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

Abstract

Provided is a reflective mask blank that is less likely to retain defects caused by foreign matter, etc. after being subjected to a cleaning process.　This reflective mask blank has a substrate, a multilayer reflective film that reflects EUV light, and an absorber film in that order. A compound having a carbonyl group with 4 to 8 carbon atoms is attached to at least one of two main surfaces of the reflective mask blank.

Description

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

[0001] The present invention relates to a reflective mask used for EUV (Extreme Ultra Violet) lithography used in an exposure process of semiconductor manufacturing, a method for manufacturing the same, and a reflective mask blank which is a substrate of the reflective mask.

[0002] In recent years, for further miniaturization of semiconductor devices, EUV lithography using EUV light having a central wavelength near 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 that reflects EUV light formed on a substrate, and an absorber film that absorbs EUV light is patterned on the multilayer reflective film.

[0004] 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. For example, in Prior Art Document 1, there is disclosed a reflective mask blank having a substrate, a multilayer reflective film, and an absorber film, the absorber film including an upper layer formed of a material containing any one of oxides, nitrides, oxynitrides, or carbides of tantalum, and a lower layer formed of a material containing tantalum.

[0005] Japanese Patent No. 5638769

[0006] Since foreign matter on the main surface of the reflective mask blank causes patterning defects, usually, after manufacturing the reflective mask blank and before patterning, it is subjected to a cleaning process. The inventors of the present invention examined the mask blank described in Patent Document 1 and found that foreign matter remains on the main surface of the mask blank after cleaning and improvement is required.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a reflective mask blank in which defects derived from foreign matters or the like are unlikely to remain after being subjected to a cleaning process. Another object of the present invention is to provide a reflective mask and a method for manufacturing a reflective mask.

[0008] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by attaching a predetermined compound to the main surface, and have thus arrived at the present invention. That is, the inventors have found that the above problems can be solved by the following configuration. [1] A reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, and an absorber film, in this order, wherein a compound having a carbonyl group with 4 to 8 carbon atoms is attached to at least one of the two main surfaces of the reflective mask blank. [The reflective mask blank] [2] The reflective mask blank according to [1], wherein the amount of the compound attached to each of the at least one main surface is 0.03 to 5.4 ng / cm ２ The reflective mask blank according to [I], which is [6] The reflective mask blank according to [1], wherein the amount of the compound attached to each of the at least one main surface is 0.3 to 4.3 ng / cm ２A reflective mask blank according to [1] or [2]. [4] A reflective mask blank according to any one of [1] to [3], wherein the compound is at least one compound selected from the group consisting of maleic anhydride, butyraldehyde, cyclopentenone, benzaldehyde, 2-ethylhexylaldehyde, cyclopentanone, methylcyclopentenone, and dimethylcyclopentanone. [5] A reflective mask blank according to any one of [1] to [4], wherein the absorbent film contains one or more metal elements selected from the group consisting of Ta, Cr, Nb, Ir, Co, Ni, Cu, Sn, Pt, Pd, Au, W, and Ru. [6] A reflective mask blank according to any one of [1] to [5], wherein the reflective mask blank has a protective film between the multilayer reflective film and the absorbent film, and the protective film contains at least one element selected from the group consisting of Si, Ru, and Rh. [7] The reflective mask blank according to any one of [1] to [6], wherein the reflective mask blank has a conductive film on the side of the substrate opposite to the multilayer reflective film side, and the conductive film comprises one or more selected from the group consisting of Cr, B, N, O, and C. [8] The reflective mask blank according to any one of [1] to [6], wherein the reflective mask blank has a conductive film on the side of the substrate opposite to the multilayer reflective film side, and the conductive film comprises one or more selected from the group consisting of Ta, B, N, O, and C. [9] A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank according to any one of [1] to [8].

[10] A method for manufacturing a reflective mask, comprising the step of patterning the absorbent film of the reflective mask blank according to any one of [1] to [8].

[0009] According to the present invention, it is possible to provide a reflective mask blank that is less likely to have defects caused by foreign matter after being subjected to a cleaning process. Furthermore, the present invention can also provide a reflective mask and a method for manufacturing a reflective mask.

[0010] Figure 2(a) to Figure 2(d) are schematic cross-sectional views showing an example of an embodiment of the reflective mask blank of the present invention.

