Reflective mask blank, method for manufacturing reflective mask blank, reflective mask, and method for manufacturing reflective mask

Abstract

Provided is a reflective mask blank having a conductive film with a small transmittance distribution of light at 632 nm and 1064 nm and excellent flatness. A reflective mask blank having a substrate, a conductive film disposed on one surface side of the substrate, a multilayer reflective film that reflects EUV light disposed on the other surface side of the substrate, and an absorber film disposed on the side opposite to the substrate side of the multilayer reflective film, wherein the conductive film contains one or more elements selected from the group consisting of tantalum and chromium, the total content of nitrogen and boron contained in the conductive film is more than 33 atomic% with respect to all atoms of the conductive film, the film thickness of the conductive film is 20 to 150 nm, the film thickness of the conductive film at the center of the substrate is larger than the film thickness of the conductive film at the end of the substrate, and the maximum film thickness difference in the in-plane direction of the conductive film is 0.30 to 1.00 nm. An EUV lithography reflective mask blank.

Description

Technical Field

[0001] The present invention relates to a reflective mask used for EUV (Extreme Ultra Violet) exposure used in the exposure process of semiconductor manufacturing (that is, for EUV lithography), a method for manufacturing the same, a reflective mask blank which is a substrate of the reflective mask, and a method for manufacturing the same. In this specification, the reflective mask blank for EUV lithography is also simply referred to as "reflective mask blank". Further, the reflective mask for EUV lithography is also simply referred to as "reflective mask".

Background Art

[0002] In recent years, for further miniaturization of semiconductor devices, EUV lithography using EUV light having a central wavelength of around 13.5 nm as a light source has been studied.

[0003] In EUV exposure, due to the characteristics of EUV light, a reflective optical system and a reflective mask are used. The reflective mask has a multilayer reflective film formed on a substrate for reflecting EUV light, and an absorber film for absorbing EUV light is patterned on the multilayer reflective film.

[0004] The EUV light incident on the reflective mask from the illumination optical system of the exposure apparatus is reflected at the portion without the absorber film (opening), and absorbed at the portion with the absorber film (non-opening). As a result, the mask pattern is transferred as a resist pattern onto the wafer through the reduction projection optical system of the exposure apparatus, and subsequent processing is performed.

[0005] On the other hand, in the reflective mask blank before patterning the reflective mask and the absorber film, a conductive film for an electrostatic chuck is often provided on the surface of the substrate opposite to the absorber film side. For example, in the reflective mask blank described in Patent Document 1, a conductive film containing at least one element selected from the group consisting of tantalum and chromium and nitrogen is disclosed.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a reflective mask, in transferring a mask pattern, in order to form a desired pattern, a high flatness is required for the reflective mask blank. Here, a state of high flatness of the reflective mask blank means that the reflective mask blank itself has no warp or the like and is flat. Also, in order to improve the deformation of the substrate due to internal stress in the multilayer reflective film or the absorption layer, a laser beam with a wavelength of 632 nm and a laser beam with a wavelength of 1064 nm are also irradiated from the conductive film side of the reflective mask blank and the reflective mask. When irradiating the laser beam as described above to improve the deformation of the substrate, it is very complicated to adjust the irradiation amount of the laser beam in the in-plane direction. Therefore, the transmittance of the laser beam with the above wavelength is required to be uniform in the in-plane direction of the conductive film.

[0008] When the inventors examined the reflective mask blank described in Patent Document 1, there were cases where the above-described flatness and the uniformity of the transmittance of the laser beam could not be achieved simultaneously at the level required recently, and improvement was required.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a reflective mask blank having a conductive film with a small distribution of transmittance of light of 632 nm and 1064 nm and excellent flatness. Another object of the present invention is to provide a method for manufacturing the above reflective mask blank, and to provide a reflective mask and a method for manufacturing the reflective mask.

Means for Solving the Problems

[0010] As a result of intensive studies on the above problems, the inventors have found that it is important to adjust the content of elements contained in the conductive film and the film thickness of the conductive film in the in-plane direction, and have reached the present invention. That is, the inventors have found that the above problems can be solved by the following configuration. 〔1〕 A substrate, A conductive film disposed on one surface side of the substrate, A multilayer reflective film that reflects EUV light disposed on the other surface side of the substrate, An absorber film disposed on the side opposite to the substrate side of the multilayer reflective film, a reflective mask blank having, The conductive film contains at least one element selected from the group consisting of tantalum and chromium, The total content of nitrogen and boron contained in the conductive film is more than 33 atomic% with respect to all atoms of the conductive film, The film thickness of the conductive film is 20 to 150 nm, The film thickness of the conductive film at the center of the substrate is larger than the film thickness of the conductive film at the end of the substrate, A reflective mask blank for EUV lithography, wherein the maximum film thickness difference in the in-plane direction of the conductive film is 0.30 to 1.00 nm. 〔2〕 The reflective mask blank for EUV lithography according to 〔1〕, wherein the nitrogen content of the conductive film is 35 to 65 atomic% with respect to all atoms of the conductive film. 〔3〕 The reflective mask blank for EUV lithography according to 〔1〕 or 〔2〕, wherein the boron content of the conductive film is more than 0 atomic% and 35 atomic% or less with respect to all atoms of the conductive film. 〔4〕 The reflective mask blank for EUV lithography according to any one of 〔1〕 to 〔3〕, wherein the electrical resistivity of the conductive film is 0.05 to 0.35 mΩ·cm. 〔5〕 The reflective mask blank for EUV lithography according to any one of 〔1〕 to 〔4〕, wherein the surface roughness of the surface on the side opposite to the substrate side of the conductive film is 0.60 nm or less. 〔6〕The conductive film has a multilayer structure composed of two or more layers, and among the above layers, the outermost layer located at the position farthest from the substrate is a layer containing tantalum and at least one element selected from the group consisting of nitrogen and oxygen. The reflective mask blank for EUV lithography according to any one of 〔1〕 to 〔5〕. 〔7〕The content of oxygen in the outermost layer is 20 to 60 atomic% with respect to all atoms in the outermost layer. The reflective mask blank for EUV lithography according to 〔6〕. 〔8〕The content of oxygen in the outermost layer is 40 to 50 atomic% with respect to all atoms in the outermost layer. The reflective mask blank for EUV lithography according to 〔6〕 or 〔7〕. 〔9〕When measuring the transmittance of the conductive film for light of 632 nm at three different points, taking the arithmetic mean value of the transmittance at the above three points as the average transmittance of light of 632 nm, and taking the difference between the maximum transmittance and the minimum transmittance among the transmittances at the above three points as the maximum transmittance difference of light of 632 nm, the ratio of the maximum transmittance difference of the conductive film for light of 632 nm to the average transmittance of the conductive film for light of 632 nm is less than 2.0%. The reflective mask blank for EUV lithography according to any one of 〔1〕 to 〔8〕. 〔10〕When measuring the transmittance of the conductive film for light of 1064 nm at three different points, taking the arithmetic mean value of the transmittance at the above three points as the average transmittance of light of 1064 nm, and taking the difference between the maximum transmittance and the minimum transmittance among the transmittances at the above three points as the maximum transmittance difference of light of 1064 nm, the ratio of the maximum transmittance difference of the conductive film for light of 1064 nm to the average transmittance of the conductive film for light of 1064 nm is less than 2.0%. The reflective mask blank for EUV lithography according to any one of 〔1〕 to 〔9〕. 〔11〕An EUV lithography reflective mask having an absorber film pattern formed by patterning the absorber film of the EUV lithography reflective mask blank according to any one of 〔1〕 to 〔10〕. A method for manufacturing a reflective mask for EUV lithography, including the step of patterning the absorber film on the reflective mask blank for EUV lithography according to any one of [1] to

