Substrate with multilayer reflective film, reflective mask blank, reflective mask, and method for manufacturing semiconductor device
Patent Information
- Application Number
- JP2023503740
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-22
- Filing Date
- 2022-02-22
- Publication Date
- 2025-01-20
- Estimated Expiration
- 2042-02-22
Abstract
Description
Substrate with multilayer reflective film, reflective mask blank, reflective mask, and method for manufacturing semiconductor device
[0001] The present invention relates to a multilayer reflective film-coated substrate, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device.
[0002] In recent years, with the increasing demand for higher density and precision in VLSI devices, EUV lithography, an exposure technology using extreme ultraviolet (EUV) light, is seen as promising. EUV light refers to light in the wavelength range of soft X-rays or vacuum ultraviolet light, specifically light with a wavelength of approximately 0.2 to 100 nm.
[0003] A reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film to absorb the exposure light. Light incident on the reflective mask mounted on an exposure machine for transferring a pattern onto a semiconductor substrate is absorbed in the areas with the absorber pattern and reflected by the multilayer reflective film in areas without the absorber pattern. The light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflection optical system.
[0004] In order to achieve high density and high precision in semiconductor devices using a reflective mask, it is necessary for the reflective region of the reflective mask (the surface of the multilayer reflective film) to have high reflectivity with respect to EUV light, which is the exposure light.
[0005] Generally, a multilayer reflective film is used in which elements having different refractive indices are periodically stacked. For example, a Mo / Si periodic stacked film in which Mo films and Si films are alternately stacked for about 40 periods is preferably used as a multilayer reflective film for EUV light having a wavelength of 13 to 14 nm.
[0006] Patent Document 1 describes a multilayer reflective film-coated substrate having a multilayer reflective film on the substrate that reflects exposure light. Patent Document 1 also describes that a protective film for protecting the multilayer reflective film is formed on the multilayer reflective film, and that the protective film is a protective film comprising a reflectance reduction suppression layer, a blocking layer, and an etching stopper layer stacked in this order. Patent Document 1 also describes that the etching stopper layer is made of ruthenium (Ru) or an alloy thereof, the reflectance reduction suppression layer is made of a material selected from silicon (Si), silicon oxide, silicon nitride, and silicon oxynitride, and the blocking layer is made of one or more materials selected from magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), rhodium (Rh), hafnium (Hf), tantalum (Ta), and tungsten (W).
[0007] Patent Document 2 describes a multilayer reflective film-coated substrate having a substrate, a multilayer reflective film, and a Ru-based protective film formed on the multilayer reflective film for protecting the multilayer reflective film. Patent Document 2 also describes that the surface layer of the multilayer reflective film opposite the substrate is a layer containing Si, and that a blocking layer is provided between the multilayer reflective film and the Ru-based protective film to prevent Si from migrating to the Ru-based protective film. Patent Document 2 also describes that the blocking layer contains at least one metal selected from the group consisting of Ti, Al, Ni, Pt, Pd, W, Mo, Co, and Cu, alloys of two or more metals, nitrides thereof, silicides thereof, and silicon nitrides thereof, and that a gradient region is present between the Si-containing layer and the blocking layer in which the content of the metal component constituting the blocking layer continuously decreases toward the substrate.
[0008] JP 2014-170931 A International Publication No. 2015 / 012151
[0009] A protective film is formed on the multilayer reflective film to protect the multilayer reflective film from damage caused by dry etching and cleaning during the manufacturing process of the reflective mask. This protective film is often made of a Ru-based material. On the other hand, the top layer of the multilayer reflective film is often made of a material containing Si, so as not to reduce the reflectivity of the multilayer reflective film.
[0010] When the top layer of the multilayer reflective film contains Si, the Si contained in the top layer of the multilayer reflective film diffuses into the protective film due to heating during EUV exposure, and Ru and Si contained in the protective film are bonded to form RuSi. In addition, the heating during annealing in the production of the reflective mask blank can cause oxygen (O ２ ) penetrates the protective film and bonds with Si, forming SiO ２ In some cases, RuSi or SiO was formed in the protective film. ２ When silicides such as these are formed, there is a problem that the reflectivity of the multilayer reflective film to EUV light drops significantly below the calculated value (calculated value assuming no Si diffusion). Furthermore, there is a problem that the durability of the reflective mask deteriorates when chemically unstable Si is exposed on the surface of the multilayer reflective film. Furthermore, it is known that EUV exposure can cause exposure contamination, such as the deposition of a carbon film on the reflective mask. To prevent this, a technique of introducing hydrogen gas into the atmosphere during exposure has been adopted in recent years. When hydrogen gas is introduced into the atmosphere during exposure, the absorber film may lift up and peel off from the surface of the protective film, or the protective film may lift up and peel off from the surface of the multilayer reflective film. (Hereinafter, such a film peeling phenomenon will be referred to as "blistering.") If SiO is present in the protective film, ２ When the layer is formed, the blister resistance (H ２ There is a problem that the resistance to heat is deteriorated.
[0011] The present invention has been made in view of the above circumstances, and aims to provide a multilayer reflective film-coated substrate, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which are capable of preventing a decrease in the reflectivity of the multilayer reflective film due to the formation of silicide in the protective film.
[0012] In order to solve the above problems, the present invention has the following configuration.
[0013] (Structure 1) A substrate with a multilayer reflective film, comprising a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, wherein the protective film includes, on a side in contact with the multilayer reflective film, a SiN material layer containing silicon (Si) and nitrogen (N) or a SiC material layer containing silicon (Si) and carbon (C), and the SiN material layer or the SiC material layer includes an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr).