[0011] The meanings of terms used in this invention are as follows: A numerical range indicated by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. In this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum may be represented by their corresponding element symbols (B, C, N, O, Si, Ti, Cr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, etc.). In this specification, silicon (Si) is included in the metallic elements.

[0012] [Reflective Mask Blank] The reflective mask blank of the present invention is a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, and an absorber film in that order, wherein a compound having carbonyl groups with 4 to 8 carbon atoms (hereinafter also referred to as "compound X") is attached to at least one of the two main surfaces of the reflective mask blank. Hereinafter in this specification, of the two main surfaces of the reflective mask blank, the main surface on the absorber film side will be referred to as the "first main surface," and the main surface on the substrate side will be referred to as the "second main surface." The two main surfaces face each other.

[0013] The reflective mask blank of the present invention will be described with reference to the drawings. Figure 1 is a schematic 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 Figure 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in this order. The reflective mask blank 10 shown in Figure 1 has a first main surface 10A on the side facing the absorber film 18 and a second main surface 10B on the side facing the substrate 12, and a compound X (not shown) is attached to at least one of the first main surface 10A on the absorber film 18 side and the second main surface 10B on the substrate 12 side. In the reflective mask blank 10 shown in Figure 1, the first main surface 10A corresponds to the surface of the absorber film 18 opposite to the protective film 16 side, and the second main surface 10B corresponds to the surface of the substrate 12 opposite to the multilayer reflective film 14 side. The reflective mask blank 10 shown in Figure 1 may also have a hard mask film, which will be described later, on the side of the absorber film 18 opposite to the substrate 12 side. Furthermore, the reflective mask blank 10 shown in Figure 1 may have a conductive film, described later, on the side of the substrate 12 opposite to the multilayer reflective film 14. The two main surfaces of the reflective mask blank also correspond to the outermost surface of the reflective mask blank. For example, if the reflective mask blank has the hard mask film on its outermost surface, the surface of the hard mask film corresponds to the main surface. The reflective mask blank 10 shown in Figure 1 has a protective film 16, but the protective film 16 may be omitted.

[0014] The reflective mask blank of the present invention is less likely to have defects caused by foreign matter after being subjected to the cleaning process. Although the details of this reason are unclear, the inventors speculate as follows: Small foreign matter can cause defects that are problematic in reflective masks, but during the cleaning process, the force from the cleaning solution does not work effectively, making it difficult to remove from the main surface. The reflective mask blank of the present invention has compound X attached to its main surface. Compound X can adhere to the main surface by interacting with it through its carbonyl group, and at the same time, because the number of carbon atoms is within a predetermined range, compound X itself is less likely to remain as a defect after cleaning. In the reflective mask blank of the present invention, the presence of compound X on the main surface reduces the interaction between foreign matter and the main surface, suppressing the adhesion of foreign matter and making it easier to remove. Furthermore, even if the size of the foreign matter is small, the force derived from cavitation etc. that occurs on the main surface during the cleaning process can remove the foreign matter along with the compound X attached to the main surface. As a result, it is presumed that the reflective mask blank of the present invention is less likely to have defects because foreign matter is efficiently removed when subjected to the cleaning process. In the following, the fact that defects caused by foreign matter, etc., are less likely to remain after the reflective mask blank has been subjected to the cleaning process will also simply be referred to as "the effects of the present invention are superior."

[0015] The configuration of the reflective mask blank of the present invention will be described in detail below.

[0016] [Compound X] The reflective mask blank of the present invention has compound X attached to at least one of its two main surfaces.

[0017] Compound X is a compound having a carbonyl group with 4 to 8 carbon atoms. The number of carbon atoms in compound X includes the carbon atoms of the carbonyl group. The carbonyl group may be, for example, part of an aldehyde group or part of an acid anhydride group. Compound X may be linear, branched, or cyclic. Compound X may be either an aliphatic compound or an aromatic compound. Compound X may have unsaturated bonds other than the carbonyl group, such as a carbon-carbon double bond. Compound X may have substituents that do not contain a carbonyl group, such as a hydroxyl group, but it is preferable that it does not. Examples of compound X include ketones with 4 to 8 carbon atoms, aldehydes with 4 to 8 carbon atoms, and acid anhydrides with 4 to 8 carbon atoms.

[0018] Compound X is preferably at least one compound selected from the group consisting of maleic anhydride, butyraldehyde, cyclopentenone, benzaldehyde, 2-ethylhexylaldehyde, cyclopentenone, methylcyclopentenone, and dimethylcyclopentanone, and more preferably at least one compound selected from the group consisting of maleic anhydride, butyraldehyde, cyclopentenone, benzaldehyde, and 2-ethylhexylaldehyde. Compound X may be used alone or in combination of two or more compounds.