[10] . 〔13〕Form a conductive film on one surface side of the substrate, Form a multilayer reflective film that reflects EUV light on the other surface side of the substrate, A method for manufacturing a reflective mask blank for EUV lithography, comprising forming an absorber film on the side opposite to the substrate side of the multilayer reflective film, The formation of the conductive film is carried out in the presence of nitrogen gas, The pressure during the formation of the conductive film is 0.1 to 0.4 Pa. A method for manufacturing a reflective mask blank for EUV lithography according to any one of [1] to

[10] . 〔14〕 A substrate with a conductive film having a substrate and a conductive film disposed on one surface side of the substrate, wherein the conductive film contains one or more elements selected from the group consisting of tantalum and chromium, the total content of nitrogen and boron contained in the conductive film is more than 33 atomic% based on all the atoms of the conductive film, the film thickness of the conductive film is 20 to 150 nm, the film thickness of the conductive film at the center of the substrate is larger than the film thickness of the conductive film at the end of the substrate, the maximum film thickness difference in the in-plane direction of the conductive film is 0.30 to 1.00 nm. A substrate with a conductive film. 〔15〕The nitrogen content of the conductive film is 35 to 65 atomic% based on all the atoms of the conductive film. A substrate with a conductive film according to

[14] . 〔16〕The boron content of the conductive film is more than 0 atomic% and 35 atomic% or less based on all the atoms of the conductive film. A substrate with a conductive film according to

[14] or

[15] . 〔17〕 The electrical resistivity of the conductive film is 0.05 to 0.35 mΩ·cm. A substrate with a conductive film according to any one of

[14] to

[16] . 〔18〕 〔18〕 The conductive film has a multilayer structure composed of two or more layers, Among the above layers, the outermost layer located at the position farthest from the substrate is a layer containing tantalum and at least one element selected from the group consisting of nitrogen and oxygen. The substrate with a conductive film according to any one of

[14] to

[17] .

[19] The substrate with a conductive film according to

[18] , wherein the oxygen content of the outermost layer is 20 to 60 atomic% with respect to all atoms of the outermost layer.

[20] The substrate with a conductive film according to

[18] , wherein the oxygen content of the outermost layer is 40 to 50 atomic% with respect to all atoms of the outermost layer.

[21] When the transmittance of the conductive film at 632 nm is measured at three different points, the arithmetic mean value of the transmittance at the three points is defined as the average transmittance of the light at 632 nm, and among the transmittances at the three points, the difference between the maximum transmittance and the minimum transmittance is defined as the maximum transmittance difference of the light at 632 nm. The substrate with a conductive film according to any one of

[14] to

[20] , wherein the ratio of the maximum transmittance difference of the conductive film at 632 nm to the average transmittance of the conductive film at 632 nm is less than 2.0%.

[22] When the transmittance of the conductive film at 1064 nm is measured at three different points, the arithmetic mean value of the transmittance at the three points is defined as the average transmittance of the light at 1064 nm, and among the transmittances at the three points, the difference between the maximum transmittance and the minimum transmittance is defined as the maximum transmittance difference of the light at 1064 nm. The substrate with a conductive film according to any one of

[14] to

[21] , wherein the ratio of the maximum transmittance difference of the conductive film at 1064 nm to the average transmittance of the conductive film at 1064 nm is less than 2.0%. [Advantages of the Invention]

[0011] According to the present invention, it is possible to provide a reflective mask blank having a conductive film with a small distribution of transmittances of light at 632 nm and 1064 nm and excellent flatness. Further, according to the present invention, it is possible to provide a method for manufacturing a reflective mask blank, as well as a reflective mask and a method for manufacturing a reflective mask. [Brief Description of the Drawings]

[0012]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0014] The meaning of each description in this specification is shown. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, tantalum, rhenium, iridium, and platinum may be represented by their corresponding element symbols (such as B, C, N, O, Si, Ti, Cr, Zr, Nb, Mo, Ru, Rh, Pd, Ta, Re, Ir, and Pt).

[0015] <Reflective mask blank> The reflective mask blank of the present invention includes a substrate, a conductive film disposed on one surface side of the substrate, a multilayer reflective film that reflects EUV light disposed on the other surface side of the substrate, and an absorber film disposed on the side opposite to the substrate side of the multilayer reflective film. In the reflective mask blank of the present invention, the conductive film contains one or more elements selected from the group consisting of tantalum and chromium, and the total content of nitrogen (N) and boron (B) contained in the conductive film is more than 33 atomic% with respect to all the atoms of the conductive film. Further, in the reflective mask blank of the present invention, the film thickness of the conductive film is 20 to 150 nm, the film thickness of the conductive film at the center of the substrate is larger than the film thickness of the conductive film at the end of the substrate, and the maximum film thickness difference in the in-plane direction of the conductive film is 0.30 to 0.80 nm. The reflective mask blank of the present invention will be described with reference to the drawings.

[0016] FIG. 1 is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. The reflective mask blank 10 shown in FIG. 1 has a conductive film 22, a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in this order. The conductive film 22 contains the above-described predetermined elements and satisfies the above-described conditions regarding the content. Further, the conductive film 22 satisfies the above-described predetermined conditions regarding the film thickness. Note that the protective film 16 shown in FIG. 1 may be omitted. Further, the reflective mask blank 10 may have a hard mask film, which will be described later, on the side opposite to the substrate 12 side of the absorber film 18.

[0017] Although the mechanism by which the reflective mask blank of the present invention has a conductive film with a small transmittance distribution of light at 632 nm and 1064 nm and excellent flatness is not necessarily clear, the present inventors presume as follows. The conductive film of the reflective mask blank of the present invention has a total content of N and B exceeding 33 atomic% with respect to all atoms of the conductive film and a film thickness of a predetermined thickness, so that light of 632 nm and 1064 nm can be transmitted. Here, the inventors of the present invention have found that when the film thickness of the conductive film at the center of the substrate is made larger than the film thickness of the conductive film at the edge of the substrate and the maximum film thickness difference is within the above range, the distribution of the transmittance of light of 632 nm and 1064 nm of the conductive film becomes smaller. Also, when the total content of N and B exceeds 33 atomic% with respect to all atoms of the conductive film, it is considered that the stress generated by the conductive film tends to increase. Then, it is considered that it is easy to balance the stress generated by the multilayer reflective film disposed on the other surface side of the substrate and the absorber film, and a reflective mask blank excellent in flatness can be obtained.

