Substrate with multilayer reflective film, reflective mask blank, reflective mask, and method for manufacturing a semiconductor device.

Abstract

The present invention provides a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which can prevent a decrease in the reflectivity of the multilayer reflective film due to the formation of silicides in the protective film. [Solution] The substrate 100 with a multilayer reflective film comprises a substrate 10, a multilayer reflective film 12 provided on the substrate 10, and a protective film 14 provided on the multilayer reflective film 12. The protective film 14 includes a SiN material layer containing silicon (Si) and nitrogen (N) or a SiC material layer containing silicon (Si) and carbon (C) on the side in contact with the multilayer reflective film 12. The 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).

Description

Technical Field

[0001] The present invention relates to a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device.

Background Art

[0002] With the further requirements for higher density and higher precision of ultra-LSI devices in recent years, extreme ultraviolet (EUV) lithography, an exposure technique using EUV light, has been regarded as promising. EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm.

[0003] A reflective mask has a multilayer reflective film formed on a substrate for reflecting exposure light, and a pattern-shaped absorber film formed on the multilayer reflective film for absorbing exposure light, which is an absorber pattern. The light incident on the reflective mask mounted on an exposure machine for pattern transfer on a semiconductor substrate is absorbed in the part with the absorber pattern and reflected by the multilayer reflective film in the part 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 reflective optical system.

[0004] In order to achieve higher density and higher precision of semiconductor devices using a reflective mask, it is necessary for the reflective region (the surface of the multilayer reflective film) in the reflective mask to have a high reflectivity with respect to EUV light, which is the exposure light.

[0005] Generally, as the multilayer reflective film, a multilayer film in which elements with different refractive indices are periodically laminated is used. For example, as the multilayer reflective film for EUV light with a wavelength of 13 to 14 nm, a Mo / Si periodically laminated film in which Mo films and Si films are alternately laminated about 40 cycles is preferably used.

[0006] Patent Document 1 describes a substrate with a multilayer reflective film that reflects exposure light on the substrate. 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 formed by laminating a reflectance reduction suppression layer, a blocking layer, and an etching stopper layer in that order. Furthermore, Patent Document 1 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 substrate with a multilayer reflective film, comprising 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 Si-containing layer, and that there is a block layer between the multilayer reflective film and the Ru-based protective film that prevents the migration of Si to the Ru-based protective film. Patent Document 2 also describes that the block layer contains at least one metal selected from Ti, Al, Ni, Pt, Pd, W, Mo, Co, Cu and alloys of two or more metals, nitrides thereof, silicides thereof, and silinites thereof, and that there is a gradient region between the Si-containing layer and the block layer in which the content of the metal component constituting the block layer continuously decreases toward the substrate. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2014-170931 [Patent Document 2] International Publication No. 2015 / 012151 [Disclosure of the Invention]

[0009] A protective film is formed on top of the multilayer reflective film to protect it from damage caused by dry etching and cleaning during the manufacturing process of reflective masks. Ru-based materials are often used for this protective film. On the other hand, the top layer of the multilayer reflective film is often formed from a Si-containing material to avoid reducing the reflectivity of the multilayer reflective film.

[0010] When Si is present in the uppermost layer of a multilayer reflective film, heating during EUV exposure can cause the Si in the uppermost layer to diffuse into the protective film, potentially leading to the formation of RuSi through bonding with Si in the protective film. Additionally, heating during annealing in the manufacturing of reflective mask blanks can allow oxygen (O2) from the atmosphere to permeate the protective film and bond with Si, forming SiO2. The formation of silicides such as RuSi and SiO2 in the protective film presents a problem: the reflectivity of the multilayer reflective film to EUV light drops significantly below the calculated value (assuming no Si diffusion). Furthermore, the exposure of chemically unstable Si to the surface of the multilayer reflective film degrades the durability of the reflective mask. Moreover, EUV exposure is known to cause exposure contamination, such as the deposition of carbon film on the reflective mask. To suppress this, the introduction of hydrogen gas into the exposure atmosphere has recently been adopted. However, introducing hydrogen gas into the exposure atmosphere can cause the absorber film to lift and peel off the protective film, or the protective film to lift and peel off the multilayer reflective film. (Hereafter, this phenomenon of film peeling will be referred to as "blistering.") When an SiO2 layer is formed in the protective film, there is a problem in that the blister resistance (H2 resistance) of the reflective mask in the exposure machine deteriorates.

[0011] This invention has been made in view of the above circumstances, and aims to provide a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device that can prevent a decrease in the reflectivity of the multilayer reflective film due to the formation of silicide in the protective film.

