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

Abstract

To provide a reflective mask blank containing Pt and having low crystallinity.SOLUTION: A reflective mask blank comprising a substrate, a multilayer reflective film that reflects EUV light, a protective film, and a phase shift film that phase-shifts EUV light in this order, wherein the phase shift film comprises Pt and a first element X1 of at least one selected from the group consisting of Cr, Hf, Ta, and W, A content of the first element X1 in the phase shift film is 10.0 atom% or more and less than 70.0 atom% with respect to all atoms of the phase shift film, and a chemical shift of a peak corresponding to a 4f7 / 2 orbit of Pt is 0. 3eV or more when the phase shift film is analyzed by X-ray photoelectron spectrometry.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, in order to further miniaturize semiconductor devices, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been considered.

[0003] Due to the characteristics of EUV light, EUV exposure uses a reflective optical system and a reflective mask. A 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 a reflective mask from the illumination optical system of an exposure tool is reflected by areas without an absorber film (openings) and absorbed by areas with an absorber film (non-openings). As a result, the mask pattern is transferred as a resist pattern onto a wafer through the reduced projection optical system of the exposure tool, and subsequent processing is carried out. The absorber film may also be a phase shift film, which shifts the phase of EUV light to reduce the reflectance of EUV light. The phase shift film reduces the reflectance of EUV light by causing interference between the EUV light reflected by the surface of the absorber film opposite the multilayer reflective film side and the EUV light reflected by the surface of the absorber film facing the multilayer reflective film side. As such a phase shift film, in terms of optical properties, for example, Patent Document 1 discloses a phase shift film containing platinum (Pt). More specifically, it discloses an absorber film (phase shift film) made of Pt. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 065421 Summary of the Invention [Problem to be solved by the invention]

[0006] In the phase shift film of a reflective mask blank, low crystallinity is required in order to suppress variations in line width during patterning, in addition to the optical properties of the constituent materials. When the present inventors investigated the Pt-containing phase shift film described in Patent Document 1, they found that it had high crystallinity, and it was desired to reduce this.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a reflective mask blank that contains Pt and has low crystallinity. Another object of the present invention is to provide a reflective mask and a method for manufacturing the reflective mask. [Means for solving the problem]

[0008] As a result of intensive research into the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by including a specific metal element and a specific light element in a predetermined ratio, and thus completed the present invention. That is, the inventors have found that the above problems can be solved by the following configuration. [1] A substrate; A multilayer reflective film that reflects EUV light, A protective film; a phase shift film that shifts the phase of EUV light, in this order, The phase shift film is made of Pt and and one or more first elements X1 selected from the group consisting of Cr, Hf, Ta, and W, the content of the first element X1 in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % with respect to all atoms in the phase shift film; When the phase shift film was analyzed by X-ray photoelectron spectroscopy, the 4f7 / 2 A reflective mask blank in which the chemical shift of the peak corresponding to the orbital is 0.3 eV or more. [2] The reflective mask blank according to [1], wherein the content of Pt in the phase shift film is 30.0 atomic % or more and less than 90.0 atomic % based on all atoms in the phase shift film. [3] The first element X1 includes at least Ta, The reflective mask blank according to [1] or [2], wherein the content of Ta in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % based on the total atoms in the phase shift film. [4] The first element X1 contains at least W, The reflective mask blank according to [1] or [2], wherein the content of W in the phase shift film is 10.0 to 40.0 atomic % based on the total atoms in the phase shift film. [5] The first element X1 contains at least Hf, The reflective mask blank according to [1] or [2], wherein the content of Hf in the phase shift film is 10.0 to 60.0 atomic % based on the total atoms in the phase shift film. [6] The reflective mask blank according to any one of [1] to [5], wherein the phase shift film has a refractive index n of 0.910 or more. [7] The reflective mask blank according to any one of [1] to [6], wherein the phase shift film has an extinction coefficient of less than 0.050. [8] The reflective mask blank according to any one of [1] to [7], wherein the phase shift film is amorphous. [9] The reflective mask blank according to any one of [1] to [8], wherein the phase shift film has a thickness of 10 to 60 nm.

[10] The reflective mask blank according to any one of [1] to [9], wherein the protective film contains one or more elements selected from the group consisting of Si, Y, Ru, Rh, Pd, and Al.

[11] An etching mask film different from the phase shift film is further provided on the opposite side of the phase shift film from the substrate side, The reflective mask blank according to any one of [1] to

[10] , wherein the etching mask film contains one or more elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf.

[12] The reflective mask blank according to

[11] , wherein the etching mask film further contains one or more elements selected from the group consisting of B, C, N, O, and F.

[13] A reflective mask having a phase shift film pattern formed by patterning the phase shift film of the mask blank according to any one of [1] to

[12] .