[0019] Compound X may adhere to only one of the first and second main surfaces, or to both the first and second main surfaces. If the reflective mask blank does not have other layers on the surface opposite to the substrate side of the absorber film, the first main surface is the surface of the absorber film. If it has other layers (e.g., a hard mask film described later), the first main surface is the outermost surface of the other layers. Also, if the reflective mask blank does not have other layers on the surface opposite to the multilayer reflective film side of the substrate, the second main surface is the surface of the substrate. If it has other layers (e.g., a conductive film described later), the second main surface is the outermost surface of the other layers. The material of the main surface to which compound X adheres is not particularly limited, but it is preferably a layer containing a metal element, and preferably a layer containing at least one metal element A selected from the group consisting of Ta, Cr, W, Ru, Sn, Pt, Nb, Au, Pd, Ir, Cu, and Co. Examples of materials for the main surface to which compound X adheres include elemental metal A, alloys containing metal A, and materials containing metal A and at least one element selected from the group consisting of B, C, N, and O. More specifically, examples include materials constituting each film that constitutes the reflective mask blank of the present invention, which will be described later. Compound X may also adhere to surfaces other than the main surface of the reflective mask blank (for example, the sides).

[0020] The manner in which compound X adheres is not particularly limited, and adsorption is one example. Compound X may adhere to the main surface in a layered manner or in a dispersed manner.

[0021] The amount of compound X adhering to one of the main surfaces is 0.01 to 6.0 ng / cm², which is preferable for achieving the best effect of the present invention. ２ Preferably, 0.03 to 5.4 ng / cm³ ２ More preferably, 0.3 to 4.3 ng / cm ２is more preferable. The deposition amount of the above compound X is a value in terms of n-hexadecane measured by the wafer thermal desorption-gas chromatography / mass spectrometry (WTD-GC / MS) method. More specifically, the deposition amount of compound X on one main surface is a value calculated by the following method. A reflective mask blank sample is heated to 400 °C in an inert gas stream, and the organic substances thermally desorbed from one main surface of the reflective mask blank sample are collected and concentrated on a solid adsorbent. Using the solid adsorbent on which the organic substances are collected, GC / MS (ionization method: electron impact (EI) method, 70 eV) analysis is performed, and using n-hexadecane as a standard substance, the deposition amount per unit area of the sample of each compound on one main surface is calculated in terms of n-hexadecane. Compound X may be used alone or in combination of two or more. When compound X contains two or more compounds, the deposition amount of the above compound X is the total deposition amount of each compound.

[0022] As a method for attaching compound X to the main surface, for example, a method of exposing the main surface of the reflective mask blank to the vapor of compound X, a method of bringing the solution containing compound X into contact with the main surface of the reflective mask blank, etc. can be mentioned. The deposition amount of compound X can be adjusted by the above exposure conditions, contact conditions, etc.

[0023] [Substrate] The substrate of the reflective mask blank of the present invention preferably has a small thermal expansion coefficient. When the thermal expansion coefficient 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 thermal expansion coefficient 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 with a small thermal expansion coefficient include SiO ２ -TiO ２ -based glass, etc., but are not limited thereto, and crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metal silicon, and substrates such as metals can also be used. SiO ２ -TiO ２ -based glass is SiO ２90-95% by mass, TiO ２ It is preferable to use quartz glass containing 5 to 10% by mass of TiO. ２ When the content is 5 to 10 mass%, the coefficient of linear expansion at room temperature is approximately zero, and there is almost no dimensional change at room temperature. ２ -TiO ２ The glass system is SiO ２ and TiO ２ It may also contain trace amounts of other components.

[0024] The surface of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first substrate main surface") preferably has high surface smoothness. The surface smoothness of the first substrate main surface can be evaluated by its surface roughness. The surface roughness of the first substrate 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 surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first substrate main surface is preferably surface-processed to have a predetermined flatness, in terms of excellent pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. Specifically, 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 area of ​​the first substrate main surface (for example, an area of ​​132 mm × 132 mm). Flatness can be measured with a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate can be appropriately determined by the design of the mask, etc. Examples of substrate dimensions include an outer diameter of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm). Substrates are often rectangular or square in shape. It is preferable that the substrate has high rigidity to prevent deformation due to film stress in the films (multilayer reflective films and absorber films, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0025] [Multilayer Reflective Film] The multilayer reflective film 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 of EUV light. Specifically, the maximum reflectivity of EUV light around a wavelength of 13.5 nm when EUV light is incident on the multilayer reflective film at an incident angle of 6° 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.

