Substrate with multilayer reflection film, reflection type mask blank, reflection type mask and method for manufacturing the same, and method for manufacturing semiconductor device

Abstract

To provide a substrate with a multilayer reflection film for manufacturing a reflection type mask having high resistance to etching gas and a protection film having high resistance to cleaning.SOLUTION: A substrate with a multilayer reflection film has a substrate, a multilayer reflection film provided on the substrate, and a protection film provided on the multilayer reflection film, where the protection film contains ruthenium (Ru) and at least one additive material selected from the group consisting of aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf), and the content of the additive material is 5 atom% or more and less than 50 atom%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask used in the manufacture of a semiconductor device, a multilayer reflective film-coated substrate used for the manufacture of a reflective mask, and a reflective mask blank. The present invention also relates to a method for manufacturing a semiconductor device using the reflective mask. [Background technology]

[0002] In recent years, with the increasing demand for higher density and precision in VLSI devices, EUV lithography, an exposure technology using extreme ultraviolet (EUV) light, is seen as promising. EUV light refers to light in the wavelength range of soft X-rays or vacuum ultraviolet light, specifically light with a wavelength of about 0.2 to 100 nm.

[0003] A reflective mask has a multilayer reflective film formed on a substrate for reflecting exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film for absorbing the exposure light. Light incident on a reflective mask mounted on an exposure machine for transferring a pattern onto a semiconductor substrate is absorbed in the area with the absorber pattern, and is reflected by the multilayer reflective film in the area without the absorber pattern. The optical image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflection optical system.

[0004] In order to achieve higher density and precision in semiconductor devices using a reflective mask, it is necessary for the reflective area of ​​the reflective mask (the surface of the multilayer reflective film) to have high reflectivity for the EUV light, which is the exposure light.

[0005] As the multilayer reflective film, a multilayer film in which elements having different refractive indices are periodically laminated is generally used. For example, as a multilayer reflective film for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminate film in which Mo films and Si films are alternately laminated for about 40 periods is preferably used.

[0006] A reflective mask used in EUV lithography is, for example, that described in Patent Document 1. Patent Document 1 describes a reflective photomask having a substrate, a reflective layer formed on the substrate and made of a multilayer film in which two different types of films are alternately stacked, a buffer layer made of a ruthenium film formed on the reflective layer, and an absorber pattern formed on the buffer layer in a predetermined pattern shape and made of a material capable of absorbing soft X-rays. The buffer layer described in Patent Document 1 is also generally called a protective film.

[0007] Patent Document 2 describes a multilayer reflective film-coated substrate that includes a multilayer reflective film that reflects exposure light on the substrate. Patent Document 2 also describes that a protective film for protecting the multilayer reflective film is formed on the multilayer reflective film, and that the protective film is a protective film formed by laminating a reflectance reduction suppression layer, a blocking layer, and an etching stopper layer in this order. Patent Document 2 also describes that the etching stopper layer is made of ruthenium (Ru) or an alloy thereof, and that specific examples of ruthenium alloys include ruthenium niobium (RuNb) alloys, ruthenium zirconium (RuZr) alloys, ruthenium rhodium (RuRh) alloys, ruthenium cobalt (RuCo) alloys, and ruthenium rhenium (RuRe) alloys.

[0008] Patent Documents 3 and 4 disclose a multilayer reflective film-coated substrate having 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 disclose that the surface layer of the multilayer reflective film on the side opposite to the substrate is a layer containing Si.

[0009] Patent Document 3 describes that a block layer that prevents Si from migrating to the Ru-based protective film is provided between the multilayer reflective film and the Ru-based protective film. Patent Document 3 describes that the constituent material of the Ru-based protective film 18 can be Ru or an alloy material thereof, and that the Ru alloy is preferably a Ru compound having Ru and at least one metal element selected from the group consisting of Nb, Zr, Rh, Ti, Co, and Re.

[0010] Furthermore, Patent Document 4 describes that the Ru-based protective film contains an Ru compound containing Ru and Ti, and that the Ru compound contains more Ru than RuTi in the stoichiometric composition. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2002-122981 A [Patent Document 2] JP 2014-170931 A [Patent Document 3] International Publication No. 2015 / 012151 [Patent Document 4] International Publication No. 2015 / 037564 Summary of the Invention [Problem to be solved by the invention]

[0012] In the manufacturing process of a reflective mask, when an absorber pattern is formed, the absorber film is etched through a resist film and / or an etching mask film. In order to obtain a design shape for the absorber pattern, it is necessary to perform a slight overetching when etching the absorber film. Therefore, the film below the absorber film (film on the substrate side) is also etched. In order to prevent the multilayer reflective film below the absorber film from being damaged during the overetching of the absorber film, a protective film is provided. Therefore, the protective film is required to have high resistance to the etching gas of the absorber film.

[0013] For example, Ru or RuNb is used as a material of the protective film having high resistance to the etching gas of the absorber film. When the etching mask film formed on the absorber film is made of a Cr-based material, a mixed gas of chlorine gas and oxygen gas is used as an etching gas to peel off the etching mask film. The protective films of Ru and RuNb have low resistance to mixed gases containing oxygen gas. Therefore, when the etching mask film is peeled off, the multilayer reflective film formed under the protective film may be damaged. In addition, the protective film damaged when peeling off the etching mask film may not have sufficient resistance in the subsequent correction process of the absorber pattern.

[0014] In EUV lithography for manufacturing semiconductor devices, there are few substances that are transparent to the exposure light. Therefore, it is not technically easy to make an EUV pellicle for preventing adhesion of foreign matter to the mask pattern surface of a reflective mask. In addition, in EUV lithography, exposure contamination occurs, such as deposition of a carbon film on the mask or growth of an oxide film due to EUV exposure. Therefore, when the mask is used in the manufacture of semiconductor devices, it is necessary to frequently clean the mask with a cleaning solution such as sulfuric acid / hydrogen peroxide (SPM) to remove foreign matter and contamination on the mask. However, there is a problem that the protective films of Ru and RuNb are not sufficiently resistant to SPM cleaning.

[0015] Thin films made of Ru and RuNb are easily crystallized and have high crystallinity. Thin films with high crystallinity are inferior in terms of density compared to amorphous thin films. Therefore, protective films made of Ru and RuNb have low resistance to certain etching gases and are thought to have problems in that they are not sufficiently resistant to cleaning such as SPM cleaning.

[0016] Therefore, an object of the present invention is to provide a reflective mask having a protective film that is highly resistant to etching gases and highly resistant to cleaning. Another object of the present invention is to provide a multilayer reflective film-coated substrate and a reflective mask blank for producing a reflective mask having a protective film that is highly resistant to etching gases and highly resistant to cleaning. [Means for solving the problem]

[0017] In order to solve the above problems, the present invention has the following configuration.

[0018] (Configuration 1) A first aspect of the present invention is a multilayer reflective film-coated substrate having a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, The protective film is a multilayer reflective film-coated substrate, characterized in that it 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 atomic %.

[0019] (Configuration 2) In a second aspect of the present invention, the protective film includes a first layer and a second layer from the substrate side, the first layer includes ruthenium (Ru) and at least one 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); The multilayer reflective film-coated substrate according to configuration 1, wherein the second layer contains the ruthenium (Ru) and the additive material.

[0020] (Configuration 3) A multilayer reflective film-coated substrate according to configuration 3 of the present invention is the multilayer reflective film-coated substrate according to configuration 1 or 2, characterized in that the protective film, the first layer, or the second layer further contains nitrogen (N).

[0021] (Configuration 4) A fourth aspect of the present invention is the multilayer reflective film-coated substrate according to any one of the first to third aspects, wherein the Ru content in the second layer is less than the Ru content in the first layer.

[0022] (Configuration 5) A fifth aspect of the present invention is a reflective mask blank comprising an absorber film on the protective film of the multilayer reflective film-coated substrate according to any one of the first to fourth aspects.

[0023] (Configuration 6) A sixth aspect of the present invention is the reflective mask blank according to the fifth aspect, further comprising an etching mask film containing chromium (Cr) on the absorber film.

[0024] (Configuration 7) A seventh aspect of the present invention is a reflective mask characterized in that the absorber film in the reflective mask blank of the fifth or sixth aspect includes an absorber pattern formed by patterning the absorber film.

