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

Abstract

To provide a reflection type mask blank in which generation of dielectric breakdown is suppressed when processing by a charged particle beam is performed.SOLUTION: A reflection type mask blank has a substrate, a multilayer reflection film reflecting EUV light, a protective film, and an absorber film in this order, where a single layer structure or an isolation layer of a multilayer structure constituted of layers adjacent to each other is included on the absorber film side of the protective film. In the case where the isolation layer is a single layer structure, the sheet resistance value of the isolation layer is 500kΩ / sq. or more, and the thickness of the isolation layer is 20nm or more. In the case where the isolation layer has a multilayer structure constituted of layers adjacent to each other, the sheet resistance value of each layer constituting the isolation layer is 500kΩ / sq. or more, and the total thickness of the above-described each layer is 20nm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a reflective mask blank, a reflective mask, and a method for manufacturing a reflective mask used in EUV (Extreme Ultraviolet) exposure, which is used in the exposure process for semiconductor manufacturing. [Background technology]

[0002] In recent years, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been investigated for further miniaturization of semiconductor devices.

[0003] In EUV lithography, reflective optics and reflective masks are used for EUV exposure due to the properties of EUV light. A reflective mask consists of a multilayer reflective film that reflects EUV light formed on a substrate, with an absorbent film that absorbs EUV light patterned on the multilayer reflective film. The absorbent film should have a low reflectivity of EUV light, and may be made of a material with high EUV light absorption, or it may be a phase-shift film. A phase-shift film is a film that imparts a phase difference to transmitted EUV light, and the interference between these phase-shifted EUV rays reduces the reflectivity of the EUV light. Furthermore, during the patterning of the absorber film described above, a protective film is often provided between the multilayer reflective film and the absorber film in order to protect the multilayer reflective film.

[0004] A reflective mask can be obtained, for example, by patterning the absorber film of a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, a protective film, and an absorber film in that order. When EUV exposure is performed using a reflective mask, the EUV light incident on the reflective mask from the illumination optical system of the exposure apparatus is reflected in areas without the absorber film (apers), and the reflection is reduced in areas with the absorber film (non-apers). 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 carried out.

[0005] As an example of a reflective mask blank used for the patterning described above, Patent Document 1 discloses an embodiment having a multilayer reflective film and a phase-shift film on a substrate, in which the outermost layer is made of a material containing a silicon compound (SiO2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6968945 [Overview of the project] [Problems that the invention aims to solve]

[0007] In reflective mask blanks or reflective masks, a film located on the opposite side of the absorber film and its protective film may be processed to form alignment marks. In forming these alignment marks, the processing of the film located on the opposite side of the absorber film and its protective film may be carried out by irradiating the film with charged particle beams such as electron beams and ion beams. In addition, in order to correct the mask pattern of reflective masks, the absorber film may be processed using charged particle beams.

[0008] In this case, if the reflective mask blank or reflective mask has an insulating layer, processing with charged particle beams may cause charge to accumulate on the surface of the reflective mask blank or reflective mask due to its insulating properties. As described above, if processing with charged particle beams continues while charge has accumulated, dielectric breakdown may occur due to the potential difference caused by the accumulated charge. Since dielectric breakdown can lead to defects, it is desirable to suppress its occurrence. When the present inventors attempted to process the reflective mask blank described in Patent Document 1 using a charged particle beam, dielectric breakdown sometimes occurred in the insulating layer, indicating the need for improvement.

[0009] This invention has been made in view of the above problems, and aims to provide a reflective mask blank in which dielectric breakdown is suppressed when processed with charged particle beams. Furthermore, the present invention also aims to provide a reflective mask and a method for manufacturing a reflective mask. [Means for solving the problem]

[0010] As a result of diligent research into the above-mentioned problems, the inventors of the present invention discovered that in a reflective mask blank, if the thickness of the insulating layer is greater than a predetermined value, the occurrence of dielectric breakdown is suppressed, and thus completed the present invention.

[0011] In other words, the inventors found that the above problem could be solved by the following configuration. [1] A circuit board and A multilayer reflective film that reflects EUV light, Protective film and, A reflective mask blank having an absorbent membrane in this order, The protective film includes an insulating layer on the absorber film side, which is composed of a single layer or a multilayer structure consisting of adjacent layers. If the insulating layer has a single-layer structure, the sheet resistance of the insulating layer is 500 kΩ / sq. or more, and the thickness of the insulating layer is 20 nm or more. A reflective mask blank in which, in the case where the above insulating layer is a multilayer structure composed of adjacent layers, the sheet resistance value of each layer constituting the above insulating layer is 500 kΩ / sq. or more, and the total thickness of each layer is 20 nm or more. [2] The reflective mask blank according to [1], wherein the side of the protective film opposite to the substrate side includes a non-insulating layer with a sheet resistance of less than 500 kΩ / sq. [3] The reflective mask blank according to [1] or [2], wherein the insulating layer is located on the surface side of the reflective mask blank that is furthest from the substrate. 〔4〕The sheet resistance value of the layer disposed on the surface side farthest from the substrate of the reflective mask blank is 1 kΩ / sq. or less, and the reflective mask blank according to any one of 〔1〕 to 〔3〕. 〔5〕The breakdown voltage between the surface at the position farthest from the substrate of the reflective mask blank and the protective film is 3.00 V or more, and the mask blank according to any one of 〔1〕 to 〔4〕. 〔6〕A reflective mask having an absorber film pattern formed by patterning the absorber film of the reflective mask blank according to any one of 〔1〕 to 〔5〕. 〔7〕A method for manufacturing a reflective mask, including a step of patterning the absorber film of the reflective mask blank according to any one of 〔1〕 to 〔5〕.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a reflective mask blank in which the occurrence of dielectric breakdown is suppressed when processing is performed with a charged particle beam. Further, according to the present invention, it is also possible to provide a reflective mask and a method for manufacturing a reflective mask.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram showing an example of the reflective mask blank of the present invention. [Figure 2] It is a schematic diagram showing an example of the reflective mask blank of the present invention. [Figure 3] It is a schematic diagram showing an example of the reflective mask blank of the present invention. [Figure 4] It is a schematic diagram showing an example of the reflective mask blank of the present invention. [Figure 5] It is a schematic diagram showing an example of the reflective mask blank of the present invention. [Figure 6] It is a schematic diagram showing an example of the manufacturing process of a reflective mask using the reflective mask blank of the present invention.