[0018] Hereinafter, the configuration of the reflective mask blank of the present invention will be described.

[0019] [Substrate] The substrate included in the reflective mask blank of the present invention preferably has a small coefficient of thermal expansion. When the coefficient of thermal expansion of the substrate is small, it is possible to suppress the occurrence of distortion in the absorber film pattern due to heat during exposure with EUV light. The coefficient of thermal expansion of the substrate is preferably 0 ± 1.0×10 -7 / °C at 20°C, and more preferably 0 ± 0.3×10 -7 / °C. Examples of materials having a small coefficient of thermal expansion include, but are not limited to, SiO2-TiO2-based glass, and substrates such as crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, and metals can also be used. For SiO2-TiO2-based glass, it is preferable to use quartz glass containing 90 to 95% by mass of SiO2 and 5 to 10% by mass of TiO2. When the content of TiO2 is 5 to 10% by mass, the linear expansion coefficient near room temperature is substantially zero, and almost no dimensional change occurs near room temperature. Note that the SiO2-TiO2-based glass may contain trace components other than SiO2 and TiO2.

[0020] The surface of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first main surface") preferably has high surface smoothness. The surface smoothness of the first main surface can be evaluated by surface roughness. The surface roughness of the first main surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. The surface roughness can be measured with an atomic force microscope, and the surface roughness is described as the root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to have a predetermined flatness in terms of enhancing the pattern transfer accuracy and positional accuracy of the reflective mask obtained using the reflective mask blank. The substrate preferably has a flatness of 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less in a predetermined region (for example, a region of 132 mm × 132 mm) of the first main surface. The flatness can be measured with a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate are appropriately determined according to the design values of the mask and the like. For example, the outer shape is a 6-inch (152 mm) square, and the thickness is 0.25 inch (6.3 mm), etc. The substrate is often rectangular (rectangular) or square. Furthermore, the substrate preferably has high rigidity in terms of preventing deformation due to the film stress of the film (multilayer reflective film, absorber film, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or more.

[0021] [Multilayer Reflective Film] The multilayer reflective film included in the reflective mask blank of the present invention is not particularly limited as long as it has the desired characteristics as the reflective film of the EUV mask blank. The multilayer reflective film preferably has a high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum value of the reflectivity of EUV light near a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% or more. Also, even when a protective film is laminated on the multilayer reflective film, similarly, the maximum value of the reflectivity of EUV light near a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% or more.

[0022] Since a multilayer reflective film can achieve a high reflectivity of EUV light, a multilayer reflective film in which a high refractive index layer that usually exhibits a high refractive index with respect to EUV light and a low refractive index layer that exhibits a low refractive index with respect to EUV light are alternately laminated a plurality of times is generally used. The multilayer reflective film may be laminated with a plurality of cycles with a laminated structure in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate side as one cycle, or may be laminated with a plurality of cycles with a laminated structure in which a low refractive index layer and a high refractive index layer are laminated in this order as one cycle. As the high refractive index layer, a layer containing Si can be used. As a material containing Si, in addition to single crystal Si, a Si compound containing one or more selected from the group consisting of B, C, N, and O can be used for Si. By using a high refractive index layer containing Si, a reflective mask excellent in the reflectivity of EUV light can be obtained. As the low refractive index layer, a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof can be used. Si is widely used for the high refractive index layer, and Mo is widely used for the low refractive index layer. That is, the Mo / Si multilayer reflective film is the most common. However, the multilayer reflective film is not limited to this, and Ru / Si multilayer reflective films, Mo / Be multilayer reflective films, Mo compound / Si compound multilayer reflective films, Si / Mo / Ru multilayer reflective films, Si / Mo / Ru / Mo multilayer reflective films, Si / Ru / Mo multilayer reflective films, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0023] The film thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layer can be appropriately selected according to the film material used and the reflectivity of EUV light required for the reflective layer. Taking the Mo / Si multilayer reflective film as an example, in order to obtain a multilayer reflective film with a maximum reflectivity of EUV light of 60% or more, a Mo film with a film thickness of 2.3 ± 0.1 nm and a Si film with a film thickness of 4.5 ± 0.1 nm may be laminated so that the number of repeating units is 30 to 60.

[0024] Each layer constituting the multilayer reflective film can be formed to a desired thickness using a known film-forming method such as magnetron sputtering method or ion beam sputtering method. For example, when producing a multilayer reflective film using the ion beam sputtering method, ion particles are supplied from an ion source to a target of a high refractive index material and a target of a low refractive index material. When the multilayer reflective film is a Mo / Si multilayer reflective film, by the ion beam sputtering method, for example, first, a Si layer with a predetermined film thickness is formed on a substrate using a Si target. Then, a Mo layer with a predetermined film thickness is formed using a Mo target. By stacking 30 to 60 cycles with this Si layer and Mo layer as one cycle, a Mo / Si multilayer reflective film is formed.

[0025] [Protective film] The reflective mask blank of the present invention may have a protective film between the multilayer reflective film and the absorber film. The protective film is provided for the purpose of protecting the multilayer reflective film so that the multilayer reflective film is not damaged by the etching process when patterning the absorber film by an etching process (usually a dry etching process). Examples of materials that can achieve the above object include materials containing at least one element selected from the group consisting of Ru and Rh. That is, the protective film preferably contains at least one element selected from the group consisting of Ru and Rh. More specifically, as the above materials, Ru metal alone, a Ru alloy containing Ru and one or more metals selected from the group consisting of Si, Ti, Nb, Rh, and Zr, and Rh metal alone, Rh and one or more metals selected from the group consisting of Si, Ti, Nb, Ru, Ta, and Zr, Rh-based materials such as a Rh alloy, a Rh-containing nitride containing the above Rh alloy and nitrogen, and a Rh-containing oxynitride containing the above Rh alloy, nitrogen, and oxygen can be mentioned. Also, examples of materials that can achieve the above object include Al, nitrides containing these metals and nitrogen, and Al2O3, etc. Among these, as the material capable of achieving the above object, a single Ru metal, a Ru alloy, a single Rh metal, or a Rh alloy is preferable. As the Ru alloy, a Ru-Si alloy is preferable, and as the Rh alloy, a Rh-Si alloy is preferable.

[0026] The film thickness of the protective film is not particularly limited as long as it can function as a protective film. From the viewpoint of maintaining the reflectance of the EUV light reflected by the multilayer reflective film, the film thickness of the protective film is preferably 1 to 10 nm, more preferably 1.5 to 6 nm, and even more preferably 2 to 5 nm. It is also preferable that the material of the protective film is a single Ru metal, a Ru alloy, a single Rh metal, or a Rh alloy, and the film thickness of the protective film is the above-preferred film thickness.

