Reflection-type mask blank, reflection-type mask, method for manufacturing reflection-type mask blank, and method for manufacturing reflection-type mask

Abstract

To provide a technique phase for suppressing precipitation of Re oxide on the surface of a shift film.SOLUTION: A reflection-type mask blank has: a substrate; a multilayer reflection film which reflects EUV light; a protective film which protects the multilayer reflection film; and a phase shift film which absorbs the EUV light and shifts a phase of the EUV light, in this order. The phase shift film has a lower layer and an upper layer in this order from a side closer to the protective film. The lower layer of the phase shift film contains Re, and the upper layer of the phase shift film has smaller Re content than the lower layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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. [Background technology]

[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 about 0.2 nm to 100 nm. At present, EUV with a wavelength of about 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, and a phase shift film in this order. The multilayer reflective film reflects EUV light. The phase shift film absorbs the EUV light and shifts the phase of the EUV light. In EUVL, the opening pattern of the phase shift film is transferred to a target substrate such as a semiconductor substrate. Transferring includes reducing and transferring.

[0004] In EUVL, the so-called projection effect (shadowing effect) occurs. The shadowing effect is caused by the fact that the incident angle θ of the EUV light is not 0° (for example, 6°), and this causes an area near the side of the aperture pattern that blocks the EUV light, resulting in a positional or dimensional shift of the transferred image. In order to reduce the shadowing effect, it is effective to lower the height of the side of the aperture pattern, and to make the phase shift film thinner.

[0005] The phase shift film shifts the phase of the second EUV light relative to the first EUV light. The first EUV light is light that passes through the opening pattern of the phase shift film without being absorbed by the phase shift film, is reflected by the multilayer reflective film, and passes through the opening pattern of the phase shift film without being absorbed by the phase shift film again. The second EUV light is light that passes through the phase shift film while being absorbed by the phase shift film, is reflected by the multilayer reflective film, and passes through the phase shift film while being absorbed by the phase shift film again.

[0006] In order to reduce the thickness of the phase shift film so as to reduce the shadowing effect while maintaining the phase difference between the first EUV light and the second EUV light, it is effective to reduce the refractive index of the phase shift film. Also, in order to reduce the ratio of the reflectance of the second EUV light L2 to the reflectance of the first EUV light L1 (hereinafter also referred to as "relative reflectance"), it is effective to increase the extinction coefficient of the phase shift film. Thus, the phase shift film is required to have excellent optical properties.

[0007] The Examples section of Patent Document 1 describes compositional examples of phase shift films. A RuRe alloy is disclosed as compositional example for Examples 9 to 12. The element ratio of Re to Ru (Re:Ru) is 1:99 to 1:1. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2023 / 026868 Summary of the Invention [Problem to be solved by the invention]

[0009] Phase shift films containing Re have been considered for reflective mask blanks. Re is advantageous in that it can increase the extinction coefficient of the phase shift film. However, Re causes oxide particles to precipitate on the surface of the phase shift film.

[0010] One aspect of the present disclosure provides a technique for suppressing the precipitation of Re oxide on the surface of a phase shift film. [Means for solving the problem]

[0011] 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 a phase shift film that absorbs the EUV light and shifts the phase of the EUV light. The phase shift film includes a lower layer and an upper layer, in this order, from the side closer to the protective film. The lower layer of the phase shift film contains Re, and the upper layer of the phase shift film has a lower Re content than the lower layer. Effect of the Invention

[0012] According to one embodiment of the present disclosure, it is possible to suppress the precipitation of Re oxide on the surface of the phase shift film. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a reflective mask blank according to one embodiment. [Diagram 2] FIG. 2 is a flowchart showing a method for manufacturing a reflective mask blank according to one embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing a reflective mask according to an embodiment. [Figure 4] FIG. 4 is a flowchart showing a method for manufacturing a reflective mask according to an embodiment. [Diagram 5] FIG. 5(A) is a cross-sectional view showing an example of S201, FIG. 5(B) is a cross-sectional view showing an example of S202, and FIG. 5(C) is a cross-sectional view showing an example of S203. [Figure 6] FIG. 6 is a cross-sectional view showing an example of EUV light reflected by the reflective mask of FIG. [Figure 7] FIG. 7 is a diagram showing an example of the refractive index and extinction coefficient of each element. [Figure 8] FIG. 8 is a cross-sectional view showing a reflective mask according to a modified example. [Figure 9] FIG. 9(A) is a diagram showing an image of the surface of the phase shift film obtained in Example 3, and FIG. 9(B) is a diagram showing an image of the surface of the phase shift film obtained in Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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 the description may be omitted. In the specification, the symbol "~" indicating a range of values ​​means that the values ​​before and after the symbol are included as the lower and upper limits.