[0025] (Configuration 8) In an eighth aspect of the present invention, the etching mask film of the reflective mask blank according to the sixth aspect is patterned to form an etching mask pattern; The absorber film is patterned using the etching mask pattern as a mask to form an absorber pattern; The method for producing a reflective mask is characterized in that the etching mask pattern is removed by using a mixed gas of a chlorine-based gas and an oxygen gas.

[0026] (Configuration 9) Configuration 9 of the present invention is a method for manufacturing a semiconductor device, comprising the steps of setting the reflective mask of configuration 7 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a transfer substrate. Effect of the Invention

[0027] According to the present invention, it is possible to provide a reflective mask having a protective film that is highly resistant to etching gases and highly resistant to cleaning. Also, according to the present invention, it is possible to provide a multilayer reflective film-coated substrate and a reflective mask blank for manufacturing a reflective mask having a protective film that is highly resistant to etching gases and highly resistant to cleaning. [Brief description of the drawings]

[0028] [Figure 1] 1 is a schematic cross-sectional view of an example of a multilayer reflective film-coated substrate of the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of another example of a multilayer reflective film-coated substrate of the present embodiment. [Diagram 3] FIG. 2 is a schematic cross-sectional view of an example of a reflective mask blank of the present embodiment. [Figure 4] FIG. 2 is a schematic cross-sectional view of another example of the reflective mask blank of the present embodiment. [Diagram 5] FIG. 13 is a graph showing the relationship between the Rh content and the etching rate of a protective film by a mixed gas. [Figure 6] FIG. 1 is a diagram showing the measurement results of diffracted X-ray intensity (CPS) versus diffraction angle 2θ. [Figure 7] FIG. 1 is a diagram showing the measurement results of diffracted X-ray intensity (CPS) versus diffraction angle 2θ for a film into which nitrogen (N) was introduced during film formation. [Figure 8] 1A to 1C are schematic cross-sectional views illustrating an example of a method for manufacturing a reflective mask according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are merely for the purpose of specifically explaining the present invention, and are not intended to limit the scope of the present invention.

[0030] Fig. 1 is a cross-sectional view illustrating an example of a multilayer reflective film-coated substrate 110 of this embodiment. The multilayer reflective film-coated substrate 110 illustrated in Fig. 1 includes a multilayer reflective film 5 and a protective film 6. The multilayer reflective film-coated substrate 110 may further include other thin films such as a back surface conductive film 2.

[0031] Fig. 2 is a schematic cross-sectional view of a multilayer reflective film coated substrate 110 similar to that of Fig. 1. However, in the multilayer reflective film coated substrate 110 shown in Fig. 2, the protective film 6 includes a first layer 62 and a second layer 64.

[0032] Fig. 3 is a schematic cross-sectional view showing an example of a reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Fig. 3 comprises a back surface conductive film 2, a multilayer reflective film 5, a protective film 6 and an absorber film 7. The reflective mask blank 100 may further comprise other thin films such as a resist film 8.

[0033] Fig. 4 is a schematic cross-sectional view showing an example of a reflective mask blank 100 further comprising an etching mask film 9 in addition to the configuration shown in Fig. 3. The reflective mask blank 100 may further comprise other thin films such as a resist film 8.

[0034] In this specification, among the main surfaces of the mask blank substrate 1, the main surface on which the multilayer reflective film 5 is formed may be referred to as the "front main surface" (or the "first main surface"). Also, the main surface on which the multilayer reflective film 5 is not formed may be referred to as the "rear main surface" (or the "second main surface"). A rear conductive film 2 is formed on the "rear main surface" (or the "second main surface").

[0035] In this specification, "having a predetermined thin film on the main surface of the mask blank substrate 1" not only means that the predetermined thin film is disposed in contact with the main surface of the mask blank substrate 1, but also includes the case where another film is present between the mask blank substrate 1 and the predetermined thin film. For example, "having film B on film A" not only means that film A and film B are disposed so as to be in direct contact with each other, but also includes the case where another film is present between film A and film B. In this specification, for example, "film A is disposed in contact with the surface of film B" means that film A and film B are disposed so as to be in direct contact with each other, without another film being interposed between film A and film B.

[0036] Next, the surface roughness (Rms) which is a parameter indicating the surface morphology of the mask blank substrate 1 and the surface morphology of the thin film constituting the reflective mask blank 100 or the like will be described.

[0037] Rms (Root Mean Square), a typical index of surface roughness, is the square root of the average of the squares of the deviations from the average line to the measurement curve. Rms is expressed by the following formula (1).

[0038]

number

[0039] Rms has conventionally been used to control the surface roughness of the mask blank substrate 1, and allows the surface roughness to be grasped numerically.

[0040] <Substrate 110 with multilayer reflective film> The substrate 1 and each thin film constituting the multilayer reflective film coated substrate 110, which is one type of the thin film coated substrate 1 of this embodiment, will be described below.

[0041] <<Substrate 1>> The substrate 1 in the multilayer reflective film coated substrate 110 of this embodiment is required to prevent the absorber pattern 7a from being distorted due to heat during EUV exposure. For this reason, a substrate having a low thermal expansion coefficient within the range of 0±5 ppb / °C is preferably used as the substrate 1. Examples of materials having a low thermal expansion coefficient within this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0042] The first main surface (front main surface) of the substrate 1 on which the transfer pattern (constituting the absorber film 7 described later) is formed is surface-processed to have a predetermined flatness from the viewpoint of obtaining at least pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less in a 132 mm×132 mm area of ​​the first main surface on which the transfer pattern of the substrate 1 is formed. In addition, the second main surface (back main surface) on the opposite side to the side on which the absorber film 7 is formed is a surface that is electrostatically chucked when set in an exposure device. The second main surface is preferably 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less in a 132 mm×132 mm area. The flatness of the second main surface of the reflective mask blank 100 in an area of ​​142 mm×142 mm is preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 0.3 μm or less.

[0043] In addition, the surface smoothness of the substrate 1 is also an extremely important item. The surface roughness of the first main surface on which the absorber pattern 7a for transfer is formed is preferably 0.15 nm or less in root mean square roughness (Rms), more preferably 0.10 nm or less in Rms. The surface smoothness can be measured by an atomic force microscope.

[0044] Furthermore, the substrate 1 preferably has high rigidity in order to prevent deformation due to film stress of films (such as the multilayer reflective film 5) formed on the substrate 1. In particular, the substrate 1 preferably has a high Young's modulus of 65 GPa or more.

[0045] <<Base film>> The multilayer reflective film coated substrate 110 of this embodiment can have an undercoat film in contact with the surface of the substrate 1. The undercoat film is a thin film formed between the substrate 1 and the multilayer reflective film 5. The presence of the undercoat film prevents charge-up during mask pattern defect inspection using an electron beam, reduces phase defects in the multilayer reflective film 5, and provides high surface smoothness.

[0046] The material of the undercoat film is preferably a material containing ruthenium or tantalum as a main component. For example, it may be Ru metal alone or Ta metal alone, or it may be a Ru alloy or Ta alloy containing metals such as titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and / or rhenium (Re) in Ru or Ta. The thickness of the undercoat film is preferably in the range of, for example, 1 nm to 10 nm.

[0047] <<Multilayer reflective film 5>>

[0048] The multilayer reflective film-coated substrate 110 of the embodiment includes a multilayer reflective film 5. The multilayer reflective film 5 provides the reflective mask 200 with a function of reflecting EUV light. The multilayer reflective film 5 is a multilayer film in which layers containing elements with different refractive indices as main components are periodically laminated.

[0049] Generally, the multilayer reflective film 5 is a multilayer film in which thin films (high refractive index layers) of a light element or its compound, which is a high refractive index material, and thin films (low refractive index layers) of a heavy element or its compound, which is a low refractive index material, are alternately stacked in about 40 to 60 periods.

