EUV lithography reflective photomask substrate, EUV lithography reflective photomask, and methods for manufacturing the above.

Abstract

This invention provides a reflective photomask substrate for EUV lithography, characterized in that: it has a multilayer reflective film for reflecting EUV light and a phase shifting film for shifting the phase of EUV light sequentially formed on the substrate, and the phase shifting film has a layer 1, which contains ruthenium (Ru) and at least one of the group consisting of oxygen (O) and nitrogen (N); using out-of-plane XRD, the full width at half maximum (FWHM) of the highest intensity peak among the diffraction peaks originating from the phase shifting film observed at 2θ: 20° to 50° is 1.0° or more.

Description

Technical Field

[0001] This invention relates to a reflective photomask substrate (hereinafter referred to as "EUV photomask substrate") for EUV (Extreme Ultra Violet) lithography, a reflective photomask for EUV lithography (hereinafter referred to as "EUV photomask"), and a method for manufacturing the above for use in semiconductor manufacturing and the like. Prior Technology

[0002] Previously, in the semiconductor industry, photolithography, using visible or ultraviolet light, was used as a transfer technique for forming micro-patterns in integrated circuits on Si substrates and the like to create micro-patterns. However, the miniaturization of semiconductor devices is accelerating, gradually approaching the limits of previous photolithography methods. In the case of photolithography, the resolution limit of the pattern is about half the exposure wavelength. It is said that even using the immersion method, the resolution is only about one-quarter of the exposure wavelength, and it is predicted that even using the immersion method with ArF laser (193 nm), the limit is only about 20 nm to 30 nm. Therefore, it is believed that exposure technology using EUV light, which has a shorter wavelength than ArF laser, namely EUV lithography, is expected to become the exposure technology for wavelengths of 20 nm to 30 nm and beyond. In this specification, EUV light refers to light with wavelengths in the soft X-ray region or the vacuum ultraviolet region. Specifically, it refers to light with wavelengths of about 10 nm to 20 nm, especially about 13.5 nm ± 0.3 nm.

[0003] EUV light is easily absorbed by various materials, and at this wavelength, the refractive index of materials is close to 1. Therefore, refractive optical systems such as those used in visible or ultraviolet lithography cannot be used. Consequently, reflective optical systems, namely reflective masks and mirrors, are used in EUV lithography.

[0004] On the other hand, unlike the shortening of light wavelengths, a technique using phase-shifting photomasks to improve resolution has also been proposed. Phase-shifting photomasks impart a 180-degree phase difference to the light passing through them by making the material or shape of the transmissive portion of the photomask pattern different from that of adjacent transmissive portions. Therefore, in the region between two transmissive portions, the diffracted light with a 180-degree phase difference cancels each other out, resulting in minimal light intensity, increased photomask contrast, expanded focal depth during transfer, and improved transfer accuracy. Furthermore, while the optimal phase difference in principle is 180 degrees, in practice, a difference of approximately 175 to 185 degrees is sufficient to achieve a significant improvement in resolution.

[0005] A halftone mask, as a type of phase-shifting mask, is a phase-shifting mask as follows: As the material constituting the mask pattern, a thin film that is semi-transparent to the exposed light is used as an absorption layer, so that the transmittance is reduced to a few percent (usually about 2.5% to 15.0% relative to the light transmitted from the substrate), and a phase difference of about 175 degrees to 185 degrees is given to it, thereby improving the resolution of the edge of the pattern and improving the transfer accuracy.

[0006] Because EUV exposure uses a reflective optical system, it has a smaller numerical aperture (NA) and a shorter wavelength, resulting in the following unique problems: it is easily affected by the surface irregularities of the mirror or photomask, making it difficult to accurately resolve the fine linewidth of the target. Therefore, a halftone EUV photomask is proposed, which can also apply the principle of halftone photomasks used in previous excimer laser exposures to EUV exposures using reflective optical systems (see, for example, Patent Documents 1 and 2).

[0007] In patent documents 1 and 2, by using a Ru-containing layer with a lower refractive index n as a phase shift film, the film thickness required to obtain a specified phase difference is reduced, and a finer and more precise phase shift pattern can be formed.

[0008] However, since RuO described in Patent Document 1 or Ru described in Patent Document 2 are easily crystallized materials, there are concerns that grains may adversely affect the pattern shape when forming the phase-shifting film pattern. If the material constituting the phase-shifting film has high crystallinity, there are problems such as a large surface roughness of the phase-shifting film and a large line edge roughness (LER) after patterning. Therefore, the crystalline structure of the phase-shifting film is preferably amorphous.

[0009] Therefore, in Patent Document 3, by using a material containing Ru and specified elements in the phase shift film, the crystalline structure of the phase shift film can be made amorphous, thereby reducing the adverse effects of grains such as metals on the formation of the phase shift pattern. [Previous Technical Documents] [Patent Literature]

[0010] [Patent Document 1] Japanese Patent No. 5282507 [Patent Document 2] Japanese Patent No. 6381921 [Patent Document 3] International Publication No. WO2019 / 225736 Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] However, it was found that even when using a material containing Ru and specified elements to phase shift film according to the invention described in Patent Document 3, there are cases where the crystalline structure of the phase shift film does not become amorphous.

[0013] The objective of this invention is to provide an EUV photomask substrate having an amorphous phase shift film with a crystalline structure, thereby solving the problems of the prior art. [Technical means to solve the problem]

[0014] The present invention is as follows [1] to

[18] . [1] A reflective photomask substrate for EUV lithography, characterized in that: it comprises, sequentially formed on a substrate, a multilayer reflective film for reflecting EUV light and a phase-shifting film for shifting the phase of EUV light, and The aforementioned phase shifting film has a layer 1, which comprises ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N); When using out-of-plane X-ray diffraction (XRD), the peak with the highest intensity observed at 2θ: 20°~50° originating from the aforementioned phase-shifted film has a full width at half maximum (FWHM) of over 1.0°. [2] As described in [1], the EUV lithography reflective photomask substrate contains Ru in the range of 40 to 99 at% and O in the range of 1 to 60 at% or, Ru in the range of 30 to 98 at% and O in the range of 1 to 69 at% and N in the range of 1 to 69 at%. [3] As described in [1], the EUV lithography reflective photomask substrate contains Ru in the range of 30 to 98 at% and N in the range of 2 to 70 at%. [4] As described in [2], the EUV lithography reflective photomask substrate, wherein the above-mentioned layer 1 further comprises at least one element (X) selected from the group consisting of chromium (Cr), tantalum (Ta), titanium (Ti), rhenium (Re), tungsten (W), bismuth (Bi), manganese (Mn), platinum (Pt), copper (Cu), iridium (Ir) and vanadium (V) in a composition ratio (at%) (Ru:X) of Ru to X in the above-mentioned phase shift film of 20:1 to 1:5, and contains a total of Ru and X (Ru+X) in a range of 40 to 99 at%, and contains O in a range of 1 to 60 at%, or contains a total of Ru and X (Ru+X) in a range of 30 to 98 at%, contains O in a range of 1 to 69 at%, and contains N in a range of 1 to 69 at%. [5] As described in [3], the EUV lithography reflective photomask substrate, wherein the above layer 1 further includes at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V in a composition ratio (at%) of Ru to X of 20:1 to 1:5, and includes the sum of Ru and X (Ru+X) in a range of 30 to 90 at%, and includes N in a range of 10 to 70 at%. [6] The EUV lithography reflective photomask substrate described in [1] to [5] further comprises a layer 2 containing at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V. [7] As described in [6], the EUV lithography reflective photomask substrate, wherein the above-mentioned layer 2 further comprises at least one element selected from the group consisting of O, N, boron (B) and carbon (C). [8] The EUV lithography reflective photomask substrate described in [1] to [7] has a phase shift film thickness of 20 nm to 60 nm. [9] The reflective photomask substrate for EUV lithography described in [1] to [8], wherein the thickness of the above layer 1 is 10 nm or more.

[10] The EUV lithography reflective photomask substrate described in [1] to [9] has a phase difference of 150 degrees to 250 degrees between the EUV light reflected from the multilayer reflective film and the EUV light reflected from the phase-shifting film, and the relative reflectivity of the EUV light reflectivity of the phase-shifting film surface and the EUV light reflectivity of the multilayer reflective film surface ((EUV light reflectivity of the phase-shifting film surface / EUV light reflectivity of the multilayer reflective film surface) × 100) is 2% to 37%.

[11] The EUV lithography reflective photomask substrate described in [1] to

[10] has a protective film formed between the multilayer reflective film and the phase shift film.

[12] The EUV lithography reflective photomask substrate described in

[11] contains at least one element selected from the group consisting of Ru, palladium (Pd), Ir, rhodium (Rh), Pt, zirconium (Zr), niobium (Nb), Ta, Ti and silicon (Si).

[13] As described in

[12] , the reflective photomask substrate for EUV lithography further comprises at least one element selected from the group consisting of O, N, and B.

[14] The EUV lithography reflective photomask substrate described in [1] to

[13] has an etch mask film on the phase offset film, the etch mask film containing at least one element selected from the group consisting of Nb, Ti, molybdenum (Mo), Ta and Si.

[15] As described in

[14] , the EUV lithography reflective photomask substrate further comprises at least one element selected from the group consisting of O, N, and B.

[16] An EUV lithography reflective photomask having a pattern formed on the phase offset film of the EUV lithography reflective photomask substrate as described in [1] to

[15] .

[17] A method for manufacturing a reflective photomask substrate for EUV lithography, characterized by comprising the following steps: A multilayer reflective film for reflecting EUV light is formed on the substrate; A phase-shifting film is formed on the aforementioned multilayer reflective film to shift the phase of EUV light; and An etching mask film is formed on the aforementioned phase shift film; and The aforementioned phase shifting film has a layer 1, which comprises ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N); Using out-of-plane XRD, among the diffraction peaks originating from the phase-shifted film observed at 2θ: 20°–50°, the peak with the highest intensity has a full width at half maximum (FWHM) greater than 1.0°. The aforementioned etched masking film can be removed by washing with acid or alkali.

