protective film using a mixed gas (Cl2 + O2) when Rh is added as an additive to Ru. When the Rh content reaches 20 atomic % or higher, the rate of decrease in etching rate begins to decrease; when it reaches 30 atomic % or higher, this tendency increases; and when it reaches 50 atomic % or higher, the etching rate hardly changes. Therefore, it can be seen that increasing the Rh content can improve the etching resistance of the protective film. Thus, it is preferable to increase the Rh content until the rate of decrease in etching rate begins to decrease. However, since the etching rate hardly changes when the Rh content exceeds 50 atomic %, it is not necessary to set the Rh content above this value. Furthermore, as the Rh content increases, the reflectivity decreases; when the Rh content exceeds 50 atomic %, the desired reflectivity cannot be obtained. Therefore, the Rh content is preferably less than 50 atomic %. Thus, based on the insights gained, and considering the improved etching resistance and reduced reflectivity resulting from the addition of Rh, an excellent substrate with a multilayer reflective film can be obtained.

[0119] When the protective film 6 (or the second layer 64) contains ruthenium (Ru) and rhodium (Rh), the following conditions are preferred. In this specification, the peaks detected by X-ray diffraction refer to the peaks whose measured X-ray intensity using CuKα rays is plotted relative to the diffraction angle 2θ. These peaks can be selected where the height of the peak after subtracting the background from the measured data (diffraction X-ray spectrum) is more than twice the noise level (amplitude of noise in the height direction) of the background near the peak. The diffraction angle 2θ of the peak can be set to the diffraction angle 2θ (the angle between the incident X-ray direction and the diffracted X-ray direction) of the peak with the maximum displayed value after subtracting the background from the measured data.

[0120] Figure 6The results show the X-ray diffraction intensity (CPS) (vertical axis) of ruthenium (Ru) single films (indicated by crystallization directions in parentheses), rhodium (Rh) single films, and RuRh films (formed at Ru:Rh ratios of 70:30, 50:50, and 30:70) relative to a diffraction angle 2θ (horizontal axis) obtained by using CuKα X-ray diffraction. Both ruthenium (Ru) and rhodium (Rh) single films showed high CPS relative to a diffraction angle 2θ, indicating that they possess high crystallinity. The CPS of the RuRh film relative to a diffraction angle 2θ changed depending on the Ru:Rh ratio, with the lowest CPS at Ru:Rh = 30:70. Therefore, in RuRh films, the higher the Rh content, the lower the crystallinity and the higher the density. However, as the Rh content increases, the reflectivity decreases. When the Rh content exceeds 50 atomic%, the desired reflectivity cannot be obtained. Therefore, as mentioned above, it is preferable that the Rh content is less than 50 atomic%.

[0121] In addition, such as Figure 6 As shown, when Ru:Rh = 70:30, the diffraction angle is 42.0 degrees and the half-maximum width at half maximum (WHM) is 0.62; when Ru:Rh = 50:50, the diffraction angle is 41.9 degrees and the WHM is 0.64; and when Ru:Rh = 30:70, the diffraction angle is 41.7 degrees and the WHM is 0.75.

[0122] Preferably, the peak has a diffraction angle 2θ between 41.0° and 43.0°, and the half-width at half-maximum (WHM) of this peak is 0.6° or higher. This is because the WHM of a single ruthenium (Ru(002)) film is less than 0.6°. Therefore, when the WHM is less than 0.6°, the crystallinity increases, which is not preferred. When the WHM is less than 0.6°, the crystallinity increases and the compactness disappears, thus reducing the etching resistance and cleaning resistance.

[0123] In this way, crystallinity can be controlled based on the range of the diffraction angle 2θ and the full width at half maximum (FWHM) of the peak. By controlling crystallinity, resistance to a given etching gas can be improved, as well as resistance to cleaning by SPM and the like. The diffraction angle 2θ is preferably 41.0 degrees or more, more preferably 41.3 degrees or more. Furthermore, the diffraction angle 2θ is preferably 43.0 degrees or less, more preferably 42.0 degrees or less. The FWHM of the peak is preferably 0.6 degrees or more, more preferably 0.65 degrees or more. Furthermore, the FWHM of the peak is preferably 0.8 degrees or less.

[0124] Figure 7The figure shows the results obtained by measuring the diffraction X-ray intensity (CPS) relative to the diffraction angle 2θ of three nitrogen (N) introduced into the film using CuKα X-ray diffraction during the formation of RuRh films (Ru:Rh = 70:30) (N introduction amounts were set to 3 sccm, 6 sccm, and 12 sccm, respectively). Figure 7 As shown, with an N content of 3 sccm, the diffraction angle is 41.9 degrees and the full width at half maximum (FWHM) is 0.68; with an N content of 6 sccm, the diffraction angle is 41.8 degrees and the FWHM is 0.68; and with an N content of 12 sccm, the diffraction angle is 41.6 degrees and the FWHM is 0.78. Regarding other films, [the text abruptly ends here]. Figure 6 The measurement results were the same. The diffraction angle 2θ of the RuRh film (Ru:Rh = 70:30) is theoretically expected to be 41.8 degrees. It is known that adding nitrogen can improve the compactness of the protective film and make the diffraction angle 2θ of the protective film peak closer to this 41.8 degrees. By making the diffraction angle 2θ of the protective film peak closer to this 41.8 degrees, the residual stress in the protective film can be reduced.

