Reflection type mask blank, reflection type mask, substrate with conductive film, and method for manufacturing semiconductor device

Abstract

To provide a reflection type mask blank which can suppress change with time of a film quality of a thin metal film, a reflection type mask, a substrate with a conductive film, and a method for manufacturing a semiconductor device.SOLUTION: A reflection type mask blank 100 includes a substrate 10, a multilayer reflection film 12 on the substrate 10, and a laminated film 16 on the multilayer reflection film 12. The laminated film 16 includes an uppermost layer 20, and a lower layer 18 other than the layer. The thickness of the uppermost layer 20 is 0.5 nm or more and less than 5 nm. The uppermost layer 20 includes at least one metal element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo) and niobium (Nb), and at least additive element selected from hydrogen (H) and deuterium (D). The total content of the metal element on the uppermost layer is 95 atom% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a reflective mask blank, a reflective mask, and a substrate with a conductive film. The present invention also relates to a method for manufacturing a semiconductor device using a reflective mask.

Background Art

[0002] The types of light sources of exposure apparatuses in semiconductor device manufacturing have evolved while gradually shortening the wavelength, such as g-line with a wavelength of 436 nm, i-line with a wavelength of 365 nm, KrF laser with a wavelength of 248 nm, ArF laser with a wavelength of 193 nm, and extreme ultraviolet light (EUV: Extreme Ultra Violet) with a wavelength near 13.5 nm has been developed to achieve finer pattern transfer. In EUV lithography, since there are few materials transparent to EUV light, a reflective mask is used. In this reflective mask, a multilayer reflective film that reflects exposure light is formed on a low thermal expansion substrate, and a mask structure in which a desired transfer pattern is formed on a protective film for protecting the multilayer reflective film is used as the basic structure. Also, from the configuration of the transfer pattern, typically, there are a binary type reflective mask composed of a relatively thick absorber pattern that sufficiently absorbs EUV light, and a phase shift type reflective mask (halftone phase shift type reflective mask) composed of a relatively thin absorber pattern that attenuates EUV light by light absorption and generates reflected light whose phase is almost inverted (phase inversion of about 180°) with respect to the reflected light from the multilayer reflective film. This phase shift type reflective mask, like a transmissive optical phase shift mask, has an effect of improving resolution because a high transfer optical image contrast can be obtained by the phase shift effect. Also, since the film thickness of the absorber pattern (phase shift pattern) of the phase shift type reflective mask is thin, a fine phase shift pattern can be formed with high accuracy.

[0003] Technologies related to such reflective masks for EUV lithography and mask blanks for manufacturing them are disclosed in Patent Documents 1 to 3.

[0004] Patent Document 1 describes a reflective mask blank for EUV lithography in which at least a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate. Specifically, in the reflective mask blank of Patent Document 1, the absorber layer contains tantalum (Ta), nitrogen (N), and hydrogen (H), and the total content ratio of Ta and N in the absorber layer is 50 to 99.9 at%, and the content ratio of H is 0.1 to 50 at%. Patent Document 1 describes that in the reflective mask blank of Patent Document 1, the crystalline state of the absorber layer film becomes amorphous, and the stress and surface roughness are also reduced.

[0005] Patent Document 2 describes a reflective mask blank for EUV lithography in which a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate. Specifically, in the reflective mask blank of Patent Document 2, the absorber layer contains at least tantalum (Ta), boron (B), nitrogen (N), and hydrogen (H), and in the absorber layer, the content ratio of B is 1 at% or more and less than 5 at%, the content ratio of H is 0.1 to 5 at%, the total content ratio of Ta and N is 90 to 98.9 at%, and the composition ratio of Ta to N (Ta:N) is 8:1 to 1:1. As a result, in the reflective mask blank of Patent Document 2, it is described that the crystalline state of the absorber layer film becomes amorphous, and the stress and surface roughness are also reduced.

[0006] Patent Document 3 describes a reflective mask blank for EUV lithography in which a multilayer reflective film that reflects EUV light and a pattern film that is partially etched during mask processing are formed in this order on a substrate. Specifically, Patent Document 3 states that the pattern film is composed of an absorber film that absorbs EUV light and a surface reflection enhancement film formed on the absorber film. When the refractive index of the absorber film at a wavelength of 13.53 nm is n ABS , the absorption coefficient is k ABS , and the refractive index of the surface reflection enhancement film is n and the absorption coefficient is k, ((n - 1) 2 +k 2 ) 1 / 2> ((n ABS -1) 2 +k ABS 2 ) 1 / 2 A reflective mask blank is described which is characterized by satisfying the condition represented by +0.03. According to the reflective mask blank of Patent Document 3, the surface reflection enhancement film formed on the absorber film increases the amplitude of the EUV light reflected from the surface of the pattern film, and the interference effect with the EUV light reflected by the multilayer reflection film becomes large. By utilizing this interference effect, it is described that a pattern film thickness with a reflectance of 2% or less can be made thinner than before.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The reflective mask blank of Patent Document 3 has a surface reflection enhancement film on the uppermost layer of the absorber film (pattern film). As the constituent material of the surface reflection enhancement film, it is described that Ag, Pt, Pd, Au, Ru, and Ni are used. Thus, when the uppermost layer of the absorber film is a thin metal film, it has been found that the film quality of the metal film is likely to change over time depending on the film formation conditions. In particular, from the viewpoint of the oxidation-reduction potential, even a metal film that was considered to be relatively stable was found to have a film quality that is likely to change over time when the film thickness is thin. When the film quality of the metal film changes over time, especially when the film thickness is thin, a problem occurs in that the deviation from the design value of optical characteristics such as reflectance becomes large.

[0009] In addition, when an etching mask film is laminated on the uppermost layer of the absorber film, depending on the combination of materials of the uppermost layer and the etching mask film, a diffusion layer may be formed at the interface, resulting in the same problem as above that the deviation from the designed value of the optical characteristics becomes large.

[0010] Therefore, an object of the present invention is to provide a reflective mask blank, a reflective mask, a substrate with a conductive film, and a method for manufacturing a semiconductor device that can suppress the change in the film quality of a thin metal film over time.

Means for Solving the Problems

[0011] To solve the above problems, the present invention has the following configuration. (Configuration 1) A reflective mask blank including a substrate, a multilayer reflective film on the substrate, and a laminated film on the multilayer reflective film, The laminated film includes an uppermost layer and other lower layers, The film thickness of the uppermost layer is 0.5 nm or more and less than 5 nm, The uppermost layer contains at least one metal element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb), and at least one additive element selected from hydrogen (H) and deuterium (D), A reflective mask blank, wherein the total content of the metal elements in the uppermost layer is 95 atomic% or more.

[0012] (Configuration 2) The reflective mask blank according to Configuration 1, wherein the metal element contained in the uppermost layer is at least one selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), and gold (Au).

[0013] (Configuration 3) The uppermost layer has a structure of at least one of an amorphous structure and a microcrystalline structure, and the reflective mask blank according to Configuration 1 or 2 is characterized thereby.

[0014] (Configuration 4) The laminated film is composed of an absorber film including a first layer and a second layer from the substrate side. The second layer contains at least one metal element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb). The uppermost layer is a layer that forms the surface layer of the second layer, and the reflective mask blank according to any one of Configurations 1 to 3 is characterized thereby.

[0015] (Configuration 5) An etching mask film is provided in contact with the uppermost layer. The etching mask film is made of a material containing silicon (Si). The metal element of the uppermost layer is ruthenium (Ru), and the reflective mask blank according to any one of Configurations 1 to 4 is characterized thereby.

[0016] (Configuration 6) An etching mask film is provided in contact with the uppermost layer. The etching mask film is made of a material containing chromium (Cr). The metal element of the uppermost layer is at least one selected from platinum (Pt), ruthenium (Ru), and palladium (Pd), and the reflective mask blank according to any one of Configurations 1 to 4 is characterized thereby.

[0017] (Configuration 7) The first layer is made of a material containing at least one selected from tantalum (Ta) and chromium (Cr), and the reflective mask blank according to any one of Configurations 4 to 6 is characterized thereby.

[0018] (Configuration 8) A reflective mask, characterized in that the absorber film in the reflective mask blank according to any one of Configurations 4 to 7 has an absorber pattern formed thereon.

[0019] (Configuration 9) A method for manufacturing a semiconductor device, comprising the step of setting the reflective mask according to Configuration 8 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 substrate to be transferred.