[18] A method for manufacturing an EUV lithography reflective photomask, characterized in that: a phase shift film in an EUV lithography reflective photomask substrate manufactured by the method for manufacturing an EUV lithography reflective photomask substrate as described in

[17] is patterned to form a pattern. [Effects of the Invention]

[0015] The EUV photomask substrate of the present invention has a phase shift film with a crystalline structure that is amorphous. Simple Explanation of the Diagram

[0016] Figure 1 is a schematic cross-sectional view showing one embodiment of the EUV photomask substrate of the present invention. Figure 2 is a schematic cross-sectional view showing another embodiment of the EUV photomask substrate of the present invention. Figure 3 is a schematic cross-sectional view showing one embodiment of the EUV photomask of the present invention. Figure 4 illustrates the steps of forming a pattern on the EUV photomask substrate 1b shown in Figure 2, wherein a resist film 30 is formed on the etching mask film 15 of the EUV photomask substrate 1b. Figure 5 shows the steps following Figure 4, where a resist pattern 300 is formed on the resist film 30. Figure 6 illustrates the steps following Figure 5, where an etched mask pattern 150 is formed on the etched mask film 15. Figure 7 shows the steps following Figure 6, where a phase shift film pattern 140 is formed on the phase shift film 14. Figure 8 is a graph showing the relationship between the full width at half maximum (FWHM) of the phase shift film in the reference example and the surface roughness (RMS). Implementation

[0017] The EUV photomask substrate and the EUV photomask of the present invention will be described below with reference to the drawings.

[0018] Figure 1 is a schematic cross-sectional view showing one embodiment of the EUV photomask substrate of the present invention. In the EUV photomask substrate 1a shown in Figure 1, a multilayer reflective film 12 for reflecting EUV light, a protective film 13 for the multilayer reflective film 12, and a phase shifting film 14 for shifting the phase of EUV light are sequentially formed on the substrate 11 from the substrate side. However, in the EUV photomask substrate of the present invention, only the substrate 11, the multilayer reflective film 12, and the phase shifting film 14 are necessary components in the configuration shown in Figure 1, while the protective film 13 is an optional component. Furthermore, the protective film 13 of the multilayer reflective film 12 is a layer provided to protect the multilayer reflective film 12 when forming the pattern of the phase shift film 14.

[0019] The following describes the various components of the EUV photomask substrate 1a.

[0020] The substrate 11 meets the characteristics of a substrate used as an EUV photomask substrate. Therefore, the substrate 11 has a low coefficient of thermal expansion (specifically, the coefficient of thermal expansion at 20°C is preferably 0±0.05×10-7 / °C, more preferably 0±0.03×10-7 / °C), and excellent smoothness, flatness, and resistance to cleaning solutions used when cleaning the photomask substrate or the photomask after patterning. Specifically, a glass with a low coefficient of thermal expansion, such as SiO2-TiO2 based glass, is used as the substrate 11, but it is not limited to this; crystallized glass obtained by precipitating β-quartz solid solution, quartz glass, silicon, or metal substrates can also be used. If the substrate 11 has a smooth surface with a surface roughness (RMS) of less than 0.15 nm and a flatness of less than 100 nm, then high reflectivity and transfer accuracy can be obtained in the photomask after the pattern is formed, which is better. The size or thickness of the substrate 11 can be appropriately determined according to the design values ​​of the photomask. In the embodiment shown below, a SiO2-TiO2 glass with a diameter of 6 inches (152 mm) and a thickness of 0.25 inches (6.3 mm) is used. Preferably, the surface of the substrate 11 on the side where the multilayer reflective film 12 is formed is free of defects. However, even if defects exist, it is acceptable as long as they do not cause phase defects. Specifically, it is preferable that the depth of the concave defects and the height of the convex defects are 2 nm or less, and that the half-width at half-maximum (WHM) of the concave and convex defects is 60 nm or less. The WHM of a concave defect refers to the width at a position where the depth of the concave defect is half its depth. The WHM of a convex defect refers to the width at a position where the height of the convex defect is half its height.

[0021] The multilayer reflective film 12 achieves high EUV light reflectivity by repeatedly depositing alternating layers of high and low refractive index layers. In the multilayer reflective film 12, Mo is widely used for the high refractive index layers, and Si is widely used for the low refractive index layers. That is, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to this; Ru / Si multilayer reflective films, Mo / Be multilayer reflective films, Mo compound / Si compound multilayer reflective films, Si / Mo / Ru multilayer reflective films, Si / Mo / Ru / Mo multilayer reflective films, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0022] The multilayer reflective film 12 is not particularly limited as long as it possesses the characteristics required for a reflective layer as an EUV photomask substrate. Here, a particularly required characteristic for the multilayer reflective film 12 is high EUV light reflectivity. Specifically, when EUV light in the wavelength range is irradiated onto the surface of the multilayer reflective film 12 at an incident angle of 6 degrees, the maximum reflectivity near a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more. Furthermore, even when a protective film 13 is provided on the multilayer reflective film 12, the maximum reflectivity near a wavelength of 13.5 nm is still preferably 60% or more, and more preferably 65% ​​or more.

[0023] The thickness of each layer and the number of repeating units in the multilayer reflective film 12 can be appropriately selected according to the film material used and the required EUV light reflectivity of the reflective layer. Taking a Mo / Si multilayer reflective film as an example, in order to produce a multilayer reflective film 12 with a maximum EUV light reflectivity of 60% or more, the multilayer reflective film only needs to be laminated with a Mo layer with a thickness of 2.3±0.1 nm and a Si layer with a thickness of 4.5±0.1 nm in a repeating unit number of 30 to 60.

[0024] Furthermore, each layer of the multilayer reflective film 12 can be formed to the required thickness using well-known film-forming methods such as magnetron sputtering or ion beam sputtering. For example, when forming a Si / Mo multilayer reflective film using ion beam sputtering, it is preferable to use a Si target as the target and argon gas (pressure 1.3×10⁻² Pa to 2.7×10⁻² Pa) as the sputtering gas. Under conditions of ion acceleration voltage of 300 V to 1500 V and film formation rate of 0.030 nm / sec to 0.300 nm / sec, a Si film is formed with a thickness of 4.5 nm. Then, using a Mo target as the target and argon gas (pressure 1.3×10⁻² Pa to 2.7×10⁻² Pa) as the sputtering gas, a Mo film is formed with a thickness of 2.3 nm under conditions of ion acceleration voltage of 300 V to 1500 V and film formation rate of 0.030 nm / sec to 0.300 nm / sec. This is taken as 1 cycle, and Si and Mo films are deposited for 40 to 50 cycles, thereby forming a Si / Mo multilayer reflective film.

[0025] To prevent oxidation of the surface of the multilayer reflective film 12, the uppermost layer of the multilayer reflective film 12 is preferably made of a material that is not easily oxidized. This layer of material functions as a cover layer of the multilayer reflective film 12. Specific examples of this type of material that functions as a cover layer include a Si layer. When the multilayer reflective film 12 is a Si / Mo multilayer reflective film, the uppermost layer is a Si layer, which functions as a cover layer. In this case, the thickness of the cover layer is preferably 11 ± 2 nm.

[0026] The protective film 13 is provided for the purpose of protecting the multilayer reflective film 12 from damage during the etching process, typically a dry etching process, when a pattern is formed on the phase shift film 14. Therefore, the material of the protective film is selected to have the following characteristics: it is not easily affected by the etching process of the phase shift film 14, i.e., its etching rate is slower than that of the phase shift film 14, and it is not easily damaged by the etching process. To satisfy the above characteristics, the protective film 13 contains at least one element selected from the group consisting of Ru, Pt, Pd, Ir, Rh, Zr, Nb, Ta, Ti, and Si. However, since Ru is also a constituent material of the phase shift film 14, when Ru is used as the material of the protective film 13, an alloy of Ru and other elements is used. For example, RuZr can be used. The protective film 13 may further include at least one element selected from the group consisting of O, N, and B. That is, it may also be an oxide, nitride, oxynitride, or boride of the aforementioned element. Specific examples include ZrO2 and SiO2.

[0027] The thickness of the protective film 13 is not particularly limited, but in the case of RuZr film, it is preferably 2 nm to 3 nm.

[0028] The protective film 13 is formed using well-known film formation methods such as magnetron sputtering and ion beam sputtering. For example, when forming a RuZr film using DC (Direct Current) sputtering, it is preferable to use a Ru target and a Zr target as targets, use argon gas (pressure 1.0×10-2 Pa or higher to 1.0×100 Pa or lower) as the sputtering gas, and form a film with a thickness of 2 nm to 3 nm under the conditions that the input power to the Ru target and the Zr target are 100 W or higher to 600 W or lower, and the film formation rate is 0.020 nm / sec to 1.000 nm / sec, respectively.

[0029] As mentioned above, the phase shift film in the halftone EUV mask is required to have an amorphous crystalline structure.

[0030] In the EUV photomask substrate 1a of the present invention, the phase shifting film 14 has a layer 1, which includes Ru and at least one of the group consisting of O and N. The EUV photomask substrate 1a of the present invention has a phase-shifting film 14 having a layer 1. Using out-of-plane XRD, the full width at half maximum (FWHM) of the highest intensity peak observed at 2θ: 20°~50° originating from the phase-shifting film 14 is 1.0° or higher. If the FWHM is 1.0° or higher, steep peaks originating from the crystalline phase are not observed, and the crystalline structure of the phase-shifting film 14 is amorphous. When the phase shift film 14 is composed solely of layer 1, the crystalline structure of the phase shift film 14 constituting layer 1 is amorphous. When the phase shift film 14 has layer 2, the crystalline structure of the entire phase shift film 14, including layer 1 and layer 2, is amorphous. Furthermore, when the out-of-plane XRD method is used, if the diffraction peak originating from the phase-shifted film is not observed at 2θ: 20°~50°, it is considered that the full width at half maximum (FWHM) is 180°.

[0031] If the crystalline structure of the phase shift film 14 is amorphous, the smoothness of the surface of the phase shift film 14 will be higher. In this specification, the surface roughness (RMS) of the phase shift film 14, measured using an atomic force microscope, is used as an indicator of the smoothness of the phase shift film 14 surface. The surface roughness (RMS) of the phase shift film 14 on the EUV photomask substrate 1a of the present invention is preferably below 0.3 nm, and more preferably below 0.25 nm.

[0032] The phase shift film 14 of the present invention preferably has a full width at half maximum (FWHM) of 2.0° or more, and more preferably 3.0° or more. Furthermore, the phase shift film 14 of the present invention is preferably in a state where no peak is visible, and more preferably, the FWHM is 5.0° or less, and more preferably 3.5° or less.

[0033] In the EUV photomask substrate 1a of the present invention, if the phase shift film 14 is in the first to third forms shown below, the full width at half maximum (FWHM) is 1.0° or more.

[0034] <First Form> The first morphology of the phase shift film 14 has a layer 1 containing Ru in the range of 40 to 99 at% and O in the range of 1 to 60 at%. If the O content of layer 1 is less than 1 at%, then when measured by out-of-plane XRD, a steep peak of the crystalline phase originating from Ru is observed in the diffraction peaks originating from phase-shifted film 14 at 2θ: 20°~50°, and the full width at half maximum (FWHM) is less than 1.0°. If the O content of layer 1 exceeds 60 at%, a steep peak originating from the crystalline phase of RuO2 is observed in the diffraction peak originating from phase-shifted film 14 at 2θ: 20°~50°, and the full width at half maximum (FWHM) does not reach 1.0°. If the O content of layer 1 is in the range of 1~60 at% then when measured by out-of-plane XRD, the steep peaks of the crystalline phase of Ru or RuO2 originating from the diffraction peaks observed at 2θ: 20°~50° are not observed in the diffraction peaks originating from the phase-shifted film 14, and the full width at half maximum (FWHM) becomes 1.0° or higher.

