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

Abstract

Provided are: a multilayer reflective film-equipped substrate that is provided with a protective film having high resistance to a fluorine-based etching gas for use in a step for repairing a absorbent pattern without decreasing the reflectivity of a multilayer reflective film; a reflective mask blank; and a reflective mask.　A multilayer reflective film-equipped substrate (100) has: a substrate (10); a multilayer reflective film (12) disposed on the substrate (10); and a protective film (14) disposed on the multilayer reflective film (12). The protective film (14) contains a first metal and a second metal. The standard formation free energy of a fluoride of the first metal is higher than the standard formation free energy of RuF5. The second metal exhibits an extinction coefficient of not more than 0.03 at a wavelength of 13.5 nm.

Description

Technical Field

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

Background Art

[0002] With the further requirements for higher density and higher precision of ultra-LSI devices in recent years, extreme ultraviolet (EUV) lithography, an exposure technology using EUV light, has been regarded as promising. EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, 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 a pattern-shaped absorber film formed on the multilayer reflective film for absorbing exposure light, which is an absorber pattern. The light incident on the reflective mask mounted on an exposure machine for pattern transfer on a semiconductor substrate is absorbed in the part with the absorber pattern and reflected by the multilayer reflective film in the part without the absorber pattern. The light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflective optical system.

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

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

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

[0007] Patent Document 2 describes a substrate with a multilayer reflective film, which has a multilayer reflective film on the substrate that reflects exposure light. 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 made up of a reflectance reduction suppression layer, a blocking layer, and an etching stopper layer stacked in that order. Furthermore, Patent Document 2 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) alloy, ruthenium zirconium (RuZr) alloy, ruthenium rhodium (RuRh) alloy, ruthenium cobalt (RuCo) alloy, and ruthenium rhenium (RuRe) alloy.

[0008] Patent documents 3 and 4 describe a substrate with a multilayer reflective film, comprising a substrate, a multilayer reflective film, and a Ru-based protective film formed on the multilayer reflective film for protecting the multilayer reflective film. Patent documents 3 and 4 also describe that the surface layer of the multilayer reflective film opposite to the substrate is a Si-containing layer.

[0009] Patent Document 3 describes a method in which a blocking layer is provided between the multilayer reflective film and the Ru-based protective film to prevent the migration of Si to the Ru-based protective film. Patent Document 3 also describes that Ru and its alloy materials can be used as constituent materials for the Ru-based protective film, and that a Ru compound having Ru and at least one metallic element selected from the group consisting of Nb, Zr, Rh, Ti, Co, and Re is preferred as the Ru alloy.

[0010] Patent Document 4 describes that a Ru-based protective film contains a Ru compound comprising Ru and Ti, and that the Ru compound contains more Ru than the stoichiometric composition of RuTi. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2002-122981 [Patent Document 2] Japanese Patent Publication No. 2014-170931 [Patent Document 3] International Publication No. 2015 / 012151 [Patent Document 4] International Publication No. 2015 / 037564 [Disclosure of the Invention]

[0012] In the manufacturing process of reflective masks, when forming the absorber pattern, the absorber film is processed by etching via a resist pattern or etching mask pattern. To process the absorber film into the designed shape, a slight over-etching of the absorber film is necessary. During over-etching, the multilayer reflective film beneath the absorber film is also damaged by etching. To prevent the multilayer reflective film from being damaged by etching, a protective film is provided between the absorber film and the multilayer reflective film. Therefore, the protective film is required to have high resistance to the etching gas used to etch the absorber film.

[0013] Furthermore, after forming an absorber pattern on the absorber film by etching, a repair process is performed to correct the absorber pattern to the shape specified in the design. In the repair process, a fluorine-based etching gas (e.g., XeF2 + H2O) is supplied while an electron beam is irradiated onto the black defects in the absorber pattern. Therefore, the protective film is required to have high resistance to fluorine-based etching gases to prevent damage to the multilayer reflective film from the fluorine-based etching gases used in the repair process.

[0014] Conventionally, Ru-based materials (Ru, RuNb, etc.), which have high resistance to etching gases used in etching absorber films, have been used as protective film materials. However, Ru-based materials have the problem of not having sufficient resistance to fluorine-based etching gases used in the repair process of absorber patterns. Furthermore, protective films are required to protect multilayer reflective films from damage caused by etching gases while minimizing the reduction in the reflectivity of the multilayer reflective films.

[0015] Therefore, the present invention aims to provide a multilayer reflective film substrate, a reflective mask blank, and a reflective mask equipped with a protective film that has high resistance to fluorine-based etching gases used in the absorber pattern repair process without reducing the reflectivity of the multilayer reflective film. The present invention also aims to provide a method for manufacturing a semiconductor device using such a reflective mask equipped with a protective film.

[0016] To solve the above problems, the present invention has the following configuration.

[0017] (Composition 1) A multilayer reflective 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 comprises a first metal and a second metal, The standard free energy of formation of the fluoride of the first metal is higher than that of RuF5. The substrate with a multilayer reflective film is characterized in that the second metal has an attenuation coefficient of 0.03 or less at a wavelength of 13.5 nm.

[0018] (Configuration 2) The substrate with a multilayer reflective film according to Configuration 1, wherein the first metal is iridium (Ir).

[0019] (Configuration 3) The substrate with a multilayer reflective film according to Configuration 1, wherein the first metal is rhodium (Rh).

[0020] (Configuration 4) The substrate with a multilayer reflective film according to any one of Configurations 1 to 3, wherein the second metal is at least one selected from zirconium (Zr) and ruthenium (Ru).

[0021] (Configuration 5) A reflective mask blank, comprising an absorber film on the protective film of the substrate with a multilayer reflective film according to any one of Configurations 1 to 4.

[0022] (Configuration 6) The reflective mask blank according to Configuration 5, wherein the absorber film contains ruthenium (Ru).

[0023] (Configuration 7) The absorber film has a buffer layer and an absorption layer provided on the buffer layer, the buffer layer contains tantalum (Ta) or silicon (Si), The reflective mask blank according to Configuration 5 or 6, wherein the absorption layer contains ruthenium (Ru).

[0024] (Configuration 8) A reflective mask, comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to any one of Configurations 5 to 7.

[0025] (Configuration 9) A method for manufacturing a semiconductor device, characterized by having a step of performing a lithography process using an exposure apparatus with a reflective mask as described in configuration 8 to form a transfer pattern on a transfer object.