[0026] Multilayer reflective films typically utilize alternating layers of high refractive index (FRF) layers and low refractive index (DRF) layers, which exhibit a high refractive index for EUV light, multiple times, as they can achieve high reflectivity for EUV light. The multilayer reflective film may be constructed by stacking layers in this order from the substrate side, forming one period, or by stacking layers in this order from the substrate side, forming one period. A layer containing Si can be used as the FRF layer. Si-containing materials include pure Si and Si compounds containing Si and at least one element selected from the group consisting of B, C, N, and O. Using a FRF layer containing Si provides a reflective mask with high reflectivity for EUV light. A layer containing at least one metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof, can be used as the DRF layer. Si is widely used for the FRF layer, and Mo is widely used for the DRF layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are 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.

[0027] 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 materials used and the required EUV light reflectance of the multilayer reflective film. Taking a Mo / Si multilayer reflective film as an example, in order to obtain a multilayer reflective film with a maximum EUV light reflectance 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 should be stacked so that the number of repeating units is between 30 and 60. The reflectance of the multilayer reflective film for EUV light with an incident angle θ of 6° is preferably 60% or more, and more preferably 65% ​​or more.

[0028] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using known deposition methods such as DC sputtering, 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 a target made of a high refractive index material and a target made of a low refractive index material. If the multilayer reflective film is a Mo / Si multilayer reflective film, for example, it can be fabricated by ion beam sputtering in the following way: First, a Si layer of a predetermined thickness is deposited on a substrate using a Si target. Then, a Mo layer of a predetermined thickness is deposited using a Mo target. These Si and Mo layers are stacked for, for example, 30 to 60 periods (preferably 40 to 50 periods), with each period representing one cycle, to form a Mo / Si multilayer reflective film.

[0029] [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 to protect 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. It is also preferable that the protective film protects the multilayer reflective film when the hard mask film described later is removed.

[0030] The protective film preferably contains at least one element selected from the group consisting of Si, Ru, and Rh. The protective film may also preferably contain Rh. If the protective film contains Rh, the Rh content is preferably 50 atomic percent or more relative to the total atoms of the protective film. Specific examples of materials for the protective film include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Rh, Pd, Ta, and Ir, elemental Rh metal, and Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Ru, Pd, Ta, and Ir. Materials for the protective film include elemental Al metal, nitrides containing Al and N, and Al ２ O ３ Other materials can also be used. Among these, Ru metal element, Ru alloy, Rh metal element, or Rh alloy are preferred as the material for the protective film. The protective film may contain at least one element selected from the group consisting of B, C, N, and O.

[0031] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In terms of maintaining the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 1 to 10 nm or less, more preferably 1.5 to 6 nm, and even more preferably 2 to 5 nm.

[0032] 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 material described above. Also, if the protective film is a multilayer film, it is preferable that the total thickness of the multilayer film satisfies the preferred range described above. If the protective film is a multilayer film, it is preferable that the layer of the multilayer film that is located closest to the absorber film contains Rh. Also, if the layer of the multilayer film that is located closest to the absorber film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0033] The protective film can be deposited using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering.

[0034] [Absorber Film] The reflective mask blank of the present invention has an absorber film disposed on the side of the multilayer reflective film opposite to the substrate side. When the absorber film is patterned, it is required that the contrast between the EUV light reflected by the multilayer reflective film and the EUV light absorbed by the absorber film is high. The 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 and interferes with the EUV light from the multilayer reflective film to produce contrast. The absorber film pattern may be used as a binary mask as described later, or as a phase-shift mask as described later. That is, the absorber film may be a phase-shift film. The absorber film preferably contains one or more metallic elements selected from the group consisting of Ta, Cr, Nb, Ir, Co, Ni, Cu, Sn, Pt, Pd, Au, W, and Ru.