[0020] (Configuration 10) A substrate with a conductive film, comprising a substrate and a backside conductive film on the substrate, The backside conductive film includes a top layer and other lower layers, The film thickness of the top layer is 0.5 nm or more and less than 5 nm, The top layer includes at least one metal element selected from platinum (Pt), gold (Au), aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), tungsten (W), indium (In), molybdenum (Mo), rhodium (Rh), and zinc (Zn), and at least one additive element selected from hydrogen (H) and deuterium (D), A substrate with a conductive film, characterized in that the total content of the metal elements in the top layer is 95 atomic% or more.

[0021] (Configuration 11) The substrate with a conductive film according to Configuration 10, characterized in that the metal element contained in the top layer is at least one selected from platinum (Pt), gold (Au), copper (Cu), silver (Ag), and rhodium (Rh).

[0022] (Configuration 12) A reflective mask blank, characterized in that it has a multilayer reflective film and an absorber film on the main surface facing the main surface on which the backside conductive film in the substrate with a conductive film according to Configuration 10 or 11 is formed.

[0023] (Configuration 13) A reflective mask, characterized in that the absorber film in the reflective mask blank according to Configuration 12 has an absorber pattern formed by patterning.

[0024] (Configuration 14) A method for manufacturing a semiconductor device, comprising the step of setting the reflective mask according to Configuration 13 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 substrate to be transferred.

Advantages of the Invention

[0025] According to the present invention, it is possible to provide a reflective mask blank, a reflective mask, a substrate with a conductive film, and a method for manufacturing a semiconductor device, which can suppress the change in the film quality of a thin metal film over time.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments do not limit the scope of the present invention in any way.

[0028] FIG. 1 is a schematic cross-sectional view of a main part of a reflective mask blank 100 according to this embodiment. As shown in FIG. 1, the reflective mask blank 100 includes a substrate 10, a multilayer reflective film 12 formed on the substrate 10, and a stacked film 16 formed on the multilayer reflective film 12. The stacked film 16 includes a lower layer 18 and an uppermost layer 20 formed so as to be in contact with the lower layer 18. A protective film 14 may be included between the multilayer reflective film 12 and the stacked film 16.

[0029] In this specification, "on" a substrate or a film includes not only the case of contacting the upper surface of the substrate or the film, but also the case of not contacting the upper surface of the substrate or the film. That is, "on" a substrate or a film includes the case where a new film is formed above the substrate or the film, the case where another film is interposed between the substrate or the film, and the like. Also, "on" does not necessarily mean the upper side in the vertical direction. "On" only indicates the relative positional relationship between a substrate, a film, etc. Further, in this specification, for example, "film A is disposed in contact with film B" means that film A and film B are directly disposed in contact with each other without another film interposed therebetween.

[0030] <Substrate> In order to prevent distortion of the transfer pattern due to heat during exposure with EUV light, the substrate 10 preferably has a low coefficient of thermal expansion within the range of 0 ± 5 ppb / °C. As a material having a low coefficient of thermal expansion within this range, for example, SiO2-TiO2-based glass, multi-component glass ceramics, etc. can be used.

[0031] The main surface of the substrate 10 on which the transfer pattern (absorber film pattern described later) is formed is preferably processed to enhance flatness. By enhancing the flatness of the main surface of the substrate 10, the positional accuracy and transfer accuracy of the pattern can be enhanced. For example, in the case of EUV exposure, in a region of 132 mm × 132 mm on the main surface of the substrate 10 on the side where the transfer pattern is formed, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Further, the main surface (back surface) on the side opposite to the side where the transfer pattern is formed is the surface fixed to the exposure apparatus by an electrostatic chuck, and in a region of 142 mm × 142 mm thereof, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Note that in this specification, the flatness represents the warpage (amount of deformation) of the surface indicated by TIR (Total Indicated Reading), and is a value determined by the least squares method with the plane defined based on the substrate surface as the focal plane, and is the absolute value of the height difference between the highest position of the substrate surface above this focal plane and the lowest position of the substrate surface below this focal plane.

[0032] In the case of EUV exposure, the surface roughness of the main surface of the substrate 10 on the side where the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). Note that the surface roughness can be measured with an atomic force microscope.

[0033] The substrate 10 preferably has high rigidity in order to prevent deformation due to the film stress of the film (such as the multilayer reflective film 12) formed thereon. In particular, those having a high Young's modulus of 65 GPa or more are preferable.

[0034] <multilayer reflective film> The multilayer reflective film 12 has a structure in which a plurality of layers mainly composed of elements having different refractive indices are periodically laminated. Generally, the multilayer reflective film 12 is composed of a multilayer film in which a thin film of a light element or its compound (high refractive index layer) that is a high refractive index material and a thin film of a heavy element or its compound (low refractive index layer) that is a low refractive index material are alternately laminated about 40 to 60 cycles. In order to form the multilayer reflective film 12, a plurality of cycles of a high refractive index layer and a low refractive index layer may be laminated in this order from the substrate 10 side. In this case, one (high refractive index layer / low refractive index layer) laminated structure constitutes one cycle.

[0035] Note that the uppermost layer of the multilayer reflective film 12, that is, the surface layer on the side opposite to the substrate 10 of the multilayer reflective film 12, is preferably a high refractive index layer. When laminating the high refractive index layer and the low refractive index layer in this order from the substrate 10 side, the uppermost layer becomes a low refractive index layer. However, when the low refractive index layer is the surface of the multilayer reflective film 12, the reflectivity of the surface of the multilayer reflective film decreases because the low refractive index layer is easily oxidized. Therefore, it is preferable to form a high refractive index layer on the low refractive index layer. On the other hand, when laminating the low refractive index layer and the high refractive index layer in this order from the substrate 10 side, the uppermost layer becomes a high refractive index layer. In that case, the high refractive index layer of the uppermost layer becomes the surface of the multilayer reflective film 12.

[0036] In this embodiment, the high refractive index layer may be a layer containing Si. The high refractive index layer may contain Si alone or may contain a Si compound. The Si compound may contain at least one element selected from the group consisting of Si and B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film excellent in reflectivity of EUV light can be obtained.

[0037] In this embodiment, the low refractive index layer may be a layer containing at least one element selected from the group consisting of Mo, Ru, Rh, and Pt, or a layer containing an alloy containing at least one element selected from the group consisting of Mo, Ru, Rh, and Pt.

[0038] For example, as the multilayer reflective film 12 for EUV light with a wavelength of 13 to 14 nm, preferably, a Mo / Si multilayer film formed by alternately laminating Mo films and Si films about 40 to 60 cycles can be used. In addition, as the multilayer reflective film used in the EUV light region, for example, a Ru / Si periodic multilayer film, a Mo / Be periodic multilayer film, a Mo compound / Si compound periodic multilayer film, a Si / Nb periodic multilayer film, a Si / Mo / Ru periodic multilayer film, a Si / Mo / Ru / Mo periodic multilayer film, a Si / Ru / Mo / Ru periodic multilayer film, etc. can be used. Considering the exposure wavelength, the material of the multilayer reflective film can be selected.

[0039] The reflectivity of such a multilayer reflective film 12 alone is, for example, 65% or more. The upper limit of the reflectivity of the multilayer reflective film 12 is, for example, 73%. Note that the thickness and period of the layers included in the multilayer reflective film 12 can be selected to satisfy Bragg's law.

[0040] The multilayer reflective film 12 can be formed by a known method. The multilayer reflective film 12 can be formed, for example, by an ion beam sputtering method.

[0041] For example, when the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film with a thickness of about 3 nm is formed on the substrate 10 using a Mo target by an ion beam sputtering method. Next, a Si film with a thickness of about 4 nm is formed using a Si target. By repeating such operations, a multilayer reflective film 12 in which Mo / Si films are laminated 40 to 60 cycles can be formed. At this time, the surface layer on the side opposite to the substrate 10 of the multilayer reflective film 12 is a layer containing Si (Si film). The thickness of one cycle of the Mo / Si film is 7 nm.

[0042] <Protective film> In order to protect the multilayer reflective film 12 from dry etching and cleaning in the manufacturing process of the reflective mask 200 described below, a protective film 14 can be formed on the multilayer reflective film 12 or in contact with the surface of the multilayer reflective film 12. Further, the protective film 14 also has a function of protecting the multilayer reflective film 12 during black defect correction of a transfer pattern using an electron beam (EB). Here, in FIG. 1, the case where the protective film 14 is a single layer is shown, but the protective film 14 may have a laminated structure of two or more layers. The protective film 14 is preferably formed of a material having resistance to an etchant or a cleaning liquid used when patterning the lower layer 18. By forming the protective film 14 on the multilayer reflective film 12, damage to the surface of the multilayer reflective film 12 during the manufacture of the reflective mask 200 can be suppressed. As a result, the reflectance characteristics of the multilayer reflective film 12 with respect to EUV light become good.