[0014] (Configuration 2) The multilayer reflective film-coated substrate according to configuration 1, wherein the metal is at least one selected from Y and Zr.
[0015] (Configuration 3) The multilayer reflective film coated substrate according to configuration 1 or 2, wherein the protective film includes a Ru-based material layer on the SiN material layer or the SiC material layer.
[0016] (Configuration 4) A reflective mask blank comprising an absorber film on the protective film of the multilayer reflective film coated substrate according to any one of Configurations 1 to 3.
[0017] (Configuration 5) A reflective mask comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to Configuration 4.
[0018] (Configuration 6) A method for manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus with the reflective mask according to configuration 5 to form a transfer pattern on a transfer target.
[0019] According to the present invention, it is possible to provide a multilayer reflective film-coated substrate, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which are capable of preventing a decrease in the reflectivity of the multilayer reflective film due to the formation of silicide in the protective film.
[0020] Fig. 1 is a cross-sectional view schematically showing an example of a multilayer reflective film-coated substrate of the present embodiment; Fig. 2 is a cross-sectional view schematically showing an example of a reflective mask blank of the present embodiment; Fig. 3 is a cross-sectional view schematically showing another example of a reflective mask blank of the present embodiment; Fig. 4 is a cross-sectional view schematically showing an example of a method for manufacturing a reflective mask; Fig. 5 is a schematic view showing a pattern transfer device;
[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are intended to specifically explain the present invention, and are not intended to limit the scope of the present invention.
[0022] Fig. 1 is a cross-sectional schematic diagram showing an example of a multilayer reflective film-coated substrate 100 of this embodiment. The multilayer reflective film-coated substrate 100 shown in Fig. 1 includes a substrate 10, a multilayer reflective film 12 formed on the substrate 10, and a protective film 14 formed on the multilayer reflective film 12. A back surface conductive film 22 for electrostatic chuck use may be formed on the back surface of the substrate 10 (the surface opposite to the side on which the multilayer reflective film 12 is formed).
[0023] In this specification, "on" a substrate or film includes not only cases where it is in contact with the upper surface of the substrate or film, but also cases where it is not in contact with the upper surface of the substrate or film. In other words, "on" a substrate or film includes cases where a new film is formed above the substrate or film, and cases where another film is interposed between the new film and the substrate or film. Furthermore, "on" does not necessarily mean the upper side in the vertical direction. "On" merely indicates the relative positional relationship of the substrate, film, etc.
[0024] <Substrate> The substrate 10 preferably has a low thermal expansion coefficient within the range of 0±5 ppb / ° C. to prevent distortion of the transferred pattern due to heat during exposure to EUV light. Examples of materials having a low thermal expansion coefficient within this range include SiO ２ -TiO ２ Glasses, multi-component glass ceramics, etc. can be used.
[0025] The main surface of the substrate 10 on which a transfer pattern (an absorber pattern described later) is formed is preferably processed to increase its flatness. Increasing the flatness of the main surface of the substrate 10 can improve the positional accuracy and transfer accuracy of the pattern. For example, in the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less, in a 132 mm × 132 mm area of the main surface of the substrate 10 on which the transfer pattern is formed. Furthermore, the main surface (back surface) opposite the side on which the transfer pattern is formed is fixed to the exposure apparatus by an electrostatic chuck, and in a 142 mm × 142 mm area, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is a value representing the warpage (deformation) of the surface indicated by TIR (Total Indicated Reading). TIR is the absolute value of the difference in height between the highest point on the substrate surface above the focal plane, which is determined by the least squares method with the substrate surface as the reference plane, and the lowest point on the substrate surface below this focal plane.
[0026] In the case of EUV exposure, the surface roughness of the main surface of the substrate 10 on which the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured using an atomic force microscope.
[0027] The substrate 10 preferably has high rigidity to prevent deformation due to film stress of the films (such as the multilayer reflective film 12) formed thereon. The substrate 10 preferably has a high Young's modulus of 65 GPa or more.
[0028] <Multilayer Reflective Film> The multilayer reflective film 12 has a configuration in which a plurality of layers whose main components are elements with different refractive indices are periodically stacked. Generally, the multilayer reflective film 12 is made of a multilayer film in which thin films of high-refractive-index materials, that is, light elements or compounds thereof (high-refractive-index layers), and thin films of low-refractive-index materials, that is, heavy elements or compounds thereof (low-refractive-index layers), are alternately stacked for about 40 to 60 periods.
[0029] To form the multilayer reflective film 12, high refractive index layers and low refractive index layers may be stacked in this order multiple times from the substrate 10 side. In this case, one stacked structure (high refractive index layer / low refractive index layer) constitutes one period.
[0030] It is preferable that the top layer of the multilayer reflective film 12, i.e., the surface layer of the multilayer reflective film 12 opposite the substrate 10, be a high refractive index layer. When a high refractive index layer and a low refractive index layer are stacked in this order from the substrate 10 side, the top layer will be a low refractive index layer. However, if a low refractive index layer is the surface of the multilayer reflective film 12, the low refractive index layer will easily oxidize, reducing the reflectivity of the surface of the multilayer reflective film. Therefore, it is preferable to form a high refractive index layer on the top low refractive index layer. On the other hand, when a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 10 side, the top layer will be a high refractive index layer. In that case, the top high refractive index layer will be the surface of the multilayer reflective film 12.