[0035] When an absorber film pattern is used 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 film may contain one or more metals selected from the group consisting of Ta, Cr, Nb, Ir, Co, Ni, Cu, Sn, Pt, Pd, Au, W, and Ru, as well as one or more elements selected from the group consisting of O, N, B, Hf, and H. In particular, it is preferable that the absorber film contains Ta and also contains N or B. By including N or B, the crystalline state of the absorber film can be made amorphous or microcrystalline. The crystalline state of the absorber film is preferably amorphous. This improves the smoothness and flatness of the absorber film. Furthermore, as the smoothness and flatness of the absorber film increase, the edge roughness of the absorber film pattern decreases, and the dimensional accuracy of the absorber film pattern can be improved. 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.

[0036] When an absorber film pattern is used as a phase shift mask, the reflectivity of the absorber film for EUV light is preferably 2% or more. To obtain a sufficient phase shift effect, the reflectivity of the absorber film is preferably 9 to 15%. When an 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 the phase shift mask include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Cr, Au, Pt, Re, Hf, Ta, 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. When an absorber film pattern is used as a phase shift mask, the film thickness of the absorber film is preferably 30 to 60 nm, and more preferably 35 to 55 nm.

[0037] The absorber film may be a single layer or a multilayer film consisting of multiple layers. If the absorber film is a single layer, the number of steps in the manufacturing of reflective mask blanks can be reduced, improving production efficiency. If the absorber film is a multilayer film, the layer located on the side of the absorber film opposite the substrate side may be a low-reflection layer that functions as an anti-reflective layer when inspecting the absorber film pattern using inspection light (e.g., wavelength 193-248 nm). Examples of materials that form the low-reflection layer include materials containing Ta and O.

[0038] Absorber films can be formed using known film deposition methods such as magnetron sputtering and ion beam sputtering. For example, when forming a TaN film as an absorber film using magnetron sputtering, a Ta target is used, and sputtering is performed by supplying a gas containing Ar gas and nitrogen gas to form the absorber film.

[0039] [Hard Mask Film] The reflective mask blank of the present invention may have a hard mask film on the side opposite to the substrate side of the absorber film. When the reflective mask blank has a hard mask film, dry etching can be performed even if the minimum line width of the absorber film pattern is reduced. Therefore, it is effective for miniaturizing the absorber film pattern.

[0040] The hard mask film preferably contains one or more metallic elements (hereinafter also referred to as "element X") selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, Ru, and Hf. The total content of element X in the hard mask film is preferably 30 atomic% or more, more preferably 50 atomic% or more, even more preferably 60 atomic% or more, and particularly preferably 70 atomic% or more, relative to the total atoms of the hard mask film. The upper limit may be 100 atomic%. That is, the hard mask film may be a film consisting only of element X. The total content of element X in the hard mask film may be 99 atomic% or less, or 95 atomic% or less.

[0041] The hard mask film may contain elements other than element X. It is also preferable that the hard mask film contain at least one element selected from the group consisting of B, N, C, and O.

[0042] Materials that constitute the hard mask film include element X, oxides of element X, nitrides, oxynitrides, carbides, carbonitrides, carbonites, fluorides, and oxyfluorides. The material constituting the hard mask film may also be a composite compound (for example, a composite oxide) containing two or more elements from among element X.

[0043] Examples of Cr-based materials containing Cr include materials containing Cr and at least one element selected from the group consisting of Cr, O, N, C, and H, and more specifically, CrO, CrN, and CrON. The notation "CrON" represents a material containing Cr, O, and N, and the following similar notations have the same meaning. Examples of Si-based materials containing Si include materials containing Si and at least one element selected from the group consisting of Si, O, N, C, and H, and more specifically, SiO ２ These include SiO, SiN, SiO, SiC, SiCO, SiCN, and SiCON.

[0044] The thickness of the hard mask film is preferably 2 nm or more. Preferably, the thickness of the hard mask film is 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less. The thickness of the hard mask film is determined by XRR.

[0045] Hard mask films can be formed using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering.

[0046] The film thickness of each film (e.g., absorber film, protective film, hard mask film) is determined by X-ray reflectivity (XRR). Rigaku's Smart Lab HTP is used for XRR measurements. CuKα rays are used as the X-ray source, with a tube voltage of 40 kV and a tube current of 30 mA. The accompanying software (GlobalFit) is used for analysis. The types and content of elements contained in each film are obtained by X-ray photoelectron spectroscopy (XPS). When measuring the types and content of elements in a given film using XPS, the layer on the opposite side of the film from the substrate is removed by sputtering or similar methods before measurement.