[0027] The protective film may be a film composed of a single layer or a multilayer film composed of a plurality of layers. When the protective film is a multilayer film, each layer constituting the multilayer film is preferably made of the above-preferred material. Further, when the protective film is a multilayer film, it is also preferable that the total film thickness of the multilayer film is the film thickness of the protective film in the above-preferred range. When the protective film is a multilayer film, it is preferable that the layer disposed closest to the absorber film among the multilayer films contains Rh. Further, when the layer disposed closest to the absorber film among the layers constituting the multilayer film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0028] The protective film can be formed using a known film-forming method such as a DC sputtering method, a magnetron sputtering method, or an ion beam sputtering method. When forming a Ru film by the magnetron sputtering method, it is preferable to use a Ru target as the target and Ar gas as the sputtering gas for film formation. Further, when forming a Rh film by the magnetron sputtering method, it is preferable to use a Rh target as the target and Ar gas as the sputtering gas for film formation.

[0029] [Absorber film] The absorber film of the reflective mask blank of the present invention is required to have a high contrast between the EUV light reflected by the multilayer reflective film and the EUV light in the absorber film when the absorber film is patterned. The patterned absorber film (absorber film pattern) may absorb EUV light and function as a binary mask, or may function as a phase shift mask that reflects EUV light and interferes with the EUV light from the multilayer reflective film to generate a contrast.

[0030] When the absorber film pattern is used as a binary mask, the absorber film needs to absorb EUV light and have a low reflectivity of EUV light. Specifically, the maximum value of the reflectivity of EUV light near a wavelength of 13.5 nm when EUV light is irradiated on the surface of the absorber film is desirably 2% or less. The absorber film may contain one or more components selected from the group consisting of O, N, B, Hf, and H in addition to one or more metals selected from the group consisting of Ta, Ti, Sn, and Cr. Among these, the absorber film preferably contains Ta and contains N or B. By containing N or B, the crystal state of the absorber film can be made into an amorphous or microcrystalline structure. The crystal state of the absorber film is preferably amorphous. This can improve the smoothness and flatness of the absorber film. Further, when the smoothness and flatness of the absorber film are increased, the edge roughness of the absorber film pattern becomes small, and the dimensional accuracy of the absorber film pattern can be increased. When the absorber film pattern is used as a binary mask, the film thickness of the absorber film is preferably 40 to 70 nm, and more preferably 50 to 65 nm.

[0031] When the absorber film pattern is used as a phase shift mask, the reflectivity of EUV light of the absorber film is preferably 2% or more. In order to sufficiently obtain the phase shift effect, the reflectivity of the absorber film is preferably 9 to 15%. When the absorber film is used as a phase shift mask, the contrast of the optical image on the wafer is improved and the exposure margin is increased. Examples of materials for forming a phase shift mask include, for example, Ru metal alone, Ru alloy containing one or more metals selected from the group consisting of Ru, Cr, Au, Pt, Re, Hf, Ta, W, Ti, and Si, an alloy of Ta and Nb, an oxide containing Ru alloy or TaNb alloy and oxygen, a nitride containing Ru alloy or TaNb alloy and nitrogen, a oxynitride containing Ru alloy or TaNb alloy and oxygen and nitrogen, a compound containing at least one metal element selected from the group consisting of Pd, Ir, Pt, Ag, Ni, and Co, etc. When using the absorber film pattern as a phase shift mask, the film thickness of the absorber film is preferably 30 to 60 nm, more preferably 35 to 55 nm.

[0032] The absorber film may be a single-layer film or a multilayer film composed of a plurality of films. When the absorber film is a single-layer film, the number of steps in the production of the mask blank can be reduced and the production efficiency can be improved. When the absorber film is a multilayer film, the layer disposed on the side opposite to the protective film side of the absorber film may be an antireflection film when inspecting the absorber film pattern using inspection light (for example, wavelength 193 to 248 nm). Examples of materials for forming the antireflection film include, for example, materials containing Ta and O.

[0033] The absorber film can be formed using known film formation methods such as magnetron sputtering method and ion beam sputtering method. For example, when forming a Ta nitride film as the absorber film using the magnetron sputtering method, a Ta target is used, and a gas containing Ar gas and nitrogen gas is supplied for sputtering to form the absorber film.

[0034] [Conductive film] The reflective mask blank of the present invention has a conductive film on the side of the surface (second main surface) opposite to the first main surface of the substrate. By providing the conductive film, the reflective mask blank can be handled by an electrostatic chuck. Hereinafter, the conductive film of the reflective mask blank of the present invention will be described in detail.

[0035] The conductive film included in the reflective mask blank of the present invention contains one or more elements selected from the group consisting of Ta and Cr. From the viewpoint of obtaining better flatness of the reflective mask blank, it is preferable that the conductive film contains Ta.

[0036] The total content of N and B contained in the conductive film is more than 33 atomic% with respect to all atoms of the conductive film. When the conductive film contains N and B, the content of N is preferably 35 to 65 atomic%, more preferably 40 to 55 atomic% with respect to all atoms of the conductive film. Also, when the conductive film contains N and B, the content of B is preferably more than 0 atomic% and 45 atomic% or less, more preferably 10 to 40 atomic% with respect to all atoms of the conductive film. Also, the content of B may be more than 0 atomic% and 35 atomic% or less with respect to all atoms of the conductive film. The content of each element in the conductive film adopts the value obtained by analysis by X-ray Photoelectron Spectroscopy (XPS). The detailed analysis method of the content follows the method described in the examples in the following section. Also, when the conductive film has a multilayer structure, for example, while performing surface etching from the side opposite to the substrate side of the conductive film using ion sputtering such as argon, analysis is performed to analyze the content of each element in each layer of the conductive film.

[0037] When the conductive film contains N and does not contain B, the content of N is preferably 35 to 65 atomic%, more preferably 40 to 60 atomic%, and even more preferably 45 to 55 atomic% with respect to all atoms of the conductive film.

[0038] When the conductive film does not contain N and contains B, the content of B is preferably more than 33 atomic% and 45 atomic% or less, more preferably 35 to 40 atomic% with respect to all atoms of the conductive film. Also, the content of B may be 35 atomic% or less with respect to all atoms of the conductive film.

[0039] The conductive film may contain elements other than Cr, Ta, N, and B. Examples of elements that the conductive film may contain include C, O, fluorine (F), hydrogen (H), silicon (Si), and Ar.

[0040] Specific materials constituting the conductive film include, for example, CrN, CrON, CrB, CrBN, CrCN, TaN, TaON, TaB, TaBN, TaCN, and CrTaN, etc. Among them, CrN, TaN, or TaBN is preferable. Note that notations such as "CrON" refer to materials containing Cr, O, and N, and the content ratios of these elements are not limited as long as the above requirements are satisfied.