[0031] In this embodiment, the high refractive index layer may be a layer containing Si. The high refractive index layer may contain simple Si or a Si compound. The Si compound may contain Si and at least one element selected from the group consisting of B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film with excellent reflectivity for EUV light can be obtained.
[0032] In this embodiment, the low refractive index layer may be a layer containing at least one element selected from the group consisting of Mo, Ru, Rh, and Pt, or a layer containing an alloy containing at least one element selected from the group consisting of Mo, Ru, Rh, and Pt.
[0033] For example, as the multilayer reflective film 12 for EUV light with a wavelength of 13 to 14 nm, a Mo / Si multilayer film in which Mo films and Si films are alternately stacked in about 40 to 60 periods can be preferably used. Other multilayer reflective films that can be used in the EUV light region include, for example, Ru / Si periodic multilayer films, Mo / Be periodic multilayer films, Mo compound / Si compound periodic multilayer films, Si / Nb periodic multilayer films, Si / Mo / Ru periodic multilayer films, Si / Mo / Ru / Mo periodic multilayer films, and Si / Ru / Mo / Ru periodic multilayer films. The material of the multilayer reflective film can be selected taking into consideration the exposure wavelength.
[0034] Furthermore, examples of materials for the low refractive index layer include materials containing Ru, such as Ru alone, RuRh, RuNb, and RuMo. When the low refractive index layer contains Ru, a shallow effective reflection surface can be obtained. When the low refractive index layer contains Ru, the stacked structure of the multilayer reflective film 12 preferably has fewer than 40 periods, more preferably 35 periods or less. Furthermore, the stacked structure preferably has 20 periods or more, more preferably 25 periods or more.
[0035] The reflectance of such a single multilayer reflective film 12 is, for example, 65% or more. The upper limit of the reflectance of the multilayer reflective film 12 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 12 can be selected so as to satisfy Bragg's law.
[0036] The multilayer reflective film 12 can be formed by a known method, for example, ion beam sputtering.
[0037] For example, when the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film having a thickness of about 3 nm is formed on the substrate 10 by ion beam sputtering using a Mo target. Next, a Si film having a thickness of about 4 nm is formed using a Si target. By repeating this operation, a multilayer reflective film 12 having 40 to 60 periods of Mo / Si films stacked can be formed. At this time, the surface layer of the multilayer reflective film 12 on the side opposite to the substrate 10 is a layer containing Si (Si film). The thickness of one period of the Mo / Si film is 7 nm.
[0038] <Protective Film> In order to protect the multilayer reflective film 12 from dry etching and cleaning in the manufacturing process of the reflective mask 200, which will be described later, a protective film 14 can be formed on the multilayer reflective film 12 or in contact with the surface of the multilayer reflective film 12. The protective film 14 also has the function of protecting the multilayer reflective film 12 when repairing opacity defects in a transfer pattern (absorber pattern) using an electron beam (EB). Forming the protective film 14 on the multilayer reflective film 12 can suppress damage to the surface of the multilayer reflective film 12 when manufacturing the reflective mask 200. As a result, the reflectivity characteristics of the multilayer reflective film 12 for EUV light are improved.
[0039] The protective film 14 can be formed by a known method, such as ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition.
[0040] In the multilayer reflective film coated substrate 100 of this embodiment, the protective film 14 includes a Si material layer 16 on the side in contact with the multilayer reflective film 12 , and a protective layer 18 formed on the Si material layer 16 .
[0041] In the multilayer reflective film coated substrate 100 of this embodiment, the Si material layer 16 is a SiN material layer containing silicon (Si) and nitrogen (N), or a SiC material layer containing silicon (Si) and carbon (C).
[0042] The SiN material layer is a layer containing silicon (Si) and nitrogen (N). The SiN material layer may further contain other elements, for example, O, C, B, and / or H. The SiN material layer is, for example, silicon nitride (Si ｘ N ｙ (x and y are integers of 1 or more)), and silicon oxynitride (Si ｘ O ｙ N ｚ (x, y, and z are integers of 1 or more) The SiN material layer may include at least one material selected from, for example, SiN, Si ３ N ４ , and SiON.
[0043] The SiC material layer is a layer containing silicon (Si) and carbon (C). The SiN material layer may further contain other elements, such as O, N, B, and / or H. The SiC material layer includes, for example, silicon carbide (SiC).
[0044] When the high refractive index layer of the multilayer reflective film 12 is a Si film and a low refractive index layer (e.g., a Mo film) and a high refractive index layer (Si film) are laminated in this order from the substrate 10 side, the Si material layer 16 may be a SiN material layer or a SiC material layer as a high refractive index layer provided as the uppermost layer of the multilayer reflective film 12. Alternatively, when a low refractive index layer and a high refractive index layer (Si film) are laminated in this order from the substrate 10 side, a high refractive index layer (Si film) may be provided as the uppermost layer of the multilayer reflective film 12, and a SiN material layer or a SiC material layer may be provided thereon.
[0045] In the multilayer reflective film coated substrate 100 of this embodiment, the SiN material layer or the SiC material layer is characterized by containing an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr). By containing an oxide of at least one metal selected from these metals in the SiN material layer or the SiC material layer, RuSi and SiO ２ Therefore, it is possible to prevent the formation of silicides such as silicides.