[0026] According to the present invention, it is possible to provide a multilayer reflective film substrate, a reflective mask blank, and a reflective mask equipped with a protective film that has high resistance to fluorine-based etching gases used in the absorber pattern repair process without reducing the reflectivity of the multilayer reflective film. Furthermore, it is possible to provide a method for manufacturing a semiconductor device using such a reflective mask equipped with a protective film. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic cross-sectional view showing an example of a substrate with a multilayer reflective film according to one embodiment. [Figure 2] This is a schematic cross-sectional view showing another example of a substrate with a multilayer reflective film according to one embodiment. [Figure 3] This is a schematic cross-sectional view showing an example of a reflective mask blank according to one embodiment. [Figure 4] This is a schematic cross-sectional view showing another example of a reflective mask blank according to one embodiment. [Figure 5] This is a schematic cross-sectional view showing another example of a reflective mask blank according to one embodiment. [Figure 6A-E] This is a schematic diagram illustrating an example of a method for manufacturing a reflective mask. [Figure 7] This is a schematic diagram showing an example of a pattern transfer device. [Modes for carrying out the invention]

[0028] The embodiments of the present invention will be described in detail below with reference to the drawings. Note that the following embodiments are intended to illustrate the present invention in detail and do not limit the present invention to their scope.

[0029] Figure 1 is a schematic cross-sectional view showing an example of a multilayer reflective substrate 100 according to one embodiment of the present invention. The multilayer reflective substrate 100 shown in Figure 1 includes a substrate 10, a multilayer reflective film 12 formed on the substrate 10, and a protective film 14 formed on the multilayer reflective film 12. A back surface conductive film 22 for electrostatic chucks may be formed on the back surface of the substrate 10 (the surface opposite to the side on which the multilayer reflective film 12 is formed).

[0030] In this specification, "on top of" a substrate or film includes not only cases where it is in contact with the upper surface of the substrate or film, but also cases where it is not in contact with the upper surface of the substrate or film. That is, "on top of" a substrate or film includes cases where a new film is formed on top of the substrate or film, or where another film is interposed between the substrate or film and the film. Furthermore, "on top" does not necessarily mean the upper side in the vertical direction. "On top" merely indicates the relative positional relationship of the substrate or film.

[0031] <Circuit board> To prevent distortion of the transfer pattern due to heat during exposure with EUV light, the substrate 10 is preferably made of a material with a low thermal expansion coefficient in the range of 0 ± 5 ppb / °C. Examples of materials with a low thermal expansion coefficient in this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0032] The main surface of the substrate 10 on the side where the transfer pattern (absorber pattern described later) is formed is preferably processed to increase its flatness. By increasing the flatness of the main surface of the substrate 10, the positional accuracy and transfer accuracy of the pattern can be improved. For example, in the case of EUV exposure, the flatness of the 132 mm × 132 mm area of ​​the main surface of the substrate 10 on the side where the transfer pattern is formed is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. The main surface (back side) on the side opposite to the side where the transfer pattern is formed is the surface that is fixed to the exposure apparatus by an electrostatic chuck, and the flatness of the 142 mm × 142 mm area of ​​this surface is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is a value representing the surface warp (amount of deformation) as shown by TIR (Total Indicated Reading). Flatness is the absolute difference in height between the highest point on the substrate surface above the focal plane (defined by the least squares method with respect to the substrate surface) and the lowest point on the substrate surface below the focal plane.

[0033] In the case of EUV exposure, the surface roughness of the main surface on the side of the substrate 10 where the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). Surface roughness can be measured using an atomic force microscope.

[0034] The substrate 10 is preferably made of a material with high rigidity in order to prevent deformation due to film stress of the film (such as the multilayer reflective film 12) formed on it. In particular, it is preferable that it has a high Young's modulus of 65 GPa or more.

[0035] <Multilayer reflective film> The multilayer reflective film 12 has a structure in which multiple layers, mainly composed of elements with different refractive indices, are periodically stacked. Generally, the multilayer reflective film 12 consists of a multilayer film in which thin films of light elements or compounds thereof, which are high refractive index materials (high refractive index layers), and thin films of heavy elements or compounds thereof, which are low refractive index materials (low refractive index layers), are alternately stacked for about 40 to 60 periods. To form the multilayer reflective film 12, high refractive index layers and low refractive index layers may be stacked in this order in multiple periods from the substrate 10 side. In this case, one (high refractive index layer / low refractive index layer) stacked structure constitutes one period.

[0036] Furthermore, it is preferable that the uppermost layer of the multilayer reflective film 12, that is, the surface layer of the multilayer reflective film 12 opposite to the substrate 10, be a high refractive index layer. When the high refractive index layer and the low refractive index layer are laminated in this order from the substrate 10 side, the uppermost layer will be the low refractive index layer. However, if the low refractive index layer is the surface of the multilayer reflective film 12, the low refractive index layer will be easily oxidized, thus affecting the multilayer reflective film. 12 Since the reflectivity of the surface decreases, it is preferable to form a high refractive index layer on top of the low refractive index layer. On the other hand, when the low refractive index layer and the high refractive index layer are stacked in this order from the substrate 10 side, the top layer becomes the high refractive index layer. In that case, the top high refractive index layer becomes the surface of the multilayer reflective film 12.

[0037] In this embodiment, the high refractive index layer may be a layer containing Si. The high refractive index layer may contain pure Si or a Si compound. The Si compound may contain Si and at least one element selected from the group consisting of B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film with excellent EUV light reflectivity can be obtained.

[0038] 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.

[0039] For example, as a multilayer reflective film 12 for EUV light with a wavelength of 13-14 nm, a Mo / Si multilayer film in which Mo films and Si films are alternately stacked for about 40-60 periods can be used. In addition, as multilayer reflective films used in the EUV light region, for example, Ru / Si periodic multilayer films, Mo / Be periodic multilayer films, Mo compound / Si compound periodic multilayer films, Si / Nb periodic multilayer films, Si / Mo / Ru periodic multilayer films, Si / Mo / Ru / Mo periodic multilayer films, Si / Ru / Mo / Ru periodic multilayer films, etc., can be used. The material of the multilayer reflective film can be selected considering the exposure wavelength.

[0040] The reflectivity of such a multilayer reflective film 12 on its own is, for example, 65% or more. The upper limit of the reflectivity of the multilayer reflective film 12 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 12 can be selected to satisfy Bragg's law.