Embodiments for Carrying Out the Invention

[0014] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0015] The meaning of each term used in this specification is shown below. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In this specification, each element may be represented by its corresponding element symbol.

[0016] <Reflective Mask Blank> The reflective mask blank of the present invention comprises a substrate, a multilayer reflective film that reflects EUV light, a protective film, and an absorber film in this order, wherein the absorber film side of the protective film includes an insulating layer which is either a single layer or a multilayer structure which consists of adjacent layers, and if the insulating layer is a single layer, the sheet resistance of the insulating layer is 500 kΩ / sq. or more and the thickness of the insulating layer is 20 nm or more, and if the insulating layer is a multilayer structure which consists of adjacent layers, the sheet resistance of each layer constituting the insulating layer is 500 kΩ / sq. or more and the total thickness of each layer is 20 nm or more.

[0017] The mechanism by which dielectric breakdown is suppressed when the reflective mask blank of the present invention is processed with charged particle beams is not entirely clear, but the inventors speculate as follows. When processing reflective mask blanks (especially when processing absorber films), charged particle beams are often used. On the other hand, in a reflective mask blank, for example, an insulating layer with a sheet resistance of 500 kΩ / sq. or more may be placed on the absorber film side of the protective film as part of the absorber film layer. If a reflective mask blank has an insulating layer as described above, and processing with a charged particle beam continues, the insulating layer or the layer located on the opposite side of the insulating layer from the substrate side will easily accumulate charges with the same sign as the charges of the charged particles in the charged particle beam. If processing with a charged particle beam continues in the above state, the potential difference between the surface of the insulating layer on the protective film side and the surface of the insulating layer on the opposite side will increase, and if the electric field strength (potential difference / thickness of the insulating layer) exceeds a certain value, dielectric breakdown may occur. In the reflective mask blank of the present invention, the thickness of the insulating layer is 20 nm or more. Therefore, it is considered that the electric field strength in the reflective mask blank of the present invention does not increase significantly with respect to the thickness of the insulating layer. As a result, it is presumed that dielectric breakdown is suppressed when the reflective mask blank of the present invention is processed using charged particle beams.

[0018] The first, second, and third embodiments of the reflective mask blank of the present invention will be described below with reference to the drawings.

[0019] <First embodiment of a reflective mask blank> A first embodiment of the reflective mask blank of the present invention is shown in Figure 1. As shown in Figure 1, the reflective mask blank 10a has a substrate 11, a multilayer reflective film 12, a protective film 13, and an absorber film 14ta in that order. The absorber film 14ta is composed of a first absorber film 14a and a second absorber film 14b from the substrate 11 side, and the second absorber film 14b corresponds to an insulating layer with a sheet resistance of 500 kΩ / sq. or more. The thickness of the second absorber film 14b is 20 nm or more. In the reflective mask blank 10a shown in Figure 1, the thickness of the second absorber film 14b, which is an insulating layer, is 20 nm or more, so the electric field strength does not easily increase, and as a result, the occurrence of dielectric breakdown is suppressed.

[0020] The configuration of the first embodiment of the reflective mask blank of the present invention will be described below.

[0021] [substrate] The substrate of the first embodiment of the reflective mask blank of the present invention preferably has a small coefficient of thermal expansion. A smaller coefficient of thermal expansion of the substrate helps to suppress distortion of the absorber film pattern due to heat during exposure with EUV light. The thermal expansion coefficient of the substrate is 0 ± 1.0 × 10 at 20°C. -7 A temperature of / ℃ is preferred, and 0±0.3×10 -7 / ℃ is preferable. Materials with a low coefficient of thermal expansion include SiO2-TiO2 glass, but are not limited to these; crystallized glass with precipitated β-quartz solid solution, quartz glass, metallic silicon, and metal substrates can also be used. For SiO2-TiO2 glass, it is preferable to use quartz glass containing 90-95% by mass of SiO2 and 5-10% by mass of TiO2. When the TiO2 content is 5-10% by mass, the coefficient of linear expansion at room temperature is approximately zero, and there is almost no dimensional change at room temperature. Note that SiO2-TiO2 glass may also contain trace components other than SiO2 and TiO2.

[0022] The side 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 its 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. Surface roughness can be measured with an atomic force microscope, and the surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to a predetermined flatness, in order to improve the pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. In a predetermined area of ​​the first main surface of the substrate (for example, an area of ​​132 mm × 132 mm), the flatness is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate are determined as appropriate based on the design values ​​of the mask, etc. For example, the outer dimensions may be 6 inches (152 mm) square and the thickness 0.25 inches (6.3 mm). Furthermore, the substrate preferably has high rigidity in order to prevent deformation due to film stress in the film (multilayer reflective film, phase-shift film, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0023] [Multilayer reflective film] The multilayer reflective film of the first embodiment of the reflective mask blank of the present invention is not particularly limited as long as it has the desired properties as a reflective film for an EUV mask blank. The multilayer reflective film preferably has a high reflectivity to EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0024] Because multilayer reflective films can achieve high reflectivity of EUV light, they typically use a multilayer reflective film in which a high refractive index layer, which exhibits a high refractive index for EUV light, and a low refractive index layer, which exhibits a low refractive index for EUV light, are alternately stacked multiple times. The multilayer reflective film may be constructed by stacking a high refractive index layer and a low refractive index layer in that order from the substrate side, with each stacking period comprising multiple cycles, or by stacking a low refractive index layer and a high refractive index layer in that order, with each stacking period comprising multiple cycles. A layer containing Si can be used as the high refractive index layer. In addition to pure Si, Si compounds containing one or more elements selected from the group consisting of B, C, N, and O can be used as the Si-containing material. By using a high refractive index layer containing Si, a reflective mask with excellent EUV light reflectivity 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 in the high refractive index layer, and Mo is widely used in the low refractive index layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to these, 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, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0025] The thickness of each layer constituting a multilayer reflective film and the number of repeating units in each layer can be appropriately selected according to the film material used and the required EUV light reflectivity of the reflective layer. Taking a Mo / Si multilayer reflective film as an example, to create a multilayer reflective film with a maximum EUV light reflectivity of 60% or more, a Mo film with a thickness of 2.3 ± 0.1 nm and a Si film with a thickness of 4.5 ± 0.1 nm should be stacked so that the number of repeating units is between 30 and 60.