[0046] If Si contained in the Si material layer 16 diffuses into the protective layer 18 due to heating during EUV exposure, Si may bond with a metal (e.g., Ru) contained in the protective layer 18 to form a metal silicide. If a metal silicide is formed in the protective layer 18, there is a problem that the reflectivity of the multilayer reflective coating 12 for EUV light will be significantly lower than the calculated value (the calculated value assuming no Si diffusion). According to the multilayer reflective film-coated substrate 100 of this embodiment, since the Si material layer 16 is a SiN material layer or a SiC material layer, diffusion of Si into the protective layer 18 can be prevented, and therefore, metal silicide (e.g., RuSi) can be prevented from being formed in the protective layer 18. As a result, it is possible to prevent the reflectivity of the multilayer reflective coating 12 for EUV light from being significantly lower than the calculated value.
[0047] The heating during annealing in the manufacture of a reflective mask blank increases the oxygen (O ２ ) penetrates the protective layer 18 and bonds with Si, forming SiO ２ In this way, a layer containing SiO may be formed in the protective film 14. ２ When the layer is formed, the blister resistance (H ２ According to the multilayer reflective film coated substrate 100 of this embodiment, the protective film 14 does not contain SiO. ２ As a result, the blister resistance (H) of the reflective mask during exposure can be improved. ２ This can prevent deterioration of the resistance.
[0048] The protective film 14 contains SiO ２ The reason why the formation of the layer can be prevented is as follows.
[0049] As described above, the SiN material layer or SiC material layer constituting the Si material layer 16 contains an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr). The standard free energy of formation (ΔG) of oxides of these metals and the SiO ２ The magnitude relationship of the standard free energy of formation (ΔG) of SiO is as follows: ２ >TiO ２ > ZrO ２ >Al ２ O ３ > MgO > Y ２ O ３
[0050] Therefore, the oxygen in the atmosphere (O ２ ) has a stronger tendency than Si to bond with at least one of the above metal elements to form a metal oxide, and therefore, SiO ２ It is believed that this can suppress the formation of
[0051] Furthermore, according to the multilayer reflective film coated substrate 100 of this embodiment, it is possible to prevent deterioration of the durability of the reflective mask due to exposure of Si, which has low chemical stability, to the surface layer of the multilayer reflective film 12.
[0052] The metal oxide contained in the SiN material layer or the SiC material layer is preferably an oxide of at least one metal element selected from Y and Zr. This is because the extinction coefficients (k) of Y and Zr for light with a wavelength of 13.5 nm are low, at 0.01 or less, and therefore when the SiN material layer or the SiC material layer contains oxides of these metals, the reflectivity of the multilayer reflective film 12 for EUV light hardly decreases.
[0053] The SiN material layer 16 is preferably formed by a PVD method (e.g., magnetron sputtering) using a SiN sintered body as a target. When forming the SiN sintered body, it is preferable to add an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr) as a sintering aid. By adding a sintering aid, a high-density SiN sintered body can be formed. By using a high-density SiN sintered body as a target, a high-quality SiN material layer with few defects can be formed. The SiN material layer formed in this manner contains the oxide of the metal added as a sintering aid.
[0054] The SiC material layer 16 is preferably formed by a physical vapor deposition (PVD) method (e.g., magnetron sputtering) using a SiC sintered body as a target. When forming the SiC sintered body, it is preferable to add an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr) as a sintering aid. By adding a sintering aid, a high-density SiC sintered body can be formed. By using a high-density SiC sintered body as a target, a high-quality SiC material layer with few defects can be formed. The SiC material layer formed in this manner contains the oxide of the metal added as a sintering aid.
[0055] The SiN or SiC material layer may be a single layer. The term "single layer" here means that the metal content (atomic %) in the SiN or SiC material layer (at least one metal selected from Mg, Al, Ti, Y, and Zr) is substantially constant (within ±20 atomic %, preferably within ±10 atomic %) throughout the thickness of the film. The SiN or SiC material layer may also be a gradient film (a film in which the metal content varies continuously throughout the thickness). It is preferable that the SiN or SiC material layer have a higher metal oxide content on the side in contact with the protective layer 18 than on the side in contact with the multilayer reflective film 12. This more effectively prevents Si from diffusing into the protective layer 18 when the multilayer reflective film-coated substrate 100 is heated.
[0056] A protective layer 18 is formed on the Si material layer 16. The protective layer 18 can be formed using a known method, such as ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition.
[0057] The protective layer 18 is preferably formed of a material having an etching selectivity different from that of the absorber film 24 described below. Examples of materials for the protective layer 18 include Ru, Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo), Si-(Ru, Rh, Cr, B), Si, Zr, Nb, La, and B. The protective layer 18 is preferably a Ru-based material layer containing ruthenium (Ru). Specifically, the material for the protective layer 18 is preferably Ru or Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo). Such a protective layer 18 is particularly effective when the absorber film 24 is formed of a Ta-based material and is patterned by dry etching using a Cl-based gas.
[0058] The protective layer 18 may further contain at least one element selected from the group consisting of nitrogen (N), oxygen (O), carbon (C), and boron (B).
[0059] The multilayer reflective film 12, the Si material layer 16, and the protective layer 18 may be formed by the same method or by different methods. For example, the multilayer reflective film 12 may be formed by ion beam sputtering, and then the Si material layer 16 and the protective layer 18 may be successively formed by magnetron sputtering. Alternatively, the multilayer reflective film 12 and the Si material layer 16 may be successively formed by ion beam sputtering, and then the protective layer 18 may be formed by magnetron sputtering. Alternatively, the multilayer reflective film 12 to the protective layer 18 may be successively formed by ion beam sputtering. When forming these films, a single target or two or more targets may be used. Furthermore, the multilayer reflective film-coated substrate on which the multilayer reflective film 12, the Si material layer 16, and the protective layer 18 have been formed may be subjected to a heat treatment at 100°C to 300°C in an air atmosphere or a nitrogen atmosphere to relieve film stress in the multilayer reflective film.