[0035] In this specification, the content of each element in layer 1 of the phase shift film and in layer 2 below are values ​​measured using an X-ray photoelectron spectroscopy device.

[0036] When a phase shift film is formed using sputtering according to the following steps, there is a situation where O is mixed in, but the content of this mixed O is less than 1.0 at%, so the full width at half maximum (FWHM) will not be more than 1.0°.

[0037] In the first form of the phase shift film 14, since the introduction of O will change the optical constant of layer 1, the EUV light reflectivity of the phase shift film surface can be adjusted by controlling the O content of layer 1.

[0038] The first morphology of the phase shift film 14 is preferably a layer 1 containing Ru in the range of 40 to 90 at% and O in the range of 10 to 60 at%; more preferably, it is a layer 1 containing Ru in the range of 40 to 75 at% and O in the range of 25 to 60 at%.

[0039] <Second Form> The second morphology of the phase shift film 14 has a layer 1 containing Ru in the range of 30 to 98 at%, O in the range of 1 to 69 at%, and N in the range of 1 to 69 at%. If the O content of layer 1 is less than 1 at%, then when measured by out-of-plane XRD, a steep peak of the crystalline phase originating from Ru is observed in the diffraction peaks originating from phase-shifted film 14 at 2θ: 20°~50°, and the full width at half maximum (FWHM) is less than 1.0°. If the O content of layer 1 exceeds 69 at%, it will be difficult to form layer 1. If the N content of layer 1 is less than 1 at%, then when measured by out-of-plane XRD, a steep peak of the crystalline phase originating from Ru is observed in the diffraction peaks originating from phase-shifted film 14 at 2θ: 20°~50°, and the full width at half maximum (FWHM) is less than 1.0°. If the N content of layer 1 exceeds 69 at%, it will be difficult to form layer 1. If the O content of layer 1 is in the range of 1~69 at% and the N content is in the range of 1~69 at%, then when measured by out-of-plane XRD, the steep peaks of the crystalline phase originating from the phase-shifted film 14 observed at 2θ: 20°~50° are not observed, and the full width at half maximum (FWHM) becomes 1.0° or higher.

[0040] In the second form of the phase shift film 14, since the introduction of O will change the optical constant of layer 1, the EUV light reflectivity of the phase shift film surface can be adjusted by controlling the O content of layer 1.

[0041] The second morphology of the phase shift film 14 is preferably a layer 1 containing Ru in the range of 30 to 75 at%, O in the range of 24 to 69 at%, and N in the range of 1 to 20 at%, and more preferably a layer 1 containing Ru in the range of 30 to 65 at%, O in the range of 34 to 69 at%, and N in the range of 1 to 10 at%.

[0042] <Third Form> The third morphology of the phase shift film 14 has a layer 1 containing Ru in the range of 30 to 98 at% and N in the range of 2 to 70 at%. If the N content of layer 1 is less than 2 at%, then when measured by out-of-plane XRD, a steep peak of the crystalline phase originating from Ru is observed in the diffraction peaks originating from phase-shifted film 14 at 2θ: 20°~50°, and the full width at half maximum (FWHM) is less than 1.0°. If the N content of layer 1 exceeds 70 at%, it will be difficult to form layer 1. If the N content of layer 1 is in the range of 2~70 at% then when measured by out-of-plane XRD, the steep peaks of the crystalline phase originating from the phase-shifted film 14 observed at 2θ: 20°~50° are not observed, and the full width at half maximum (FWHM) becomes 1.0° or higher.

[0043] In the third form of the phase-shifting film 14, the change in the optical constant of layer 1 caused by the introduction of N is small, so the EUV light reflectivity of the phase-shifting film surface is not easily affected by the N content. Therefore, the crystalline structure of the phase-shifting film 14 can be made amorphous, and the EUV light reflectivity of the phase-shifting film surface will not change significantly due to the introduction of N.

[0044] The third morphology of the phase shift film 14 is preferably a layer 1 containing Ru in the range of 80 to 98 at% and N in the range of 2 to 20 at%.

[0045] In the first, second, and third forms of the phase-shifting film 14, layer 1 may further contain at least one element (X) selected from the group consisting of chromium (Cr), tantalum (Ta), titanium (Ti), rhenium (Re), tungsten (W), bismuth (Bi), manganese (Mn), platinum (Pt), copper (Cu), iridium (Ir), and vanadium (V) to adjust the EUV light reflectivity of the surface of the phase-shifting film 14. Preferably, X is Cr, Re, Mn, or V, and more preferably Cr and Re.

[0046] In the first, second, and third forms of the phase-shifting film 14, when layer 1 contains element (X), the element (X) is included in a range of 20:1 to 1:5, based on the composition ratio (at%) (Ru:X) of Ru in layer 1. If the content ratio of element (X) in layer 1 is greater than 20:1 based on the composition ratio (Ru:X), the inclusion of element (X) can achieve the effect of adjusting the EUV light reflectivity of the surface of the phase-shifting film 14. On the other hand, if the content ratio of element (X) in layer 1 is less than 1:5 based on the composition ratio (Ru:X), the film thickness required to obtain the specified phase difference can be reduced. The ratio of element (X) in layer 1, calculated as a composition ratio (Ru:X), is preferably in the range of 4:1 to 1:4, and more preferably in the range of 2:1 to 1:2.

[0047] In the first form of the phase shift film 14, when layer 1 contains element (X), it contains the sum of Ru and X (Ru+X) in the range of 40~99 at%, and O in the range of 1~60 at%, preferably Ru+X in the range of 50~99 at%, and O in the range of 1~50 at%, more preferably Ru+X in the range of 80~99 at%, and O in the range of 1~20 at%.

[0048] In the second form of the phase shift film 14, when layer 1 contains element (X), the total of Ru and X (Ru+X) is contained in the range of 30~98 at%, O is contained in the range of 1~69 at%, and N is contained in the range of 1~69 at%. More preferably, Ru+X is contained in the range of 50~98 at%, O is contained in the range of 1~30 at%, and N is contained in the range of 1~20 at%. More preferably, Ru+X is contained in the range of 70~98 at%, O is contained in the range of 1~20 at%, and N is contained in the range of 1~10 at%.

[0049] In the third form of the phase shift film 14, when layer 1 contains element (X), it contains the sum of Ru and X (Ru+X) in the range of 30~90 at%, and contains N in the range of 10~70 at%, preferably containing Ru+X in the range of 60~90 at%, and containing N in the range of 10~40 at%.

[0050] Furthermore, when the middle layer 1 of the phase shift film 14 contains two or more elements as elements (X), the X in the composition ratio (Ru:X) and the total of Ru and X (Ru+X) represents the total of two or more elements.

[0051] The phase shift film 14 can be constructed by stacking two or more of the first, second, and third types of layer 1. Furthermore, when the phase shift film 14 is constructed by stacking two or more of the first, second, and third types of layer 1, some layers may contain element (X), or all layers may contain element (X). When two or more layers contain element (X), the element (X) contained in each layer may be the same or different.

[0052] The phase shift film 14 may further have a layer 2, which contains at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V. The element (X) is preferably Cr, Ta, Pt, or Ir, and more preferably Cr or Ta. Layer 2 may further include at least one element selected from the group consisting of O, N, B and C. Furthermore, layer 2 does not contain Ru.

[0053] The phase shift film 14 may also have two or more layers 2 containing different elements.

[0054] By having the phase shift film 14 have layer 2, the reflectivity of EUV light can be adjusted. However, if the thickness of layer 2 is too thick, the reflectivity will become too low. Therefore, the ratio of the thickness of layer 1 to layer 2 ((thickness of layer 1):(thickness of layer 2)) is preferably in the range of 1:1 to 30:1, and more preferably in the range of 5:1 to 20:1. Furthermore, when the phase shift film 14 comprises two or more layers 1, the thickness of the aforementioned layer 1 is the total film thickness of the two or more layers 1. When the phase shift film 14 comprises two or more layers 2, the thickness of the aforementioned layer 2 is the total film thickness of the two or more layers 2.

[0055] When the phase shift film 14 has a layer 2, the arrangement of layer 1 and layer 2 in the phase shift film 14 is not particularly limited. Layer 2 can be formed on layer 1, or layer 1 can be formed on layer 2.

[0056] The first, second, and third morphologies of the phase-shifted film 14 can be formed using well-known film-forming methods such as magnetron sputtering and ion beam sputtering.

[0057] For example, when forming layer 1 of the first form of the phase shift film 14 using reactive sputtering, it is sufficient to use a Ru target as the target and a mixed gas containing an inert gas and O2 as the sputtering gas, and to carry out the film formation under the following conditions. Sputtering gas: a mixture of argon and O2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.010~0.50, preferably 0.010~0.30, more preferably 0.010~0.200; the gas pressure is 5×10-2 Pa~1.0 Pa, preferably 1×10-1 Pa~8×10-1 Pa, more preferably 2×10-1 Pa~4×10-1 Pa). The input power density per unit target area is 1.0 W / cm2 ~ 15.0 W / cm2, preferably 3.0 W / cm2 ~ 12.0 W / cm2, and even more preferably 4.0 W / cm2 ~ 10.0 W / cm2. Film formation rate: 0.010 nm / sec to 1.00 nm / sec, preferably 0.015 nm / sec to 0.500 nm / sec, and even more preferably 0.020 nm / sec to 0.300 nm / sec.

[0058] For example, when forming the second morphology of the phase shift film 14 using reactive sputtering, it is sufficient to use a Ru target as the target and a mixture of O2 and N2 or a mixture of inert gas, O2 and N2 as the sputtering gas, and carry out the film formation under the following conditions. Sputtering gas: a mixture of argon, O2 and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.010~0.75, preferably 0.010~0.500, more preferably 0.010~0.200; the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.010~0.75, preferably 0.010~0.500, more preferably 0.010~0.200; the gas pressure is 5×10-2 Pa~1.0 Pa, preferably 1×10-1 Pa~8×10-1 Pa, more preferably 2×10-1 Pa~4×10-1 Pa). The input power density per unit target area is 1.0 W / cm2 ~ 15.0 W / cm2, preferably 3.0 W / cm2 ~ 12.0 W / cm2, and even more preferably 4.0 W / cm2 ~ 10.0 W / cm2. Film formation rate: 0.010 nm / sec to 1.000 nm / sec, preferably 0.015 nm / sec to 0.500 nm / sec, and even more preferably 0.020 nm / sec to 0.300 nm / sec.