[0015] In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The Z-axis direction is perpendicular to the first main surface 10a of the substrate 10. The X-axis direction is perpendicular to the incidence plane of the EUV light (plane including the incident light beam and the reflected light beam). As shown in FIG. 6, the incident light beam is inclined toward the positive Y-axis direction as it moves toward the negative Z-axis direction, and the reflected light beam is inclined toward the positive Y-axis direction as it moves toward the positive Z-axis direction.

[0016] 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, a phase shift film 13, and a hard mask film 14, in this order. The multilayer reflective film 11, the protective film 12, the phase shift 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 when the phase shift film 13 is processed. The phase shift film 13 absorbs EUV light and shifts the phase of the EUV light. The hard mask film 14 protects a part of the phase shift film 13 from a first etching gas when the phase shift film 13 is processed.

[0017] The reflective mask blank 1 may have a conductive film 15 on the opposite side 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, the substrate 10, the multilayer reflective film 11, the protective film 12, the phase shift film 13, and the 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 device.

[0018] 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.

[0019] Although not shown, the reflective mask blank 1 may have a buffer film between the protective film 12 and the phase shift film 13. The buffer film protects the protective film 12 from a first etching gas that forms an opening pattern 13op in the phase shift film 13. The buffer film is etched more slowly than the phase shift film 13. Unlike the protective film 12, the buffer film will ultimately have the same opening pattern as the opening pattern 13op of the phase shift film 13.

[0020] 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 the 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, a phase shift film 13 is formed on the protective film 12. In step S106, a hard mask film 14 is formed on the phase shift film 13.

[0021] 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.

[0022] Next, a reflective mask 2 according to an embodiment will be described with reference to Fig. 3. The reflective mask 2 includes, for example, the reflective mask blank 1 shown in Fig. 1 and includes an opening pattern 13op in a phase shift film 13. In EUVL, the opening pattern 13op in the phase shift 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.

[0023] Next, a method for manufacturing a reflective mask 2 according to one embodiment will be described with reference to Fig. 4 and Fig. 5. The method for manufacturing a reflective mask 2 includes steps S201 to S204 shown in Fig. 4. In step S201, a reflective mask blank 1 is prepared as shown in Fig. 5(A). The reflective mask blank 1 includes a resist film 16 as shown in Fig. 5(A). The resist film 16 is formed on a hard mask film 14. An opening pattern to be transferred to the phase shift film 13 is formed in the resist film 16.

[0024] In step S202, as shown in FIG. 5B, the hard mask film 14 is processed using the resist film 16 having an opening pattern. In the openings of 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.

[0025] 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 F 8 Gas, F 2 Gas, SF 6 Gas and NF 3 The second etching gas may include at least one selected from the group consisting of fluorine-based gas, active gas, and inert gas. The active gas may be, for example, O 2 Gas and O 3 The inert gas includes at least one selected from the group consisting of 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.

[0026] In step S203, as shown in FIG. 5C, the phase shift film 13 is processed using the hard mask film 14 having an opening pattern. In the openings of the hard mask film 14, the phase shift film 13 is exposed to a first etching gas, and the first etching gas etches the phase shift film 13. The hard mask film 14 has higher resistance to the first etching gas than the phase shift 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 phase shift film 13.

[0027] The first etching gas is selected according to the combination of the material of the hard mask film 14 and the material of the phase shift 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 2Gas, 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 include at least one selected from the group consisting of a chlorine-based gas and 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.

[0028] In step S204, although not shown, the hard mask film 14 is removed. For example, a third etching gas is used to remove the hard mask film 14. The third etching gas contains, for example, a fluorine-based gas, similar to the second etching gas. The third etching gas is preferably a plasma gas. For example, a chemical solution may be used to remove the hard mask film 14.

[0029] Next, referring back to FIG. 1, the substrate 10, the multilayer reflective film 11, the protective film 12, the phase shift film 13, the hard mask film 14, and the conductive film 15 will be described in this order.

[0030] The substrate 10 is, for example, a glass substrate. The material of the substrate 10 is TiO 2 Quartz glass containing SiO is preferred. Quartz glass has a smaller linear expansion coefficient and smaller dimensional change due to temperature change than general soda-lime glass. 2 80% to 95% by mass, TiO 2 It may contain 4% by mass to 17% by mass of TiO 2 When the content is 4% by mass to 17% by mass, the linear expansion coefficient at room temperature is approximately zero, and almost no dimensional change occurs at room temperature. 2 and TiO 2The material of the substrate 10 may be crystallized glass in which a β-quartz solid solution is precipitated, silicon, a metal, or the like.

[0031] The substrate 10 has a first main surface 10a and a second main surface 10b facing opposite to the first main surface 10a. A multilayer reflective film 11 and the like are formed on the first main surface 10a. The size of the substrate 10 in plan view (viewed in the Z-axis direction) is, for example, 152 mm long and 152 mm wide. The vertical and horizontal dimensions may be 152 mm or more. The first main surface 10a and the second main surface 10b each have, for example, a square quality assurance area in the center. The size of the quality assurance area is, for example, 142 mm long and 142 mm wide. The vertical and horizontal dimensions may be 142 mm or more. The quality assurance area of ​​the first main surface 10a preferably has a root-mean-square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less. In addition, it is preferable that the quality assurance area of ​​the first main surface 10a does not have a defect that causes a phase defect.