[0012] To solve the above problems, the present invention has the following configuration.

[0013] (Configuration 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, The protective film includes, on the 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). A multilayer reflective substrate characterized in that the 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).

[0014] (Configuration 2) The substrate with a multilayer reflective film according to Configuration 1, characterized in that the metal is at least one selected from Y and Zr.

[0015] (Configuration 3) A multilayer reflective substrate according to Configuration 1 or 2, characterized in that the protective film includes a Ru-based material layer on top of the SiN material layer or SiC material layer.

[0016] (Configuration 4) A reflective mask blank characterized by having an absorbent film on the protective film of a multilayer reflective film substrate as described in any of Configurations 1 to 3.

[0017] (Configuration 5) A reflective mask characterized by having an absorbent pattern obtained by patterning the absorbent membrane of the reflective mask blank described in Configuration 4.

[0018] A method for manufacturing a semiconductor device, comprising a step of performing a lithography process using an exposure apparatus with the reflective mask described in Configuration 5 to form a transfer pattern on a transfer target.

[0019] According to the present invention, it is possible to provide a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which can prevent a decrease in the reflectance of the multilayer reflective film due to the formation of silicide in the protective film.

Brief Description of the Drawings

[0020] [Figure 1] It is a cross-sectional schematic view showing an example of a substrate with a multilayer reflective film of the present embodiment. [Figure 2] It is a cross-sectional schematic view showing an example of a reflective mask blank of the present embodiment. [Figure 3] It is a cross-sectional schematic view showing another example of a reflective mask blank of the present embodiment. [Figure 4A-E] It is a schematic view showing an example of a method for manufacturing a reflective mask. [Figure 5] It is a schematic view showing a pattern transfer device.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The following embodiments are for specifically explaining the present invention and do not limit the present invention within its scope.

[0022] FIG. 1 is a cross-sectional schematic view showing an example of a substrate 100 with a multilayer reflective film of the present embodiment. The substrate 100 with a multilayer reflective film 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 an electrostatic chuck may be formed on the back surface of the substrate 10 (the surface opposite to the side where the multilayer reflective film **********

[0023] In this specification, "on top of" 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. That is, "on top of" a substrate or film includes cases where a new film is formed on top of the substrate or film, and cases where another film is interposed between the new film and the substrate or film. Furthermore, "on top of" does not necessarily mean the upper side in the vertical direction. "On top of" merely indicates the relative positional relationship of the substrate or film, etc.

[0024] <Circuit board> To prevent distortion of the transfer pattern due to heat during exposure with EUV light, the substrate 10 is preferably made of a material with a low thermal expansion coefficient in the range of 0 ± 5 ppb / °C. Examples of materials with a low thermal expansion coefficient in this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0025] The main surface of the substrate 10 on the side where the transfer pattern (absorber pattern described later) is formed is preferably processed to increase its flatness. By increasing the flatness of the main surface of the substrate 10, the positional accuracy and transfer accuracy of the pattern can be improved. For example, in the case of EUV exposure, the flatness of the 132 mm × 132 mm area of ​​the main surface of the substrate 10 on the side where the transfer pattern is formed is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. The main surface (back side) on the side opposite to the side where the transfer pattern is formed is the surface that is fixed to the exposure apparatus by an electrostatic chuck, and the flatness of the 142 mm × 142 mm area of ​​this surface is preferably 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 surface warp (amount of deformation) as shown by TIR (Total Indicated Reading). TIR is the absolute difference in height between the highest point on the substrate surface above the focal plane and the lowest point on the substrate surface below the focal plane, with the focal plane being defined by the least squares method relative to the substrate surface.

[0026] In the case of EUV exposure, the surface roughness of the main surface on the side of the substrate 10 where the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). Surface roughness can be measured using an atomic force microscope.

[0027] The substrate 10 is preferably made of high rigidity in order to prevent deformation due to film stress of the film (such as the multilayer reflective film 12) formed on it. In particular, the substrate 10 is preferably made of a high Young's modulus of 65 GPa or more.

[0028] <Multilayer reflective film> The multilayer reflective film 12 has a structure in which multiple layers, mainly composed of elements with different refractive indices, are periodically stacked. Generally, the multilayer reflective film 12 consists of a multilayer film in which thin films of light elements or compounds thereof, which are high refractive index materials (high refractive index layers), and thin films of heavy elements or compounds thereof, which are low refractive index materials (low refractive index layers), are alternately stacked for about 40 to 60 periods.