[0060] The N content in the SiN material layer is preferably 20 atomic % to 70 atomic %, and more preferably 40 atomic % to 60 atomic %. If the N content in the SiN material layer is less than 20 atomic %, the effect of preventing Si from diffusing into the protective layer 18 cannot be sufficiently obtained. If the N content in the SiN material layer is more than 70 atomic %, the film density of the SiN material layer decreases, which in turn deteriorates durability and reduces reflectivity.
[0061] The C content in the SiC material layer is preferably 20 atomic % to 80 atomic %, and more preferably 40 atomic % to 70 atomic %. If the C content in the SiC material layer is less than 20 atomic %, the effect of preventing Si from diffusing into the protective layer 18 cannot be sufficiently obtained. If the C content in the SiC material layer exceeds 80 atomic %, the film density of the SiC material layer decreases, and durability is instead deteriorated.
[0062] As described above, the Si material layer 16 (SiN material layer or SiC material layer) contains an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr). The content of oxygen (O) in the SiN material layer is preferably 0.5 atomic % to 20 atomic %, and more preferably 1.5 atomic % to 15 atomic %. When the content of O in the SiN material layer is less than 0.5 atomic %, SiO ２ If the O content in the SiN material layer exceeds 20 atomic %, the reflectivity of the multilayer reflective film will drop sharply. The oxygen (O) content in the SiC material layer is preferably 0.1 atomic % to 15 atomic %, more preferably 0.2 atomic % to 12 atomic %. If the O content in the SiC material layer is less than 0.1 atomic %, the SiO ２ If the O content in the SiC material layer exceeds 15 atomic %, the reflectance of the multilayer reflective film drops sharply.
[0063] The content of the metal (at least one metal selected from Mg, Al, Ti, Y, and Zr) in the SiN material layer is preferably 0.1 atomic % to 10 atomic %, more preferably 0.5 atomic % to 6.0 atomic %. When the content of the metal in the SiN material layer is less than 0.1 atomic %, SiO ２ If the content of the metal in the SiN material layer exceeds 10 atomic %, the reflectivity of the multilayer reflective film will drop sharply. The content of the metal (at least one metal selected from Mg, Al, Ti, Y, and Zr) in the SiC material layer is preferably 0.05 atomic % to 3.0 atomic %, more preferably 0.1 atomic % to 2.5 atomic %. If the content of the metal in the SiC material layer is less than 0.05 atomic %, the SiO ２ If the content of the metal in the SiC material layer exceeds 3.0 atomic %, the reflectance of the multilayer reflective film drops sharply.
[0064] Fig. 2 is a cross-sectional schematic diagram showing an example of a reflective mask blank 110 of this embodiment. The reflective mask blank 110 shown in Fig. 2 has an absorber film 24 for absorbing EUV light on the protective film 14 of the above-mentioned multilayer reflective film-coated substrate 100. Note that the reflective mask blank 110 can further have another thin film, such as a resist film 26, on the absorber film 24.
[0065] 3 is a cross-sectional schematic view showing another example of the reflective mask blank 110 of this embodiment. As shown in FIG. 3, the reflective mask blank 110 may have an etching mask film 28 between the absorber film 24 and the resist film 26.
[0066] <Absorber Film> The absorber film 24 of the reflective mask blank 110 of this embodiment is formed on the protective film 14. The basic function of the absorber film 24 is to absorb EUV light. The absorber film 24 may be an absorber film 24 intended for absorbing EUV light, or an absorber film 24 having a phase shift function that also takes into account the phase difference of EUV light. The absorber film 24 having a phase shift function not only absorbs EUV light but also reflects a portion of the EUV light to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 24 having a phase shift function, the absorber film 24 absorbs and attenuates EUV light in the portion where it is formed, while reflecting a portion of the EUV light at a level that does not adversely affect pattern transfer. Furthermore, in the region (field portion) where the absorber film 24 is not formed, the EUV light is reflected by the multilayer reflective film 12 via the protective film 14. Therefore, a desired phase difference occurs between the light reflected from the absorber film 24 having a phase shift function and the light reflected from the field portion. The absorber film 24 having a phase shift function is preferably formed so that the phase difference between the light reflected from the absorber film 24 and the light reflected from the multilayer reflective film 12 is 170 to 190 degrees. Light beams with an inverted phase difference of approximately 180 degrees interfere with each other at the pattern edge portion, thereby improving the image contrast of the projected optical image. As the image contrast improves, the resolution increases, and various exposure latitudes such as exposure dose latitude and focus latitude can be increased.
[0067] The absorber film 24 may be a single-layer film or a multilayer film consisting of multiple films (e.g., a lower-layer absorber film and an upper-layer absorber film). In the case of a single-layer film, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constants and film thickness of the upper-layer absorber film can be appropriately set so that it serves as an anti-reflection film during optical mask pattern defect inspection. This improves inspection sensitivity during optical mask pattern defect inspection. Furthermore, using a film containing oxygen (O) or nitrogen (N), which improves oxidation resistance, as the upper-layer absorber film improves stability over time. Thus, by forming the absorber film 24 into a multilayer film, various functions can be added to the absorber film 24. When the absorber film 24 has a phase shift function, forming it into a multilayer film can increase the range of optical adjustment, making it easier to obtain a desired reflectance.