[0043] In the reflective mask blank 100 of the present embodiment, as the material of the protective film 14, a material having resistance to an etching gas used for dry etching for patterning the lower layer 18 formed on the protective film 14 can be used. When the lower layer 18 is formed of a plurality of layers, as the material of the protective film 14 in contact with the lower layer 18 (when the protective film 14 includes a plurality of layers, the uppermost layer of the protective film 14), among the layers forming the lower layer 18, the lowermost layer of the lower layer 18 (the layer in contact with the protective film 14) A material having resistance to the etching gas used for dry etching for patterning can be used. The material of the protective film 14 is preferably a material having an etching selectivity ratio of the lowermost layer of the lower layer 18 with respect to the protective film 14 (etching rate of the lowermost layer of the lower layer 18 / etching rate of the protective film 14) of 1.5 or more, preferably 3 or more.

[0044] For example, when the lowermost layer of the lower layer 18 in contact with the surface of the protective film 14 is a thin film made of a material containing tantalum (Ta), the lowermost layer of the lower layer 18 can be etched by dry etching using a halogen-based gas not containing oxygen gas. As the material of the protective film 14 having resistance to this etching gas, a material containing ruthenium (Ru) as a main component can be used.

[0045] Further, when the lowermost layer of the lower layer 18 in contact with the surface of the protective film 14 is a thin film made of a material containing chromium (Cr), the lowermost layer of the lower layer 18 can be etched by dry etching using a mixed gas of oxygen gas and a chlorine-based gas. As a material of the protective film 14 having resistance to this etching gas, a material mainly composed of ruthenium (Ru) and added with an element (such as Zr, Y, Rh) having etching resistance to oxygen gas can be used.

[0046] When the lowermost layer of the lower layer 18 is a material containing at least one selected from tantalum (Ta) and chromium (Cr), the material of the protective film 14 that can be used is, as described above, a material mainly containing ruthenium. Examples of the material mainly containing ruthenium specifically include Ru metal alone, Ru alloy containing at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), rhenium (Re), and rhodium (Rh), and materials containing nitrogen in these metals or alloys.

[0047] Further, when the lowermost layer of the lower layer 18 is formed of a material containing at least one selected from tantalum (Ta) and chromium (Cr), the lowermost layer and the uppermost layer of the protective film 14 can be formed of the above-described material mainly containing ruthenium. The layer between the lowermost layer and the uppermost layer can be formed of a metal other than Ru or an alloy containing the same.

[0048] The Ru content ratio of the Ru alloy is 50 atomic % or more and less than 100 atomic %, preferably 80 atomic % or more and less than 100 atomic %, more preferably 95 atomic % or more and less than 100 atomic %. In particular, when the Ru content ratio of the Ru alloy is 95 atomic % or more and less than 100 atomic %, diffusion of the element (silicon) constituting the multilayer reflective film 12 into the protective film 14 can be suppressed. Also, the cleaning resistance of the mask can be improved while ensuring sufficient reflectance of EUV light. Furthermore, the protective film 14 can function as an etching stopper when etching the lower layer 18. Also, the protective film 14 can prevent the change over time of the multilayer reflective film 12.

[0049] The thickness of the protective film 14 is not particularly limited as long as the protective film 14 can function to protect the multilayer reflective film 12. From the viewpoint of the reflectance of EUV light, the thickness of the protective film 14 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0050] As a method for forming the protective film 14, known methods can be used. Examples of the method for forming the protective film 14 include a sputtering method and an ion beam sputtering method.

[0051] The reflective mask blank 100 may further have a back surface conductive film 22 on the main surface on the side opposite to the side where the multilayer reflective film 12 of the substrate 10 is formed. The back surface conductive film 22 is used when adsorbing the reflective mask blank 100 by an electrostatic chuck.

[0052] The reflective mask blank 100 may include an underlayer formed between the substrate 10 and the multilayer reflective film 12. The underlayer is formed, for example, for the purpose of improving the smoothness of the surface of the substrate 10. The underlayer is formed, for example, for purposes such as defect reduction, improvement of the reflectance of the multilayer reflective film, and stress correction of the multilayer reflective film.

[0053] <Stacked film> The reflective mask blank 100 of this embodiment has a stacked film 16 formed on a multilayer reflective film 12 (or a multilayer reflective film 12 with a protective film 14). The stacked film 16 includes an uppermost layer 20 and a lower layer 18 which is the other layer. The lower layer 18 is formed so as to contact the multilayer reflective film 12 (or the multilayer reflective film 12 with the protective film 14). The uppermost layer 20 is formed so as to contact the lower layer 18.

[0054] In the reflective mask blank 100 of this embodiment, the stacked film 16 is composed of an absorber film 17 for absorbing EUV light. In this case, the absorber film 17 includes an absorption layer as the lower layer 18 and the uppermost layer 20. The absorption layer (lower layer 18) is a layer for absorbing EUV light. The uppermost layer 20 is a layer for increasing the amplitude of EUV light reflected from the surface of the absorber film 17. By increasing the amplitude of EUV light reflected from the surface of the absorber film 17, the interference effect with the EUV light reflected by the multilayer reflective film 12 becomes larger. By utilizing this interference effect, the film thickness of the absorber film 17 that can make the reflectivity be equal to or less than a predetermined value (for example, 2.5% or less) can be made thinner than before.

[0055] When the lower layer 18 is an absorption layer, as the material of the lower layer 18, for example, a material containing at least one selected from tantalum (Ta) and chromium (Cr) can be used.

[0056] Examples of materials containing tantalum (Ta) include materials in which tantalum (Ta) contains at least one element selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H). Among these, materials in which tantalum (Ta) contains nitrogen (N) are preferable. Specific examples of such materials include tantalum nitride (TaN), tantalum oxynitride (TaON), tantalum boron nitride (TaBN), and tantalum boron oxynitride (TaBON).

[0057] Examples of materials containing chromium (Cr) include materials in which chromium (Cr) contains at least one element selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H). Among these, materials in which chromium (Cr) contains nitrogen (N) and / or carbon (C) are preferred. Specific examples of such materials include chromium nitride (CrN), chromium oxynitride (CrON), chromium carbide (CrC), chromium oxycarbide (CrOC), chromium carbonitride (CrCN), and chromium oxycarbonitride (CrOCN).

[0058] The lower layer 18 (absorbing layer) made of the above material can be formed by a magnetron sputtering method such as a DC sputtering method and an RF sputtering method. For example, the lower layer 18 (absorbing layer) can be formed by a reactive sputtering method using a target containing tantalum and boron and a noble gas such as argon (Ar) gas, krypton (Kr) gas, and / or xenon (Xe) gas to which nitrogen gas is added.

[0059] Further, the material of the lower layer 18 is not particularly limited as long as it has a function of absorbing EUV light, has an etching selectivity with respect to the uppermost layer 20, and has an etching selectivity with respect to the protective film 14. As such a material, 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), and rhodium (Rh), or a compound thereof can be preferably used.

[0060] In the reflective mask blank 100 of the present embodiment, the film thickness of the uppermost layer 20 is 0.5 nm or more and less than 5 nm, preferably 0.5 nm or more and 4 nm or less.

[0061] In the reflective mask blank 100 of the present embodiment, the uppermost layer 20 contains a metal element and at least one additive element selected from hydrogen (H) and deuterium (D).

[0062] The metal element contained in the uppermost layer 20 is at least one selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb).

[0063] The total content of the metal element in the uppermost layer 20 is 95 atomic% or more, preferably 97 atomic% or more, and less than 100 atomic%. When there is one metal element contained in the uppermost layer 20, the above total content is the content of the metal alone. When there are a plurality of metal elements contained in the uppermost layer 20, the above total content is the total content of the plurality of metal elements.

[0064] The total content of the above additive element in the uppermost layer 20 is 0.1 atomic% or more, preferably 0.3 atomic% or more. The total content of the additive element is 5 atomic% or less, and more preferably 3 atomic% or less.

[0065] When the refractive index of the lower layer 18 (absorbing layer) is n1 and the refractive index of the uppermost layer 20 is n2, the lower layer 18 (absorbing layer) and the uppermost layer 20 are preferably made of materials that satisfy the relationship n1 > n2. By satisfying the relationship n1 > n2, the amplitude of the EUV light reflected from the surface of the absorber film 17 can be increased. As a result, the film thickness of the absorber film 17 such that the reflectance becomes, for example, 2.5% or less can be made thinner than before. The film thickness of the absorber film 17 is preferably 55 nm or less, and more preferably 45 nm or less.