[0026] Each layer constituting the multilayer reflective film can be deposited to the desired thickness using known deposition methods such as magnetron sputtering and ion beam sputtering. For example, when fabricating a multilayer reflective film using ion beam sputtering, ion particles are supplied from an ion source to targets made of a high refractive index material and targets made of a low refractive index material. If the multilayer reflective film is a Mo / Si multilayer reflective film, for example, using ion beam sputtering, first a Si layer of a predetermined thickness is deposited on the substrate using a Si target. Then, a Mo layer of a predetermined thickness is deposited using a Mo target. By stacking these Si and Mo layers for 30 to 60 periods, with each period representing one cycle, a Mo / Si multilayer reflective film is formed.

[0027] The layer in contact with the protective film of a multilayer reflective film is preferably made of a material that is resistant to oxidation. The layer made of a material that is resistant to oxidation functions as a cap layer of the multilayer reflective film. An example of a layer made of a material that is resistant to oxidation is a Si layer. When the multilayer reflective film is a Si / Mo multilayer reflective film, if the layer in contact with the protective film is a Si layer, the layer in contact with the protective film functions as a cap layer. In that case, the thickness of the cap layer is preferably 11±2 nm.

[0028] [Protective film] The protective film in the first embodiment of the reflective mask blank of the present invention is provided for the purpose of protecting the multilayer reflective film from damage during the etching process (usually a dry etching process) when a pattern is formed on the absorber film by the etching process. Materials that can achieve the above objective include materials containing at least one element selected from the group consisting of Ru and Rh. In other words, it is preferable that the protective film contains at least one element selected from the group consisting of Ru and Rh. More specifically, the above materials include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Ti, Nb, Rh, and Zr, as well as Rh-based materials such as elemental Rh metal, Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Ti, Nb, Rh, Ta, and Zr, Rh-containing nitrides containing the above Rh alloy and nitrogen, and Rh-containing oxynitrides containing the above Rh alloy, nitrogen, and oxygen. Furthermore, examples of materials that can achieve the above objectives include Al, nitrides containing these metals and nitrogen, and Al2O3. Among these, Ru elemental metal, Ru alloy, Rh elemental metal, or Rh alloy are preferred as materials that can achieve the above objectives. As Ru alloys, Ru-Si alloys are preferred, and as Rh alloys, Rh-Si alloys are preferred.

[0029] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In order to maintain the reflectance of EUV light reflected by the multilayer reflective film, the 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 elemental Ru metal, Ru alloy, elemental Rh metal, or Rh alloy, and that the thickness of the protective film is the preferred thickness described above.

[0030] The protective film may be a single layer or a multilayer film consisting of multiple layers. If the protective film is a multilayer film, it is preferable that each layer constituting the multilayer film is made of the preferred material described above. Furthermore, if the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the preferred range described above.

[0031] The sheet resistance value of the protective film is 1.0 × 10 3 Preferably less than Ω / sq., 7.5 × 10 2 Ω / sq. or less is more preferable, and 5.0 × 10 2 A value of Ω / sq. or less is even more preferable. There is no particular lower limit to the sheet resistance of the protective film, but 1.0 × 10⁻⁶ is preferable. -1 Examples include Ω / sq. and above, and 1.0 × 10⁻⁶. 0 A value of Ω / sq. or higher is preferable. The sheet resistance can be measured by contacting the measuring terminals with the protective film using the four-probe method. More specifically, the sheet resistance can be measured with a surface resistivity meter (Loresta GX MCP-T700, manufactured by Nitto Seiko Analytech Co., Ltd.). The sheet resistance of the protective film may be measured, for example, by exposing the protective film on a reflective mask blank using a method such as etching. Alternatively, the sheet resistance of the protective film may be measured by analyzing the composition and thickness of the protective film using a known analytical method (e.g., transmission scanning electron microscope-energy dispersive X-ray spectroscopy), and then preparing a sample with the same composition and thickness on another substrate (e.g., an insulating substrate), or by preparing a sample on another substrate (e.g., an insulating substrate) under the same conditions as the protective film, and then measuring it. The sheet resistance of the protective film may also be measured using a laminate in an intermediate state during the manufacturing of the reflective mask blank, i.e., a sample in which a substrate, a multilayer reflective film, and a protective film have been formed. According to the method described above, similar sheet resistance values ​​can be obtained.

[0032] The protective film can be deposited using known deposition methods such as magnetron sputtering and ion beam sputtering. When depositing a Ru film by magnetron sputtering, it is preferable to use a Ru target as the target and Ar gas as the sputtering gas.

[0033] [Absorbing membrane] In the first embodiment of the reflective mask blank of the present invention, the absorber film (first absorber film and second absorber film) is comprised of an insulating layer, the second absorber film having a sheet resistance of 500 kΩ / sq. or more. The thickness of the second absorber film is 20 nm or more. The absorber films (first absorber film and second absorber film) are required to have a high contrast between the EUV light reflected by the multilayer reflective film and the EUV light reflected by the absorber film when the absorber films are patterned. A patterned absorber film (absorber film pattern) may function as a binary mask by absorbing EUV light, or it may function as a phase-shift mask that reflects EUV light while interfering with EUV light from a multilayer reflective film to produce contrast. Furthermore, absorber films can also include films with so-called anti-reflective properties. In other words, if the absorber film is a multilayer film (a multi-layered absorber film), the layer located on the opposite side of the absorber film from the protective film side may be an anti-reflective film used when inspecting the absorber film pattern using inspection light (for example, wavelength 193-248 nm).