[0125] Therefore, when the protective film 6 (or the second layer 64) contains ruthenium (Ru) and rhodium (Rh), it is preferable that the protective film further contains nitrogen (N). By containing N, the crystallinity of the protective film can be reduced, thereby increasing its density. In addition, by having nitrogen present at the interface between the protective film and the films on and / or under the protective film, and by reducing residual stress in the protective film, their adhesion can be improved, and cleaning resistance can be enhanced. Furthermore, by improving adhesion, anti-bubbling properties can also be improved (for example, the phenomenon of the absorber film floating off the surface of the protective film and peeling off when hydrogen is introduced into the gas atmosphere during exposure is called "bubbling").

[0126] When hafnium (Hf) is added to ruthenium (Ru) as an additive (e.g., in the case of a RuHf film), the etch resistance of the protective film 6 against a mixture of chlorine-based gases and oxygen, as well as its resistance to cleaning with a sulfuric acid / hydrogen peroxide solution (SPM), is improved. If the Hf concentration in the protective film 6 is too low, the additive effect is not achieved; if it is too high, the extinction coefficient k of the protective film 6 for EUV light becomes high, thus reducing the reflectivity of the reflective mask 200. Therefore, the Hf concentration in the protective film 6 is preferably 5 atomic% or more and 30 atomic% or less, more preferably 10 atomic% or more and 25 atomic% or less.

[0127] like Figure 2As shown, in this preferred embodiment, the protective film 6 of the substrate 110 with a multilayer reflective film preferably includes a first layer 62 and a second layer 64 from the substrate 1 side. It should be noted that when the protective film 6 includes a first layer 62 and a second layer 64, the second layer 64 can be made into a thin film that is the same as the protective film 6 described above.

[0128] When the multilayer reflective film 5 is a Mo / Si periodic laminated film, Mo is easily oxidized by the atmosphere, thus posing a risk of reduced reflectivity of the multilayer reflective film 5. Therefore, the top layer of the multilayer reflective film 5 is made of Si. When the Si film is in contact with the Ru-based protective film 6, silicon (Si) easily diffuses into the protective film 6. That is, over time, Si migrates and diffuses from the Si layer of the multilayer reflective film 5 towards the Ru-based protective film 6 between the grain boundaries of the Ru-based protective film 6 (and then forms ruthenium silicide (RuSi)). Before reaching the surface of the Ru-based protective film 6, it undergoes an oxidation reaction due to the cleaning solution and gas, generating SiO2. Furthermore, if the protective film 6 is not dense, the cleaning solution and gas permeate into the protective film 6, generating SiO2 within the protective film 6 (inside or at the bottom). Furthermore, due to the low adhesion between Ru and SiO2, there is a risk of film peeling during the manufacturing process of the reflective mask 200 or during use after the product is completed, due to repeated cleaning. By giving the protective film 6 a given first layer 62, the diffusion of silicon (Si) from the multilayer reflective film 5 to the protective film 6 can be suppressed.

[0129] To suppress the diffusion of silicon (Si) from the multilayer reflective film 5 to the protective film 6, the first layer 62 preferably contains ruthenium (Ru) and at least one element selected from magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf), and tungsten (W). In particular, when the first layer 62 is a RuTi film, a RuZr film, or a RuAl film, the diffusion of silicon (Si) to the protective film 6 can be suppressed more effectively.

[0130] The proportion of Ru in the Ru compound of layer 62 is preferably greater than 50 atomic% and less than 100 atomic%, more preferably greater than 80 atomic% and less than 100 atomic%, and particularly preferably greater than 95 atomic% and less than 100 atomic%.

[0131] When the protective film 6 comprises a first layer 62 and a second layer 64, the second layer 64 can be made into a thin film identical to the protective film 6 described above. That is, the second layer 64 may contain ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf). Alternatively, the first layer 62 and the second layer 64 may be made into the same material with altered compositional ratios.

[0132] When the first layer 62 is a RuTi film (e.g., a RuTi film, a RuTiN film; the same applies to other RuY films, etc.), the second layer 64 is preferably a RuY film, a RuZr film, or a RuRh film. When the first layer 62 is a RuZr film, the second layer 64 is preferably a RuAl film, a RuY film, a RuZr film, or a RuRh film. In this case, the diffusion of silicon (Si) into the protective film 6 can be more effectively suppressed using the first layer 62, and the resistance of the protective film 6 to etching gases and cleaning can be more effectively improved using the second layer 64.

[0133] Within the scope of achieving the effects of this embodiment, the protective film 6 (first layer 62 and / or second layer 64) may contain at least one selected from N, C, O, H and B. In order to reduce the crystallinity of the film and make it amorphous, the protective film 6 (first layer 62 and / or second layer 64) preferably contains nitrogen (N) and / or oxygen (O).

[0134] The protective film 6 (first layer 62 and / or second layer 64) of the substrate 110 with multilayer reflective films in this embodiment preferably further contains nitrogen (N). By further containing nitrogen (N) in the protective film 6 (first layer 62 and / or second layer 64), crystallinity can be reduced. As a result, the film can be made denser, and therefore, resistance to etching gases and cleaning can be further improved. The proportion of N in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably greater than 1 atomic% and less than 20 atomic% and more preferably more than 3 atomic% and less than 10 atomic%.

