Multilayer reflective film-equipped substrate, reflective mask blank, reflective mask, and method for manufacturing semiconductor device

Abstract

Provided is a multilayer reflective film-equipped substrate having a multilayer reflective film which has a shallow effective reflection surface and in which it is possible to suppress the phenomenon in which atoms serving as a material are diffused between a low-refractive-index layer and a high-refractive-index layer.　This multilayer reflective film-equipped substrate has a substrate (1) and a multilayer reflective film (2) provided on the substrate and is characterized in that: the multilayer reflective film includes a multilayer film in which a low-refractive-index layer (24) and a high-refractive-index layer (22) including silicon (Si) are alternatingly layered; the multilayer reflective film further includes at least one intermediate layer (26) disposed between the low-refractive-index layer and the high-refractive-index layer; the multilayer reflective film includes at least one added element selected from nitrogen (N), carbon (C), and oxygen (O); and the content of the added element in the multilayer reflective film is no more than 40 at%.

Description

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

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

[0002] 2. Description of the Related Art In recent years, with the increasing demand for higher density and higher precision in VLSI devices, EUV lithography, an exposure technique using extreme ultraviolet (hereinafter referred to as EUV) light, has been proposed.

[0003] A reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film to absorb the exposure light. The optical image reflected by the multilayer reflective film is transferred onto a semiconductor substrate (transfer target) such as a silicon wafer through a reflective optical system.

[0004] As an example of a reflective mask blank for manufacturing a reflective mask, Patent Document 1 describes an EUV blank mask including a substrate, a reflective film laminated on the substrate, and an absorbing film laminated on the reflective film. Patent Document 1 describes that the reflective film has a structure in which pairs each including a first layer made of Ru or a Ru compound in which one or more elements selected from Mo, Nb, and Zr are added to Ru, and a second layer made of Si are laminated multiple times.

[0005] Patent Document 2 describes a multilayer reflecting mirror for soft X-rays and vacuum ultraviolet rays, which has a multilayer thin film structure consisting of alternating layers of two main materials, A and B, with different refractive indices. Patent Document 2 describes that at least one or more sub-material thin films, which have the effect of reducing roughness at the stacking interface, are stacked between each of the A-B layers and / or the B-A layers, forming a periodic structure. Patent Document 2 also describes that the low refractive index layers are generally formed of high-melting point metal materials such as tungsten and molybdenum, or compounds containing these as their main components, and that the high refractive index layers are generally formed of light elements such as carbon, silicon, boron, and beryllium, or compounds containing these as their main components. Furthermore, Patent Document 2 lists examples of sub-materials, such as carbon (C), boron (B), beryllium (Be), silicon carbide (SiC), and silicon nitride (Si). ３ N ４ , silicon oxide SiO ２ , Boron nitride BN, Boron carbide B ４ It is described that examples of the conductor include conductors of light elements with atomic numbers of 13 or less, such as C and aluminum nitride AlN, or compounds thereof.

[0006] Patent Document 3 describes a multilayer spectral reflector characterized by using a compound intermediate layer made of Si and C between a heavy element layer and a light element layer of a multilayer spectral element having a Bragg diffraction effect. Patent Document 3 also describes a multilayer spectral reflector characterized by using Mo, Ru, Rh, or Re as the heavy element layer, Si as the light element layer, and Si as the intermediate layer. １００－ｘ C ｘ It is described that a multilayer film was produced using the above method.

[0007] Patent Document 4 describes a multilayer X-ray mirror in which a plurality of material layers are periodically stacked. Patent Document 4 also describes forming an intermediate layer between each of the material layers, and using a material having a higher melting point than at least one of the material layers as the intermediate layer. Patent Document 4 also describes fabricating a Mo / Si multilayer film using Mo as a heavy element layer and Si as a light element layer.

[0008] In Non-Patent Document 1, B is added to a Mo / Si multilayer reflector. ４Furthermore, Non-Patent Document 1 describes the use of a Ru / Si multilayer reflective film as the multilayer reflective film.

[0009] JP 2021-110953, JP 2-242201, JP 5-203798, JP 9-230098

[0010] Overt Wood et al. "Improved Ru / Si multilayer reflective coatings for advanced extreme-ultraviolet lithography photomasks". Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 977619 (18 March 2016)

[0011] The above-mentioned EUV lithography is an exposure technology that uses extreme ultraviolet light (EUV light). EUV light is light in the wavelength band of the soft X-ray region or vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm. In the case of EUV lithography, EUV light with a wavelength of 13 to 14 nm (for example, a wavelength of 13.5 nm) can be used.

[0012] EUV lithography uses a reflective mask with an absorber pattern. EUV light irradiated onto the reflective mask is absorbed in the areas where the absorber pattern is present and reflected in the areas where the absorber pattern is not present. A multilayer reflective film is exposed in the areas where the absorber pattern is not present. The exposed multilayer reflective film reflects the EUV light. In EUV lithography, the optical image reflected by the multilayer reflective film (the areas where the absorber pattern is not present) is transferred onto a semiconductor substrate (transfer target) such as a silicon wafer through a reflection optical system.

[0013] Generally, a multilayer reflective film is used in which elements with different refractive indices are periodically stacked. For example, a Mo / Si periodic stacked film is used as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm (e.g., 13.5 nm), in which Mo films with a low refractive index and Si films with a high refractive index are alternately stacked for 40 to 60 periods.

[0014] In order to achieve high density and high precision in semiconductor devices using a reflective mask, it is necessary for the reflective region of the reflective mask (the surface of the multilayer reflective film) to have high reflectivity with respect to EUV light, which is the exposure light.

[0015] As the node (minimum line width) transferred to a substrate, such as a semiconductor substrate, becomes narrower, the impact of the 3D effect on transfer characteristics becomes greater. Reducing the film thickness of the absorber pattern is effective in suppressing the 3D effect. However, in EUV lithography using reflective exposure, simply thinning the absorber film to form the absorber pattern is insufficient. Therefore, control of the reflective surface that reflects EUV light is also necessary. Specifically, control of the reflective surface requires bringing the effective reflective surface of the multilayer reflective film as close as possible to the surface to prevent the EUV light reflected from the multilayer reflective film from spreading. In this specification, an effective reflective surface that is relatively close to the surface of the multilayer reflective film may be referred to as a "shallow effective reflective surface." By having a shallow effective reflective surface, the 3D effect can be suppressed and the number of layers of the multilayer reflective film can be reduced.

[0016] In order to bring the effective reflective surface of the multilayer reflective film as close as possible to the surface, it is necessary to select a material for the multilayer reflective film that will have a high reflectivity for EUV light. The multilayer reflective film reflects EUV light by having a stacked structure of low-refractive index layers and high-refractive index layers. When a material for the multilayer reflective film is selected to have a high reflectivity for EUV light, depending on the material, a phenomenon may occur in which atoms of the material diffuse between the low-refractive index layers and the high-refractive index layers. When this diffusion phenomenon occurs, the reflectivity of the multilayer reflective film decreases.

[0017] Therefore, an object of the present invention is to provide a multilayer reflective film-coated substrate having a shallow effective reflective surface and a multilayer reflective film capable of suppressing the phenomenon of diffusion of material atoms between a low refractive index layer and a high refractive index layer, a reflective mask blank, and a reflective mask. Another object of the present invention is to provide a method for manufacturing a semiconductor device using the above reflective mask.

[0018] In order to solve the above problems, the present invention has the following configuration.

[0019] (Structure 1) Structure 1 of the present invention is a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film provided on the substrate, wherein the multilayer reflective film includes a multilayer film in which low refractive index layers and high refractive index layers containing silicon (Si) are alternately stacked, the multilayer reflective film further includes at least one intermediate layer disposed between the low refractive index layers and the high refractive index layers, the multilayer reflective film includes at least one additive element selected from nitrogen (N), carbon (C) and oxygen (O), and the content of the additive element in the multilayer reflective film is 40 atomic % or less.

[0020] (Configuration 2) Configuration 2 of the present invention is the multilayer reflective film-coated substrate according to configuration 1, characterized in that the content of the additive element is 1 atomic % or more.

[0021] (Configuration 3) Configuration 3 of the present invention is the multilayer reflective film-coated substrate according to configuration 1 or 2, characterized in that the intermediate layer contains at least one selected from SiN, SiO, SiC, SiON, SiCN, SiOC, and SiOCN.

[0022] (Configuration 4) Configuration 4 of the present invention is the multilayer reflective film coated substrate according to any one of configurations 1 to 3, wherein the low refractive index layer contains ruthenium (Ru).