[0066] The lower layer 18 and the topmost layer 20 are made of a TaBN film and a Ru film, a TaBN film and a Pt film, or a CrN film and a Pt film, respectively. Fig. 7 shows the simulation results of the EUV light reflectivity with respect to the film thickness of the absorber film 17 when the film thickness of the topmost layer 20 is fixed at 3 nm. For reference, the simulation results when the absorber film 17 is a single TaBN film are also shown. As can be seen from Fig. 7, when the topmost layer 20 is provided on the lower layer 18, it is possible to reduce the film thickness of the absorber film 17 as compared with the case where the topmost layer 20 is not provided.

[0067] The refractive index n1 of the lower layer 18 (absorbing layer) is preferably 0.92 or more and 1.0 or less. The refractive index n2 of the topmost layer 20 is preferably 0.87 or more and 0.95 or less.

[0068] As described above, the topmost layer 20 has a film thickness of 0.5 nm or more and less than 5 nm and is a thin metal film. Thus, when the topmost layer 20 of the absorber film 17 is a thin metal film, it has been found that, depending on the film formation conditions, the film quality of the metal film is likely to change with time. When the film quality of the metal film changes with time, particularly when the film thickness is thin, a problem occurs in that the deviation from the designed values of optical characteristics such as reflectivity increases.

[0069] To solve such a problem, in the reflective mask blank 100 of the present embodiment, the topmost layer 20 contains at least one additive element selected from hydrogen (H) and deuterium (D). By including the above additive element in the topmost layer 20, it becomes possible to suppress the change in the film quality of the topmost layer 20 with time. Although the reason for obtaining such an effect is not clear, it is considered that the thin metal film constituting the topmost layer 20 has a microcrystalline structure or an amorphous structure due to the above additive element, and the intrusion of oxygen or the like into the grain boundaries is suppressed. Since it is possible to reduce the crystallinity with the same addition amount of hydrogen (H), the above additive element contained in the topmost layer 20 is more preferably deuterium (D).

[0070] Moreover, the content (atomic %) of the additive element contained in the top layer 20 is preferably higher than the content (atomic %) of the additive element contained in the lower layer 18 (absorbing layer). By having the content of the additive element contained in the top layer 20 higher than that of the lower layer 18, it becomes possible to more effectively suppress the film quality of the top layer 20 from changing over time.

[0071] The metal element contained in the top layer 20 is preferably at least one selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru) and gold (Au). These metal elements have an oxidation-reduction potential (standard electrode potential) of +0.4 V or more and have been considered to be relatively stable. In addition, the metal element contained in the top layer 20 is more preferably at least one selected from palladium (Pd), platinum (Pt) and gold (Au). These metal elements have an oxidation-reduction potential (standard electrode potential) of +0.9 V or more and have been considered to be more stable. However, it has become clear that even in metal films containing these metal elements, when the film thickness of the metal film is thin (film thickness is 0.5 nm or more and 5 nm), the film quality of the metal film is likely to change over time. In other words, it has become clear that even in films made of these metals that have been considered to be relatively stable, when the film thickness of the metal film is thin, there is a high need to suppress the film quality of the metal film from changing over time. For this reason, when the uppermost layer 20 contains these metal elements, the effect of suppressing changes in film quality caused by the above-mentioned added elements is more pronounced.

[0072] The top layer 20 can be formed by magnetron sputtering such as DC sputtering and RF sputtering. The above-mentioned additive elements can be added to the top layer 20 by reactive sputtering using a metal target made of the metal element contained in the top layer 20, and a rare gas (Ar gas, Kr gas, and / or Xe gas) and hydrogen gas and / or deuterium gas.

[0073] In the reflective mask blank 100 of the present embodiment, a resist film 26 may be formed on the stacked film 16 (absorber film 17). This aspect is shown in FIG. 1. After a pattern is drawn and exposed on the resist film 26 by an electron beam lithography apparatus and then through a development process, a resist pattern can be formed. By performing dry etching on the stacked film 16 (absorber film 17) using this resist pattern as a mask, a pattern (absorber pattern) can be formed on the stacked film 16. As the material of the resist film 26, for example, a chemically-amplified resist (CAR) can be used.

[0074] As a reflective mask blank 100 of another embodiment, the stacked film 16 is composed of an absorber film 17 for absorbing EUV light. In this case, as shown in FIG. 2, the absorber film 17 includes a first layer 62 and a second layer 64 from the substrate 10 side. The uppermost layer 20 is a layer that forms the surface layer of the second layer 64 on the opposite side of the first layer 62, and the film thickness is 0.5 nm or more and less than 5 nm. The first layer 62 is a layer for absorbing EUV light. The second layer 64 including the uppermost layer 20 is a layer for absorbing EUV light and increasing the amplitude of the EUV light reflected on the surface of the absorber film 17. By increasing the amplitude of the EUV light reflected on the surface of the absorber film 17, the interference effect with the EUV light reflected by the multilayer reflective film 12 becomes larger. By utilizing this interference effect, the film thickness of the absorber film 17 such that the reflectance becomes equal to or less than a predetermined value (for example, 2.5% or less) can be made thinner in the same manner as in the above-described embodiment.

[0075] As the material of the first layer 62, the same material as the material of the above-described absorption layer (lower layer 18) can be used.

[0076] As the materials for the second layer 64 and the topmost layer 20, at least one metal selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb), or a compound containing at least one selected from nitrogen (N), oxygen (O), carbon (C), and boron (B) in these metals can be used.

[0077] The total content of the metal elements contained in the second layer 64 and the topmost layer 20 is 95 atomic% or more, preferably 97 atomic% or more, and less than 100 atomic%. When there is one metal element contained in the second layer 64 and the topmost layer 20, the above total content is the content of the single metal. When there are a plurality of metal elements contained in the second layer 64, the above total content is the total content of the plurality of metal elements.

[0078] The additive elements and film thickness of the topmost layer 20 are the same as those in the above-described embodiment. The second layer 64 may contain at least one additive element selected from hydrogen (H) and deuterium (D) throughout the film thickness direction. Also, the content of the additive element in the second layer 64 may decrease in the direction from the topmost layer 20 to the first layer 62.

[0079] The film thickness of the first layer 62 is preferably 20 nm or more, more preferably 25 nm or more, and preferably 60 nm or less, more preferably 55 nm or less. The film thickness of the second layer 64 is preferably 1 nm or more, more preferably 1.5 nm or more, preferably 25 nm or less, more preferably 20 nm or less.

[0080] When the refractive index of the first layer 62 is n1 and the refractive index of the second layer 64 is n2, the first layer 62 and the second layer 64 are preferably made of materials satisfying the relationship n1 > n2. By satisfying the relationship n1 > n2, the amplitude of the EUV light reflected from the surface of the absorber film 17 can be increased. As a result, the film thickness of the absorber film 17 such that the reflectance becomes, for example, 2.5% or less can be made thinner in the same manner as in the above-described embodiment.

[0081] The refractive index n1 of the first layer 62 is preferably 0.92 or more and 1.0 or less. The refractive index n2 of the second layer 64 is preferably 0.87 or more and 0.95 or less.

[0082] As another reflective mask blank 100 of an embodiment, a phase shift film having a phase shift function may be provided on the absorber film. In a portion where the phase shift film (phase shift pattern) is formed, while absorbing EUV light and reducing the light intensity, a part of the light is reflected at a level that does not adversely affect pattern transfer. On the other hand, in the opening (the portion where the phase shift film is not present), EUV light is reflected from the multilayer reflective film 12 through the protective film 14. The reflected light from the portion where the phase shift film is formed forms a desired phase difference with the reflected light from the opening. The phase shift film is formed such that the phase difference between the reflected light from the phase shift film and the reflected light from the multilayer reflective film 12 is 160° to 200°. The light with inverted phase differences near 180° interfere with each other at the pattern edge portion, thereby improving the image contrast of the projection optical image. Along with the improvement of the image contrast, the resolution increases, and various margins related to exposure such as exposure amount margin and focus margin expand. Although it depends on the pattern and exposure conditions, generally, the standard of the reflectivity of the phase shift film for obtaining this phase shift effect is 2% or more in relative reflectivity. In order to obtain a sufficient phase shift effect, the reflectivity of the phase shift film is preferably 6% or more in relative reflectivity. Here, the relative reflectivity of the phase shift film (phase shift pattern) is the reflectivity of the EUV light reflected from the phase shift pattern when the EUV light reflected from the multilayer reflective film 12 (including the multilayer reflective film 12 with the protective film 14) in the portion without the phase shift pattern is set to 100% reflectivity. In this specification, the relative reflectivity may be simply referred to as "reflectivity".