[14] A method for producing a reflective mask, comprising the step of patterning the phase shift film of the reflective mask blank according to any one of [1] to

[12] . [Effects of the Invention]

[0009] According to the present invention, a reflective mask blank containing Pt and having low crystallinity can be provided. The present invention also provides a reflective mask and a method for manufacturing the reflective mask. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of an embodiment of a reflective mask blank of the present invention. [Figure 2] 1A to 1C are schematic diagrams showing an example of a manufacturing process for a reflective mask using a reflective mask blank of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0012] The meaning of each description in this specification is as follows. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, elements such as boron, carbon, nitrogen, oxygen, aluminum, silicon, titanium, chromium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, tantalum, tungsten, hafnium, rhenium, iridium, and platinum may be represented by their corresponding element symbols (B, C, N, O, Al, Si, Ti, Cr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Hf, Re, Ir, and Pt, etc.).

[0013] <Reflective mask blank> The reflective mask blank of the present invention is a reflective mask blank having, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film, and a phase shift film that shifts the phase of EUV light. In the reflective mask blank of the present invention, the phase shift film contains Pt and one or more first elements X1 selected from the group consisting of Cr, Hf, Ta, and W. The content of the first elements X1 in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % with respect to all atoms in the phase shift film. Furthermore, when the phase shift film of the reflective mask blank of the present invention was analyzed by X-ray photoelectron spectroscopy, the 4f 7 / 2 The chemical shift of the peak corresponding to the orbital is 0.3 eV or more. The reflective mask blank of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a cross-sectional view showing one example of an embodiment of the reflective mask blank of the present invention. The reflective mask blank 10 shown in Fig. 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18, in this order. The phase shift film 18 contains Pt and the first element X1, the content of the first element X1 being within a predetermined range, and the chemical shift of the Pt being 0.3 eV or more. Furthermore, the reflective mask blank 10 may have an etching mask film, which will be described later, on the side of the absorber film 18 opposite to the substrate 12 side.

[0015] The mechanism by which the crystallinity of the phase shift film of the reflective mask blank of the present invention decreases is not entirely clear, but the present inventors speculate as follows. It is believed that the phase shift film in the reflective mask blank of the present invention contains Pt and also a predetermined amount of the first element X1, which tends to result in low crystallinity. In addition, in the phase shift film of the reflective mask blank of the present invention, 4f of Pt 7 / 2 The chemical shift of the peak corresponding to the orbital is 0.3 eV or more. The chemical shift of Pt in the above range indicates that it is affected by the first element X1, and is thought to correspond to the presence of a large amount of the first element X1 around Pt. This means that the proportion of Pt atoms adjacent to each other is small, and as a result, it is thought that the crystallinity is further reduced.

[0016] The structure of the reflective mask blank of the present invention will be described below. [substrate] The substrate of the reflective mask blank of the present invention preferably has a small thermal expansion coefficient, which can prevent distortion of the phase shift film pattern due to heat generated during exposure to EUV light. The thermal expansion coefficient of the substrate is 0±1.0×10 at 20℃. -7 / ℃ is preferred, 0±0.3×10 -7 / °C is more preferred. Materials with a low thermal expansion coefficient include SiO2-TiO2-based glass, but are not limited to this. Substrates such as crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, and metal can also be used. The SiO2-TiO2-based glass preferably uses silica 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 linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. Note that the SiO2-TiO2-based glass may contain trace components other than SiO2 and TiO2.

[0017] The surface of the substrate on which the multilayer reflective film is to be laminated (hereinafter also referred to as the "first principal surface") preferably has high surface smoothness. The surface smoothness of the first principal surface can be evaluated by surface roughness. The surface roughness of the first principal surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. The surface roughness can be measured using an atomic force microscope, and will be described as the root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to have a predetermined flatness, which improves the pattern transfer accuracy and positional accuracy of a reflective mask obtained using the reflective mask blank. In a predetermined region of the first main surface (e.g., a 132 mm × 132 mm region), 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. The flatness can be measured using a Fujinon flatness measuring instrument. The size and thickness of the substrate are determined appropriately depending on the design values ​​of the mask, etc. For example, the outer shape is 6 inches (152 mm) square and the thickness is 0.25 inches (6.3 mm). The substrate is often rectangular or square. Furthermore, the substrate preferably has high rigidity to prevent deformation due to film stress of films (such as a multilayer reflective film, a protective film, and a phase shift film) formed on the substrate. For example, the substrate preferably has a Young's modulus of 65 GPa or more.

[0018] [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 high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more.