[0029] To form the multilayer reflective film 12, multiple layers of high refractive index layers and low refractive index layers may be stacked in this order from the substrate 10 side in multiple periods. In this case, one (high refractive index layer / low refractive index layer) stacked structure constitutes one period.

[0030] Furthermore, it is preferable that the uppermost layer of the multilayer reflective film 12, that is, the surface layer of the multilayer reflective film 12 opposite to the substrate 10, be a high refractive index layer. When the high refractive index layer and the low refractive index layer are laminated in this order from the substrate 10 side, the uppermost layer will be the low refractive index layer. However, if the low refractive index layer is the surface of the multilayer reflective film 12, the low refractive index layer will be easily oxidized, reducing the reflectivity of the surface of the multilayer reflective film. Therefore, it is preferable to form the high refractive index layer on top of the uppermost low refractive index layer. On the other hand, when the low refractive index layer and the high refractive index layer are laminated in this order from the substrate 10 side, the uppermost layer will be the high refractive index layer. In that case, the uppermost 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 pure 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 EUV light reflectivity 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 a multilayer reflective film 12 for EUV light with a wavelength of 13-14 nm, a Mo / Si multilayer film in which Mo films and Si films are alternately stacked for about 40-60 periods can be used. In addition, as multilayer reflective films used in the EUV light region, 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, Si / Ru / Mo / Ru periodic multilayer films, etc., can be used. The material of the multilayer reflective film can be selected considering the exposure wavelength.

[0034] Furthermore, examples of materials for the low refractive index layer include materials containing Ru, such as pure Ru, RuRh, RuNb, and RuMo. By including Ru in the low refractive index layer, a shallow effective reflective surface can be obtained. When the low refractive index layer contains Ru, the laminated structure of the multilayer reflective film 12 is preferably less than 40 periods, and more preferably 35 periods or less. In addition, the laminated structure is preferably 20 periods or more, and more preferably 25 periods or more.

[0035] The reflectivity of such a multilayer reflective film 12 on its own is, for example, 65% or more. The upper limit of the reflectivity 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 to satisfy Bragg's law.

[0036] The multilayer reflective film 12 can be formed by known methods. For example, the multilayer reflective film 12 can be formed by ion beam sputtering.

[0037] For example, if the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film with a thickness of approximately 3 nm is formed on the substrate 10 using an ion beam sputtering method with a Mo target. Next, a Si film with a thickness of approximately 4 nm is formed using a Si target. By repeating this operation, a multilayer reflective film 12 can be formed with 40 to 60 periods of stacked Mo / Si films. In this case, the surface layer of the multilayer reflective film 12 opposite to the substrate 10 is a Si-containing layer (Si film). The thickness of one period of Mo / Si film is 7 nm.

[0038] <Protective film> To protect the multilayer reflective film 12 from dry etching and cleaning during the manufacturing process of the reflective mask 200 described later, a protective film 14 can be formed on the multilayer reflective film 12 or in contact with its surface. The protective film 14 also has the function of protecting the multilayer reflective film 12 when correcting black defects in the transfer pattern (absorber pattern) using an electron beam (EB). By forming the protective film 14 on the multilayer reflective film 12, damage to the surface of the multilayer reflective film 12 during the manufacturing of the reflective mask 200 can be suppressed. As a result, the reflectivity characteristics of the multilayer reflective film 12 to EUV light are improved.

[0039] The protective film 14 can be deposited using known methods. Examples of methods for depositing the protective film 14 include ion beam sputtering, magnetron sputtering, reactive sputtering, vapor deposition (CVD), and vacuum deposition.

[0040] In the multilayer reflective 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 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, such as O, C, B and / or H. The SiN material layer is, for example, silicon nitride (Si x N y (x and y are integers greater than or equal to 1), and silicon oxide nitride (Si x O y N z The SiN material layer may include at least one material selected from (x, y, and z are integers of 1 or greater). The SiN material layer may include at least one material selected from, for example, SiN, Si3N4, and SiON.

[0043] The SiC material layer is a layer containing silicon (Si) and carbon (C). The SiC material layer may further contain other elements, such as O, N, B, and / or H. The SiC material layer contains, for example, silicon carbide (SiC).

[0044] The Si material layer 16 may be a SiN material layer or a SiC material layer as the uppermost high refractive index layer of the multilayer reflective film 12 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 stacked in this order from the substrate 10 side. Alternatively, when a low refractive index layer and a high refractive index layer (Si film) are stacked 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 on top of it.