[0083] In order to further improve the resolution and improve the throughput in manufacturing a semiconductor device, the relative reflectivity of the phase shift pattern is required to be 6% to 35%, more preferably 15% to 35%.

[0084] As the material of the first layer 62, the same material as that of the above-described absorption layer (lower layer 18) can be used.

[0085] As the materials of the second layer 64 and the uppermost layer 20, a Ru-based compound containing ruthenium (Ru) and at least one metal selected from chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re), or at least one selected from nitrogen (N), oxygen (O), and carbon (C) and these metals can be used.

[0086] Also, as the materials of the second layer 64 and the uppermost layer 20, a Ru-based compound containing ruthenium (Ru) and at least one selected from nitrogen (N), oxygen (O), and carbon (C) can be used.

[0087] The total content of the metal elements contained in the second layer 64 and the uppermost layer 20 is the same as above. Also, the additive elements and film thickness of the uppermost layer 20 are the same as above.

[0088] When the refractive index of the first layer 62 is n3 and the refractive index of the second layer 64 is n4, it is preferable that the first layer 62 and the second layer 64 are made of materials satisfying the relationship n3 > n4. Also, when the attenuation coefficient of the first layer 62 is k3 and the attenuation coefficient of the second layer 64 is k4, it is preferable that the first layer 62 and the second layer 64 are made of materials satisfying the relationship k3 > k4. The refractive index n3 of the first layer 62 is preferably 0.93 to 0.96, and the attenuation coefficient k3 is preferably 0.02 to 0.04. The refractive index n4 of the second layer 64 is preferably 0.86 to 0.95, and the attenuation coefficient k4 is preferably 0.008 to 0.035.

[0089] By including the above additive elements in the uppermost layer 20 in the second layer 64, it becomes possible to suppress the change in the film quality of the uppermost layer 20 over time. Thereby, it is possible to suppress the deviation from the design values of the optical characteristics such as the reflectance and phase difference of the absorber film or the phase shift film.

[0090] <Etching mask film> The laminated film 16 can further include an etching mask film formed on the absorber film 17 (phase shift film). A resist film may be further formed on the etching mask film. In this case, the uppermost layer 20 is an etching mask film or a layer forming the surface layer of the etching mask film. When the laminated film 16 includes an etching mask film, the uppermost layer 20 can be a metal film with a film thickness of less than 0.5 to 5 nm so that the contrast is improved in an inspection using, for example, a defect inspection device. In this case, the uppermost layer 20 of the laminated film 16 can include the above-described metal element and at least one additive element selected from hydrogen (H) and deuterium (D), similar to the uppermost layer 20 of the absorber film 17 described above. By forming the uppermost layer 20 of the laminated film 16 as a thin metal film containing the above additive element, the uppermost layer 20 will have a microcrystalline structure or an amorphous structure. Thereby, when the surface of the etching mask film is inspected by a defect inspection device, it becomes possible to detect defects on the surface of the etching mask film with higher accuracy.

[0091] FIG. 3 shows a reflective mask blank 100 according to another embodiment. As shown in FIG. 3, an etching mask film 24 may be formed in contact with the uppermost layer 20 of the laminated film 16 (absorber film 17). A resist film 26 may be further formed on the etching mask film 24.

[0092] When etching the absorber film 17 (especially the topmost layer 20) with a fluorine-based gas, a material containing chromium (Cr) can be used as the material of the etching mask film 24. By forming the etching mask film 24 with a material containing chromium (Cr), the etching selectivity of the topmost layer 20 with respect to the etching mask film 24 can be increased. Examples of the material containing chromium include materials containing chromium (Cr) and at least one selected from nitrogen (N), oxygen (O), carbon (C), and boron (B). Examples of such materials include CrN, CrC, CrO, CrON, CrOC, CrCN, CrCON, CrBN, CrBC, CrBO, CrBC, CrBON, CrBCN, and CrBOCN. When the etching mask film 24 is formed of a material containing chromium, the content of chromium (Cr) is preferably 50 atomic% or more and less than 100 atomic%, and more preferably 80 atomic% or more and less than 100 atomic%.

[0093] When etching the absorber film 17 (especially the topmost layer 20) with a chlorine-based gas containing oxygen, a material containing silicon (Si) can be used as the material of the etching mask film 24. By forming the etching mask film 24 with a material containing silicon (Si), the etching selectivity of the topmost layer 20 with respect to the etching mask film 24 can be increased. Examples of the material containing silicon (Si) include materials containing silicon (Si) and at least one selected from nitrogen (N), oxygen (O), carbon (C), and hydrogen (H). Further, examples of the material containing silicon (Si) include metal silicon (metal silicide) containing silicon (Si) and a metal, or a metal silicon compound (metal silicide compound). Examples of the metal silicon compound include materials containing a metal and Si and at least one selected from N, O, C, and H.

[0094] When the etching mask film 24 is formed, the thickness of the resist film 26 can be reduced, so that a fine pattern can be formed by the absorber film 17 (especially the topmost layer 20). The thickness of the etching mask film 24 is preferably 3 nm or more. When the thickness of the etching mask film 24 is 3 nm or more, a fine pattern can be accurately formed on the topmost layer 20. Also, from the viewpoint of reducing the thickness of the resist film 26, the thickness of the etching mask film 24 is preferably 15 nm or less, and more preferably 10 nm or less.

[0095] When the etching mask film 24 is formed, a diffusion layer may be formed at the interface between the etching mask film 24 and the topmost layer 20. This diffusion layer is a layer formed by the diffusion of elements contained in one layer into the other layer. When such a diffusion layer is formed, when the etching mask film 24 is removed to form an absorber pattern, there arises a problem that the deviation of the optical characteristics (reflectivity, etc.) of the absorber pattern from the design value becomes large. Therefore, it is preferable to suppress the formation of the diffusion layer as much as possible.

[0096] According to the reflective mask blank 100 of the present embodiment, the topmost layer 20 contains a metal element and at least one additive element selected from hydrogen (H) and deuterium (D). Thereby, the thin metal film constituting the topmost layer 20 has a microcrystalline structure or an amorphous structure due to the above additive element, and it becomes possible to prevent the elements contained in the topmost layer 20 from diffusing into the etching mask film 24. Alternatively, it becomes possible to prevent the elements contained in the etching mask film 24 from diffusing into the topmost layer 20. As a result, it becomes possible to prevent the formation of a diffusion layer at the interface between the etching mask film 24 and the topmost layer 20.

[0097] When the metal element contained in the uppermost layer 20 is ruthenium (Ru), the uppermost layer 20 can be etched with a chlorine-based gas containing oxygen. Therefore, in this case, as the material of the etching mask film 24, the material containing silicon (Si) described above can be used. In this case, the formation of a diffusion layer containing RuSi can be prevented.

[0098] When the metal element contained in the uppermost layer 20 is at least one selected from platinum (Pt), ruthenium (Ru), and palladium (Pd), the uppermost layer 20 can be etched with a fluorine-based gas. Therefore, in this case, as the material of the etching mask film 24, the material containing chromium (Cr) described above can be used. In this case, the formation of a diffusion layer containing PtCr, RuCr, or PdCr can be prevented.

[0099] As the fluorine-based gas, CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, F2, etc. can be used. As the chlorine-based gas, Cl2, SiCl4, CHCl3, CCl4, BCl3, etc. can be used. Further, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 in a predetermined ratio can be used. Further, these etching gases can contain an inert gas such as He and / or Ar as necessary.

[0100] <Backside conductive film> As described above, a backside conductive film 22 is formed on the main surface on the side opposite to the side where the multilayer reflective film 12 of the substrate 10 is formed. The backside conductive film 22 is used when adsorbing the reflective mask blank 100 by an electrostatic chuck.

[0101] The electrical property (sheet resistance) required for the backside conductive film 22 for the electrostatic chuck is usually 100 Ω / □ (Ω / Square) or less. The backside conductive film 22 can be formed, for example, by a magnetron sputtering method or an ion beam sputtering method.

[0102] The back conductive film 22 can be formed using a material having a transmittance of 20% or more with respect to light having a wavelength of, for example, 532 nm or 470 nm. Thereby, it becomes possible to correct the misalignment of the reflective mask from the back surface by a laser beam or the like.