[0019] Multilayer reflective films can achieve high reflectivity for EUV light, so multilayer reflective films are usually used that are made by alternately stacking high-refractive index layers that have a high refractive index for EUV light and low-refractive index layers that have a low refractive index for EUV light multiple times. The multilayer reflective film may be formed by stacking multiple periods, each period being a stack structure in which a high refractive index layer and a low refractive index layer are stacked in this order from the substrate side, or may be formed by stacking multiple periods, each period being a stack structure in which a low refractive index layer and a high refractive index layer are stacked in this order. The high refractive index layer can be a layer containing Si. As the Si-containing material, in addition to simple Si, a Si compound containing Si and one or more elements selected from the group consisting of B, C, N, and O can be used. By using a high refractive index layer containing Si, a reflective mask with excellent reflectance to EUV light can be obtained. The low refractive index layer may be a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof. Si is commonly used for the high-refractive index layer, and Mo is commonly used for the low-refractive index layer. That is, Mo / Si reflective multilayer films are the most common. However, the reflective multilayer film is not limited to this, and Ru / Si reflective multilayer films, Mo / Be reflective multilayer films, Mo compound / Si compound reflective multilayer films, Si / Mo / Ru reflective multilayer films, Si / Mo / Ru / Mo reflective multilayer films, Si / Ru / Mo reflective multilayer films, and Si / Ru / Mo / Ru reflective multilayer films can also be used.

[0020] The thickness of each layer constituting the multilayer reflective film and the number of layer repeat units can be appropriately selected depending on the film material used and the EUV light reflectivity required for the reflective layer. Taking a Mo / Si multilayer reflective film as an example, to obtain 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 can be laminated so that the number of repeat units is 30 to 60.

[0021] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using a known deposition method, such as magnetron sputtering or ion beam sputtering. For example, when a multilayer reflective film is fabricated using ion beam sputtering, ion particles are supplied from an ion source to a target of a high refractive index material and a target of a low refractive index material. When the multilayer reflective film is a Mo / Si multilayer reflective film, for example, a Si layer with a predetermined thickness is first deposited on a substrate using an ion beam sputtering method, for example, using a Si target. Then, a Mo layer with a predetermined thickness is deposited using a Mo target. This Si layer and Mo layer constitute one cycle, and the Mo / Si multilayer reflective film is formed by stacking, for example, 30 to 60 cycles.

[0022] [Protective film] The reflective mask blank of the present invention has a protective film between the multilayer reflective film and the phase shift film, which is provided for the purpose of protecting the multilayer reflective film from damage during an etching process (usually a dry etching process) to form a pattern on the phase shift film. The protective film preferably contains one or more elements selected from the group consisting of Si, Y, Ru, Rh, Pd, and Al, and more preferably contains at least one element selected from the group consisting of Ru and Rh.

[0023] Examples of materials containing Si include Si oxides, Si nitrides, Si oxynitrides, and alloys containing Si. Examples of materials containing Y include Y oxide, Y fluoride, Y oxyfluoride, and Y-containing alloys.

[0024] Examples of materials containing Ru include simple Ru metal and Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Ti, Nb, Rh, and Zr. Examples of materials containing Rh include Rh metal alone, Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Ti, Nb, Ru, Ta, and Zr, Rh-containing nitrides containing the above-mentioned Rh alloys and nitrogen, and Rh-containing oxynitrides containing the above-mentioned Rh alloys, nitrogen, and oxygen. Examples of materials containing Pd include simple Pd metal and Pd alloys containing Pd and one or more metals selected from the group consisting of Si, Ti, Zr, Nb, Ru, Rh, and Ta.

[0025] Further, examples of materials that can achieve the above object include Al and nitrides containing these metals and nitrogen, and Al2O3. Among these, materials that can achieve the above object are preferably Ru metal alone, Ru alloys, Rh metal alone, or Rh alloys. As the Ru alloy, a Ru—Si alloy is preferred, and as the Rh alloy, a Rh—Si alloy is preferred.

[0026] The thickness of the protective film is not particularly limited as long as it can 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 Ru metal alone, a Ru alloy, Rh metal alone, or a Rh alloy, and that the thickness of the protective film is the above-mentioned preferable thickness.

[0027] The protective film may be a film consisting of a single layer, or a multilayer film consisting of multiple layers. When the protective film is a multilayer film, each layer constituting the multilayer film is preferably made of the above-mentioned preferred material. Furthermore, when the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the above-mentioned preferred range.

[0028] The protective film can be formed by a known film formation method such as magnetron sputtering, ion beam sputtering, etc. When forming a Ru film by magnetron sputtering, it is preferable to use a Ru target as the target and Ar gas as the sputtering gas.