[0041] The multilayer reflective film 12 can be formed by known methods. For example, the multilayer reflective film 12 can be formed by ion beam sputtering.

[0042] For example, if the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film with a thickness of approximately 3 nm is formed on the substrate 10 using an ion beam sputtering method with a Mo target. Next, a Si film with a thickness of approximately 4 nm is formed using a Si target. By repeating this operation, a multilayer reflective film 12 can be formed with 40 to 60 periods of stacked Mo / Si films. In this case, the surface layer of the multilayer reflective film 12 opposite to the substrate 10 is a Si-containing layer (Si film). The thickness of one period of Mo / Si film is 7 nm.

[0043] <Protective film> To protect the multilayer reflective film 12 from dry etching and cleaning during the manufacturing process of the reflective mask 200 described later, a protective film 14 can be formed on the multilayer reflective film 12 or in contact with its surface. The protective film 14 also has the function of protecting the multilayer reflective film 12 when correcting black defects in the transfer pattern (absorber pattern) using an electron beam (EB). By forming the protective film 14 on the multilayer reflective film 12, damage to the surface of the multilayer reflective film 12 during the manufacturing of the reflective mask 200 can be suppressed. As a result, the reflectivity characteristics of the multilayer reflective film 12 to EUV light are improved.

[0044] The protective film 14 can be deposited using known methods. Examples of methods for depositing the protective film 14 include ion beam sputtering, magnetron sputtering, reactive sputtering, vapor deposition (CVD), and vacuum deposition. The protective film 14 may also be deposited continuously by ion beam sputtering after the deposition of the multilayer reflective film 12.

[0045] In the multilayer reflective substrate 100 of this embodiment, the protective film 14 includes a first metal and a second metal.

[0046] The standard free energy of formation of the fluoride of the first metal is higher than the standard free energy of formation of RuF5. The standard free energy of formation (ΔG) of RuF5 is, for example, -948 kJ / mol. In other words, the standard free energy of formation of the fluoride of the first metal is preferably higher than -948 kJ / mol, and more preferably higher than -700 kJ / mol.

[0047] The first metals are iridium (Ir), palladium (Pd), gold (Au), and platinum (Pt). Preferably, the first metal is at least one metal selected from the group consisting of iridium (Ir) and rhodium (Rh). More preferably, the first metal is iridium (Ir). The standard free energy of formation (ΔG) of the fluorides of these metals are, for example, as shown in Table 1 below.

[0048] [Table 1]

[0049] The extinction coefficient (k) of the second metal at a wavelength of 13.5 nm for EUV light is 0.03 or less, and more preferably 0.02 or less. The second metal is preferably at least one metal selected from the group consisting of zirconium (Zr), ruthenium (Ru), yttrium (Y), lanthanum (La), niobium (Nb), rubidium (Rb), and titanium (Ti). The second metal is more preferably at least one selected from zirconium (Zr) and ruthenium (Ru). The extinction coefficients (k) of these metals at a wavelength of 13.5 nm are shown in Table 2 below.

[0050] [Table 2]

[0051] The protective film 14 may contain elements other than the first and second metals. For example, the protective film 14 may contain at least one element selected from the group consisting of nitrogen (N), oxygen (O), carbon (C), and boron (B). If the protective film 14 contains nitrogen (N), the N content is preferably 0.1 atomic% or more, and more preferably 1 atomic% or more. Furthermore, the N content is preferably 50 atomic% or less, and more preferably 25 atomic% or less. When the material of the protective film 14 contains Ir, Zr, and N, the N content is preferably 0.1 to 50 atomic%, and more preferably 1 to 25 atomic%. When the material of the protective film 14 contains Ir, Ru, and N, the N content is preferably 0.1 to 15 atomic percent, and more preferably 1 to 10 atomic percent. If the material of the protective film 14 contains Rh, Zr, and N, the N content is preferably 0.1 to 50 atomic percent, and more preferably 1 to 25 atomic percent. If the material of the protective film 14 contains Rh, Ru, and N, the N content is preferably 0.1 to 15 atomic percent, and more preferably 1 to 10 atomic percent.

[0052] The protective film 14 can be deposited by a sputtering method (coarse sputtering method) using a target containing a first metal and a target containing a second metal. Alternatively, the protective film 14 can be deposited by a sputtering method using an alloy containing the first metal and the second metal as a target.

[0053] Examples of materials for the protective film 14, which includes the first and second metals, include IrZr, IrRu, RhRu, and RhZr. However, the materials for the protective film 14 are not limited to these.

[0054] The protective film 14 has etching resistance to any of the following: oxygen-containing chlorine-based gases, oxygen-free chlorine-based gases, and fluorine-based gases.

[0055] The inclusion of a first metal in the protective film 14 improves its etching resistance to fluorine-based gases (e.g., XeF2 + H2O). The standard free energy of formation of the fluoride of the first metal is higher than that of RuF5. Therefore, the protective film 14 containing the first metal has the advantage of being less likely to react with fluorine-based gases to form fluoride compared to protective films made from conventional Ru-based materials.

[0056] The content of the first metal in the protective film 14 is preferably 10 atomic percent or more, more preferably 20 atomic percent or more, and even more preferably 50 atomic percent or more. By including the first metal in the protective film 14 in such proportions, the protective film 14 is less likely to react with fluorine-based gases to form fluorides, and thus the etching resistance of the protective film 14 to fluorine-based gases becomes sufficiently high.

[0057] The content of the first metal in the protective film 14 is preferably 90 atomic percent or less, and more preferably 80 atomic percent or less. If the protective film 14 contains more of the first metal than this, the extinction coefficient of the protective film 14 will increase, which may reduce the reflectance of the multilayer reflective film 12 to EUV light to a predetermined value or less (for example, 65% or less).

[0058] By including a second metal in the protective film 14, the reflectance of the multilayer reflective film 12 to EUV light can be maintained at or above a predetermined value (e.g., 65% or more).

[0059] The content of the second metal in the protective film 14 is preferably 10 atomic percent or more, and more preferably 20 atomic percent or more. By including the second metal in the protective film 14 in such proportions, the reflectance of the multilayer reflective film 12 can be maintained at or above a predetermined value (for example, 65% or more).

[0060] The content of the second metal in the protective film 14 is preferably 90 atomic percent or less, more preferably 80 atomic percent or less, and even more preferably less than 50 atomic percent. If the protective film 14 contains more of the second metal than this, the etching resistance to fluorine-based gases and the cleaning resistance to sulfuric acid peroxide (SPM) may become insufficient.