[0032] The multilayer reflective film 11 reflects EUV light. The multilayer reflective film 11 is, for example, a laminate of high refractive index layers and low refractive index layers alternately. 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), and a Mo / Si multilayer reflective film is used. Note that Ru / Si multilayer reflective film, Mo / Be multilayer reflective film, Mo compound / Si compound multilayer reflective film, Si / Mo / Ru multilayer reflective film, Si / Mo / Ru / Mo multilayer reflective film, Si / Ru / Mo / Ru multilayer reflective film, Si / Ru / Mo multilayer reflective film, and the like can also be used as the multilayer reflective film 11.

[0033] The film thickness of each layer constituting the multilayer reflective film 11 and the number of repeating units of the layer can be appropriately selected according to the material of each layer and the reflectivity with respect to 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 with respect to EUV light with an incident angle θ (see Fig. 6) of 6°, a Mo layer with a film thickness of 2.3 ± 0.1 nm and a Si layer with a film thickness of 4.5 ± 0.1 nm may be laminated so that the number of repeating units is 30 or more and 60 or less. The multilayer reflective film 11 preferably has a reflectivity of 60% or more with respect to EUV light with an incident angle θ of 6°. More preferably, the reflectivity is 65% or more.

[0034] The film formation method of each layer constituting the multilayer reflective film 11 is, for example, a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like. When forming a Mo / Si multilayer reflective film using the ion beam sputtering method, an example of the film formation conditions for each of the Mo layer and the Si layer is as follows. <Film formation conditions for Si layer> Target: Si target, Sputtering gas: Ar gas, Gas pressure: 1.3×10 -2 Pa~2.7×10 -2 Pa, Ion acceleration voltage: 300V~1500V, Film formation rate: 0.030 nm / sec~0.300 nm / sec, Film 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~2.7×10 -2 Pa, Ion acceleration voltage: 300V~1500V, Film formation rate: 0.030 nm / sec~0.300 nm / sec, Film thickness of Mo layer: 2.3 ± 0.1 nm, <Repeating unit of Si layer and Mo layer> Number of repeating units: 30~60 (preferably 40~50).

[0035] The protective film 12 is formed between the multilayer reflective film 11 and the phase shift 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 phase shift 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.

[0036] The protective film 12 contains at least one element selected from, for example, Ru, Rh, and Si. When the protective film 12 contains Rh, the protective film 12 may contain only Rh, or may contain an Rh compound. The Rh compound may contain, in addition to Rh, at least one element selected from the group consisting of Ru, Nb, Mo, Ta, Ir, Pd, Zr, Y, and Ti.

[0037] The Rh compound may contain, in addition to Rh, at least one element selected from the group consisting of N, O, C, and B. These elements reduce the resistance of the protective film 12 to the first etching gas, but reduce the crystallinity of the protective film 12, thereby improving the smoothness of the protective film 12. When the Rh compound has an amorphous structure or a microcrystalline structure, the X-ray diffraction profile of the Rh compound does not have a clear peak.

[0038] In this embodiment, the protective film 12 is a film consisting of a single layer, but it may 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 phase shift film 13. By forming the protective film 12 in this manner as a multi-layer structure, materials having excellent predetermined functions can be used for each layer, and therefore the protective film 12 as a whole can be made multifunctional.

[0039] The upper layer of the protective film 12 preferably contains at least one element selected from Ru and Rh, more preferably contains Rh, and even more preferably contains an 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, and more preferably contains Ru. Further, in order to suppress the crystallinity of the protective film 12, the lower layer of the protective film 12 preferably contains at least one element selected from C, N, and B in addition to the above at least one element. When the protective film 12 is a multilayer film, the thickness of the protective film 12 below means the total film thickness of the multilayer film. Note that a mixing layer formed by mixing the components contained in the multilayer reflective film 11 and the 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.

[0040] The thickness of the protective film 12 is preferably 1.0 nm to 4.0 nm, more preferably 2.0 nm to 3.5 nm, and even more preferably 2.5 nm to 3.0 nm. If the thickness of the protective film 12 is 1.0 nm or more, the etching resistance is good. Also, if the thickness of the protective film 12 is 4.0 nm or less, the reflectance for EUV light is good.

[0041] The density of the protective film 12 is preferably 10.0 g / cm 3 ~14.0 g / cm 3 . If the density of the protective film 12 is 10.0 g / cm 3 or more, the etching resistance is good. Also, if the density of the protective film 12 is 14.0 g / cm 3 or less, a decrease in the reflectance for EUV light can be suppressed.

