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

Abstract

This reflective mask blank comprises a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and an absorption film that absorbs EUV light, in this order. The protective film contains an Ru compound, and the Ru compound contains Ru, Si, and O.

Description

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

[0001] The present disclosure relates to a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask blank, and a method for manufacturing a reflective mask.

[0002] In recent years, with the miniaturization of semiconductor devices, EUV lithography (EUVL), an exposure technology using extreme ultraviolet (EUV) light, has been developed. EUV includes soft X-rays and vacuum ultraviolet light, and specifically refers to light with a wavelength of approximately 0.2 nm to 100 nm. At present, EUV light with a wavelength of approximately 13.5 nm is mainly being considered.

[0003] In EUVL, a reflective mask is used. The reflective mask has, for example, a glass substrate, a multilayer reflective film, a protective film, and an absorbing film, in that order. The multilayer reflective film reflects EUV light. The protective film protects the multilayer reflective film from etching gas when processing the absorbing film. The absorbing film absorbs EUV light. The absorbing film may not only absorb EUV light, but also shift the phase of the EUV light. In other words, the absorbing film may be a phase shift film. In EUVL, the opening pattern of the absorbing film is transferred to a target substrate such as a semiconductor substrate. Transferring includes transferring by reducing the size.

[0004] The reflective mask blank described in Patent Document 1 has a protective film made of a Ru compound containing Ru and X (X is at least one selected from Nb and Zr). This protective film has an oxide layer mainly composed of X on the surface opposite the substrate of the protective film for the purpose of improving resistance to ozone water and etching gas (containing 70% or more of oxygen and including chlorine-based gases).

[0005] In the reflective mask blank described in Patent Document 2, the protective film is made of a Ru-based material, and the phase shift film is made of a Ta-based material. A diffusion prevention layer is formed on the surface of the protective film (the surface in contact with the phase shift film). The diffusion prevention layer contains Ru and O and prevents interdiffusion between the protective film and the phase shift film.

[0006] Japanese Patent Publication No. 2010-092947 Japanese Patent Publication No. 2015-122468

[0007] The protective film of a reflective mask blank may contain Ru. When the protective film containing Ru crystallizes, the absorbing film may inherit the crystalline structure of the protective film, causing the absorbing film to crystallize. As a result, an opening pattern is formed along the crystal grain boundaries of the absorbing film, resulting in a coarse opening pattern.

[0008] One aspect of the present disclosure provides a technique for suppressing crystallization of a protective film of a reflective mask blank when the protective film contains Ru.

[0009] A reflective mask blank according to one embodiment of the present disclosure includes, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and an absorbing film that absorbs EUV light. The protective film contains a Ru compound, and the Ru compound contains Ru, Si, and O.

[0010] According to one aspect of the present disclosure, when the protective film of the reflective mask blank contains Ru, crystallization of the protective film can be suppressed.

[0011] FIG. 1 is a cross-sectional view showing a reflective mask blank according to an embodiment. FIG. 2 is a flowchart showing a method for manufacturing a reflective mask blank according to an embodiment. FIG. 3 is a cross-sectional view showing a reflective mask according to an embodiment. FIG. 4 is a flowchart showing a method for manufacturing a reflective mask according to an embodiment. FIG. 5(A) is a cross-sectional view showing an example of step S201, FIG. 5(B) is a cross-sectional view showing an example of step S202, and FIG. 5(C) is a cross-sectional view showing an example of step S203. FIG. 6 is a cross-sectional view showing an example of EUV light reflected by the reflective mask of FIG. 3. FIG. 7 is a diagram showing a TEM image of a reflective mask blank according to Example 1 and the distribution of each element measured by TEM-EDX. FIG. 8 is a diagram showing a TEM image of a reflective mask blank according to Example 5 and the distribution of each element measured by TEM-EDX.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. The range of values ​​includes the range rounded up or down.

[0013] In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to one another. The Z-axis direction is perpendicular to the first main surface 10a of the substrate 10. The X-axis direction is perpendicular to the plane of incidence of the EUV light (the plane including the incident light beam and the reflected light beam). As shown in Figure 6, the incident light beam is tilted more in the positive Y-axis direction as it moves in the negative Z-axis direction, and the reflected light beam is tilted more in the positive Y-axis direction as it moves in the positive Z-axis direction.