[0034] When using an absorber film pattern as a binary mask, the absorber film must absorb EUV light and have a low reflectivity of EUV light. Specifically, when EUV light is irradiated onto the surface of the absorber film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 2% or less. The absorber membranes (first absorber membrane and second absorber membrane) preferably contain one or more elements selected from the group consisting of Ta, Ti, Sn, and Cr, and one or more elements selected from the group consisting of O, N, B, Hf, and H. Among these, the inclusion of N or B is preferable. The inclusion of N or B allows the crystalline state of the absorber membrane to be amorphous or microcrystalline. When using an absorber membrane pattern as a binary mask, the thickness of the absorber membrane is preferably 40 to 70 nm, and more preferably 50 to 65 nm. However, in the first embodiment, the thickness of the second absorber membrane is set to 20 nm or more.

[0035] When using an absorber film pattern as a phase shift mask, the EUV light reflectivity of the absorber film is preferably 2% or higher. To obtain a sufficient phase shift effect, the EUV light reflectivity of the absorber film is preferably 9-15%. Using an absorber film as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. Examples of materials used to form a phase shift mask include materials containing one or more elements selected from the group consisting of Cr, Nb, Ru, Ta, Re, Ir, Ag, Os, Au, Pd, and Pt. The absorbent membrane preferably comprises a first layer containing a first element selected from the group consisting of Ru, Re, Ir, Ag, Os, Au, Pd, and Pt, and a second layer containing a second element selected from the group consisting of Nb, Ta, and Cr. The first and second layers also preferably contain at least one element selected from the group consisting of N, O, B, Si, and C. It is also preferable that the first layer corresponds to the first absorbent membrane and the second layer corresponds to the second absorbent membrane. Examples of materials for forming a phase shift mask include the element in its elemental form, alloys containing the element, oxides of the element, nitrides of the element, oxynitrides of the element, borides of the element, silicides of the element, and carbides of the element, as well as composite oxides containing one or more of the element, composite nitrides containing one or more of the element, composite oxynitrides containing one or more of the element, composite borides containing one or more of the element, composite silicides containing one or more of the element, and composite carbides containing one or more of the element. For example, examples of materials used to form a phase shift mask include elemental Ru metal, Ru nitride, Ru oxynitride, Ta nitride, Ta oxynitride, Ru alloys containing Ru and one or more metals selected from the group consisting of Cr, Au, Pt, Re, Hf, Ti, and Si, alloys of Ta and Nb, oxides containing Ru alloy or TaNb alloy and oxygen, nitrides containing Ru alloy or TaNb alloy and nitrogen, and oxynitrides containing Ru alloy or TaNb alloy, oxygen, and nitrogen. However, the material of the phase shift mask that forms the layer in contact with the protective film is selected to be different from the material that forms the protective film. When using an absorber membrane pattern as a phase shift mask, the thickness of the absorber membrane is preferably 30 to 60 nm, and more preferably 35 to 55 nm. However, in the first embodiment, the thickness of the second absorber membrane is set to 20 nm or more.

[0036] The crystalline state of the absorber membrane is preferably amorphous. This improves the smoothness and flatness of the absorber membrane. Furthermore, higher smoothness and flatness of the absorber membrane reduce the edge roughness of the absorber membrane pattern, thereby improving the dimensional accuracy of the absorber membrane pattern.

[0037] Absorber films can be formed using known film deposition methods such as magnetron sputtering and ion beam sputtering. For example, when forming a Ru oxide film as an absorber film using magnetron sputtering, a Ru target is used, and sputtering is performed by supplying a gas containing Ar gas and oxygen gas to deposit the absorber film.

[0038] In FIG. 1, the absorber film 14ta is a two-layer structure of a first absorber film 14a and a second absorber film 14b. As described above, the second absorber film 14b is a layer having a sheet resistance value of 500 kΩ / sq. or more. That is, the second absorber film 14b functions as an absorber film and corresponds to an insulating layer having a sheet resistance value of a predetermined value or more. The sheet resistance value can be measured by the same method as the method for measuring the sheet resistance value of the protective film. Examples of the material constituting the second absorber film 14b include materials containing the second element and an element selected from the group consisting of O and B. More specifically, Ta oxide, Ta oxynitride, Ta boride, Ta borate, Cr oxide, Cr oxynitride, and Cr borate can be mentioned.

[0039] The sheet resistance value of the second absorber film 14 is 500 kΩ / sq. or more, preferably 1000 kΩ / sq. or more. The upper limit is not particularly limited, but preferably 250 GΩ / sq. or less, more preferably 50 GΩ / sq. or less. The thickness of the second absorber film 14b is 20 nm or more, preferably 50 nm or less, more preferably 30 nm or less.

[0040] Further, the sheet resistance value of the first absorber film 14a is preferably less than 500 kΩ / sq., preferably less than 1.0×10 3 Ω / sq., more preferably 7.5×10 2 Ω / sq. or less, and even more preferably 5.0×10 2 Ω / sq. or less. The lower limit of the sheet resistance value of the first absorber film 14a is not particularly limited, and preferably 1.0×10 -1 Ω / sq. or more, more preferably 1.0×10 0 Ω / sq. or more. When the sheet resistance value of the first absorber film 14a is less than 500 kΩ / sq., the first absorber film 14a corresponds to a non-insulating layer described later. The sheet resistance value can be measured by the same method as the method for measuring the sheet resistance value of the protective film. Examples of materials constituting the first absorber film 14a include materials containing the first element described above. More specifically, examples include elemental Ru metal, Ru nitride, Ru oxide, Ru oxynitride, Ru boride, elemental Ir metal, Ir nitride, Ir oxide, Ir oxynitride, Ir boride, Ta nitride, and elemental Pt metal.

[0041] [Insulating layer] The insulating layer of the first embodiment of the reflective mask blank of the present invention is a layer having a sheet resistance of 500 kΩ / sq. or more. In the embodiment shown in Figure 1, the second absorber film 14b corresponds to the insulating layer. The insulating layer may be a single-layer structure or a multi-layer structure composed of adjacent layers. If the insulating layer is a single-layer structure, the sheet resistance of the insulating layer is 500 kΩ / sq. or higher, and the thickness of the insulating layer is 20 nm or higher. Furthermore, the first embodiment of the reflective mask blank of the present invention is not limited to the above-described embodiment, and the insulating layer may be a multilayer structure composed of adjacent layers. In the case of a multilayer structure in which the insulating layer is composed of adjacent layers, the sheet resistance value of each layer constituting the insulating layer is 500 kΩ / sq. or more, and the total thickness of each layer is 20 nm or more. The sheet resistance value can be measured in accordance with the method for measuring the sheet resistance value of the protective film. The insulating layer is preferably positioned on the surface side of the reflective mask blank that is furthest from the substrate.