[0029] [Phase shift film] The phase shift film of the reflective mask blank of the present invention contains Pt and one or more first elements X1 selected from the group consisting of Cr, Hf, Ta, and W. The content of the first elements X1 in the phase shift film is 10 atomic % or more and less than 70 atomic % with respect to all atoms in the phase shift film. Furthermore, when the phase shift film of the reflective mask blank of the present invention was analyzed by X-ray photoelectron spectroscopy, the 4f 7 / 2 The chemical shift of the peak corresponding to the orbital is 0.3 eV or more. The phase shift film will be described in detail below.

[0030] The content of the first element X1 in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % based on the total atoms in the phase shift film. The content of the first element X1 in the phase shift film is preferably 15.0 to 65.0 atomic %, more preferably 20.0 to 60.0 atomic %, still more preferably 30.0 to 50.0 atomic %, and particularly preferably 40.0 to 50.0 atomic % based on the total atoms in the phase shift film. The content of the first element X1 in the phase shift film is determined by analysis using X-ray photoelectron spectroscopy (XPS). The detailed analysis method will be described later. The first element X1 is at least one element selected from the group consisting of Cr, Hf, Ta, and W, and is preferably at least one element selected from the group consisting of Hf, Ta, and W. The phase shift film may contain only one type of first element X1, or two or more types. When the phase shift film contains two or more types of first elements X1, the content of the first elements X1 refers to the total content of each of the first elements X1.

[0031] When the first element X1 includes at least Ta, the optical properties against EUV light become more excellent and the crystallinity becomes lower. Therefore, the content of Ta in the phase shift film is preferably 10.0 atomic % or more and less than 70.0 atomic %, more preferably 20.0 to 60.0 atomic %, further preferably 30.0 to 50.0 atomic %, and particularly preferably 33.0 to 45.0 atomic %, based on the total atoms in the phase shift film. Furthermore, when the first element X1 contains at least W, the content of W in the phase shift film is preferably 5.0 to 60.0 atomic %, more preferably 10.0 to 40.0 atomic %, further preferably 11.0 to 20.0 atomic %, and particularly preferably 11.0 to 15.0 atomic %, based on the total atoms in the phase shift film, in order to improve the optical properties against EUV light and reduce the crystallinity. Furthermore, when the first element X1 contains at least Hf, the content of Hf in the phase shift film is preferably 5.0 atomic % or more and less than 70.0 atomic %, more preferably 10.0 to 60.0 atomic %, and even more preferably 15.0 to 40.0 atomic %, based on the total atoms in the phase shift film, in order to improve the optical properties against EUV light and reduce the crystallinity.

[0032] The Pt content in the phase shift film is preferably 30.0 atomic % or more, more preferably 40.0 atomic % or more, and even more preferably 50.0 atomic % or more, based on the total atoms in the phase shift film. The upper limit of the Pt content in the phase shift film is preferably less than 90.0 atomic %, more preferably 80.0 atomic % or less, even more preferably 70.0 atomic % or less, and particularly preferably 60.0 atomic % or less, based on the total atoms in the phase shift film. The Pt content in the phase shift film is determined by XPS analysis, the details of which will be described later.

[0033] In addition, when the phase shift film was analyzed by XPS, the 4f 7 / 2 The chemical shift of the peak corresponding to the orbital is 0.3 eV or more. The chemical shift may be 0.4 eV or more, 0.5 eV or more, or 0.7 eV or more. The upper limit of the chemical shift is not particularly limited, but is often 1.5 eV or less, and more often 1.2 eV or less. The XPS analysis in this specification will be described below.

[0034] For the XPS analysis, an analytical instrument "PHI 5000 VersaProbe" manufactured by ULVAC-PHI, Inc. is used. The instrument is calibrated in accordance with JIS K 0145. First, a measurement sample of approximately 1 cm square is cut out from a reflective mask blank, and the obtained measurement sample is set in a measurement holder so that the phase shift film side becomes the measurement surface. After loading the measurement holder into the above-mentioned equipment, a portion of the phase shift film is removed by 5 nm from the top surface using an argon ion beam. If the phase shift film is not exposed, the above removal is continued until the phase shift film is exposed, and then a portion of the phase shift film is removed by 5 nm from the top surface. The sputtering rate during this removal can be measured using a separately prepared sample. After removing the top surface of the phase shift film, the removed area is irradiated with X-rays (monochromated AlKα rays) and analyzed at a photoelectron take-off angle (the angle between the surface of the measurement sample and the direction of the detector) of 45°. During the analysis, a neutralization gun is used to suppress charge buildup. The analysis involves a wide scan in the binding energy range of 1,000 to 0 eV to confirm the elements present, followed by a narrow scan depending on the elements present (e.g., Pt and the first element X1). The narrow scan is performed with a pass energy of 58.7 eV, an energy step of 0.1 eV, a time step of 50 ms, and 10 accumulations. The wide scan is performed with a pass energy of 58.7 eV, an energy step of 1 eV, a time step of 50 ms, and 2 accumulations. Here, the binding energy is calibrated using the peak of the C1s orbital derived from carbon present on the measurement sample. Specifically, before removing 5 nm of a portion of the phase shift film from the outermost surface with an argon ion beam, the binding energy value indicating the peak of the C1s orbital in the measurement sample is obtained from the narrow scan analysis results, and the value obtained by subtracting this binding energy value from 284.8 eV is used as the shift value. The above shift value is added to the binding energy value indicating the peak of each orbital of each element obtained from the narrow scan analysis results to calculate the binding energy value of each peak. The chemical shift of each peak refers to the deviation from the value of each peak in the literature. In this specification, the 4f of Pt is 7 / 2 The peak value corresponding to the orbital is 71.1 eV. In this specification, the chemical shift is expressed as a positive value when it is a shift toward a higher binding energy side, and as a negative value when it is a shift toward a lower binding energy side.