[0014] A reflective mask blank 1 according to one embodiment will be described with reference to FIG. 1 . The reflective mask blank 1 includes, for example, a substrate 10, a multilayer reflective film 11, a protective film 12, an absorbing film 13, and a hard mask film 14, in this order. The multilayer reflective film 11, the protective film 12, the absorbing film 13, and the hard mask film 14 are formed on a first main surface 10a of the substrate 10 in this order. The multilayer reflective film 11 reflects EUV light. The protective film 12 protects the multilayer reflective film 11 from a first etching gas during processing of the absorbing film 13. The absorbing film 13 absorbs EUV light. The absorbing film 13 may not only absorb EUV light but also shift the phase of the EUV light. In other words, the absorbing film 13 may be a phase shift film. The hard mask film 14 protects a portion of the absorbing film 13 from the first etching gas during processing of the absorbing film 13.

[0015] The reflective mask blank 1 may have a conductive film 15 on the side opposite to the multilayer reflective film 11 with respect to the substrate 10. That is, the reflective mask blank 1 may have the conductive film 15, substrate 10, multilayer reflective film 11, protective film 12, absorbing film 13, and hard mask film 14, in this order. The conductive film 15 is formed on the second main surface 10b of the substrate 10. The second main surface 10b is the surface facing opposite to the first main surface 10a. The conductive film 15 is used, for example, to attract the reflective mask 2 to an electrostatic chuck of an exposure tool.

[0016] The reflective mask blank 1 may further have a functional film not shown in Fig. 1. For example, the reflective mask blank 1 may have a diffusion barrier film (not shown) between the multilayer reflective film 11 and the protective film 12. The diffusion barrier film suppresses diffusion of metal elements contained in the protective film 12 into the multilayer reflective film 11.

[0017] Although not shown, the reflective mask blank 1 may have a buffer film between the protective film 12 and the absorbing film 13. The buffer film protects the protective film 12 from the first etching gas that forms the opening pattern 13a in the absorbing film 13. The buffer film is etched more slowly than the absorbing film 13. Unlike the protective film 12, the buffer film will ultimately have the same opening pattern as the opening pattern 13a in the absorbing film 13.

[0018] Next, a method for manufacturing a reflective mask blank 1 according to one embodiment will be described with reference to Fig. 2. The method for manufacturing a reflective mask blank 1 includes, for example, steps S101 to S106 shown in Fig. 2. In step S101, a substrate 10 is prepared. In step S102, a conductive film 15 is formed on the second main surface 10b of the substrate 10. In step S103, a multilayer reflective film 11 is formed on the first main surface 10a of the substrate 10. In step S104, a protective film 12 is formed on the multilayer reflective film 11. In step S105, an absorbing film 13 is formed on the protective film 12. In step S106, a hard mask film 14 is formed on the absorbing film 13.

[0019] The order of steps S101 to S106 is not limited to the order shown in Fig. 2. For example, the order of step S102 and steps S103 to S106 may be reversed. Furthermore, the method for manufacturing the reflective mask blank 1 does not have to include all of steps S101 to S106. The method for manufacturing the reflective mask blank 1 may further include a step of forming a functional film not shown in Fig. 2.

[0020] Next, a reflective mask 2 according to one embodiment will be described with reference to FIG. 3. The reflective mask 2 is fabricated using, for example, the reflective mask blank 1 shown in FIG. 1 and includes an opening pattern 13a in an absorbing film 13. In EUVL, the opening pattern 13a in the absorbing film 13 is transferred to a target substrate such as a semiconductor substrate. Transferring includes reducing and transferring. Note that the hard mask film 14 shown in FIG. 1 is not included in the reflective mask 2.

[0021] Next, a method for manufacturing a reflective mask 2 according to one embodiment will be described with reference to Figures 4 and 5. The method for manufacturing a reflective mask 2 includes steps S201 to S204 shown in Figure 4. In step S201, a reflective mask blank 1 is prepared, as shown in Figure 5(A). The reflective mask blank 1 includes a resist film 16, as shown in Figure 5(A). The resist film 16 is formed on a hard mask film 14. An opening pattern to be transferred to the absorption film 13 is formed in the resist film 16.

[0022] 5B, the hard mask film 14 is processed using the resist film 16 having an opening pattern. In the openings in the resist film 16, the hard mask film 14 is exposed to a second etching gas, and the second etching gas etches the hard mask film 14. At the end of step S202, the resist film 16 remains. As a result, the opening pattern of the resist film 16 is transferred to the hard mask film 14.

[0023] The second etching gas is selected depending on the combination of the material of the resist film 16 and the material of the hard mask film 14, and is not particularly limited, but may include, for example, a fluorine-based gas. The fluorine-based gas may be, for example, CF ４ Gas, CHF ３ Gas, C ２ F ６ Gas, C ３ F ６ Gas, C ４ F ６ Gas, C ４ F ８ Gas, CH ２ F ２ Gas, CH ３ F gas, C ３ F８ Gas, F ２ Gas, SF ６ Gas and NF ３ The second etching gas may contain at least one selected from the group consisting of a fluorine-based gas, an active gas, and an inert gas. The active gas may be, for example, O ２ The inert gas includes, for example, N ２ The second etching gas preferably contains at least one selected from the group consisting of a nitrogen gas, a He gas, and an Ar gas. The second etching gas is preferably a plasma.