[0041] The conductive film may have a single-layer structure or a multilayer structure. When the conductive film has a multilayer structure, the number of layers constituting the conductive film is not particularly limited, but 4 layers or less is preferable, 3 layers or less is more preferable, and 2 layers is even more preferable. When the conductive film has a multilayer structure, at least one element selected from the group consisting of Ta and Cr is contained in any one of the layers constituting the conductive film. More preferably, at least one element selected from the group consisting of Ta and Cr is contained in all of the layers constituting the conductive film. Note that when the conductive film has a multilayer structure, the conductive film as a whole satisfies the requirements for the contents of N and B described above.

[0042] When the conductive film has a multilayer structure and contains N but does not contain B, the content of N is preferably 35 to 55 atomic% with respect to all atoms of the conductive film, and more preferably 40 to 50 atomic%.

[0043] Here, when the layer located farthest from the substrate among the layers constituting the conductive film is defined as the outermost layer, the outermost layer preferably contains Ta. Furthermore, it is also preferable that the outermost layer is a layer containing Ta and at least one element selected from the group consisting of N and O. When the outermost layer is a layer containing Ta and at least one element selected from the group consisting of N and O, the content of O is preferably 20 to 60 atomic%, more preferably 30 to 50 atomic%, and particularly preferably 40 to 50 atomic% with respect to all atoms of the outermost layer. The outermost layer may not contain N.

[0044] The film thickness of the conductive film is 20 to 150 nm. When the conductive film has a multilayer structure, the total film thickness of each layer constituting the conductive film is 20 to 150 nm. The film thickness of the conductive film is preferably 25 to 120 nm, more preferably 30 to 100 nm in terms of better flatness. The film thickness of the conductive film is determined by X-ray Reflectivity (XRR). The calculation method of the film thickness of the conductive film will be described later.

[0045] When the conductive film has a multilayer structure, the ratio of the film thickness of the layer containing at least one element selected from the group consisting of Ta and Cr and having a total content of N and B in the conductive film exceeding 33 atomic% to the total film thickness of the conductive film is preferably 0.50 or more, more preferably 0.70 or more, and even more preferably 0.80 or more. The upper limit of the above ratio is less than 1.00, and is often 0.95 or less.

[0046] In the reflective mask blank of the present invention, the film thickness of the conductive film at the center of the substrate (hereinafter, also simply referred to as "center") is larger than the film thickness of the conductive film at the edge of the substrate (hereinafter, also simply referred to as "edge"). The center of the substrate refers to, for example, the intersection of the two diagonals when the substrate is rectangular or square. In this specification, the edge of the substrate is defined as follows. When the substrate is rectangular or square, first, in the in-plane direction of the substrate, with the center of the substrate as the origin, an X-axis parallel to one side of the substrate and a Y-axis perpendicular to the X-axis are defined. Next, the distance from the origin to the intersection of the X-axis and one side of the substrate is denoted as Lx, and the distance from the origin to the intersection of the Y-axis and one side of the substrate is denoted as Ly. Here, the edge of the substrate refers to the point that becomes (0.868Lx, 0.868Ly) in the coordinate system described by the X-axis and the Y-axis when the center of the substrate is the origin. Note that the film thickness at the edge may be the film thickness at any position within a perfect circular region with a radius of 0.5 mm centered at the edge. Also, the film thickness at the center of the substrate may be the film thickness at any position within a perfect circular region with a radius of 0.5 mm centered at the center of the substrate. For example, when the substrate is a square with a side length of 152 mm, with the center of the substrate as the intersection of the diagonals and an X-axis parallel to one side and a Y-axis perpendicular to the X-axis defined, the edge of the substrate refers to the point that has moved 66 mm in the X-axis direction and 66 mm in the Y-axis direction from the origin.

[0047] That is, "the film thickness of the conductive film at the center is greater than the film thickness of the conductive film at the edge of the substrate" means that the film thickness of the conductive film at the center is thicker than the film thickness of the conductive film at the edge (the point of the coordinates). For the measurement of the film thickness of the conductive film at the center and the edge by XRR, Rigaku's Smart Lab HTP is used. As the X-ray source, CuKα rays are used, the tube voltage is 40 kV, and the tube current is 30 mA. The attached software (GlobalFit) is used for analysis. Also, in the measurement by XRR, the X-ray is irradiated onto the conductive film so that the center of the X-ray beam coincides with the center or the point at the edge of the substrate for measurement.

[0048] In the above, the center and the edge of the substrate in the case where the substrate is rectangular or square have been described. However, when the substrate is circular, the center of the substrate is the center of the circle. Also, the edge of the substrate is the point that is 0.868 times the radius of the substrate from the center of the substrate in the in-plane direction of the substrate.

[0049] The film thickness of the conductive film described above is determined by the following method. First, using the method described above, determine the center and the end portion. Here, on the line passing through the center and the end portion (the diagonal line of the substrate), let the distance between the center and the end portion be Ld. Here, determine a point where the distance from the center is 33Ld / 66 on the diagonal line toward the end portion. At the above-mentioned point, the center, and the end portion, a total of three points, measure the film thickness of the conductive film according to the above method, and take the arithmetic mean value as the film thickness of the conductive film. Note that the film thickness at the above three points may be the film thickness at any position within a perfect circle region with a radius of 0.5 mm centered on each of the above points. For example, when the substrate is a square with a side length of 152 mm, with the center of the substrate as the intersection of the diagonal lines, and an X-axis parallel to one side and a Y-axis perpendicular to the X-axis are defined, XRR measurements are performed at the points (0,0), (33,33), and (66,66), and the arithmetic mean value is taken as the film thickness of the conductive film. Note that the unit of each numerical value in the above coordinates is mm. When the substrate is a square with a side length of 152 mm, the above three points are arranged as shown in FIG. 2. FIG. 2 is a plan view when the reflective mask blank 10 shown in FIG. 1 is viewed from the conductive film 22 side, and points A to C respectively correspond to the points (0,0) (center), (33,33), and (66,66) (end portion) in order.

[0050] In the reflective mask blank of the present invention, the maximum film thickness difference in the in-plane direction of the conductive film is 0.30 to 0.80 nm. In this specification, the maximum film thickness difference refers to the value obtained by subtracting the minimum film thickness from the maximum film thickness of the conductive film at each point measured when determining the film thickness of the conductive film described above. The maximum film thickness difference is preferably 0.40 to 0.65 nm, and more preferably 0.50 to 0.60 nm, at a point where the distribution of the light transmittance of 632 nm light is likely to be smaller. Also, in the same manner as above, it is preferable that the maximum film thickness difference obtained from (0,0), (-33,33), and (-66,66) is 0.30 to 0.80 nm, and more preferably within the above preferable range. Furthermore, in the same manner as described above, the maximum film thickness difference obtained from (0, 0), (-33, -33), and (-66, -66) is preferably 0.30 to 0.80 nm, and more preferably within the above-preferred range. Furthermore, in the same manner as described above, the maximum film thickness difference obtained from (0, 0), (33, -33), and (66, -66) is preferably 0.30 to 0.80 nm, and more preferably within the above-preferred range.