[0042] The film formation method of the protective film 12 is, for example, a DC sputtering method, a magnetron sputtering method, an ion beam sputtering method, or the like. When forming an Rh film using the DC sputtering method, an example of the film formation conditions is as follows. <Film formation conditions of Rh film> Target: Rh target, Sputtering gas: Ar gas, Gas pressure: 1.0×10-2 Pa~1.0×10 0 Pa, Target power density: 1.0W / cm 2 ~8.5W / cm 2 , Deposition rate: 0.020nm / sec~1.000nm / sec, Film thickness: 1nm~10nm.

[0043] The phase shift film 13 absorbs EUV light and shifts the phase of the EUV light. The phase shift film 13 is a film in which an opening pattern 13op is to be formed. The opening pattern 13op 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 phase shift film shifts the phase of the second EUV light L2 with respect to the first EUV light L1 shown in FIG.

[0044] The first EUV light L1 is light that passes through the opening pattern 13op of the phase shift film 13 without being absorbed by the phase shift film 13, is reflected by the multilayer reflective film 11, and passes through the opening pattern 13op of the phase shift film 13 without being absorbed by the phase shift film 13 again. The second EUV light L2 is light that passes through the phase shift film 13 while being absorbed by the phase shift film 13, is reflected by the multilayer reflective film 11, and passes through the phase shift film 13 while being absorbed by the phase shift film 13 again.

[0045] 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 phase shift film 13 improves the contrast of the transferred image by utilizing the 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 13op of the phase shift film 13 onto the target substrate.

[0046] In EUVL, a so-called projection effect (shadowing effect) occurs. The shadowing effect refers to a region in which the side surface of the opening pattern 13op 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 shift of the transferred image. In order to reduce the shadowing effect, it is effective to lower the height of the side surface of the opening pattern 13op, and it is also effective to thin the phase shift film 13.

[0047] The thickness of the phase shift film 13 is, for example, 60 nm or less, and preferably 50 nm or less, in order to reduce the shadowing effect. The thickness of the phase shift film 13 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.

[0048] In order to reduce the thickness of the phase shift 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 phase shift film 13. Also, in order to reduce the ratio of the reflectance of the second EUV light L2 to the reflectance of the first EUV light L1 (hereinafter also referred to as "relative reflectance"), it is effective to increase the extinction coefficient k of the phase shift film 13. Thus, the phase shift film 13 is required to have excellent optical properties.

[0049] Fig. 7 is a diagram showing an example of the refractive index n and extinction coefficient k of each element. In this specification, the refractive index n is the refractive index for EUV light (e.g., light with a wavelength of 13.5 nm). Also, in this specification, the extinction coefficient k is the extinction coefficient for EUV light (e.g., light with a wavelength of 13.5 nm). Note that Fig. 7 also shows the refractive index n and extinction coefficient k of the lower layer listed in Tables 1 and 2 described below.

[0050] 7, Re is advantageous in that it can increase the extinction coefficient of the phase shift film 13. However, Re causes oxide particles to precipitate on the surface of the phase shift film 13. Re also reduces the resistance of the phase shift film 13 to SPM (a mixture of sulfuric acid and hydrogen peroxide). SPM is used to remove the resist film 16, clean the reflective mask 2, and the like.

[0051] 1, the phase shift film 13 of this embodiment has a lower layer 13A and an upper layer 13B in this order from the side closer to the protective film 12. The lower layer 13A of the phase shift film 13 contains Re. The upper layer 13B of the phase shift film 13 has a lower Re content than the lower layer 13A. It is preferable that the upper layer 13B does not substantially contain Re.

[0052] According to this embodiment, a lower layer 13A containing Re is combined with an upper layer 13B having a lower Re content than the lower layer 13A. This makes it possible to utilize the optical properties of Re while suppressing the precipitation of Re oxides on the surface (upper surface in FIG. 1) of the phase shift film 13. In addition, the resistance of the phase shift film 13 to SPM can be improved.

[0053] The upper layer 13B preferably contains at least one metal element selected from Ru, Ir, Pt, and Ta. Ru, Ir, Pt, and Ta are superior in resistance to SPM compared to Re. From the viewpoint of resistance to SPM, it is preferable that the upper layer 13B does not substantially contain Re.

[0054] More preferably, the upper layer 13B has a compound containing at least one metal element selected from Ru, Ir, Pt, and Ta. The compound preferably contains at least one nonmetal element selected from B, C, N, and Si. These nonmetal elements can reduce the crystallinity of the upper layer 13B and reduce the roughness of the side surface of the opening pattern 13op. It is preferable that the upper layer 13B does not substantially contain O from the viewpoint of suppressing the precipitation of Re oxides.

[0055] The thickness of the upper layer 13B is preferably 0.1 nm to 10 nm, more preferably 0.1 nm to 4 nm, and further preferably 0.1 nm to 2 nm. If the thickness of the upper layer 13B is 0.1 nm or more, the precipitation of Re oxides can be suppressed and the resistance to SPM can be improved.