[0047] [Conductive Film] The reflective mask blank of the present invention may have a conductive film on the side of the substrate opposite to the multilayer reflective film side. Having a conductive film allows the reflective mask blank to be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The constituent material of the 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 material of the conductive film may be a Cr compound containing Cr and one or more selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more selected from the group consisting of B, N, O, and C. The thickness of the conductive film is preferably 10 to 1000 nm, and more preferably 10 to 400 nm. Furthermore, the 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 conductive film can adjust the reflective mask blank to be flat by balancing the stress from various films formed on the first main surface side. The conductive film can be formed using known film deposition methods, such as sputtering methods such as DC sputtering, magnetron sputtering, and ion beam sputtering, CVD, vacuum deposition, and electrolytic plating.

[0048] The reflective mask blank of the present invention can be manufactured, for example, by forming the multilayer reflective film on the substrate, forming an absorbent film on the multilayer reflective film, and attaching compound X to at least one main surface. Alternatively, if the reflective mask blank of the present invention has a protective film, it can be manufactured, for example, by forming the multilayer reflective film on the substrate, forming a protective film on the multilayer reflective film, and forming the absorbent film on the protective film. If the reflective mask blank of the present invention has a hard mask film, it may include a step of forming the hard mask film on the absorbent film. The methods for forming each film and attaching compound X are as described above.

[0049] [Cleaning Process] The reflective mask blank of the present invention is less likely to have defects remaining when subjected to the cleaning process. The cleaning process is usually performed during the manufacturing process of the reflective mask blank, before shipment of the reflective mask blank, after acceptance of the reflective mask blank after shipment, and before coating of the resist described later. The preferred cleaning method in the above cleaning process is to bring the cleaning solution into contact with the main surface of the reflective mask blank. Examples of cleaning solutions include water, nitrogen water, acidic solutions, and alkaline solutions. The nitrogen water is a solution obtained by mixing nitrogen with water (pure water is preferred, and ultrapure water is more preferred). Specific examples of the acidic solution include aqueous solutions of acidic compounds such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, and acetic acid. Specific examples of the alkaline solution include aqueous solutions of basic compounds such as ammonia, tetramethylammonium hydroxide, triethanolamine, choline, sodium hydroxide, potassium hydroxide, and cesium hydroxide. Conventional known methods such as spin cleaning, immersion of the reflective mask blank in the cleaning solution, and flowing the cleaning solution over the reflective mask blank can be used as the cleaning method. The above cleaning may also be performed while stirring the cleaning solution with ultrasound or megasonic waves.

[0050] <Method for Manufacturing a Reflective Mask and the Reflective Mask> The reflective mask of the present invention is obtained by patterning the absorbent membrane of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be explained with reference to Figures 2(a) to (d).

[0051] Figure 2(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in that order. A known method can be used to form the resist pattern 40. For example, a resist is applied to the absorber film 18 of the reflective mask blank, and exposure and development are performed to form the resist pattern 40. The resist pattern 40 corresponds to the pattern formed on the wafer using a reflective mask. Then, using the resist pattern 40 in Figure 2(a) as a mask, the absorber film 18 is etched and patterned, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 18pt shown in Figure 2(b). Next, as shown in Figure 2(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 2(b), and dry etching is performed using the resist pattern 41 in Figure 2(c) as a mask. Dry etching is performed until the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 2(d).

[0052] A dry etching method for forming the absorber film pattern 18pt includes a method using an etching gas. The etching gas may include one or more gases selected from the group consisting of F-based gases, Cl-based gases, and oxygen-based gases. An example of an F-based gas is CF ４ CHF ３ , C ２ F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ ,CH ２ F ２ ,CH ３ F, C ３ F ８ F ２ SF ６ , and NF ３ Examples of such gases, as well as mixtures thereof, include Cl. ２ SiCl ４ , CHCl ３ , CCl４ , and BCl ３ Examples of such gases, as well as mixtures thereof, include O ２ CO ２ Examples include gases such as CO and mixtures thereof. The above gases may include inert gases such as He gas, Ar gas, Kr gas, Xe gas, and nitrogen gas. The etching gas may be plasma-generated and used to etch the absorber film 18.

[0053] The resist patterns 40 and 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.

[0054] If the reflective mask blank has a hard mask film, the hard mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the hard mask film as a mask. The patterning of the hard mask film can be done by known methods, for example, dry etching with an oxygen-containing gas or a chlorine-containing gas (Cl-based gas). If the reflective mask blank has a hard mask film, a step to remove the hard mask film may be performed. In addition, the hard mask film may be removed simultaneously in the step to remove the resist pattern 40 or 41 described above. As a method for removing the hard mask film, for example, it can be done by the same method as etching the hard mask film described above.