[0024] In step S203, as shown in FIG. 5C , the absorber film 13 is processed using the hard mask film 14 having an opening pattern. In the openings in the hard mask film 14, the absorber film 13 is exposed to a first etching gas, and the first etching gas etches the absorber film 13. The hard mask film 14 has higher resistance to the first etching gas than the absorber film 13. At the end of step S203, the hard mask film 14 remains. As a result, the opening pattern of the hard mask film 14 is transferred to the absorber film 13.

[0025] The first etching gas is selected depending on the combination of the material of the hard mask film 14 and the material of the absorption film 13, and is not particularly limited, but includes, for example, a chlorine-based gas and an oxygen-based gas. The chlorine-based gas is, for example, Cl ２ Gas, SiCl ４ Gas, CHCl ３ Gas, CCl ４ Gas and BCl ３ The oxygen-based gas includes at least one selected from the group consisting of O ２ Gas and O ３ The first etching gas may contain at least one selected from the group consisting of a chlorine-based gas, an oxygen-based gas, and an inert gas. The inert gas may be, for example, N ２ The first etching gas preferably contains at least one selected from the group consisting of a nitrogen gas, a He gas, and an Ar gas. The first etching gas is preferably a plasma.

[0026] In step S204, although not shown, the hard mask film 14 is removed. A third etching gas, for example, is used to remove the hard mask film 14. The third etching gas, like the second etching gas, contains, for example, a fluorine-based gas. The third etching gas is preferably a plasma gas. A chemical solution may be used to remove the hard mask film 14.

[0027] Next, referring back to FIG. 1, the substrate 10, the multilayer reflective film 11, the protective film 12, the absorbing film 13, the hard mask film 14, and the conductive film 15 will be described in this order.

[0028] The substrate 10 is, for example, a glass substrate. The material of the substrate 10 is TiO ２ The quartz glass has a smaller coefficient of linear expansion and a smaller change in dimension due to temperature changes than common soda lime glass. ２ 80% by mass to 95% by mass of TiO ２ It may contain 4% to 17% by mass of TiO ２ When the content is 4% by mass to 17% by mass, the linear expansion coefficient is approximately zero around room temperature, and there is almost no dimensional change around room temperature. ２ and TiO ２ The substrate 10 may contain a third component or impurities other than the above. The material of the substrate 10 may be crystallized glass in which a β-quartz solid solution is precipitated, silicon, a metal, or the like.

[0029] The substrate 10 has a first major surface 10a and a second major surface 10b facing opposite to the first major surface 10a. A multilayer reflective film 11 and the like are formed on the first major surface 10a. In plan view (viewed in the Z-axis direction), the substrate 10 measures, for example, 152 mm long and 152 mm wide. The vertical and horizontal dimensions may be 152 mm or greater. The first major surface 10a and the second major surface 10b each have, for example, a square quality assurance area at their centers. The quality assurance area measures, for example, 142 mm long and 142 mm wide. The vertical and horizontal dimensions may be 142 mm or greater. The quality assurance area on the first major surface 10a preferably has a root-mean-square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less. Furthermore, the quality assurance area on the first major surface 10a preferably does not have defects that cause phase defects.

[0030] The multilayer reflective film 11 reflects EUV light. The multilayer reflective film 11 is formed by alternately stacking, for example, high-refractive-index layers and low-refractive-index layers. The high-refractive-index layers are made of, for example, silicon (Si), and the low-refractive-index layers are made of, for example, molybdenum (Mo), so that a Mo / Si multilayer reflective film is used. Note that other films that can be used as the multilayer reflective film 11 include a Ru / Si multilayer reflective film, a Mo / Be multilayer reflective film, a Mo compound / Si compound multilayer reflective film, a Si / Mo / Ru multilayer reflective film, a Si / Mo / Ru / Mo multilayer reflective film, a Si / Ru / Mo / Ru multilayer reflective film, and a Si / Ru / Mo multilayer reflective film.

[0031] The thickness of each layer constituting the multilayer reflective film 11 and the number of repeating units of the layers can be appropriately selected depending on the material of each layer and the reflectivity for EUV light. When the multilayer reflective film 11 is a Mo / Si multilayer reflective film, in order to achieve a reflectivity of 60% or more for EUV light at an incident angle θ (see FIG. 6 ) of 6°, Mo layers with a thickness of 2.3±0.1 nm and Si layers with a thickness of 4.5±0.1 nm can be stacked so that the number of repeating units is 30 to 60. The multilayer reflective film 11 preferably has a reflectivity of 60% or more for EUV light at an incident angle θ of 6°. The reflectivity is more preferably 65% ​​or more.