[0056] Furthermore, if the thickness of the upper layer 13B is 10 nm or less, the upper layer 13B has little effect on the optical constants of the phase shift film 13. The optical constants of the phase shift film 13 are substantially determined by the optical constants of the lower layer 13A. Since the lower layer 13A contains Re, the extinction coefficient k of the phase shift film 13 can be increased.

[0057] The lower layer 13A preferably contains a Re compound. The Re compound preferably contains at least one metal element selected from Ru, Ir, Pt, and Cr in addition to Re. Ru, Ir, Pt, and Cr have better resistance to SPM than Re. Therefore, the resistance of the lower layer 13A to SPM can be improved.

[0058] When the Re compound contains at least one metal element selected from Ru, Ir, Pt, and Cr in addition to Re, from the viewpoint of resistance to SPM, the ratio (Re / M) of the Re content to the total content of all metal elements (e.g., Re, Ru, Ir, Pt, and Cr) is preferably 60 atomic % or less. The ratio (Re / M) is more preferably 50 atomic % or less, even more preferably 40 atomic % or less, and particularly preferably 35 atomic % or less.

[0059] When the Re compound contains, in addition to Re, at least one metal element selected from Ru, Ir, Pt, and Cr, from the viewpoint of optical constants, the ratio of the Re content to the total content of all metal elements (Re / M) is preferably 10 atomic % or more, and more preferably 15 atomic % or more.

[0060] The lower layer 13A and the upper layer 13B preferably contain the same metal element. The same metal element is at least one selected from Ru, Ir, and Pt. By using the same metal element, the resistance to SPM of both the lower layer 13A and the upper layer 13B can be improved. In addition, since the same metal element is used, the lower layer 13A and the upper layer 13B can be continuously formed using the same film forming apparatus.

[0061] The lower layer 13A preferably contains a Re compound. The Re compound preferably contains at least one nonmetallic element selected from B, C, N and Si in addition to Re. These nonmetallic elements can reduce the crystallinity of the lower layer 13A and reduce the roughness of the side surface of the opening pattern 13op. From the viewpoint of suppressing the precipitation of Re oxides, the lower layer 13A preferably does not substantially contain O.

[0062] When the Re compound contains, in addition to Re, at least one nonmetallic element selected from B, C, N, and Si, it is preferable that the total content of B, C, N, and Si is 30 atomic % or less relative to the total content of all elements.

[0063] The refractive index n of the lower layer 13A is preferably 0.920 or less, more preferably 0.915 or less, and further preferably 0.910 or less. The smaller the refractive index n of the lower layer 13A, the smaller the film thickness of the phase shift film 13 can be to reduce the shadowing effect while ensuring the phase difference between the first EUV light L1 and the second EUV light L2. However, the refractive index n of the lower layer 13A may be 0.890 or more.

[0064] The extinction coefficient k of the lower layer 13A is preferably 0.020 or more, more preferably 0.022 or more, and even more preferably 0.024 or more. The larger the extinction coefficient k of the lower layer 13A, the smaller the ratio (relative reflectance) of the reflectance of the second EUV light L2 to the reflectance of the first EUV light L1 can be. However, the extinction coefficient k of the lower layer 13A may be 0.060 or less.

[0065] The optical properties (refractive index n and extinction coefficient k) of the lower layer 13A are determined using the values from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or values calculated from the "dependence on the incident angle" of the reflectance described below. Note that the optical properties of the upper layer 13B can also be determined in the same manner as those of the lower layer 13A.

[0066] The incident angle θ of EUV light, the reflectance R with respect to EUV light, the refractive index n of the lower layer 13A, and the extinction coefficient k of the lower layer 13A satisfy the following formula (1). R = |(sinθ - ((n + ik) 2 - cos 2 θ) 1 / 2 ) / (sinθ + ((n + ik) 2 - cos 2 θ) 1 / 2 )| ··· (1) Measure a plurality of combinations of the incident angle θ and the reflectance R, and calculate the refractive index n and the extinction coefficient k by the least squares method so that the error between the plurality of measurement data and the formula (1) is minimized.

[0067] The method for forming the phase shift film 13 is, for example, a DC sputtering method, a magnetron sputtering method, or an ion beam sputtering method. When forming the RuReC film as the lower layer 13A and the Ru film as the upper layer 13B in this order using the magnetron sputtering method, an example of the film formation conditions is as follows. <Film formation conditions for RuReC film> Targets: Ru target, Re target, C target Sputtering gas: Ar gas, Gas pressure: 1.0 × 10 -2 Pa ~ 1.0 × 10 0 Pa, Output density of Ru target: 1.0 W / cm 2 ~ 8.5 W / cm 2 , Output density of Re target: 1.0 W / cm 2 ~ 8.5 W / cm 2 , Output density of C target: 1.0 W / cm2 ~8.5 W / cm 2 、 Thickness of the RuReC film: 20 nm to 60 nm. <Film formation conditions of the Ru film> Target: Ru target Sputtering gas: Ar gas, Gas pressure: 1.0×10 -2 Pa to 1.0×10 0 Pa, Output density of the Ru target: 1.0 W / cm 2 ~8.5 W / cm 2 、 Thickness of the Ru film: 0.1 nm to 10 nm.

