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

Abstract

The present invention addresses the problem of providing a reflective mask blank containing Pt and having low crystallinity.　This reflective mask blank comprises, in an order of, a substrate, a multilayer reflection film that reflects EUV light, a protection film, and a phase shift film that shifts the phase of the EUV light. The phase shift film contains Pt, and one or more types of first element 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 atom% or more but less than 70.0 atom% with respect to all atoms of the phase shift film, and when the phase shift film is analyzed by X-ray photoelectron spectroscopy, the chemical shift of the peak corresponding to the Pt 4f7 / 2 orbital is 0.3 eV or more.

Description

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

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

[0002] In recent years, in order to further miniaturize semiconductor devices, EUV lithography using 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 reduction projection optical system of the exposure tool, and subsequent processing is performed. A phase shift film, which shifts the phase of EUV light to reduce the reflectance of EUV light, is also used as the absorber film. Phase shift films reduce the reflectance of EUV light by interfering with EUV light reflected from the surface of the absorber film opposite the multilayer reflective film side. Patent Document 1, for example, discloses a phase shift film containing platinum (Pt) as such a phase shift film in terms of optical properties. More specifically, an absorber film (phase shift film) made of Pt is disclosed.

[0005] International Publication No. 2022 / 065421

[0006] In a phase shift film for a reflective mask blank, low crystallinity is required 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 the film had high crystallinity, and it was desired to reduce this crystallinity.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object of providing a reflective mask blank containing Pt and having low crystallinity. 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 research into the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by including a specific metal element and a specific light element in a predetermined ratio, and have thus completed the present invention. That is, the inventors have found that the above-mentioned problems can be solved by the following configuration: [1] 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, wherein 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 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, and when the phase shift film is analyzed by X-ray photoelectron spectroscopy, the 4f of Pt is ７／２A reflective mask blank having a chemical shift of 0.3 eV or more at a peak corresponding to the orbital. [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 reflective mask blank according to [1] or [2], wherein the first element X1 contains at least Ta, and 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 reflective mask blank according to [1] or [2], wherein the first element X1 contains at least W, and the content of W in the phase shift film is 10.0 to 40.0 atomic % based on all atoms in the phase shift film. [5] The reflective mask blank according to [1] or [2], wherein the first element X1 contains at least Hf, and the content of Hf in the phase shift film is 10.0 to 60.0 atomic % based on all atoms in the phase shift film. [6] The reflective mask blank according to any one of [1] to [5], wherein the refractive index n of the phase shift film is 0.910 or more. [7] The reflective mask blank according to any one of [1] to [6], wherein the extinction coefficient of the phase shift film is 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 thickness of the phase shift film is 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] The reflective mask blank according to any one of [1] to

[10] , further comprising an etching mask film different from the phase shift film on the side opposite to the substrate side of the phase shift film, the etching mask film containing 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 manufacturing a reflective mask, comprising a step of patterning the phase shift film of the reflective mask blank according to any one of [1] to

[12] .

[0009] According to the present invention, it is possible to provide a reflective mask blank containing Pt and having low crystallinity. Also, according to the present invention, it is possible to provide a reflective mask and a method for manufacturing a reflective mask.

[0010] 1 is a schematic diagram showing an example of an embodiment of a reflective mask blank of the present invention. FIG. 2 is a schematic diagram showing an example of a manufacturing process of a reflective mask using the reflective mask blank of the present invention.

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

[0012] The meaning of each description in this specification is shown below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written 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 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. Furthermore, when the phase shift film of the reflective mask blank of the present invention is analyzed by X-ray photoelectron spectroscopy, the 4f of Pt is 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, in this order, a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18. The phase shift film 18 contains Pt and the first element X1, the content of which is within a predetermined range, and the chemical shift of the Pt is 0.3 eV or more. The reflective mask blank 10 may also have an etching mask film, described below, on the side of the absorber film 18 opposite the substrate 12 side.

[0015] Although the mechanism by which the crystallinity of the phase shift film of the reflective mask blank of the present invention is low is not entirely clear, the present inventors speculate as follows: It is believed that the phase shift film of the reflective mask blank of the present invention is likely to have low crystallinity by containing Pt and a predetermined amount of the first element X1. Also, in the phase shift film of the reflective mask blank of the present invention, the 4f of Pt ７／２The 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. A substrate with a small thermal expansion coefficient can suppress distortion of the phase shift film pattern due to heat during exposure to EUV light. The thermal expansion coefficient of the substrate is 0±1.0×10 at 20° C. －７ / °C, and 0±0.3×10 －７ / °C is more preferable. Examples of materials with a small thermal expansion coefficient include SiO ２ -TiO ２ However, the present invention is not limited to this, and substrates made of crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, metal, and the like can also be used. ２ -TiO ２ The SiO-based glass ２ 90 to 95 mass% of TiO ２ It is preferable to use quartz glass containing 5 to 10 mass % of TiO ２ When the content of SiO is 5 to 10 mass %, the linear expansion coefficient is approximately zero at around room temperature, and there is almost no change in dimension at around room temperature. ２ -TiO ２ The SiO-based glass ２ and TiO ２ It may contain other minor components.