[0059] For example, when forming the third morphology of the phase shift film 14 using reactive sputtering, it is sufficient to use a Ru target as the target and nitrogen or a mixture of inert gas and N2 as the sputtering gas, and carry out the film formation under the following conditions. Sputtering gas: a mixture of nitrogen or argon and N2 (the volume ratio of nitrogen in the sputtering gas (N2 / (Ar+N2)) = 0.100~1.000, preferably 0.200~0.750, more preferably 0.250~0.500; the gas pressure is 5×10-2 Pa~1.0 Pa, preferably 1×10-1 Pa~8×10-1 Pa, more preferably 2×10-1 Pa~4×101 Pa). The input power density per unit target area is 1.0 W / cm2 ~ 15.0 W / cm2, preferably 3.0 W / cm2 ~ 12.0 W / cm2, and even more preferably 4.0 W / cm2 ~ 10.0 W / cm2. Film formation rate: 0.010 nm / sec to 1.000 nm / sec, preferably 0.015 nm / sec to 0.500 nm / sec, and even more preferably 0.020 nm / sec to 0.300 nm / sec.

[0060] When the phase shift film 14 includes layer 2, layer 2 can be formed using well-known film formation methods such as magnetron sputtering or ion beam sputtering.

[0061] For example, when forming a layer 2 containing Ta as element X and containing O and N using reactive sputtering, it is sufficient to use a Ta target as the target and a mixture of O2 and N2 or a mixture of inert gas, O2 and N2 as the sputtering gas, and carry out the film formation under the following conditions. Sputtering gas: a mixture of oxygen and N2 or a mixture of argon, O2 and N2 (the volume ratio of oxygen in the mixture (O2 / (O2 + N2) or O2 / (Ar+O2 + N2)) = 0.010~0.750, preferably 0.100~0.500, more preferably 0.200~0.500; the volume ratio of nitrogen in the mixture (N2 / (O2 + N2) or N2 / (Ar+O2 + N2)) = 0.010~0.750, preferably 0.010~0.500, more preferably 0.010~0.200; the gas pressure is 5×10-2 Pa~1.0 Pa, preferably 1×10-1 Pa~8×10-1 Pa, more preferably 2×10-1 Pa~4×10-1 Pa). The input power density per unit target area is 1.0 W / cm2 ~ 15.0 W / cm2, preferably 3.0 W / cm2 ~ 12.0 W / cm2, and even more preferably 4.0 W / cm2 ~ 10.0 W / cm2. Film formation rate: 0.010 nm / sec to 1.000 nm / sec, preferably 0.015 nm / sec to 0.500 nm / sec, and even more preferably 0.020 nm / sec to 0.300 nm / sec.

[0062] For example, when forming a layer 2 containing Cr as element X and containing N using reactive sputtering, it is sufficient to use a Cr target as the target and nitrogen or a mixture of inert gas and N2 as the sputtering gas, and carry out the film formation under the following conditions. Sputtering gas: a mixture of nitrogen or argon and N2 (the volume ratio of nitrogen in the sputtering gas (N2 / (Ar+N2)) = 0.100~1.000, preferably 0.200~0.750, more preferably 0.250~0.500; the gas pressure is 5×10-2 Pa~1.0 Pa, preferably 1×10-1 Pa~8×10-1 Pa, more preferably 2×10-1 Pa~4×10-1 Pa). The input power density per unit target area is 1.0 W / cm2 ~ 15.0 W / cm2, preferably 3.0 W / cm2 ~ 12.0 W / cm2, and even more preferably 4.0 W / cm2 ~ 10.0 W / cm2. Film formation rate: 0.010 nm / sec to 1.000 nm / sec, preferably 0.015 nm / sec to 0.500 nm / sec, and even more preferably 0.020 nm / sec to 0.300 nm / sec.

[0063] Furthermore, when using an inert gas other than Ar, the concentration of the inert gas is set to the same range as the argon concentration described above. Also, when using multiple inert gases, the total concentration of the inert gases is set to the same range as the argon concentration described above.

[0064] When the thickness of the phase shift film 14 in the EUV photomask substrate 1a is 20 nm or more, the optical characteristics required for the phase shift film of a halftone EUV photomask, as shown below, can be achieved, and therefore it is better. Furthermore, when the thickness of layer 1 in phase shift film 14 is 10 nm or more, the optical characteristics required for a phase shift film as a halftone EUV mask can be achieved, as shown below, and therefore it is better.

[0065] When the reflectance of light with a wavelength of approximately 13.5 nm is used as the EUV light reflectance of the phase-shifting film surface when EUV light in the wavelength range is irradiated onto the surface of the phase-shifting film 14 at an incident angle of 6 degrees, and the reflectance of light with a wavelength of approximately 13.5 nm is used as the EUV light reflectance of the multilayer reflective film surface when EUV light in the wavelength range is irradiated onto the surface of the multilayer reflective film 12 at an incident angle of 6 degrees, the relative reflectance of the EUV light reflectance of the phase-shifting film surface and the EUV light reflectance of the multilayer reflective film surface ((EUV light reflectance of the phase-shifting film surface / EUV light reflectance of the multilayer reflective film surface) × 100) is preferably 2% to 37%, more preferably 4% to 20%, and even more preferably 6% to 15%. Furthermore, the phase difference between the EUV light reflected from the multilayer reflective film 12 and the EUV light reflected from the phase shift film 14 is preferably 150 degrees to 250 degrees, and more preferably 180 degrees to 230 degrees.

[0066] The thickness of the phase shift film 14 in the EUV photomask substrate 1a is preferably 30 nm or more, and more preferably 35 nm or more. The thickness of layer 1 in phase shift film 14 is preferably 20 nm or more, and more preferably 30 nm or more. Furthermore, the thickness of layer 1 in phase shift film 14 is preferably 60 nm or less, and more preferably 55 nm or less.

[0067] When the thickness of the phase shift film 14 in the EUV photomask substrate 1a is less than 60 nm, the shadowing effect can be reduced, which is better. The use of halftone EUV lithography masks is, in principle, an effective method to improve resolution in EUV lithography. However, the optimal reflectivity in halftone EUV lithography masks depends on the exposure conditions or the pattern to be transferred, and cannot be generalized. Furthermore, since EUV exposure is a reflective exposure process, the incident light is incident from a slightly tilted direction (usually around 6°) rather than from a perpendicular direction, becoming reflected light on the EUV photomask. In the EUV photomask, the phase-shifting film is used for pattern processing, but because the EUV light is incident from a tilted direction, it produces shadows on the pattern. Therefore, depending on the incident direction and the pattern's orientation, the transfer resist pattern formed by the reflected light on the wafer may sometimes deviate from the original pattern position. This is called the shadowing effect, which is a problem inherent in EUV exposure. To reduce the shadowing effect, the length of the shadow needs to be shortened. To do this, the height of the pattern needs to be reduced as much as possible. To reduce the pattern height, the phase-shifting film needs to be made as thin as possible.

[0068] The thickness of the phase shift film 14 in the EUV photomask substrate 1a is preferably less than 55 nm, and more preferably less than 50 nm.

[0069] When forming patterns on layer 1 of the first, second and third forms of the phase shift film 14, dry etching is performed using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas. The phase shift film 14 is preferably capable of etching at an etching rate of 10 nm / min or higher when using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas for dry etching. As a mixture of O2 and halogen-based gases, a mixture of O2 containing 40 vol% or more but less than 100 vol%, preferably 75 vol% to 90 vol%, and containing more than 0 vol% but less than 60 vol%, preferably 10 vol% to 25 vol%, of chlorine-based or fluorine-based gases. As chlorine-based gases, Cl2, SiCl4, CHCl3, CCl4, BCl3, and mixtures thereof are used. As fluorine-based gases, CF4, CHF3, SF6, BF3, XeF2, and mixtures thereof are used.

[0070] In the first and second morphologies of the phase shift film 14, the introduction of O not only suppresses crystallization but also increases the etching rate during dry etching using O2 or a mixture of O2 and halogen-based gases (chlorine-based or fluorine-based gases) as the etching gas. Increasing the O content in layer 1 allows for etching at more than twice the speed compared to films containing only Ru, potentially leading to increased production capacity.

[0071] Furthermore, when the first, second, and third forms of the phase shift film 14 contain element (X) in layer 1, in order to form the pattern of the phase shift film, dry etching is also performed using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas. At this point, by selecting elements (X) such as Cr, V, Mn, and Re that form volatile oxides or acetylated halides, it is expected that patterns with less deposits on the sidewalls of the pattern can be formed.

[0072] When the phase shift film 14 is composed of only layer 1, the pattern of the phase shift film can be formed by dry etching using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas, thus simplifying the pattern formation process.

[0073] When the phase shift film 14 has layer 1 and layer 2, the pattern of the phase shift film can be formed by dry etching in stages using two or more etching gases as needed. For example, when the phase shift film 14 has a layer 1 and a layer 2 containing Ta as an element (X), the pattern of the phase shift film can be formed by dry etching of layer 1 with O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas, and by dry etching of layer 2 with halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas.

[0074] Furthermore, when layer 2 contains elements such as Cr, V, Mn, and Re that can form volatile oxides or acehalides, the pattern of the phase shift film can be formed simply by dry etching layers 1 and 2 using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas. Therefore, even if the phase shift film 14 has layers 1 and 2, the pattern formation process does not become complicated, and the pattern of the phase shift film can be formed easily.

[0075] Figure 2 is a schematic cross-sectional view showing another embodiment of the EUV photomask substrate of the present invention. In the EUV photomask substrate 1b shown in Figure 2, a multilayer reflective film 12 for reflecting EUV light, a protective film 13 for the multilayer reflective film 12, a phase shifting film 14 for shifting the phase of EUV light, and an etched masking film 15 are sequentially formed on the substrate 11 from the substrate side. Since the substrate 11, multilayer reflective film 12, protective film 13, and phase shift film 14 in the EUV photomask substrate 1b are the same as those in the EUV photomask substrate 1a, their descriptions are omitted.

[0076] Typically, it is known that resist can be thinned by depositing a layer of material (etch mask film) on the phase shift film that is resistant to the etching conditions of the phase shift film. That is, the resist can be thinned by forming an etch mask film to reduce the relative speed (etch selectivity) of the etch mask film when the etch speed of the phase shift film is set to 1 in the etching conditions of the phase shift film.

[0077] The etching selectivity of the etching mask film 15 under the etching conditions of the phase shift film 14 is required to be sufficiently high. Therefore, the etching mask film 15 is required to have high etching tolerance for dry etching using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas.