[0103] The material of the back conductive film 22 (transparent conductive film) having a high transmittance preferably contains one or more metal elements selected from platinum (Pt), gold (Au), aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), tungsten (W), indium (In), molybdenum (Mo), rhodium (Rh), and zinc (Zn). Further, within a range satisfying the desired transmittance and electrical characteristics, a metal compound containing at least one selected from boron, nitrogen, oxygen, and carbon can be used for the metal element. Since the metal film containing these metal elements has a high electrical conductivity, when these metal films are used as the back conductive film 22, it is possible to make the back conductive film 22 thinner. From the viewpoint of transmittance, the film thickness of the metal film is preferably 50 nm or less, more preferably 20 nm or less. Further, if the film thickness is too thin, the sheet resistance tends to increase rapidly, and from the viewpoint of the stability during film formation, the film thickness of the metal film is preferably 2 nm or more.

[0104] The surface layer (uppermost layer) of 0.5 nm or more and less than 5 nm from the surface of the back conductive film 22 can contain at least one additive element selected from the above metal element and hydrogen (H) and deuterium (D). The back conductive film 22 may be a laminated film composed of a plurality of layers. FIGS. 1 to 3 illustrate the case where the back conductive film 22 is a laminated film.

[0105] When the back conductive film 22 is a laminated film, the back conductive film 22 can include an uppermost layer 30 and other lower layers 28. The lower layer 28 is a layer formed in contact with the main surface (back surface) of the substrate 10. The uppermost layer 30 is a layer formed in contact with the lower layer 28. In FIGS. 1 to 3, the uppermost layer 30 is located on the lowermost side.

[0106] The uppermost layer 30 of the back conductive film 22 may be formed of a thin metal film containing the above-mentioned additive element. That is, the uppermost layer 30 of the back conductive film 22 (laminated film) can contain one or more metal elements selected from platinum (Pt), gold (Au), aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), tungsten (W), indium (In), molybdenum (Mo), rhodium (Rh), and zinc (Zn), and at least one additive element selected from hydrogen (H) and deuterium (D). When the uppermost layer 30 (or the uppermost layer as the surface layer) of the back conductive film 22 is formed of a thin metal film containing the above-mentioned additive element, the uppermost layer 30 of the back conductive film 22 will have a microcrystalline structure or an amorphous structure. Thereby, it is possible to suppress a change in the film quality of the back conductive film 22 and a change in its conductivity or the like. As a result, the reflective mask blank 100 can be held more stably by an electrostatic chuck.

[0107] It is more preferable that the metal element contained in the uppermost layer 30 (or the uppermost layer as the surface layer) is at least one selected from platinum (Pt), gold (Au), copper (Cu), silver (Ag), and rhodium (Rh). These metal elements have a redox potential (standard electrode potential) of +0.5 V or more and were considered to be more stable. Further, it is more preferable that the metal element contained in the uppermost layer 30 is at least one selected from platinum (Pt) and gold (Au). These metal elements have a redox potential (standard electrode potential) of +1.0 V or more and were considered to be more stable. Similar to the case of the above-mentioned uppermost layer 20, when these metal elements are contained in the uppermost layer 30, the effect of suppressing a change in the film quality by the above-mentioned additive element is more significantly exhibited.

[0108] Further, the lower layer 28 of the back surface conductive film 22 can be a film having a stress adjustment function for adjusting the stress between the first main surface side of the substrate 10 on which the multilayer reflective film 12 is formed and the second main surface side of the substrate 10 on which the back surface conductive film 22 is formed. Examples of the material of the lower layer 28 in this case include Si3N4 and SiO2. Since Si3N4 has a high transmittance for a wavelength of 532 nm or 470 nm, there are fewer restrictions on the film thickness compared to other materials. For example, in the case of the lower layer 28 of Si3N4, stress adjustment can be performed in the film thickness range of 1 to 100 nm. When the material of the lower layer 28 is Si3N4 and SiO2, from the viewpoints of ensuring conductivity and transmittance, the film thickness of the uppermost layer 30 made of a metal film is preferably 2 nm or more and less than 5 nm. Also, the film thickness of the laminated film of the lower layer 28 and the uppermost layer 30 is preferably 6 nm or more and 110 nm or less, and more preferably 15 nm or more and 70 nm or less.

[0109] Also, as the material of the lower layer 28 of the back surface conductive film 22, a Ta-based oxide film or a Cr-based oxide film with a small attenuation coefficient can be used. The material of the lower layer 28 preferably has an attenuation coefficient of 1.3 or less at a wavelength of 532 nm or 470 nm. Examples of the Ta-based oxide film include TaO, TaON, TaCON, TaBO, TaBON, and TaBCON. When the lower layer 28 is a Ta-based oxide film, the oxygen (O) content is preferably 20 to 70 atomic %. Examples of the Cr-based oxide film include CrO, CrON, CrCON, CrBO, CrBON, and CrBOCN. When the lower layer 28 is a Cr-based oxide film, the oxygen (O) content is preferably 25 to 75 atomic %. Further, the material of the lower layer 28 may be an oxide film of the metal film of the uppermost layer 30, that is, PtO, AuO, AlO, CuO, NiO, CrO, AgO, TiO, WO, InO, MoO, RhO, or ZnO.

[0110] When the material of the lower layer 28 is a metal oxide film such as a Ta-based oxide film or a Cr-based oxide film, from the viewpoints of ensuring conductivity and transmittance, the film thickness of the uppermost layer 30 made of a metal film is preferably 2 nm or more and less than 5 nm. Further, the film thickness of the laminated film of the lower layer 28 including the Ta-based oxide film and the uppermost layer 30 is preferably 3 nm or more and 200 nm or less, more preferably 10 nm or more and 60 nm or less. The film thickness of the laminated film of the lower layer 28 including the Cr-based oxide film and the uppermost layer 30 is preferably 3 nm or more and 250 nm or less, preferably 10 nm or more and 100 nm or less.

[0111] In addition, the lower layer 28 can be provided with a function of improving the adhesion between the substrate 10 and the back surface conductive film 22 or suppressing the intrusion of hydrogen from the substrate 10 into the back surface conductive film 22. Further, the lower layer 28 can be provided with a function of suppressing the transmission of vacuum ultraviolet light and ultraviolet light (wavelength: 130 to 400 nm), which is called out-of-band light when EUV light is used as an exposure light source, through the substrate 10 and being reflected by the back surface conductive film 22. Examples of the material of the lower layer 28 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 film thickness of the lower layer 28 is preferably 1 nm or more, more preferably 5 nm or more, and still more preferably 10 nm or more. Note that the material and film thickness of the lower layer 28 are selected so that the transmittance of the laminated film formed by laminating the lower layer 28 and the uppermost layer 30 satisfies 20% or more.

[0112] <Substrate with conductive film> FIG. 4 is a schematic cross-sectional view of a substrate 110 with a conductive film according to the present embodiment. As shown in FIG. 4, the substrate 110 with a conductive film includes a substrate 10 and a back surface conductive film 22 formed on the substrate 10. The back surface conductive film 22 includes an uppermost layer 30 and other lower layers 28. The substrate 10, the back surface conductive film 22, the uppermost layer 30, and the lower layer 28 of the substrate 110 with a conductive film are the same as those of the substrate 10, the back surface conductive film 22, the uppermost layer 30, and the lower layer 28 of the reflective mask blank 100 described above.

[0113] <Reflective Mask and Method for Manufacturing the Same> Using the reflective mask blank 100 of the present embodiment, the reflective mask of the present embodiment can be manufactured. Hereinafter, an example of a method for manufacturing a reflective mask will be described.

[0114] FIG. 5 is a schematic diagram showing a method for manufacturing a reflective mask 200. As shown in FIG. 5, first, a reflective mask blank 100 having a substrate 10, a multilayer reflective film 12 formed on the substrate 10, a protective film 14 formed on the multilayer reflective film 12, and a laminated film 16 (lower layer 18 and uppermost layer 20) formed on the protective film 14 is prepared (FIG. 5(a)). Next, a resist film 26 is formed on the laminated film 16 (FIG. 5(b)). A pattern is drawn on the resist film 26 by an electron beam lithography apparatus, and further through a development and rinsing process, a resist pattern 26a is formed (FIG. 5(c)).

[0115] Using the resist pattern 26a as a mask, the laminated film 16 (lower layer 18 and uppermost layer 20) is dry-etched. The lower layer 18 and the uppermost layer 20 are etched in two steps using an etching gas having an etching selectivity between them. Thereby, the portion of the laminated film 16 not covered by the resist pattern 26a is etched, and a laminated film pattern 40 (absorber pattern) is formed (FIG. 5(d)).