[0045] In the multilayer reflective substrate 100 of this embodiment, the SiN material layer or 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 SiC material layer, it is possible to prevent the formation of silicides such as RuSi and SiO2 in the protective film 14.

[0046] When Si contained in the Si material layer 16 diffuses into the protective layer 18 due to heating during EUV exposure, the Si may bond with the 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 film 12 to EUV light will drop significantly lower than the calculated value (calculated value assuming no Si diffusion). In the multilayer reflective film substrate 100 of this embodiment, since the Si material layer 16 is a SiN material layer or a SiC material layer, the diffusion of Si into the protective layer 18 can be prevented, and thus the formation of a metal silicide (e.g., RuSi) in the protective layer 18 can be prevented. As a result, it is possible to prevent the reflectivity of the multilayer reflective film 12 to EUV light from dropping significantly lower than the calculated value.

[0047] During the annealing process when manufacturing reflective mask blanks, heating can cause oxygen (O2) from the atmosphere to permeate the protective layer 18 and bond with Si, potentially forming a layer containing SiO2. When an SiO2 layer is formed in the protective film 14 in this way, there is a problem in that the blister resistance (H2 resistance) of the reflective mask in the exposure machine deteriorates. The multilayer reflective film substrate 100 of this embodiment prevents the formation of an SiO2 layer in the protective film 14. As a result, it is possible to prevent the deterioration of the blister resistance (H2 resistance) of the reflective mask in the exposure machine.

[0048] The reason why the formation of an SiO2 layer in the protective film 14 can be prevented is as follows:

[0049] As described above, the SiN 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 relationship between the standard free energy of formation (ΔG) of these metal oxides and the standard free energy of formation (ΔG) of SiO2 is as follows. SiO2 > TiO2 > ZrO2 > Al2O3 > MgO > Y2O3

[0050] Therefore, since oxygen (O2) in the atmosphere that permeates through the protective layer 18 has a stronger tendency to combine with at least one of the above metal elements to form a metal oxide than with Si, it is thought that the formation of SiO2 can be suppressed.

[0051] Furthermore, according to the multilayer reflective film substrate 100 of this embodiment, it is possible to prevent deterioration of the durability of the reflective mask due to the exposure of chemically unstable Si on the surface layer of the multilayer reflective film 12.

[0052] The metal oxide contained in the SiN material layer or SiC material layer is preferably an oxide of at least one metal element selected from Y and Zr. This is because the extinction coefficient (k) of Y and Zr for light at a wavelength of 13.5 nm is low, at 0.01 or less, so when oxides of these metals are contained in the SiN material layer or SiC material layer, the reflectivity of the multilayer reflective film 12 to EUV light hardly decreases.

[0053] The SiN material layer 16 is preferably deposited by a PVD method (e.g., magnetron sputtering) using a SiN sintered body as a target. When producing 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 produced. By using a high-density SiN sintered body as a target, a high-quality SiN material layer with fewer defects can be formed. The SiN material layer thus formed contains the oxide of the metal added as a sintering aid.

[0054] The SiC material layer 16 is preferably deposited by a PVD method (e.g., magnetron sputtering) using a SiC sintered body as a target. When producing 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 produced. By using a high-density SiC sintered body as a target, a high-quality SiC material layer with fewer defects can be formed. The SiC material layer thus formed contains the oxide of the metal added as a sintering aid.

[0055] The SiN material layer or SiC material layer can be a single layer. Here, "single layer" means that the content (atomic %) of metal (at least one metal selected from Mg, Al, Ti, Y, and Zr) in the SiN material layer or SiC material layer is substantially constant (within ±20 atomic %, preferably within ±10 atomic %) throughout the thickness direction of the film. The SiN material layer or SiC material layer can also be a gradient film (a film in which the metal content changes continuously along the thickness direction of the film). It is preferable that the SiN material layer or SiC material layer has 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. In this case, it is possible to more effectively prevent Si from diffusing into the protective layer 18 when the substrate 100 with the multilayer reflective film is heated.

[0056] A protective layer 18 is formed on the Si material layer 16. The protective layer 18 can be deposited using known methods. Examples of methods for depositing the protective layer 18 include ion beam sputtering, magnetron sputtering, reactive sputtering, vapor deposition (CVD), and vacuum deposition.