[0078] On the other hand, the etched masking film 15 is preferably removed by using an acidic or alkaline cleaning solution that can be used as a resist in EUV lithography. Specific examples of cleaning solutions used for the aforementioned purposes include: sulfuric acid-hydrogen peroxide mixture (SPM), ammonia-hydrogen peroxide mixture, and hydrofluoric acid. SPM is a solution obtained by mixing sulfuric acid and hydrogen peroxide, wherein the sulfuric acid and hydrogen peroxide are mixed in a volume ratio of 4:1 to 1:3, preferably 3:1. In this case, to improve the etching rate, it is preferable to control the temperature of the SPM at 100°C or higher. Ammonia-hydrogen peroxide mixture is a solution obtained by mixing ammonia and hydrogen peroxide, wherein NH4OH, hydrogen peroxide, and water are mixed in a volume ratio of 1:1:5 to 3:1:5. In this case, it is preferable to control the temperature of the ammonia-hydrogen peroxide mixture at 70°C to 80°C.

[0079] To meet the above requirements, the etching mask film 15 of the EUV photomask substrate 1b of the present invention preferably contains at least one element selected from the group consisting of Nb, Ti, Mo, Ta, and Si. The etching mask film 15 may further contain at least one element selected from the group consisting of O, N, and B. That is, it may also be an oxide, oxynitride, nitride, or boride of the above elements. Specific examples of the constituent materials of the etching mask film 15 include Nb-based materials such as Nb, Nb₂O₅, and NbON. The etching mask film 15 containing these Nb-based materials can be etched by dry etching using a chlorine-based gas as the etching gas. Furthermore, Mo-based materials such as Mo, MoO₃, and MoON can be used. The etching mask film 15 containing these Mo-based materials can be etched, for example, by dry etching using a chlorine-based gas as the etching gas. Furthermore, Si-based materials such as SiO₂ and Si₃N₄ can be used. The etching mask film 15 containing such Si-based materials can be etched, for example, by dry etching using a fluorine-based gas as the etching gas. Furthermore, when using Si-based materials as the etching mask film 15, it is preferable to use hydrofluoric acid as a cleaning solution to remove it.

[0080] Regarding the removability of the cleaning solution, the thickness of the etching mask film 15 is preferably 20 nm or less. For etching mask films 15 containing Nb-based materials, the thickness is more preferably 5 nm to 15 nm.

[0081] The etched mask film 15 can be formed by known film formation methods, such as magnetron sputtering or ion beam sputtering.

[0082] When forming NbN films by sputtering, reactive sputtering using an Nb target can be performed in a gas atmosphere obtained by mixing an inert gas (hereinafter referred to as inert gas only) containing at least one of He, Ar, Ne, Kr, and Xe with nitrogen. When using magnetron sputtering, specifically, it can be performed under the following film formation conditions. Sputtering gas: A mixture of argon and N2 (the volume ratio of N2 in the mixture (N2 / (Ar+N2)) = 15 vol% or more) Atmospheric pressure: 5.0 × 10⁻² ~ 1.0 Pa, preferably 1.0 × 10⁻¹ ~ 8.0 × 10⁻¹ Pa, even more preferably 2.0 × 10⁻¹ ~ 4.0 × 10⁻¹ Pa The applied power density per unit target area is 1.0 W / cm² to 15.0 W / cm², preferably 3.0 W / cm² to 12.0 W / cm², and even more preferably 4.0 W / cm² to 10.0 W / cm². Film formation rate: 0.010 nm / sec to 1.0 nm / sec, preferably 0.015 nm / sec to 0.50 nm / sec, and even more preferably 0.020 nm / sec to 0.30 nm / sec The distance between the target and the substrate is 50 mm to 500 mm, preferably 100 mm to 400 mm, and even more preferably 150 mm to 300 mm.

[0083] Furthermore, when using an inert gas other than Ar, the concentration of the inert gas is set to the same range as the argon concentration described above. Also, when using multiple inert gases, the total concentration of the inert gases is set to the same range as the argon concentration described above.

[0084] In addition to the multilayer reflective film 12, protective film 13, phase shift film 14, and etching mask film 15, the EUV photomask substrates 1a and 1b of the present invention may also have functional films known in the field of EUV photomask substrates. Specific examples of such functional films include, for instance, the high-dielectric coating added to the back side of the substrate to promote electrostatic adhesion, as described in Japanese Patent Publication No. 2003-501823. Here, the back side of the substrate, in substrate 11 of FIG. 1, refers to the side opposite to the side where the multilayer reflective film 12 is formed. For this purpose, the high-dielectric coating added to the back side of the substrate is selected with a sheet resistance of 100 Ω / □ or less in terms of conductivity and thickness. The high-dielectric coating material can be widely selected from materials described in known literature. For example, a high dielectric constant coating as described in Japanese Patent Publication No. 2003-501823 can be applied, specifically a coating containing Si, TiN, Mo, Cr, or TaSi. The thickness of the high dielectric coating can be set, for example, to 10~1000 nm. High dielectric coatings can be formed using known film formation methods, such as magnetron sputtering, ion beam sputtering, CVD (Chemical Vapor Deposition), vacuum evaporation, and electroplating.

[0085] The method for manufacturing the EUV photomask substrate of the present invention includes the following steps a) to c). a) Step of forming a multilayer reflective film on a substrate to reflect EUV light. b) The step of forming a phase shift film on the multilayer reflective film formed in step a). c) The step of forming an etching mask film on the phase shift film formed in step c) According to the manufacturing method of the EUV photomask substrate of the present invention, the EUV photomask substrate 1b shown in FIG2 can be obtained.

[0086] Figure 3 is a schematic cross-sectional view showing one embodiment of the EUV photomask of the present invention. In the EUV photomask 2 shown in Figure 3, a pattern (phase shift film pattern) 140 is formed on the phase shift film 14 of the EUV photomask substrate 1a shown in Figure 1. That is, a multilayer reflective film 12 that reflects EUV light, a protective film 13 of the multilayer reflective film 12, and a phase shift film 14 that shifts the phase of EUV light are sequentially formed on the substrate 11 from the substrate side, and a pattern (phase shift film pattern) 140 is formed on the phase shift film 14. The components of the EUV photomask 2, including the substrate 11, the multilayer reflective film 12, the protective film 13, and the phase shift film 14, are the same as those of the EUV photomask substrate 1a.

[0087] In the EUV photomask manufacturing method of the present invention, the phase shift film 14 of the EUV photomask substrate 1b manufactured by the EUV photomask substrate manufacturing method of the present invention is patterned to form a pattern (phase shift film pattern) 140. Referring to the diagram, the steps for forming a pattern on the phase shift film 14 of the EUV photomask substrate 1b will be described. As shown in Figure 4, a resist film 30 is formed on the etching mask film 15 of the EUV photomask substrate 1b. Then, using an electron beam plotter, as shown in Figure 5, a resist pattern 300 is formed on the resist film 30. Next, using the resist film 30 with the resist pattern 300 as a mask, an etching mask film pattern 150 is formed on the etching mask film 15, as shown in Figure 6. When forming the pattern of the etching mask film 15 containing Nb-based materials, dry etching using a chlorine-based gas as the etching gas is sufficient. Then, using the etching mask film 15 with the etching mask film pattern 150 as a mask, a phase shift film pattern 140 is formed on the phase shift film 14, as shown in Figure 7. When forming the pattern of the phase shift film 14 containing Ru, dry etching using O2 or a mixture of O2 and halogen-based gases (chlorine-based gases, fluorine-based gases) as the etching gas is sufficient. Subsequently, the resist film 30 and the etching mask film 15 are removed using an acidic or alkaline cleaning solution, thereby obtaining an EUV mask 2 that exposes the phase shift film pattern 140. Furthermore, most of the resist pattern 300 and resist film 30 are removed during the formation of the phase shift film pattern 140, but in order to remove the residual resist pattern 300, resist film 30 and etching mask film 15, cleaning is performed using an acidic or alkaline cleaning solution. [Example]

[0088] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments. In Examples 1 to 24, Examples 1 to 17 are embodiments, and Examples 18 to 24 are comparative examples.

[0089] (Example 1) In Example 1, the EUV photomask substrate 1a shown in Figure 1 is fabricated. A SiO2-TiO2 glass substrate (6 inches (152 mm) square, 6.3 mm thick) was used as the substrate 11 for film formation. The glass substrate had a coefficient of thermal expansion of 0.02 × 10⁻⁷ / ℃ at 20°C, a Young's modulus of 67 GPa, a Pascal's ratio of 0.17, and a specific stiffness of 3.07 × 10⁷ m² / s². Through grinding, the glass substrate was made to have a smooth surface with a surface roughness (RMS) of less than 0.15 nm and a flatness of less than 100 nm.

[0090] On the back side of substrate 11, a 100 nm thick Cr film is formed by magnetron sputtering, thereby increasing the high dielectric coating with a sheet resistance of 100 Ω / □. The Cr film formed by the separator is used to fix the substrate 11 (6 inches (152 mm) square and 6.3 mm thick) on a conventional electrostatic chuck in the shape of a flat plate. On the surface of the substrate 11, Si film and Mo film are alternately formed by ion beam sputtering. This alternating film formation is repeated for 40 cycles to form a Si / Mo multilayer reflective film 12 with a total film thickness of 272 nm ((4.5 nm + 2.3 nm) × 40). Furthermore, a RuZr film (2.5 nm thick) is deposited on the Si / Mo multilayer reflective film 12 using DC sputtering, thereby forming a protective film 13.

[0091] The film formation conditions for Si, Mo, and Ru films are as follows. (Conditions for Si film formation) Target: Si target (boron-doped) Sputtering gas: Argon (pressure 2.0 × 10⁻² Pa) Voltage: 700 V Film formation rate: 0.077 nm / sec Film thickness: 4.5 nm (Film-forming conditions of Mo films) Target: Mo target Sputtering gas: Argon (pressure 2.0 × 10⁻² Pa) Voltage: 700 V Film formation rate: 0.064 nm / sec Film thickness: 2.3 nm (Film-forming conditions of RuZr films) Target: Ru target Zr target Sputtering gas: Argon (pressure 2.0 × 10⁻² Pa) Ru input power: 500 W Zr input power: 150 W Film formation rate: 0.073 nm / sec Film thickness: 2.5 nm

[0092] Subsequently, a phase shift film 14 containing Ru and O, layer 1 (RuOx film), is formed on the protective film using a reactive sputtering method. In this embodiment, the phase shift film 14 consists only of layer 1. The film formation conditions of layer 1 of the phase shift film 14 are described below. (RuOx membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon and O2 (volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.030, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.170 nm / sec Film thickness: 39 nm

[0093] The EUV photomask substrate 1a obtained by the above steps was evaluated as follows (1) to (7). The same evaluation results were also obtained for the substrate obtained by forming a RuOx film on a silicon wafer as described in (1) to (7).