[0061] In light of the reflectance of the multilayer reflective film 12, its etching resistance to fluorine-based gases, and its cleaning resistance to sulfuric acid peroxide (SPM), the specific composition ratios of the first and second metals are shown below. When the material of the protective film 14 contains Ir and Zr, the composition ratio of Ir to Zr (Ir:Zr) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Ir and Ru, the composition ratio of Ir to Ru (Ir:Ru) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Ir and Y, the composition ratio of Ir to Y (Ir:Y) is preferably 9:1 to 1:9, and more preferably 7:3 to 1:4. When the material of the protective film 14 contains Ir and La, the composition ratio of Ir to La (Ir:La) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Ir and Nb, the composition ratio of Ir to Nb (Ir:Nb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Ir and Rb, the composition ratio of Ir to Rb (Ir:Rb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Ir and Ti, the composition ratio of Ir to Ti (Ir:Ti) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pd and Zr, the composition ratio of Pd to Zr (Pd:Zr) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Pd and Ru, the composition ratio of Pd to Ru (Pd:Ru) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Pd and Y, the composition ratio of Pd to Y (Pd:Y) is preferably 9:1 to 1:9, and more preferably 7:3 to 1:4. When the material of the protective film 14 contains Pd and La, the composition ratio of Pd to La (Pd:La) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pd and Nb, the composition ratio of Pd to Nb (Pd:Nb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pd and Rb, the composition ratio of Pd to Rb (Pd:Rb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pd and Ti, the composition ratio of Pd to Ti (Pd:Ti) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Au and Zr, the composition ratio of Au to Zr (Au:Zr) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Au and Ru, the composition ratio of Au to Ru (Au:Ru) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Au and Y, the composition ratio of Au to Y (Au:Y) is preferably 9:1 to 1:9, and more preferably 7:3 to 1:4. When the material of the protective film 14 contains Au and La, the composition ratio of Au to La (Au:La) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Au and Nb, the composition ratio of Au to Nb (Au:Nb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Au and Rb, the composition ratio of Au to Rb (Au:Rb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Au and Ti, the composition ratio of Au to Ti (Au:Ti) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pt and Zr, the composition ratio of Pt to Zr (Pt:Zr) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Pt and Ru, the composition ratio of Pt to Ru (Pt:Ru) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Pt and Y, the composition ratio of Pt to Y (Pt:Y) is preferably 9:1 to 1:9, and more preferably 7:3 to 1:4. When the material of the protective film 14 contains Pt and La, the composition ratio of Pt to La (Pt:La) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pt and Nb, the composition ratio of Pt to Nb (Pt:Nb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pt and Rb, the composition ratio of Pt to Rb (Pt:Rb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Pt and Ti, the composition ratio of Pt to Ti (Pt:Ti) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Rh and Zr, the composition ratio of Rh to Zr (Rh:Zr) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Rh and Ru, the composition ratio of Rh to Ru (Rh:Ru) is preferably 9:1 to 1:9, and more preferably 4:1 to 1:4. When the material of the protective film 14 contains Rh and Y, the composition ratio of Rh to Y (Rh:Y) is preferably 9:1 to 1:9, and more preferably 7:3 to 1:4. When the material of the protective film 14 contains Rh and La, the composition ratio of Rh to La (Rh:La) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Rh and Nb, the composition ratio of Rh to Nb (Rh:Nb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Rh and Rb, the composition ratio of Rh to Rb (Rh:Rb) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2. When the material of the protective film 14 contains Rh and Ti, the composition ratio of Rh to Ti (Rh:Ti) is preferably 9:1 to 1:1, and more preferably 17:3 to 3:2.

[0062] Figure 2 is a schematic cross-sectional view showing another example of the multilayer reflective film substrate 100 of this embodiment. As shown in Figure 2, the protective film 14 may include a Si material layer 16 containing silicon (Si) on the side in contact with the multilayer reflective film 12. That is, the protective film 14 may include a Si material layer 16 on the side in contact with the multilayer reflective film 12 and a protective layer 18 formed on the Si material layer 16. The protective layer 18 is a layer containing a first metal and a second metal, similar to the protective film 14 described above. The Si material layer 16 may be, for example, silicon (Si), silicon oxide (SiO, SiO2, Si3O2, etc.). x O y (x, y are integers greater than or equal to 1), silicon nitride (SiN, Si3N4, etc.) x N y (x and y are integers greater than or equal to 1), and silicon oxide nitride (Si such as SiON). x O y N z The Si material layer 16 may be a Si film that is the uppermost high refractive index layer of the multilayer reflective film 12 when the multilayer reflective film 12 is a Mo / Si multilayer film and the Mo film and Si film are stacked in that order from the substrate 10 side.

[0063] The multilayer reflective film 12, the Si material layer 16, and the protective layer 18 may be deposited by the same method or by different methods. For example, the multilayer reflective film 12 and the Si material layer 16 may be deposited continuously by ion beam sputtering, and then the protective layer 18 may be deposited by magnetron sputtering. Alternatively, the multilayer reflective film 12 to the protective layer 18 may be deposited continuously by ion beam sputtering.

[0064] Conventional Ru-based protective films sometimes contain elements (such as Nb) that react with fluorine-based etching gases to produce highly volatile substances, and these highly volatile substances can cause defects in the protective film. When defects occur in the protective film, fluorine-based etching gases can enter the Si material layer through these defects, forming highly volatile SiF4. This SiF4 can then expand between the protective film and the Si material layer, potentially causing the protective film to break down. In the multilayer reflective film substrate 100 of this embodiment, the protective layer 18 contains a first metal and a second metal, making it less likely for the protective layer 18 to react with fluorine-based etching gases to produce fluorides. Therefore, it is possible to prevent fluoride from expanding between the protective layer 18 and the Si material layer 16, which could cause the protective layer 18 to break down.

[0065] Figure 3 is a schematic cross-sectional view showing an example of a reflective mask blank 110 according to this embodiment. The reflective mask blank 110 shown in Figure 3 has an absorber film 24 for absorbing EUV light on top of the protective film 14 of the multilayer reflective film substrate 100 described above. The reflective mask blank 110 may further have other thin films, such as a resist film 26, on top of the absorber film 24.

[0066] Figure 4 is a schematic cross-sectional view showing another example of a reflective mask blank 110. As shown in Figure 4, the reflective mask blank 110 may have an etching mask film 28 between the absorber film 24 and the resist film 26.