[0035] When the phase shift film contains carbon, the binding energy is calibrated using gold whose surface has been cleaned in an ultra-high vacuum. 7 / 2 The binding energy value of the orbital is obtained from the narrow scan analysis results and is calculated by subtracting the binding energy value from 83.96 eV. When reading the binding energy value indicating the peak of each orbital from the narrow scan analysis results, the value indicating the peak top is read as the binding energy value.

[0036] The contents of Pt and the first element X1 are analyzed using the relative sensitivity coefficients specific to each element and each orbital from the spectrum obtained by narrow scanning when XPS analysis is performed according to the above procedure.

[0037] The absolute value of the chemical shift of the first element X1 is preferably 0.1 eV or more, more preferably 0.2 eV or more, and even more preferably 0.3 eV or more. The chemical shift may be 0.5 eV or more, 0.8 eV or more, 1.0 eV or more, or even 1.5 eV or more. The upper limit of the chemical shift is not particularly limited, but is often, for example, 2.0 eV or less. The chemical shift of the first element X1 is the 4f of Pt. 7 / 2 It is determined in the same manner as the chemical shift of the peak corresponding to the orbital. When the first element X1 contains Cr, the 2p orbital is used. When the first element X1 contains Hf, Ta, or W, the 4f orbital is used. The detailed method will be explained later in the Examples section.

[0038] The phase shift film may contain elements other than Pt and the first element X1, such as one or more elements selected from the group consisting of B, C, N, O, and Si. The phase shift film may contain only one kind of the other elements, or two or more kinds of the other elements.

[0039] When the phase shift film contains the other elements, the content of the other elements is preferably more than 0.0 atomic % and not more than 10.0 atomic %, more preferably more than 0.0 atomic % and not more than 5.0 atomic %, based on all atoms in the phase shift film. It is also preferable that the phase shift film does not contain any of the other elements, that is, it is also preferable that the phase shift film is made of Pt and the first element X1.

[0040] The refractive index n of the phase shift film is preferably 0.900 or more, more preferably 0.910 or more, and is preferably 0.950 or less, more preferably 0.940 or less, even more preferably 0.930 or less, and particularly preferably 0.920 or less, in order to make the thickness of the phase shift film thinner. The extinction coefficient k of the phase shift film is preferably less than 0.060, more preferably less than 0.050, and even more preferably 0.048 or less. The extinction coefficient k of the phase shift film is preferably 0.035 or more, more preferably 0.040 or more, and even more preferably 0.042 or more, in order to facilitate adjustment of the reflectance of the phase shift film to a lower value. The refractive index n and extinction coefficient k are determined by measuring the incidence angle dependency of reflectance using EUV light with a wavelength of 13.5 nm and performing fitting on the obtained profile using the refractive index n and extinction coefficient k as parameters.

[0041] The reflectance of the phase shift film to EUV light is preferably 2% or more, and in order to obtain a sufficient phase shift effect, the reflectance of the phase shift film is preferably 9 to 15%.

[0042] The phase shift film of the reflective mask blank of the present invention has low crystallinity. Low crystallinity of a phase shift film refers to a small crystallite diameter calculated using a diffraction chart obtained by X-ray diffraction (XRD). The crystallite diameter is calculated using Scherrer's equation. The full half-width of the diffraction peak with the highest intensity in the 2θ range of 30 to 55° is used to calculate the crystallite diameter using Scherrer's equation. If no clear diffraction peak is observed in the diffraction chart, the phase shift film is considered to be amorphous. In the present invention, the crystallite diameter of the phase shift film is preferably 10.0 nm or less, more preferably 6.0 nm or less, and even more preferably 4.0 nm or less. There is no particular lower limit to the crystallite diameter, but it is often 0.1 nm or more. The phase shift film of the present invention may also be amorphous.