[0055] The reflective mask obtained by patterning the absorbent film of the reflective mask blank of the present invention has fewer foreign substances after the washing process and suppresses the occurrence of defects after patterning, making it suitable for use as a reflective mask for exposure with EUV light.

[0056] The present invention will be described in detail below with reference to examples. Examples 2 to 8 are embodiments, and Examples 1 and 9 are comparative examples. However, the present invention is not limited to these examples.

[0057] [Examples 1-8] A square SiO with an outer diameter of 6 inches on each side ２ -TiO ２ A glass substrate (6 inches (152 mm) square, 6.3 mm thick) was prepared. This glass substrate has a thermal expansion coefficient of 0.2 × 10⁻⁶ －７ / °C, Young's modulus 67 GPa, Poisson's ratio 0.17, specific stiffness 3.07 × 10⁻⁶ ７ I understand ２ / s ２ The glass substrate was polished so that the surface roughness (root mean square height Sq) of the main surface was 0.15 nm or less and the flatness was 100 nm or less. Next, a conductive film was formed on one side of the glass substrate. The conductive film was a CrN film and was deposited by magnetron sputtering to a thickness of approximately 100 nm. The sheet resistance of the conductive film was 100 Ω / □. In this way, a glass substrate having a conductive film of CrN was manufactured.

[0058] Next, the glass substrate was fixed in the deposition chamber using an electrostatic chuck via an electrostatic adsorption method with a conductive film. In this state, a multilayer reflective film was deposited on the first main surface of the glass substrate. For deposition, an ion beam sputtering method was used, and a Mo / Si multilayer reflective film was formed by alternately depositing a 2.3 nm thick Mo layer and a 4.5 nm thick Si layer 50 times each. For the deposition of the Mo layer, a Mo target was used, and ion beam sputtering was performed in an Ar gas atmosphere (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the deposition rate was 3.84 nm / min. For the deposition of the Si layer, a boron-doped Si target was used, and ion beam sputtering was performed in 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 (target value) of the multilayer reflective film was (2.3 nm + 4.5 nm) × 50 times = 340 nm. The uppermost layer of the multilayer reflective film was a Si layer. Next, a protective film was formed on the multilayer reflective film by ion beam sputtering. The protective film was a Ru layer, and ion beam sputtering was performed using a Ru target in an Ar gas atmosphere (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the deposition rate was 3.12 nm / min. The thickness of the protective film was 2.5 nm.

[0059] Next, an absorber film was formed on the protective film by magnetron sputtering. First, a TaN layer was formed on the protective film. Specifically, a Ta target was used to form Kr and N ２ mixed gas (Kr = 95 vol%, N ２ Magnetron sputtering was performed under an atmosphere of 5 vol%). The deposition rate was 7.7 nm / min, and the film thickness was 75 nm. Next, a TaON layer was formed on the TaN layer by magnetron sputtering. The TaON layer corresponds to the low-reflectance layer of the absorber film. Specifically, using a Ta target, Ar, O ２ , and N ２ mixed gas (Ar = 60 vol%, O ２ = 30 vol%, N ２Magnetron sputtering was performed under a 10 vol% atmosphere. The deposition rate was 1.32 nm / min. The thickness of the TaON layer was 5 nm. This resulted in obtaining a reflective mask blank having a conductive film, a substrate, a protective film, and an absorber film in that order.

[0060] The obtained reflective mask blank was left to stand in a vapor atmosphere of compound X as described in Table 1, allowing compound X to adhere to the main surface. The amount of compound X adhered was adjusted by the standing time. The amount of compound X adhered was measured by the method described above. The amount of compound X adhered to the first main surface (the outermost surface of the TaON layer) is shown in Table 1 below. In Example 7, the ratio of compound X used when adhering compound X was C ４ H ２ O ３ / C ４ H ８ Let O = 1 / 1 (mass ratio), and in Example 8, C ５ H ６ O / C ７ H ６ O = 1 / 1 (mass ratio).

[0061] [Example 9] Compound X was not attached to the reflective mask blank, and the evaluation described below was performed as is.