[0094] (1) Membrane composition The composition of the RuOx film was determined using an X-ray photoelectron spectroscopy system (manufactured by ULVAC-PHI). The composition ratio (at%) of the RuOx film was Ru:O = 91:9.

[0095] (2) Calculation of phase difference and relative reflectivity in the EUV wavelength region The phase difference between the EUV light reflected from the multilayer reflective film 12 and the EUV light reflected from the phase-shifting film 14, and the relative reflectivity of the EUV light on the surface of the phase-shifting film 14 and the surface of the multilayer reflective film 12 were determined through optical simulation. The optical constants of the multilayer reflective film 12 required for the simulation were values ​​obtained from the database of the X-ray Optics Center at Lawrence Berkeley National Laboratory. The optical constants of the phase-shifting film 14 were values ​​obtained from the database of the X-ray Optics Center at Lawrence Berkeley National Laboratory or were evaluated by measuring the "angular dependence" of the reflectivity of light in the 13.5 nm region. Specifically, EUV reflectivity, the incident angle of EUV light, and optical constants are expressed by the following formula. R=|(sinθ-((n+ik)2 -cos2 θ)1 / 2 ) / (sinθ+((n+ik)2 -cos2 θ)1 / 2 )| Here, θ is the incident angle of EUV light, R is the EUV reflectivity at the incident angle θ, n is the refractive index of the phase shift film 14, and k is the extinction coefficient of the phase shift film 14. By fitting the measured reflectivity values ​​at each EUV incident angle using the above formula, the EUV optical constants (refractive index (n) and extinction coefficient (k)) can be estimated. The phase-shifting film 14 has a refractive index (n) of 0.900 and an extinction coefficient (k) of 0.017. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 31.9%.

[0096] (3) Crystallization peaks from the phase-shifted film The phase-shifted film (RuOx film) was measured using out-of-plane XRD. The full width at half maximum (FWHM) was determined for the highest intensity peak among the diffraction peaks originating from the phase-shifted film observed at 2θ: 20°–50°. The full width at half maximum (FWHM) is 1.0°, and the phase-shifted film (RuOx film) has an amorphous crystalline structure.

[0097] (4) Etching rate A sample with a phase-shifted film (RuOx film) was placed on the sample stage of an ICP (Inductively Coupled Plasma) etching apparatus, and ICP plasma etching was performed under the conditions shown below to determine the etching rate. ICP antenna bias: 200 W Substrate bias: 40 W Etching time: 30 sec Trigger pressure: 3.0 × 100 Pa Etching pressure: 3.0 × 10⁻¹ Pa Etching gas: a mixture of O2 and Cl2 Gas flow rate (Cl2 / O2): 10 / 10 sccm The etching rate is 25 nm / min.

[0098] (Example 2) In Example 2, the film formation conditions of layer 1 (RuOx film) of phase shift film 14 are set as follows, and the same steps as in Example 1 are performed. (RuOx membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon and O2 (volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.04, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.22 nm / sec Film thickness: 45 nm The composition ratio (at%) of the RuOx membrane is Ru:O = 76:24. The RuOx film has a refractive index (n) of 0.912 and an extinction coefficient (k) of 0.019. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 23.5%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuOx film) is 2.6°, and the crystalline structure of the phase-shifted film (RuOx film) is amorphous. The etching rate of the phase-shifted film (RuOx film) is 36 nm / min.

[0099] (Example 3) In Example 3, the film formation conditions of layer 1 (RuOx film) of phase shift film 14 are set as follows, and the same steps as in Example 1 are performed. (RuOx membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon and O2 (volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.05, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.22 nm / sec Film thickness: 45 nm The composition ratio (at%) of the RuOx membrane is Ru:O = 67:33. The RuOx film has a refractive index (n) of 0.919 and an extinction coefficient (k) of 0.020. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 15.2%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuOx film) is 3.2°, and the crystalline structure of the phase-shifted film (RuOx film) is amorphous. The etching rate of the phase-shifted film (RuOx film) is 41 nm / min.

[0100] (Example 4) In Example 4, a phase shift film 14 (RuN film) containing Ru and N was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are as follows. (Film-forming conditions of RuN films) Target: Ru target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.5, pressure: 2.0×10-1 Pa). Power density per unit target area: 1.7 W / cm² Film formation rate: 0.017 nm / sec Film thickness: 39 nm The composition ratio (at%) of the RuN membrane is Ru:N = 98:2. The RuN film has a refractive index (n) of 0.890 and an extinction coefficient (k) of 0.016. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 35.4%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuN film) is 1.2°, and the crystalline structure of the phase-shifted film (RuN film) is amorphous. The etching rate of the phase-shifted film (RuN film) is 23 nm / min.

[0101] (Example 5) In Example 5, a phase shift film 14 (RuON film) containing Ru, O and N was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are as follows. (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.013, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, and the pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.13 nm / sec Film thickness: 39 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 93:2:5 (Ru:O+N=93:7). The RuON film has a refractive index (n) of 0.901 and an extinction coefficient (k) of 0.017. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 31.8%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuON film) is 1.9°, and the crystalline structure of the phase-shifted film (RuON film) is amorphous. The etching rate of the phase-shifted film (RuON film) is 26 nm / min.

[0102] (Example 6) In Example 6, the film formation conditions of layer 1 (RuON film) of phase shift film 14 are set as follows, and the same steps as in Example 5 are followed. (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.026, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.17 nm / sec Film thickness: 39 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 76:14:10 (Ru:O+N=76:24). The RuON film has a refractive index (n) of 0.912 and an extinction coefficient (k) of 0.019. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 23.5%. Since no crystallization peaks originating from the phase-shifted film (RuON film) were observed, the full width at half maximum (FWHM) was 180°, and the crystalline structure of the phase-shifted film (RuON film) was amorphous. The etching rate of the phase-shifted film (RuON film) is 32 nm / min.

[0103] (Example 7) In Example 7, the film formation conditions of layer 1 (RuON film) of phase shift film 14 are set as follows, and the same steps as in Example 5 are followed. (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.051, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.19, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.21 nm / sec Film thickness: 46 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 62:29:9 (Ru:O+N=62:38). The RuON film has a refractive index (n) of 0.919 and an extinction coefficient (k) of 0.020. The phase difference in the EUV wavelength region is 1.2 degrees, and the relative reflectivity is 11.8%. Since no crystallization peaks originating from the phase-shifted film (RuON film) were observed, the full width at half maximum (FWHM) was 180°, and the crystalline structure of the phase-shifted film (RuON film) was amorphous. The etching rate of the phase-shifted film (RuON film) is 35 nm / min.

[0104] (Example 8) In Example 8, the film formation conditions of layer 1 (RuON film) of phase shift film 14 are set as follows, and the same steps as in Example 5 are followed. (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.17, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.17, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.20 nm / sec Film thickness: 52 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 38:51:11 (Ru:O+N=38:62). The RuON film has a refractive index (n) of 0.922 and an extinction coefficient (k) of 0.021. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 15.7%. Since no crystallization peaks originating from the phase-shifted film (RuON film) were observed, the full width at half maximum (FWHM) was 180°, and the crystalline structure of the phase-shifted film (RuON film) was amorphous. The etching rate of the phase-shifted film (RuON film) is 37 nm / min.

[0105] (Example 9) In Example 9, a phase shift film 14 layer 1 (RuCrN film) comprising Ru, Cr and N was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are described below. (Film-forming conditions of RuCrN films) Target: Ru target Cr target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 1, pressure: 2.5×10-1 Pa). Power density per unit target area: Rutarget 4.9 W / cm2 Cr target 9.9 W / cm2 Film formation rate: 0.10 nm / sec Film thickness: 52 nm The composition ratio (at%) of the Ru:Cr:N membrane is Ru:Cr:N = 37:33:30 (Ru+Cr:N=70:30,Cr / Ru=0.9). The RuCrN film has a refractive index (n) of 0.921 and an extinction coefficient (k) of 0.023. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 8.7%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuCrN film) is 2.3°, and the crystalline structure of the phase-shifted film (RuCrN film) is amorphous. The etching rate of the phase-shifted film (RuCrN film) was not determined.

[0106] (Example 10) In Example 10, a phase shift film 14 (RuCrON film) comprising Ru, Cr, O and N was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are described below. (Film-forming conditions of RuCrON membranes) Target: Ru target Cr target Sputtering gas: a mixture of argon, N2, and O2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.033, and the pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: Rutarget 4.9 W / cm2 Cr target 9.9 W / cm2 Film formation rate: 0.31 nm / sec Film thickness: 52 nm The composition ratio (at%) of the RuCrON membrane is Ru:Cr:O:N = 14:35:41:10 (Ru+Cr:O+N=49:51,Cr / Ru=2.5). The RuCrON film has a refractive index (n) of 0.923 and an extinction coefficient (k) of 0.031. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 12.6%. Since no crystallization peaks originating from the phase-shifted film (RuCrON film) were observed, the full width at half maximum (FWHM) was 180°, and the crystalline structure of the phase-shifted film (RuCrON film) was amorphous. The etching rate of the phase-shifted film (RuCrON film) was not determined.

[0107] (Example 11) In Example 11, a phase shift film 14 (RuReON film) comprising Ru, Re, O and N was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are described below. (RuReON membrane formation conditions) Target: Ru target Re target Sputtering gas: a mixture of argon, N2, and O2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.1, and the gas pressure is 3.0 × 10⁻¹ Pa). Power density per unit target area: Rutarget 2.5 W / cm2 Re target 7.4 W / cm2 Film formation rate: 0.16 nm / sec Film thickness: 52 nm The composition ratio (at%) of the RuReON membrane is Ru:Re:O:N = 16:71:2:11 (Ru+Re:O+N=87:13,Re / Ru=4.4). The RuReON film has a refractive index (n) of 0.928 and an extinction coefficient (k) of 0.029. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 6.1%. The full width at half maximum (FWHM) of the crystallization peak derived from the phase-shifted film (RuReON film) is 4°, and the crystalline structure of the phase-shifted film (RuReON film) is amorphous. The etching rate of the phase-shifted film (RuReON film) was not determined.