[0067] <Absorbing membrane> In this embodiment, the absorber film 24 of the reflective mask blank 110 is formed on the protective film 14. The basic function of the absorber film 24 is to absorb EUV light. The absorber film 24 may be an absorber film 24 intended for absorbing EUV light, or it may be an absorber film 24 having a phase shift function that also takes into account the phase difference of EUV light. An absorber film 24 having a phase shift function absorbs EUV light and also reflects a portion of the EUV light to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 24 having a phase shift function, the portion where the absorber film 24 is formed absorbs EUV light to reduce its brightness while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Also, in the region where the absorber film 24 is not formed (field portion), EUV light is reflected by the multilayer reflective film 12 via the protective film 14. Therefore, a desired phase difference is created between the light reflected from the absorber film 24 having a phase shift function and the light reflected from the field portion. The absorber film 24 having a phase shift function is preferably formed such that the phase difference between the reflected light from the absorber film 24 and the reflected light from the multilayer reflective film 12 is between 170 and 190 degrees. The light with inverted phase differences near 180 degrees interferes with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast leads to an increase in resolution, and various exposure-related margins such as exposure margin and focus margin can be increased.

[0068] The absorber film 24 may be a single layer or a multilayer film consisting of multiple layers (for example, a lower absorber film and an upper absorber film). In the case of a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constants and film thickness of the upper absorber film can be appropriately set so that it acts as an anti-reflective film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. Furthermore, if a film with oxygen (O) and nitrogen (N), etc., which improve oxidation resistance is added to the upper absorber film, the stability over time is improved. In this way, by making the absorber film 24 a multilayer film, it becomes possible to add various functions to the absorber film 24. If the absorber film 24 has 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 the desired reflectance.

[0069] The material for the absorber film 24 is not particularly limited, as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably etchable by dry etching with chlorine (Cl)-based gas and / or fluorine (F)-based gas), and has a high etching selectivity ratio with respect to the protective film 14. As materials possessing such functions, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or compounds thereof, can be preferably used.

[0070] In the reflective mask blank 110 of this embodiment, it is preferable to use a material containing ruthenium (Ru) (Ru-based material) as the material for the absorber film 24. As the Ru-based material, it is preferable to use a material containing ruthenium (Ru) and at least one of the following elements: chromium (Cr), nickel (Ni), cobalt (Co), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), germanium (Ge), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re).

[0071] When the material of the absorbent membrane 24 contains Ru and Cr, the composition ratio of Ru to Cr (Ru:Cr) is preferably 15:1 to 1:20. When the material of the absorbent membrane 24 contains Ru and Ni, the composition ratio of Ru to Ni (Ru:Ni) is preferably 20:1 to 1:4. When the material of the absorbent membrane 24 contains Ru and Co, the composition ratio of Ru to Co (Ru:Co) is preferably 20:1 to 1:5. When the material of the absorbent membrane 24 contains Ru and Al, the composition ratio of Ru to Al (Ru:Al) is preferably 20:1 to 4:5. When the material of the absorber membrane 24 contains Ru and Si, the composition ratio of Ru to Si (Ru:Si) is preferably 20:1 to 1:1. When the material of the absorbent membrane 24 contains Ru and Ti, the composition ratio of Ru to Ti (Ru:Ti) is preferably 20:1 to 1:20. When the material of the absorbent membrane 24 contains Ru and V, the composition ratio of Ru to V (Ru:V) is preferably 20:1 to 1:20. When the material of the absorber membrane 24 contains Ru and Ge, the composition ratio of Ru to Ge (Ru:Ge) is preferably 20:1 to 1:1. When the material of the absorbent membrane 24 contains Ru and Nb, the composition ratio of Ru to Nb (Ru:Nb) is preferably 20:1 to 5:1. When the material of the absorbent membrane 24 contains Ru and Mo, the composition ratio of Ru to Mo (Ru:Mo) is preferably 20:1 to 4:1. When the material of the absorbent membrane 24 contains Ru and Sn, the composition ratio of Ru to Sn (Ru:Sn) is preferably 20:1 to 3:2. When the material of the absorbent membrane 24 contains Ru and Te, the composition ratio of Ru to Te (Ru:Te) is preferably 20:1 to 3:1. When the material of the absorber membrane 24 contains Ru and Hf, the composition ratio of Ru to Hf (Ru:Hf) is preferably 20:1 to 1:2. When the material of the absorbent membrane 24 contains Ru and W, the composition ratio of Ru to W (Ru:W) is preferably 20:1 to 1:20. When the material of the absorbent membrane 24 contains Ru and Re, the composition ratio of Ru to Re (Ru:Re) is preferably 20:1 to 1:20.

[0072] The above explanation mainly described binary Ru-based materials, but ternary Ru-based materials (e.g., RuCrNi, RuCrCo, RuNiCo, and RuCrW) or quaternary Ru-based materials (e.g., RuCrNiCo and RuCrCoW) can also be used.

[0073] The absorber film 24 may contain elements other than the metals mentioned above. For example, the absorber film 24 may contain at least one element selected from the group consisting of nitrogen (N), oxygen (O), carbon (C), and boron (B). Examples of materials for such an absorber film 24 include RuN, RuCrN, RuCrO, etc. Such an absorber film 24 can be etched with a mixed gas of chlorine-based gas and oxygen gas.

[0074] The absorber film 24 containing the Ru-based material described above can be formed by known methods such as DC sputtering and magnetron sputtering methods such as RF sputtering. For example, the absorber film 24 can be deposited by a sputtering method using an alloy target containing Ru and at least one element selected from the group consisting of Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re.

[0075] Furthermore, the absorber film 24 can be deposited by a sputtering method (coarse sputtering method) using a Ru target and at least one target from among Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re.

[0076] Ru-based materials containing Ru and at least one element from Cr, Ni, Co, V, Nb, Mo, W, and Re can be dry-etched with oxygen-containing chlorine gas or oxygen gas. Ru-based materials containing Ru and at least one element from Al, Si, Ti, Ge, Sn, and Hf can be dry-etched with oxygen-free chlorine gas. Examples of chlorine gases that can be used include Cl2, SiCl4, CHCl3, CCl4, and BCl3. These etching gases may optionally contain inert gases such as He and / or Ar.