[0023] (Structure 5) Structure 5 of the present invention is the multilayer reflective film-coated substrate according to any one of Structures 1 to 4, wherein the low refractive index layer contains ruthenium (Ru), and when a stacked structure of one low refractive index layer and one high refractive index layer is defined as one period, the stacked structure has less than 40 periods.

[0024] (Configuration 6) Configuration 6 of the present invention is the multilayer reflective film coated substrate according to any one of claims 1 to 5, characterized in that it has a protective film on the multilayer reflective film.

[0025] (Configuration 7) Configuration 7 of the present invention is the multilayer reflective film-coated substrate of Configuration 6, wherein 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).

[0026] (Configuration 8) Configuration 8 of the present invention is a reflective mask blank characterized in that an absorber film is provided on the protective film of the multilayer reflective film coated substrate of configuration 6 or 7.

[0027] (Configuration 9) Configuration 9 of the present invention is a reflective mask blank characterized by having an absorber film on the multilayer reflective film of the multilayer reflective film-coated substrate of any one of configurations 1 to 5.

[0028] (Configuration 10) Configuration 10 of the present invention is a reflective mask characterized by having an absorber pattern obtained by patterning the absorber film of the reflective mask blank of configuration 8 or 9.

[0029] (Configuration 11) Configuration 11 of the present invention is a method for manufacturing a semiconductor device, comprising a step of performing a lithography process using an exposure apparatus with the reflective mask of Configuration 10 to form a transfer pattern on a transfer target.

[0030] According to the present invention, it is possible to provide a multilayer reflective film-coated substrate having a multilayer reflective film that has a shallow effective reflective surface and that can suppress the phenomenon of diffusion of material atoms between a low refractive index layer and a high refractive index layer, a reflective mask blank, and a reflective mask. Also, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device using the above reflective mask.

[0031] FIG. 1 is a cross-sectional view schematically showing an example of a multilayer reflective film-coated substrate of the present embodiment. FIG. 2 is a cross-sectional view schematically showing another example of a multilayer reflective film-coated substrate of the present embodiment. FIG. 3 is a cross-sectional view schematically showing an example of a reflective mask blank of the present embodiment. FIG. 4 is a cross-sectional view schematically showing another example of a reflective mask blank of the present embodiment. FIG. 5 is a cross-sectional view schematically showing yet another example of a reflective mask blank of the present embodiment. FIG. 6 is a cross-sectional view schematically showing an example of a method for manufacturing a reflective mask of the present embodiment. FIG. 7 is a cross-sectional view schematically showing a first embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 8 is a cross-sectional view schematically showing a second embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 9 is a cross-sectional view schematically showing a third embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 10 is a cross-sectional view schematically showing a fourth embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 11 is a cross-sectional view schematically showing a fifth embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 12 is a cross-sectional view schematically showing a sixth embodiment of a multilayer reflective film of a multilayer reflective film-coated substrate of the present embodiment. FIG. 13 is a cross-sectional view schematically showing an example of an EUV exposure apparatus.

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are intended to specifically explain the present invention, and are not intended to limit the scope of the present invention.

[0033] FIG. 1 is a cross-sectional schematic diagram showing an example of a multilayer reflective film-coated substrate 90 of this embodiment. The multilayer reflective film-coated substrate 90 of this embodiment includes a substrate 1 and a multilayer reflective film 2 provided on the substrate 1. As shown in FIGS. 7 to 12 , the multilayer reflective film 2 includes a multilayer film in which low-refractive index layers 24 and high-refractive index layers 22 are alternately stacked. As shown in FIGS. 7 to 12 , the multilayer reflective film 2 further includes at least one intermediate layer 26 disposed between the low-refractive index layers 24 and the high-refractive index layers 22. A back surface conductive film 5 for an electrostatic chuck may be formed on the back surface of the substrate 1 (the surface opposite to the side on which the multilayer reflective film 2 is formed).

[0034] Fig. 2 is a cross-sectional schematic diagram showing another example of a multilayer reflective film-coated substrate 90 of this embodiment. The multilayer reflective film-coated substrate 90 shown in Fig. 2 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a protective film 3 formed on the multilayer reflective film 2. As shown in Figs. 7 to 12 , the multilayer reflective film 2 has a low refractive index layer 24, a high refractive index layer 22, and at least one intermediate layer 26 disposed between the low refractive index layer 24 and the high refractive index layer 22. A back surface conductive film 5 for an electrostatic chuck may be formed on the back surface of the substrate 1 (the surface opposite to the side on which the multilayer reflective film 2 is formed).

[0035] In this specification, "thin film B is disposed (formed) on thin film A (or substrate)" not only means that thin film B is disposed (formed) in contact with the surface of thin film A (or substrate), but also means that another thin film C is present between thin film A (or substrate) and thin film B. Furthermore, in this specification, for example, "thin film B is disposed in contact with the surface of thin film A (or substrate)" means that thin film A (or substrate) and thin film B are disposed so as to be in direct contact with each other, without any other thin film interposed between them. Furthermore, in this specification, "on" does not necessarily mean the upper side in the vertical direction. "on" merely indicates the relative positional relationship between the thin film, substrate 1, etc.

[0036] The multilayer reflective film coated substrate 90 of this embodiment will be specifically described.

[0037] <Substrate 1> To prevent distortion of the transfer pattern due to heat during exposure to EUV light, a substrate having a low thermal expansion coefficient within the range of 0±5 ppb / °C is preferably used as the substrate 1. Examples of materials having a low thermal expansion coefficient within this range include SiO ２ -TiO ２ Glasses, multi-component glass ceramics, etc. can be used.

[0038] The main surface (first main surface) of the substrate 1 on which a transfer pattern (the absorber pattern 4a described below) is formed is preferably processed to increase its flatness. Increasing the flatness of the main surface of the substrate 1 can improve the positional accuracy and transfer accuracy of the pattern. For example, in the case of EUV exposure, in a 132 mm × 132 mm area of ​​the main surface of the substrate 1 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. Furthermore, the second main surface (rear surface) opposite the side on which the transfer pattern is formed is the surface fixed to the exposure apparatus by an electrostatic chuck. In a 142 mm × 142 mm area of ​​the rear surface, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In this specification, flatness is a value representing the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). The flatness (TIR) ​​is the absolute value of the difference in height between the highest point on the surface of substrate 1 above the focal plane, which is determined by the least squares method using the surface of substrate 1 as a reference, and the lowest point on the surface of substrate 1 below this focal plane.

[0039] In the case of EUV exposure, the surface roughness of the main surface of the substrate 1 on which the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured using an atomic force microscope.

[0040] The substrate 1 preferably has high rigidity to prevent deformation due to film stress of the thin film (such as the multilayer reflective film 2) formed thereon. The substrate 1 preferably has a high Young's modulus of 65 GPa or more.

[0041] <Multilayer reflective film 2>

[0042] As shown in FIGS. 1 and 2, a multilayer reflective film coated substrate 90 of this embodiment has a substrate 1 and a multilayer reflective film 2 provided on the substrate 1 .

[0043] The multilayer reflective film 2 has a structure in which a plurality of layers whose main components are elements with different refractive indices are periodically stacked. In general, the multilayer reflective film 2 includes a multilayer film in which thin films of a light element or its compound, which is a high refractive index material (high refractive index layers 22), and thin films of a heavy element or its compound, which is a low refractive index material (low refractive index layers 24), are alternately stacked.

[0044] The multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment includes a multilayer film in which low refractive index layers 24 and high refractive index layers 22 containing silicon (Si) are alternately stacked.

[0045] In this embodiment, the high-refractive index layer 22 is a layer containing silicon (Si). The high-refractive index layer 22 may contain elemental 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 22, a multilayer reflective film 2 with excellent reflectivity for EUV light can be obtained. In order to obtain a relatively high reflectivity, the high-refractive index layer 22 is preferably made of silicon (Si). Note that "the high-refractive index layer 22 is made of silicon (Si)" does not prevent the presence of impurities other than Si that are inevitably mixed in the high-refractive index layer 22. The same applies to other thin films and other elements.

[0046] The silicon (Si) content in the multilayer reflective film 2 of this embodiment is preferably 50 atomic % or more, more preferably 65 atomic % or more. The silicon (Si) content in the multilayer reflective film 2 is preferably 99 atomic % or less, more preferably 95 atomic % or less. The silicon (Si) content in the multilayer reflective film 2 is the total content of Si constituting the high refractive index layer 22 and the intermediate layer 26.

[0047] In this embodiment, the low refractive index layer 24 can 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.

[0048] The low refractive index layer 24 of the multilayer reflective film coated substrate 90 of this embodiment preferably contains ruthenium (Ru). Examples of materials for the low refractive index layer 24 containing Ru include simple Ru, RuRh, RuNb, and RuMo. When the low refractive index layer 24 contains ruthenium (Ru), a shallow effective reflection surface can be obtained.