[0108] (Example 12) In Example 12, the film formation conditions of layer 1 (RuReON film) of phase shift film 14 are set to the following conditions, and the same steps as in Example 11 are performed. (RuReON membrane formation conditions) Target: Ru target Re target Sputtering gas: a mixture of argon, N2, and O2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.016, and the pressure is 3.0 × 10⁻¹ Pa). Power density per unit target area: Ru_target 7.4 W / cm² Re target 7.4 W / cm2 Film formation rate: 0.30 nm / sec Film thickness: 52 nm The composition ratio (at%) of the RuReON membrane is Ru:Re:O:N = 41:48:2:9 (Ru+Re:O+N=89:11,Re / Ru=1.2). The RuReON film has a refractive index (n) of 0.914 and an extinction coefficient (k) of 0.026. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 14.2%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuReON film) is 1.3°, and the crystalline structure of the phase-shifted film (RuReON film) is amorphous. The etching rate of the phase-shifted film (RuReON film) was not determined.

[0109] (Example 13) In Example 13, the film formation conditions of layer 1 (RuReON film) of phase shift film 14 are set to the following conditions, and the same steps as in Example 11 are performed. (RuReON membrane formation conditions) Target: Ru target Re target A mixture of argon, N2, and O2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.016, and the pressure is 3.0 × 10⁻¹ Pa). Power density per unit target area: Ru_target 7.4 W / cm² Re target 2.5 W / cm2 Film formation rate: 0.19 nm / sec Film thickness: 44 nm The composition ratio (at%) of the RuReON membrane is Ru:Re:O:N = 71:18:3:8 (Ru+Re:O+N=89:11, Re / Ru=0.3). The RuReON film has a refractive index (n) of 0.904 and an extinction coefficient (k) of 0.020. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 21.0%. The full width at half maximum (FWHM) of the crystallization peak derived from the phase-shifted film (RuReON film) is 3°, and the crystalline structure of the phase-shifted film (RuReON film) is amorphous. The etching rate of the phase-shifted film (RuReON film) was not determined.

[0110] (Example 14) In Example 14, the film formation conditions of layer 1 (RuCrN film) of phase shift film 14 are set to the following conditions, and the same steps as in Example 9 are performed. (Film-forming conditions of RuCrN films) Target: Ru target Cr target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.17, pressure: 2.0×10-1 Pa). Power density per unit target area: Rutarget 3.7 W / cm2 Cr target 4.9 W / cm2 Film formation rate: 0.07 nm / sec Film thickness: 40 nm The composition ratio (at%) of the Ru:Cr:N membrane is Ru:Cr:N = 42:44:14. (Ru+Cr:N=86:14,Cr / Ru=1). The RuCrN film has a refractive index (n) of 0.920 and an extinction coefficient (k) of 0.024. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 10.2%. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuCrN film) is 2.8°, and the crystalline structure of the phase-shifted film (RuCrN film) is amorphous. The etching rate of the phase-shifted film (RuCrN film) was not determined.

[0111] (Example 15) In Example 15, a phase shift film 14 layer 1 (RuCrO film) containing Ru, Cr, and O was formed on the protective film using reactive sputtering. Otherwise, the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 layer 1 are described below. (Film-forming conditions of RuCrO membranes) Target: Ru target Cr target Sputtering gas: a mixture of argon and O2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.2, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: Ru_target 7.4 W / cm² Cr target 5.9 W / cm2 Film formation rate: 0.49 nm / sec Film thickness: 40 nm The composition ratio (at%) of the Ru:Cr:O membrane is Ru:Cr:O = 20:30:50. (Ru+Cr:O=50:50,Cr / Ru=0.6). The RuCrO film has a refractive index (n) of 0.929 and an extinction coefficient (k) of 0.027. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 7.3%. Since no crystallization peaks originating from the phase-shifted film (RuCrO film) were observed, the full width at half maximum (FWHM) was 180°, and the crystalline structure of the phase-shifted film (RuCrO film) was amorphous. The etching rate of the phase-shifted film (RuCrO film) was not determined.

[0112] (Example 16) In Example 16, a layer 1 (RuON film) containing Ru, O and N phase shift film 14 is formed on the protective film using reactive sputtering, and a layer 2 (TaON film) containing Ta, O and N phase shift film 14 is formed using reactive sputtering. Otherwise, the same steps as in Example 1 are performed. The film formation conditions for layers 1 and 2 of the phase shift film 14 are as follows. (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.17, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.17, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.20 nm / sec Film thickness: 48 nm (TaON membrane formation conditions) Target: Ta target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.4, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.1, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.10 nm / sec Film thickness: 4 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 38:51:11 (Ru:O+N=38:62). The RuON film has a refractive index (n) of 0.922 and an extinction coefficient (k) of 0.021. The TaON film has a refractive index (n) of 0.955 and an extinction coefficient (k) of 0.025. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 12.9%. Since no crystallization peaks originating from the phase shift films (layer 1 (RuON film) and layer 2 (TaON film)) were observed, the full width at half maximum (FWHM) was 180°. The crystalline structure of the phase shift film 14, which includes layer 1 (RuON film) and layer 2 (TaON film), is amorphous. The etching rates of layer 1 (RuON film) and layer 2 (TaON film) of phase offset film 14 were not measured.

[0113] (Example 17) In Example 17, a layer 2 (CrN film) containing a phase shift film 14 of Cr and N is formed on the protective film using reactive sputtering, and a layer 1 (RuON film) containing a phase shift film 14 of Ru, O and N is formed using reactive sputtering. Otherwise, the same steps as in Example 1 are performed. The film formation conditions for layer 2 and layer 1 of phase shift film 14 are as follows. (Film-forming conditions for CrN films) Target: Cr target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.2, pressure: 2.0×10-1 Pa). Power density per unit target area: 9.9 W / cm² Film formation rate: 0.09 nm / sec Film thickness: 4 nm (RuON membrane formation conditions) Target: Ru target Sputtering gas: a mixture of argon, O2, and N2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.17, the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.17, and the gas pressure is 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.20 nm / sec Film thickness: 48 nm The composition ratio (at%) of the RuON membrane is Ru:O:N = 38:51:11 (Ru:O+N=38:62). The RuON film has a refractive index (n) of 0.922 and an extinction coefficient (k) of 0.021. The CrN film has a refractive index (n) of 0.928 and an extinction coefficient (k) of 0.039. The phase difference in the EUV wavelength region is 216 degrees, and the relative reflectivity is 13.6%. The full width at half maximum (FWHM) of the crystallization peaks originating from the phase-shifted films (layer 2 (CrN film) and layer 1 (RuON film)) is 3.6°. The crystalline structure of the phase-shifted film 14, which includes layer 2 (CrN film) and layer 1 (RuON film), is amorphous. The etching rates of layer 2 (CrN film) and layer 1 (RuON film) of phase shift film 14 were not measured.

[0114] (Example 18) In Example 18, a phase shift film 14 (Ru film) containing Ru was formed on a protective film using DC sputtering, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (Film-forming conditions of Ru membranes) Target: Ru target Sputtering gas: Argon (pressure: 2.0 × 10⁻¹ Pa) Power density per unit target area: 7.4 W / cm² Film formation rate: 0.14 nm / sec Film thickness: 40 nm The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (Ru film) is 0.42°, and the crystal structure of the phase-shifted film (Ru film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (Ru film) was not determined.

[0115] (Example 19) In Example 19, a phase shift film 14 (RuO2 film) containing Ru and O was formed on a protective film using reactive sputtering, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (RuO2 membrane formation conditions) Target: Ru target A mixture of argon and O2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.13, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.26 nm / sec Film thickness: 40 nm The composition ratio (at%) of the RuO2 membrane is Ru:O = 38:62. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuO2 film) is 0.82°, and the crystal structure of the phase-shifted film (RuO2 film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuO2 film) was not determined.

[0116] (Example 20) In Example 20, a phase shift film 14 (RuCr film) containing Ru and Cr was formed on a protective film using a binary sputtering method, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (Film-forming conditions for RuCr membranes) Target: Ru target Cr target Sputtering gas: Argon (pressure: 2.0 × 10⁻¹ Pa) Power density per unit target area: Ru_target 7.4 W / cm² Cr target 4.9 W / cm2 Film formation rate: 0.21 nm / sec Film thickness: 40 nm The composition ratio (at%) of the Ru:Cr membrane is Ru:Cr = 65:35. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuCr film) is 0.34°, and the crystal structure of the phase-shifted film (RuCr film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuCr film) was not determined.

[0117] (Example 21) In Example 21, a phase shift film 14 (RuRe film) containing Ru and Re is formed on a protective film using a binary sputtering method, except that the same steps as in Example 1 are performed. The film formation conditions for the phase shift film 14 are as follows. (Film-forming conditions of RuRe membranes) Target: Ru target Re target Sputtering gas: Argon (pressure: 2.0 × 10⁻¹ Pa) Power density per unit target area: Ru_target 7.4 W / cm² Re target 7.4 W / cm2 Film formation rate: 0.25 nm / sec Film thickness: 40 nm The composition ratio (at%) of the Ru:Re membrane is Ru:Re = 50:50. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuRe film) is 0.40°, and the crystal structure of the phase-shifted film (RuRe film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuRe film) was not determined.

[0118] (Example 22) In Example 22, a phase shift film 14 (RuN film) containing Ru and N was formed on a protective film using reactive sputtering, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (Film-forming conditions of RuN films) Target: Ru target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.2, pressure: 2.0×10-1 Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.07 nm / sec Film thickness: 40 nm The composition ratio (at%) of the RuN membrane is Ru:N = 99:1. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuN film) is 0.72°, and the crystal structure of the phase-shifted film (RuN film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuN film) was not determined.

[0119] (Example 23) In Example 23, a phase shift film 14 (RuReN film) containing Ru, Re, and N was formed on a protective film using reactive sputtering, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (RuReN film formation conditions) Target: Ru target Re target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.04, pressure: 3.0 × 10⁻¹ Pa). Power density per unit target area: Ru_target 7.4 W / cm² Re target 7.4 W / cm2 Film formation rate: 0.32 nm / sec Film thickness: 40 nm The composition ratio (at%) of the Ru:Re:N membrane is Ru:Re:N = 41:58:1 (Ru+Re:N=99:1,Re / Ru=0.7). The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuReN film) is 0.4°, and the crystal structure of the phase-shifted film (RuReN film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuReN film) was not determined.

[0120] (Example 24) In Example 24, a phase shift film 14 (RuCrN film) containing Ru, Cr, and N was formed on a protective film using a reactive sputtering method, except that the same steps as in Example 1 were performed. The film formation conditions for the phase shift film 14 are described below. (Film-forming conditions of RuCrN films) Target: Ru target Cr target Sputtering gas: a mixture of argon and N2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+N2)) = 0.09, pressure: 2.0 × 10⁻¹ Pa). Power density per unit target area: Ru_target 7.4 W / cm² Cr target 7.4 W / cm2 Film formation rate: 0.24 nm / sec Film thickness: 40 nm The composition ratio (at%) of the RuCrN membrane is Ru:Cr:N = 61:31:8. The full width at half maximum (FWHM) of the crystallization peak originating from the phase-shifted film (RuCrN film) is 0.52°, and the crystal structure of the phase-shifted film (RuCrN film) is crystalline. The phase difference and relative reflectivity in the EUV wavelength region were not measured. The etching rate of the phase-shifted film (RuCrN film) was not determined.