[0057] The protective layer 18 is preferably formed from a material with different etching selectivity from the absorber film 24 described later. 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 particularly preferably a Ru-based material layer containing ruthenium (Ru). Specifically, the material of 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 from a Ta-based material and the absorber film 24 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 deposited by the same method or by different methods. For example, the multilayer reflective film 12 may be deposited by ion beam sputtering, and then the Si material layer 16 and the protective layer 18 may be deposited continuously by magnetron sputtering. Alternatively, the multilayer reflective film 12 and the Si material layer 16 may be deposited continuously by ion beam sputtering, and then the protective layer 18 may be deposited by magnetron sputtering. Alternatively, the multilayer reflective film 12 to the protective layer 18 may be deposited continuously by ion beam sputtering. When depositing these films, a single target may be used, or two or more targets may be used. Furthermore, the substrate with the multilayer reflective film 12, Si material layer 16, and protective layer 18 can be subjected to a heat treatment at 100°C to 300°C in an air atmosphere or a nitrogen atmosphere to relieve the film stress of the multilayer reflective film.

[0060] The nitrogen content in the SiN material layer is preferably 20 to 70 atoms, and more preferably 40 to 60 atoms. If the nitrogen content in the SiN material layer is less than 20 atoms, the effect of preventing Si from diffusing into the protective layer 18 is not sufficiently obtained. If the nitrogen content in the SiN material layer exceeds 70 atoms, the film density of the SiN material layer becomes low, which actually worsens durability and also reduces reflectivity.

[0061] The carbon content in the SiC material layer is preferably 20 to 80 atoms, and more preferably 40 to 70 atoms. If the carbon content in the SiC material layer is less than 20 atoms, the effect of preventing Si from diffusing into the protective layer 18 is not sufficiently obtained. If the carbon content in the SiC material layer exceeds 80 atoms, the film density of the SiC material layer becomes low, and the durability actually deteriorates.

[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 oxygen (O) content in the SiN material layer is preferably 0.5 atomic% to 20 atomic%, and more preferably 1.5 atomic% to 15 atomic%. If the O content in the SiN material layer is less than 0.5 atomic%, the formation of SiO2 cannot be suppressed, and durability decreases. If the O content in the SiN material layer exceeds 20 atomic%, the reflectivity of the multilayer reflective film decreases sharply. The oxygen (O) content in the SiC material layer is preferably 0.1 atomic% to 15 atomic%, and more preferably 0.2 atomic% to 12 atomic%. If the O content in the SiC material layer is less than 0.1 atomic%, the formation of SiO2 cannot be suppressed, and durability decreases. If the O content in the SiC material layer exceeds 15 atomic percent, the reflectivity of the multilayer reflective film decreases sharply.

[0063] Furthermore, the content of the above 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%, and more preferably 0.5 atomic% to 6.0 atomic%. If the content of the above metal in the SiN material layer is less than 0.1 atomic%, the formation of SiO2 cannot be suppressed and durability decreases. If the content of the above metal in the SiN material layer exceeds 10 atomic%, the reflectivity of the multilayer reflective film decreases sharply. The content of the above 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%, and more preferably 0.1 atomic% to 2.5 atomic%. If the content of the above metal in the SiC material layer is less than 0.05 atomic%, the formation of SiO2 cannot be suppressed and durability decreases. If the content of the above metal in the SiC material layer exceeds 3.0 atomic%, the reflectivity of the multilayer reflective film decreases sharply.

[0064] Figure 2 is a schematic cross-sectional view showing an example of a reflective mask blank 110 of this embodiment. The reflective mask blank 110 shown in Figure 2 has an absorber film 24 for absorbing EUV light on top of the protective film 14 of the multilayer reflective film substrate 100 described above. The reflective mask blank 110 may further have other thin films, such as a resist film 26, on top of the absorber film 24.

[0065] Figure 3 is a schematic cross-sectional view showing another example of the reflective mask blank 110 of this embodiment. As shown in Figure 3, the reflective mask blank 110 may have an etching mask film 28 between the absorber film 24 and the resist film 26.

[0066] <Absorbing membrane> In this embodiment, the absorber film 24 of the reflective mask blank 110 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 it may be an absorber film 24 having a phase shift function that also takes into account the phase difference of EUV light. An absorber film 24 having a phase shift function absorbs EUV light and 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, in the area where the absorber film 24 is formed, EUV light is absorbed and attenuated, while a portion of the EUV light is reflected at a level that does not adversely affect pattern transfer. In addition, in the area where the absorber film 24 is not formed (field area), EUV light is reflected by the multilayer reflective film 12 via the protective film 14. Therefore, a desired phase difference is created between the light reflected from the absorber film 24 having a phase shift function and the light reflected from the field area. The absorber film 24 having a phase shift function is preferably formed such that the phase difference between the reflected light from the absorber film 24 and the reflected light from the multilayer reflective film 12 is between 170 and 190 degrees. The light with inverted phase differences near 180 degrees interferes with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast leads to an increase in resolution, and various exposure-related margins such as exposure margin and focus margin can be increased.