[0068] The hard mask film 14 is formed on the side opposite to the protective film 12 with respect to the phase shift film 13 and is used to form the opening pattern 13op in the phase shift film 13. The hard mask film 14 enables thinning of the resist film 16.

[0069] The hard mask film 14 preferably contains at least one metal element or metalloid 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 metalloid element. The compound preferably contains at least one element selected from O, N, C, and B.

[0070] 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 even more preferably 2 nm or more and 10 nm or less.

[0071] The film formation method of the hard mask film 14 is, for example, a DC sputtering method, a magnetron sputtering method, or an ion beam sputtering method.

[0072] 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.

[0073] In this embodiment, the conductive film 15 is a film consisting of a single layer, but it may 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.

[0074] 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 further preferably 20 nm or more and 400 nm or less.

[0075] The conductive film 15 is formed by, for example, DC sputtering, magnetron sputtering, or ion beam sputtering.

[0076] Next, a reflective mask 2 according to a modified example will be described with reference to FIG. 8. Differences from the above embodiment will be mainly described below. The opening pattern 13op of the phase shift film 13 is formed penetrating the upper layer 13B and the lower layer 13A, as in the above embodiment. Unlike the above embodiment, the phase shift film 13 has a modified layer 13C having a lower Re content than the lower layer 13A on the side of the opening pattern 13op in the lower layer 13A. By forming the modified layer 13C, it is possible to suppress the precipitation of Re oxide on the side of the opening pattern 13op. In addition, it is possible to improve the resistance of the side of the opening pattern 13op to SPM.

[0077] The modified layer 13C is formed during the manufacturing process of the reflective mask 2. Specifically, the modified layer 13C is obtained by forming an opening pattern 13op in the phase shift film 13, and then exposing the side surface of the opening pattern 13op to a mixed gas containing a fluorine-based gas and an oxygen-based gas (hereinafter, also referred to as a "fourth etching gas"). The fourth etching gas causes Re contained in the lower layer 13A to be desorbed. As a result, it is possible to form the modified layer 13C which has a lower Re content and a higher content of metal elements other than Re (e.g., Ru) than the lower layer 13A.

[0078] The fourth etching gas is a mixed gas of a fluorine-based gas and an oxygen-based gas. The fluorine-based gas is, 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 F 8 Gas, F 2 Gas, SF 6 Gas and NF 3 The fluorine-based gas is preferably CF 4 Gas and SF 6 The oxygen-based gas includes at least one selected from the group consisting of O 2 Gas and O 3 The fourth etching gas includes at least one selected from the group consisting of a fluorine-based gas, an oxygen-based gas, and a fluorine-based gas. The fourth etching gas is preferably a plasma. The volume ratio of the fluorine-based gas to the oxygen-based gas (fluorine-based gas:oxygen-based gas) in the fourth etching gas is preferably 10:90 to 90:10, and more preferably 40:60 to 60:40.

[0079] The modified layer 13C has a smaller Re content than the lower layer 13A. Therefore, it is also possible to form the upper layer 13B using the technique of this modification. Specifically, in the manufacturing process of the reflective mask blank 1, after the lower layer 13A is formed, the upper surface of the lower layer 13A is exposed to a fourth etching gas to form the upper layer 13B. The upper layer 13B may be a modified layer. The upper layer 13B is formed before the hard mask film 14 is formed. EXAMPLES

[0080] The experimental data will be described below. In Examples 1 to 11, a reflective mask blank 1 having a substrate 10, a multilayer reflective film 11, a protective film 12, and a phase shift film 13 in this order was prepared. In Examples 1 to 11, a reflective mask blank 1 having the same configuration except for the configuration of the phase shift film 13 was prepared. Examples 1, 3, 5 to 8, and 10 are working examples, and Examples 2, 4, 9, and 11 are comparative examples.

[0081] The substrate 10 is made of SiO 2 -TiO 2 A glass substrate (6-inch (152 mm) square, 6.3 mm thick) was prepared. The thermal expansion coefficient of this glass substrate at 20° C. was 0.02×10 -7 / °C, Young's modulus is 67 GPa, Poisson's ratio is 0.17, and specific stiffness is 3.07 × 10 7 m 2 / s 2 It was.

[0082] 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 deposition of a Si layer (thickness 4.5 nm) and a Mo layer (thickness 2.3 nm) 40 times using an ion beam sputtering method. The total thickness of the Mo / Si multilayer reflective film was 272 nm ((4.5 nm + 2.3 nm) × 40).