[0050] The multilayer film used as the multilayer reflective film 5 may be laminated in multiple cycles, with a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side, or may be laminated in multiple cycles, with a low refractive index layer / high refractive index layer stacked in this order from the substrate 1 side. Note that the top layer of the multilayer reflective film 5, i.e., the surface layer of the multilayer reflective film 5 opposite the substrate 1 side, is preferably a high refractive index layer. In the above-mentioned multilayer film, when a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side is stacked in multiple cycles, with a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side, the top layer is a low refractive index layer. In this case, if the low refractive index layer constitutes the top surface of the multilayer reflective film 5, it is easily oxidized, and the reflectance of the reflective mask 200 decreases. Therefore, it is preferable to form a high refractive index layer on the top low refractive index layer to form the multilayer reflective film 5. On the other hand, in the above-mentioned multilayer film, when a low refractive index layer / high refractive index layer laminate structure in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side is one period, the uppermost layer is the high refractive index layer. Therefore, in this case, there is no need to form an additional high refractive index layer.

[0051] The high refractive index layer may be a layer containing silicon (Si). As the material containing Si, in addition to a simple substance of Si, a Si compound containing boron (B), carbon (C), nitrogen (N), oxygen (O) and / or hydrogen (H) in addition to Si may be used. By using a high refractive index layer containing Si, a reflective mask 200 having excellent reflectance to EUV light can be obtained. In addition, the low refractive index layer may be a simple substance of metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh) and platinum (Pt), or an alloy thereof. In addition, boron (B), carbon (C), nitrogen (N), oxygen (O) and / or hydrogen (H) may be added to these simple substances or alloys. In the multilayer reflective film-coated substrate 110 of this embodiment, it is preferable that the low refractive index layer is a molybdenum (Mo) layer and the high refractive index layer is a silicon (Si) layer. For example, a Mo / Si periodic laminated film in which Mo layers and Si layers are alternately laminated for about 40 to 60 periods is preferably used as the multilayer reflective film 5 for reflecting EUV light with a wavelength of 13 nm to 14 nm. The high refractive index layer that is the top layer of the multilayer reflective film 5 may be formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the top layer (Si) and the protective film 6. With this structure, it is possible to improve the mask cleaning resistance.

[0052] The reflectance of the multilayer reflective film 5 alone is usually 65% ​​or more, and the upper limit is usually 73%. The thickness and period of each of the constituent layers of the multilayer reflective film 5 can be appropriately selected depending on the exposure wavelength. Specifically, the thickness and period of each of the constituent layers of the multilayer reflective film 5 can be selected so as to satisfy the law of Bragg reflection. In the multilayer reflective film 5, there are multiple high refractive index layers and multiple low refractive index layers, but the thicknesses of the high refractive index layers and the low refractive index layers do not necessarily have to be the same. In addition, the thickness of the Si layer on the outermost surface of the multilayer reflective film 5 can be adjusted within a range that does not reduce the reflectance. The thickness of the Si (high refractive index layer) on the outermost surface can be 3 nm to 10 nm.

[0053] The method of forming the multilayer reflective film 5 is known in the art, and for example, each layer can be formed by ion beam sputtering. In the case of the Mo / Si periodic laminated film described above, for example, a Si film having a thickness of about 4 nm is first formed on the substrate 1 using a Si target by ion beam sputtering, and then a Mo film having a thickness of about 3 nm is formed using a Mo target, and this constitutes one period, and 40 to 60 periods are laminated to form the multilayer reflective film 5 (the outermost layer is a Si film). Note that, although the number of steps increases in the case of 60 periods compared to 40 periods, the reflectance to EUV light can be increased.

[0054] <<Protective film 6>> 1 and 2, the multilayer reflective film-coated substrate 110 of this embodiment has a protective film 6 on the multilayer reflective film 5. By having the protective film 6 on the multilayer reflective film 5, it is possible to suppress damage to the surface of the multilayer reflective film 5 when the multilayer reflective film-coated substrate 110 is used to manufacture a reflective mask 200. Therefore, the resulting reflective mask 200 has good reflectance characteristics for EUV light.

[0055] The protective film 6 of this embodiment includes ruthenium (Ru) and an additive material. The additive material is at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). A thin film made of Ru is easily crystallized and has high crystallinity, and a thin film with high crystallinity is inferior in terms of density compared to an amorphous thin film. Therefore, by including an additive material in the protective film 6, the density of the protective film 6 can be increased, and the resistance of the protective film 6 to etching gas and to cleaning can be increased. Note that this protective film 6 is a protective film 6 corresponding to a second layer 64 described later. As described later, the protective film 6 can further include a first layer 62 in addition to the protective film 6 corresponding to the second layer 64 (see, for example, FIG. 2).

[0056] The content of the additive material in the protective film 6 of this embodiment 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. 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 added, it is possible to form a protective film 6 that has high resistance to etching gas and SPM cleaning and does not significantly reduce the EUV reflectance. Therefore, by setting the content of the additive material in the protective film 6 within a predetermined range, it is possible to suppress the reduction in the EUV light reflectance of the multilayer reflective film 5 with the protective film 6, and to increase the resistance to etching gas and cleaning. In addition, in the case of an additive material having a higher extinction coefficient k than ruthenium (Ru), it is preferable to adjust the extinction coefficient of the protective film 6 to 0.030 or less, and further 0.025 or less.

[0057] The content of the additive material in the protective film 6 can be the content of the additive material in the second layer 64 described below. That is, the content of the additive material in the second layer 64 can be 5 atomic % or more and less than 50 atomic %. The content of the additive material is preferably 10 atomic % or more, and more preferably 20 atomic % or more. The content of the additive material is preferably 40 atomic % or less, and more preferably 35 atomic % or less.

[0058] Next, the cases where the additive material contained in the protective film 6 is aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh), and hafnium (Hf) will be described. Note that the protective film 6 in the following description can be the second layer 64 described later.

[0059] When the material of the protective film 6 (or the second layer 64) is ruthenium (Ru) with aluminum (Al) added as an additive (for example, in the case of a RuAl film), the etching resistance of the protective film 6 to a mixed gas of a chlorine-based gas and an oxygen gas, the etching resistance to fluorine gas, and the cleaning resistance with sulfuric acid / hydrogen peroxide (SPM) are improved. If the Al concentration in the protective film 6 is too low, the effect of the addition cannot be obtained, and if it is too high, the extinction coefficient of the protective film 6 to EUV light increases, and the reflectance of the reflective mask 200 decreases. Moreover, if the Al concentration is too high, the resistance to fluorine gas decreases. Therefore, the Al concentration in the protective film 6 is preferably 5 atomic % or more and 40 atomic % or less, and more preferably 10 atomic % or more and 25 atomic % or less.

[0060] When yttrium (Y) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of a RuY film), the etching resistance of the protective film 6 to a mixed gas of a chlorine-based gas and an oxygen gas and to a fluorine-based gas are increased. If the Y concentration in the protective film 6 is too low, the effect of the addition cannot be obtained, and if it is too high, the cleaning resistance of the protective film 6 with sulfuric acid / hydrogen peroxide (SPM) is reduced. Therefore, the Y concentration in the protective film 6 is preferably 5 atomic % or more and less than 50 atomic %, and more preferably 10 atomic % or more and 40 atomic % or less.

[0061] When zirconium (Zr) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of a RuZr film), the etching resistance of the protective film 6 to a mixed gas of a chlorine-based gas and an oxygen gas is improved. If the Zr concentration in the protective film 6 is too low, the effect of the addition is not obtained, and if it is too high, the resistance of the protective film 6 to cleaning with sulfuric acid / hydrogen peroxide (SPM) is reduced. Furthermore, if the Zr concentration is too high, the resistance to chlorine-based gas is reduced. Therefore, the Zr concentration in the protective film 6 is preferably 5 atomic % or more and 45 atomic % or less, and more preferably 10 atomic % or more and 25 atomic % or less.