[0067] The absorber film 24 may be a single layer or a multilayer film consisting of multiple layers (for example, a lower absorber film and an upper absorber film). In the case of a single layer, 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 absorber film can be appropriately set so that it acts as an anti-reflective film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. Furthermore, if a film with oxygen (O) and nitrogen (N), etc., added to the upper absorber film improves oxidation resistance, the stability over time is improved. In this way, by making the absorber film 24 a multilayer film, it becomes possible to add various functions to the absorber film 24. If the absorber film 24 has a phase shift function, the range of adjustment on the optical surface can be increased by making it a multilayer film, making it easier to obtain the desired reflectance.

[0068] The material for 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 etchable by dry etching with chlorine (Cl)-based gas and / or fluorine (F)-based gas), and has a high etching selectivity ratio with respect to the protective film 14. As materials possessing such functions, 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 compounds (alloys) thereof, can be preferably used.

[0069] The absorber film 24 can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, an absorber film 24 made of a tantalum compound can be deposited by a reactive sputtering method using an argon gas doped with oxygen or nitrogen, with a target containing tantalum and boron.

[0070] The tantalum compound for forming the absorber film 24 includes an alloy of Ta and the aforementioned metal. When the absorber film 24 is an alloy of Ta, the crystalline state of the absorber film 24 is preferably amorphous or microcrystalline 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, and the dimensional accuracy of the pattern may deteriorate. The preferred surface roughness of the absorber film 24 is 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in terms of root mean square roughness (Rms).

[0071] Examples of tantalum compounds for forming the absorber membrane 24 include compounds containing Ta and B, compounds containing Ta and N, compounds containing Ta, O and N, compounds containing Ta and B and 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, etc.

[0072] Ta has a high absorption coefficient for EUV light and can be easily dry-etched with chlorine-based or fluorine-based gases. Therefore, Ta is considered a material for absorber films 24 with excellent processability. Furthermore, by adding B, Si, and / or Ge to Ta, amorphous materials can be easily obtained. As a result, the smoothness of the absorber film 24 can be improved. In addition, by adding N and / or O to Ta, the resistance of the absorber film 24 to oxidation is improved, thereby improving its stability over time.

[0073] <Etching mask film> An etching mask film 28 may be formed on the absorber film 24. It is preferable to use a material for the etching mask film 28 that has a high etching selectivity ratio of the absorber film 24 to the etching mask film 28. The etching selectivity ratio of the absorber film 24 to the etching mask film 28 is preferably 1.5 or higher, and more preferably 3 or higher.

[0074] In this embodiment, the reflective mask blank 110 preferably has an etching mask film 28 containing chromium (Cr) on top of the absorber film 24. When etching the absorber film 24 with a fluorine-based gas, it is preferable to use chromium or a chromium compound as the material for 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 (CrO film, CrON film, CrOC film, or CrOCN film) containing chromium and oxygen.

[0075] When etching the absorber film 24 with a chlorine-based gas that is substantially free of 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 metallic silicon (metallic silicide) and metallic silicon compounds (metallic silicide compounds) that contain metal in silicon and silicon compounds. Examples of metallic 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 accurately form a pattern on the absorber film 24. Furthermore, the thickness of the etching mask film 28 is preferably 15 nm or less in order to reduce the thickness of the resist film 26.

[0077] <Conductive film on the back surface> A back surface conductive film 22 for electrostatic chucks may be formed on the back surface of the substrate 10 (the side opposite to the side on which the multilayer reflective film 12 is formed). For electrostatic chucks, the required sheet resistance of the back surface conductive film 22 is usually 100 Ω / □ (Ω / square) or less. The back surface 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 of the back surface conductive film 22 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back surface conductive film 22 is preferably a Cr compound containing Cr and at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Furthermore, 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 the electrostatic chuck, but is, for example, 10 nm to 200 nm.

[0079] <Reflective mask> The reflective mask 200 of this embodiment can be manufactured using the reflective mask blank 110 of this embodiment. An example of a method for manufacturing a reflective mask will be described below.

[0080] Figures 4A-E are schematic diagrams showing an example of a manufacturing method for the reflective mask 200.

[0081] As shown in Figures 4A-E, 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 (Si material layer 16 and protective layer 18) formed on the multilayer reflective film 12, and an absorber film 24 formed on the protective film 14 (Figure 4A). Next, a resist film 26 is formed on the absorber film 24 (Figure 4B). A pattern is drawn on the resist film 26 using an electron beam lithography apparatus, and then a resist pattern 26a is formed by going through a development and rinsing process (Figure 4C).