[0043] The thickness of the phase shift film is preferably 10 to 60 nm, more preferably 20 to 60 nm The thickness of the phase shift film is determined by X-ray reflectivity.

[0044] The phase shift film preferably has resistance to dissolution in cleaning solutions. When the phase shift film has resistance to dissolution in cleaning solutions, the phase shift film is less likely to be removed during the etching process of the etching mask film described later, making it easier to obtain a desired pattern. More specifically, it is preferable that the change in thickness of the phase shift film is small when the phase shift film is brought into contact with a sulfuric acid-hydrogen peroxide aqueous solution (SPM). For example, when the phase shift film is etched with SPM at 100°C for 20 minutes, the change in film thickness before and after the etching process is preferably 1.0 nm or less, more preferably 0.5 nm or less, and even more preferably 0.2 nm or less. The specific conditions for the etching treatment are as described in the examples below. In order to improve the resistance of the phase shift film to dissolution by the cleaning solution, the phase shift film preferably contains Ta as the first element X1. The content of Ta in the phase shift film may fall within the above-mentioned preferred range.

[0045] The phase shift film can be formed by known film formation methods such as magnetron sputtering, ion beam sputtering, etc. For example, when a PtTa film is formed as the phase shift film by magnetron sputtering, a Pt target and a Ta target are used, and a gas containing Ar gas is supplied to perform sputtering from each target, thereby forming the phase shift film. Furthermore, when forming a PtTa film, the target used for sputtering may be, for example, a Pt—Ta alloy target (PtTa target), that is, an alloy target containing Pt and the first element X1.

[0046] [Etching mask film] The reflective mask blank of the present invention may have an etching mask film on the side of the phase shift film opposite to the substrate side. The etching mask film is preferably made of a material that is highly resistant to dry etching. When an etching mask film is formed on a phase shift film, dry etching can be performed even if the minimum line width of the phase shift film pattern is small. Therefore, this is effective for miniaturizing the phase shift film pattern.

[0047] The etching mask film preferably contains one or more elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf (hereinafter also referred to as "third element X3"). That is, the material constituting the etching mask film preferably contains the third element X3. It is also preferable that the etching mask film further contains one or more elements selected from the group consisting of B, C, N, O and F. Examples of materials constituting the etching mask film include a simple substance of the third element X3, and borides, oxides, nitrides, oxynitrides, carbides, carbonitrides, carbonates, fluorides, and oxyfluorides of the third element X3. Note that the material constituting the etching mask film may be a composite compound (e.g., a composite oxide) containing two or more elements of the third element X3.

[0048] For example, Cr-based materials containing Cr as the third element X3 include materials containing Cr and one or more elements selected from the group consisting of Cr and O, N, C, and H, and more specifically, include CrO, CrN, and CrON. Note that the notation "CrON" represents a material containing Cr, O, and N, and similar notations below have the same meaning. Furthermore, examples of the Si-based material containing Si as the third element X3 include materials containing Si and one or more elements selected from the group consisting of O, N, C, and H, and more specifically, examples thereof include SiO, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON.

[0049] [Conductive film] The reflective mask blank of the present invention may have a conductive film on the surface (second main surface) opposite to the first main surface of the substrate. By providing the conductive film, the reflective mask blank can be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance, for example, preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The conductive film may be made of a wide range of materials, including those described in known literature. For example, the high-dielectric-constant coating described in JP-A-2003-501823, specifically a coating made of Si, Mo, Cr, CrON, or TaSi, may be used. The conductive film may also be made of 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 is preferably 10 to 1,000 nm, more preferably 10 to 400 nm. The conductive film may also have a function of adjusting 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 by a known film formation method, for example, a sputtering method such as magnetron sputtering or ion beam sputtering, a CVD method, a vacuum deposition method, or an electrolytic plating method.

[0050] [Other membranes] The reflective mask blank of the present invention may have other films. The other films include, for example, an anti-reflection film used when inspecting an absorber film pattern using inspection light (for example, wavelength 193 to 248 nm). The anti-reflection film is preferably disposed on the side opposite to the substrate side of the phase shift film.

[0051] <Reflective mask manufacturing method and reflective mask> A reflective mask can be obtained by patterning the phase shift film of the reflective mask blank of the present invention. One example of a method for producing a reflective mask will be described with reference to FIG.

[0052] 2A shows a state in which a resist pattern 40 is formed on a reflective mask blank having a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18 in this order. The resist pattern 40 can be formed by a known method, for example, by applying a resist to the phase shift film 18 of the reflective mask blank, and then exposing and developing the resist to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Thereafter, using resist pattern 40 of FIG. 2A as a mask, phase shift film 18 is etched and patterned, and resist pattern 40 is removed to obtain a laminate having phase shift film pattern 18pt shown in FIG. 2B. Next, as shown in Fig. 2C, a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate of Fig. 2B, and dry etching is performed using the resist pattern 41 of Fig. 2C as a mask. Dry etching is performed until it reaches the substrate 12. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Fig. 2D.