[0116] As the etching gas for the lower layer 18 and the uppermost layer 20, a fluorine-based gas and / or a chlorine-based gas can be used according to the materials of the lower layer 18 and the uppermost layer 20. As the fluorine-based gas, CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, F2, etc. can be used. As the chlorine-based gas, Cl2, SiCl4, CHCl3, CCl4, BCl3, etc. can be used. Further, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 in a predetermined ratio can be used. These etching gases can further contain an inert gas such as He and / or Ar, if necessary. Note that, as the etching gas for dry-etching the lower layer 18, an etching gas having etching selectivity with respect to the protective film 14 may be used.

[0117] After the stacked film pattern 40 is formed, the resist pattern 26a is removed with a resist stripper. After removing the resist pattern 26a, the reflective mask 200 of the present embodiment is obtained by going through a wet cleaning process using an acidic or alkaline aqueous solution (FIG. 5(e)).

[0118] Note that, when using the reflective mask blank 100 having the etching mask film 24 formed on the uppermost layer 20, after forming a pattern (etching mask pattern) on the etching mask film 24 using the resist pattern 26a as a mask, a step of forming a pattern on the stacked film 16 using the etching mask pattern as a mask is added.

[0119] The reflective mask 200 thus obtained has a structure in which the multilayer reflective film 12, the protective film 14, and the stacked film pattern 40 (absorber pattern) are stacked on the substrate 10.

[0120] The region 44 where the multilayer reflective film 12 (including the protective film 14) is exposed has a function of reflecting EUV light. The region 46 where the multilayer reflective film 12 (including the protective film 14) is covered by the stacked film pattern 40 (absorber pattern) has a function of absorbing EUV light. According to the reflective mask 200 of the present embodiment, since the thickness of the absorber pattern can be made thinner than before so that the reflectance becomes, for example, 2.5% or less, a finer pattern can be transferred to the object to be transferred.

[0121] <Method for manufacturing a semiconductor device> By lithography using the reflective mask 200 of this embodiment, a transfer pattern can be formed on a semiconductor substrate. This transfer pattern has a shape in which the pattern of the reflective mask 200 is transferred. By forming a transfer pattern on a semiconductor substrate with the reflective mask 200, a semiconductor device can be manufactured.

[0122] A method of transferring a pattern to a resist-coated semiconductor substrate 56 by EUV light will be described with reference to FIG. 6.

[0123] FIG. 6 shows a pattern transfer apparatus 50. The pattern transfer apparatus 50 includes a laser plasma X-ray source 52, a reflective mask 200, a reduction optical system 54, and the like. An X-ray reflecting mirror is used as the reduction optical system 54.

[0124] The pattern reflected by the reflective mask 200 is reduced by the reduction optical system 54 to about 1 / 4 of its original size. For example, a wavelength band of 13 to 14 nm is used as the exposure wavelength, and the optical path is set in advance to be in a vacuum. Under such conditions, EUV light generated by the laser plasma X-ray source 52 is incident on the reflective mask 200. The light reflected by the reflective mask 200 is transferred onto the resist-coated semiconductor substrate 56 through the reduction optical system 54.

[0125] The light reflected by the reflective mask 200 is incident on the reduction optical system 54. The light incident on the reduction optical system 54 forms a transfer pattern on the resist layer on the resist-coated semiconductor substrate 56. By developing the exposed resist layer, a resist pattern can be formed on the resist-coated semiconductor substrate 56. By etching the semiconductor substrate 56 using the resist pattern as a mask, for example, a predetermined wiring pattern can be formed on the semiconductor substrate. Through such processes and other necessary processes, a semiconductor device is manufactured.

Example

[0126] The following experiment was conducted to confirm the change over time in reflectance when hydrogen (H) or deuterium (D) is not added to the uppermost layer 20 of the absorber film. Reflective mask blanks for samples 1 to 6 for the experiment were fabricated as follows. An SiO2-TiO2-based glass substrate, which is a low-thermal-expansion glass substrate with a size of 6025 (approx. 152 mm × 152 mm × 6.35 mm) and both the first main surface and the second main surface polished, was prepared. Polishing consisting of a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process was performed to obtain a flat and smooth main surface.

[0127] A multilayer reflective film was formed by periodically laminating a Mo film and a Si film on the main surface of the glass substrate.

[0128] Specifically, using a Mo target and a Si target, a Mo film and a Si film were alternately laminated on the substrate by ion beam sputtering (using Kr). The thickness of the Mo film is 2.8 nm. The thickness of the Si film is 4.2 nm. The thickness of one cycle of the Mo / Si film is 7.0 nm. Such Mo / Si films were laminated 40 times, and finally a Si film was formed with a thickness of 4.0 nm to form a multilayer reflective film.

[0129] A protective film containing a Ru compound was formed on the multilayer reflective film. Specifically, using a RuNb target (Ru: 80 atomic%, Nb: 20 atomic%), a protective film made of a RuNb film was formed on the multilayer reflective film by DC magnetron sputtering in an Ar gas atmosphere. The thickness of the protective film was 3.5 nm.

[0130] Next, an absorption layer (lower layer) or a first layer made of a TaBN film was formed on the protective film by DC magnetron sputtering. The TaBN film was formed by reactive sputtering in a mixed gas atmosphere of Xe gas and N2 gas using a TaB mixed sintered target. The composition ratio (Ta:B:N) of the TaBN film was 75:12:13 as measured by X-ray photoelectron spectroscopy (XPS). Also, the refractive index of the TaBN film at a wavelength of 13.5 nm was 0.949. The film thicknesses of the absorption layer (lower layer) or the first layer in Samples 1 to 6 are as shown in Table 1 below.

[0131] Next, an uppermost layer or a second layer including the uppermost layer made of a metal film was formed on the absorption layer (lower layer) or the first layer by DC magnetron sputtering. Using a metal target made of Pt, Ru, or Ni contained in the uppermost layer, the uppermost layer or the second layer including the uppermost layer was formed by DC magnetron sputtering in a Kr gas atmosphere. For example, in Sample 1, a Pt film was formed by sputtering using a Pt target and Kr gas. The film thickness of the uppermost layer was set to a film thickness at which the amplitude of EUV light reflected from the surface of the absorber film becomes large, as shown in FIG. 7.

[0132] The metal elements contained in the uppermost layer and the film thicknesses of the uppermost layer or the second layer are as shown in Table 1 below. It was confirmed by both X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) that the content of the metal elements in the formed film was 95 atomic % or more. Note that the content of the metal elements in the uppermost layer formed in the second layer was measured at a depth of 2 nm from the surface.

[0133] From the above, reflective mask blanks of Samples 1 to 6 in which a multilayer reflective film, a protective film, an absorption layer (lower layer) or a first layer, and an uppermost layer or a second layer including the uppermost layer were laminated on a substrate were obtained. The reflectance (first time) of Samples 1 to 6 at a wavelength of 13.5 nm was measured.

[0134] Next, Samples 1 to 6 were left in an atmosphere at a temperature of 22°C and a relative humidity of 50% for 4 days, and then the reflectance (second time) of Samples 1 to 6 at a wavelength of 13.5 nm was measured.

[0135] The variation amounts of the reflectivities of the reflective mask blanks of Samples 1 to 6 in the first and second times were calculated by the following formula. The results are shown in Table 1. Variation amount = Reflectivity in the second time - Reflectivity in the first time [%]

[0136] As can be seen from the results shown in Table 1, the reflective mask blanks of Samples 1 to 6 had a variation amount of reflectivity exceeding 0.2%. It is considered that the film quality of the entire top layer made of the metal film changed over time, resulting in a large variation amount of reflectivity. In addition, when the crystal structures of Samples 1 to 6 were measured by an X-ray diffractometer (XRD) and electron diffraction method (ED), they had crystallinity.

[0137] Next, in order to confirm the change over time of the reflectivity when hydrogen (H) or deuterium (D) was added to the top layer 20, reflective mask blanks of Samples 7 to 13 were fabricated and the following experiment was conducted.

[0138] Substrates similar to Sample 1 were prepared, and in the same manner as Sample 1, a multilayer reflective film, a protective film, an absorption layer (lower layer), or a first layer was formed on the substrates. The film thicknesses of the absorption layer (lower layer) or the first layer in Samples 7 to 13 are as shown in Table 2 below.

[0139] Next, on the absorption layer (lower layer) or the first layer, a top layer made of a metal film or a second layer including the top layer was formed by DC magnetron sputtering. Using a metal target made of Pt, Ru, or Ni contained in the top layer, the top layer was formed by a reactive sputtering method using Kr gas and hydrogen gas or deuterium gas. For example, in the preparation of Sample 7, a Pt film with H added was formed by reactive sputtering using a Pt target, Kr gas, and hydrogen gas.