[0068] The material of the absorber film 24 is not particularly limited as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity relative to the protective film 14. As a material having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or a compound (alloy) thereof can be preferably used.
[0069] The absorber film 24 can be formed by magnetron sputtering such as DC sputtering and RF sputtering. For example, the absorber film 24 made of a tantalum compound or the like can be formed by reactive sputtering using a target containing tantalum and boron and argon gas to which oxygen or nitrogen is added.
[0070] The tantalum compound for forming the absorber film 24 includes an alloy of Ta and the above-mentioned metals. When the absorber film 24 is an alloy of Ta, the crystalline state of the absorber film 24 is preferably an amorphous or microcrystalline structure in terms of smoothness and flatness. If the surface of the absorber film 24 is not smooth or flat, the edge roughness of the absorber pattern 24a may increase, resulting in poor dimensional accuracy of the pattern. The surface roughness of the absorber film 24 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in root-mean-square roughness (Rms).
[0071] Examples of tantalum compounds for forming the absorber film 24 include compounds containing Ta and B, compounds containing Ta and N, compounds containing Ta, O and N, compounds containing Ta and B and further containing at least one of O and N, compounds containing Ta and Si, compounds containing Ta, Si and N, compounds containing Ta and Ge, and compounds containing Ta, Ge and N.
[0072] Ta has a large absorption coefficient for EUV light and is a material that can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, Ta can be said to be a material with excellent processability for the absorber film 24. Furthermore, by adding B, Si, and / or Ge, etc. to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 24 can be improved. Furthermore, by adding N and / or O to Ta, the resistance of the absorber film 24 to oxidation is improved, thereby improving stability over time.
[0073] <Etching Mask Film> An etching mask film 28 may be formed on the absorber film 24. As a material for the etching mask film 28, it is preferable to use a material that has a high etching selectivity of the absorber film 24 to the etching mask film 28. The etching selectivity of the absorber film 24 to the etching mask film 28 is preferably 1.5 or more, and more preferably 3 or more.
[0074] The reflective mask blank 110 of this embodiment preferably has an etching mask film 28 containing chromium (Cr) on the absorber film 24. When the absorber film 24 is etched with a fluorine-based gas, it is preferable to use chromium or a chromium compound as the material of the etching mask film 28. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. The etching mask film 28 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and even more preferably is a CrO-based film containing chromium and oxygen (a CrO film, CrON film, CrOC film, or CrOCN film).
[0075] When the absorber film 24 is etched with a chlorine-based gas that does not substantially contain oxygen, it is preferable to use silicon or a silicon compound as the material for the etching mask film 28. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as metal silicon (metal silicides) and metal silicon compounds (metal silicide compounds) that contain a metal in silicon or a silicon compound. Examples of metal silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C, and H.
[0076] The thickness of the etching mask film 28 is preferably 3 nm or more in order to form a pattern with high precision in the absorber film 24. Moreover, the thickness of the etching mask film 28 is preferably 15 nm or less in order to make the thickness of the resist film 26 thin.
[0077] <Backside Conductive Film> A backside conductive film 22 for electrostatic chuck may be formed on the backside of the substrate 100 (the surface opposite to the surface on which the multilayer reflective film 12 is formed). The sheet resistance required for the backside conductive film 22 for electrostatic chuck use is typically 100 Ω / □ (Ω / square) or less. The backside conductive film 22 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material for the backside conductive film 22 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material for the backside conductive film 22 is preferably a Cr compound containing Cr and at least one element selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the back surface conductive film 22 is preferably Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.
[0078] The thickness of the back surface conductive film 22 is not particularly limited as long as it functions as a film for an electrostatic chuck, but is, for example, 10 nm to 200 nm.
[0079] <Reflection Mask> The reflection mask blank 110 of this embodiment can be used to manufacture the reflection mask 200 of this embodiment. An example of a method for manufacturing a reflection mask will now be described.
[0080] 4A to 4E are schematic diagrams showing an example of a method for manufacturing the reflective mask 200.
[0081] 4A-4E, first, a reflective mask blank 110 is prepared, which includes a substrate 10, a multilayer reflective film 12 formed on the substrate 10, a protective film 14 (a Si material layer 16 and a protective layer 18) formed on the multilayer reflective film 12, and an absorber film 24 formed on the protective film 14 (FIG. 4A). Next, a resist film 26 is formed on the absorber film 24 (FIG. 4B). A pattern is written on the resist film 26 using an electron beam lithography system, and a resist pattern 26a is formed by further undergoing a development and rinsing process (FIG. 4C).
[0082] Using the resist pattern 26a as a mask, the absorber film 24 is dry-etched, whereby the portions of the absorber film 24 that are not covered by the resist pattern 26a are etched, and an absorber pattern 24a is formed (FIG. 4D).
[0083] As the etching gas for the absorber film 24, for example, a fluorine-based gas and / or a chlorine-based gas can be used. As the fluorine-based gas, CF ４ , CHF ３ , C2F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ , C.H. ２ F ２ , C.H. ３ F, C ３ F ８ , S.F. ６ , and F ２ The chlorine-based gas may be Cl ２ , SiCl ４ , CHCl ３ , CCl ４ , and BCl ３ In addition, a fluorine-based gas and / or a chlorine-based gas and O ２ In this case, a mixed gas containing a predetermined ratio of these may be used. These etching gases may further contain an inert gas such as He and / or Ar, if necessary.