[0032] The method for forming each layer constituting the multilayer reflective film 11 is, for example, DC sputtering, magnetron sputtering, or ion beam sputtering. When the Mo / Si multilayer reflective film is formed using ion beam sputtering, an example of the film formation conditions for the Mo layer and the Si layer is as follows: <Si layer formation conditions> Target: Si target, Sputtering gas: Ar gas, Gas pressure: 1.3×10 －２ Pa ~ 2.7 x 10 －２ Pa, Ion acceleration voltage: 300 V to 1500 V, Film formation rate: 0.030 nm / sec to 0.300 nm / sec, Thickness of Si layer: 4.5±0.1 nm, <Film formation conditions for Mo layer> Target: Mo target, Sputtering gas: Ar gas, Gas pressure: 1.3×10 －２ Pa ~ 2.7 x 10 －２ Pa, ion acceleration voltage: 300 V to 1500 V, film formation rate: 0.030 nm / sec to 0.300 nm / sec, film thickness of Mo layer: 2.3±0.1 nm, <Repeating units of Si layer and Mo layer> Number of repeating units: 30 to 60 (preferably 40 to 50).

[0033] The protective film 12 is formed between the multilayer reflective film 11 and the absorbing film 13 to protect the multilayer reflective film 11. The protective film 12 protects the multilayer reflective film 11 from the first etching gas when processing the absorbing film 13, i.e., in step S203. The protective film 12 is not removed even when exposed to the first etching gas, but remains on the multilayer reflective film 11.

[0034] When the protective film 12 contains Ru, it may exhibit crystallinity. If the protective film 12 crystallizes, the crystalline structure of the protective film 12 may be inherited by the absorbing film 13, causing the absorbing film 13 to crystallize. As a result, the opening pattern 13a is formed along the crystal grain boundaries of the absorbing film 13, resulting in the opening pattern 13a becoming rough.

[0035] The protective film 12 of this embodiment contains a Ru compound, and the Ru compound contains Ru, Si, and O. Si is more easily oxidized than Ru, and the O concentration in the Ru compound can be increased. O suppresses the crystallization of Ru. Therefore, the crystallization of the protective film 12 can be suppressed, and ultimately the crystallization of the absorption film 13 can be suppressed.

[0036] The Ru compound constituting the protective film 12 preferably has an average Si concentration of 9.0 at% or more. If the average Si concentration is 9.0 at% or more, the O concentration of the Ru compound is more easily increased, and crystallization of Ru is more easily suppressed. The average Si concentration is more preferably 9.5 at% or more, even more preferably 10.0 at% or more, and particularly preferably 15.0 at% or more.

[0037] The Ru compound constituting the protective film 12 preferably has an average Si concentration of less than 37.9 at%. If the average Si concentration is less than 37.9 at%, the O concentration is not too high, and the generation of defects containing SiO can be suppressed. The generation of defects containing SiO causes surface roughness of the protective film 12. The average Si concentration is more preferably 37.0 at% or less, even more preferably 35.0 at% or less, and particularly preferably 25.0 at% or less.

[0038] The Ru compound constituting the protective film 12 preferably has an average O concentration of 3.0 at% or more. If the average O concentration is 3.0 at% or more, O can easily suppress the crystallization of Ru. The average O concentration is more preferably 3.5 at% or more, and even more preferably 5.0 at% or more.

[0039] The Ru compound constituting the protective film 12 preferably has an average O concentration of less than 12.6 at%. If the average O concentration is less than 12.6 at%, the O concentration is not too high, and the generation of defects containing SiO can be suppressed. The generation of defects containing SiO causes surface roughness of the protective film 12. The average O concentration is more preferably 10.0 at% or less, and even more preferably 8.0 at% or less.

[0040] The protective film 12 includes, for example, a RuSiO film. The RuSiO film can be obtained, for example, by first forming a RuSi film and then oxidizing the RuSi film. The oxidation of the RuSi film begins from the surface of the RuSi film. Therefore, the deeper the RuSiO film is from the surface, the lower the O concentration becomes. The O concentration also depends on the element ratio of Ru to Si. Si is more easily oxidized than Ru, and the higher the Si concentration, the higher the O concentration becomes.

[0041] The RuSi film is formed, for example, by dual sputtering. The elemental ratio of Ru to Si can be adjusted by controlling the output densities of the Ru target and the Si target. The elemental ratio of Ru to Si can be made constant regardless of depth, or the elemental ratio of Ru to Si can be graded, or the Si concentration can be increased only in the outermost layer. The oxidation of the RuSi film can involve, for example, irradiating the RuSi film with oxygen plasma or implanting oxygen ions into the RuSi film.