[0062] When rhodium (Rh) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of a RuRh film), the etching resistance of the protective film 6 to a mixed gas of a chlorine-based gas and an oxygen gas, the etching resistance to a chlorine-based gas, the etching resistance to a fluorine-based gas, and the cleaning resistance with sulfuric acid / hydrogen peroxide (SPM) are improved. If the Rh concentration in the protective film 6 is too low, the effect of the addition cannot be obtained, and if it is too high, the extinction coefficient k of the protective film 6 to EUV light becomes high, and the reflectance of the reflective mask 200 decreases. Therefore, the Rh concentration in the protective film 6 is preferably 15 atomic % or more and less than 50 atomic %, and more preferably 20 atomic % or more and 40 atomic % or less. FIG. 5 shows the relationship between the content of Rh (atomic %: horizontal axis) and the etching rate (nm / s: vertical axis) of the protective film by the mixed gas (Cl2+O2 gas) when Rh is added as an additive material to Ru. When the content of Rh is 20 atomic % or more, the rate at which the etching rate decreases starts to decrease, and when the content of Rh is 30 atomic % or more, this tendency becomes stronger, and when the content of Rh is 50 atomic % or more, the etching rate hardly changes. This shows that the etching resistance of the protective film can be improved by increasing the content of Rh. Therefore, it is preferable to increase the content of Rh until the rate at which the etching rate decreases starts to decrease. However, when the content of Rh exceeds 50 atomic %, the etching rate hardly changes, so there is no need to increase the content of Rh any more. Furthermore, when the content of Rh increases, the reflectance decreases, and when the content of Rh exceeds 50 atomic %, the desired reflectance cannot be obtained, so the content of Rh is preferably less than 50 atomic %. In this way, based on the knowledge obtained, it is possible to obtain an excellent multilayer reflective film-coated substrate by considering the improvement in etching resistance and the decrease in reflectance due to the addition of Rh.

[0063] When the protective film 6 (or the second layer 64) contains ruthenium (Ru) and rhodium (Rh), the following conditions are preferable. In this specification, the peak detected by the X-ray diffraction method is a peak when the measurement data of the diffracted X-ray intensity versus the diffraction angle 2θ using CuKα rays is illustrated, and the height of the peak when the background is subtracted from the measurement data (diffracted X-ray spectrum) can be at least twice the size of the background noise (width in the height direction of the noise) near the peak. The diffraction angle 2θ of the peak can be the diffraction angle 2θ (angle between the incident X-ray direction and the diffracted X-ray direction) that indicates the maximum value of the peak when the background is subtracted from the measurement data. Figure 6 shows the results of measuring the diffracted X-ray intensity (CPS) (vertical axis) versus the diffraction angle 2θ (horizontal axis) for a single film of ruthenium (Ru) (the number in parentheses indicates the crystal orientation), a single film of rhodium (Rh), and a RuRh film (films formed at ratios of Ru:Rh=70:30, Ru:Rh=50:50, and Ru:Rh=30:70) using an X-ray diffraction method using CuKα radiation. Both the single film of ruthenium (Ru) and the single film of rhodium (Rh) show relatively high CPS versus the diffraction angle 2θ, which indicates that the single films of ruthenium (Ru) and rhodium (Rh) have relatively high crystallinity. The CPS for the diffraction angle 2θ of the RuRh film changes depending on the ratio of Ru and Rh, and the CPS for the diffraction angle 2θ is lowest when Ru:Rh=30:70. This shows that the higher the Rh content in the RuRh film, the lower the crystallinity and the higher the density. However, as described above, the reflectance decreases as the Rh content increases, and the desired reflectance cannot be obtained if the Rh content exceeds 50 atomic %, so it is preferable that the Rh content is less than 50 atomic %. Furthermore, as shown in FIG. 6, when Ru:Rh=70:30, the diffraction angle was 42.0 degrees and the half-width was 0.62, when Ru:Rh=50:50, the diffraction angle was 41.9 degrees and the half-width was 0.64, and when Ru:Rh=30:70, the diffraction angle was 41.7 degrees and the half-width was 0.75. It is preferable that the diffraction angle 2θ has a peak in the range of 41.0 degrees or more and 43.0 degrees or less, and the half-width of the peak is 0.6 degrees or more. Since the half-width of a single film of ruthenium (Ru(002)) is slightly less than 0.6 degrees, if the half-width is less than 0.6 degrees, the crystallinity becomes high, which is undesirable. If the half-width of the peak is less than 0.6 degrees, the crystallinity becomes high and the density is lost, resulting in low etching resistance and cleaning resistance. In this way, the crystallinity can be controlled by the range of the diffraction angle 2θ of the peak and the half-width of the peak. By controlling the crystallinity, it is possible to increase the resistance to a specific etching gas and to increase the cleaning resistance of SPM and the like. The diffraction angle 2θ of the peak is preferably 41.0 degrees or more, more preferably 41.3 degrees or more. The diffraction angle 2θ of the peak is preferably 43.0 degrees or less, more preferably 42.0 degrees or less. The half-width of the peak is preferably 0.6 degrees or more, more preferably 0.65 degrees or more. The half-width of the peak is preferably 0.8 degrees or less.

[0064] Figure 7 shows the results of measuring the diffracted X-ray intensity (CPS) versus the diffraction angle 2θ for three types of films (with N amounts of 3sccm, 6sccm, and 12sccm) doped with nitrogen (N) during the formation of RuRh films (Ru:Rh=70:30) by X-ray diffraction using CuKα radiation. As shown in Figure 7, when the amount of N was 3sccm, the diffraction angle was 41.9 degrees and the half-width was 0.68, when the amount of N was 6sccm, the diffraction angle was 41.8 degrees and the half-width was 0.68, and when the amount of N was 12sccm, the diffraction angle was 41.6 degrees and the half-width was 0.78. The results for the other films are the same as those in Figure 6. The diffraction angle 2θ of the peak of the RuRh film (Ru:Rh=70:30) is theoretically expected to be 41.8 degrees. It can be seen that by adding nitrogen, the density of the protective film can be increased and the diffraction angle 2θ of the peak of the protective film can be brought closer to 41.8 degrees. By bringing the diffraction angle 2θ of the peak of the protective film closer to 41.8 degrees, it is possible to reduce the residual stress in the protective film. For this reason, 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 including N, the crystallinity of the protective film can be reduced and the denseness can be improved. In addition, the presence of nitrogen at the interface between the protective film and the film above the protective film and / or the film below the protective film, and the residual stress in the protective film can be reduced, thereby improving the adhesion therebetween and improving the cleaning resistance. Furthermore, by improving the adhesion, the blister resistance can also be improved (for example, when hydrogen gas is introduced into the atmosphere during exposure, the phenomenon in which the absorber film floats up and peels off from the surface of the protective film is called "blister").

[0065] When hafnium (Hf) is added as an additive material to ruthenium (Ru) as the material of the protective film 6 (or the second layer 64) (for example, in the case of a RuHf film), the etching resistance of the protective film 6 to a mixed gas of a chlorine-based gas and an oxygen gas and the cleaning resistance with sulfuric acid / hydrogen peroxide (SPM) are improved. If the Hf concentration in the protective film 6 is too low, the effect of the addition cannot be obtained, and if it is too high, the extinction coefficient k of the protective film 6 to EUV light becomes high, and the reflectance of the reflective mask 200 decreases. Therefore, the Hf concentration in the protective film 6 is preferably 5 atomic % or more and 30 atomic % or less, and more preferably 10 atomic % or more and 25 atomic % or less.

[0066] 2, the protective film 6 of the multilayer reflective film coated substrate 110 of this embodiment preferably includes, from the substrate 1 side, a first layer 62 and a second layer 64. When the protective film 6 includes the first layer 62 and the second layer 64, the second layer 64 can be the same thin film as the protective film 6 described above.

[0067] When the multilayer reflective film 5 is a Mo / Si periodic laminated film, Mo is easily oxidized by the atmosphere, and the reflectance of the multilayer reflective film 5 may decrease. For this reason, the top layer of the multilayer reflective film 5 is made of a Si layer. When the Si film comes into contact with the protective film 6 made of Ru, silicon (Si) easily diffuses into the protective film 6. That is, Si from the Si layer of the multilayer reflective film 5 moves and diffuses between the grain boundaries of the Ru-based protective film 6 over time (and forms Ru silicide (RuSi)), reaches the surface layer of the Ru-based protective film 6, and is oxidized by a cleaning solution or gas to generate SiO2. Furthermore, if the protective film 6 is not dense, the cleaning solution or gas penetrates into the protective film 6, and SiO2 is generated inside the protective film 6 (inside or under the protective film 6). Since the adhesion between Ru and SiO2 is low, the film may peel off due to repeated cleaning during the manufacturing process of the reflective mask 200 or when used after completion as a product. By the protective film 6 having the predetermined first layer 62, the diffusion of silicon (Si) from the multilayer reflective film 5 to the protective film 6 can be suppressed.