[0077] Furthermore, Ru-based materials containing Ru and at least one element from Al, Si, Ti, Nb, Mo, Sn, Te, Hf, W, and Re can be dry-etched with fluorine-based gases. Examples of fluorine-based gases that can be used include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, C3F8, and SF6. These etching gases may be used individually or in mixtures of two or more. These etching gases may optionally contain inert gases such as He and / or Ar, or O2 gas.

[0078] According to the reflective mask blank 110 of this embodiment, the protective film 14 contains a first metal and a second metal. Since this protective film 14 has sufficient resistance to the etching gas used to etch the absorber film 24, it can function as an etching stopper when etching the absorber film 24.

[0079] According to the reflective mask blank 110 of this embodiment, the protective film 14 contains a first metal and a second metal. Since this protective film 14 has sufficient resistance to fluorine-based etching gases (e.g., XeF2 + H2O) used in the repair process of the absorber pattern, it is possible to prevent the multilayer reflective film 12 from being damaged by the fluorine-based etching gases used in the repair process.

[0080] According to the reflective mask blank 110 of this embodiment, since the protective film 14 contains a first metal and a second metal, it is possible to prevent the multilayer reflective film 12 from being damaged by the fluorine-based etching gas used in the repair process, while maintaining the reflectivity of the multilayer reflective film 12 at or above a predetermined value (for example, 65% or more).

[0081] Figure 5 is a schematic cross-sectional view showing another example of a reflective mask blank 110. As shown in Figure 5, the absorber film 24 may include a buffer layer 24b on the side in contact with the protective film 14. That is, the absorber film 24 may include a buffer layer 24b on the side in contact with the protective film 14 and an absorbent layer 24c formed on the buffer layer 24b. The absorbent layer 24c is preferably formed of the same material as the absorber film 24 described above, and more preferably of a material containing Ru (Ru-based material).

[0082] Depending on the selection of materials for the protective film 14 and the absorption layer 24c, a problem may arise in which the etching selectivity ratio of the absorption layer 24c to the protective film 14 is not sufficiently high. Even in this case, it is possible to avoid the problem of insufficient etching selectivity ratio of the absorption layer 24c to the protective film 14 by interposing a buffer layer 24b between the protective film 14 and the absorption layer 24c.

[0083] The material of the buffer layer 24b is preferably a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), and boron (B). Examples of such materials include TaO, TaBO, TaN, TaBN, etc. The buffer layer 24b containing such a material can be etched with a fluorine-based gas or a chlorine-based gas that does not contain oxygen.

[0084] Furthermore, the material of the buffer layer 24b is preferably a material containing silicon (Si), and more preferably a material containing silicon (Si) and one or more elements selected from oxygen (O) and nitrogen (N). Examples of such materials include SiO2, SiO, SiN, SiON, SiC, SiCO, SiCN, SiCON, MoSi, MoSiO, MoSiN, and MoSiON. The buffer layer 24b containing such a material can be etched with a fluorine-based gas.

[0085] The thickness of the buffer layer 24b is preferably 0.5 nm or more, more preferably 1 nm or more, and even more preferably 2 nm or more, from the viewpoint of suppressing damage to the protective film 14 and changes in optical properties during etching of the absorption layer 24c. Furthermore, the thickness of the buffer layer 24b is preferably 25 nm or less, more preferably 15 nm or less, even more preferably 10 nm or less, and particularly preferably less than 4 nm, from the viewpoint of reducing the total thickness of the absorption layer 24c and the buffer layer 24b.

[0086] According to the reflective mask blank 110 of this embodiment, the protective film 14 contains a first metal and a second metal. Since this protective film 14 has sufficient resistance to the etching gas used to etch the buffer layer 24b described above, it can function as an etching stopper when etching the buffer layer 24b.

[0087] <Conductive film on the back surface> A back-side conductive film 22 for electrostatic chucks is formed on the second main surface of the substrate 100 (the main surface opposite to the side on which the multilayer reflective film 12 is formed). For electrostatic chucks, the sheet resistance required for the back-side conductive film 22 is usually 100 Ω / □ (Ω / square) or less. The back-side conductive film 22 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material of the back-side conductive film 22 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back-side conductive film 22 is preferably a Cr compound containing Cr and at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Furthermore, the material of the back surface conductive film 22 is preferably Ta (tantalum), 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, TaHO, TaHN, TaHON, TaHON, TaHCON, TaSi, TaSiO, TaSiN, TaSiONCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0088] The thickness of the back surface conductive film 22 is not particularly limited as long as it functions as a film for electrostatic chucks, but is usually between 10 nm and 200 nm. Furthermore, it is preferable that the back surface conductive film 22 has the function of adjusting the stress on the second main surface side of the reflective mask blank 110. That is, it is preferable that the back surface conductive film 22 has the function of adjusting the reflective mask blank 110 to be flat by balancing the stress caused by the formation of a thin film on the first main surface with the stress on the second main surface.

[0089] <Etching mask film> An etching mask film 28 may be formed on the absorber film 24. It is preferable to use a material for the etching mask film 28 that has a high etching selectivity ratio of the absorber film 24 to the etching mask film 28. The etching selectivity ratio of the absorber film 24 to the etching mask film 28 is preferably 1.5 or higher, and more preferably 3 or higher.

[0090] When etching the absorber film 24 with an oxygen-free chlorine-based gas or an oxygen-containing chlorine-based gas, the etching mask film 28 can be made from a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), and boron (B). Examples of such materials include TaO, TaBO, TaN, and TaBN.

[0091] Furthermore, when etching the absorber film 24 with an oxygen-free chlorine-based gas or an oxygen-containing chlorine-based gas, a material containing silicon (Si) may be used as the material for the etching mask film 28, and it is preferable to use a material containing silicon (Si) and one or more elements selected from oxygen (O) and nitrogen (N). Examples of such materials include SiO2, SiO, SiN, SiON, SiC, SiCO, SiCN, SiCON, MoSi, MoSiO, MoSiN, and MoSiON.

[0092] Furthermore, when etching the absorber film 24 with a fluorine-based gas, chromium or a chromium compound can be used as the material for the etching mask film 28. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. The etching mask film 28 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and even more preferably is a CrO-based film (CrO film, CrON film, CrOC film, or CrOCN film) containing chromium and oxygen.

[0093] By combining it with the material of the protective film 14, damage to the protective film 14 when the etching mask film 28 is removed by dry etching can be suppressed.