[0042] The RuSiO film can also be formed by reactive sputtering. In this case, the element ratio of Ru to Si can be adjusted by controlling the output densities of the Ru target and the Si target. ２ Gas volume ratio (O ２ / (Ar + O ２ )) can be controlled to adjust the O concentration. The O concentration is constant, for example, regardless of the depth from the surface of the RuSiO film. Note that it is also possible to gradient the O concentration in the depth direction, or to oxidize only the outermost layer.

[0043] In this embodiment, the protective film 12 is a film consisting of a single layer, but it may also be a multi-layer film having a lower layer and an upper layer. The lower layer of the protective film 12 is a layer formed in contact with the uppermost surface of the multilayer reflective film 11. The upper layer of the protective film 12 is in contact with the lowermost surface of the absorbing film 13. By making the protective film 12 have a multi-layer structure in this way, materials with excellent predetermined functions can be used for each layer, making it possible to make the protective film 12 multifunctional as a whole.

[0044] The upper layer of the protective film 12 preferably contains at least one element selected from Ru and Rh, more preferably Rh, and even more preferably a Rh compound. The lower layer of the protective film 12 preferably contains at least one element selected from Ru, Rh, Nb, Mo, Zr, Y, and Si, more preferably Ru, and even more preferably a Ru compound. When the protective film 12 is a multilayer film, the thickness of the protective film 12 below refers to the total film thickness of the multilayer film. Note that a mixing layer formed by mixing components contained in the multilayer reflective film 11 and components contained in the lower layer of the protective film 12 may be formed between the multilayer reflective film 11 and the lower layer of the protective film 12.

[0045] The thickness of the protective film 12 is preferably 1.0 nm to 7.0 nm, more preferably 2.0 nm to 6.5 nm, and even more preferably 2.5 nm to 6.5 nm. If the thickness of the protective film 12 is 1.0 nm or more, the etching resistance is good. Furthermore, if the thickness of the protective film 12 is 7.0 nm or less, the reflectance to EUV light is good.

[0046] The density of the protective film 12 is preferably 10.0 g / cm ３ ~14.0g / cm ３ The density of the protective film 12 is 10.0 g / cm ３ If the density of the protective film 12 is 14.0 g / cm or more, the etching resistance is good. ３ If it is equal to or less than this, it is possible to suppress a decrease in reflectance for EUV light.

[0047] The upper surface of the protective film 12, i.e., the surface of the protective film 12 on which the absorbing film 13 is formed, preferably has a root-mean-square roughness Rq of 0.20 nm or less, more preferably 0.17 nm or less. If the root-mean-square roughness Rq is 0.20 nm or less, the absorbing film 13 and the like can be formed smoothly on the protective film 12. In addition, scattering of EUV light can be suppressed, and the reflectance for EUV light can be improved. The root-mean-square roughness Rq is preferably 0.05 nm or more.

[0048] The protective film 12 can be formed by, for example, DC sputtering, magnetron sputtering, or ion beam sputtering. When a RuSi film is formed by DC sputtering and then oxidized, an example of the film formation conditions is as follows: <RuSi film formation conditions> Target: Ru target and Si target, Sputtering gas: Ar gas, Gas pressure: 1.0×10 －２ Pa ~ 1.0 x 10 ０ Pa, target power density: 1.0 W / cm ２ ~8.5 W / cm ２ , Film formation rate: 0.020 nm / sec to 1.000 nm / sec, Film thickness: 1 nm to 10 nm. <RuSi film oxidation conditions (plasma treatment conditions)> O ２ Gas flow rate: 200 sccm to 3000 sccm Ar gas flow rate: 100 sccm to 6000 sccm O ２ O in the mixed gas of Ar gas and ２ Gas ratio: 0% to 90% by volume; Power supply frequency for plasma generation: 10 MHz to 60 MHz; Power for plasma generation: 50 W to 600 W; Treatment time: 2 sec to 120 sec; Treatment temperature: 80°C to 350°C; Treatment pressure: 50 Pa to 1200 Pa.

[0049] The absorbing film 13 absorbs EUV light. The absorbing film 13 is a film in which an opening pattern 13a is to be formed. The opening pattern 13a is not formed in the manufacturing process of the reflective mask blank 1, but is formed in the manufacturing process of the reflective mask 2. The absorbing film 13 may not only absorb EUV light, but also shift the phase of the EUV light. In other words, the absorbing film 13 may be a phase shift film. The phase shift film shifts the phase of the second EUV light L2 relative to the first EUV light L1 shown in FIG. 6 .