[0135] The protective film 6 (first layer 62 and / or second layer 64) of the substrate 110 with multilayer reflective films in this embodiment preferably further contains oxygen (O). By further containing oxygen (O) in the protective film 6 (first layer 62 and / or second layer 64), crystallinity can be reduced. As a result, the film can be made denser, and therefore, resistance to etching gases and cleaning can be further improved. The proportion of O in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably greater than 1 atomic% and less than 20 atomic% and more preferably more than 3 atomic% and less than 10 atomic%.

[0136] In the substrate 110 with multilayer reflective films of this embodiment, the Ru content of the second layer 64 is preferably less than the Ru content of the first layer 62. For example, when the first layer 62 is a RuTi film and the second layer 64 is a RuRh film, even if the Ti content of the RuTi film of the first layer 62 is low, the diffusion of silicon (Si) into the protective film 6 can be suppressed. Therefore, by making the Ru content of the second layer 64 less than the Ru content of the first layer 62, the resistance to etching gases and cleaning can be further improved, and the diffusion of silicon (Si) into the protective film 6 can be suppressed.

[0137] In the substrate 110 with a multilayer reflective film in this embodiment, it is preferable that the refractive index of the second layer 64 is smaller than that of the first layer 62. As a result, a substrate with a protective film (substrate 110 with a multilayer reflective film having a protective film 6) can be fabricated without reducing the reflectivity of EUV light from the multilayer reflective film 5 including the protective film 6. The refractive index of the second layer 64 is preferably 0.920 or less, more preferably 0.885 or less.

[0138] The aforementioned protective film 6 (first layer 62 and / or second layer 64) can be formed by various known methods. Examples of methods for forming the protective film 6 include ion beam sputtering, sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum evaporation. When the first layer 62 is formed by ion beam sputtering, continuous film formation is possible after the formation of the multilayer reflective film 5, which is therefore preferable. Furthermore, when the protective film 6 (first layer 62 and / or second layer 64) contains nitrogen and / or oxygen, reactive sputtering is preferred for stable film formation.

[0139] When the protective film 6 includes a first layer 62 and a second layer 64, a heat treatment can be performed after the formation of the first layer 62 and the second layer 64, or after the formation of the absorber film 7. In this heat treatment, heating can be performed at a temperature higher than the pre-baking temperature (around 110°C) of the resist film 8 in the manufacturing process of the reflective mask blank 100. Specifically, the temperature conditions for the heat treatment are typically 160°C or higher and 300°C or lower, preferably 180°C or higher and 250°C or lower.

[0140] When the above-described heat treatment process is performed, at least a portion of the metal constituting the first layer 62 diffuses into the second layer 64. Furthermore, a substrate 110 with a multilayer reflective film can be obtained in which the content of the metal component constituting the first layer 62 continuously decreases towards the second layer 64 in a composition gradient region between the first layer 62 and the second layer 64.

[0141] Regarding the thickness of the protective film 6 (the sum of the first layer 62 and the second layer 64), there are no particular limitations as long as it fulfills its function as the protective film 6. From the viewpoint of EUV light reflectivity, the thickness of the protective film 6 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm. Furthermore, the thickness of the first layer 62 is preferably 0.5 nm to 2.0 nm, more preferably 1.0 nm to 1.5 nm. Additionally, the thickness of the second layer 64 is preferably 1.0 nm to 7.0 nm, more preferably 1.5 nm to 4.0 nm.

[0142] <Reflective Mask Blank 100>

[0143] The reflective mask blank 100 of this embodiment will be described. The reflective mask blank 100 has an absorber film 7 on the protective film 6 of the substrate 110 with the multilayer reflective film.

[0144] <<Absorbent membrane 7>>

[0145] In this embodiment, the absorber film 7 of the reflective mask blank 100 is formed on the multilayer reflective film 5 (or on the protective film 6 if a protective film 6 is formed). The basic function of the absorber film 7 is to absorb EUV light. The absorber film 7 can be an absorber film 7 specifically for absorbing EUV light, or it can be an absorber film 7 with a phase-shifting function that also takes into account the phase difference of EUV light. An absorber film 7 with a phase-shifting function refers to an absorber film that absorbs EUV light and reflects a portion of it, thereby causing a phase shift. That is, in the patterned reflective mask 200, where the absorber film 7 with a phase-shifting function has been applied, EUV light is absorbed and reduced in the area where the absorber film 7 is formed, while a portion of the light is reflected at a level that does not adversely affect the pattern transfer. In addition, in the area where the absorber film 7 is not formed (field region), EUV light is reflected from the multilayer reflective film 5 via the protective film 6. Therefore, there is a desired phase difference between the reflected light from the absorber film 7 with a phase-shifting function and the reflected light from the field region. The formation of the phase-shifting absorber film 7 results in a phase difference of 170 to 190 degrees between the reflected light from the absorber film 7 and the reflected light from the multilayer reflective film 5. The light with the phase difference flipped by approximately 180 degrees interferes with each other at the edge of the pattern, thereby improving the image contrast of the projected optical image. As the image contrast increases, the resolution rises, allowing for the improvement of various exposure-related tolerances, such as exposure tolerance and focus tolerance.

[0146] The absorber film 7 can be a single-layer film or a multilayer film comprising multiple films (e.g., a lower absorber film and an upper absorber film). In the case of a single-layer film, it has the characteristic of reducing the number of steps in mask blank manufacturing, thereby improving production efficiency. In the case of a multilayer film, its optical constants and film thickness can be appropriately set so that the upper absorber film can be used as an anti-reflective film for mask pattern defect inspection using light. This improves the inspection sensitivity when inspecting mask pattern defects using light. In addition, if films containing oxygen (O) and nitrogen (N) to improve oxidation resistance are used in the upper absorber film, the stability over time is improved. In this way, various functions can be added by making the absorber film 7 into a multilayer film. In the case of an absorber film 7 with phase-shifting function, the range of adjustment using optical surfaces can be increased by making it into a multilayer film, thus obtaining the desired reflectivity.