[0062] <Evaluation Method and Criteria> The degree to which defects remain after the cleaning process (defect removal capability) was evaluated using the following method. Reflective mask blanks of Examples 1 to 9 were prepared by supplying nitrogen water, obtained by dissolving nitrogen in ultrapure water (resistivity value ≥ 18 MΩ·cm), through an external shower nozzle, and then ultrasonic waves (1.0 MHz, 10 W / cm) were applied to the cleaning solution. ２ The mask blanks were cleaned by propagating a solution and cleaning for 120 seconds at a cleaning solution temperature of 23°C. The amount of defects on the first main surface of the reflective mask blanks before and after cleaning was measured, and the removal rate (%) defined by the following formula was calculated. The amount of defects was measured using a Lasertec MAGICS series. Removal rate (%) = ((Amount of defects before cleaning - Amount of defects remaining after cleaning) / Amount of defects before cleaning) × 100

[0063] The defect removal performance was evaluated based on the obtained removal rate (%) according to the following evaluation criteria. In practical terms, a defect removal performance rating of B or higher is preferable. (Evaluation Criteria) A: Removal rate of 80% or more B: Removal rate of 60% or more but less than 80% C: Removal rate less than 60%

[0064] Table 1 shows the type of compound X used in each example, the amount of compound X attached to the first main surface, and the evaluation results. The correspondence between the molecular formulas and compounds in the table is as follows: ・C ２ H ５ OH: Ethanol C ４ H ２ O ３ Maleic anhydride C ４ H ８ O: Butyraldehyde C ５ H ６ O: Cyclopentenone C ７ H ６ O: Benzaldehyde C ８ H １６ O: 2-ethylhexylaldehyde

[0065]

[0066] The reflective mask blank of the present invention was confirmed to be less prone to defects caused by foreign matter after being subjected to the cleaning process (Examples 2-8). When a compound different from compound X was used (Example 1), and when compound X was not used (Example 9), it was confirmed that defects caused by foreign matter were more likely to remain after being subjected to the cleaning process. The amount of compound X adhering was 0.3-4.3 ng / cm³. ２ In this case, it was confirmed that defects originating from foreign matter, etc., were less likely to remain after the cleaning process (Examples 2-8).

[0067] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2025-009771, filed on January 23, 2025, are incorporated herein by reference as disclosure of the present invention.

[0068] 10 Reflective mask blank 10A First main surface 10B Second main surface 12 Substrate 14 Multilayer reflective film 16 Protective film 18 Absorber film 18pt Absorber film pattern 40, 41 Resist pattern

Claims

1. A reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light, and an absorber film in this order, wherein a compound having carbonyl groups with 4 to 8 carbon atoms is attached to at least one of the two main surfaces of the reflective mask blank.

2. The amount of the compound adhering to each of the at least one main surface is 0.03 to 5.4 ng / cm². ２ The reflective mask blank according to claim 1.

3. The amount of the compound adhering to each of the at least one main surface is 0.3 to 4.3 ng / cm². ２ A reflective mask blank according to claim 1 or 2.

4. The reflective mask blank according to claim 1 or 2, wherein the compound is at least one compound selected from the group consisting of maleic anhydride, butyraldehyde, cyclopentenone, benzaldehyde, 2-ethylhexylaldehyde, cyclopentanone, methylcyclopentenone, and dimethylcyclopentanone.

5. The reflective mask blank according to claim 1 or 2, wherein the absorbent film contains one or more metallic elements selected from the group consisting of Ta, Cr, Nb, Ir, Co, Ni, Cu, Sn, Pt, Pd, Au, W, and Ru.

6. The reflective mask blank according to claim 1 or 2, wherein the reflective mask blank has a protective film between the multilayer reflective film and the absorber film, and the protective film contains at least one element selected from the group consisting of Si, Ru, and Rh.

7. The reflective mask blank according to claim 1 or 2, wherein the reflective mask blank has a conductive film on the side of the substrate opposite to the multilayer reflective film side, and the conductive film comprises Cr and one or more elements selected from the group consisting of B, N, O, and C.

8. The reflective mask blank according to claim 1 or 2, wherein the reflective mask blank has a conductive film on the side of the substrate opposite to the multilayer reflective film side, and the conductive film comprises Ta and one or more elements selected from the group consisting of B, N, O, and C.

9. A reflective mask having an absorbent film pattern formed by patterning the absorbent film of the reflective mask blank described in claim 1 or 2.

10. A method for manufacturing a reflective mask, comprising the step of patterning the absorbent film of the reflective mask blank according to claim 1 or 2.

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