[0050] The first EUV light L1 is light that passes through the opening pattern 13a without passing through the absorbing film 13, is reflected by the multilayer reflective film 11, and passes through the opening pattern 13a without passing through the absorbing film 13 again. The second EUV light L2 is light that passes through the absorbing film 13 while being absorbed by the absorbing film 13, is reflected by the multilayer reflective film 11, and passes through the absorbing film 13 while being absorbed by the absorbing film 13 again.

[0051] The phase difference (≧0) between the first EUV light L1 and the second EUV light L2 is, for example, 170° to 250°. The phase of the first EUV light L1 may be ahead of or behind the phase of the second EUV light L2. The absorbing film 13 improves the contrast of the transferred image by utilizing interference between the first EUV light L1 and the second EUV light L2. The transferred image is an image obtained by transferring the opening pattern 13a of the absorbing film 13 onto the target substrate.

[0052] In EUVL, a so-called shadowing effect occurs. The shadowing effect refers to the occurrence of a region in the vicinity of the sidewall of the opening pattern 13 a where the sidewall blocks the EUV light due to the incident angle θ of the EUV light being not 0° (for example, 6°), resulting in a positional or dimensional deviation of the transferred image. In order to reduce the shadowing effect, it is effective to reduce the height of the sidewall of the opening pattern 13 a, and it is also effective to thin the absorbing film 13.

[0053] The thickness of the absorbing film 13 is, for example, 60 nm or less, and preferably 50 nm or less, in order to reduce the shadowing effect, and is preferably 20 nm or more, and more preferably 30 nm or more, in order to ensure a phase difference between the first EUV light L1 and the second EUV light L2.

[0054] In order to reduce the thickness of the absorbing film 13 so as to reduce the shadowing effect while ensuring the phase difference between the first EUV light L1 and the second EUV light L2, it is effective to reduce the refractive index n of the absorbing film 13. Furthermore, in order to reduce the reflectance for EUV light, it is effective to increase the extinction coefficient k of the absorbing film 13. Thus, the absorbing film 13 is required to have excellent optical properties.

[0055] The absorbing film 13 preferably contains at least one metal element selected from Cr, Ta, Nb, Ir, Pt, Pd, Au, and Ru. These metal elements have a relatively small refractive index, allowing the thickness of the absorbing film 13 to be reduced while maintaining a sufficient phase difference. The absorbing film 13 preferably contains a compound of a metal element. The compound of a metal element preferably contains at least one element selected from O, B, C, Si, and N. Adding at least one element selected from O, B, C, Si, and N can suppress crystallization while suppressing deterioration of optical properties, thereby reducing the roughness of the opening pattern 13a. The absorbing film 13 more preferably contains a Ta compound. The Ta compound more preferably contains N. This is because the inclusion of N can suppress crystallization of the Ta compound and prevent surface roughness due to crystallization. The absorbing film 13 preferably contains TaN.

[0056] In this embodiment, the absorber film 13 is a film consisting of a single layer, but it may also be a multilayer film having a lower layer and an upper layer. The lower and upper layers constituting the absorber film 13 are formed on the protective film 12 in this order. The top layer of the absorber film 13 is the layer farthest from the protective film 12. The top layer of the absorber film 13 preferably contains at least one metal element selected from Cr, Ta, Nb, Ir, Pt, Pd, Au, and Ru, and more preferably contains a compound of the metal element. The top layer of the absorber film 13 more preferably contains a Ta compound. The Ta compound is more preferably because it contains N, which suppresses the crystallization of Ta and prevents the crystals from becoming large and increasing the surface roughness. In other words, the absorber film 13 preferably contains TaN. When the absorber film 13 is a multilayer film, the thickness of the absorber film 13 refers to the total thickness of the multilayer film.

[0057] When the Ta compound contains Ta and N, the content of N atoms in the Ta compound is preferably 10.0 to 35.0 at%, more preferably 10.0 to 25.0 at%, further preferably 10.5 to 18.0 at%, and particularly preferably 11.0 to 16.0 at%, in order to increase the etching selectivity.

[0058] When the Ta compound contains N, it may further contain at least one element selected from hafnium (Hf), silicon (Si), zirconium (Zr), titanium (Ti), germanium (Ge), boron (B), tin (Sn), nickel (Ni), cobalt (Co), and hydrogen (H). The total content of these elements is preferably 10 at% or less.

[0059] The method for forming the absorbing film 13 is, for example, a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like. ２ The nitrogen content of the absorbing film 13 can be controlled by adjusting the gas content.