[0049] The content of the elements constituting the low refractive index layer 24 in the multilayer reflective film 2 of this embodiment is preferably 40 atomic % or more, more preferably 55 atomic % or more. The content of the elements constituting the low refractive index layer 24 in the multilayer reflective film 2 is preferably 99 atomic % or less, more preferably 85 atomic % or less. When a plurality of elements constituting the low refractive index layer 24 are contained in the multilayer reflective film 2, the content of the elements constituting the low refractive index layer 24 is the total content of these elements.

[0050] As the node (minimum line width) transferred to a transfer target, such as a semiconductor substrate 60, becomes narrower, the impact of the 3D effect on transfer characteristics becomes greater. The 3D effect refers to the influence of the three-dimensional structure of the reflective mask 200, including its height structure, on the fidelity of the transferred pattern relative to the mask pattern. In EUV lithography, controlling the reflective surface of the reflective mask 200 is necessary to suppress the 3D effect. Specifically, controlling the reflective surface requires bringing the effective reflective surface of the multilayer reflective film 2 as close to the surface as possible. By having the reflective mask 200 have a shallow effective reflective surface, it is possible to prevent the EUV light reflected from the multilayer reflective film 2 from spreading, thereby suppressing the 3D effect. The multilayer reflective film 2 includes a multilayer film formed by alternately stacking low-refractive-index layers 24 containing ruthenium (Ru) and high-refractive-index layers 22 containing silicon (Si). This allows the effective reflective surface of the multilayer reflective film 2 to be shallower than conventional Mo / Si multilayer reflective films.

[0051] On the other hand, when a material containing Ru is used for the low-refractive-index layer 24, a problem may arise in that Si in the high-refractive-index layer 22 diffuses into the low-refractive-index layer 24, reducing the reflectivity of the multilayer reflective film 2 for EUV light. In this embodiment, as shown in Figures 7 to 12, the multilayer reflective film 2 further includes at least one predetermined intermediate layer 26 disposed between the low-refractive-index layer 24 and the high-refractive-index layer 22, thereby preventing this problem from occurring.

[0052] 7 to 12 , the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment further includes at least one intermediate layer 26 disposed between the low refractive index layer 24 and the high refractive index layer 22. The inclusion of the intermediate layer 26 in the multilayer reflective film 2 can suppress diffusion of Si in the high refractive index layer 22 into the low refractive index layer 24.

[0053] The multilayer reflective film 2 contains at least one additive element selected from nitrogen (N), carbon (C), and oxygen (O). These elements can be contained in the intermediate layer 26. The thickness of the intermediate layer 26 is quite thin. The thickness of the intermediate layer 26 is 1.2 nm or less, for example, approximately 0.3 nm. When an intermediate layer 26 having such a thickness is formed, the boundary between the intermediate layer 26 and the low-refractive-index layer 24 and / or the boundary between the intermediate layer 26 and the high-refractive-index layer 22 may not be clearly defined. Therefore, although the specified additive element is an element added to form the intermediate layer 26, it can be said that it is an element present in the multilayer reflective film 2 (in the intermediate layer 26, the low-refractive-index layer 24, and the high-refractive-index layer 22).

[0054] The thickness of the intermediate layer 26 is preferably 0.1 nm to 1.2 nm, and more preferably 0.3 nm to 1.0 nm. When the thickness of the intermediate layer 26 is within the predetermined range, the diffusion of Si in the high-refractive-index layer 22 into the low-refractive-index layer 24 can be more reliably suppressed.

[0055] The content of the additive element in the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment is 40 atomic % or less. If the content of the additive element is too high, it may adversely affect the reflectivity of the multilayer reflective film 2 for EUV light. When the additive element is nitrogen (N), the content of the additive element (N) in the multilayer reflective film 2 is preferably 35 atomic % or less, and more preferably 20 atomic % or less. When the additive element is carbon (C), the content of the additive element (C) in the multilayer reflective film 2 is preferably 40 atomic % or less, and more preferably 30 atomic % or less. When the additive element is oxygen (O), the content of the additive element (O) in the multilayer reflective film 2 is preferably 15 atomic % or less, and more preferably 10 atomic % or less.

[0056] The content of the additive element in the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment is preferably 1 atomic % or more. When the content of the additive element in the multilayer reflective film 2 is a predetermined content, it is possible to more reliably suppress the diffusion of Si in the high refractive index layer 22 into the low refractive index layer 24.

[0057] In order to more efficiently suppress the diffusion of Si from the high-refractive-index layers 22 into the low-refractive-index layers 24, when nitrogen (N) is the additive element, the content of the additive element (N) in the multilayer reflective film 2 is preferably 5 atomic % or more, more preferably 10 atomic % or more. When carbon (C) is the additive element, the content of the additive element (C) in the multilayer reflective film 2 is preferably 10 atomic % or more, more preferably 20 atomic % or more. When oxygen (O) is the additive element, the content of the additive element (O) in the multilayer reflective film 2 is preferably 3 atomic % or more, more preferably 5 atomic % or more.

[0058] The intermediate layer 26 of the multilayer reflective film 2 of the multilayer reflective film coated substrate 90 of this embodiment preferably contains at least one selected from SiN, SiO, SiC, SiON, SiCN, SiOC, and SiOCN. When the intermediate layer 26 is made of one of these silicon compounds, the intermediate layer 26 disposed between the low refractive index layer 24 and the high refractive index layer 22 can more reliably suppress the diffusion of Si from the high refractive index layer 22 into the low refractive index layer 24. In addition, the intermediate layer 26 contains B４ The intermediate layer 26 may contain at least one boron compound selected from C and BN. ４ It is preferable that the intermediate layer 26 is made of at least one selected from C and BN. When the intermediate layer 26 contains a predetermined boron compound, it is possible to more reliably suppress the diffusion of Si in the high refractive index layer 22 into the low refractive index layer 24.

[0059] To form the multilayer reflective film 2, generally, high-refractive index layers 22 and low-refractive index layers 24 can be laminated in this order from the substrate 1 side in multiple cycles. In this case, one stacked structure (high-refractive index layer 22 / low-refractive index layer 24) constitutes one cycle. In the multilayer reflective film-coated substrate 90 of this embodiment, the multilayer reflective film 2 includes an intermediate layer 26, so that the intermediate layer 26 can be appropriately disposed between the high-refractive index layer 22 and the low-refractive index layer 24.

[0060] As shown in Fig. 7 , in the first embodiment of the multilayer reflective film 2, a structure can be formed in which a high refractive index layer 22, an intermediate layer 26, a low refractive index layer 24, and an intermediate layer 26 are stacked in this order from the substrate 1 side. In this case, the structure of "high refractive index layer 22 / intermediate layer 26 / low refractive index layer 24 / intermediate layer 26" is one unit (one period). Fig. 7 shows an example in which one period of the multilayer reflective film 2 of the first embodiment is arranged on the substrate 1. In the first embodiment, when multiple periods of the multilayer reflective film 2 are arranged on the substrate 1, the surface layer of the topmost period (the period farthest from the substrate 1) is the intermediate layer 26 (Si-containing layer).

[0061] In the second embodiment of the multilayer reflective film 2, a structure can be formed in which a high refractive index layer 22, an intermediate layer 26, and a low refractive index layer 24 are stacked in this order from the substrate 1 side. Fig. 8 shows an example in which one cycle of the multilayer reflective film 2 of the second embodiment is arranged on the substrate 1. In this case, the structure of "high refractive index layer 22 / intermediate layer 26 / low refractive index layer 24" is one unit (one cycle). In the second embodiment, when multiple cycles of the multilayer reflective film 2 are arranged on the substrate 1, the surface layer of the topmost cycle is the low refractive index layer 24.

[0062] In the third embodiment of the multilayer reflective film 2, a structure can be formed in which a high refractive index layer 22, a low refractive index layer 24, and an intermediate layer 26 are stacked in this order from the substrate 1 side. Fig. 9 shows an example in which one cycle of the multilayer reflective film 2 of the third embodiment is arranged on the substrate 1. In this case, the structure of "high refractive index layer 22 / low refractive index layer 24 / intermediate layer 26" is one unit (one cycle). In the third embodiment, when multiple cycles of the multilayer reflective film 2 are arranged on the substrate 1, the surface layer of the topmost cycle is the intermediate layer 26 (Si-containing layer).