[0051] The electrical resistivity of the conductive film is preferably 0.35 mΩ·cm or less from the viewpoint of obtaining sufficient holding force when performing electrostatic chucking. The lower limit of the electrical resistivity is often 0.05 mΩ·cm or more. The electrical resistivity of the conductive film is measured by the method shown in the following examples.

[0052] The surface roughness of the surface of the conductive film on the side opposite to the substrate side is preferably 0.60 nm or less, and more preferably 0.50 nm or less. The above surface roughness is often 0.01 nm or more. The surface roughness of the surface of the conductive film on the side opposite to the substrate side is the root mean square roughness Rq, and can be measured in the same manner as the surface roughness of the above substrate. The detailed measurement method of the surface roughness follows the method of the following examples.

[0053] Regarding the transmittance of the conductive film for light of 632 nm, it is preferable to satisfy the following relationship. First, measure the transmittance of light of 632 nm at the above three points, and obtain the average transmittance of light of 632 nm, which is the arithmetic mean value of the transmittances at these three points, and the maximum transmittance difference of light of 632 nm, which is the value obtained by subtracting the minimum transmittance from the maximum transmittance. Here, the ratio of the maximum transmittance difference of light of 632 nm to the average transmittance of light of 632 nm is preferably less than 2.0%, more preferably less than 1.5%, and even more preferably less than 1.2%. The transmittance of the conductive film for light of 632 nm is measured by the following method. First, prepare a substrate with a conductive film formed thereon. If a multilayer reflective film, an absorber film, or the like is formed on the substrate, remove them. Next, at the above three points, from the side where the conductive film is formed, irradiate light in the normal direction of the surface of the conductive film, and calculate the transmittance at 632 nm with a spectrophotometer. The above spectrophotometer uses "V-780" manufactured by JASCO Corporation, and the wavelength range is 175 to 2000 nm.

[0054] Also, regarding the transmittance of the conductive film to light of 1064 nm, it is preferable to satisfy the following relationship. First, measure the transmittance of light of 1064 nm at the above three points, and obtain the average transmittance of light of 1064 nm, which is the arithmetic mean value of the transmittances at those three points, and the maximum transmittance difference of light of 1064 nm, which is the value obtained by subtracting the minimum transmittance from the maximum transmittance. Here, the ratio of the maximum transmittance difference of light of 1064 nm to the average transmittance of light of 1064 nm is preferably less than 2.0%, more preferably less than 1.5%, and even more preferably less than 1.2%. The measurement of the transmittance of the conductive film to light of 1064 nm can be carried out in the same manner as the measurement of the transmittance of light of 632 nm.

[0055] The formation method of the conductive film is not particularly limited as long as it can form a conductive film that satisfies the above-mentioned requirements, and known film formation methods can be applied. For example, a conductive film can be formed by a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or the like. In addition, the manufacturing method of the reflective mask blank described later can be preferably applied.

[0056] [Other films] The reflective mask blank of the present invention may have other films. Examples of the other films include a hard mask film. The hard mask film is preferably disposed on the side opposite to the substrate side of the absorber film. As the hard mask film, it is preferable to use a material highly resistant to dry etching, such as a Cr-based film and a Si-based film. Examples of the Cr-based film include materials containing Cr and one or more elements selected from the group consisting of Cr and O, N, C, and H. Specifically, CrO, CrN, etc. can be mentioned. Examples of the Si-based film include materials containing Si and one or more selected from the group consisting of Si and O, N, C, and H. Specifically, SiO2, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON, etc. can be mentioned. When a hard mask film is formed on the absorber film, dry etching can be carried out even if the minimum line width of the absorber film pattern becomes small. Therefore, it is effective for miniaturization of the absorber film pattern.

[0057] <Method for manufacturing a reflective mask blank> As one embodiment of the method for manufacturing a reflective mask blank of the present invention, there is provided a method for manufacturing a reflective mask blank, which includes forming a conductive film on one surface side of a substrate, forming a multilayer reflective film that reflects EUV light on the other surface side of the substrate, and forming an absorber film on the side of the multilayer reflective film opposite to the substrate side. Here, the formation of the conductive film is carried out in the presence of one or more gases selected from the group consisting of nitrogen gas and oxygen gas, and the pressure during the formation of the conductive film is 0.1 to 0.4 Pa. Note that forming a conductive film in the presence of nitrogen gas means that nitrogen gas (N2 gas) is included in the atmosphere for forming the conductive film. Note that forming a conductive film in the presence of oxygen gas means that oxygen gas (O2 gas) is included in the atmosphere for forming the conductive film. Note that forming a conductive film in the presence of nitrogen gas and oxygen gas means that nitrogen gas (N2 gas) and oxygen gas (O2 gas) are included in the atmosphere for forming the conductive film. Also, the pressure during the formation of the conductive film being within the above pressure range means that the pressure in the space (for example, a chamber) for forming the conductive film is within the above pressure range.

[0058] The formation of the conductive film is preferably carried out by a sputtering method, and more preferably by a magnetron sputtering method. The formation of the conductive film is carried out by controlling the pressure in the space where the conductive film is formed to 0.1 to 0.4 Pa. When forming the conductive film by a sputtering method (preferably a magnetron sputtering method), the pressure in the chamber where sputtering is carried out is controlled within the above range to form the conductive film. The pressure control is carried out, for example, by evacuating the inside of the chamber with a vacuum pump connected to the chamber while supplying gas from a gas supply means connected to the chamber while controlling the flow rate. At this time, a vacuum gauge is arranged in the chamber, and the gas flow rate may be adjusted while monitoring the pressure in the chamber with the vacuum gauge. In the above method, the gas to be supplied is preferably a mixed gas containing a noble gas and one or more gases selected from the group consisting of nitrogen gas and oxygen gas. Examples of the noble gas include Ne gas, Ar gas, Kr gas, and Xe gas, and Ar gas is preferred. The content of nitrogen gas in the mixed gas is preferably 5 to 50% by volume, more preferably 10 to 30% by volume, based on the total volume of the mixed gas.

[0059] When forming the conductive film by a sputtering method (preferably a magnetron sputtering method), the film formation rate is preferably 0.5 to 20 nm / min, more preferably 1 to 20 nm / min, still more preferably 2 to 10 nm / min, and particularly preferably 2 to 4.7 nm / min. When forming the conductive film by the magnetron sputtering method, the input power is preferably 500 to 1500 W, more preferably 700 to 1200 W.

[0060] When the conductive film has a multilayer structure composed of two or more layers, after forming the first layer on the substrate side, subsequently, the second and subsequent layers are formed under the same film formation conditions as the first layer.

[0061] The formation methods of the multilayer reflective film and the absorber film are as described above, and known methods can be applied.

[0062] <Method for Manufacturing Reflective Mask and Reflective Mask> The reflective mask of the present invention is obtained by patterning the absorber film included in the reflective mask blank of the present invention. An example of the method for manufacturing a reflective mask will be described with reference to FIG. 3.