[0094] The thickness of the etching mask film 28 is preferably 3 nm or more in order to accurately form a pattern on the absorber film 24. Furthermore, the thickness of the etching mask film 28 is preferably 15 nm or less in order to reduce the thickness of the resist film 26.

[0095] <Reflective mask> The reflective mask 200 of this embodiment can be manufactured using the reflective mask blank 110 according to this embodiment. 200 An example of a manufacturing method will be described.

[0096] Figures 6A to 6E are schematic diagrams showing an example of a method for manufacturing a reflective mask 200. As shown in the figures, first, a reflective mask blank 110 is prepared, which has 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 an absorber film 24 formed on the protective film 14 (Figure 6A). Next, a resist film 26 is formed on the absorber film 24 (Figure 6B). A pattern is drawn on the resist film 26 using an electron beam lithography apparatus, and then a resist pattern 26a is formed by going through a development and rinsing process (Figure 6C).

[0097] The absorber film 24 is dry-etched using the resist pattern 26a as a mask. This etches the parts of the absorber film 24 that are not covered by the resist pattern 26a, forming the absorber pattern 24a (Figure 6D).

[0098] For example, a fluorine-based gas and / or a chlorine-based gas can be used as the etching gas for the absorber film 24. Examples of fluorine-based gases include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2. Examples of chlorine-based gases include Cl2, SiCl4, CHCl3, CCl4, and BCl3. Alternatively, 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 may further contain inert gases such as He and / or Ar as needed.

[0099] After the absorbent pattern 24a is formed, the resist pattern 26a is removed with a resist stripping solution. After removing the resist pattern 26a, the reflective mask 200 of this embodiment is obtained by going through a wet cleaning process using an acidic or alkaline aqueous solution (Figure 6E).

[0100] Furthermore, when using a reflective mask blank 110 in which an etching mask film 28 is formed on an absorber film 24, an additional step is added: first, a pattern (etching mask pattern) is formed on the etching mask film 28 using the resist pattern 26a as a mask, and then a pattern is formed on the absorber film 24 using the etching mask pattern as a mask.

[0101] The reflective mask 200 obtained in this manner has a structure in which a multilayer reflective film 12, a protective film 14, and an absorber pattern 24a are laminated on a substrate 10.

[0102] The region 30 in which the multilayer reflective film 12 (including the protective film 14) is exposed has the function of reflecting EUV light. The region 32 in which the multilayer reflective film 12 (including the protective film 14) is covered by the absorber pattern 24a has the function of absorbing EUV light. According to the reflective mask 200 of this embodiment, the thickness of the absorber pattern 24a such that the reflectance is, for example, 2.5% or less can be made thinner than in the conventional method, so that a finer pattern can be transferred to the object to be transferred.

[0103] <Manufacturing method for semiconductor devices> A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask 200 of this embodiment. This transfer pattern has the shape of the pattern transferred from the reflective mask 200. By forming a transfer pattern on a semiconductor substrate with the reflective mask 200, a semiconductor device can be manufactured.

[0104] Using Figure 7, we will explain a method for transferring a pattern onto a resist-coated semiconductor substrate 56 using EUV light.

[0105] Figure 7 shows the pattern transfer apparatus 50. The pattern transfer apparatus 50 includes a laser plasma X-ray source 52, a reflective mask 200, and a reduction optical system 54, etc. An X-ray reflective mirror is used as the reduction optical system 54.

[0106] The pattern reflected by the reflective mask 200 is typically reduced to about 1 / 4 of its original size by the reduction optical system 54. For example, a wavelength band of 13-14 nm is used as the exposure wavelength, and the optical path is pre-set to be in a vacuum. Under these 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 via the reduction optical system 54.

[0107] Light reflected by the reflective mask 200 enters the reduction optical system 54. The light entering 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, the semiconductor substrate 56 For example, a predetermined wiring pattern can be formed on top. By going through such a process and other necessary processes, a semiconductor device is manufactured. [Examples]

[0108] Examples and comparative examples will be described below with reference to the drawings.

[0109] (Multilayer reflective substrate 100) First, a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) substrate 10 with a first main surface and a second main surface polished was prepared. This substrate 10 is made of low thermal expansion glass (SiO2-TiO2 glass). The main surface of the substrate 10 was polished by a rough polishing process, a precision polishing process, a localized polishing process, and a touch polishing process.

[0110] Next, a multilayer reflective film 12 was formed on the main surface (first main surface) of the substrate 10. To make the multilayer reflective film 12 formed on the substrate 10 suitable for EUV light with a wavelength of 13.5 nm, a periodic multilayer reflective film 12 made of Mo and Si was formed. The multilayer reflective film 12 was formed by alternately stacking Mo films and Si films on the substrate 10 using an ion beam sputtering method with a Mo target and a Si target and krypton (Kr) as the process gas. First, a Si film was deposited to a thickness of 4.2 nm, and then a Mo film was deposited to a thickness of 2.8 nm. This constituted one period, and 40 periods were stacked in the same manner to form the multilayer reflective film 12.

[0111] Next, a Si material layer 16 was formed on the multilayer reflective film 12. The multilayer reflective film 12 and the Si material layer 16 were deposited continuously by ion beam sputtering. The Si material layer 16 was deposited to a thickness of 4.0 nm using a Si target and krypton (Kr) as the process gas.

[0112] Next, a protective layer 18 was formed on the Si material layer 16. The protective layer 18 was formed by magnetron sputtering (coarse sputtering) in an Ar gas atmosphere using two types of metal targets for the protective layer material shown in Table 3. The composition of the protective layer 18 was measured by X-ray photoelectron spectroscopy (XPS). Table 3 below shows the composition and film thickness of the protective layer 18 in the examples and comparative examples.

[0113] (Evaluation of the multilayer reflective substrate 100) Using the multilayer reflective film substrates 100 of Examples 1-3 and Comparative Example 1, tests were conducted to evaluate the repair resistance and reflectivity of the protective film 14 (protective layer 18). First, a test was conducted to evaluate the repair resistance of the protective film 14 using a repair device. Specifically, the protective film 14 was repeatedly irradiated with an electron beam while a fluorine-based etching gas (XeF2 + H2O) was supplied around it. The test conditions were as follows: (Repair resistance test conditions) Electron beam acceleration voltage: 1kV XeF2 temperature: 0℃ H2O temperature: -42℃ Electron beam irradiation time per unit pixel (1.5 nm × 1.5 nm): 4.00 e -8 [s] Definition of one loop: One loop is defined as the electron beam being repeatedly scanned horizontally with a predetermined interval in the vertical direction, until the entire 500nm x 500nm area has been scanned.