[0147] The material used for the absorber film 7 is not particularly limited as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably dry etching using chlorine (Cl) and / or fluorine (F) gases), and has a high etch selectivity for the protective film 6 (second layer 64). As a material with such function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or compounds thereof, can be used.

[0148] The absorber film 7 can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, the absorber film 7 of tantalum compounds can be formed by using a target containing tantalum and boron and by using reactive sputtering with argon gas containing oxygen or nitrogen.

[0149] The tantalum compound used to form the absorber film 7 comprises an alloy of Ta and the aforementioned metal. When the absorber film 7 is an alloy of Ta, from the perspective of smoothness and flatness, the crystalline state of the absorber film 7 is preferably an amorphous or microcrystalline structure. When the surface of the absorber film 7 is not smooth / flat, the edge roughness of the absorber pattern 7a sometimes increases, and the dimensional accuracy of the pattern deteriorates. The preferred surface roughness of the absorber film 7, expressed as root mean square roughness (Rms), is 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less.

[0150] As the tantalum compound used to form the absorber membrane 7, the following can be used: compounds containing Ta and B, compounds containing Ta and N, compounds containing Ta, O and N, compounds containing Ta and B and further containing at least one of O and N, compounds containing Ta and Si, compounds containing Ta, Si and N, compounds containing Ta and Ge, and compounds containing Ta, Ge and N, etc.

[0151] Ta is a material with a high absorption coefficient for EUV light and can be easily dry-etched using chlorine-based or fluorine-based gases. Therefore, Ta can be considered a material with excellent processability for the absorber film 7. Furthermore, by adding B, Si, and / or Ge to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 7 can be improved. In addition, if N and / or O are added to Ta, the resistance of the absorber film 7 to oxidation is improved, thus achieving an effect that improves its stability over time.

[0152] <<Back Conductive Film 2>>

[0153] On the second main surface (back side main surface) of the substrate 1 (opposite to the surface on which the multilayer reflective film 5 is formed; if an intermediate layer such as a hydrogen intrusion suppression film is formed on the substrate 1, it is formed on the intermediate layer), a back conductive film 2 for an electrostatic chuck can be formed. The sheet resistance required for the back conductive film 2 for use as an electrostatic chuck is typically 100 Ω / □ (Ω / square) or less. The back conductive film 2 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target containing a metal such as chromium or tantalum, or an alloy thereof. The chromium (Cr) material in the back conductive film 2 is preferably a Cr compound selected from at least one of boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The tantalum (Ta) material in the back conductive film 2 is preferably Ta, an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon. Examples of Ta compounds include: TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON. The thickness of the back conductive film 2 is not particularly limited as long as it meets the requirements for use as an electrostatic chuck, and is typically 10nm to 200nm. Furthermore, the back conductive film 2 also serves to adjust the stress on the second main surface side of the reflective mask blank 100. That is, the back conductive film 2 can be adjusted to balance the stress from the various films formed on the first main surface side, thereby obtaining a flat reflective mask blank 100.

[0154] It should be noted that the back conductive film 2 can be formed on the substrate 110 with multilayer reflective film before forming the absorber film 7 described above. The substrate 110 with multilayer reflective film includes Figure 1 and Figure 2 The substrate 110 with multilayer reflective film shown has a back conductive film 2 disposed on its second main surface. In addition, the reflective mask blank 100 does not necessarily include the back conductive film 2.

[0155] <Etching Mask Film 9>

[0156] An etching mask film 9 can be formed on the absorber film 7. The material used for the etching mask film 9 is one with a high etch selectivity ratio relative to the absorber film 7. Here, "etch selectivity ratio of B to A" refers to the ratio of the etching rate of layer A (the layer that is not to be etched, which becomes the mask layer) to the etching rate of layer B (the layer that is to be etched). Specifically, this can be defined by the mathematical formula "etch selectivity ratio of B to A = etching rate of B / etching rate of A". Furthermore, "high selectivity ratio" means that the value of the selectivity ratio defined above is large relative to the comparison object. The etch selectivity ratio of the absorber film 7 relative to the etching mask film 9 is preferably 1.5 or more, and more preferably 3 or more.

[0157] Materials with high etch selectivity for the absorber film 7 relative to the etch mask film 9 include chromium and chromium compounds. When etching the absorber film 7 using a fluorine-based gas, materials with chromium and chromium compounds can be used. As chromium compounds, materials containing Cr and at least one element selected from N, O, C, and H can be used. Furthermore, when etching the absorber film 7 using a substantially oxygen-free chlorine-based gas, materials with silicon and silicon compounds can be used. As silicon compounds, materials containing Si and at least one element selected from N, O, C, and H can be used, as well as metallic silicon (metal silicides) and metallic silicon compounds (metal silicide compounds). As metallic silicon compounds, materials containing a metal, Si, and at least one element selected from N, O, C, and H can be used.

[0158] In this embodiment, the reflective mask blank 100 preferably includes an etch mask film 9 containing chromium (Cr) on the absorber film 7. The etch mask film 9 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN or CrOCN, and even more preferably is a CrO-based film (CrO film, CrON film, CrOC film or CrOCN film) containing chromium and oxygen.