[0060] When a TaN film is formed by reactive sputtering, an example of the film formation conditions is as follows: <TaN film formation conditions> Target: Ta target, Output density of Ta target: 1.0 W / cm ２ ~8.5 W / cm ２ , Sputtering gas: Ar gas and N ２ Gas mixture, N in sputtering gas ２ Gas volume ratio (N ２ / (Ar+N ２ )): 0.01 to 0.25, Gas pressure: 1.0 x 10 －２ Pa ~ 1.0 x 10 ０ Pa, Ta target power density: 1.0 W / cm ２ ~8.5 W / cm ２ , Film formation rate: 0.020 nm / sec to 0.060 nm / sec, Film thickness: 20 nm to 60 nm.

[0061] The absorbing film 13 preferably has an extremely low reflectance for EUV light. Specifically, the reflectance of the absorbing film 13 for light with a wavelength of 13.5 nm is preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less, and particularly preferably 0.1% or less. The reflectance of the absorbing film 13 for light with a wavelength of 13.5 nm is 0.0% or more.

[0062] The hard mask film 14 is formed on the opposite side of the protective film 12 with respect to the absorbing film 13, and is used to form an opening pattern 13a in the absorbing film 13. The hard mask film 14 enables the resist film 16 to be made thinner.

[0063] The hard mask film 14 preferably contains at least one metal element or semi-metal element selected from Al, Hf, Y, Cr, Nb, Ti, Mo, Ta, and Si. The hard mask film 14 preferably contains a compound of the above metal element or semi-metal element. The compound preferably contains at least one element selected from O, N, C, and B.

[0064] The thickness of the hard mask film 14 is preferably 2 nm or more and 30 nm or less, more preferably 2 nm or more and 25 nm or less, and further preferably 2 nm or more and 10 nm or less.

[0065] The hard mask film 14 may be formed by, for example, DC sputtering, magnetron sputtering, or ion beam sputtering.

[0066] The conductive film 15 is formed on the opposite side of the substrate 10 from the multilayer reflective film 11, and is used to attract the reflective mask 2 to an electrostatic chuck of an exposure tool. The conductive film 15 preferably contains at least one metal element selected from Cr and Ta. The conductive film 15 preferably contains a compound of the above metal element. The compound preferably contains at least one element selected from O, N, C, and B.

[0067] In this embodiment, the conductive film 15 is a film consisting of a single layer, but it may also be a multilayer film having a lower layer and an upper layer. The lower layer and upper layer constituting the conductive film 15 are formed on the substrate 10 in this order. The uppermost layer of the conductive film 15 is the layer farthest from the substrate 10. The uppermost layer of the conductive film 15 preferably contains at least one metal element selected from Cr and Ta, and more preferably contains a compound of the above metal element. When the conductive film 15 is a multilayer film, the thickness of the conductive film 15 means the total film thickness of the multilayer film.

[0068] The thickness of the conductive film 15 is preferably 5 nm or more and 500 nm or less, more preferably 10 nm or more and 450 nm or less, and even more preferably 20 nm or more and 400 nm or less.

[0069] The conductive film 15 may be formed by, for example, DC sputtering, magnetron sputtering, or ion beam sputtering.

[0070] The experimental data will be explained below. In Examples 1 to 5, a reflective mask blank 1 was fabricated having a substrate 10, a multilayer reflective film 11, a protective film 12, and an absorbing film 13 in this order. In Examples 1 to 5, reflective mask blanks 1 were fabricated having the same configuration except for the configuration of the protective film 12. Examples 1 to 5 are working examples.

[0071] The substrate 10 is made of SiO ２ -TiO ２ A glass substrate (6-inch (152 mm) square outer diameter, 6.3 mm thick) was prepared. This glass substrate had a thermal expansion coefficient of 0.02×10 at 20° C. －７ / °C, Young's modulus is 67 GPa, Poisson's ratio is 0.17, and specific rigidity is 3.07 × 10 ７ m ２ / s ２ The quality assurance area of ​​the first main surface 10a of the substrate 10 was polished to a root-mean-square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less. A 100 nm-thick Cr film was formed on the second main surface 10b of the substrate 10 using magnetron sputtering. The sheet resistance of the Cr film was 100 Ω / □.

[0072] A Mo / Si multilayer reflective film was formed as the multilayer reflective film 11. The Mo / Si multilayer reflective film was formed by repeating the process of depositing a Si layer (film thickness 4.5 nm) and a Mo layer (film thickness 2.3 nm) 40 times using an ion beam sputtering method. The total film thickness of the Mo / Si multilayer reflective film was 272 nm ((4.5 nm + 2.3 nm) × 40). The uppermost layer of the Mo / Si multilayer reflective film was a Si layer.