[0068] In order 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 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) into the protective film 6 can be suppressed more reliably.

[0069] The proportion of Ru in the Ru compound of the first 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 %.

[0070] When the protective film 6 includes a first layer 62 and a second layer 64, the second layer 64 can be the same thin film as the above-mentioned protective film 6. That is, the second layer 64 can include ruthenium (Ru) and at least one additive material selected from aluminum (Al), yttrium (Y), zirconium (Zr), rhodium (Rh) and hafnium (Hf). The first layer 62 and the second layer 64 can also be made of the same material with different composition ratios.

[0071] When the first layer 62 is a RuTi-containing film (e.g., a RuTi film or a RuTiN film; the same applies to other RuY-containing films, etc.), the second layer 64 is preferably a RuY-containing film, a RuZr-containing film, or a RuRh-containing film. When the first layer 62 is a RuZr-containing film, the second layer 64 is preferably a RuAl-containing film, a RuY-containing film, a RuZr-containing film, or a RuRh-containing film. In this case, the first layer 62 can more reliably suppress the diffusion of silicon (Si) into the protective film 6, and the second layer 64 can more reliably increase the resistance of the protective film 6 to etching gas and cleaning.

[0072] The protective film 6 (the first layer 62 and / or the second layer 64) may contain at least one selected from N, C, O, H, and B, within the range in which the effects of this embodiment can be obtained. In order to reduce the crystallinity of the thin film and make it amorphous, the protective film 6 (the first layer 62 and / or the second layer 64) preferably contains nitrogen (N) and / or oxygen (O).

[0073] The protective film 6 (first layer 62 and / or second layer 64) of the multilayer reflective film coated substrate 110 of this embodiment preferably further contains nitrogen (N). When the protective film 6 (first layer 62 and / or second layer 64) further contains nitrogen (N), the crystallinity can be reduced. As a result, the thin film can be densified, and the resistance to etching gas and cleaning can be further increased. The ratio of N in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably more than 1 atomic % and not more than 20 atomic %, and more preferably 3 atomic % or more and not more than 10 atomic %.

[0074] The protective film 6 (first layer 62 and / or second layer 64) of the multilayer reflective film coated substrate 110 of this embodiment preferably further contains oxygen (O). When the protective film 6 (first layer 62 and / or second layer 64) further contains oxygen (O), the crystallinity can be reduced. As a result, the thin film can be densified, and the resistance to etching gas and cleaning can be further increased. The ratio of O in the Ru compound of the protective film 6 (first layer 62 and / or second layer 64) is preferably more than 1 atomic % and not more than 20 atomic %, and more preferably 3 atomic % or more and 10 atomic % or less.

[0075] In the multilayer reflective film coated substrate 110 of this embodiment, the Ru content of the second layer 64 is preferably lower than the Ru content of the first layer 62. For example, when the first layer 62 is an RuTi film and the second layer 64 is an RuRh film, even if the Ti content of the RuTi film of the first layer 62 is relatively 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 lower than the Ru content of the first layer 62, the resistance to etching gas and cleaning can be further increased, and the diffusion of silicon (Si) into the protective film 6 can be suppressed.

[0076] In the multilayer reflective film coated substrate 110 of this embodiment, the refractive index of the second layer 64 is preferably smaller than the refractive index of the first layer 62. As a result, a substrate with a protective film (multilayer reflective film coated substrate 110 having a protective film 6) can be produced without decreasing the reflectance 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, and more preferably 0.885 or less.

[0077] The above-mentioned protective film 6 (first layer 62 and / or second layer 64) can be formed by various known methods. Examples of the method for forming the protective film 6 include ion beam sputtering, sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition. When the first layer 62 is formed by ion beam sputtering, it is preferable because it can be formed continuously after the formation of the multilayer reflective film 5. Furthermore, when the protective film 6 (first layer 62 and / or second layer 64) contains nitrogen and / or oxygen, it is preferable to use reactive sputtering in order to perform stable film formation.

[0078] When the protective film 6 includes the first layer 62 and the second layer 64, a heat treatment can be performed after forming the first layer 62 and the second layer 64, or after forming the absorber film 7. In this heat treatment, heating can be performed at a temperature higher than the pre-bake temperature (about 110°C) of the resist film 8 in the manufacturing process of the reflective mask blank 100. Specifically, the temperature condition of the heat treatment is usually 160°C or higher and 300°C or lower, and preferably 180°C or higher and 250°C or lower.

[0079] When the above-mentioned heat treatment process is performed, at least a portion of the metal constituting the first layer 62 is diffused into the second layer 64, and further, a multilayer reflective film-coated substrate 110 is obtained in which a compositionally gradient region exists between the first layer 62 and the second layer 64 in which the content of the metal component constituting the first layer 62 continuously decreases toward the second layer 64.

[0080] The thickness of the protective film 6 (the total of the first layer 62 and the second layer 64) is not particularly limited as long as it can function as the protective film 6. From the viewpoint of the reflectance of EUV light, the thickness of the protective film 6 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm. The thickness of the first layer 62 is preferably 0.5 nm to 2.0 nm, and more preferably 1.0 nm to 1.5 nm. The thickness of the second layer 64 is preferably 1.0 nm to 7.0 nm, and more preferably 1.5 nm to 4.0 nm.

[0081] <Reflective mask blank 100> The reflective mask blank 100 of this embodiment will be described below. The reflective mask blank 100 has an absorber film 7 on the protective film 6 of the multilayer reflective film coated substrate 110 described above.

[0082] <<Absorber membrane 7>> The absorber film 7 of the reflective mask blank 100 of this embodiment is formed on the multilayer reflective film 5 (on the protective film 6 when the protective film 6 is formed). The basic function of the absorber film 7 is to absorb EUV light. The absorber film 7 may be an absorber film 7 intended to absorb EUV light, or may be an absorber film 7 having a phase shift function that also takes into account the phase difference of EUV light. The absorber film 7 having a phase shift function absorbs EUV light and reflects a part of it to shift the phase. That is, in the reflective mask 200 in which the absorber film 7 having a phase shift function is patterned, the absorber film 7 absorbs EUV light to reduce the light, while reflecting a part of the light at a level that does not adversely affect pattern transfer. In addition, in the region (field portion) in which the absorber film 7 is not formed, the 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 having a phase shift function and the reflected light from the field portion. The absorber film 7 having a phase shift function is formed so that the phase difference between the reflected light from the absorber film 7 and the reflected light from the multilayer reflective film 5 is 170 degrees to 190 degrees. Light beams with an inverted phase difference of about 180 degrees interfere with each other at the pattern edge, improving the image contrast of the projected optical image. With this improvement in image contrast, the resolution increases, and various exposure tolerances such as exposure dose tolerance and focus tolerance can be increased.

[0083] The absorber film 7 may be a single layer film, or may be a multilayer film consisting of multiple films (for example, a lower absorber film and an upper absorber film). In the case of a single layer film, the number of steps during mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constant and film thickness of the upper absorber film can be appropriately set so that it becomes an anti-reflection film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. In addition, if a film to which oxygen (O) and nitrogen (N), which improve oxidation resistance, are added is used as the upper absorber film, the stability over time is improved. In this way, various functions can be added by making the absorber film 7 a multilayer film. In the case of an absorber film 7 having a phase shift function, the range of adjustment on the optical surface can be increased by making it a multilayer film, making it easier to obtain a desired reflectance.

[0084] The material of 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 can be etched by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity with respect to the protective film 6 (second layer 64). As a material having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or a compound thereof, can be preferably used.

[0085] The absorber film 7 can be formed by magnetron sputtering such as DC sputtering and RF sputtering. For example, the absorber film 7 made of a tantalum compound or the like can be formed by a reactive sputtering method using a target containing tantalum and boron and argon gas to which oxygen or nitrogen is added.

[0086] The tantalum compound for forming the absorber film 7 includes an alloy of Ta and the above-mentioned metal. When the absorber film 7 is an alloy of Ta, the crystal state of the absorber film 7 is preferably an amorphous or microcrystalline structure in terms of smoothness and flatness. If the surface of the absorber film 7 is not smooth and flat, the edge roughness of the absorber pattern 7a increases, and the dimensional accuracy of the pattern may deteriorate. The surface roughness of the absorber film 7 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in terms of root-mean-square roughness (Rms).