[0159] By configuring the protective film 6 as described above, damage to the protective film 6 can be suppressed when the chromium (Cr)-containing etching mask film 9 is peeled off by dry etching using a mixture of chlorine and oxygen.

[0160] Furthermore, by making the protective film 6 (or the second layer 64) a RuAl-containing film, a RuY-containing film, or a RuRh-containing film, damage to the protective film 6 can be suppressed when the etching mask film 9 is peeled off using dry etching with fluorine-based gases, provided that the etching mask film 9 is made of silicon or a silicon compound. Therefore, the range of materials or etching conditions for the absorber film 7 and / or the etching mask film 9 is wide. Since damage to the protective film 6 caused by dry etching using fluorine-based gases can be suppressed, the substrate 110 with multilayer reflective films and the reflective mask blank 100 manufactured by the manufacturing method of this embodiment can have a resist film 8 in contact with the absorber film 7 without using the etching mask film 9. A desired pattern, such as a circuit pattern, can be drawn (exposed) on the resist film 8 and further developed and washed to form a given resist pattern. Using this resist pattern as a mask, the absorber film 7 is etched to form an absorber pattern.

[0161] From the viewpoint of achieving a function as an etching mask that forms a transfer pattern on the absorber film 7 with good precision, it is desirable that the thickness of the etching mask film 9 be 3 nm or more. Furthermore, from the viewpoint of reducing the thickness of the resist film 8, it is desirable that the thickness of the etching mask film 9 be 15 nm or less.

[0162] <Other Thin Films>

[0163] Preferably, in this embodiment, the substrate 110 with multilayer reflective film and the reflective mask blank 100 have a hydrogen intrusion suppression film between the glass substrate 1, which serves as their substrate 1, and the back conductive film 2 containing tantalum or chromium, to suppress hydrogen intrusion from the substrate 1 into the back conductive film 2. Due to the presence of the hydrogen intrusion suppression film, hydrogen can be prevented from being introduced into the back conductive film 2, and the increase in compressive stress of the back conductive film 2 can be suppressed.

[0164] The material of the hydrogen intrusion suppression film can be any type, as long as it is not easily permeable by hydrogen and can inhibit hydrogen from penetrating from the substrate 1 into the back conductive film 2. Specific examples of materials for hydrogen intrusion suppression films include: Si, SiO2, SiON, SiCO, SiCON, SiBO, SiBON, Cr, CrN, CrON, CrC, CrCN, CrCO, CrCON, Mo, MoSi, MoSiN, MoSiO, MoSiCO, MoSiON, MoSiCON, TaO, and TaON. The hydrogen intrusion suppression film can be a single layer of these materials, or it can be a multilayer or a composition gradient film.

[0165] <Reflective Mask 200>

[0166] This embodiment is a reflective mask 200 in which the absorber film 7 in the above-mentioned reflective mask blank 100 is patterned to have an absorber pattern 7a on the multilayer reflective film 5. By using the reflective mask blank 100 of this embodiment, a reflective mask 200 having a protective film 6 with high resistance to etching gases and high resistance to cleaning can be obtained.

[0167] The reflective mask 200 is manufactured using the reflective mask blank 100 of this embodiment. Only a brief description is given here; a more detailed description will follow in the embodiments with reference to the accompanying drawings.

[0168] Prepare a reflective mask blank 100, and form a resist film 8 on the outermost surface of its first main surface (as described in the following embodiments, on the etch mask film 9 formed on the absorber film 7) (not required if the resist film 8 is provided as a reflective mask blank 100), draw (expose) a desired pattern such as a circuit pattern on the resist film 8, and then develop and wash it to form a given resist pattern 8a.

[0169] Etching mask pattern 9a is formed by dry etching the etching mask film 9 using the resist pattern 8a as a mask. Next, absorber film 7 is dry etched using the etching mask pattern 9a as a mask to form absorber pattern 7a. It should be noted that the etching gas used for dry etching the absorber film 7 can be selected from chlorine-based gases such as Cl2, SiCl4, and CHCl3; a mixture of chlorine-based gases and O2 in a given ratio; a mixture of chlorine-based gases and He in a given ratio; a mixture of chlorine-based gases and Ar in a given ratio; fluorine-based gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2; and a mixture of fluorine-based gases and O2 in a given ratio. Here, if oxygen is present in the etching gas at the final stage of etching, the Ru-based protective film 6 will develop a rough surface. Therefore, during the over-etching stage where the Ru-based protective film 6 is exposed to etching, an oxygen-free etching gas is preferably used. After the absorber pattern 7a is formed, the etch mask pattern 9a can be removed using a mixture of chlorine-based and oxygen-based gases or a fluorine-based gas.

[0170] Then, the resist pattern 8a is removed using an ashing and resist stripping solution to create an absorber pattern 7a with the desired circuit pattern.

[0171] Through the above procedures, the reflective mask 200 of this embodiment can be obtained.

[0172] <Methods for Manufacturing Semiconductor Devices>

[0173] This embodiment relates to a method for manufacturing a semiconductor device, comprising: performing a photolithography process using an exposure apparatus on a reflective mask 200 to form a transfer pattern on a substrate. Specifically, the reflective mask 200 can be placed in an exposure apparatus having an exposure light source that emits EUV light to transfer the transfer pattern onto a resist film formed on a substrate. According to the semiconductor device manufacturing method of this embodiment, since a reflective mask 200 can be used where the presence of impurities (trace amounts of material) in the thin film of the reflective mask 200 does not adversely affect the performance of the reflective mask 200, a semiconductor device having a fine and highly precise transfer pattern can be manufactured.