[0084] After the absorber pattern 24a is formed, the resist pattern 26a is removed with a resist remover solution, and after the resist pattern 26a is removed, a wet cleaning process using an acidic or alkaline aqueous solution is performed to obtain the reflective mask 200 of this embodiment (FIG. 4E).
[0085] In addition, when a reflective mask blank 110 in which an etching mask film 28 is formed on the absorber film 24 is used, an additional process is performed in which a pattern (etching mask pattern) is formed on the etching mask film 28 using the resist pattern 26a as a mask, and then a pattern is formed on the absorber film 24 using the etching mask pattern as a mask.
[0086] The reflective mask 200 thus obtained has a structure in which a multilayer reflective film 12, a protective film 14 (Si material layer 16 and protective layer 18), and an absorber pattern 24a are laminated on a substrate 10.
[0087] An area 30 where the multilayer reflective film 12 (including the protective film 14) is exposed has the function of reflecting EUV light. An area 32 where the multilayer reflective film 12 (including the protective film 14) is covered with the absorber pattern 24a has the function of absorbing EUV light. According to the reflective mask 200 of this embodiment, the thickness of the absorber pattern 24a can be made thinner than before so that the reflectivity becomes, for example, 2.5% or less, and therefore a finer pattern can be transferred onto a transfer target.
[0088] <Method for Manufacturing a Semiconductor Device> A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask 200 of this embodiment. This transfer pattern has a shape that is the result of transferring the pattern of the reflective mask 200. A semiconductor device can be manufactured by forming a transfer pattern on a semiconductor substrate using the reflective mask 200.
[0089] A method of transferring a pattern onto a semiconductor substrate 56 with a resist by using EUV light will be described with reference to FIG.
[0090] 5 shows a pattern transfer device 50. The pattern transfer device 50 includes a laser plasma X-ray source 52, a reflective mask 200, and a reduction optical system 54. An X-ray reflection mirror is used as the reduction optical system 54.
[0091] The pattern reflected by the reflective mask 200 is reduced, usually to about 1 / 4, by the reduction optical system 54. For example, a wavelength band of 13 to 14 nm is used as the exposure wavelength, and the optical path is preset to be in a vacuum. Under these conditions, EUV light generated by the laser plasma X-ray source 52 is made incident on the reflective mask 200. The light reflected by the reflective mask 200 is transferred onto a resist-coated semiconductor substrate 56 via the reduction optical system 54.
[0092] The light reflected by the reflective mask 200 enters the reduction optical system 54. The light that enters the reduction optical system 54 forms a transfer pattern in a resist layer on the resist-coated semiconductor substrate 56. By developing the exposed resist layer, a resist pattern can be formed on the resist-coated semiconductor substrate 56. By etching the semiconductor substrate 56 using the resist pattern as a mask, it is possible to form, for example, a predetermined wiring pattern on the semiconductor substrate. A semiconductor device is manufactured through these and other necessary processes.
[0093] Examples, Reference Examples and Comparative Examples will be described below with reference to the drawings.
[0094] (Fabrication of the multilayer reflective film coated substrate 100) First, a substrate 10 having a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) and having a first main surface and a second main surface polished was prepared. This substrate 10 was made of low thermal expansion glass (SiO ２ -TiO ２ The main surface of the substrate 10 was polished through a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.
[0095] Next, a multilayer reflective film 12 was formed on the main surface (first main surface) of the substrate 10. The multilayer reflective film 12 formed on the substrate 10 was a periodic multilayer reflective film 12 made of Mo and Si in order to be suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 12 was formed by alternately stacking Mo films and Si films on the substrate 10 by ion beam sputtering using Mo targets and Si targets and krypton (Kr) as the process gas. First, a Si film was formed to a thickness of 4.2 nm, followed by a Mo film to a thickness of 2.8 nm. This constituted one period, and 40 periods were similarly stacked to form the multilayer reflective film 12.
[0096] Next, a Si material layer 16 was formed on the multilayer reflective film 12. The Si material layer 16 was formed to a thickness of 3.5 nm by magnetron sputtering in an Ar gas atmosphere using a target made of a SiC sintered body or a SiN sintered body. The SiC sintered body or the SiN sintered body used as the target was doped with an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), yttrium (Y), and zirconium (Zr) as a sintering aid. Meanwhile, in Reference Example 1, a SiN sintered body was used as the target to form the Si material layer. No sintering aid was added to this target. In Reference Example 2, a SiC sintered body was used as the target to form the Si material layer. No sintering aid was added to this target. In Comparative Example 1, simple Si was used as the target to form the Si material layer.
[0097] Next, a RuNb film was formed as a protective layer 18 on the Si material layer 16. The protective layer 18 was formed to a thickness of 3.5 nm by magnetron sputtering in an Ar gas atmosphere using a RuNb target.
[0098] (Evaluation of the multilayer reflective film coated substrate 100) Using the multilayer reflective film coated substrates 100 of the Examples, Reference Examples, and Comparative Examples prepared above, the presence or absence of a change in reflectance after heating the multilayer reflective film coated substrate 100 and the amount of SiO in the protective film 14 were evaluated. ２ The presence or absence of layer formation was confirmed.