[0082] The absorber film 24 is dry-etched using the resist pattern 26a as a mask. This etches the parts of the absorber film 24 that are not covered by the resist pattern 26a, forming the absorber pattern 24a (Figure 4D).

[0083] For example, a fluorine-based gas and / or a chlorine-based gas can be used as the etching gas for the absorber film 24. Examples of fluorine-based gases include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2. Examples of chlorine-based gases include Cl2, SiCl4, CHCl3, CCl4, and BCl3. Alternatively, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 in a predetermined ratio can be used. These etching gases may further contain inert gases such as He and / or Ar as needed.

[0084] After the absorbent pattern 24a is formed, the resist pattern 26a is removed with a resist stripping solution. After removing the resist pattern 26a, the reflective mask 200 of this embodiment is obtained by going through a wet cleaning process using an acidic or alkaline aqueous solution (Figure 4E).

[0085] Furthermore, when using a reflective mask blank 110 in which an etching mask film 28 is formed on an absorber film 24, an additional step is added: first, 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 obtained in this manner 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] The region 30 in which the multilayer reflective film 12 (including the protective film 14) is exposed has the function of reflecting EUV light. The region 32 in which the multilayer reflective film 12 (including the protective film 14) is covered by 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 such that the reflectance is, for example, 2.5% or less can be made thinner than in the conventional method, so that a finer pattern can be transferred to the object to be transferred.

[0088] <Manufacturing method for semiconductor devices> A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask 200 of this embodiment. This transfer pattern has the shape of the pattern transferred from the reflective mask 200. By forming a transfer pattern on a semiconductor substrate with the reflective mask 200, a semiconductor device can be manufactured.

[0089] Using Figure 5, we will explain a method for transferring a pattern onto a resist-coated semiconductor substrate 56 using EUV light.

[0090] Figure 5 shows the pattern transfer apparatus 50. The pattern transfer apparatus 50 includes a laser plasma X-ray source 52, a reflective mask 200, and a reduction optical system 54, etc. An X-ray reflective mirror is used as the reduction optical system 54.

[0091] The pattern reflected by the reflective mask 200 is typically reduced to about 1 / 4 of its original size by the reduction optical system 54. For example, a wavelength band of 13-14 nm is used as the exposure wavelength, and the optical path is pre-set to be in a vacuum. Under these conditions, EUV light generated by the laser plasma X-ray source 52 is incident on the reflective mask 200. The light reflected by the reflective mask 200 is transferred onto the resist-coated semiconductor substrate 56 via the reduction optical system 54.

[0092] Light reflected by the reflective mask 200 enters the reduction optical system 54. The light entering the reduction optical system 54 forms a transfer pattern on the 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, a predetermined wiring pattern can be formed on the semiconductor substrate. A semiconductor device is manufactured through these steps and other necessary steps. [Examples]

[0093] Examples, reference examples, and comparative examples will be described below with reference to the drawings.

[0094] (Fabrication of a multilayer reflective substrate 100) First, a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) substrate 10 with a first main surface and a second main surface polished was prepared. This substrate 10 is made of low thermal expansion glass (SiO2-TiO2 glass). The main surface of the substrate 10 was polished by a rough polishing process, a precision polishing process, a localized 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. To make the multilayer reflective film 12 formed on the substrate 10 suitable for EUV light with a wavelength of 13.5 nm, a periodic multilayer reflective film 12 made of Mo and Si was formed. The multilayer reflective film 12 was formed by alternately stacking Mo films and Si films on the substrate 10 using an ion beam sputtering method with a Mo target and a Si target and krypton (Kr) as the process gas. First, a Si film was deposited to a thickness of 4.2 nm, and then a Mo film was deposited to a thickness of 2.8 nm. This constituted one period, and 40 periods were stacked in the same manner 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 deposited 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. At least one metal oxide selected from magnesium (Mg), aluminum (Al), yttrium (Y), and zirconium (Zr) was added as a sintering aid to the SiC sintered body or SiN sintered body used as the target. On the other hand, 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, pure Si was used as the target to form the Si material layer.

[0097] Next, a RuNb film was formed on the Si material layer 16 as a protective layer 18. The protective layer 18 was formed to a thickness of 3.5 nm by magnetron sputtering using a RuNb target in an Ar gas atmosphere.