[0174] Specifically, by using the reflective mask 200 of this embodiment for EUV exposure, a desired transfer pattern can be formed on a semiconductor substrate. Through various processes other than this photolithography, such as etching of the processed film, formation of insulating and conductive films, introduction of dopants, or annealing, a semiconductor device with a desired electronic circuit can be manufactured with a high yield.

[0175] Example

[0176] The following describes the embodiments. These embodiments do not limit the present invention.

[0177] (Example)

[0178] As an example, a substrate 110 with a multilayer reflective film, on which a multilayer reflective film 5 and a protective film 6 are formed on the first main surface of a substrate 1, was fabricated. Table 1 shows the material and composition of the protective film 6 formed as an example. The substrates 110 with multilayer reflective films in each embodiment are fabricated in the same way except for the type of protective film 6. The protective film described below was used as the protective film 6 in each embodiment.

[0179] The protective film 6 in Examples 1-1 and 1-2 is a RuAl film, and the protective film 6 in Examples 1-3 is a RuAlN film (refer to...). Figure 1 The protective film 6 in Examples 1-4 is a protective film 6 composed of two layers: the first layer 62 of the RuZr film and the second layer 64 of the RuAl film (see reference). Figure 2 ).

[0180] The protective film 6 in Examples 2-1 and 2-2 is a RuY film, and the protective film 6 in Example 2-3 is a RuYN film (refer to...). Figure 1 The protective film 6 in Examples 2-4 is a protective film 6 composed of two layers: the first layer 62 of the RuTi film and the second layer 64 of the RuY film (see reference). Figure 2 ).

[0181] The protective film 6 in Examples 3-1 and 3-2 is a RuZr film, and the protective film 6 in Example 3-3 is a RuZrN film (refer to...). Figure 1 The protective film 6 in Examples 3-4 is a protective film 6 composed of two layers: the first layer 62 of the RuZr film and the second layer 64 of the RuZr film (see reference). Figure 2 ).

[0182] The protective film 6 in Examples 4-1 and 4-2 is a RuRh film, and the protective film 6 in Example 4-3 is a RuRhN film (refer to...). Figure 1 The protective film 6 in Examples 4-4 is a protective film 6 composed of two layers: the first layer 62 of the RuTi film and the second layer 64 of the RuRh film (see reference). Figure 2 ).

[0183] The protective film 6 in Examples 5-1 and 5-2 is a RuHf film, and the protective film 6 in Example 5-3 is a RuHfN film (refer to...). Figure 1 The protective film 6 in Examples 5-4 is a protective film 6 composed of two layers: the first layer 62 of the RuZr film and the second layer 64 of the RuHf film (see reference). Figure 2 ).

[0184] The substrate 110 with multilayer reflective film in the embodiment is fabricated as described below.

[0185] A SiO2-TiO2 type glass substrate with dimensions of 6025 (approximately 152mm × 152mm × 6.35mm) and serving as a low thermal expansion glass substrate is prepared as substrate 1, with both the first and second main surfaces having been ground. A grinding process consisting of coarse grinding, precision grinding, localized processing, and touch grinding is performed to obtain a flat and smooth main surface.

[0186] Next, a multilayer reflective film 5 was formed on the first main surface of the substrate 1. To make the multilayer reflective film 5 suitable for EUV light with a wavelength of 13.5 nm, it was fabricated as a periodic multilayer reflective film 5 containing Si and Mo. Specifically, Si targets and Mo targets were used as targets for high and low refractive index materials, respectively. Krypton (Kr) ions were supplied to these targets from an ion source for ion beam sputtering, thereby alternately stacking Si and Mo layers on the substrate 1.

[0187] Here, the sputtered particles of Si and Mo are incident at an angle of 30 degrees relative to the normal of the first main surface of the substrate 1. First, a Si layer with a thickness of 4.2 nm is formed, followed by a Mo layer with a thickness of 2.8 nm. This is considered as one cycle, and 40 cycles are stacked in the same manner. Finally, a Si layer with a thickness of 4.0 nm is formed, thus creating the multilayer reflective film 5. Therefore, the material of the bottommost layer of the multilayer reflective film 5, which is closest to the substrate 1, is Si, and the material of the topmost layer of the multilayer reflective film 5, which is in contact with the protective film 6, is also Si.

[0188] Next, a protective film 6 as shown in Table 1 was formed on the surface of the multilayer reflective film 5 by ion beam sputtering. For example, in the case of the protective film 6 in Example 1-1, a RuAl mixed sintered target with the composition shown in Table 1 was used as the target for the ion beam sputtering. In an Ar atmosphere, the protective film 6 of Example 1-1, composed of a RuAl film with the composition shown in Table 1, was formed by ion beam sputtering using the RuAl mixed sintered target to a thickness shown in Table 1. Here, the sputtered Ru and Al particles were incident at an angle of 30 degrees relative to the normal of the first main surface of the substrate 1. For the protective films 6 of other embodiments, the protective films 6 were also formed in the same manner as in Example 1-1.

[0189] It should be noted that the protective films 6 in Examples 1-3, 2-3, 3-3, 4-3, and 5-3 contain nitrogen (N). These protective films 6 are formed by reactive sputtering using a mixed gas atmosphere of Ar and N2.