[0099] Specifically, first, the reflectivity of the multilayer reflective film-coated substrate 100 of the example, reference example, and comparative example to EUV light was measured. Next, the multilayer reflective film-coated substrate 100 was heated in an air atmosphere at 200°C for 10 minutes. After heating the multilayer reflective film-coated substrate 100, the reflectivity of the multilayer reflective film-coated substrate 100 to EUV light was measured. The change in reflectivity of the multilayer reflective film-coated substrate 100 was evaluated by subtracting the reflectivity (%) of the multilayer reflective film-coated substrate 100 before heating from the reflectivity (%) of the multilayer reflective film-coated substrate 100 after heating.
[0100] Furthermore, after the multilayer reflective film coated substrate 100 was heated at 200° C. for 10 minutes, a cross section of the protective film 14 was observed with an electron microscope, and it was found that SiO ２ It was confirmed whether a layer was formed or not.
[0101] The following Table 1 shows whether or not the reflectance of the multilayer reflective film coated substrate 100 has changed, and the amount of SiO in the protective film 14. ２ The results of confirming whether or not a layer was formed are shown below. Table 1 below also shows the film composition and film thickness of the Si material layer 16 in the example, reference example, and comparative example after heating the multilayer reflective film-coated substrate 100. The film composition and metal oxide of the Si material layer 16 were measured by X-ray photoelectron spectroscopy (XPS) and dynamic SIMS (secondary ion mass spectroscopy). The composition of the RuNb film was measured by X-ray photoelectron spectroscopy (XPS) and was found to be Ru:Nb=80:20.
[0102]
[0103] As can be seen from the results shown in Table 1, in the multilayer reflective film coated substrates 100 of Examples 1 to 8 and Reference Examples 1 and 2, the reflectivity of the multilayer reflective film coated substrates 100 for EUV light hardly changed before and after heating at 200° C. In particular, the change in reflectivity was small in Examples 3 and 4. In Examples 1 to 8 and Reference Examples 1 and 2, the Si material layer 16 was a SiN layer or a SiC layer, so that diffusion of Si from the Si material layer 16 to the protective layer 18 was suppressed, and it is presumed that this was because the formation of metal silicide (RuSi) in the protective layer 18 was suppressed.
[0104] On the other hand, in the multilayer reflective film-coated substrate 100 of Comparative Example 1, the reflectivity of the multilayer reflective film-coated substrate 100 for EUV light changed significantly before and after heating at 200° C. In Comparative Example 1, it is presumed that this was caused by the diffusion of Si from the Si material layer 16 into the protective layer 18, resulting in the formation of metal silicide (RuSi) in the protective layer 18.
[0105] In addition, in the multilayer reflective film coated substrates 100 of Examples 1 to 8, after heating at 200° C., SiO ２ In Examples 1 to 8, since the metal oxide was added to the Si material layer 16, the SiO ２ On the other hand, in the multilayer reflective film coated substrates 100 of Reference Examples 1 and 2 and Comparative Example 1, after heating at 200° C., the generation of SiO ２ In Reference Examples 1 and 2 and Comparative Example 1, since no metal oxide was added to the Si material layer 16, a SiO layer was formed in the protective film 14. ２ It is presumed that this was the cause of the
[0106] REFERENCE SIGNS LIST 10 Substrate 12 Multilayer reflective film 14 Protective film 16 Si material layer 18 Protective layer 22 Back surface conductive film 24a Absorber pattern 24 Absorber film 26a Resist pattern 26 Resist film 28 Etching mask film 50 Pattern transfer device 100 Substrate with multilayer reflective film 110 Reflective mask blank 200 Reflective mask
Claims
1. A multilayer reflective film-coated substrate having a substrate, a multilayer reflective film provided on the substrate, and a protective film provided on the multilayer reflective film, the protective film includes, on a side in contact with the multilayer reflective film, a SiN material layer containing silicon (Si) and nitrogen (N) or a SiC material layer containing silicon (Si) and carbon (C); The substrate with a multilayer reflective film, wherein the SiN material layer or the SiC material layer contains an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y) and zirconium (Zr).
2. A substrate with a multilayer reflective film as described in claim 1, characterized in that the protective film includes a SiN material layer.
3. The multilayer reflective film-coated substrate as described in claim 2, characterized in that the metal content of the SiN material layer is 0.1 atomic % to 10 atomic %.
4. The multilayer reflective film-coated substrate as described in claim 2, characterized in that the oxygen content of the SiN material layer is 0.5 atomic % to 20 atomic %.
5. The multilayer reflective film-coated substrate as described in claim 2, characterized in that the nitrogen content of the SiN material layer is 20 atomic % to 70 atomic %.
6. A substrate with a multilayer reflective film as described in claim 1, characterized in that the protective film includes the SiC material layer.
7. The multilayer reflective film-coated substrate as described in claim 6, characterized in that the metal content of the SiC material layer is 0.05 atomic % to 3.0 atomic %.
8. The multilayer reflective film-coated substrate as described in claim 6, characterized in that the oxygen content of the SiC material layer is 0.1 atomic % to 15 atomic %.
9. The multilayer reflective film-coated substrate as described in claim 6, characterized in that the carbon content of the SiC material layer is 20 atomic % to 80 atomic %.
10. 2. The substrate with a multilayer reflective film according to claim 1, wherein the protective film includes a Ru-based material layer on the SiN material layer or the SiC material layer.
11. A reflective mask blank comprising an absorber film on the protective film of the multilayer reflective film-coated substrate according to claim 1 .
12. A reflective mask comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to claim 11.
13. 13. A method for manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus with the reflective mask according to claim 12 to form a transfer pattern on a transfer target.