[0063] In the fourth embodiment of the multilayer reflective film 2, a structure can be formed in which a low refractive index layer 24, an intermediate layer 26, a high refractive index layer 22, and an intermediate layer 26 are stacked in this order from the substrate 1 side. Fig. 10 shows an example in which one cycle of the multilayer reflective film 2 of the fourth embodiment is arranged on the substrate 1. In this case, the structure of "low refractive index layer 24 / intermediate layer 26 / high refractive index layer 22 / intermediate layer 26" is one unit (one cycle). In the fourth embodiment, when multiple cycles of the multilayer reflective film 2 are arranged on the substrate 1, the surface layer of the topmost cycle is the intermediate layer 26 (Si-containing layer).

[0064] In the fifth embodiment of the multilayer reflective film 2, a structure can be formed in which a low refractive index layer 24, an intermediate layer 26, and a high refractive index layer 22 are laminated in this order from the substrate 1 side. Fig. 11 shows an example in which one cycle of the multilayer reflective film 2 of the fifth embodiment is disposed on the substrate 1. In this case, the structure of "low refractive index layer 24 / intermediate layer 26 / high refractive index layer 22" is one unit (one cycle). In the fifth embodiment, the surface layer of the topmost cycle is the high refractive index layer 22.

[0065] In the sixth embodiment of the multilayer reflective film 2, a structure can be formed in which a low refractive index layer 24, a high refractive index layer 22, and an intermediate layer 26 are laminated in this order from the substrate 1 side. Fig. 12 shows an example in which one cycle of the multilayer reflective film 2 of the sixth embodiment is disposed on the substrate 1. In this case, the structure of "low refractive index layer 24 / high refractive index layer 22 / intermediate layer 26" is one unit (one cycle). In the sixth embodiment, the surface layer of the topmost cycle is the intermediate layer 26 (Si-containing layer).

[0066] In the second embodiment of the multilayer reflective film 2, for example, when the low refractive index layer 24 is the surface of the multilayer reflective film 2, it is preferable to further form a layer containing Si (Si-containing layer) similar to the high refractive index layer 22 on the topmost period of the low refractive index layer 24 in order to suppress changes over time. The Si-containing layer can be at least a part of the protective film 3 described later. The protective film 3 described later can contain the Si-containing layer.

[0067] In the first embodiment and the like of the multilayer reflective film 2, the uppermost surface layer (intermediate layer 26) of one period can also serve as a Si-containing layer that is part of the protective film 3 described below. In this case, the intermediate layer 26 of the surface layer is preferably made of SiN, SiC, or SiCN.

[0068] In the fifth embodiment of the multilayer reflective film 2 , when the surface layer of the uppermost period is the high refractive index layer 22 , the protective film 3 can be formed on the high refractive index layer 22 .

[0069] Next, a description will be given of the relationship between the material of the intermediate layer 26 and the Si-containing layer which is at least a part of the protective film 3. The Si-containing layer, SiN material layer, and SiC material layer in this description will be described in the description of the protective film 3.

[0070] The material of the intermediate layer 26 and the material of the Si-containing layer can be the same, and the Si-containing layer can be oxygen-free.

[0071] When the intermediate layer 26 is formed using SiN as a material, the Si-containing layer is preferably a SiN material layer or a SiC material layer. The Si-containing layer is more preferably a SiN material layer. Furthermore, it is even more preferable that the N content of the SiN material layer is greater than the N content of the intermediate layer 26. As a result, it is possible to suppress the diffusion of Si into the protective film 3, which will be described later.

[0072] When the intermediate layer 26 is formed using SiC as a material, the Si-containing layer is preferably a SiN material layer or a SiC material layer. The Si-containing layer is more preferably a SiC material layer. Furthermore, it is even more preferable that the C content of the SiC material layer is higher than the C content of the intermediate layer 26. As a result, it is possible to suppress diffusion of Si into the protective film 3, which will be described later.

[0073] When the intermediate layer 26 is formed using SiO as a material, the Si-containing layer is preferably a SiN material layer or a SiC material layer, which can suppress diffusion of Si into the protective film 3 described below.

[0074] The material of the intermediate layer 26 and the material of the Si-containing layer can be different.

[0075] The intermediate layer 26 is B ４ When the Si-containing layer is formed using C as the material, the Si-containing layer is preferably a SiN material layer or a SiC material layer. The Si-containing layer is more preferably a SiN material layer. As a result, high reflectance can be maintained while suppressing diffusion between the high refractive index layer 22 and the low refractive index layer 24.

[0076] When the low-refractive-index layer 24 of the multilayer reflective film-coated substrate 90 of this embodiment contains ruthenium (Ru), the stacked structure preferably has fewer than 40 periods, where one period is a stacked structure including one low-refractive-index layer 24 and one high-refractive-index layer 22. When the low-refractive-index layer 24 contains Ru, the stacked structure of the multilayer reflective film 2 more preferably has 35 periods or less. Because the effective reflective surface of the multilayer reflective film 2 of this embodiment is shallow, an appropriate reflectivity can be obtained with a smaller number of periods than in conventional multilayer reflective films 2. Therefore, by using the multilayer reflective film-coated substrate 90 of this embodiment, the 3D effect can be suppressed. Note that, in order to obtain an appropriate reflectivity for the multilayer reflective film 2, the stacked structure preferably has 20 periods or more, and more preferably has 25 periods or more.

[0077] If the high-refractive-index layer 22 of the multilayer reflective film 2 is amorphous and the low-refractive-index layer 24 of the multilayer reflective film 2 is amorphous, Si will easily diffuse in the high-refractive-index layer 22. Therefore, if the high-refractive-index layer 22 of the multilayer reflective film 2 is amorphous, it is preferable that the low-refractive-index layer 24 of the multilayer reflective film 2 has a crystalline structure. If the low-refractive-index layer 24 has a crystalline structure, it is preferable that the film thickness of the low-refractive-index layer 24 be 2.5 nm or more and 3.5 nm or less.

[0078] When the low refractive index layer 24 of the multilayer reflective coating 2 of this embodiment contains ruthenium (Ru), the uppermost layer of the multilayer reflective coating 2 can be the low refractive index layer 24. This is because Ru has the function of protecting the multilayer reflective coating 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200, which will be described later. In this case, the low refractive index layer 24 of the uppermost layer of the multilayer reflective coating 2 can also function as the protective film 3.

[0079] The reflectance of the multilayer reflective film 2 used in this embodiment alone is, for example, 65% or more. The upper limit of the reflectance of the multilayer reflective film 2 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 2 can be selected so as to satisfy Bragg's law. In the case of a multilayer reflective film 2 for reflecting EUV light with a wavelength of 13.5 nm, the film thickness of one period (one pair of high-refractive-index layers 22 and low-refractive-index layers 24, and at least one intermediate layer 26) is preferably about 7 nm.

[0080] The multilayer reflective film 2 can be formed by a known method. For example, the multilayer reflective film 2 can be formed by a magnetron sputtering method such as an ion beam sputtering method, a DC sputtering method, or an RF sputtering method. The magnetron sputtering method is preferred because it allows the high refractive index layer 22, the low refractive index layer 24, and the intermediate layer 26 to be deposited successively.

[0081] The intermediate layer 26 can be formed by magnetron sputtering (reactive sputtering) using a Si target in a predetermined gas atmosphere. Alternatively, the intermediate layer 26 can be formed by magnetron sputtering using a SiN sintered body, a SiC sintered body, or a SiO sintered body as a target. When forming the SiN sintered body, a SiC sintered body, or a SiO sintered body, an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr) can be added as a sintering aid. Adding a sintering aid can produce a sintered body with high density. The intermediate layer 26 thus formed contains the oxide of the metal added as a sintering aid.

[0082] The multilayer reflective film 2 may contain an oxide of at least one metal selected from magnesium (Mg), aluminum (Al), titanium (Ti), yttrium (Y), and zirconium (Zr). The content of the metal (at least one metal selected from Mg, Al, Ti, Y, and Zr) in the multilayer reflective film 2 is preferably 0.05 to 3.0 atomic %, more preferably 0.1 to 2.5 atomic %.

[0083] For example, if the multilayer reflective film 2 is a Si / SiN / Ru multilayer film using Si for the high-refractive index layer 22, SiN for the intermediate layer 26, and Ru for the low-refractive index layer 24, a Si film (high-refractive index layer 22) with a thickness of approximately 3.9 nm is formed on the substrate 1 by magnetron sputtering using a Si target in a Kr gas atmosphere. Next, a SiN film (intermediate layer 26) with a thickness of approximately 0.3 nm is formed by magnetron sputtering (reactive sputtering) using a Si target in a Kr gas and nitrogen gas atmosphere. Next, a Ru film (low-refractive index layer 24) with a thickness of approximately 2.8 nm is formed by magnetron sputtering using a Ru target in a Kr gas atmosphere. By repeating this process, a multilayer reflective film 2 can be formed in which 20 to 39 periods of Si / SiN / Ru films are stacked. The total thickness of one period of the Si / SiN / Ru film is preferably 7 nm.

[0084] <Protective Film 3> As shown in FIG. 2, the multilayer reflective film coated substrate 90 of this embodiment preferably has a protective film 3 on the multilayer reflective film 2.

[0085] In order to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200, which will be described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with the surface of the multilayer reflective film 2. The protective film 3 also has the function of protecting the multilayer reflective film 2 when repairing opacity defects in the transfer pattern (absorber pattern 4a) using an electron beam (EB). By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 can be suppressed when manufacturing the reflective mask 200. As a result, the reflectivity characteristics of the multilayer reflective film 2 for EUV light are improved.

[0086] FIG. 2 shows a single-layer protective film 3. However, the protective film 3 can also have a two-layer laminate structure. Alternatively, the protective film 3 can have a three-layer or more laminate structure, with the bottom and top layers being layers made of a material containing, for example, ruthenium (Ru), and a metal or alloy other than Ru being interposed between the bottom and top layers. The protective film 3 is formed, for example, from a material containing Ru as a primary component. Examples of materials containing Ru as a primary component include Ru metal itself, Ru alloys containing Ru and at least one metal selected from titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials further containing nitrogen. The protective film 3 is formed, for example, from a material containing rhodium (Rh) as a primary component. Examples of materials containing Rh as a main component include Rh metal alone, Rh alloys containing Rh and at least one metal selected from titanium (Ti), niobium (Nb), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials further containing nitrogen.

[0087] The Ru content of the Ru alloy used in the protective film 3 is 50 atomic % or more and less than 100 atomic %, preferably 80 atomic % or more and less than 100 atomic %, and more preferably 95 atomic % or more and less than 100 atomic %. The Rh content of the Rh alloy used in the protective film 3 is 50 atomic % or more and less than 100 atomic %, preferably 80 atomic % or more and less than 100 atomic %, and more preferably 95 atomic % or more and less than 100 atomic %. In this case, the protective film 3 can be provided with sufficient reflectivity for EUV light, mask cleaning resistance, an etching stopper function when the absorber film 4 is etched, and the function of preventing deterioration of the multilayer reflective film 2 over time.

[0088] The protective film 3 of the multilayer reflective film coated substrate 90 of this embodiment preferably contains the same material as the low refractive index layer 24. Furthermore, the protective film 3 of the multilayer reflective film coated substrate 90 of this embodiment more preferably contains at least one selected from ruthenium (Ru) and rhodium (Rh).

[0089] As described above, the low-refractive index layer 24 preferably contains ruthenium (Ru). Therefore, the protective film 3 also preferably contains the same material (Ru) as the low-refractive index layer 24. In the multilayer reflective film coated substrate 90 of this embodiment, the protective film 3 contains the same material as the low-refractive index layer 24, which is expected to function as part of the multilayer reflective film 2. Therefore, an improvement in the reflectivity of the multilayer reflective film 2 can be expected. Furthermore, by using the same material as the low-refractive index layer 24, the protective film 3 can be more easily formed. It is more preferable that the protective film 3 be made of a material with the same elements and composition ratio as the low-refractive index layer 24.

[0090] The thickness of the protective film 3 is not particularly limited as long as it can function as the protective film 3. From the viewpoint of reflectance of EUV light, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm.

[0091] Any known film formation method can be used without any particular limitation as a method for forming the protective film 3. Specific examples of the method for forming the protective film 3 include ion beam sputtering, magnetron sputtering such as DC sputtering and RF sputtering, chemical vapor deposition (CVD), and vacuum deposition.

[0092] In the multilayer reflective film coated substrate 90 of this embodiment, the protective film 3 may include a Si-containing layer and a protective layer. The Si-containing layer of the protective film 3 is formed on the side that contacts the multilayer reflective film 2, and the protective layer is formed on the Si-containing layer. The protective layer may be made of the same material as the above-mentioned protective film 3, and may be a thin film having the same function as the protective film 3.

[0093] The protective film 3 of the multilayer reflective film coated substrate 90 of this embodiment preferably includes a Si-containing layer on the side in contact with the multilayer reflective film 2. The Si-containing layer preferably includes a silicon (Si) simple substance layer, a SiN material layer containing silicon (Si) and nitrogen (N), a SiC material layer containing silicon (Si) and carbon (C), or a SiNC layer containing silicon (Si), nitrogen (N), and carbon (C). By including a predetermined Si-containing layer (SiN material layer, SiC material layer, or SiNC layer) in the protective film 3, it is possible to prevent Si from diffusing into the protective layer. This makes it possible to prevent the reflectivity of the multilayer reflective film 2 for EUV light from decreasing significantly more than the calculated value.

[0094] The Si-containing layer of the protective film 3 may include multiple layers of different compositions. For example, the Si-containing layer may include two layers: a layer containing Si formed in contact with the multilayer reflective film 2 and a layer containing Si and an additive element formed on the Si-containing layer. The Si-containing layer may be a layer consisting of only Si (Si layer). The layer containing Si and an additive element may be a layer consisting of only Si and an additive element. The additive element is preferably nitrogen (N) and / or carbon (C). The Si-containing layer is more preferably a two-layer structure consisting of a Si layer and a SiN layer, a SiC layer, or a SiNC layer. Alternatively, the Si-containing layer may be a compositionally graded film in which the composition of the additive element increases in the film thickness direction from the multilayer reflective film 2 side to the protective layer side. By having the Si-containing layer consist of a predetermined two-layer structure or a compositionally graded film, diffusion of Si into the protective layer can be suppressed, thereby increasing the reflectivity of the multilayer reflective film 2 for EUV light.

[0095] The SiN material layer is a layer containing silicon (Si) and nitrogen (N). The SiN material layer may further contain other elements, for example, O, C, B, and / or H. The SiN material layer is, for example, silicon nitride (Si ｘ N ｙ (x and y are integers of 1 or more)), and silicon oxynitride (Si ｘ O ｙ N ｚ (x, y, z are integers of 1 or more) The SiN material layer may include at least one material selected from, for example, SiN, Si ３ N ４, and SiON.

[0096] 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 includes, for example, silicon carbide (SiC).

[0097] If Si contained in the Si-containing layer diffuses into the protective layer due to heating during EUV exposure, the metal (e.g., Ru) contained in the protective layer may bond with Si to form metal silicide. If metal silicide is formed in the protective layer, there is a problem that the reflectivity of the multilayer reflective film 2 for EUV light will be significantly lower than the calculated value (the calculated value assuming no Si diffusion). According to the multilayer reflective film-coated substrate 90 of this embodiment, since the Si-containing layer is a SiN material layer or a SiC material layer, the presence of the Si-containing layer can prevent Si from diffusing into the protective layer. Therefore, it is possible to prevent metal silicide (e.g., RuSi) from being formed in the protective layer. As a result, it is possible to prevent the reflectivity of the multilayer reflective film 2 for EUV light from being significantly lower than the calculated value.

[0098] The heating during annealing in manufacturing the reflective mask blank 100 causes oxygen (O ２ ) penetrates the protective layer and bonds with Si, forming SiO ２ In this way, a layer containing SiO may be formed in the protective film 3. ２ When the layer is formed, the blister resistance (H ２ According to the multilayer reflective film coated substrate 90 of this embodiment, the SiO 2 in the protective film 3 is deteriorated. ２ As a result, the blister resistance (H) of the reflective mask 200 in an exposure machine can be improved. ２ This can prevent deterioration of the resistance.

[0099] The N content in the SiN material layer is preferably 5 atomic % to 35 atomic %, more preferably 10 atomic % to 20 atomic %. If the N content in the SiN material layer is less than 5 atomic %, the effect of preventing Si from diffusing into the protective layer cannot be sufficiently obtained. If the N content in the SiN material layer is more than 35 atomic %, the film density of the SiN material layer decreases, and durability and reflectivity are also reduced.

[0100] The C content in the SiC material layer is preferably 10 atomic % to 40 atomic %, more preferably 20 atomic % to 30 atomic %. If the C content in the SiC material layer is less than 10 atomic %, the effect of preventing Si from diffusing into the protective layer cannot be sufficiently obtained. If the C content in the SiC material layer is more than 40 atomic %, the film density of the SiC material layer decreases, and durability is actually deteriorated.

[0101] <Absorber film 4> The reflective mask blank 100 of this embodiment includes an absorber film 4 on the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 described above, or on the protective film 3 formed so as to be in contact with the surface of the multilayer reflective film 2.

[0102] Fig. 3 is a cross-sectional schematic diagram showing an example of a reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Fig. 3 has an absorber film 4 for absorbing EUV light on the multilayer reflective film 2 of the multilayer reflective film-coated substrate 90 shown in Fig. 1. The reflective mask blank 100 may further have another thin film, such as a resist film 11, on the absorber film 4. In the structure shown in Fig. 3, the uppermost layer of the multilayer reflective film 2 may be a low refractive index layer 24 containing Ru.

[0103] Fig. 4 is a cross-sectional schematic diagram showing an example of a reflective mask blank 100 of this embodiment. The reflective mask blank 100 shown in Fig. 4 has an absorber film 4 for absorbing EUV light on the protective film 3 of the multilayer reflective film-coated substrate 90 shown in Fig. 2. The reflective mask blank 100 can further have another thin film, such as a resist film 11, on the absorber film 4.

[0104] Fig. 5 is a cross-sectional schematic diagram showing another example of the reflective mask blank 100 of this embodiment. As shown in Fig. 5, the reflective mask blank 100 can have an etching mask film 6 on an absorber film 4. The reflective mask blank 100 can further have another thin film, such as a resist film 11, on the etching mask film 6.

[0105] In the reflective mask blank 100 of this embodiment, the absorber film 4 can absorb EUV light, and therefore the reflective mask 200 (EUV mask) of the present invention can be manufactured by patterning the absorber film 4 of the reflective mask blank 100. The reflective mask blank 100 of this embodiment can provide a reflective mask blank 100 having a shallow effective reflection surface and a multilayer reflective film 2 that can suppress the phenomenon of diffusion of material atoms between the low refractive index layer 24 and the high refractive index layer 22.

[0106] The basic function of the absorber film 4 is to absorb EUV light. The absorber film 4 may be an absorber film 4 intended for absorbing EUV light, or an absorber film 4 having a phase shift function that also takes into account the phase difference of EUV light. The absorber film 4 having a phase shift function absorbs EUV light and reflects a portion of the EUV light to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 4 having a phase shift function, the portion where the absorber film 4 is formed absorbs and attenuates EUV light while reflecting a portion of the light at a level that does not adversely affect pattern transfer. Furthermore, in a region (field portion) where the absorber film 4 is not formed, the EUV light is reflected by the multilayer reflective film 2 (via the protective film 3, if present). Therefore, a desired phase difference is generated between the light reflected from the absorber film 4 having a phase shift function and the light reflected from the field portion. The absorber film 4 having a phase shift function is preferably formed so that the phase difference between the reflected light from the absorber film 4 and the reflected light from the multilayer reflective film 2 is 170 to 260 degrees. The light beams with inverted phase differences interfere with each other at the pattern edge, improving the image contrast of the projected optical image. This improvement in image contrast increases the resolution, and makes it possible to increase various latitudes related to exposure, such as exposure dose latitude and focus latitude.

[0107] The absorber film 4 may be a single-layer film or a multilayer film consisting of multiple films (e.g., a lower-layer absorber film and an upper-layer absorber film). In the case of a single-layer film, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constants and film thickness of the upper-layer absorber film can be appropriately set so that it serves as an anti-reflection film during optical mask pattern defect inspection. This improves inspection sensitivity during optical mask pattern defect inspection. Furthermore, using a film containing oxygen (O) or nitrogen (N), which improves oxidation resistance, as the upper-layer absorber film improves stability over time. Thus, by forming the absorber film 4 into a multilayer film, various functions can be added to the absorber film 4. When the absorber film 4 has a phase shift function, forming it into a multilayer film can increase the range of optical adjustment, making it easier to obtain the desired reflectance.

[0108] The material of the absorber film 4 is not particularly limited as long as it has the 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 relative to the protective film 3. As a material having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), an alloy containing two or more metals, or a compound thereof can be preferably used. The compound may contain oxygen (O), nitrogen (N), carbon (C), and / or boron (B) in addition to the above metal or alloy.

[0109] The absorber film 4 can be formed by magnetron sputtering such as DC sputtering or RF sputtering. For example, the absorber film 4 made of a tantalum compound or the like can be formed by reactive sputtering using a target containing tantalum and boron and argon gas to which oxygen or nitrogen has been added.

[0110] Furthermore, in terms of smoothness and flatness, the crystalline state of the absorber film 4 is preferably an amorphous or microcrystalline structure. If the surface of the absorber film 4 is not smooth or flat, the edge roughness of the absorber pattern 4 a increases, which may result in poor dimensional accuracy of the pattern. The surface roughness of the absorber film 4 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in root mean square roughness (Rms).

[0111] 5 , the reflective mask blank 100 of this embodiment can have an etching mask film 6 on the absorber film 4. As a material for the etching mask film 6, it is preferable to use a material that has a high etching selectivity of the absorber film 4 to the etching mask film 6 (etching rate of the absorber film 4 / etching rate of the etching mask film 6). The etching selectivity of the absorber film 4 to the etching mask film 6 is preferably 1.5 or more, and more preferably 3 or more.

[0112] The reflective mask blank 100 of this embodiment preferably has an etching mask film 6 on the absorber film 4 .

[0113] Chromium or a chromium compound is preferably used as the material for the etching mask film 6. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. The etching mask film 6 more preferably contains CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and further preferably is a CrO-based film containing chromium and oxygen (a CrO film, a CrON film, a CrOC film, or a CrOCN film).

[0114] Tantalum or a tantalum compound is preferably used as the material of the etching mask film 6. Examples of tantalum compounds include a material containing Ta and at least one element selected from N, O, B, and H. More preferably, the etching mask film 6 contains TaN, TaO, TaON, TaBN, TaBO, or TaBON.

[0115] Silicon or a silicon compound is preferably used as the material for the etching mask film 6. Examples of silicon compounds include a material containing Si and at least one element selected from N, O, C, and H, as well as metal silicon (metal silicide) and metal silicon compounds (metal silicide compounds) containing a metal in silicon or a silicon compound. Examples of metal silicon compounds include a material containing a metal, Si, and at least one element selected from N, O, C, and H.

[0116] The thickness of the etching mask film 6 is preferably 3 nm or more in order to form a pattern with high precision in the absorber film 4. Moreover, the thickness of the etching mask film 6 is preferably 15 nm or less in order to make the thickness of the resist film 11 thin.

[0117] <Back Surface Conductive Film 5> A back surface conductive film 5 for electrostatic chucks can be formed on the back surface of the substrate 10 (the surface opposite to the surface on which the multilayer reflective film 2 is formed). The sheet resistance required for the back surface conductive film 5 for electrostatic chucks is typically 100 Ω / □ (Ω / square) or less. The back surface conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material for the back surface conductive film 5 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material for the back surface conductive film 5 is preferably a Cr compound containing Cr and at least one element selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the back surface conductive film 5 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.

[0118] The thickness of the back surface conductive film 5 is not particularly limited as long as it functions as a film for an electrostatic chuck, and is, for example, 10 nm to 200 nm.

[0119] <Reflective Mask 200> As shown in FIG. 6D, the reflective mask 200 of this embodiment includes an absorber pattern 4a obtained by patterning the absorber film 4 of the reflective mask blank 100 described above.

[0120] 6A to 6D are schematic diagrams showing an example of a method for manufacturing a reflective mask 200. The reflective mask blank 100 of this embodiment described above can be used to manufacture the reflective mask 200 of this embodiment. An example of the method for manufacturing the reflective mask 200 will be described below.

[0121] First, a reflective mask blank 100 is prepared, which includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, a protective film 3 formed on the multilayer reflective film 2, and an absorber film 4 formed on the protective film 3. Next, a resist film 11 is formed on the absorber film 4 to obtain a reflective mask blank 100 with the resist film 11 (FIG. 6A). A pattern is written on the resist film 11 using an electron beam lithography device, and a developing and rinsing process is then performed to form a resist pattern 11a (FIG. 6B).

[0122] Using the resist pattern 11a as a mask, the absorber film 4 is dry-etched, whereby the portions of the absorber film 4 that are not covered by the resist pattern 11a are etched, and an absorber pattern 4a is formed (FIG. 6C).

[0123] As an etching gas for the absorber film 4, for example, a fluorine-based gas and / or a chlorine-based gas can be used. As the fluorine-based gas, CF ４ , CHF ３ , C ２ F ６ , C ３ F ６ , C ４ F ６ , C ４ F ８ , C.H. ２ F ２ , C.H. ３ F, C ３ F ８ , SF ６ , and F ２ The chlorine-based gas may be Cl ２ , SiCl ４ , CHCl ３ , CCl ４ , and BCl ３ In addition, a fluorine-based gas and / or a chlorine-based gas and O ２In this case, a mixed gas containing a predetermined ratio of these may be used. These etching gases may further contain an inert gas such as He and / or Ar, if necessary.

[0124] After the absorber pattern 4a is formed, the resist pattern 11a is removed with a resist remover solution, and after the resist pattern 11a is removed, a wet cleaning process using an acidic or alkaline aqueous solution is performed to obtain the reflective mask 200 of this embodiment (FIG. 6D).

[0125] In addition, when a reflective mask blank 100 in which an etching mask film 6 is formed on an absorber film 4 is used, an additional process is performed in which a pattern (etching mask pattern) is formed on the etching mask film 6 using the resist pattern 11a as a mask, and then a pattern is formed on the absorber film 4 using the etching mask pattern as a mask.

[0126] The reflective mask 200 thus obtained has a structure in which a multilayer reflective film 2, a protective film 3, and an absorber pattern 4a are laminated on a substrate 1.

[0127] The exposed region of the multilayer reflective film 2 (including the protective film 3) has the function of reflecting EUV light. The region of the multilayer reflective film 2 (including the protective film 3) covered with the absorber pattern 4 a has the function of absorbing EUV light. The reflective mask 200 of this embodiment has a shallow effective reflective surface and includes a multilayer reflective film 2 that can suppress the phenomenon of diffusion of material atoms between the low refractive index layer 24 and the high refractive index layer 22. Therefore, by using the reflective mask 200 of this embodiment, it is possible to transfer a finer pattern onto a transfer target.

[0128] <Method for Manufacturing Semiconductor Device> The method for manufacturing a semiconductor device according to this embodiment includes a step of performing a lithography process using an exposure apparatus and the above-described reflective mask 200 to form a transfer pattern on a transfer target object.

[0129] A transfer pattern can be formed on a semiconductor substrate 60 (transfer receiving body) by lithography using the reflective mask 200 of this embodiment. This transfer pattern has a shape that is the result of transferring the pattern of the reflective mask 200. By forming a transfer pattern on the semiconductor substrate 60 using the reflective mask 200, a semiconductor device can be manufactured.

[0130] According to this embodiment, a semiconductor device can be manufactured using a reflective mask 200 having a shallow effective reflection surface and including a multilayer reflective film 2 that can suppress the phenomenon of diffusion of material atoms between the low refractive index layer 24 and the high refractive index layer 22. Therefore, by using the reflective mask 200 of this embodiment, it is possible to manufacture semiconductor devices with higher density and precision.

[0131] A method for transferring a pattern onto a semiconductor substrate 60 with a resist by using EUV light will be described with reference to FIG.

[0132] 13 shows a schematic configuration of an EUV exposure apparatus 50, which is an apparatus for transferring a transfer pattern onto a resist film formed on a semiconductor substrate 60. The EUV exposure apparatus 50 includes an EUV light generation unit 51, an irradiation optical system 56, a reticle stage 58, a projection optical system 57, and a wafer stage 59, which are precisely arranged along the optical path axis of the EUV light. The container of the EUV exposure apparatus 50 is filled with hydrogen gas.

[0133] The EUV light generation unit 51 has a laser light source 52, a tin droplet generation unit 53, a capture unit 54, and a collector 55. When the high-power carbon dioxide laser from the laser light source 52 irradiates the tin droplets emitted from the tin droplet generation unit 53, the tin droplets are converted into plasma, and EUV light is generated. The generated EUV light is collected by the collector 55 and passes through an irradiation optical system 56 to be incident on a reflective mask 200 set on a reticle stage 58. The EUV light generation unit 51 generates EUV light with a wavelength of, for example, 13.53 nm.

[0134] The EUV light reflected by the reflective mask 200 is reduced by the projection optical system 57 to a pattern image light, typically about one-fourth the original size, and projected onto the semiconductor substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred onto a resist film on the semiconductor substrate 60. A resist pattern can be formed on the semiconductor substrate 60 by developing the exposed resist film. An integrated circuit pattern can be formed on the semiconductor substrate 60 by etching the semiconductor substrate 60 using the resist pattern as a mask. A semiconductor device is manufactured through these and other necessary processes.

[0135] Examples and comparative examples will be described below with reference to the drawings.

[0136] (Fabrication of Multilayer Reflective Film-Coated Substrate 90 in Examples 1 to 8) First, a substrate 1 having a size of 6025 (approximately 152 mm×152 mm×6.35 mm) and having a polished first main surface and a polished second main surface was prepared. This substrate 1 was made of low thermal expansion glass (SiO ２ -TiO ２ The substrate 1 is made of a glass (based glass). The main surface of the substrate 1 is polished by a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process.

[0137] Next, a multilayer reflective film 2 (see FIG. 8 ) consisting of a high-refractive-index layer 22, an intermediate layer 26, and a low-refractive-index layer 24 was formed on the main surface (first main surface) of the substrate 1. The high-refractive-index layer 22 in Examples 1 to 8 was made of Si, and the low-refractive-index layer 24 was made of Ru. Table 1 shows the material and film thickness of the intermediate layer 26 in Examples 1 to 8. The "Additive element content (atomic %) in the multilayer reflective film" in Table 1 also shows the type of additive element added when forming the intermediate layer 26, and the content (atomic %) of the additive element in the multilayer reflective film 2.

[0138] The multilayer reflective film 2 was formed by alternately laminating high-refractive index layers 22, intermediate layers 26, and low-refractive index layers 24 on the substrate 1 using a DC magnetron sputtering method (reactive sputtering method) in a predetermined gas atmosphere using a Si target and a Ru target. First, a high-refractive index layer 22 made of a Si film was formed in a Kr gas atmosphere using a Si target so as to have the film thickness shown in Table 1, so as to be in contact with the main surface of the substrate 1.

[0139] Next, the intermediate layer 26 was formed to have the thickness shown in Table 1. As shown in Table 1, a SiN film and a SiC film were used as the intermediate layer 26. The SiN film was formed by using Kr gas and N ２ The SiC film was formed using a SiC target in a Kr gas atmosphere.

[0140] Next, a low refractive index layer 24 made of a Ru film was formed using a Ru target in a Kr gas atmosphere to a thickness of 2.8 nm.

[0141] The film was formed by laminating 35 periods (sets) of one high refractive index layer 22, one intermediate layer 26 and one low refractive index layer 24 on the main surface of the substrate 1, with one period (set) being one period.

[0142] Next, a protective film 3 consisting of a Si-containing layer and a protective layer was formed on the multilayer reflective film 2 of Examples 1 to 8.

[0143] As shown in Table 1, the Si-containing layer of the protective film 3 in Examples 1 to 6 was made of a Si film. The Si film was formed to a thickness of 3.5 nm by DC magnetron sputtering using a Si target in a Kr gas atmosphere.

[0144] As shown in Table 1, the Si-containing layer of Example 7 is composed of two layers, a Si film and a SiN film. First, a Si film was formed on the multilayer reflective film 2. The Si film was formed to a thickness of 3.2 nm by DC magnetron sputtering using a Si target in a Kr gas atmosphere. Next, a SiN film was formed. The SiN film was formed by sputtering in a Kr gas atmosphere and N ２A film having a thickness of 0.3 nm was formed by DC magnetron sputtering (reactive sputtering) using a Si target in a mixed gas atmosphere.

[0145] As shown in Table 1, the Si-containing layer of Example 8 consisted of two layers: a Si film and a SiC film. First, a Si film was formed on the multilayer reflective film 2. The Si film was formed to a thickness of 2.9 nm by DC magnetron sputtering using a Si target in a Kr gas atmosphere. Next, a SiC layer was formed. The SiC film was formed to a thickness of 0.6 nm by DC magnetron sputtering using a SiC target in a Kr gas atmosphere.

[0146] Next, a Ru film was formed as a protective layer on the Si-containing layer using a Ru target in a Kr gas atmosphere to a thickness of 3.5 nm.

[0147] In this manner, the multilayer reflective film coated substrates 90 of Examples 1 to 8 were manufactured.

[0148] (Production of multilayer reflective film coated substrate 90 of Comparative Example 1) A multilayer reflective film coated substrate 90 of Comparative Example 1 was produced in the same manner as in Example 1, except that the intermediate layer 26 of the multilayer reflective film 2 was not formed. In Comparative Example 1, the film thickness of the high refractive index layer was 4.2 nm, and the film thickness of one period of the multilayer reflective film was 7 nm, the same as in Example 1.

[0149] (Evaluation of Multilayer Reflective Film-Coated Substrate 90) A cross section of a multilayer reflective film 2 manufactured under the same conditions as the multilayer reflective film 2 of Examples 1 to 8 was observed with a transmission electron microscope (TEM). As a result of the TEM observation, it was confirmed that an intermediate layer 26 was formed between the high refractive index layer 22 and the low refractive index layer 24 of the multilayer reflective film 2 of Examples 1 to 8. Table 1 shows the content of the additive element in the multilayer reflective film 2 measured by energy dispersive X-ray analysis (EDX). The content of the additive element in the multilayer reflective film 2 was measured by measuring the maximum value of the additive element in a line profile in the cross-sectional direction by TEM-EDX analysis excluding the surface 5 nm of the multilayer reflective film 2.

[0150] Using the multilayer reflective film coated substrates 90 of the example and comparative example prepared as described above, changes in reflectance due to heat treatment of the multilayer reflective film coated substrates 90 were measured.

[0151] Specifically, first, the reflectivity (R1, unit: %) of the multilayer reflective film-coated substrate 90 of the example and comparative example to EUV light (wavelength 13.5 nm) was measured. Next, the multilayer reflective film-coated substrate 90 was heat-treated by heating it in an air atmosphere at 200°C for 10 minutes. After the heat treatment of the multilayer reflective film-coated substrate 90, the reflectivity (R2, unit: %) of the multilayer reflective film-coated substrate 90 to EUV light was measured. The change in EUV reflectivity of the multilayer reflective film-coated substrate 90 due to the heat treatment was obtained by subtracting the reflectivity (R2) of the multilayer reflective film-coated substrate 90 after the heat treatment from the reflectivity (R1) of the multilayer reflective film-coated substrate 90 before the heat treatment. Table 1 shows the change in EUV reflectivity due to the heat treatment.

[0152] As shown in Table 1, in the multilayer reflective film coated substrates 90 of Examples 1 to 8, the change in reflectivity for EUV light before and after heat treatment at 200°C for 10 minutes was 1.1% or less (Example 4). The multilayer reflective film 2 of Examples 1 to 8 includes a predetermined intermediate layer 26, which suppresses the diffusion of Si from the high refractive index layer 22 to the low refractive index layer 24. This is presumably why the change in reflectivity before and after heat treatment was small. In particular, the change in reflectivity in Examples 2, 3, and 7, in which the intermediate layer 26 was made of SiN, was small at 0.1%.

[0153] On the other hand, in the multilayer reflective film-coated substrate 90 of Comparative Example 1, the reflectivity of the multilayer reflective film-coated substrate 90 for EUV light changed significantly before and after the heat treatment at 200° C. for 10 minutes compared to Examples 1 to 8. In Comparative Example 1, it is presumed that the reflectivity changed significantly because Si diffused from the high refractive index layer 22 to the low refractive index layer 24, resulting in the formation of metal silicide (RuSi) in the high refractive index layer 22.

[0154] (Reflective Mask Blank 100) Next, the reflective mask blank 100 of Examples 1 to 8 will be described.

[0155] A back surface conductive film 5 was formed on the back surface of the substrate 1 of the multilayer reflective film coated substrate 90 manufactured as described above, and an absorber film 4 was formed on the protective film 3, thereby manufacturing the reflective mask blanks 100 of Examples 1 to 8.

[0156] First, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the substrate 1 of the multilayer reflective film coated substrate 90 by magnetron sputtering (reactive sputtering) under the following conditions: Conditions for forming the back surface conductive film 5: Cr target, Ar and N ２ A mixed gas atmosphere (Ar: 90%, N: 10%), film thickness 20 nm.

[0157] Next, a TaBN film having a thickness of 55 nm was formed as an absorber film 4 on the protective film 3 of the multilayer reflective film-coated substrate 90. The composition of the absorber film 4 was Ta:B:N=75:12:13 (atomic ratio), and the film thickness was 55 nm.

[0158] In this manner, the reflective mask blanks 100 of Examples 1 to 8 were manufactured.

[0159] (Reflective Mask 200) Next, a reflective mask 200 was manufactured using the reflective mask blanks 100 of Examples 1 to 8. The manufacture of the reflective mask 200 will be described with reference to Figures 6A to 6D.

[0160] First, as shown in Fig. 6A, a resist film 11 was formed on the absorber film 4 of the reflective mask blank 100. Then, a desired pattern such as a circuit pattern was drawn (exposed) on this resist film 11, and then developed and rinsed to form a predetermined resist pattern 11a (Fig. 6B). Next, using the resist pattern 11a as a mask, the absorber film 4 (TaBN film) was etched with Cl ２ Dry etching was performed using a gas to form an absorber pattern 4a (FIG. 6C), after which the resist pattern 11a was removed (FIG. 6D).

[0161] Finally, wet cleaning was performed using deionized water (DIW), and the reflective masks 200 of Examples 1 to 8 were manufactured.

[0162] (Manufacturing of Semiconductor Device) The reflective mask 200 of Examples 1 to 8 was set in an EUV scanner, and EUV exposure was performed on a wafer having a processed film and a resist film formed on a semiconductor substrate 60, which was a transfer object. Then, by developing this exposed resist film, a resist pattern was formed on the semiconductor substrate 56 on which the processed film was formed.

[0163] The reflective masks 200 of Examples 1 to 8 have a shallow effective reflective surface and a multilayer reflective film 2 that can suppress the phenomenon of diffusion of material atoms between the low refractive index layer and the high refractive index layer, and therefore were able to form a fine and highly accurate transfer pattern (resist pattern) on the semiconductor substrate 60 (transferred substrate).

[0164] This resist pattern is transferred to the film to be processed by etching, and then various processes such as forming insulating and conductive films, introducing dopants, and annealing are carried out, allowing semiconductor devices with the desired characteristics to be manufactured with a high yield.

[0165]

[0166] REFERENCE SIGNS LIST 1 substrate 2 multilayer reflective film 3 protective film 4 absorber film 4a absorber pattern 5 back surface conductive film 6 etching mask film 11 resist film 11a resist pattern 22 high refractive index layer 24 low refractive index layer 26 intermediate layer 50 EUV exposure device 51 EUV light generation unit 52 laser light source 53 tin droplet generation unit 54 capture unit 55 collector 56 irradiation optical system 57 projection optical system 58 reticle stage 59 wafer stage 60 semiconductor substrate 90 substrate with multilayer reflective film 100 reflective mask blank 200 reflective mask

Claims

1. A substrate with a multilayer reflective film, comprising a substrate and a multilayer reflective film provided on the substrate, wherein the multilayer reflective film includes a multilayer film formed by alternately laminating a low refractive index layer and a high refractive index layer containing silicon (Si), the multilayer reflective film further includes at least one intermediate layer disposed between the low refractive index layer and the high refractive index layer, the multilayer reflective film contains at least one additive element selected from nitrogen (N), carbon (C), and oxygen (O), and a content of the additive element in the multilayer reflective film is 40 atomic% or less. A substrate with a multilayer reflective film is characterized by this.

2. The substrate with a multilayer reflective film according to claim 1, wherein the content of the additive element is 1 atomic% or more.

3. The substrate with a multilayer reflective film according to claim 1, wherein the intermediate layer contains silicon (Si) and the additive element.

4. The substrate with a multilayer reflective film according to claim 1, wherein the intermediate layer contains at least one selected from SiN, SiO, SiC, SiON, SiCN, SiOC, and SiOCN.

5. The additive element contains nitrogen (N), and the substrate with a multilayer reflective film according to claim 1, wherein a content of the nitrogen (N) is 5 atomic% or more and 20 atomic% or less.

6. The additive element contains carbon (C), and the substrate with a multilayer reflective film according to claim 1, wherein a content of the carbon (C) is 10 atomic% or more and 30 atomic% or less.

7. The additive element contains oxygen (O), and the substrate with a multilayer reflective film according to claim 1, wherein a content of the oxygen (O) is 3 atomic% or more and 15 atomic% or less.

8. The substrate with a multilayer reflective film according to claim 1, wherein the low refractive index layer contains ruthenium (Ru).

9. The low refractive index layer contains ruthenium (Ru), and when a lamination structure of one low refractive index layer and one high refractive index layer is defined as one cycle, the lamination structure is less than 40 cycles. The substrate with a multilayer reflective film according to claim 1 is characterized by this.

10. The substrate with a multilayer reflective film according to any one of claims 1 to 9, having a protective film on the multilayer reflective film.

11. The substrate with a multilayer reflective film according to claim 10, wherein the protective film includes a SiN material layer containing silicon (Si) and nitrogen (N) or a SiC material layer containing silicon (Si) and carbon (C) on a side in contact with the multilayer reflective film.

12. A reflective mask blank, comprising an absorber film on the protective film of the substrate with a multilayer reflective film according to Claim 10.

13. A reflective mask, comprising an absorber pattern obtained by patterning the absorber film of the reflective mask blank according to Claim 12.

14. 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 13 to form a transfer pattern on a transfer target.