[0114] After repeatedly irradiating the surface of the protective film 14 with an electron beam, the surface of the protective film 14 was imaged using a scanning electron microscope (SEM). The number of electron beam irradiations (loop counts) required to observe damage to the surface of the protective film 14 using the SEM was then measured. Table 3 below shows the number of electron beam irradiations (loop counts) for Examples 1-3 and Comparative Example 1. In Table 3, the number of electron beam irradiations (loop counts) is shown as a ratio with the number of loops for Comparative Example 1 set to 1.0.

[0115] (Reflective mask blank 110) In addition to the multilayer reflective substrate 100 used in the repair resistance test described above, multilayer reflective substrates 100 for Examples 1 to 3 and Comparative Example 1 were prepared. Using the prepared multilayer reflective substrates 100, reflective mask blanks 110 containing an absorber film 24 were manufactured. The manufacturing method of the reflective mask blanks 110 will be described below.

[0116] An absorber film 24 (phase-shift film) made of RuCr was formed on the protective layer 18 of a multilayer reflective film substrate 100 by DC magnetron sputtering. The RuCr film was deposited using a RuCr target in an Ar gas atmosphere to a thickness of 45.0 nm. The composition (atomic ratio) of the RuCr film was Ru:Cr = 7:93.

[0117] Next, a back-side conductive film 22 made of CrN was formed on the second main surface (back-side main surface) of the substrate 10 by magnetron sputtering (reactive sputtering) under the following conditions. Formation conditions for the conductive film 22 on the back surface: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90 atomic%, N: 10 atomic%), film thickness 20 nm.

[0118] As described above, reflective mask blanks 110 for Examples 1-3 and Comparative Example 1 were manufactured.

[0119] (Reflective mask 200) Next, a reflective mask 200 was manufactured using the reflective mask blank 110 described above. The manufacturing process of the reflective mask 200 will be explained with reference to Figures 6B to 6E.

[0120] First, as shown in Figure 6B, a resist film 26 was formed on the absorber film 24 of the reflective mask blank 110. Next, a desired pattern such as a circuit pattern was drawn (exposed) onto this resist film 26, and then developed and rinsed to form a predetermined resist pattern 26a (Figure 6C). Next, using the resist pattern 26a as a mask, the absorber film 24 was dry-etched using a mixed gas of Cl2 gas and O2 gas (gas flow rate ratio Cl2:O2=4:1) to form an absorber pattern 24a (Figure 6D).

[0121] Subsequently, the resist pattern 26a was removed using ashing or a resist stripping solution. Finally, wet washing with pure water (DIW) was performed to produce the reflective masks 200 of Examples 1-3 and Comparative Example 1 (Figure 6E).

[0122] (Evaluation of Reflective Mask 200) Using the reflective masks 200 of Examples 1-3 and Comparative Example 1 that were manufactured, tests were conducted to evaluate the reflectivity of the protective film 14 (protective layer 18).

[0123] The reflectance of the surface of the protective film 14 not covered by the absorber pattern 24a to EUV light with a wavelength of 13.5 nm was measured. Table 3 below shows the reflectance measurement results for Examples 1 to 3 and Comparative Example 1.

[0124] [Table 3]

[0125] As can be seen from the results shown in Table 3, the number of loops in the protective film 14 of the multilayer reflective substrate 100 in Examples 1 to 3 was greater than the number of loops in the protective film of the multilayer reflective substrate in Comparative Example 1. In other words, it was found that the protective layer 18 (protective film 14) of the multilayer reflective substrate 100 in Examples 1 to 3 has high resistance to repair by electron beam irradiation using a fluorine-based etching gas (XeF2 + H2O).

[0126] Furthermore, the reflectivity of the protective layer 18 (protective film 14) of the reflective mask 200 in Examples 1 to 3 was 65% or higher in all cases, maintaining a value above the predetermined value. [Explanation of symbols]

[0127] 10 circuit boards 12 Multilayer reflective coating 14 Protective film 16 Si material layer 18 Protective layer 22 Conductive film on the back surface 24 Absorbent membrane 24a Absorber pattern 24b Buffer layer 24c absorption layer 26 Resist film 28 Etching mask film 100 Multilayer reflective substrates 110 Reflective Mask Blank 200 Reflective Masks

Claims

1. A multilayer reflective 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 comprises a first metal and a second metal. The standard free energy of formation of the fluoride of the first metal is RuF ５ Higher than the standard free energy of formation, The second metal has an extinction coefficient of 0.03 or less at a wavelength of 13.5 nm. The first metal is iridium (Ir), and the second metal is at least one selected from zirconium (Zr) and ruthenium (Ru), or the first metal is rhodium (Rh), and the second metal is ruthenium (Ru). A multilayer reflective substrate characterized in that the content of the first metal is greater than the content of the second metal.

2. The multilayer reflective substrate according to claim 1, characterized in that the content of the second metal is 40 atomic percent or less.

3. The multilayer reflective film substrate according to claim 1 or 2, characterized in that the content of the first metal is 60 atomic percent or more.

4. A multilayer reflective substrate according to any one of claims 1 to 3, characterized in that the first metal is iridium (Ir) and the second metal is ruthenium (Ru).

5. A multilayer reflective substrate according to any one of claims 1 to 3, characterized in that the first metal is rhodium (Rh) and the second metal is ruthenium (Ru).

6. A multilayer reflective substrate according to any one of claims 1 to 3, characterized in that the first metal is iridium (Ir) and the second metal is zirconium (Zr).

7. A reflective mask blank characterized by comprising an absorbent film on the protective film of a multilayer reflective film substrate according to any one of claims 1 to 6.

8. The reflective mask blank according to claim 7, characterized in that the absorbent membrane contains ruthenium (Ru).

9. The absorbent membrane comprises a buffer layer and an absorbent layer provided on the buffer layer. The buffer layer comprises tantalum (Ta) or silicon (Si), The reflective mask blank according to claim 7 or 8, characterized in that the absorption layer contains ruthenium (Ru).

10. A reflective mask characterized by comprising an absorbent pattern obtained by patterning the absorbent membrane of the reflective mask blank described in any one of claims 7 to 9.

11. A method for manufacturing a semiconductor device, characterized by comprising the step of performing a lithography process using an exposure apparatus with a reflective mask as described in claim 10 to form a transfer pattern on a transfer object.

Images