[0087] As the tantalum compound for forming the absorber film 7, a compound containing Ta and B, a compound containing Ta and N, a compound containing Ta, O and N, a compound containing Ta and B and further containing at least one of O and N, a compound containing Ta and Si, a compound containing Ta, Si and N, a compound containing Ta and Ge, and a compound containing Ta, Ge and N, etc. can be used.

[0088] Ta is a material that has a large absorption coefficient of EUV light and can be easily dry etched with a chlorine-based gas or a fluorine-based gas. Therefore, it can be said that Ta is a material for the absorber film 7 that is excellent in processability. Furthermore, by adding B, Si and / or Ge, etc. to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 7 can be improved. Furthermore, by adding N and / or O to Ta, the resistance of the absorber film 7 to oxidation is improved, and therefore the effect of improving stability over time can be obtained.

[0089] <<Backside conductive film 2>> A backside conductive film 2 for electrostatic chuck is formed on the second main surface (backside main surface) of the substrate 1 (opposite to the surface on which the multilayer reflective film 5 is formed, and on the intermediate layer if an intermediate layer such as a hydrogen penetration suppression film is formed on the substrate 1). The sheet resistance required for the backside conductive film 2 for electrostatic chuck is usually 100 Ω / □ (Ω / square) or less. The method for forming the backside conductive film 2 is, for example, magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The chromium (Cr)-containing material of the backside conductive film 2 is preferably a Cr compound containing at least one element selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The tantalum (Ta)-containing material of the back surface conductive film 2 is preferably Ta, an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON. The thickness of the back surface conductive film 2 is not particularly limited as long as it satisfies the function for electrostatic chuck, but is usually 10 nm to 200 nm. In addition, the back surface 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 surface conductive film 2 is adjusted to obtain a flat reflective mask blank 100 by balancing the stress from various films formed on the first main surface side.

[0090] Note that, before forming the above-mentioned absorber film 7, a back surface conductive film 2 can be formed on the multilayer reflective film-coated substrate 110. The multilayer reflective film-coated substrate 110 includes a case in which the back surface conductive film 2 is disposed on the second main surface of the multilayer reflective film-coated substrate 110 shown in Figures 1 and 2. In addition, the reflective mask blank 100 does not necessarily need to include the back surface conductive film 2.

[0091] <Etching mask film 9> An etching mask film 9 may be formed on the absorber film 7. The material of the etching mask film 9 is a material having a high etching selectivity of the absorber film 7 to the etching mask film 9. Here, the "etching selectivity of B to A" refers to the ratio of the etching rate of A, which is a layer that is not to be etched (a layer that serves as a mask), to B, which is a layer that is to be etched. Specifically, it is specified by the formula "etching selectivity of B to A=etching rate of B / etching rate of A". In addition, "high selectivity" refers to a high selectivity value as defined above with respect to a comparison target. The etching selectivity of the absorber film 7 to the etching mask film 9 is preferably 1.5 or more, more preferably 3 or more.

[0092] Materials having a high etching selectivity of the absorber film 7 to the etching mask film 9 include materials of chromium and chromium compounds. When the absorber film 7 is etched with a fluorine-based gas, materials of chromium and chromium compounds can be used. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. Also, when the absorber film 7 is etched with a chlorine-based gas that does not substantially contain oxygen, materials of silicon and silicon compounds can be used. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as materials such as metal silicon (metal silicide) and metal silicon compounds (metal silicide compounds) containing metal in silicon and silicon compounds. Examples of metal silicon compounds include materials containing metal, Si, and at least one element selected from N, O, C, and H.

[0093] The reflective mask blank 100 of this embodiment preferably includes an etching mask film 9 containing chromium (Cr) on the absorber film 7. The etching mask film 9 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and further preferably is a CrO-based film containing chromium and oxygen (a CrO film, a CrON film, a CrOC film, or a CrOCN film).

[0094] By configuring the protective film 6 as described above, it is possible to suppress damage to the protective film 6 when the etching mask film 9 containing chromium (Cr) is peeled off by dry etching using a mixed gas of chlorine gas and oxygen gas.

[0095] 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, when the etching mask film 9 is made of silicon or a silicon compound, damage to the protective film 6 when the etching mask film 9 is peeled off by dry etching using a fluorine-based gas can be suppressed. Therefore, the range of materials and etching conditions for the absorber film 7 and / or the etching mask film 9 can be broadened. Since damage to the protective film 6 caused by dry etching using a fluorine-based gas can be suppressed, the multilayer reflective film-coated substrate 110 and the reflective mask blank 100 manufactured by the manufacturing method of this embodiment can be provided with 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 is drawn (exposed) on this resist film 8, and then developed and rinsed to form a predetermined resist pattern, and the absorber film 7 is etched using this resist pattern as a mask to form the absorber pattern.

[0096] The thickness of the etching mask film 9 is desirably 3 nm or more from the viewpoint of obtaining the function as an etching mask for accurately forming a transfer pattern in the absorber film 7. Moreover, the thickness of the etching mask film 9 is desirably 15 nm or less from the viewpoint of making the thickness of the resist film 8 thin.

[0097] <Other thin films> The multilayer reflective film-coated substrate 110 and the reflective mask blank 100 of this embodiment preferably have a hydrogen penetration suppression film between the glass substrate, which is the substrate 1, and the back surface conductive film 2 containing tantalum or chromium, for suppressing penetration of hydrogen from the substrate 1 into the back surface conductive film 2. The presence of the hydrogen penetration suppression film can suppress the incorporation of hydrogen into the back surface conductive film 2, and can suppress an increase in the compressive stress of the back surface conductive film 2.

[0098] The material of the hydrogen penetration suppression film may be any type of material that is difficult for hydrogen to permeate and can suppress the penetration of hydrogen from the substrate 1 to the back surface conductive film 2. Specific examples of the material of the hydrogen penetration suppression film 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 penetration suppression film may be a single layer of these materials, or may be a multiple layer or composition gradient film.

[0099] <Reflection mask 200> The present embodiment is a reflective mask 200 having an absorber pattern 7a on a multilayer reflective film 5 by patterning the absorber film 7 in the above-mentioned reflective mask blank 100. By using the reflective mask blank 100 of the present embodiment, a reflective mask 200 can be obtained having a protective film 6 that is highly resistant to etching gases and highly resistant to cleaning.

[0100] A reflective mask 200 is manufactured using the reflective mask blank 100 of this embodiment. Only an outline will be given here, and a detailed description will be given later in examples with reference to the drawings.

[0101] A reflective mask blank 100 is prepared, and a resist film 8 (not necessary if the reflective mask blank 100 is provided with a resist film 8) is formed on the outermost surface of its first main surface (on top of an etching mask film 9 formed on an absorber film 7, as described in the following examples), and a desired pattern such as a circuit pattern is drawn (exposed) on this resist film 8, which is then developed and rinsed to form a predetermined resist pattern 8a.

[0102] The etching mask film 9 is dry-etched using the resist pattern 8a as a mask to form an etching mask pattern 9a. Next, the absorber film 7 is dry-etched using the etching mask pattern 9a as a mask to form an absorber pattern 7a. The etching gas for dry-etching the absorber film 7 may be selected from chlorine-based gases such as Cl2, SiCl4, and CHCl3, mixed gases containing chlorine-based gas and O2 at a predetermined ratio, mixed gases containing chlorine-based gas and He at a predetermined ratio, mixed gases containing chlorine-based gas and Ar at a predetermined ratio, fluorine-based gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2, and mixed gases containing fluorine-based gas and O2 at a predetermined ratio. If oxygen is contained in the etching gas in the final stage of etching, the surface of the Ru-based protective film 6 will become rough. For this reason, it is preferable to use an etching gas that does not contain oxygen in the overetching stage in which the Ru-based protective film 6 is exposed to etching. After the absorber pattern 7a is formed, the etching mask pattern 9a can be removed with a mixed gas of a chlorine-based gas and an oxygen gas or a fluorine-based gas.

[0103] Thereafter, the resist pattern 8a is removed by ashing or using a resist stripper, to produce an absorber pattern 7a on which a desired circuit pattern is formed.