[0121] (Example for reference) In the reference example, a phase shift film 14, comprising Ru and O, or Ru, O, and N, is formed on a Si wafer using reactive sputtering (a layer 1 of RuOx film or RuOx N film). The film formation conditions for the phase shift film 14 layer 1 are described below. Furthermore, the purpose of expressing the volume ratio of oxygen in the mixed gas as a range is to prepare multiple samples under conditions with different volume ratios of oxygen in the mixed gas. (RuOx membrane formation conditions) Target: Ru target A mixture of argon and O2 (the volume ratio of oxygen in the mixture (O2 / (Ar+O2)) = 0.03~0.17, pressure: 2.0×10-1 Pa). Power density per unit target area: 7.4 W / cm² Film formation rate: 0.13~0.30 nm / sec Film thickness: 40 nm (Film-forming conditions of RuOx N films) Target: Ru target A mixture of argon, N2, and O2 (the volume ratio of nitrogen in the mixture (N2 / (Ar+O2+N2)) = 0.2, the volume ratio of oxygen in the mixture (O2 / (Ar+O2+N2)) = 0.026~0.17, and the pressure is 2.0×10-1 Pa). Input power: 150 W Film formation rate: 0.13~0.30 nm / sec Film thickness: 40 nm The surface roughness (RMS) of the phase-shifted film 14 (RuOx film, RuOx N film) was measured using an atomic force microscope. Alternatively, the surface roughness (RMS) can be measured according to JIS-B0601-2001. Figure 8 is a graph showing the relationship between the full width at half maximum (FWHM) (°) and the surface roughness (RMS) of the phase-shifting film in the reference example. As shown in Figure 8, whether it is a RuOx film or a RuOx N film, when the full width at half maximum (FWHM) of the phase shift film 14 is above 1.0°, the surface roughness (RMS) of the phase shift film 14 becomes below 0.3 nm.

[0122] The invention has been described in detail with reference to specific embodiments, but those skilled in the art will understand that various changes or modifications may be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-127311, filed on July 28, 2020, the contents of which are incorporated herein by reference.

[0123] 1a: EUV photomask substrate 1b: EUV photomask substrate 2: EUV photomask 11:Substrate 12: Multilayer reflective film 13: Protective film 14: Phase shifting film 15: Etching mask film 30: Anti-corrosion film 140: Phase-shifted film pattern 150: Etched masking film pattern 300: Anti-corrosion pattern

Claims

1. A reflective photomask substrate for EUV lithography, characterized in that: it comprises, sequentially formed on a substrate, a multilayer reflective film for reflecting EUV light and a phase shifting film for shifting the phase of EUV light, wherein the phase shifting film has a layer 1 comprising ruthenium (Ru) and at least one of the group consisting of oxygen (O) and nitrogen (N); and the full width at half maximum (FWHM) of the highest intensity peak observed at 2θ: 20° to 50° from the phase shifting film by out-of-plane XRD is 1.0° or more, wherein the layer 1 comprises Ru in the range of 40 to 99 at% and O in the range of 1 to 60 at%, or comprises Ru in the range of 30 to 98 at% and O in the range of 1 to 69 at% and N in the range of 1 to 69 at%.

2. A reflective photomask substrate for EUV lithography, characterized in that: it comprises, sequentially formed on a substrate, a multilayer reflective film for reflecting EUV light and a phase shifting film for shifting the phase of EUV light, wherein the phase shifting film has a layer 1 comprising ruthenium (Ru) and at least one of the group consisting of oxygen (O) and nitrogen (N); and the full width at half maximum (FWHM) of the highest intensity peak observed at 2θ: 20° to 50° from the phase shifting film by out-of-plane XRD is 1.0° or more, wherein the layer 1 comprises Ru in the range of 30 to 98 at% and N in the range of 2 to 70 at%.

3. A reflective photomask substrate for EUV lithography, characterized in that: it comprises, sequentially formed on a substrate, a multilayer reflective film for reflecting EUV light and a phase shifting film for shifting the phase of EUV light, wherein the phase shifting film has a layer 1, the layer 1 comprising ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N); and the full width at half maximum (FWHM) of the highest intensity peak observed at 2θ: 20° to 50° from the phase shifting film by out-of-plane XRD is 1.0° or more, wherein the phase shifting film further comprises a layer 2, the layer 2 comprising at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V.

4. The EUV lithography reflective photomask substrate of claim 1, wherein the aforementioned layer 1 further comprises at least one element (X) selected from the group consisting of chromium (Cr), tantalum (Ta), titanium (Ti), rhenium (Re), tungsten (W), bismuth (Bi), manganese (Mn), platinum (Pt), copper (Cu), iridium (Ir) and vanadium (V) in a Ru to X composition ratio (at%) of 20:1 to 1:5, and comprises the sum of Ru and X (Ru+X) in a range of 40 to 99 at%, and O in a range of 1 to 60 at%, or, comprises the sum of Ru and X (Ru+X) in a range of 30 to 98 at%, and O in a range of 1 to 69 at%, and N in a range of 1 to 69 at%.

5. The EUV lithography reflective photomask substrate of claim 2, wherein the aforementioned layer 1 further comprises at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V in a composition ratio (at%) of Ru to X of 20:1 to 1:5, and comprises the sum of Ru and X (Ru+X) in a range of 30 to 90 at%, and comprises N in a range of 10 to 70 at%.

6. The EUV lithography reflective photomask substrate of claim 3, wherein the layer 2 further comprises at least one element selected from the group consisting of O, N, boron (B) and carbon (C).

7. The EUV lithography reflective photomask substrate of any one of claims 1 to 6, wherein the thickness of the phase shift film is 20 nm to 60 nm.

8. The EUV lithography reflective photomask substrate of any one of claims 1 to 6, wherein the thickness of the aforementioned layer 1 is 10 nm or more.

9. The EUV lithography reflective photomask substrate according to any one of claims 1 to 6, wherein the phase difference between the reflected EUV light from the aforementioned multilayer reflective film and the reflected EUV light from the aforementioned phase-shifting film is 150 degrees to 250 degrees, and the relative reflectivity of the EUV light reflectivity of the surface of the aforementioned phase-shifting film and the EUV light reflectivity of the surface of the aforementioned multilayer reflective film ((EUV light reflectivity of the surface of the phase-shifting film / EUV light reflectivity of the surface of the multilayer reflective film) × 100) is 2% to 37%.

10. The EUV lithography reflective photomask substrate of any one of claims 1 to 6, wherein a protective film of the multilayer reflective film is formed between the multilayer reflective film and the phase shift film.

11. The EUV lithography reflective photomask substrate of claim 10, wherein the protective film comprises at least one element selected from the group consisting of Ru, palladium (Pd), Ir, rhodium (Rh), Pt, zirconium (Zr), niobium (Nb), Ta, Ti and silicon (Si).

12. The EUV lithography reflective photomask substrate of claim 11, wherein the protective film further comprises at least one element selected from the group consisting of O, N, and B.

13. An EUV lithography reflective photomask substrate as claimed in any one of claims 1 to 6, wherein an etch mask film is provided on the phase shift film, the etch mask film comprising at least one element selected from the group consisting of Nb, Ti, molybdenum (Mo), Ta and Si.

14. The EUV lithography reflective photomask substrate of claim 13, wherein the etched mask film further comprises at least one element selected from the group consisting of O, N, and B.

15. A reflective photomask for EUV lithography, wherein a pattern is formed on the phase offset film of the reflective photomask substrate for EUV lithography as claimed in any one of claims 1 to 14.

16. A method for manufacturing a reflective photomask substrate for EUV lithography, characterized by comprising the following steps: forming a multilayer reflective film on a substrate to reflect EUV light; forming a phase shifting film on the multilayer reflective film to shift the phase of EUV light; and forming an etching mask film on the phase shifting film; wherein the phase shifting film has a layer 1, the layer 1 comprising ruthenium (Ru) and at least one of the group consisting of oxygen (O) and nitrogen (N); using out-of-plane XRD, the full width at half maximum (FWHM) of the highest intensity peak of the diffraction peak originating from the phase shifting film observed at 2θ: 20° to 50° is 1.0° or more; the etching mask film can be removed by washing with acid or alkali, wherein the layer 1 comprises Ru in the range of 40 to 99 at% and O in the range of 1 to 60 at%; or, comprises Ru in the range of 30 to 98 at% and O in the range of 1 to 69 at% and O in the range of 1 to 69 at%. The range of at% includes N.

17. A method for manufacturing a reflective photomask substrate for EUV lithography, characterized by comprising the following steps: forming a multilayer reflective film on a substrate to reflect EUV light; forming a phase shifting film on the multilayer reflective film to shift the phase of EUV light; and forming an etching mask film on the phase shifting film; wherein the phase shifting film has a layer 1, the layer 1 comprising ruthenium (Ru) and at least one of the group consisting of oxygen (O) and nitrogen (N); using out-of-plane XRD, the full width at half maximum (FWHM) of the highest intensity peak observed at 2θ: 20° to 50° from the diffraction peak originating from the phase shifting film is 1.0° or higher; the etching mask film can be removed by washing with acid or alkali; wherein the layer 1 comprises Ru in the range of 30 to 98 at% and N in the range of 2 to 70 at%.

18. A method for manufacturing a reflective photomask substrate for EUV lithography, characterized by comprising the following steps: forming a multilayer reflective film on a substrate to reflect EUV light; forming a phase shifting film on the multilayer reflective film to shift the phase of EUV light; and forming an etching mask film on the phase shifting film; wherein the phase shifting film has a layer 1, the layer 1 comprising ruthenium (Ru) and at least one selected from the group consisting of oxygen (O) and nitrogen (N); the half-width at half-maximum (FWHM) of the highest intensity peak observed at 2θ: 20° to 50° from the phase shifting film by out-of-plane XRD is 1.0° or higher; the etching mask film can be removed by washing with acid or alkali; wherein the phase shifting film further comprises a layer 2, the layer 2 comprising at least one element (X) selected from the group consisting of Cr, Ta, Ti, Re, W, Bi, Mn, Pt, Cu, Ir and V.

19. A method for manufacturing an EUV lithography reflective photomask, characterized in that: a pattern is formed by patterning a phase shift film in an EUV lithography reflective photomask substrate manufactured by the method for manufacturing an EUV lithography reflective photomask substrate as claimed in any one of claims 16 to 18.

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