[0190] Furthermore, the protective film 6 in Examples 1-4, 2-4, 3-4, 4-4, and 5-4 is a protective film 6 composed of two layers: a first layer 62 and a second layer 64. Therefore, in these examples, the second layer 64 is formed after the first layer 62 is formed. Table 2 shows the composition and film thickness of the first layer 62 in these examples. Additionally, Table 1 shows the composition and film thickness of the second layer 64 in these examples.

[0191] The substrate 110 with a multilayer reflective film of the embodiment was manufactured as described above.

[0192] (Comparative Example 1)

[0193] Except for the single-layer protective film 6, which is made of only Ru, the substrate 110 with a multilayer reflective film of Comparative Example 1 was manufactured in the same manner as in Examples 1-1. For the protective film 6 of Comparative Example 1, the protective film 6 of Comparative Example 1, which is made of Ru film, was formed in an Ar atmosphere by using ion beam sputtering with a Ru target to the film thickness shown in Table 1.

[0194] (Reflective mask blank 100)

[0195] Using the substrate 110 with multilayer reflective film described in the above embodiments and Comparative Example 1, a reflective mask blank 100 comprising an absorber film 7 and an etching mask film 9 was manufactured. Hereinafter, the manufacturing method of the reflective mask blank 100 will be described.

[0196] An absorber film 7 was formed on the protective film 6 of a substrate 110 with a multilayer reflective film using DC magnetron sputtering. The absorber film 7 is a laminated film consisting of a TaN film as an absorber layer and a TaO film as a low-reflection layer. The TaN film, serving as the absorber layer, was formed on the surface of the protective film 6 of the substrate 110 with the multilayer reflective film using DC magnetron sputtering. The substrate 110 with the multilayer reflective film was placed opposite a Ta target, and the TaN film was formed by reactive sputtering in a mixed atmosphere of Ar and N2 gases. Next, a TaO film (low-reflection layer) was further formed on the TaN film using DC magnetron sputtering. This TaO film, like the TaN film, was formed by reactive sputtering in a mixed atmosphere of Ar and O2 gases, with the substrate 110 with the multilayer reflective film placed opposite a Ta target.

[0197] The TaN film has an atomic ratio of Ta:N = 70:30 and a thickness of 48 nm. The TaO film has an atomic ratio of Ta:O = 35:65 and a thickness of 11 nm.

[0198] Next, an etching mask film 9 composed of a CrOCN film was formed on the absorber film 7 by DC magnetron sputtering. The CrOCN film was formed by reactive sputtering using a Cr target and a mixed gas atmosphere of Ar, N2, and CO2. The etching mask film 9 was formed with a film thickness of 5 nm.

[0199] Next, a CrN-containing back conductive film 2 was formed on the second main surface (back side main surface) of substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. The formation conditions of the back conductive film 2 were: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90 atomic%, N: 10 atomic%), and film thickness of 20 nm.

[0200] The reflective mask blank 100 of the embodiment and comparative example 1 was manufactured as described above.

[0201] (Reflective mask 200)

[0202] Next, a reflective mask 200 was manufactured using the reflective mask blank 100 from Examples and Comparative Example 1. (Refer to...) Figure 8 The manufacturing process of the reflective mask 200 will be explained.

[0203] Figure 8 (a) is (for example, refer to) Figure 4 This specification provides a schematic cross-sectional view of an exemplary reflective mask blank 100. Firstly, as... Figure 8 As shown in (b), a resist film 8 is formed on the etch mask film 9 of the reflective mask blank 100. Then, a desired pattern, such as a circuit pattern, is drawn (exposed) on the resist film 8, followed by further development and rinsing, thereby forming a given resist pattern 8a. Figure 8 (c)). Next, using the resist pattern 8a as a mask, a dry etching process is performed on the etching mask film 9 using a mixture of Cl2 and O2 gases (Cl2 + O2 gas), thereby forming the etching mask pattern 9a. Figure 8 (d)). The resist pattern 8a was stripped by oxygen ashing. Using the etching mask pattern 9a as a mask, the TaO film (low-reflection layer) of the absorber film 7 was dry-etched using CF4 gas, followed by dry etching of the TaN film using Cl2 gas, thereby forming the absorber pattern 7a. Figure 8 (e)).

[0204] Then, the etch mask pattern 9a was removed by dry etching using a mixture of Cl2 and O2 gases (Cl2 + O2 gas). Figure 8 (f) Finally, a wet cleaning process using pure water (DIW) was performed to manufacture the reflective mask 200 of Example 1 and Comparative Example 1.

[0205] The reflective mask 200 of Embodiment 1 and Comparative Example 1 was manufactured as described above.

[0206] (Evaluation of the reflective mask 200 of the Example and Comparative Example 1)

[0207] The effects of dry etching when removing the etched mask pattern 9a were evaluated in the examples of the above embodiments and Comparative Example 1.