[0042] [Non-insulating layer] In the first embodiment of the reflective mask blank of the present invention, a non-insulating layer may be included. The non-insulating layer is a layer with a sheet resistance of less than 500 kΩ / sq. In the embodiment shown in Figure 1, the first absorber film 14a corresponds to the non-insulating layer. The sheet resistance value can be measured in accordance with the method for measuring the sheet resistance value of the protective film.

[0043] The non-insulating layer that the first embodiment of the reflective mask blank of the present invention may have may be one layer or two or more layers. If the reflective mask blank has two or more non-insulating layers, the two or more non-insulating layers may be arranged adjacent to each other, or other layers may be arranged between the two or more non-insulating layers.

[0044] [Hard mask film] The first embodiment of the reflective mask blank of the present invention may have a hard mask film. The hard mask film is preferably located on the side opposite to the substrate side of the absorber film. Figure 2 shows an embodiment having a hard mask film. The reflective mask blank 10b shown in Figure 2 has a substrate 11, a multilayer reflective film 12, a protective film 13, an absorber film 14ta, and a hard mask film 15 in this order. The hard mask film 15 is located on the surface side of the reflective mask blank 10b that is furthest from the substrate 11. The absorber film 14ta is composed of a first absorber film 14a and a second absorber film 14b from the substrate 11 side, and the second absorber film 14b corresponds to an insulating layer exhibiting a sheet resistance value of 500 kΩ / sq. or more. The thickness of the second absorber film 14b is 20 nm or more. The components other than the hard mask film 15 are as described above.

[0045] The elements included in the material constituting the hard mask film are preferably at least one element selected from the group consisting of Si, Ti, Cr, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, In, Sn, Hf, Ta, and Ir.

[0046] As the hard mask film, it is preferable to use a material that has high resistance to dry etching, such as a Si-based film, a Cr-based film, a Nb-based film, a Mo-based film, a Ru-based film, and a Ta-based film. The hard mask film is preferably made of a material containing the above elements and one or more elements selected from the group consisting of O, N, C, B, and H, and more preferably made of a material containing the above elements and one or more elements selected from the group consisting of N and C. Hereinafter, a material containing Cr and O will be written as "CrO", and a material containing Cr, O, and N will be written as "CrON". Examples of materials that make up Si-based films include Si (pure Si), SiO2, SiON, SiN, SiO, SiC, SiCO, SiCN, and SiCON. Examples of materials that make up Cr-based films include Cr (elemental Cr), CrC, CrB, CrBN, CrO, CrN, and CrON. Examples of materials that make up Nb-based films include Nb (elemental Nb), NbC, NbB, NbBN, NbO, NbN, and NbON. Examples of materials that make up Mo-based films include Mo (elemental Mo), MoC, MoB, MoBN, MoO, MoN, and MoON. Examples of materials that make up Ru-based films include Ru (elemental Ru), RuC, RuB, RuBN, RuO, RuN, and RuON. Examples of materials that constitute Ta-based films include Ta (elemental Ta), TaC, TaB, TaBN, TaO, TaN, and TaON.

[0047] By forming a hard mask film on the absorber film, dry etching can be performed even if the minimum line width of the absorber film pattern becomes small. Therefore, it is effective for miniaturizing the absorber film pattern.

[0048] The thickness of the hard mask film is preferably 1 to 20 nm, and more preferably 5 to 15 nm.

[0049] The hard mask film can be formed by known film deposition methods, such as magnetron sputtering or ion beam sputtering. When forming a RuON film by sputtering, a reactive sputtering method using a Ru target should be performed in a gas atmosphere consisting of a mixture of an inert gas containing at least one of He, Ar, Ne, Kr, and Xe, along with oxygen and nitrogen gases.

[0050] In the embodiment shown in Figure 2, the hard mask film 15 may correspond to the non-insulating layer or to a part of the insulating layer. That is, the sheet resistance value of the hard mask film in the embodiment shown in Figure 2 may be less than 500 kΩ / sq. or 500 kΩ / sq. or greater. In the embodiment shown in Figure 2, when the hard mask film 15 corresponds to a non-insulating layer, the sheet resistance value of the hard mask film 15 is preferably 1 kΩ / sq. or less, more preferably 750 Ω / sq. or less, and even more preferably 500 Ω / sq. or less. The lower limit of the sheet resistance value of the hard mask film 15 is not particularly limited, but it is 0.1 Ω / sq. or more, and preferably 1 Ω / sq. or more. The method for measuring the sheet resistance is as described above. In the embodiment shown in Figure 2, when the sheet resistance of the hard mask film 15 is 1 kΩ / sq. or less, it corresponds to an embodiment in which the sheet resistance of the layer located on the surface side furthest from the substrate 11 of the reflective mask blank 10b is 1 kΩ / sq. or less.

[0051] [Conductive film on the back surface] In the first embodiment of the reflective mask blank of the present invention, a back surface conductive film may be provided on the surface of the substrate opposite to the first main surface (second main surface). By providing a back surface conductive film, the reflective mask blank can be handled by an electrostatic chuck. The conductive film on the back surface is preferably low in sheet resistance. The sheet resistance of the conductive film on the back surface is preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The constituent materials for the back surface conductive film can be broadly selected from those described in known literature. For example, a high dielectric constant coating described in Japanese Patent Publication No. 2003-501823, specifically a coating consisting of Si, Mo, Cr, CrON, or TaSi, can be applied. Alternatively, the constituent materials for the back surface conductive film may be a Cr compound containing Cr and one or more elements selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more elements selected from the group consisting of B, N, O, and C. The thickness of the conductive film on the back surface is preferably 10 to 1000 nm, and more preferably 10 to 400 nm. Furthermore, the back surface conductive film may also have a function of adjusting the stress on the second main surface side of the reflective mask blank. That is, the back surface conductive film can balance the stress from the various films formed on the first main surface side and adjust the reflective mask blank to be flat. The conductive film on the back surface can be formed using known film deposition methods, such as sputtering methods including magnetron sputtering and ion beam sputtering, CVD, vacuum deposition, and electrolytic plating.