[0017] The surface of the substrate on which the multilayer reflective film is 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. Note that the surface roughness can be measured using an atomic force microscope, and the surface roughness is described as the root-mean-square roughness Rq based on JIS-B0601. The first principal surface is preferably surface-processed to achieve a predetermined flatness, in order to improve the pattern transfer accuracy and positional accuracy of a reflective mask obtained using the reflective mask blank. In a predetermined region of the first principal surface (e.g., a 132 mm × 132 mm region), the flatness of the substrate is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate are determined appropriately based on the design values ​​of the mask, etc. For example, the outer shape may be 6 inches (152 mm) square and the thickness may be 0.25 inches (6.3 mm). The substrate is often rectangular (oblong) or square. Furthermore, it is preferable that the substrate has high rigidity in order to prevent deformation due to film stress of films (such as multilayer reflective films, protective films, and phase shift films) formed on the substrate. For example, the Young's modulus of the substrate is preferably 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 a high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity for EUV light with a wavelength of around 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 with a wavelength of around 13.5 nm is preferably 60% or more, more preferably 65% ​​or more.

[0019] Since multilayer reflective films can achieve high reflectivity for EUV light, they are typically formed by alternately stacking multiple high-refractive index layers, which exhibit a high refractive index for EUV light, and multiple low-refractive index layers, which exhibit a low refractive index for EUV light. The multilayer reflective film may be formed by stacking multiple cycles of a stack structure in which high-refractive index layers and low-refractive index layers are stacked in this order from the substrate side, or multiple cycles of a stack structure in which low-refractive index layers and high-refractive index layers are stacked in this order. The high-refractive index layer may be a layer containing Si. Examples of materials containing Si include elemental Si and Si compounds containing one or more elements selected from the group consisting of B, C, N, and O. The use of a high-refractive index layer containing Si results in a reflective mask with excellent reflectivity for EUV light. 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 multilayer reflective films are most common, but the 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.

[0020] The thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layer can be appropriately selected depending on the film material used and the reflectivity of the reflective layer required for EUV light. Taking a Mo / Si multilayer reflective film as an example, to obtain a multilayer reflective film with a maximum reflectivity of 60% or more for EUV light, it is sufficient to laminate 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 so that the number of repeating 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 having a predetermined thickness is first deposited on a substrate using an ion beam sputtering method. Then, a Mo layer having a predetermined thickness is deposited using an 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. The protective film 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 the material containing Si include Si oxide, Si nitride, Si oxynitride, and alloys containing Si. Examples of the material containing Y include Y oxide, Y fluoride, Y oxyfluoride, and alloys containing Y.

[0024] Examples of materials containing Ru include Ru metal alone 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 Rh alloys and nitrogen, and Rh-containing oxynitrides containing the Rh alloys, nitrogen, and oxygen. Examples of materials containing Pd include Pd metal alone 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] Furthermore, as materials that can achieve the above object, Al and nitrides containing these metals and nitrogen, and Al ２ O ３ 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 reflectivity 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 within the above-mentioned preferred thickness range.

[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 element X1 in the phase shift film is 10 atomic % or more and less than 70 atomic % with respect to the total atoms in the phase shift film. When the phase shift film of the reflective mask blank of the present invention was analyzed by X-ray photoelectron spectroscopy, the 4f of Pt was 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 %, even 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 obtained by analysis using X-ray photoelectron spectroscopy (XPS). A 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 content of Ta in the phase shift film is preferably 10.0 atomic % or more but less than 70.0 atomic %, more preferably 20.0 to 60.0 atomic %, even more 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, in order to improve the optical properties against EUV light and reduce the crystallinity. When the first element X1 includes 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 %, even more 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 of 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 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 % based on the total atoms in the phase shift film, more preferably 80.0 atomic % or less, even more preferably 70.0 atomic % or less, and particularly preferably 60.0 atomic % or less. The Pt content in the phase shift film is obtained by analysis using XPS. The detailed analysis method will be described later.

[0033] Furthermore, 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. There is no particular upper limit to the chemical shift, but it is often 1.5 eV or less, and more often 1.2 eV or less. Analysis by XPS in this specification will be described below.