[0053] The dry etching used to form the phase shift film pattern 18pt may be, for example, dry etching using a Cl-based gas or dry etching using an F-based gas. The resist pattern 40 or 41 may be removed by a known method, such as removal with a cleaning solution, such as sulfuric acid-hydrogen peroxide solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide solution (APM), OH radical cleaning water, or ozone water. When the reflective mask blank has an etching mask film as another film, the etching mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the etching mask film as a mask. When the reflective mask blank has an etching mask film as another film, a step of removing the etching mask film may be performed in the step of obtaining the reflective mask. Furthermore, the etching mask film may be removed simultaneously in the step of removing the resist pattern 40 or 41 described above.

[0054] A reflective mask obtained by patterning the phase shift film of the reflective mask blank of the present invention can be suitably used as a reflective mask for exposure to EUV light. [Example]

[0055] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples. Examples 1 to 4 described below are working examples, and Example 5 is a comparative example.

[0056] <Example 1> The procedure for obtaining the reflective mask blank of Example 1 will be described as a representative example.

[0057] [substrate] First, a SiO2-TiO2 glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared as a substrate. This glass substrate has a thermal expansion coefficient of 0.02 × 10 at 20 °C. -7 / °C, Young's modulus is 67 GPa, Poisson's ratio is 0.17, and specific stiffness is 3.07 × 10 7 m 2 / s 2The quality assurance area of ​​the first main surface of the substrate was polished to a root-mean-square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less. A 100 nm thick Cr film was formed on the second main surface of the substrate using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / □.

[0058] [Multilayer reflective film] Next, a Mo / Si multilayer reflective film was formed on the first main surface of the substrate as a multilayer reflective film. The Mo / Si multilayer reflective film was obtained by repeating the process of depositing a Si film (4.5 nm thick) and a Mo film (2.3 nm thick) using ion beam sputtering 40 times, and after the 40th Mo film was formed, an additional Si film (4.5 nm thick) was deposited. The total thickness of the Mo / Si multilayer reflective film was 276.5 nm ((4.5 nm + 2.3 nm) × 40 + 4.5 nm).

[0059] [Protective film] A Ru film (thickness: 0.9 nm) was formed as a protective film on the multilayer reflective film by ion beam sputtering, and a Rh film (thickness: 1.6 nm) was formed on the formed Ru film by ion beam sputtering.

[0060] [Phase shift film] A PtTaW film (phase shift film) was formed on the protective film using a multi-target magnetron sputtering system under the following conditions: Targets: Pt target, Ta target and W target Sputtering gas: Ar gas Film formation pressure: 0.3 Pa Input power: 12~120W Deposition speed: 0.3nm / sec Film thickness: 30 nm Each target was discharged using a DC power supply, and the power input to each target was adjusted to form a film having the composition shown in the table below.

[0061] <Example 2 to Example 4> Reflective mask blanks of each example were obtained in the same manner as in Example 1, except that the type of target and input power were adjusted to form phase shift films (Examples 2 to 4) having the compositions shown in the table below.

[0062] <Example 5> A reflective mask blank for each example was obtained in the same manner as in Example 1, except that the target to which power was applied was a Pt target only, and a phase shift film made of Pt only (Example 5) was formed.

[0063] <Measurement> [XPS] The phase shift film formed using the method described above was analyzed by XPS. The table below shows the composition of the phase shift film and the chemical shift of each element. For the chemical shift of each element, the peak values ​​corresponding to the following orbitals were calculated. Note that the binding energy in parentheses is the peak value of the reference binding energy. Hf: 4f of Hf 7 / 2 Peak corresponding to the orbital (14.3 eV) Ta: 4f of Ta 7 / 2 Peak corresponding to the orbital (21.8 eV) W:W 4th floor 7 / 2 Peak corresponding to the orbital (31.5 eV)

[0064] [Optical properties] The optical properties of the phase shift film formed using the method described above were obtained. The refractive index n and extinction coefficient k for EUV light are shown in the table below.

[0065] [Crystallite diameter] The crystallite diameter of the phase shift film was measured by the method described above, and the results are shown in the table below. In each example, in order to exclude the overlap of the diffraction lines from the Mo layer of the multilayer reflective film from the crystallinity evaluation, the crystallite diameter of the phase shift film of each example was obtained by using a sample obtained by forming a phase shift film on a Si wafer under the same conditions as above.Here, the crystallite diameter of the phase shift film formed on the Si wafer and the crystallite diameter of the phase shift film in the reflective mask blank obtained by the above procedure are sufficiently corresponding. In practical terms, the crystallite size is preferably 10 nm or less, more preferably 6.0 nm or less, and even more preferably 4.0 nm or less.