[0073] As the protective film 12, a RuSiO film (film thickness 4 nm to 6 nm) having the composition shown in Table 1 was formed. The RuSiO film was formed by forming a RuSi film by a dual sputtering method and then oxidizing the RuSi film with O plasma. The element ratio of Ru to Si in the RuSiO film was adjusted by adjusting the output densities of the Ru target and the Si target, respectively. The O concentration in the RuSiO film corresponded to the Si concentration. Si is more easily oxidized than Ru, and the higher the Si concentration, the higher the O concentration.

[0074] A TaN film (40 nm) was formed as the absorption film 13. The TaN film was formed by reactive sputtering.

[0075] The experimental conditions and results of Examples 1 to 5 are shown in Table 1. The concentration of each element constituting the RuSiO film was analyzed using TEM (Transmission Electron Microscope)-EDX (Energy Dispersive X-ray Spectroscopy). The presence or absence of defects containing SiO was confirmed by observing the surface of the TaN film using an SEM (Scanning Electron Microscope). If defects containing SiO exist at the interface between the RuSiO film and the TaN film, microdefects caused by the defects containing SiO will appear on the surface of the TaN film. The amorphous nature of the TaN film, i.e., the degree of crystallization of the TaN film, was confirmed using XRD (X-ray Diffraction).

[0076]

[0077] In Table 1, the amorphousness of the TaN film being "A" indicates that the full width at half maximum of the most intense peak in the 2θ range of 20° to 50° measured by XRD using CuKα radiation was 1.0° or more, i.e., crystallization of the TaN film was suppressed. Also, in Table 1, the presence or absence of defects containing SiO being "A" indicates that no micro-defects due to defects containing SiO were observed on the surface of the TaN film using SEM, and the presence or absence of defects containing SiO being "B" indicates that micro-defects due to defects containing SiO were observed on the surface of the TaN film using SEM.

[0078] As shown in Table 1, in Examples 1 to 5, the protective film 12 was a RuSiO film, and therefore it was possible to suppress crystallization of the TaN film that was the absorber film 13. It has also been confirmed that, even when the material of the absorber film 13 is an Nb-based material or an Ir-based material, if the protective film 12 is a RuSiO film, it is possible to suppress crystallization of the absorber film 13. Furthermore, as shown in Table 1, in Examples 1 to 4, unlike Example 5, the Si concentration of the RuSiO film was less than 37.9 at %, and therefore no micro-defects due to defects containing SiO were observed on the surface of the TaN film with an SEM.

[0079] Fig. 7 shows a TEM image of the reflective mask blank according to Example 1 and the distribution of each element measured by TEM-EDX. Fig. 8 shows a TEM image of the reflective mask blank according to Example 5 and the distribution of each element measured by TEM-EDX. As shown in Fig. 8, defects containing SiO were observed at the interface between the RuSiO film and the TaN film in Example 5, but no defects containing SiO were observed at the interface between the RuSiO film and the TaN film in Example 1.

[0080] The reflective mask blank, reflective mask, reflective mask blank manufacturing method, and reflective mask manufacturing method according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure.

[0081] This application claims priority based on Japanese Patent Application No. 2023-174933 filed with the Japan Patent Office on October 10, 2023, the entire contents of which are incorporated herein by reference.

[0082] REFERENCE SIGNS LIST 1 reflective mask blank 2 reflective mask 10 substrate 11 multilayer reflective film 12 protective film 13 absorbing film

Claims

1. A reflective mask blank having, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and an absorbing film that absorbs EUV light, the protective film contains a Ru compound, and the Ru compound contains Ru, Si, and O; The Ru compound has an average Si concentration of less than 37.9 at %.

2. A reflective mask blank having, in this order: a substrate; a multilayer reflective film that reflects EUV light; a protective film that protects the multilayer reflective film; and an absorbing film that absorbs EUV light, the protective film contains a Ru compound, the Ru compound containing Ru, Si, and O; The reflective mask blank, wherein the Ru compound has an average Si concentration of 9.0 at % or more.

3. A reflective mask blank having, in this order: a substrate; a multilayer reflective film that reflects EUV light; a protective film that protects the multilayer reflective film; and an absorbing film that absorbs EUV light, the protective film contains a Ru compound, the Ru compound containing Ru, Si, and O; the absorbing film contains a Ta compound, the Ta compound contains N, A reflective mask blank, wherein the content of N atoms in the Ta compound is 10.0 at % or more and 35.0 at % or less.

4. A reflective mask blank as described in Claim 3, wherein the Ru compound has an average Si concentration of less than 37.9 at%.

5. A reflective mask blank as described in Claim 3, wherein the Ru compound has an average Si concentration of 9.0 at% or more.

6. A reflective mask blank according to claim 1 or 2, A reflective mask including an aperture pattern in the absorbing film.

7. Preparing a reflective mask blank according to claim 1 or 2; forming an opening pattern in the absorbing film; A method for manufacturing a reflective mask, comprising the steps of: