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

Abstract

The present invention provides a multilayer reflective film-equipped substrate, a reflective mask blank, a reflective mask, and a method for producing a semiconductor device, the multilayer reflective film-equipped substrate having high tolerance for etching gas used for etching of an absorber film and / or an etching mask film, and capable of suppressing occurrence of blisters.　A multilayer reflective film-equipped substrate 100 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 contains at least one additional element selected from ruthenium (Ru), rhodium (Rh), titanium (Ti), zirconium (Zr), yttrium (Y), niobium (Nb), vanadium (V), and hafnium (Hf).

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 (hereinafter referred to as EUV) lithography, which is 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 and serving as an absorber pattern for absorbing exposure light. The light incident on the reflective mask mounted on an exposure machine for performing pattern transfer on a semiconductor substrate is absorbed at the part with the absorber pattern and reflected by the multilayer reflective film at 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] As the multilayer reflective film, generally, a multilayer film in which elements with different refractive indexes 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] As a reflective mask used in EUV lithography, for example, there is a reflective mask described in Patent Document 1. Patent Document 1 describes a reflective photomask having a substrate, a reflective layer composed of a multilayer film formed on the substrate and having two different films alternately laminated, a buffer layer composed of a ruthenium film formed on the reflective layer, and an absorber pattern composed of a material capable of absorbing soft X-rays formed on the buffer layer with a predetermined pattern shape. The buffer layer described in Patent Document 1 is generally also called a protective film.

[0007] Patent Document 2 describes a substrate with a multilayer reflective film that reflects exposure light on the substrate. Further, Patent Document 2 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 formed by laminating a reflectance reduction suppression layer, a blocking layer, and an etching stopper layer in this order. Also, Patent Document 2 describes that the etching stopper layer is made of ruthenium (Ru) or an alloy thereof, and specific examples of the ruthenium alloy include ruthenium niobium (RuNb) alloy, ruthenium zirconium (RuZr) alloy, ruthenium rhodium (RuRh) alloy, ruthenium cobalt (RuCo) alloy, and ruthenium rhenium (RuRe) alloy.

[0008] Patent Documents 3 and 4 describe a substrate with a multilayer reflective film 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 Documents 3 and 4 describe that the surface layer on the side of the multilayer reflective film opposite to the substrate contains Si.

[0009] Patent Document 3 describes that a block layer for preventing the transition of Si to the Ru-based protective film is provided between the multilayer reflective film and the Ru-based protective film. Patent Document 3 also describes that the constituent materials of the Ru-based protective film can include Ru and its alloy materials, and among the Ru alloys, Ru compounds having Ru and at least one metal element selected from the group consisting of Nb, Zr, Rh, Ti, Co, and Re are preferred.

[0010] Patent Document 4 describes that the Ru-based protective film contains a Ru compound containing Ru and Ti, and the Ru compound contains more Ru than the stoichiometric composition of RuTi.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Disclosure of the Invention

[0012] In the manufacturing process of a reflective mask, when forming an absorber pattern, the absorber film is processed by etching through a resist pattern or an etching mask pattern. In order to process the absorber film into the designed shape, it is necessary to perform some over-etching on the absorber film. During over-etching, the multilayer reflective film under the absorber film is also damaged by etching. To prevent the multilayer reflective film from being damaged by etching, a protective film is provided between the absorber film and the multilayer reflective film. Therefore, the protective film is required to have high resistance to the etching gas used for etching the absorber film.

[0013] As a material for a protective film having high resistance to an etching gas of an absorber film, for example, Ru or RuNb is used. When the etching mask film formed on the absorber film is a Cr-based material, a mixed gas of chlorine gas and oxygen gas is used as the etching gas to remove the etching mask film. The protective films of Ru and RuNb have low resistance to a mixed gas containing oxygen gas. Therefore, when the etching mask film is removed, the multilayer reflective film formed under the protective film may be damaged. In addition, the protective film damaged when the etching mask film is removed may not have sufficient resistance in the subsequent absorber pattern correction process.

[0014] Also, in EUV lithography, it is known that exposure contamination such as carbon film deposition on a reflective mask occurs due to EUV exposure. In order to suppress this, in recent years, a technique of introducing hydrogen gas into the atmosphere during exposure has been adopted. The present inventors have discovered that when hydrogen gas is introduced into the atmosphere during exposure, a phenomenon occurs in which the absorber film floats and peels off from the surface of the protective film. Furthermore, it has been discovered that a phenomenon occurs in which the protective film floats and peels off from the surface of the multilayer reflective film (hereinafter, such a film peeling phenomenon is referred to as "blister"). In particular, when the absorber film is a material containing Ta, it has been discovered that such a phenomenon occurs remarkably because Ta easily adsorbs hydrogen. Therefore, it is also required to solve the problem of blister in the protective film.

[0015] Therefore, an object of the present invention is 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 have high resistance to an etching gas used for etching an absorber film and / or an etching mask film and can suppress the occurrence of blisters.

[0016] To solve the above problems, the present invention has the following configuration.

[0017] (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 contains ruthenium (Ru), rhodium (Rh), and at least one additive element selected from titanium (Ti), zirconium (Zr), yttrium (Y), niobium (Nb), vanadium (V), and hafnium (Hf). The substrate with a multilayer reflective film is characterized by this.

[0018] (Configuration 2) The content of the rhodium (Rh) is 15 atomic % or more and 50 atomic % or less. The substrate with a multilayer reflective film according to Configuration 1 is characterized by this.

[0019] (Configuration 3) The content of the additive element is 1 atomic % or more and 20 atomic % or less. The substrate with a multilayer reflective film according to Configuration 1 or Configuration 2 is characterized by this.

[0020] (Configuration 4) The additive element is titanium (Ti). The content of the Ti is 1 atomic % or more and 10 atomic % or less. The substrate with a multilayer reflective film according to Configuration 3 is characterized by this.

[0021] (Configuration 5) The additive element is zirconium (Zr). The content of the Zr is 1 atomic % or more and 10 atomic % or less. The substrate with a multilayer reflective film according to Configuration 3 is characterized by this.

[0022] (Configuration 6) The protective film contains a Si material layer containing silicon (Si) on the side in contact with the multilayer reflective film. The substrate with a multilayer reflective film according to any one of Configurations 1 to 5 is characterized by this.

[0023] (Configuration 7) A reflective mask blank, characterized by comprising an absorber film on the protective film of the substrate with a multilayer reflective film according to any one of Configurations 1 to 6.

[0024] (Configuration 8) A reflective mask comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to Configuration 7.

[0025] (Configuration 9) A method for manufacturing a semiconductor device, comprising a step of performing a lithography process using an exposure apparatus with the reflective mask according to Configuration 8 and forming a transfer pattern on a transfer target.

[0026] 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 have high resistance to an etching gas used for etching an absorber film and / or an etching mask film and can suppress the generation of blisters.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A-E

Figure 6

Embodiments for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Note that the following embodiments are for specifically explaining the present invention and do not limit the present invention within its scope.

[0029] FIG. 1 is a schematic cross-sectional view showing an example of a substrate 100 with a multilayer reflective film according to this 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 on which the multilayer reflective film 12 is formed).

[0030] In this specification, "on" a substrate or a film includes not only the case of contacting the upper surface of the substrate or the film but also the case of not contacting the upper surface of the substrate or the film. That is, "on" a substrate or a film includes the case where a new film is formed above the substrate or the film, the case where another film is interposed between the substrate or the film, and the like. Also, "on" does not necessarily mean the upper side in the vertical direction. "On" only indicates the relative positional relationship of a substrate, a film, etc.

[0031] <Substrate> In order to prevent distortion of a transfer pattern due to heat during exposure with EUV light, the substrate 10 preferably has a low coefficient of thermal expansion within the range of 0 ± 5 ppb / °C. As a material having a low coefficient of thermal expansion in this range, for example, SiO 2 -TiO 2 -based glass, multi-component glass ceramics, etc. can be used.

[0032] The main surface of the substrate 10 on which the transfer pattern (absorber pattern described later) is formed is preferably processed to enhance flatness. By enhancing 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, in the region of 132 mm × 132 mm of the main surface of the substrate 10 on which the transfer pattern is formed, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Further, the main surface (back surface) on the side opposite to the side on which the transfer pattern is formed is the surface fixed to the exposure apparatus by an electrostatic chuck. In the region of 142 mm × 142 mm of the back surface, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. Note that in this specification, the flatness is a value representing the warpage (amount of deformation) of the surface indicated by TIR (Total Indicated Reading). Specifically, the flatness is the absolute value of the height difference between the highest position of the substrate surface above the focal plane and the lowest position of the substrate surface below the focal plane, with the plane determined by the least squares method with the substrate surface as a reference being the focal plane.

[0033] 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). Note that the surface roughness can be measured with an atomic force microscope.

[0034] The substrate 10 preferably has high rigidity in order to prevent deformation due to the film stress of the film (such as the multilayer reflective film 12) formed thereon. In particular, it preferably has a high Young's modulus of 65 GPa or more.

[0035] <multilayer reflective film> The multilayer reflective film 12 has a structure in which a plurality of layers mainly composed of elements with different refractive indices are periodically laminated. Generally, the multilayer reflective film 12 is composed of a multilayer film in which thin films of light elements or their compounds (high refractive index layers) that are high refractive index materials and thin films of heavy elements or their compounds (low refractive index layers) that are low refractive index materials are alternately laminated about 40 to 60 cycles. In order to form the multilayer reflective film 12, a plurality of cycles of high refractive index layers and low refractive index layers may be laminated in this order from the substrate 10 side. In this case, one (high refractive index layer / low refractive index layer) laminated structure becomes one cycle.

[0036] Note that the uppermost layer of the multilayer reflective film 12, that is, the surface layer on the side opposite to the substrate 10 of the multilayer reflective film 12, is preferably 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 becomes a low refractive index layer. However, when the low refractive index layer is the surface of the multilayer reflective film 12, the reflectance of the surface of the multilayer reflective film decreases because the low refractive index layer is easily oxidized. In that case, it is preferable to form a high refractive index layer on the 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 becomes a high refractive index layer. In that case, the high refractive index layer of the uppermost layer becomes the surface of the multilayer reflective film 12.

[0037] In this embodiment, the high refractive index layer may be a layer containing Si. The high refractive index layer may contain Si alone or may contain a Si compound. The Si compound may contain at least one element selected from the group consisting of Si and B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film excellent in reflectance of EUV light can be obtained.

[0038] 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.

[0039] For example, as the multilayer reflective film 12 for EUV light with a wavelength of 13 to 14 nm, preferably, a Mo / Si multilayer film formed by alternately laminating Mo films and Si films about 40 to 60 cycles can be used. In addition, as the multilayer reflective film used in the EUV light region, for example, Ru / Si periodic multilayer film, Mo / Be periodic multilayer film, Mo compound / Si compound periodic multilayer film, Si / Nb periodic multilayer film, Si / Mo / Ru periodic multilayer film, Si / Mo / Ru / Mo periodic multilayer film, and Si / Ru / Mo / Ru periodic multilayer film, etc. can be used. Considering the exposure wavelength, the material of the multilayer reflective film can be selected.

[0040] The reflectivity of such a multilayer reflective film 12 alone is, for example, 65% or more. The upper limit of the reflectivity of the multilayer reflective film 12 is, for example, 73%. Note that the thickness and period of the layers included in the multilayer reflective film 12 can be selected to satisfy Bragg's law.

[0041] The multilayer reflective film 12 can be formed by a known method. The multilayer reflective film 12 can be formed, for example, by an ion beam sputtering method.

[0042] For example, when the multilayer reflective film 12 is a Mo / Si multilayer film, by an ion beam sputtering method, a Mo film with a thickness of about 3 nm is formed on the substrate 10 using a Mo target. Next, a Si film with a thickness of about 4 nm is formed using a Si target. By repeating such operations, a multilayer reflective film 12 in which Mo / Si films are laminated 40 to 60 cycles can be formed. At this time, the surface layer on the side opposite to the substrate 10 of the multilayer reflective film 12 is a layer containing Si (Si film). The thickness of one cycle of the Mo / Si film is 7 nm.

[0043] <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 described below, 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. Further, the protective film 14 also has a function of protecting the multilayer reflective film 12 when correcting black defects in a transfer 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 manufacture of the reflective mask 200 can be suppressed. As a result, the reflectance characteristics of the multilayer reflective film 12 with respect to EUV light become good.

[0044] The protective film 14 can be formed by using a known method. Examples of the film formation method of the protective film 14 include an ion beam sputtering method, a magnetron sputtering method, a reactive sputtering method, a chemical vapor deposition method (CVD), and a vacuum evaporation method. The protective film 14 may be continuously formed by an ion beam sputtering method after the formation of the multilayer reflective film 12.

[0045] In the substrate 100 with a multilayer reflective film of the present embodiment, the protective film 14 contains ruthenium (Ru), rhodium (Rh), and at least one additive element selected from titanium (Ti), zirconium (Zr), yttrium (Y), niobium (Nb), vanadium (V), and hafnium (Hf).

[0046] When the protective film 14 contains ruthenium (Ru) and rhodium (Rh), the etching resistance of the protective film 14 to a mixed gas of a chlorine-based gas and an oxygen gas, the etching resistance to a chlorine-based gas, the etching resistance to a fluorine-based gas, and the cleaning resistance by sulfuric acid peroxide (SPM) are improved. If the content of Rh in the protective film 14 is too small, the effect of the addition cannot be obtained. If the content of Rh in the protective film 14 is too large, the attenuation coefficient k of the protective film 14 with respect to EUV light becomes high, so the reflectance of the reflective mask 200 decreases. Therefore, the content of Rh in the protective film 14 is preferably 15 atomic% or more and 50 atomic% or less, and more preferably 20 atomic% or more and 40 atomic% or less.

[0047] By including ruthenium (Ru), rhodium (Rh), and at least one additive element selected from titanium (Ti), zirconium (Zr), yttrium (Y), niobium (Nb), vanadium (V), and hafnium (Hf) in the protective film 14, the adhesion between the protective film 14 and the multilayer reflective film 12 is improved. Therefore, it is possible to suppress the generation of blisters between the protective film 14 and the multilayer reflective film 12. Also, since the adhesion between the protective film 14 and the absorber film 24 described later is improved, it is possible to prevent the generation of blisters between the protective film 14 and the multilayer reflective film 12. To obtain such an effect, the content of the additive element in the protective film 14 is preferably 1 atomic % or more and 20 atomic % or less.

[0048] When the protective film 14 contains titanium (Ti) as an additive element (for example, in the case of a RuRhTi film), the content of Ti in the protective film 14 is preferably 1 atomic % or more, and more preferably 2 atomic % or more. Also, the content of Ti is preferably 10 atomic % or less, and more preferably 7 atomic % or less.

[0049] When the protective film 14 contains zirconium (Zr) as an additive element (for example, in the case of a RuRhZr film), the content of Zr in the protective film 14 is preferably 1 atomic % or more, and more preferably 2 atomic % or more. Also, the content of Zr is preferably 10 atomic % or less, and more preferably 7 atomic % or less.

[0050] When the protective film 14 contains yttrium (Y) as an additive element (for example, in the case of a RuRhY film), the content of Y in the protective film 14 is preferably 1 atomic % or more, and more preferably 2 atomic % or more. Also, the content of Y is preferably 10 atomic % or less, and more preferably 7 atomic % or less.

[0051] When the protective film 14 contains niobium (Nb) as an additive element (for example, in the case of a RuRhNb film), the content of Nb in the protective film 14 is preferably 1 atomic % or more, more preferably 2 atomic % or more. Also, the content of Nb is preferably 20 atomic % or less, more preferably 15 atomic % or less.

[0052] When the protective film 14 contains vanadium (V) as an additive element (for example, in the case of a RuRhV film), the content of V in the protective film 14 is preferably 1 atomic % or more, more preferably 2 atomic % or more. Also, the content of V is preferably 10 atomic % or less, more preferably 7 atomic % or less.

[0053] When the protective film 14 contains hafnium (Hf) as an additive element (for example, in the case of a RuRhHf film), the content of Hf in the protective film 14 is preferably 1 atomic % or more, more preferably 2 atomic % or more. Also, the content of Hf is preferably 7 atomic % or less, more preferably 5 atomic % or less.

[0054] FIG. 2 is a cross-sectional schematic view showing another example of the substrate 100 with a multilayer reflective film according to the present embodiment. As shown in FIG. 2, the protective film 14 may include a Si material layer 16 containing silicon (Si) on the side in contact with the multilayer reflective film 12. That is, the protective film 14 may include a Si material layer 16 on the side in contact with the multilayer reflective film 12 and a RuRh-based layer 18 formed on the Si material layer 16. The RuRh-based layer 18, similar to the protective film 14 described above, is a layer containing ruthenium (Ru), rhodium (Rh), and at least one additive element selected from titanium (Ti), zirconium (Zr), yttrium (Y), niobium (Nb), vanadium (V), and hafnium (Hf). The Si material layer 16 is a layer made of a material containing silicon (Si). The Si material layer 16 is, for example, silicon (Si), silicon oxide (SiO, SiO 2 , Si 3 O 2 etc. of Si x O y (x, y are integers of 1 or more), silicon nitride (SiN, Si3 N 4 Si such as x N y (where x and y are integers of 1 or more), and silicon oxynitride (Si such as SiON x O y N z (where x, y, and z are integers of 1 or more)), and includes at least one material selected therefrom. The Si material layer 16 may be a Si film which is a high refractive index layer provided as the uppermost layer of the multilayer reflective film 12 when the multilayer reflective film 12 is a Mo / Si multilayer film and the Mo film and the Si film are laminated in this order from the substrate 10 side.

[0055] In the substrate 100 with the multilayer reflective film of the present embodiment, the Si material layer 16 may contain a first noble gas element, and the RuRh-based layer 18 may contain a second noble gas element different from the first noble gas element. Each of the first noble gas element and the second noble gas element may be one kind of noble gas element or two or more kinds of noble gas elements. That the first noble gas element and the second noble gas element are "different" means that at least one kind of noble gas element contained in the first noble gas element is different from at least one kind of noble gas element contained in the second noble gas element.

[0056] Each of the first noble gas element and the second noble gas element contains at least one kind of noble gas element selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). The first noble gas element and the second noble gas element preferably contain at least one kind of noble gas element selected from argon (Ar), krypton (Kr), and xenon (Xe).

[0057] The second noble gas element may have an atomic weight smaller than that of the first noble gas element. "Smaller" as used herein means that the atomic weight of at least one kind of noble gas element contained in the second noble gas element is smaller than the atomic weight of at least one kind of noble gas element contained in the first noble gas element. For example, when the first noble gas element is krypton (Kr) and the second noble gas element is argon (Ar), such conditions are satisfied.

[0058] Further, the second noble gas element may have a larger atomic weight than the first noble gas element. Here, "larger" means that the atomic weight of at least one noble gas element contained in the second noble gas element is larger than the atomic weight of at least one noble gas element contained in the first noble gas element. For example, when the first noble gas element is argon (Ar) or krypton (Kr) and the second noble gas element is xenon (Xe), such conditions are satisfied. Also, when the first noble gas element is argon (Ar) and krypton (Kr) and the second noble gas element is argon (Ar) and xenon (Xe), such conditions are satisfied.

[0059] The multilayer reflective film 12, the Si material layer 16, and the RuRh-based layer 18 may be formed by the same method or by different methods. For example, after continuously forming the multilayer reflective film 12 and the Si material layer 16 by the ion beam sputtering method, the RuRh-based layer 18 may be formed by the magnetron sputtering method. Also, the multilayer reflective film 12 to the RuRh-based layer 18 may be continuously formed by the ion beam sputtering method.

[0060] The protective film 14 containing ruthenium (Ru), rhodium (Rh), and an additive element (when the protective film 14 includes the Si material layer 16 and the RuRh-based layer 18, the RuRh-based layer 18) may be a single layer, a multilayer film, or a gradient film. When the protective film 14 (RuRh-based layer 18) is a multilayer film, an additive element layer and a RuRh layer may be alternately laminated to form a multilayer film of 4 to 10 layers. In this case, it is preferable that the lowermost layer is an additive element layer and the uppermost layer is a RuRh layer. Also, when the protective film 14 (RuRh-based layer 18) is a gradient film, it is preferable to have a configuration in which the content of the additive element is high on the side of the multilayer reflective film 12 of the protective film 14 (RuRh-based layer 18) and the content of the additive element is low on the side of the absorber film 24. Also, when the protective film 14 (RuRh-based layer 18) is a gradient film, it is preferable to have a configuration in which the content of Rh is low on the side of the multilayer reflective film 12 of the protective film 14 (RuRh-based layer 18) and the content of Rh is high on the side of the absorber film 24.

[0061] FIG. 3 is a schematic cross-sectional view showing an example of the reflective mask blank 110 of the present embodiment. The reflective mask blank 110 shown in FIG. 3 has an absorber film 24 for absorbing EUV light on the protective film 14 of the above-described substrate 100 with a multilayer reflective film. Note that the reflective mask blank 110 may further have other thin films such as a resist film 26 on the absorber film 24.

[0062] FIG. 4 is a schematic cross-sectional view showing another example of the reflective mask blank 110 of the present embodiment. As shown in FIG. 4, the reflective mask blank 110 may have an etching mask film 28 between the absorber film 24 and the resist film 26.

[0063] <Absorber film> The absorber film 24 of the reflective mask blank 110 of the present 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 for the purpose of absorbing EUV light, or may be an absorber film 24 having a phase shift function considering the phase difference of EUV light. The absorber film 24 having a phase shift function is one that absorbs EUV light and reflects a part thereof to shift the phase. That is, in the reflective mask 200 in which the absorber film 24 having a phase shift function is patterned, in the portion where the absorber film 24 is formed, while absorbing EUV light and reducing the light intensity, a part of the light is reflected at a level that does not adversely affect pattern transfer. Further, in the region (field portion) where the absorber film 24 is not formed, EUV light is reflected by the multilayer reflective film 12 through the protective film 14. Therefore, a desired phase difference occurs between the reflected light from the absorber film 24 having a phase shift function and the reflected light from the field portion. 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 170 degrees to 190 degrees. By the interference of the light with the inverted phase difference in the vicinity of 180 degrees with each other at the pattern edge portion, the image contrast of the projection optical image is improved. Along with the improvement of the image contrast, the resolution is increased, and various margins related to exposure such as the exposure amount margin and the focus margin can be increased.

[0064] The absorber film 24 may be a single-layer film or a multilayer film composed of a plurality of films (for example, a lower absorber film and an upper absorber film). In the case of a single-layer film, the number of manufacturing steps during mask blank production can be reduced, thus improving production efficiency. In the case of a multilayer film, the optical constants and film thickness can be appropriately set so that the upper absorber film serves as an antireflection film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. Also, when a film in which oxygen (O), nitrogen (N), etc. that improve oxidation resistance are added to the upper absorber film is used, the stability over time is improved. Thus, by making the absorber film 24 a multilayer film, various functions can be added to the absorber film 24. When the absorber film 24 has a phase shift function, making it a multilayer film can increase the adjustment range on the optical surface, making it easier to obtain a desired reflectance.

[0065] As the material of the absorber film 24, as long as it has a function of absorbing EUV light, can be processed by etching or the like (preferably, can be etched by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity with respect to the protective film 14 (RuRh-based layer 18), it is not particularly limited. As materials having 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 thereof can be preferably used.

[0066] The absorber film 24 can be formed by a magnetron sputtering method such as a DC sputtering method or an RF sputtering method. For example, the absorber film 24 made of a tantalum compound can be formed by a reactive sputtering method using a target containing tantalum and boron and an argon gas added with oxygen or nitrogen.

[0067] The tantalum compound for forming the absorber film 24 includes an alloy of Ta and the above-mentioned metal. When the absorber film 24 is an alloy of Ta, from the viewpoints of smoothness and flatness, the crystal state of the absorber film 24 is preferably an amorphous or microcrystalline structure. 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 a root mean square roughness (Rms) of 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less.

[0068] Examples of the tantalum compound 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, etc.

[0069] Ta is a material with a large absorption coefficient for EUV light and can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, it can be said that Ta is a material for the absorber film 24 with excellent processability. 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. Also, by adding N and / or O to Ta, the resistance of the absorber film 24 to oxidation can be improved, and thus the stability over time can be improved.

[0070] <Back surface conductive film> Substrate 10On the second main surface (the main surface opposite to the side on which the multilayer reflective film 12 is formed) of the reflective mask blank 110, a back surface conductive film 22 for an electrostatic chuck is formed. As the electrostatic chuck, the sheet resistance required for 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 at least one selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of the Cr compound include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Further, 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 the Ta compound include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHO, TaHN, TaHON 、T aHCON, TaSi, TaSiO, TaSiN, TaSiONCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON, etc. can be mentioned.

[0071] The film 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 usually 10 nm to 200 nm. Further, the back surface conductive film 22 preferably has a function of adjusting the stress on the second main surface side of the reflective mask blank 110. That is, the back surface conductive film 22 preferably has a function of adjusting so that the reflective mask blank 110 becomes flat by balancing the stress generated by forming a thin film on the first main surface and the stress on the second main surface.

[0072] <Etching mask film> An etching mask film 28 may be formed on the absorber film 24. As the material of the etching mask film 28, it is preferable to use a material that provides a high etching selectivity of the absorber film 24 with respect to the etching mask film 28. The etching selectivity of the absorber film 24 with respect to the etching mask film 28 is preferably 1.5 or more, and more preferably 3 or more.

[0073] The reflective mask blank 110 of the present embodiment preferably includes an etching mask film 28 containing chromium (Cr) on 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 of the etching mask film 28. Examples of the chromium compound 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.

[0074] By configuring the protective film 14 to include ruthenium (Ru), rhodium (Rh), and the additive element described above, damage to the protective film 14 can be suppressed when removing the etching mask film 28 containing chromium (Cr) by dry etching using a mixed gas of a chlorine-based gas and an oxygen gas.

[0075] When etching the absorber film 24 with a chlorine-based gas substantially free of oxygen, it is preferable to use silicon or a silicon compound as the material of the etching mask film 28. Examples of the silicon compound include materials containing Si and at least one element selected from N, O, C, and H, and silicon Or Silicon compounds include metal silicon (metal silicide) containing a metal, and metal silicon compounds (metal silicide compounds). Examples of the metal silicon compound include materials containing a metal, Si, and at least one element selected from N, O, C, and H.

[0076] By configuring the protective film 14 to contain the aforementioned ruthenium (Ru), rhodium (Rh), and additive elements, damage to the protective film 14 can be suppressed when removing the silicon-containing etching mask film 28 by dry etching using a fluorine-based gas.

[0077] The film 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. Also, the film thickness of the etching mask film 28 is preferably 15 nm or less in order to make the film thickness of the resist film 26 thinner.

[0078] <Reflective mask> Using the reflective mask blank 110 of the present embodiment, the reflective mask 200 of the present embodiment can be manufactured. Hereinafter, an example of a method for manufacturing a reflective mask will be described.

[0079] Figs. 5A - E are schematic diagrams showing an example of a method for manufacturing a reflective mask 200.

[0080] As shown in Fig. 5A, first, a reflective mask blank 110 having a substrate 10, a multilayer reflective film 12 formed on the substrate 10, a protective film 14 formed on the multilayer reflective film 12, and an absorber film 24 formed on the protective film 14 is prepared (Fig. 5A). Next, a resist film 26 is formed on the absorber film 24 (Fig. 5B). A pattern is drawn on the resist film 26 by an electron beam lithography apparatus, and through a development and rinsing process, a resist pattern 26a is formed (Fig. 5C).

[0081] Using the resist pattern 26a as a mask, the absorber film 24 is dry-etched. As a result, the portion of the absorber film 24 not covered by the resist pattern 26a is etched, and an absorber pattern 24a is formed (Fig. 5D).

[0082] 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 、CHF3 , C2F 6 , C 3 F 6 , C 4 F 6 , C 4 F 8 , CH 2 F 2 , CH 3 , CHF, C 3 F 8 , SF 6 , and F 2 etc. can be used. As the chlorine-based gas, Cl 2 , SiCl 4 , CHCl 3 , CCl 4 , and BCl 3 etc. can be used. Also, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O 2 can be used in a predetermined ratio. These etching gases can further contain an inert gas such as He and / or Ar, if necessary.

[0083] After the absorber pattern 24a is formed, the resist pattern 26a is removed with a resist stripper. After removing the resist pattern 26a, the reflective mask 200 of the present embodiment is obtained by passing through a wet cleaning process using an acidic or alkaline aqueous solution (FIG. 5E).

[0084] In addition, when using the reflective mask blank 110 in which the etching mask film 28 is formed on the absorber film 24, after forming a pattern (etching mask pattern) on the etching mask film 28 using the resist pattern 26a as a mask, a step of forming a pattern on the absorber film 24 using the etching mask pattern as a mask is added.

[0085] The reflective mask 200 thus obtained has a structure in which the multilayer reflective film 12, the protective film 14, and the absorber pattern 24a are laminated on the substrate 10.

[0086] In the region 30 where the multilayer reflective film 12 (including the protective film 14) is exposed, it has the function of reflecting EUV light. In the region 32 where the multilayer reflective film 12 (including the protective film 14) is covered by the absorber pattern 24a, it has the function of absorbing EUV light. According to the reflective mask 200 of the present embodiment, since the thickness of the absorber pattern 24a can be made thinner than before so that the reflectance becomes, for example, 2.5% or less, a finer pattern can be transferred to the object to be transferred.

[0087] <Method for manufacturing a semiconductor device> By lithography using the reflective mask 200 of the present embodiment, a transfer pattern can be formed on a semiconductor substrate. This transfer pattern has the shape obtained by transferring the pattern of the reflective mask 200. By forming a transfer pattern on a semiconductor substrate using the reflective mask 200, a semiconductor device can be manufactured.

[0088] A method of transferring a pattern to a semiconductor substrate 56 with a resist by EUV light will be described with reference to FIG. 6.

[0089] FIG. 6 shows a pattern transfer apparatus 50. The pattern transfer apparatus 50 includes a laser plasma X-ray source 52, a reflective mask 200, a reduction optical system 54, etc. An X-ray reflecting mirror is used as the reduction optical system 54.

[0090] The pattern reflected by the reflective mask 200 is reduced by the reduction optical system 54 to about 1 / 4 of its original size. For example, a wavelength band of 13 - 14 nm is used as the exposure wavelength, and the optical path is preset to be in a vacuum. Under such conditions, the 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 the semiconductor substrate 56 with a resist through the reduction optical system 54.

[0091] The light reflected by the reflective mask 200 is incident on the reduction optical system 54. The light incident on the reduction optical system 54 forms a transfer pattern on the resist layer on the semiconductor substrate 56 with a resist. By developing the exposed resist layer, a resist pattern can be formed on the semiconductor substrate 56 with a resist. By etching the semiconductor substrate 56 using the resist pattern as a mask, for example, a predetermined wiring pattern can be formed on the semiconductor substrate. Through such processes and other necessary processes, a semiconductor device is manufactured.

Example

[0092] Hereinafter, examples and comparative examples will be described with reference to the drawings.

[0093] (Substrate 100 with a multilayer reflective film) First, a substrate 10 with a size of 6025 (about 152 mm × 152 mm × 6.35 mm) whose first main surface and second main surface were polished was prepared. This substrate 10 is a substrate made of low thermal expansion glass (SiO 2 -TiO 2 -based glass). The main surfaces of the substrate 10 were polished by a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process.

[0094] Next, a multilayer reflective film 12 was formed on the main surface (the 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 a multilayer reflective film 12 suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 12 was formed by alternately laminating a Mo film and a Si film on the substrate 10 by an ion beam sputtering method using a Mo target and a Si target and using krypton (Kr) as a process gas. First, a Si film was formed to a thickness of 4.2 nm, and then a Mo film was formed to a thickness of 2.8 nm. This was taken as one cycle, and 40 cycles were laminated in the same manner to form the multilayer reflective film 12.

[0095] Next, a Si material layer 16 was formed on the multilayer reflective film 12. The multilayer reflective film 12 and the Si material layer 16 were continuously formed by an ion beam sputtering method. The Si material layer 16 was formed into a Si film with a thickness of 4.0 nm using a Si target and krypton (Kr) as a process gas.

[0096] Next, a RuRh-based layer 18 or a Ru film was formed on the Si material layer 16. The RuRh-based layer 18 or the Ru film was formed to the film thickness shown in Table 1 by a magnetron sputtering method in an Ar gas atmosphere using a target having the composition shown in Table 1. The composition of the formed protective film 14 was measured by X-ray photoelectron spectroscopy (XPS).

[0097] Table 1 shows the composition and film thickness of the protective film 14 (RuRh-based layer 18 or Ru film) in the examples and comparative examples.

[0098] (Reflective mask blank 110) Using the above-described substrate 100 with a multilayer reflective film, a reflective mask blank 110 including an absorber film 24 was manufactured. Hereinafter, a method for manufacturing the reflective mask blank 110 will be described.

[0099] An absorber film 24 was formed on the protective film 14 of the substrate 100 with a multilayer reflective film by DC magnetron sputtering. The absorber film 24 was an absorber film 24 that was a laminated film composed of a TaN film as an absorption layer and a TaO film as a low reflection layer. A TaN film was formed as an absorption layer on the surface of the protective film 14 of the above-described substrate 100 with a multilayer reflective film by DC magnetron sputtering. This TaN film was formed by a reactive sputtering method in a mixed gas atmosphere of Ar gas and N 2 gas with the substrate 100 with a multilayer reflective film opposed to a Ta target. Next, a TaO film (low reflection layer) was formed on the TaN film by DC magnetron sputtering. This TaO film was formed by a reactive sputtering method in a mixed gas atmosphere of Ar and O 2 in the same manner as the TaN film with the substrate 100 with a multilayer reflective film opposed to a Ta target.

[0100] The composition (atomic ratio) of the TaN film was Ta:N = 70:30, and the film thickness was 48 nm. Also, the composition (atomic ratio) of the TaO film was Ta:O = 35:65, and the film thickness was 11 nm.

[0101] Next, on the 10 second main surface (backside main surface) of the substrate, a backside conductive film 22 made of CrN was formed under the following conditions by magnetron sputtering (reactive sputtering). Formation conditions of the backside conductive film 22: Cr target, mixed gas atmosphere of Ar and N 2 (Ar: 90 atomic%, N: 10 atomic%), film thickness 20 nm.

[0102] In the above manner, the reflective mask blanks 110 of Examples 1 to 6 and Comparative Example 1 were manufactured.

[0103] (Reflective mask 200) Next, using the above-described reflective mask blank 110, a reflective mask 200 was manufactured. The manufacture of the reflective mask 200 will be described with reference to FIGS. 5A - E.

[0104] First, as shown in FIG. 5B, a resist film 26 was formed on the absorber film 24 of the reflective mask blank 110. Then, a desired pattern such as a circuit pattern was drawn (exposed) on this resist film 26, and further developed and rinsed to form a predetermined resist pattern 26a (FIG. 5C). Next, using the resist pattern 26a as a mask, the TaO film (low reflection layer) of the absorber film 24 was dry-etched using CF 4 gas, and subsequently, the TaN film was dry-etched using Cl 2 gas to form an absorber pattern 24a (FIG. 5D).

[0105] Thereafter, the resist pattern 26a was removed by oxygen ashing. Finally, wet cleaning using pure water (DIW) was performed to manufacture the reflective masks 200 of Examples 1 to 6 and Comparative Example 1.

[0106] (Evaluation of the Reflective Mask 200 in the Examples and Comparative Examples) Regarding the reflective masks 200 in the above-described examples and comparative examples, the change in reflectance before and after etching the absorber film 24 was evaluated. Further, the reflective mask 200 was set in an EUV exposure apparatus, and the presence or absence of blister generation was evaluated when transferring a pattern onto a semiconductor substrate in an atmosphere containing hydrogen.

[0107] Specifically, before forming the absorber film 24 on the surface of the protective film 14 of the substrate 100 with the multilayer reflective film, the reflectance of the surface of the protective film 14 with respect to EUV light having a wavelength of 13.5 nm (reflectance before etching) was measured. Further, after forming the absorber pattern 24a by etching the absorber film 24, the reflectance of the surface of the protective film 14 not covered by the absorber pattern 24a (reflectance after etching) was similarly measured. Table 1 shows the change in reflectance of the surface of the protective film 14 before and after etching (the absolute value of the difference between the reflectance before etching and the reflectance after etching).

[0108] Regarding the presence or absence of blister generation, after taking out the reflective mask 200 from the exposure apparatus, it was confirmed by observing the cross-section of the reflective mask 200 with an electron microscope. When the generation of blisters was confirmed even at one of arbitrarily selected 10 cross-sections, it was determined that the generation of blisters was "present".

[0109]

Table 1

[0110] As can be seen from the results shown in Table 1, for the reflective masks 200 of Examples 1 to 6, the change in reflectance before and after etching the absorber film 24 was small. Further, even after setting the reflective mask 200 in the exposure apparatus and transferring a pattern onto a semiconductor substrate in an atmosphere containing hydrogen, no blister generation was confirmed between the protective film 14 and the absorber pattern 24a, and between the protective film 14 and the multilayer reflective film 12.

[0111] In the reflective mask 200 of Comparative Example 1, the change in reflectance before and after the etching of the absorber film 24 was small. However, the generation of blisters was confirmed between the protective film 14 and the absorber pattern 24a, and between the protective film 14 and the multilayer reflective film 12.

Explanation of Reference Numerals

[0112] 10 Substrate 12 Multilayer reflective film 14 Protective film 16 Si material layer 18 RuRh-based layer 22 Back conductive film 24 Absorber film 26 Resist film 28 Etching mask film 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 contains ruthenium (Ru), rhodium (Rh), and at least one additive element selected from titanium (Ti), zirconium (Zr), niobium (Nb), and vanadium (V); The content of the rhodium (Rh) is 15 atomic % or more and 50 atomic % or less, A multilayer reflective film-coated substrate, wherein the content of the additional element is 1 atomic % or more and 20 atomic % or less.

2. A substrate with a multilayer reflective film as described in claim 1, characterized in that the rhodium (Rh) content is 20 atomic % or more.

3. The additive element is at least one selected from titanium (Ti), zirconium (Zr), and vanadium (V), 3. The substrate with a multilayer reflective film according to claim 1, wherein the content of the additional element is from 1 atomic % to 10 atomic %.

4. The additive element is niobium (Nb), 3. The multilayer reflective film coated substrate according to claim 1, wherein the content of said niobium (Nb) is 1 atomic % or more and 20 atomic % or less.

5. A substrate with a multilayer reflective film described in any one of claims 1 to 4, characterized in that the protective film is a gradient film in which the content of the added element on the side in contact with the multilayer reflective film is greater than the content of the added element on the side opposite to the side in contact with the multilayer reflective film.

6. 6. A substrate with a multilayer reflective film as described in any one of claims 1 to 5, characterized in that the protective film is a gradient film in which the Rh content on the side in contact with the multilayer reflective film is lower than the Rh content on the side opposite to the side in contact with the multilayer reflective film.

7. 5. The multilayer reflective film coated substrate according to claim 1, wherein the protective film includes a layer of the additional element and a RuRh layer.

8. 8. The substrate with a multilayer reflective film according to claim 1, wherein the protective film includes a Si material layer containing silicon (Si) on a side in contact with the multilayer reflective film.

9. 9. A reflective mask blank comprising an absorber film on the protective film of the multilayer reflective film-coated substrate according to claim 1.

10. A reflective mask comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to claim 9.

11. 11. 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 10 to form a transfer pattern on a transfer target.

Images