[0083] A Rh film (thickness: 5 nm) was formed as the protective film 12. The Rh film was formed by using an ion beam sputtering method.

[0084] The phase shift film 13 was formed to have a single-layer structure or a multi-layer structure as shown in Table 1. The phase shift film 13 was formed by magnetron sputtering. The ratio of metal elements in the chemical composition of each layer constituting the phase shift film 13 was measured by a Rutherford backscattering spectrometry (RBS) device. The C content was measured by a calibration curve method using a fluorescent X-ray analyzer ZSX Primus II manufactured by Rigaku Corporation, using a sample containing 30 atomic % or more of C as a standard sample measured by RBS. The thickness of each layer constituting the phase shift film 13 was measured by X-ray reflectivity.

[0085] In Examples 1 to 11, after the reflective mask blank 1 was produced, the presence or absence of Re oxide precipitation on the surface of the phase shift film 13 was examined using a scanning electron microscope SU-70 manufactured by Hitachi High-Technologies Corporation. In Examples 1 to 11, after the reflective mask blank 1 was produced, the surface of the phase shift film 13 was etched with an SPM at 100° C. for 20 minutes, and the change in film thickness was examined. The experimental results of Examples 1 to 11 are shown in Table 1.

[0086] [Table 1]

[0087] As shown in Table 1, in Examples 1, 3, 5 to 8, and 10, phase shift film 13 had a multi-layer structure, unlike Examples 2, 4, 9, and 11. As a result, in Examples 1, 3, 5 to 8, and 10, unlike Examples 2, 4, 9, and 11, the generation of precipitates (Re oxides) could be suppressed.

[0088] Fig. 9(A) shows an image of the surface of the phase shift film 13 obtained in Example 3. Fig. 9(B) shows an image of the surface of the phase shift film 13 obtained in Example 4. Precipitates P were observed in Example 4 as shown in Fig. 9(B), whereas precipitates P were not observed in Example 3 as shown in Fig. 9(A).

[0089] In Examples 12 to 13, a reflective mask blank 1 having a substrate 10, a multilayer reflective film 11, a protective film 12, and a phase shift film 13 in this order was prepared, similarly to Examples 1 to 11. In Examples 12 to 13, a reflective mask blank 1 having the same configuration as that of the phase shift film 13 was prepared. Examples 12 to 13 are reference examples. In Examples 12 to 13, a phase shift film 13 having a single-layer structure shown in Table 2 (having only the lower layer shown in Table 2) was formed.

[0090] In Examples 12 and 13, after producing the reflective mask blank 1, the surface of the phase shift film 13 was exposed to the etching gas shown in Table 2 for 10 seconds at room temperature, and then the surface of the phase shift film 13 was etched with an SPM for 20 minutes at 100° C., and the change in film thickness was examined. The experimental results of Examples 12 and 13 are shown in Table 2.

[0091] [Table 2]

[0092] As shown in Table 2, in Example 12, the surface of the phase shift film 13 was treated with CF 4 Gas and O 2 Gas mixture containing CF 4 Content: 50% by volume, O 2 The phase shift film 13 was exposed to a Cl content of 50% by volume, and the change in film thickness was small even when etched with the SPM. 2 Gas and O 2 Mixture of gases including Cl 2 Content: 50% by volume, O 2 The film was exposed to a concentration of 50% by volume, and the change in film thickness was large when etched with an SPM.

[0093] From this, according to Example 12, the surface of the phase shift film 13 is 4 Gas and O 2 It can be seen that a modified layer was formed on the surface of the phase shift film 13 by exposing it to a mixed gas containing Re. The modified layer has a lower Re content than the lower layer. Therefore, the modified layer formed in Example 12 can also be used as an upper layer.

[0094] The reflective mask blank, the reflective mask, the manufacturing method of the reflective mask blank, and the manufacturing method of the reflective mask according to the present disclosure have been described above, but the present disclosure is not limited to the above-mentioned 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. [Explanation of symbols]

[0095] 1 Reflective mask blank 2 Reflective mask 10 Substrate 11 Multilayer reflective film 12 Protective film 13 Phase shift film 13A Lower layer 13B Upper layer

Claims

1. A reflective mask blank comprising, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film that protects the multilayer reflective film, and a phase shift film that absorbs the EUV light and shifts the phase of the EUV light, the phase shift film has a lower layer and an upper layer in this order from the side closest to the protective film, A reflective mask blank, wherein the lower layer of the phase shift film contains Re, and the upper layer of the phase shift film has a lower Re content than the lower layer.

2. 2. The reflective mask blank according to claim 1, wherein the upper layer of the phase shift film contains at least one metal element selected from the group consisting of Ru, Ir, Pt and Ta.

3. the upper layer of the phase shift film has a compound containing at least one metal element selected from Ru, Ir, Pt, and Ta; The reflective mask blank according to claim 1 , wherein the compound contains at least one nonmetallic element selected from B, C, N and Si.