[0052] [Dielectric breakdown voltage] The dielectric breakdown voltage of the first embodiment of the reflective mask blank of the present invention is preferably 3.00V or higher. The dielectric breakdown voltage is measured between the surface of the reflective mask blank at the position furthest from the substrate and the protective film. A detailed method for measuring the dielectric breakdown voltage follows the measurement method described in the later examples. The dielectric breakdown voltage may also be measured after exposing the protective film by methods such as etching. The dielectric breakdown voltage can be adjusted by the material used for the insulating layer and the thickness of the insulating layer, among other factors. When the dielectric breakdown voltage is high, dielectric breakdown is more likely to be suppressed when processing is performed using charged particle beams.

[0053] <Modified example of the first embodiment of the reflective mask blank>

[0054] The following describes modifications of the first embodiment of the reflective mask blank. Note that the following modifications may also have some of the same configurations as the first embodiment of the reflective mask blank described above.

[0055] In the first embodiment of the reflective mask blank of the present invention shown in Figure 1 above, the absorber membrane 14ta has a two-layer structure, consisting of a first absorber membrane 14a and a second absorber membrane 14b in that order from the protective membrane 13 side, but the present invention is not limited to this embodiment. For example, the reflective mask blank of the present invention may be in the form shown in Figure 3. The reflective mask blank 10c shown in Figure 3 comprises a substrate 11, a multilayer reflective film 12, a protective film 13, and an absorber film 14tb in that order. The absorber film 14tb is composed of a second absorber film 14b and a first absorber film 14a from the substrate 11 side, with the second absorber film 14b being an insulating layer exhibiting a sheet resistance of 500 kΩ / sq. or more. The thickness of the second absorber film 14b is 20 nm or more. In the embodiment shown in Figure 3, the positions of the first absorber membrane 14a and the second absorber membrane 14b are swapped, but otherwise it is the same as the embodiment shown in Figure 1, so the explanation of each component is omitted.

[0056] Furthermore, the reflective mask blank of the present invention may also have a structure in which the absorber film consists of three or more layers, and one of these layers corresponds to the insulating layer with a thickness of 20 nm or more as described above. For example, the absorber film may have a three-layer structure, with a first absorber film, a second absorber film, and a third absorber film arranged from the substrate side, and the third absorber film being an insulating layer with a thickness of 20 nm or more. That is, in the first embodiment of the reflective mask blank of the present invention shown in Figure 1, the first absorber film 14a may consist of two or more layers.

[0057] Furthermore, the reflective mask blank of the present invention may, for example, have an absorber film with a structure of three or more layers, where two or more adjacent layers correspond to a multilayer insulating layer composed of adjacent layers, and the total thickness may be 20 nm or more. For example, the absorber film may have a three-layer structure, with a first absorber film, a second absorber film, and a third absorber film arranged from the substrate side, with the sheet resistance values ​​of the second and third absorber films being 500 kΩ / sq. or more, and the total thickness of the second and third absorber films being 20 nm or more. That is, in the first embodiment of the reflective mask blank of the present invention shown in Figure 1, the second absorber film 14b may be composed of two or more layers. Furthermore, the absorber membrane may have a structure of three or more layers, with each layer constituting the absorber membrane having a sheet resistance of 500 kΩ / sq. or more, and the total thickness of the absorber membrane may be 20 nm or more.

[0058] Furthermore, the reflective mask blank of the present invention may have a single-layer structure for the absorber film, and the single layer itself may correspond to the insulating layer with a thickness of 20 nm or more as described above. In other words, the reflective mask blank of the present invention may be in the form shown in Figure 4. The reflective mask blank 10d shown in Figure 4 has a substrate 11, a multilayer reflective film 12, a protective film 13, and an absorber film 14s in that order. The absorber film 14s corresponds to an insulating layer with a sheet resistance of 500 kΩ / sq. or more, and the thickness of the absorber film 14s is 20 nm or more. A preferred embodiment of the material constituting the absorber membrane 14s is the same as a preferred embodiment of the material constituting the second absorber membrane 14b in the embodiment shown in Figure 1. In the embodiment shown in Figure 4, the structure is the same as that shown in Figure 1, except that the absorber membrane has a single-layer structure; therefore, a description of each component is omitted.

[0059] Furthermore, in the first embodiment of the reflective mask blank shown in Figure 1 above, the first absorber film 14a corresponds to a non-insulating layer, but the first absorber film 14a may also correspond to an insulating layer.

[0060] Furthermore, in the reflective mask blank of the present invention, the protective film may include an insulating layer on the absorber film side, which may be a single-layer structure or a multi-layer structure composed of adjacent layers. Unlike the above embodiment, it may also include an insulating layer made of a component other than the absorber film. If the thickness of the insulating layer made of a component other than the absorber film is 20 nm or more, the absorber film does not need to be considered an insulating layer. For example, in the embodiment shown in Figure 2, the reflective mask blank of the present invention may have a first absorber film 14a and a second absorber film 14b that do not correspond to insulating layers, a hard mask film 15 that corresponds to an insulating layer (sheet resistance value of 500 kΩ / sq. or more), and a thickness of 20 nm or more.

[0061] <Second embodiment of reflective mask blank> A second embodiment of the reflective mask blank of the present invention is shown in Figure 5. The reflective mask blank 10e shown in Figure 5 has a substrate 11, a multilayer reflective film 12, a protective film 13, an absorber film 14tc, and a hard mask film 15a in that order. The hard mask film 15a is located on the surface side of the reflective mask blank 10e furthest from the substrate 11, and the sheet resistance of the hard mask film 15a is 500 kΩ / sq. or higher. The absorber film 14tc is composed of a first absorber film 14c and a second absorber film 14d from the substrate 11 side, and the sheet resistance of the second absorber film 14d is 500 kΩ / sq. or higher. The second absorber film 14d and the hard mask film 15a are adjacent to each other. Furthermore, the thickness of the second absorber film 14d and the hard mask film 15a is less than 20 nm each, and the combined thickness of the second absorber film 14d and the hard mask film 15a is 20 nm or more. In other words, the second absorber film 14d and the hard mask film 15a correspond to a multilayer insulating layer composed of adjacent layers. As shown in Figure 5, even in the reflective mask blank 10e, the total thickness of the insulating layer, the second absorber film 14d, and the hard mask film 15a is 20 nm or more, so the electric field strength does not easily increase, and as a result, the occurrence of dielectric breakdown is suppressed.