[0034] For XPS analysis, an analytical instrument "PHI 5000 VersaProbe" manufactured by ULVAC-PHI, Inc. was used. The instrument was calibrated in accordance with JIS K 0145. First, a measurement sample approximately 1 cm square was cut out from a reflective mask blank. The obtained measurement sample was placed in a measurement holder so that the phase shift film side was the measurement surface. After the measurement holder was loaded into the instrument, a portion of the phase shift film was removed by 5 nm from the outermost surface using an argon ion beam. If the phase shift film was not exposed, the above removal was continued until the phase shift film was exposed, and then a portion of the phase shift film was removed by 5 nm from the outermost surface. The sputtering rate during this removal can be measured using a separately prepared sample. After removing the outermost surface of the phase shift film, X-rays (monochromated AlKα rays) were irradiated onto the removed portion, and analysis was performed with a photoelectron take-off angle (the angle between the surface of the measurement sample and the direction of the detector) of 45°. In addition, a neutralization gun is used to suppress charge buildup during analysis. The analysis involves a wide scan in the binding energy range of 1,000 to 0 eV to confirm the presence of elements, followed by a narrow scan depending on the elements present (e.g., Pt and the first element X1). The narrow scan is performed, for example, with a pass energy of 58.7 eV, an energy step of 0.1 eV, a time step of 50 ms, and 10 integrations. 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 integrations. 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 representing the peak of the C1s orbital on the measurement sample is obtained from the narrow scan analysis results, and the shift value is calculated by subtracting this binding energy value from 284.8 eV. 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 result 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 ７／２The 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 C as a component, the binding energy is calibrated using Au 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 the value is obtained 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 relative sensitivity coefficients specific to each element and each orbital from a 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 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 4f of Pt. ７／２ The chemical shift of the peak corresponding to the orbital can be determined in the same manner. 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 described later in the Examples section.

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

[0039] When the phase shift film contains the other element, the content of the other element 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 the total atoms of the phase shift film. It is also preferable that the phase shift film does not contain the other element. In other words, it is also preferable that the phase shift film consists 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. The refractive index n of the phase shift film 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 enable the thickness of the phase shift film to be further reduced. 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 dependence of reflectance using EUV light with a wavelength of 13.5 nm, and fitting 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 Scherrer's equation is used to calculate the crystallite diameter. 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 the 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. While there is no particular lower limit for the crystallite diameter, it is often 0.1 nm or more. The phase shift film of the present invention may be amorphous.

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

[0044] The phase shift film preferably has resistance to dissolution in cleaning solutions. Having resistance to dissolution in cleaning solutions makes it difficult for the phase shift film to be removed during the etching process of the etching mask film described later, making it easier to obtain the desired pattern. More specifically, it is preferable that the change in film thickness of the phase shift film is small when contacted with a sulfuric acid-hydrogen peroxide aqueous solution (SPM). For example, when the phase shift film is etched for 20 minutes with SPM at 100°C, 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. Specific conditions for the etching process are as described in the examples below. In order to improve the resistance of the phase shift film to dissolution in cleaning solutions, the phase shift film preferably contains Ta as the first element X1. The Ta content in the phase shift film may fall within the preferred range described above.

[0045] The phase shift film can be formed using known film formation methods such as magnetron sputtering and ion beam sputtering. For example, when forming a PtTa film as a phase shift film using 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 may be used.

[0046] [Etching Mask Film] The reflective mask blank of the present invention may have an etching mask film on the side opposite to the substrate side of the phase shift film. 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 the 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. The etching mask film also preferably 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. The material constituting the etching mask film may also be a composite compound (e.g., a composite oxide) containing two or more elements of the third element X3.

[0048] For example, examples of 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 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. Furthermore, examples of Si-based materials 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, SiO ２ , 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 a conductive film, the reflective mask blank can be handled using an electrostatic chuck. The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably, for example, 200 Ω / sq. or less, more preferably 100 Ω / sq. or less. The conductive film may be made of a wide variety of materials described in known literature. For example, a 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 be adjusted to balance the stress from various films formed on the first main surface side and flatten the reflective mask blank. The conductive film can be formed using 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 Films] The reflective mask blank of the present invention may have other films. Examples of the other films include an antireflection film used when inspecting an absorber film pattern using inspection light (e.g., wavelength 193 to 248 nm). The antireflection film is preferably disposed on the side opposite to the substrate side of the phase shift film.