4. 4. The reflective mask blank according to claim 1, wherein the upper layer of the phase shift film has a thickness of 0.1 nm or more and 10 nm or less.

5. 4. The reflective mask blank according to claim 1, wherein the upper layer of the phase shift film has a thickness of 0.1 nm or more and 4 nm or less.

6. The reflective mask blank according to any one of claims 1 to 3, wherein the lower layer of the phase shift film contains an Re compound, and the Re compound contains, in addition to Re, at least one metal element selected from Ru, Ir, Pt, and Cr.

7. The reflective mask blank according to claim 6 , wherein the Re compound has an Re content of 60 atomic % or less with respect to the total content of all metal elements.

8. the lower layer of the phase shift film and the upper layer of the phase shift film contain the same metal element, The reflective mask blank according to claim 6 , wherein the same metal element is at least one selected from the group consisting of Ru, Ir and Pt.

9. The reflective mask blank according to any one of claims 1 to 3, wherein the lower layer of the phase shift film contains a Re compound, and the Re compound contains, in addition to Re, at least one nonmetallic element selected from B, C, N, and Si.

10. 10. The reflective mask blank according to claim 9, wherein the Re compound has a total content of B, C, N and Si of 30 atomic % or less with respect to the total content of all elements.

11. 4. The reflective mask blank according to claim 1, wherein the lower layer of the phase shift film has a refractive index of 0.920 or less.

12. 4. The reflective mask blank according to claim 1, wherein the lower layer of the phase shift film has an extinction coefficient of 0.020 or more.

13. 4. The reflective mask blank according to claim 1, wherein the phase shift film has a thickness of 60 nm or less.

14. 4. The reflective mask blank according to claim 1, further comprising a hard mask film on the opposite side of said protective film with respect to said phase shift film.

15. 15. The reflective mask blank according to claim 14, wherein the hard mask film contains at least one element selected from Al, Hf, Y, Cr, Nb, Ti, Mo, Ta and Si.

16. the hard mask film has a compound containing at least one element selected from Al, Hf, Y, Cr, Nb, Ti, Mo, Ta, and Si; The reflective mask blank according to claim 14 , wherein the compound contains at least one nonmetallic element selected from B, C, N and O.

17. The reflective mask blank according to claim 14 , wherein the hard mask film has a thickness of 20 nm or less.

18. A reflective mask blank according to any one of claims 1 to 3, A reflective mask including an opening pattern in the phase shift film.

19. the opening pattern is formed penetrating the upper layer and the lower layer, 20. The reflective mask according to claim 18, wherein the phase shift film has a modified layer on a side surface of the opening pattern of the lower layer, the modified layer having a lower Re content than the lower layer.

20. A method for producing 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 a phase shift film that absorbs the EUV light and shifts a phase of the EUV light, comprising: the phase shift film has a lower layer and an upper layer in this order from the side closest to the protective film, A method for producing a reflective mask blank, wherein the lower layer of the phase shift film contains Re, and the upper layer of the phase shift film has a lower Re content than the lower layer.

21. Preparing a reflective mask blank according to any one of claims 1 to 3; forming an opening pattern in the phase shift film; having The method for manufacturing a reflective mask, wherein the opening pattern is formed penetrating the upper layer and the lower layer.

22. 22. The method for producing a reflective mask according to claim 21, further comprising exposing a side surface of the opening pattern to a mixed gas containing a fluorine-based gas and an oxygen-based gas after forming the opening pattern in the phase shift film.

23. 23. The method for producing a reflective mask according to claim 22, wherein the mixed gas has a volume ratio of the fluorine-based gas to the oxygen-based gas (fluorine-based gas:oxygen-based gas) of 10:90 to 90:

10.

24. 23. The method for producing a reflective mask according to claim 22, wherein the mixed gas has a volume ratio of the fluorine-based gas to the oxygen-based gas (fluorine-based gas:oxygen-based gas) of 40:60 to 60:

40.

25. The fluorine-based gas is 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 F ８ Gas, F. ２ Gas, SF ６ Gas and NF ３ 23. The method for producing a reflective mask according to claim 22, further comprising at least one selected from the group consisting of a gas.

26. The fluorine-based gas is CF ４ Gas and SF ６ 23. The method for producing a reflective mask according to claim 22, further comprising at least one selected from the group consisting of a gas.

27. The oxygen-based gas is O ２ Gas and O ３ 23. The method for producing a reflective mask according to claim 22, further comprising at least one selected from the group consisting of a gas.

28. 22. The method for producing a reflective mask according to claim 21, further comprising forming an opening pattern in the phase shift film by using a chlorine-based gas and an oxygen-based gas.

29. The chlorine-based gas is Cl ２ Gas, SiCl ４ Gas, CHCl ３ Gas, CCl ４ Gas and BCl ３ 30. The method for producing a reflective mask according to claim 28, further comprising at least one selected from the group consisting of a gas.

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