[0104] Through the above steps, the reflective mask 200 of this embodiment can be obtained.

[0105] <Method of Manufacturing Semiconductor Device> This embodiment is a method for manufacturing a semiconductor device, which includes a step of forming a transfer pattern on a transferee by performing a lithography process using an exposure apparatus using the above-mentioned reflective mask 200. Specifically, the above-mentioned reflective mask 200 is set in an exposure apparatus having an exposure light source that emits EUV light, and the transfer pattern can be transferred to a resist film formed on the transferee substrate. According to the method for manufacturing a semiconductor device of this embodiment, a reflective mask 200 that does not adversely affect the performance of the reflective mask 200 even if impurities (trace materials) are contained in the thin film of the reflective mask 200 can be used, so that a semiconductor device having a fine and highly accurate transfer pattern can be manufactured.

[0106] Specifically, a desired transfer pattern can be formed on a semiconductor substrate by EUV exposure using the reflective mask 200 of the present embodiment. In addition to this lithography process, various steps such as etching of the film to be processed, formation of an insulating film or conductive film, introduction of a dopant, or annealing can be carried out to manufacture a semiconductor device having a desired electronic circuit formed thereon with a high yield. EXAMPLES

[0107] Examples will now be described, but the present invention is not limited to these examples.

[0108] (Example) As an example, a multilayer reflective film-coated substrate 110 was prepared in which a multilayer reflective film 5 and a protective film 6 were formed on the first main surface of a substrate 1. Table 1 shows the material and composition of the protective film 6 formed as an example. The multilayer reflective film-coated substrate 110 of each example was prepared in the same manner except that the type of protective film 6 was different. The protective film 6 used in each example is as described below.

[0109] The protective film 6 in Example 1-1 and Example 1-2 is a RuAl film, and the protective film 6 in Example 1-3 is a RuAlN film (see FIG. 1). The protective film 6 in Example 1-4 is a protective film 6 consisting of two layers, a first layer 62 of a RuZr film and a second layer 64 of a RuAl film (see FIG. 2).

[0110] The protective film 6 in Example 2-1 and Example 2-2 is a RuY film, and the protective film 6 in Example 2-3 is a RuYN film (see FIG. 1). The protective film 6 in Example 2-4 is a protective film 6 consisting of two layers, a first layer 62 of a RuTi film and a second layer 64 of a RuY film (see FIG. 2).

[0111] The protective film 6 in Example 3-1 and Example 3-2 is a RuZr film, and the protective film 6 in Example 3-3 is a RuZrN film (see FIG. 1). The protective film 6 in Example 3-4 is a protective film 6 consisting of two layers, a first layer 62 of a RuZr film and a second layer 64 of a RuZr film (see FIG. 2).

[0112] The protective film 6 in Example 4-1 and Example 4-2 is a RuRh film, and the protective film 6 in Example 4-3 is a RuRhN film (see FIG. 1). The protective film 6 in Example 4-4 is a protective film 6 consisting of two layers, a first layer 62 of a RuTi film and a second layer 64 of a RuRh film (see FIG. 2).

[0113] The protective film 6 in Example 5-1 and Example 5-2 is a RuHf film, and the protective film 6 in Example 5-3 is a RuHfN film (see FIG. 1). The protective film 6 in Example 5-4 is a protective film 6 consisting of two layers, a first layer 62 of a RuZr film and a second layer 64 of a RuHf film (see FIG. 2).

[0114] The multilayer reflective film coated substrate 110 of this example was produced as follows.

[0115] A SiO2-TiO2-based glass substrate, which is a low-thermal expansion glass substrate having a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) with both the first and second main surfaces polished, was prepared as substrate 1. In order to obtain a flat and smooth main surface, polishing was performed using a rough polishing process, a precision polishing process, a localized polishing process, and a touch polishing process.

[0116] Next, a multilayer reflective film 5 was formed on the first main surface of the substrate 1. The multilayer reflective film 5 was a periodic multilayer reflective film 5 made of Si and Mo in order to make the multilayer reflective film 5 suitable for EUV light with a wavelength of 13.5 nm. Specifically, a Si target and a Mo target were used as the high refractive index material target and the low refractive index material target. Krypton (Kr) ion particles were supplied from an ion source to these targets to perform ion beam sputtering, thereby alternately laminating Si layers and Mo layers on the substrate 1.

[0117] Here, the sputtered particles of Si and Mo were incident at an angle of 30 degrees with respect to the normal to the first main surface of the substrate 1. First, a Si layer was formed to a thickness of 4.2 nm, and then a Mo layer was formed to a thickness of 2.8 nm. This constitutes one cycle, and 40 cycles were similarly stacked, and finally a Si layer was formed to a thickness of 4.0 nm to form the multilayer reflective film 5. Therefore, the material of the bottom layer of the multilayer reflective film 5, i.e., the layer closest to the substrate 1, is Si, and the material of the top layer of the multilayer reflective film 5, i.e., the layer in contact with the protective film 6, is also Si.

[0118] Next, the protective film 6 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 of Example 1-1, a RuAl mixed sintered target having the composition shown in Table 1 was used as the target for the ion beam sputtering. In an Ar gas atmosphere, the protective film 6 of Example 1-1 made of a RuAl film having the composition shown in Table 1 was formed to the thickness shown in Table 1 by ion beam sputtering using a RuAl mixed sintered target. Here, the sputtered particles of Ru and Al were incident at an angle of 30 degrees with respect to the normal line of the first main surface of the substrate 1. The protective film 6 of the other examples was also formed in the same manner as in Example 1-1.

[0119] The protective films 6 in Examples 1-3, 2-3, 3-3, 4-3, and 5-3 contain nitrogen (N). These protective films 6 were formed by reactive sputtering in a mixed gas atmosphere of Ar gas and N2 gas.

[0120] Moreover, the protective film 6 in Examples 1-4, 2-4, 3-4, 4-4, and 5-4 is a protective film 6 consisting of two layers, a first layer 62 and a second layer 64. Therefore, in these Examples, the second layer 64 was formed after the first layer 62 was formed. Table 2 shows the composition and film thickness of the first layer 62 in these Examples. Furthermore, Table 1 shows the composition and film thickness of the second layer 64 in these Examples.

[0121] In this manner, the multilayer reflective film coated substrate 110 of the example was manufactured.

[0122] Comparative Example 1 A multilayer reflective film-coated substrate 110 of Comparative Example 1 was manufactured in the same manner as in Example 1-1, except that the material of the protective film 6 was a single layer made of Ru only. The protective film 6 of Comparative Example 1 was formed by ion beam sputtering using a Ru target in an Ar gas atmosphere, to a thickness shown in Table 1.

[0123] (Reflective mask blank 100) A reflective mask blank 100 including an absorber film 7 and an etching mask film 9 was produced using the multilayer reflective film coated substrate 110 of the above-mentioned Example and Comparative Example 1. The method for producing the reflective mask blank 100 will be described below.

[0124] An absorber film 7 was formed on the protective film 6 of the multilayer reflective film-coated substrate 110 by DC magnetron sputtering. The absorber film 7 was a laminated film consisting of two layers, a TaN film as an absorbing layer and a TaO film as a low-reflection layer. A TaN film was formed as an absorbing layer on the surface of the protective film 6 of the multilayer reflective film-coated substrate 110 by DC magnetron sputtering. This TaN film was formed by placing the multilayer reflective film-coated substrate 110 opposite a Ta target and by reactive sputtering in a mixed gas atmosphere of Ar gas and N2 gas. Next, a TaO film (low-reflection layer) was further formed on the TaN film by DC magnetron sputtering. This TaO film was formed by placing the multilayer reflective film-coated substrate 110 opposite a Ta target and by reactive sputtering in a mixed gas atmosphere of Ar gas and O2 gas, similar to the TaN film.

[0125] The composition (atomic ratio) of the TaN film was Ta:N=70:30, and the thickness was 48 nm, while the composition (atomic ratio) of the TaO film was Ta:O=35:65, and the thickness was 11 nm.

[0126] Next, an etching mask film 9 made 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 in a mixed gas atmosphere of Ar gas, N2 gas, and CO2 gas. The etching mask film 9 was formed to a thickness of 5 nm.