[0208] Specifically, for each example of the above embodiments and Comparative Example 1, the manufacturing... Figure 4 The mask blank with the structure shown is formed into a shape similar to the one described above through the manufacturing process of the reflective mask 200. Figure 8(e) An etch mask pattern 9a and an absorber pattern 7a of the same type. The absorber pattern 7a used for evaluation was shaped to allow for the measurement of EUV light reflectance on the exposed portion of the protective film 6, resulting in a pattern that significantly exposes the surface of the protective film 6. After forming the absorber pattern 7a, the reflectance of the protective film 6 surface to EUV light at a wavelength of 13.5 nm (reflectance before etching) was measured. Next, the etch mask pattern 9a of the CrOCN film was removed using dry etching with a mixture of Cl2 and O2 gases (Cl2:O2 = 9:1). Figure 8 (f)). After removing the etched mask pattern 9a by etching, the reflectance of the surface of the protective film 6 to EUV light with a wavelength of 13.5 nm was measured (reflectance after etching). Column A of Table 3 shows the change in reflectance before and after the etched mask pattern 9a was removed by etching (reflectance after etching / reflectance before etching). The change in reflectance is expressed as a ratio when Comparative Example 1 is set to 1.

[0209] Furthermore, the change in film thickness of the protective film 6 during dry etching using the aforementioned mixed gas of Cl2 and O2 (Cl2 + O2 gas) was measured, and the etching rates of each material were calculated as a ratio when the etching rate of the Ru film of the protective film 6 using the mixed gas was set to 1. Column B of Table 3 shows the etching rate ratios of the protective film 6 using the mixed gas.

[0210] As can be clearly seen from Table 3, compared to Comparative Example 1, the change in reflectivity of the etched mask pattern 9a before and after etching is small in all embodiments. Furthermore, compared to Comparative Example 1, the etching rate of the protective film 6 using the mixed gas (Cl2 + O2 gas) is low in all embodiments. Therefore, it is clear that the protective film 6 of this embodiment has high resistance to the etching gas used to remove the etched mask film 9.

[0211] In addition, the resistance of the protective film 6 to cleaning with a sulfuric acid / hydrogen peroxide mixed solution (SPM) was separately measured. The results clearly show that, compared with Comparative Example 1, the film thickness change before and after cleaning was small in all examples, and the change in reflectivity to EUV light was small. Therefore, the protective film 6 has high resistance to cleaning.

[0212] Table 4 shows the rate of decrease in membrane thickness when SPM cleaning was performed under the following cleaning conditions, with Comparative Example 1 (Ru membrane) set to 1.

[0213] The cleaning solution consists of H₂SO₄ and H₂O₂ in a weight ratio of 2:1.

[0214] Cleaning temperature 120℃

[0215] Cleaning time: 10 minutes

[0216] As can be clearly seen from Table 4, the SPM cleaning resistance of Examples 4-2 (Ru:Rh = 70:30) and 4-3 (Ru:Rh:N = 65:30:5) is higher than that of Example 4-1 (Ru:Rh = 80:20). It should be noted that the protective film of Example 4-4 is the same as that of Example 4-2; therefore, when Comparative Example 1 (Ru film) is set to 1, the rate of decrease in its film thickness is also the same as that of Example 4-2.

[0217] (Semiconductor device manufacturing)

[0218] A reflective mask 200, manufactured from a substrate 110 with a multilayer reflective film as described in this embodiment, is placed in an EUV scanner to perform EUV exposure on a wafer on which a workable film and a resist film are formed. Then, the exposed resist film is developed, thereby forming a resist pattern on the semiconductor substrate on which the workable film is formed.

[0219] The reflective mask 200 manufactured using the substrate 110 with multilayer reflective film of the embodiment has a protective film with high resistance to etching gases and high resistance to cleaning, thus enabling the formation of fine and high-precision transfer patterns (resist patterns).

[0220] The resist pattern is transferred to the processed film by etching. In addition, through various processes such as the formation of insulating film and conductive film, introduction of dopants, or annealing, a high yield of semiconductor device with desired characteristics is achieved.

[0221]

[0222]

[0223]

[0224]

Claims

1. A substrate with a multilayer reflective film, comprising: a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, the protective film comprising a first layer and a second layer from the substrate side, the first layer containing ruthenium (Ru) and containing at least one selected from the group consisting of magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf), and tungsten (W), the second layer containing ruthenium (Ru) and containing at least one selected from the group consisting of aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf), and the Ru content of the second layer being less than the Ru content of the first layer.

2. A substrate with a multilayer reflective film, comprising: a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, the protective film comprising a first layer and a second layer from the substrate side, the first layer containing ruthenium (Ru) and containing at least one selected from the group consisting of magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf), and tungsten (W), the second layer containing ruthenium (Ru) and containing at least one selected from the group consisting of aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf), and the refractive index of the second layer being less than the refractive index of the first layer.

3. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the first layer further contains nitrogen (N) at a content of 1 atomic% or more and 20 atomic% or less.

4. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the second layer further contains nitrogen (N) at a content of 1 atomic% or more and 20 atomic% or less. wherein 5. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the proportion of Ru in the first layer is more than 50 atomic% and less than 100 atomic%.

6. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the refractive index of the second layer is 0.920 or less.

7. The substrate with a multilayer reflective film according to claim 1 or 2, wherein the film thickness of the first layer is 0.5 nm to 2.0 nm and the film thickness of the second layer is 1.0 nm to 7.0 nm.

8. A reflective mask blank, comprising an absorber film on the protective film of the substrate with a multilayer reflective film according to any one of claims 1 to 7.

9. A reflective mask, comprising an absorber pattern obtained by patterning the absorber film in the reflective mask blank according to claim 8.

10. A method for manufacturing a semiconductor device, comprising the step of: providing the reflective mask according to claim 9 to an exposure device having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a transfer substrate. ​ ​ wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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