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

[0052] FIG. 2A shows a state in which a resist pattern 40 is formed on a reflective mask blank having, in this order, a substrate 12, a multilayer reflective film 14, a protective film 16, and a phase shift film 18. 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, exposing it to light, and developing it to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Then, using the resist pattern 40 of FIG. 2A as a mask, the phase shift film 18 is etched and patterned, and the resist pattern 40 is removed to obtain a laminate having a 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 region 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 the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain a reflective mask shown in FIG. 2D.

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

[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.

[0055] The present invention will be described in more detail below based on 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 interpreted as being limited by the examples shown below. Examples 1 to 4 described below are 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, as a substrate, SiO ２ -TiO ２ A glass substrate (6-inch (152 mm) square outer diameter, 6.3 mm thick) of this type was prepared. This glass substrate had 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 rigidity is 3.07 × 10 ７ m ２ / s ２ The 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 forming a Si film (4.5 nm thick) and a Mo film (2.3 nm thick) using an ion beam sputtering method 40 times, and then forming an additional Si film (4.5 nm thick) after the 40th Mo film. 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 formed protective film using a multi-target magnetron sputtering system. The film formation conditions for the PtWB film were as follows: Target: Pt target, Ta target, and W target Sputtering gas: Ar gas Film formation pressure: 0.3 Pa Input power: 12 to 120 W Film formation rate: 0.3 nm / sec Film thickness: 30 nm Each target was discharged using a DC power supply. The input power to each target was adjusted to form the film with the composition shown in the table below.

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

[0062] Example 5 A reflective mask blank of 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 (Example 5) made of only Pt was formed.

[0063] <Measurement> [XPS] The phase shift film formed by the above-mentioned method 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. The bond energy in parentheses is the peak value of the reference bond energy. Hf: 4f of Hf ７／２ Peak corresponding to orbital (14.3 eV) Ta: 4f of Ta ７／２ Peak corresponding to orbital (21.8 eV) W: 4f of W ７／２ Peak corresponding to the orbital (31.5 eV)

[0064] [Optical Properties] The optical properties of the phase shift film formed by 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 formed was obtained by the above-mentioned method. 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 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 correspond sufficiently. In practical use, the crystallite diameter 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 measurement, a Smart Lab HTP from Rigaku Corporation was used. CuKα rays were used as the X-ray source, and the tube voltage was 40 kV and the tube current was 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 treatment. Note that negative values ​​indicate a decrease in the thickness of the phase shift film. The absolute value of the change in 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] <Results> 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]

[0069] From the results of Examples 1 to 4 shown in Table 1, it was found that the phase shift film contained Pt and the first element X1, the content of the first element X1 in the phase shift film was 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, from the results of Example 5, the crystallinity was not low in the phase shift film containing only Pt. From the comparison of Examples 1 and 2 with Examples 3 and 4, it was confirmed that when the first element X1 contains at least Ta and the content of Ta in the phase shift film is 10.0 atomic % or more and less than 70.0 atomic % with respect to the total atoms of 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.

[0071] REFERENCE SIGNS LIST 10 reflective mask blank 12 substrate 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 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, wherein 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 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, and when the phase shift film is analyzed by X-ray photoelectron spectroscopy, the 4f ７／２ A reflective mask blank, in which the chemical shift of a peak corresponding to the orbital is 0.3 eV or more.

2. The reflective mask blank according to claim 1, wherein the Pt content 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. A reflective mask blank according to claim 1 or 2, wherein the first element X1 contains at least Ta, and the content of Ta 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.

4. A reflective mask blank according to claim 1 or 2, wherein the first element X1 contains at least W, and the content of W in the phase shift film is 10.0 to 40.0 atomic % based on all atoms in the phase shift film.

5. A reflective mask blank according to claim 1 or 2, wherein the first element X1 contains at least Hf, and the content of Hf in the phase shift film is 10.0 to 60.0 atomic % based on all atoms in the phase shift film.

6. The reflective mask blank according to claim 1 or 2, wherein the phase shift film has a refractive index n of 0.910 or more.

7. The reflective mask blank according to claim 1 or 2, wherein the phase shift film has an extinction coefficient of less than 0.

050.

8. The reflective mask blank according to claim 1 or 2, wherein the phase shift film is amorphous.

9. The reflective mask blank according to claim 1 or 2, wherein the phase shift film has a thickness of 10 to 60 nm.

10. The reflective mask blank according to claim 1 or 2, wherein the protective film contains one or more elements selected from the group consisting of Si, Y, Ru, Rh, Pd and Al.

11. The reflective mask blank according to claim 1 or 2, further comprising an etching mask film different from the phase shift film on the opposite side of the phase shift film from the substrate side, the etching mask film containing 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 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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