[0098] (Evaluation of the multilayer reflective substrate 100) Using the multilayer reflective film substrates 100 of the examples, reference examples, and comparative examples prepared above, we confirmed whether there was a change in reflectivity after heating the multilayer reflective film substrates 100, and whether or not an SiO2 layer was formed in the protective film 14.

[0099] Specifically, first, the reflectance of the multilayer reflective film substrate 100 of the examples, reference examples, and comparative examples to EUV light was measured. Next, the multilayer reflective film substrate 100 was heated in an atmospheric environment at 200°C for 10 minutes. After heating the multilayer reflective film substrate 100, the reflectance of the multilayer reflective film substrate 100 to EUV light was measured. The change in reflectance of the multilayer reflective film substrate 100 was evaluated by subtracting the reflectance of the multilayer reflective film substrate 100 before heating (%) from the reflectance of the multilayer reflective film substrate 100 after heating (%).

[0100] Furthermore, after heating the multilayer reflective film substrate 100 at 200°C for 10 minutes, the cross-section of the protective film 14 was observed with an electron microscope to confirm whether or not an SiO2 layer had formed in the protective film 14.

[0101] Table 1 below shows the results of confirming whether or not there was a change in the reflectance of the multilayer reflective film substrate 100, and whether or not an SiO2 layer was formed in the protective film 14. Table 1 also shows the film composition and film thickness of the Si material layer 16 in the examples, reference examples, and comparative examples after heating the multilayer reflective film 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 spectrometry). The composition of the RuNb film was measured by X-ray photoelectron spectroscopy (XPS) and found to be Ru:Nb = 80:20.

[0102] [Table 1]

[0103] As can be seen from the results shown in Table 1, in the multilayer reflective substrates 100 of Examples 1-8 and Reference Examples 1 and 2, the reflectivity of the multilayer reflective substrate 100 to EUV light remained almost unchanged before and after heating at 200°C. In particular, the change in reflectivity in Examples 3 and 4 was small. In Examples 1-8 and Reference Examples 1 and 2, since the Si material layer 16 is a SiN layer or a SiC layer, the diffusion of Si from the Si material layer 16 to the protective layer 18 is suppressed, and it is presumed that this is because the formation of metal silicide (RuSi) in the protective layer 18 is suppressed.

[0104] On the other hand, in Comparative Example 1, the reflectivity of the multilayer reflective substrate 100 to EUV light changed significantly before and after heating at 200°C. In Comparative Example 1, it is presumed that this was due to the diffusion of Si from the Si material layer 16 to the protective layer 18, resulting in the formation of metal silicide (RuSi) in the protective layer 18.

[0105] Furthermore, in the multilayer reflective substrates 100 of Examples 1 to 8, no SiO2 layer was generated in the protective film 14 after heating at 200°C. It is presumed that this is because, in Examples 1 to 8, the addition of metal oxide to the Si material layer 16 suppressed the generation of SiO2 in the protective film 14. On the other hand, in the multilayer reflective substrates 100 of Reference Examples 1 and 2 and Comparative Example 1, an SiO2 layer was generated in the protective film 14 after heating at 200°C. It is presumed that this is because, in Reference Examples 1 and 2 and Comparative Example 1, no metal oxide was added to the Si material layer 16, resulting in the generation of SiO2 in the protective film 14. [Explanation of symbols]

[0106] 10 circuit boards 12 Multilayer reflective coating 14 Protective film 16 Si material layer 18 Protective layer 22 Conductive film on the back surface 24a Absorber pattern 24 Absorbent membrane 26a Resist Pattern 26 Resist film 28 Etching mask film 50 Pattern Transfer Device 100 Multilayer reflective substrates 110 Reflective Mask Blank 200 Reflective Masks

Claims

1. A multilayer reflective 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 the 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). A multilayer reflective substrate characterized in that the 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).

2. The substrate with a multilayer reflective film according to claim 1, characterized in that the metal is at least one selected from Y and Zr.

3. The substrate with a multilayer reflective film according to claim 1 or 2, characterized in that the protective film includes a Ru-based material layer on the SiN material layer or SiC material layer.

4. A reflective mask blank characterized in that an absorbent film is provided on the protective film of a multilayer reflective film substrate according to any one of claims 1 to 3.

5. A reflective mask characterized by comprising an absorbent pattern obtained by patterning the absorbent membrane of the reflective mask blank described in claim 4.

6. A method for manufacturing a semiconductor device, characterized by comprising the step of performing a lithography process using an exposure apparatus with a reflective mask as described in claim 5 to form a transfer pattern on a transfer object.

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