[0062] In the second embodiment of the reflective mask blank of the present invention shown in Figure 5, the configuration is the same as that of the reflective mask blank of the first embodiment, except for differences in the thickness of the second absorber film 14d and the hard mask film 15a, and the sheet resistance value of the hard mask film 15a. Therefore, a detailed explanation is omitted.

[0063] <Method for manufacturing a reflective mask and the reflective mask itself> A reflective mask is obtained by patterning the absorbent film of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be described with reference to Figure 6. In the following description, a method for manufacturing a reflective mask using the reflective mask blank 10d, a modified example of the first embodiment described in Figure 4, will be described, but a reflective mask can be manufactured in the same manner using the other embodiments described above.

[0064] Figure 6(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having a substrate 11, a multilayer reflective film 12, a protective film 13, and an absorber film 14s in that order. A known method can be used to form the resist pattern 40. For example, a resist can be applied to the absorber film 14s of the reflective mask blank, and then exposed and developed to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Subsequently, the absorber film 14s is etched and patterned using the resist pattern 40 in Figure 6(a) as a mask, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 14pt shown in Figure 5(b). If the reflective mask blank has a hard mask film, the hard mask film located at the openings of the resist pattern 40 may be removed by etching before etching the absorber film 14s, and then the absorber film 14s may be etched and patterned. Next, as shown in Figure 6(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 6(b), and dry etching is performed using the resist pattern 41 in Figure 6(c) as a mask. Dry etching is carried out until the substrate 11 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 6(d).

[0065] Dry etching for forming the absorber film pattern 14pt can be performed using, for example, a Cl-based gas or a F-based gas. If the reflective mask blank has a hard mask film, the etching of the hard mask film located at the openings of the resist pattern 40 may be performed by wet etching using a chemical solution or by dry etching. It is also preferable to select an etching method that etches the hard mask film but does not etch the absorber film 14s. The resist pattern 40 or 41 can be removed by known methods, including removal with a cleaning solution. Examples of cleaning solutions include sulfuric acid-hydrogen peroxide aqueous solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide aqueous solution (APM), OH radical cleaning water, and ozonated water.

[0066] The reflective mask obtained by patterning a phase-shift film on the reflective mask blank of the present invention can be suitably applied as a reflective mask used for exposure with EUV light. [Examples]

[0067] The present invention will be described in more detail below based on examples. The materials, quantities, proportions, processing details, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Examples 1-3, described below, are examples of actual cases, while Examples 4-7 are comparative examples.

[0068] <Manufacturing of reflective mask blanks> The reflective mask blank for Example 1 was manufactured using the following procedure. A SiO2-TiO2 glass substrate (152mm square, approximately 6.3mm thick) was used as the substrate. This glass substrate has a thermal expansion coefficient of 0.2 × 10⁻⁶. -7 / ℃, Young's modulus 67 GPa, Poisson's ratio 0.17, specific stiffness 3.07 × 10 7 m 2 / s 2 The glass substrate was polished to a surface roughness (root mean square height Sq) of 0.15 nm or less and a flatness of 100 nm or less on the main surface. A CrN layer approximately 100 nm thick was deposited on the back surface (the side opposite to the processed surface) of the glass substrate using magnetron sputtering to form a conductive film for the electrostatic chuck. The sheet resistance of the CrN layer was approximately 100 Ω / □.

[0069] Next, the glass substrate was fixed into the deposition chamber using an electrostatic chuck via electrostatic adsorption. In this state, a multilayer reflective film was deposited on the first main surface (processed surface) of the glass substrate. For the deposition of the multilayer reflective film, ion beam sputtering was used, and a 2.3 nm thick Mo layer and a 4.5 nm thick Si layer were deposited alternately 40 times each to form a Mo / Si multilayer reflective film. For the deposition of the Mo layer, an Mo target was used, and ion beam sputtering was performed under an Ar gas atmosphere (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the deposition rate was 3.84 nm / min. On the other hand, for the deposition of the Si layer, a boron-doped Si target was used, and ion beam sputtering was performed under an Ar gas atmosphere (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the deposition rate was 4.62 nm / min. The total thickness of the multilayer reflective film (target value) is (2.3 nm + 4.5 nm) × 40 times = 272 nm. The top layer of the multilayer reflective film is a Si layer.

[0070] Next, a protective film was formed on the multilayer reflective film using ion beam sputtering. The protective film consists of two layers, a Ru layer and an Rh layer, in that order from the substrate side. The Ru layer was deposited using ion beam sputtering in an Ar gas atmosphere with a Ru target (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the deposition rate was 3.12 nm / min. The thickness of the Ru layer was 1.0 nm. The Rh layer was deposited using an Rh target under an Ar gas atmosphere by ion beam sputtering (gas pressure: 0.027 Pa). The applied voltage was 600 V, and the deposition rate was 4.62 nm / min. The thickness of the Rh layer was 1.5 nm.

[0071] Next, an absorber film was formed on the protective film using ion beam sputtering and magnetron sputtering. The absorber film consisted of three layers, arranged in order from the substrate side: a RuN layer, a TaN layer, and a TaON layer. The absorber film was formed with a portion of it masked. For the deposition of the RuN layer, magnetron sputtering was performed using a Ru target in a mixed gas atmosphere of Ar gas and N2 gas (Ar gas: 80 vol%, N2 gas: 20 vol%) (gas pressure: 0.2 Pa). The applied voltage was 700 V, and the deposition rate was 3.0 nm / min. The thickness of the RuN layer was 29 nm. For the deposition of the TaN layer, magnetron sputtering was performed using a Ta target in an atmosphere of mixed gas (Ar gas: 95 vol%) and N2 gas (N2 gas: 5 vol%). The deposition rate was 1.74 nm / min, and the thickness of the TaN layer was 8 nm. For the deposition of the TaON layer, magnetron sputtering was performed using a Ta target in an atmosphere of mixed gases (Ar gas: 60 vol%, N2 gas: 30 vol%, O2 gas: 10 vol%). The deposition rate was 0.6 nm / min, and the thickness of the TaON layer was 30 nm.