[0066] [SPM resistance] The SPM resistance of the phase shift film formed on the reflective mask blank was evaluated by the following method. First, an etching treatment was performed by contacting the phase shift film with SPM (75% by volume of concentrated sulfuric acid, 25% by volume of hydrogen peroxide solution) at 100°C for 20 minutes. After the etching treatment, the thickness of the phase shift film was measured by XRR. For the XRR measurements, a Rigaku Smart Lab HTP was used. The X-ray source used was CuKα radiation, with a tube voltage of 40 kV and a tube current of 30 mA. The accompanying software (GlobalFit) was used for analysis. The table below shows the change in thickness of the phase shift film before and after the etching process, where negative values ​​indicate a decrease in thickness of the phase shift film. The absolute value of the change in film thickness before and after the etching treatment is preferably 1.0 nm or less, more preferably 0.5 nm or less, and even more preferably 0.2 nm or less.

[0067] <Result> The composition of the phase shift film formed on the reflective mask blank of each example and the results of each measurement are shown in the table.

[0068] [Table 1]

[0069] From the results of Examples 1 to 4 shown in Table 1, it can be seen that the phase shift film contains Pt and the first element X1, the content of the first element X1 in the phase shift film is 10 atomic % or more and less than 70.0 atomic % with respect to the total atoms in the phase shift film, and when analyzed by XPS, the 4f 7 / 2 It was confirmed that when the chemical shift of the peak corresponding to the orbital is 0.3 eV or more, the crystallite size is small and the crystallinity is low. On the other hand, the results of Example 5 show that the crystallinity of the phase shift film containing only Pt did not decrease. A comparison of Examples 1 and 2 with Examples 3 and 4 confirmed that when the first element X1 contains at least Ta and the Ta content in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % with respect to all atoms in the phase shift film, the phase shift film has excellent SPM resistance.

[0070] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-199954, filed on November 27, 2023, are hereby incorporated by reference as the disclosure of the specification of the present invention. [Explanation of symbols]

[0071] 10 Reflective mask blanks 12 PCB 14 Multilayer reflective film 16 Protective film 18 Phase shift film 18pt phase shift film pattern 22 Conductive film 40,42 Resist pattern

Claims

1. A substrate; a multilayer reflective film that reflects EUV light; A protective film; a phase shift film that shifts the phase of EUV light, in this order, The phase shift film is made of Pt and and one or more first elements X1 selected from the group consisting of Cr, Hf, Ta, and W, the content of the first element X1 in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % with respect to all atoms in the phase shift film, When the phase shift film was analyzed by X-ray photoelectron spectroscopy, the 4f ７／２ A reflective mask blank, wherein the chemical shift of the peak corresponding to the orbital is 0.3 eV or more.

2. 2. The reflective mask blank according to claim 1, wherein the content of Pt in the phase shift film is 30.0 atomic % or more and less than 90.0 atomic % with respect to all atoms in the phase shift film.

3. the first element X1 includes at least Ta, 3. The reflective mask blank according to claim 1, wherein the content of Ta in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % based on all atoms in the phase shift film.

4. the first element X1 includes at least W, 3. The reflective mask blank according to claim 1, wherein the content of W in said phase shift film is 10.0 to 40.0 atomic % based on the total atoms in said phase shift film.

5. the first element X1 includes at least Hf, 3. The reflective mask blank according to claim 1, wherein the content of Hf in said phase shift film is 10.0 to 60.0 atomic % based on the total atoms in said phase shift film.

6. 3. The reflective mask blank according to claim 1, wherein the phase shift film has a refractive index n of 0.910 or more.

7. 3. The reflective mask blank according to claim 1, wherein the phase shift film has an extinction coefficient of less than 0.

050.

8. 3. The reflective mask blank according to claim 1, wherein the phase shift film is amorphous.

9. 3. The reflective mask blank according to claim 1, wherein the phase shift film has a thickness of 10 to 60 nm.

10. 3. The reflective mask blank according to claim 1, wherein the protective film contains one or more elements selected from the group consisting of Si, Y, Ru, Rh, Pd, and Al.

11. an etching mask film different from the phase shift film is further provided on the opposite side of the phase shift film from the substrate side; 3. The reflective mask blank according to claim 1, wherein the etching mask film contains one or more elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf.

12. 12. The reflective mask blank according to claim 11, wherein the etching mask film further contains one or more elements selected from the group consisting of B, C, N, O and F.

13. A reflective mask having a phase shift film pattern formed by patterning the phase shift film of the mask blank according to claim 1 or 2.

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

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