[0127] Next, a back surface conductive film 2 made of CrN was formed on the second main surface (rear main surface) of the substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions: Conditions for forming the back surface conductive film 2: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90 atomic %, N: 10 atomic %), film thickness 20 nm.

[0128] In this manner, the reflective mask blanks 100 of the example and comparative example 1 were manufactured.

[0129] (Reflective mask 200) Next, a reflective mask 200 was manufactured using the reflective mask blanks 100 of the example and comparative example 1. The manufacture of the reflective mask 200 will be described with reference to FIG.

[0130] FIG. 8(a) is a schematic cross-sectional view of an exemplary reflective mask blank 100 described herein (e.g., with reference to FIG. 4). First, as shown in FIG. 8(b), a resist film 8 was formed on the etching mask film 9 of the reflective mask blank 100. Then, a desired pattern such as a circuit pattern was drawn (exposed) on the resist film 8, and the resist film 8 was developed and rinsed to form a predetermined resist pattern 8a (FIG. 8(c)). Next, the etching mask film 9 was dry-etched using a mixture gas of Cl2 gas and O2 gas (Cl2+O2 gas) with the resist pattern 8a as a mask to form an etching mask pattern 9a (FIG. 8(d)). The resist pattern 8a was peeled off by oxygen ashing. Using the etching mask pattern 9a as a mask, the TaO film (low reflective layer) of the absorber film 7 was dry-etched using CF4 gas, and subsequently, the TaN film was dry-etched using Cl2 gas to form an absorber pattern 7a (FIG. 8(e)).

[0131] Thereafter, the etching mask pattern 9a was removed by dry etching using a mixed gas of Cl2 gas and O2 gas (Cl2+O2 gas) (FIG. 8(f)). Finally, wet cleaning was performed using pure water (DIW) to manufacture the reflective masks 200 of the example and comparative example 1.

[0132] In this manner, the reflective masks 200 of the example and comparative example 1 were manufactured.

[0133] (Evaluation of the Reflective Mask 200 of the Example and Comparative Example 1) For each of the above-mentioned Example and Comparative Example 1, the influence of dry etching when removing the etching mask pattern 9a was evaluated.

[0134] Specifically, for each of the above-mentioned Example and Comparative Example 1, a mask blank having a structure shown in FIG. 4 was manufactured, and an etching mask pattern 9a and an absorber pattern 7a corresponding to FIG. 8(e) were formed in the manufacturing process of the above-mentioned reflective mask 200. However, the pattern shape of the absorber pattern 7a for evaluation was a pattern having a shape that widely exposes the surface of the protective film 6 so that the reflectance of EUV light at the exposed portion of the surface of the protective film 6 can be measured. After the absorber pattern 7a was formed, the reflectance (reflectance before etching) of the surface of the protective film 6 to EUV light having a wavelength of 13.5 nm was measured. Next, the etching mask pattern 9a of the CrOCN film was removed by dry etching using a mixed gas of Cl2 gas and O2 gas (Cl2:O2=9:1) (FIG. 8(f)). After the etching mask pattern 9a was removed by etching, the reflectance (reflectance after etching) of the surface of the protective film 6 to EUV light having a wavelength of 13.5 nm was measured. The change in reflectance before and after removal of the etching mask pattern 9a by etching (reflectance after etching / reflectance before etching) is shown in column A of Table 3. The change in reflectance is shown as a ratio when Comparative Example 1 is taken as 1.

[0135] In addition, the change in thickness of the protective film 6 during dry etching using the above-mentioned mixed gas of Cl2 gas and O2 gas (Cl2+O2 gas) was measured, and the etching rate of each material in the protective film 6 was calculated as a ratio when the etching rate of the Ru film in the protective film 6 by the mixed gas was set to 1. Column B of Table 3 shows the etching rate ratio of the protective film 6 by the mixed gas.

[0136] As is clear from Table 3, in all the examples, the change in reflectance before and after removal of the etching mask pattern 9a by etching was small compared to Comparative Example 1. Also, in all the examples, the etching rate of the protective film 6 by the mixed gas (Cl2+O2 gas) was small compared to Comparative Example 1. Therefore, it was revealed that the protective film 6 in the examples of this embodiment has high resistance to the etching gas for removing the etching mask film 9.

[0137] In addition, the resistance of the protective film 6 to cleaning with sulfuric acid / hydrogen peroxide (SPM) was measured separately. As a result, in all the examples, the change in film thickness before and after cleaning was small compared to Comparative Example 1, and the fluctuation in reflectance to EUV light was also small, making it clear that the protective film 6 has high resistance to cleaning.

[0138] Table 4 shows the rate of film thickness reduction measured when SPM cleaning was performed under the following cleaning conditions, and shows the ratio when the value for Comparative Example 1 (Ru film) was taken as 1. Cleaning solution H2SO4:H2O2=2:1 (weight ratio) Washing temperature: 120℃ Washing time: 10 minutes

[0139] As is clear from Table 4, the SPM cleaning resistance of Example 4-2 (Ru:Rh=70:30) and Example 4-3 (Ru:Rh:N=65:30:5) is higher than the SPM cleaning resistance of Example 4-1 (Ru:Rh=80:20). Note that since the protective film of Example 4-4 is the same as that of Example 4-2, the ratio of the film reduction rate when Comparative Example 1 (Ru film) is set to 1 is also the same as that of Example 4-2.

[0140] (Semiconductor device manufacturing) The reflective mask 200 manufactured using the multilayer reflective film coated substrate 110 of the embodiment was set in an EUV scanner, and EUV exposure was performed on a wafer having a film to be processed and a resist film formed on a semiconductor substrate. Then, a resist pattern was formed on the semiconductor substrate having the film to be processed formed thereon by developing the exposed resist film.

[0141] The reflective mask 200 manufactured using the multilayer reflective film-coated substrate 110 of the embodiment has a protective film that is highly resistant to etching gas and highly resistant to cleaning, making it possible to form a fine and highly accurate transfer pattern (resist pattern).

[0142] This resist pattern is transferred to the film to be processed by etching, and then various processes such as forming insulating and conductive films, introducing dopants, and annealing are carried out, making it possible to manufacture semiconductor devices with the desired characteristics with a high yield.

[0143] [Table 1]

[0144] [Table 2]

[0145] [Table 3]

[0146] [Table 4] [Explanation of symbols]

[0147] 1 Mask blank substrate (substrate) 2. Backside conductive film 5 Multilayer reflective film 6 Protective film 7. Absorber membrane 7a Absorber pattern 8. Resist film 8a Resist pattern 9 Etching mask film 9a Etching mask pattern 62 First Layer 64 Second Layer 100 Reflective mask blank 110 Multilayer reflective film substrate 200 Reflective mask

Claims

1. A multilayer reflective film-coated substrate having a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, 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 atomic %.

2. the protective film includes a first layer and a second layer from the substrate side, the first layer includes ruthenium (Ru) and at least one 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); 2. The multilayer reflective film coated substrate according to claim 1, wherein the second layer contains the ruthenium (Ru) and the additive material.

3. 3. The multilayer reflective film coated substrate according to claim 1, wherein the protective film, the first layer, or the second layer further contains nitrogen (N).

4. 4. The multilayer reflective film coated substrate according to claim 2, wherein the Ru content of the second layer is less than the Ru content of the first layer.

5. 5. A reflective mask blank comprising an absorber film on the protective film of the multilayer reflective film-coated substrate according to claim 1.

6. The reflective mask blank according to claim 5 , further comprising an etching mask film containing chromium (Cr) on the absorber film.

7. 7. A reflective mask comprising an absorber pattern formed by patterning the absorber film in the reflective mask blank according to claim 5.

8. The etching mask film of the reflective mask blank according to claim 6 is patterned to form an etching mask pattern; The absorber film is patterned using the etching mask pattern as a mask to form an absorber pattern; The method for producing a reflective mask comprises removing the etching mask pattern with a mixed gas of a chlorine-based gas and an oxygen gas.

9. 8. A method for manufacturing a semiconductor device, comprising the steps of: setting the reflective mask according to claim 7 in an exposure apparatus having an exposure light source that emits EUV light; and transferring a transfer pattern onto a resist film formed on a transfer substrate.

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