[0072] Following the procedure described above, a reflective mask blank of Example 1 was obtained. In the reflective mask blank of Example 1, the protective film was exposed in the area masked by the procedure described above, while an absorbent film was formed in the other areas. The results of measuring the sheet resistance values ​​of each layer of the reflective mask blanks in Example 1 and Examples 2-7 (described later) using the method described above are shown in the table below. The reflective mask blanks in Examples 2-7 were obtained as follows.

[0073] The reflective mask blanks in Examples 2 and 4-7 were manufactured using the same procedure as the reflective mask blank in Example 1, except that the thickness of the TaON layer was changed to the thickness shown in the table below.

[0074] In Example 3, the reflective mask blank was prepared by forming each layer in the same manner as in Example 1, except that the thickness of the TaON layer was set to 11 nm. Next, an SiO layer was deposited on the TaON layer. The SiO layer corresponds to the hard mask film. The SiO layer was deposited using a SiO2 target and high-frequency sputtering in an Ar gas atmosphere. The thickness of the SiO layer was 25 nm. Following the procedure described above, the reflective mask blank for Example 3 was obtained.

[0075] <Measurement and Evaluation> (Measurement of dielectric breakdown voltage) The dielectric breakdown voltage between the exposed protective film and the outermost surface of the reflective mask blank was measured using a manual prober (Hysol Co., Ltd., model: HMP-400). The straight-line distance in the planar direction between the measuring terminal in contact with the protective film and the measuring terminal in contact with the outermost surface was set to 20 mm. Furthermore, using the above method, if the electrical resistance of the protective film is low, the dielectric breakdown voltage between the outermost surface and the protective film can be measured. Furthermore, when the electrical resistance of the protective film is low, the dielectric breakdown voltage mainly depends on the electrical resistance of the layer located on the opposite side of the substrate from the protective film, in the direction perpendicular to the substrate, and on the thickness of that layer, while the electrical resistance of the substrate in the direction horizontal can be ignored. Therefore, even if the linear distance during the measurement is changed from 20 mm to 100 mm and the dielectric breakdown voltage is measured, the value will be the same as in the case of 20 mm. In measuring the dielectric breakdown voltage, the voltage was swept from 0V at a rate of 10mV / sec, and the current value at each voltage was recorded to obtain a current-voltage curve. The obtained current-voltage curve showed a shape in which the current value increased sharply above a certain voltage. Here, a steep increase in current value was evaluated by the change in the slope of the current-voltage curve (the second derivative of the current value with respect to voltage). Specifically, the current-voltage curve obtained by the above method was first normalized to the set maximum current value of 100 mA. In the normalized current-voltage curve, the voltage value at which the second derivative of the current value with respect to voltage first became greater than 0.05 was defined as the dielectric breakdown voltage.

[0076] (Dielectric breakdown resistance) Dielectric breakdown resistance was evaluated based on the measured dielectric breakdown voltage according to the following criteria. In practical terms, an A rating is preferable. A: Dielectric breakdown voltage is 3.00V or higher • B: Dielectric breakdown voltage is 2.00V or more and less than 3.00V • C: Dielectric breakdown voltage is less than 2.00V Furthermore, the higher the dielectric breakdown voltage, that is, the better the dielectric breakdown resistance, the more the occurrence of dielectric breakdown is suppressed when processing with charged particle beams.

[0077] <Result> Table 1 shows the layer configuration for each example and the evaluation results of the dielectric breakdown voltage and dielectric breakdown resistance. The sheet resistance of each layer was measured using the method described above, with each layer formed on the sample. In Table 1, the entry ">40M" in the "Sheet Resistance Value" column indicates that the sheet resistance value was 40 MΩ / sq. or greater. The "k" in "10k" represents the SI prefix "kilo," indicating that the sheet resistance value was 10 kΩ / sq.

[0078] [Table 1]

[0079] As shown in Table 1, the results from Examples 1 to 3 confirmed that the reflective mask blank of the present invention exhibits excellent dielectric breakdown resistance. On the other hand, the results from Examples 4 to 7 confirmed that dielectric breakdown resistance is poor when the thickness of the insulating layer is below a predetermined value. As mentioned above, the better the dielectric breakdown resistance, the more the occurrence of dielectric breakdown is suppressed when processing with charged particle beams. [Explanation of symbols]

[0080] 10a~10e Reflective Mask Blank 11 circuit boards 12 Multilayer reflective film 13 Protective film 14ta, 14tb, 14tc, 14s Absorbent membrane 14a, 14c First absorber membrane 14b, 14d Second absorber membrane 14pt Absorber membrane pattern 15,15a Hard mask film 40,41 Resist Pattern

Claims

1. circuit board and A multilayer reflective film that reflects EUV light, Protective film and, A reflective mask blank having an absorbent membrane in this order, The protective film includes an insulating layer on the absorber film side, which is composed of a single layer or a multi-layer structure consisting of adjacent layers. If the insulating layer has a single-layer structure, the sheet resistance of the insulating layer is 40 MΩ / sq. or more, and the thickness of the insulating layer is 20 nm or more. If the insulating layer has a multilayer structure composed of adjacent layers, the sheet resistance value of each layer constituting the insulating layer is 40 MΩ / sq. or more, and the total thickness of each layer is 20 nm or more. A reflective mask blank in which the sheet resistance of the layer located on the surface side furthest from the substrate is 1 kΩ / sq. or less.

2. The reflective mask blank according to claim 1, wherein a non-insulating layer having a sheet resistance of less than 500 kΩ / sq. is included on the side of the protective film opposite to the substrate side.

3. The reflective mask blank according to claim 1, wherein the insulating layer is arranged on the surface side of the reflective mask blank that is furthest from the substrate.

4. The mask blank according to claim 1, wherein the dielectric breakdown voltage between the surface of the reflective mask blank at the position furthest from the substrate and the protective film is 3.00V or more.

5. A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank according to any one of claims 1 to 4.

6. A method for manufacturing a reflective mask, comprising the step of patterning the absorbent membrane of a reflective mask blank according to any one of claims 1 to 4.

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