[0063] FIG. 3(a) shows a state in which a resist pattern 40 is formed on a reflective mask blank having a conductive film 22, a substrate 12, a multilayer reflective film 14, a protective film 16, an absorber film 18, and a hard mask film 20 in this order. As the method for forming the resist pattern 40, a known method can be used. For example, a resist is applied on the hard mask film 20 of the reflective mask blank, and exposure and development are performed to form the resist pattern 40. Note that the resist pattern 40 corresponds to the pattern formed on the wafer using the reflective mask. Thereafter, using the resist pattern 40 in FIG. 3(a) as a mask, the absorber film 18 is etched and patterned, and the resist pattern 40 is removed to obtain a laminate having an absorber film pattern 18pt shown in FIG. 3(b). Next, as shown in FIG. 3(c), a resist pattern 42 corresponding to the frame of the exposure region is formed on the laminate in FIG. 3(b), and dry etching is performed using the resist pattern 42 in FIG. 3(c) as a mask. The dry etching is carried out until the substrate 12 is reached. After the dry etching, the resist pattern 42 is removed to obtain the reflective mask shown in FIG. 3(d).

[0064] The reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention can be suitably applied as a reflective mask used for exposure with EUV light.

Example

[0065] The present invention will be described in more detail based on the following examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the examples shown below. Note that Examples 1, 2, and 5 described below are examples, and Examples 3, 4, 6, and 7 are comparative examples.

[0066] <Example 1> First, the procedure for obtaining the substrate with a conductive film of Example 1 will be described.

[0067] [Substrate] First, as the substrate, a SiO2-TiO2-based glass substrate (outer shape: 6 inches (152 mm) square, thickness: 6.3 mm) was prepared. The thermal expansion coefficient of this glass substrate at 20 °C was 0.02×10 -7 / °C, the Young's modulus was 67 GPa, the Poisson's ratio was 0.17, and the specific stiffness was 3.07×10 7 m 2 / s 2 . The quality assurance area of the first main surface of the substrate had a root mean square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less by polishing.

[0068] [Conductive film] A TaN film (conductive film) was formed on one surface of the above substrate by magnetron sputtering. The film formation conditions of TaN are as follows. Target: Ta metal target Sputtering gas: Mixed gas of Ar gas and N2 gas (Ar gas: 81 vol%, N2 gas: 19 vol%) Film formation pressure: 0.23 Pa Input power: 1000 W Film formation rate: 4.62 nm / min

[0069] The substrate with a conductive film of Example 1 was obtained by the above procedure. The obtained substrate with a conductive film was measured by the following procedure.

[0070] [Measurement] (Conductive film composition) The composition of the formed conductive film was analyzed by XPS. As the XPS, "PHI 5000 VersaProbe" manufactured by ULVAC-PHI, Inc. was used. The composition obtained by the analysis is shown in the table in the subsequent section. Note that elements other than those shown in the table in the subsequent section were the elements used for the above target.

[0071] (Film thickness) The film thickness of the conductive film was measured by the method described above. That is, with the intersection of the diagonals of the substrate as the center, XRR measurements were performed at each of the points (0,0), (33,33), and (66,66), and the film thickness (arithmetic mean value) of the conductive film, the film thickness of the conductive film at the center of the substrate, the film thickness of the conductive film at the edge of the substrate, and the maximum film thickness difference in the in-plane direction of the conductive film were calculated.

[0072] <Examples 2 to 7> A substrate with a conductive film was obtained in the same manner as in Example 1, except that the film formation conditions were changed as shown in the table in the subsequent section. The measurement results are shown in the table in the subsequent section. In Examples 2 and 5, first, Conductive Film 1 was formed, and then, subsequently, Conductive Film 2 was formed. For the composition of Conductive Film 1, measurement was performed after removing Conductive Film 2 by sputtering with argon ions for the region where measurement by XPS was to be performed.

[0073] <Evaluation method and evaluation criteria> For each obtained substrate with a conductive film, the transmittance distribution of light with a wavelength of 632 nm, flatness, electrical resistivity of the conductive film, and surface roughness of the conductive film were evaluated. The following shows each evaluation method and each evaluation criterion.

[0074] [Transmittance distribution] The transmittance distribution at 632 nm and the transmittance distribution at 1064 nm were measured by the method described above. That is, for the above three points where the film thickness was measured, the transmittance at each wavelength was measured with a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation), and the average transmittance at each wavelength and the maximum transmittance difference, which is the value obtained by subtracting the minimum transmittance from the maximum transmittance, were determined. The transmittance distribution at each wavelength was evaluated based on the following criteria from the ratio of the maximum transmittance difference to the average transmittance obtained. The results are shown in the table in the subsequent section. A: The ratio of the maximum transmittance difference to the average transmittance at 632 nm is less than 2.0%, and the ratio of the maximum transmittance difference to the average transmittance at 1064 nm is less than 2.0%. B: It does not meet the requirements of A above.

[0075] [Flatness] The flatness of the substrate with a conductive film was evaluated by the following procedure. The flatness of the substrate with a conductive film was measured using a flatness measuring machine manufactured by Fujinon Corporation. From the obtained flatness values, the flatness was evaluated according to the following criteria. The results are shown in the table in the following section. A: The flatness is 0.4 μm or more B: The flatness is less than 0.4 μm Note that the fact that the flatness of the substrate with a conductive film meets the criterion A above corresponds to the substrate with a conductive film being warped. When the substrate with a conductive film is warped, when forming films such as a multilayer reflective film and an absorber film on the side opposite to the conductive film side of the substrate using the substrate with a conductive film, the balance with the stress generated by the formation of these films is achieved, and the flatness of the obtained reflective mask blank becomes high.

[0076] [Electrical Resistivity] The electrical resistivity of the conductive film on the substrate with a conductive film was evaluated by the following procedure. Note that the film thickness of the conductive film obtained by the above procedure was used for the calculation of the electrical resistivity. The results are shown in the table in the following section. · Evaluation apparatus: Loresta - GX, manufactured by Nitto Seiko Analytic Co., Ltd. · Number of measurement points: 3 points · Measurement range: 149 mm × 149 mm

[0077] [Surface Roughness] The surface roughness (root mean square roughness Rq) of the surface on the side opposite to the substrate side of the conductive film was measured. The surface roughness was calculated by analyzing the measurement results using an atomic force microscope manufactured by SII Corporation. Note that the measurement range was set to a range of 2 μm × 2 μm. The results are shown in the table in the following section.

[0078] [Results] The configuration of each substrate with a conductive film, each measurement result, and the evaluation result are shown in a table. In the table, for the column of "Center film thickness > End film thickness", when the film thickness of the conductive film at the center is thicker than the film thickness of the conductive film at the end, it is described as "A", and when it is not, it is described as "B".