[0140] The metal element contained in the uppermost layer, its content, the flow rate ratio of the film-forming gas, and the film thickness of the uppermost layer or the second layer including the uppermost layer are as shown in Table 2 below. The content of the metal element in the formed film was measured by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometer (SIMS). Also, it was confirmed that H or D was contained by dynamic secondary ion mass spectrometry (SIMS) at a depth of 2 nm from the surface of the uppermost layer or the second layer.

[0141] From the above, reflective mask blanks of Samples 7 to 13 were obtained in which a multilayer reflective film, a protective film, an absorption layer (lower layer) or a first layer, and an uppermost layer or a second layer including the uppermost layer were laminated on a substrate. The reflectivities of the obtained Samples 7 to 13 were measured in the same manner as Sample 1, and the amount of variation in reflectivity was calculated.

[0142] As can be seen from the results shown in Table 2, in the reflective mask blanks of Samples 7 to 13, the change in the film quality of the uppermost layer made of a metal film was suppressed, and the amount of variation in reflectivity was within 0.2%. In addition, when the crystal structures of Samples 7 to 13 were measured by an X-ray diffractometer (XRD) and electron diffraction method (ED), they had a microcrystalline structure or an amorphous structure.

[0143] (Example 1) The reflective mask blank and reflective mask of Example 1 will be described. The reflective mask blank of Example 1 was produced in the same manner as the production conditions of Sample 8 above. An etching mask film made of a CrN film was formed on the uppermost layer of the produced reflective mask blank to produce a reflective mask blank having an etching mask film.

[0144] The etching mask film was formed to a film thickness shown in Table 3 by a magnetron sputtering (reactive sputtering) method using a Cr target in a mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%).

[0145] A back conductive film made of CrN was formed on the back surface of the above glass substrate by magnetron sputtering. The back conductive film was formed to a thickness of 20 nm by magnetron sputtering (reactive sputtering) using a Cr target in a mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%).

[0146] In the above manner, the reflective mask blank of Example 1 was manufactured.

[0147] Next, using the reflective mask blank of Example 1 above, the reflective mask of Example 1 was manufactured. No diffusion layer was formed between the etching mask film and the top layer.

[0148] The reflective mask was manufactured by forming an etching mask pattern and a laminated film pattern (second layer pattern and first layer pattern) using the etching gas shown in Table 3 by the above-described method for manufacturing a reflective mask, and removing the etching mask pattern with a mixed gas of Cl2 gas and O2 gas.

[0149] Regarding the reflective mask of Example 1, the reflectance at a wavelength of 13.5 nm was measured in the same manner as in Sample 8, and the amount of variation in reflectance was calculated. As a result, it was confirmed that the variation was within 0.1% and the deviation from the design value was small.

[0150] (Example 2) The reflective mask blank and reflective mask of Example 2 will be described. The reflective mask blank of Example 2 was manufactured in the same manner as the manufacturing conditions of Sample 10 above. An etching mask film made of SiO2 film was formed on the top layer of the manufactured reflective mask blank to manufacture a reflective mask blank having an etching mask film.

[0151] The etching mask film was formed to the film thickness shown in Table 4 by RF sputtering using a SiO2 target in an Ar gas atmosphere.

[0152] A back surface conductive film was formed in the same manner as in Example 1, and a reflective mask blank of Example 2 was manufactured. A diffusion layer was not formed between the etching mask film and the uppermost layer.

[0153] Next, using the reflective mask blank of Example 2 above, a reflective mask of Example 2 was manufactured.

[0154] The reflective mask was manufactured by forming an etching mask pattern and a laminated film pattern (uppermost layer pattern and lower layer pattern) using the etching gas in Table 4 by the manufacturing method of the reflective mask described above, and removing the etching mask pattern with CF4 gas.

[0155] Regarding the reflective mask of Example 2, the reflectance at a wavelength of 13.5 nm was measured in the same manner as in Sample 10, and the amount of variation in reflectance was calculated. As a result, it was within 0.2%, and it was confirmed that the deviation from the design value was small.

[0156] (Example 3) The substrate with a conductive film of Example 3 will be described. The substrate with a conductive film of Example 3 was obtained by preparing a glass substrate similar to Sample 1 and forming a back surface conductive film on the main surface opposite to the main surface on which the multilayer reflective film of the glass substrate was formed.

[0157] Specifically, a back surface conductive film (including the uppermost layer) made of a Pt film containing H was formed by DC magnetron sputtering using a Pt target in the film-forming gas atmosphere shown in Table 5. The metal element contained in the back surface conductive film, its content, the film-forming gas flow rate ratio, and the film thickness of the back surface conductive film are as shown in Table 5 below. The content of the metal element in the formed film was measured by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS).

[0158] As described above, a substrate with a back conductive film including the topmost layer laminated thereon was obtained. After leaving the obtained substrate with the conductive film in an atmosphere of a temperature of 22°C and a relative humidity of 50% for 4 days, the sheet resistance and transmittance were measured, and as shown in Table 5, there was almost no deviation from the design values. The transmittance was measured by irradiating light with a wavelength of 470 nm from the back surface of the substrate with the conductive film. The sheet resistance was measured by the four-terminal measurement method.

[0159]

Table 1

[0160]

Table 2

[0161]

Table 3

[0162]

Table 4

[0163]

Table 5

Explanation of Symbols

[0164] 10 Substrate 12 Multilayer Reflective Film 14 Protective Film 16 Laminate Film 17 Absorber Film 18, 28 Lower Layer 20, 30 Topmost Layer 22 Back Conductive Film 24 Etching Mask Film 26 Resist Film 40 Laminate Film Pattern 62 First Layer 64 Second Layer 100 Reflective mask blank 110 Substrate with conductive film 200 Reflective mask

Claims

1. A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, and a laminated film on the multilayer reflective film, wherein the laminated film includes a top layer and other lower layers, the film thickness of the top layer is 0.5 nm or more and less than 5 nm, the top layer contains at least one metal element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb), and at least one additive element selected from hydrogen (H) and deuterium (D), A reflective mask blank, wherein the total content of the metal elements in the top layer is 95 atomic% or more.

2. The reflective mask blank according to claim 1, wherein the metal element contained in the top layer is at least one selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), and gold (Au).

3. The reflective mask blank according to claim 1 or 2, wherein the top layer has at least one of an amorphous structure and a microcrystalline structure.

4. The laminated film is composed of an absorber film including a first layer and a second layer from the substrate side, the second layer contains at least one metal element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb), The reflective mask blank according to any one of claims 1 to 3, wherein the top layer is a layer forming the surface layer of the second layer.

5. Comprising an etching mask film provided in contact with the top layer, the etching mask film is made of a material containing silicon (Si), The reflective mask blank according to any one of claims 1 to 4, wherein the metal element of the top layer is ruthenium (Ru).

6. Comprising an etching mask film provided in contact with the top layer, the etching mask film is made of a material containing chromium (Cr), The reflective mask blank according to any one of claims 1 to 4, wherein the uppermost metal element is at least one selected from platinum (Pt), ruthenium (Ru), and palladium (Pd).

7. The reflective mask blank according to any one of claims 4 to 6, wherein the first layer is made of a material containing at least one selected from tantalum (Ta) and chromium (Cr).

8. A reflective mask, characterized in that the absorber pattern in the reflective mask blank according to any one of claims 4 to 7 has a patterned absorber film.

9. A method for manufacturing a semiconductor device, comprising the step of setting the reflective mask according to claim 8 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 substrate to be transferred.

10. A substrate with a conductive film, comprising a substrate and a backside conductive film on the substrate, wherein the backside conductive film includes an uppermost layer and other lower layers, the thickness of the uppermost layer is 0.5 nm or more and less than 5 nm, the uppermost layer includes at least one metal element selected from platinum (Pt), gold (Au), aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), tungsten (W), indium (In), molybdenum (Mo), rhodium (Rh), and zinc (Zn), and at least one additive element selected from hydrogen (H) and deuterium (D), and the total content of the metal elements in the uppermost layer is 95 atomic% or more. A substrate with a conductive film characterized by this.

11. The substrate with a conductive film according to claim 10, wherein the metal element contained in the uppermost layer is at least one selected from platinum (Pt), gold (Au), copper (Cu), silver (Ag), and rhodium (Rh).

12. A reflective mask blank, characterized in that a multilayer reflective film and an absorber film are provided on the main surface facing the main surface on which the backside conductive film of the substrate with a conductive film according to claim 10 or 11 is formed.

13. A reflective mask, characterized in that the absorber pattern in the reflective mask blank according to claim 12 has a patterned absorber film.

14. A method for manufacturing a semiconductor device, comprising the step of setting the reflective mask according to claim 13 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 substrate to be transferred.

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