[0079]

Table 1

[0080] As shown in Table 1, when the predetermined conditions regarding the above-described conductive film are satisfied, it was confirmed that the transmittance distribution of the conductive film becomes small. Further, when the predetermined conditions regarding the above-described conductive film are satisfied, since the flatness of the substrate with the conductive film becomes low, the flatness of the obtained reflective mask blank becomes high. On the other hand, from the results of Example 3, it was confirmed that when the film thickness of the conductive film at the center of the substrate is not greater than the film thickness of the conductive film at the end of the substrate, the transmittance distribution of the conductive film does not become small. From the results of Example 4, since it was confirmed that when the total content of nitrogen and boron contained in the conductive film is 33% or less with respect to all atoms of the conductive film, the flatness of the substrate with the conductive film becomes high, the flatness of the obtained reflective mask blank does not become high.

[0081] In addition, when a multilayer reflective film and an absorber film are formed on the side opposite to the conductive film side of the substrate with the conductive film obtained by the above procedure by the above method, the reflective mask blank of the present invention is obtained.

[0082] The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2023-169979 filed on September 29, 2023, and Japanese Patent Application No. 2024-009653 filed on January 25, 2024, are hereby incorporated by reference and made a part of the disclosure of the present invention.

Explanation of reference numerals

[0083] 10 Reflective mask blank 12 Substrate 14 Multilayer reflective film 16 Protective film 18 Absorber film 18pt Absorber film pattern 22 Conductive film 40, 42 Resist pattern

Claims

1. A substrate; A conductive film disposed on one surface side of the substrate; a multilayer reflective film that reflects EUV light and is disposed on the other surface side of the substrate; an absorber film disposed on the opposite side of the multilayer reflective film from the substrate side, the conductive film contains tantalum; the conductive film contains nitrogen but does not contain boron, the nitrogen content being 35 to 65 atomic % relative to all atoms in the conductive film; The conductive film has a thickness of 20 to 150 nm, a thickness of the conductive film at a center of the substrate is greater than a thickness of the conductive film at an end of the substrate; A reflective mask blank for EUV lithography, wherein the conductive film has a maximum film thickness difference in an in-plane direction of 0.30 to 1.00 nm.

2. 2. The reflective mask blank for EUV lithography according to claim 1, wherein the conductive film has an electrical resistivity of 0.05 to 0.35 mΩ·cm.

3. 3. The reflective mask blank for EUV lithography according to claim 1, wherein the surface of said conductive film opposite to said substrate has a surface roughness of 0.60 nm or less.

4. the conductive film has a multilayer structure consisting of two or more layers, 3. The reflective mask blank for EUV lithography according to claim 1, wherein among the layers, an outermost layer located farthest from the substrate is a layer containing tantalum and one or more elements selected from the group consisting of nitrogen and oxygen.

5. 5. The reflective mask blank for EUV lithography according to claim 4, wherein the oxygen content of the outermost layer is 20 to 60 atomic % based on all atoms in the outermost layer.

6. 5. The reflective mask blank for EUV lithography according to claim 4, wherein the oxygen content of the outermost layer is 40 to 50 atomic % based on all atoms in the outermost layer.

7. The transmittance of the conductive film at 632 nm light is measured at three different points, the arithmetic mean value of the transmittances at the three points is defined as the average transmittance of 632 nm light, and the difference between the maximum transmittance and the minimum transmittance among the transmittances at the three points is defined as the maximum transmittance difference of 632 nm light.

3. The reflective mask blank for EUV lithography according to claim 1, wherein a ratio of the maximum transmittance difference of the conductive film at 632 nm light to the average transmittance of the conductive film at 632 nm light is less than 2.0%.

8. The transmittance of the conductive film at 1064 nm light is measured at three different points, the arithmetic mean value of the transmittances at the three points is defined as the average transmittance of 1064 nm light, and the difference between the maximum transmittance and the minimum transmittance among the transmittances at the three points is defined as the maximum transmittance difference of 1064 nm light.

3. The reflective mask blank for EUV lithography according to claim 1, wherein a ratio of the maximum transmittance difference of the conductive film at 1064 nm light to the average transmittance of the conductive film at 1064 nm light is less than 2.0%.

9. 3. A reflective mask for EUV lithography, comprising an absorber film pattern formed by patterning the absorber film of the reflective mask blank for EUV lithography according to claim 1 or 2.

10. 3. A method for producing a reflective mask for EUV lithography, comprising the step of patterning the absorber film of the reflective mask blank for EUV lithography according to claim 1 or 2.

11. A conductive film is formed on one side of a substrate; forming a multilayer reflective film that reflects EUV light on the other surface side of the substrate; A method for producing a reflective mask blank for EUV lithography, comprising forming an absorber film on a side of the multilayer reflective film opposite to a side of the substrate, the method comprising: The formation of the conductive film is carried out in the presence of nitrogen gas; 3. The method for producing a reflective mask blank for EUV lithography according to claim 1, wherein the conductive film is formed under a pressure of 0.1 to 0.4 Pa.

12. A substrate; A substrate with a conductive film, the substrate having a conductive film disposed on one surface side of the substrate, the conductive film contains tantalum; the conductive film contains nitrogen but does not contain boron, the nitrogen content being 35 to 65 atomic % relative to all atoms in the conductive film; The conductive film has a thickness of 20 to 150 nm, a thickness of the conductive film at a center of the substrate is greater than a thickness of the conductive film at an end of the substrate; A substrate with a conductive film for a reflective mask blank, wherein the conductive film has a maximum film thickness difference of 0.30 to 1.00 nm in an in-plane direction.

13. 13. The substrate with a conductive film according to claim 12, wherein the conductive film has an electrical resistivity of 0.05 to 0.35 mΩ·cm.

14. the conductive film has a multilayer structure consisting of two or more layers, 14. The substrate with a conductive film according to claim 12 or 13, wherein among the layers, an outermost layer located farthest from the substrate is a layer containing tantalum and one or more elements selected from the group consisting of nitrogen and oxygen.

15. 15. The substrate with a conductive film according to claim 14, wherein the oxygen content of the outermost layer is 20 to 60 atomic % based on all atoms in the outermost layer.

16. 15. The substrate with a conductive film according to claim 14, wherein the oxygen content of the outermost layer is 40 to 50 atomic % based on all atoms in the outermost layer.

17. The transmittance of the conductive film at 632 nm light is measured at three different points, the arithmetic mean value of the transmittances at the three points is defined as the average transmittance of 632 nm light, and the difference between the maximum transmittance and the minimum transmittance among the transmittances at the three points is defined as the maximum transmittance difference of 632 nm light.

14. The substrate with a conductive film according to claim 12, wherein a ratio of the maximum transmittance difference of the conductive film at 632 nm light to the average transmittance of the conductive film at 632 nm light is less than 2.0%.

18. The transmittance of the conductive film at 1064 nm light is measured at three different points, the arithmetic mean value of the transmittances at the three points is defined as the average transmittance of 1064 nm light, and the difference between the maximum transmittance and the minimum transmittance among the transmittances at the three points is defined as the maximum transmittance difference of 1064 nm light.

14. The substrate with a conductive film according to claim 12, wherein a ratio of the maximum transmittance difference of the conductive film at 1064 nm light to the average transmittance of the conductive film at 1064 nm light is less than 2.0%.

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