Manufacturing methods for substrates with multilayer reflective films, reflective mask substrates, reflective masks, and semiconductor devices.

Abstract

A substrate with a multilayer reflective film is provided. The multilayer reflective film has a shallow effective reflective surface, which can suppress the diffusion of atoms as materials between a low-refractive-index layer and a high-refractive-index layer. The substrate with the multilayer reflective film has a substrate and a multilayer reflective film disposed on the substrate. The multilayer reflective film comprises a multilayer film with alternating layers of a low-refractive-index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high-refractive-index layer containing silicon (Si). The low-refractive-index layer further contains additive elements with a work function in the range of greater than 3.7 eV but less than 4.7 eV.

Description

[Technical Field]

[0001] This invention relates to a substrate with a multilayer reflective film, a reflective shield substrate, a reflective shield, and a method for manufacturing a semiconductor device. [Previous Technology]

[0002] With the increasing demands for density and precision in ultra-low light (ULS) devices in recent years, an exposure technique using extreme ultraviolet (EUV) light, namely EUV lithography, has been proposed.

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

[0004] As an example of a reflective mask substrate for manufacturing a reflective mask, Patent Document 1 describes an EUV blank mask comprising a substrate, a reflective film deposited on the substrate, and an absorbent film deposited on the reflective film. Patent Document 1 describes the reflective film having a structure in which a first layer and a second layer are deposited multiple times, the first layer being composed of Ru, or being composed of Ru compound containing one or more elements selected from Mo, Nb, and Zr, and the second layer being composed of Si.

[0005] Patent Document 2 discloses a multilayer reflector for soft X-ray / vacuum ultraviolet light, which has a multilayer thin film structure composed of alternating layers of two main materials, A and B, with different refractive indices. Patent Document 2 discloses that at least one or more sub-material thin films with the function of reducing wrinkles at the lamination interface are deposited between each AB layer and / or between BA layers to form a periodic structure. Patent Document 2 discloses that the low refractive index layer is generally formed of high-melting-point metal materials such as tungsten and molybdenum or compounds with such as the main component, and the high refractive index layer is generally formed of light elements such as carbon, silicon, boron, and beryllium or compounds with such as the main component. Furthermore, Patent Document 2 describes examples of conductors or compounds of light elements with atomic numbers 13 or less, such as carbon (C), boron (B), beryllium (Be), silicon carbide (SiC), silicon nitride (Si3N4), silicon oxide (SiO2), boron nitride (BN), boron carbide (B4C), and aluminum nitride (AlN).

[0006] Patent Document 3 discloses a multilayer film beam-splitting mirror that uses a compound interlayer composed of Si and C as the intermediate layer between the heavy element layer and the light element layer of a multilayer film beam-splitting element with Bragg diffraction effect. Furthermore, Patent Document 3 discloses a method for fabricating a multilayer film using Mo, Ru, Rh, and Re as the heavy element layer, Si as the light element layer, and Si 100-xC x as the intermediate layer.

[0007] Patent Document 4 discloses a multilayer X-ray reflector having a plurality of material layers periodically deposited. Patent Document 4 discloses forming an intermediate layer between the material layers, and using a material with a melting point higher than at least one of the aforementioned material layers as the intermediate layer. Furthermore, Patent Document 4 discloses using Mo as a heavy element layer and Si as a light element layer to fabricate a Mo / Si multilayer film.

[0008] Non-Patent Document 1 describes the use of B4C interlayers in a Mo / Si multilayer reflector. Furthermore, Non-Patent Document 1 describes the use of a Ru / Si multilayer reflector as a multilayer reflector.

[0009] [Prior Art Documents] [Patent Documents] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-110953 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2-242201 Patent Document 3: Japanese Unexamined Patent Application Publication No. 5-203798 Patent Document 4: Japanese Unexamined Patent Application Publication No. 9-230098

[0010] [Non-Patent Literature] Non-Patent Literature 1: 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) [Summary of the Invention]

[0011] The above-mentioned EUV lithography is an exposure technique using extreme ultraviolet light (EUV light). 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 0.2~100nm. EUV lithography can use EUV light with a wavelength of 13~14nm (e.g., wavelength 13.5nm).

[0012] In EUV lithography, a reflective mask with an absorber pattern is used. EUV light irradiated by the reflective mask is absorbed in the areas with the absorber pattern and reflected in the areas without the absorber pattern. The areas without the absorber pattern expose a multilayer reflective film. The exposed multilayer reflective film reflects EUV light. In EUV lithography, the light image reflected by the multilayer reflective film (the areas without the absorber pattern) is transferred onto a semiconductor substrate (the substrate to be transferred) such as a silicon wafer through a reflective optical system.

[0013] As a multilayer reflective film, it is generally used to periodically laminate multiple layers of elements with different refractive indices. For example, as a multilayer reflective film for EUV light with a wavelength of 13~14nm (e.g., wavelength 13.5nm), it is used to alternately laminate a Mo / Si periodic film with 40~60 periods of low refractive index Mo film and high refractive index Si film.

[0014] In order to achieve high density and high precision of semiconductor devices by using reflective masks, the reflective area (the surface of the multilayer reflective film) in the reflective mask must have high reflectivity relative to the EUV light that is the exposure light.

[0015] As the minimum linewidth of the nodes transferred onto the semiconductor substrate and other transfer objects becomes narrower, the impact of the 3D effect on the transfer characteristics also increases. 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 used to form the absorber pattern is insufficient. Therefore, the reflective surface reflecting EUV light must also be controlled. Specifically, the reflective surface is controlled in such a way that the effective reflective surface of the multilayer reflective film is as close to the surface as possible to prevent the EUV light reflected from the multilayer reflective film from diffusing. In this specification, the effective reflective surface closer to the surface of the multilayer reflective film is sometimes referred to as a "shallow effective reflective surface." By having a shallow effective reflective surface, the multilayer reflective film can suppress the 3D effect and reduce the number of layers.

[0016] To make the effective reflective surface of the multilayer reflective film as close as possible to the surface, the material of the multilayer reflective film must be selected to increase the reflectivity of EUV light. Multilayer reflective films reflect EUV light through a stacked structure of low-refractive-index layers and high-refractive-index layers. When selecting materials for the multilayer reflective film to increase the reflectivity of EUV light, the atoms of the material may diffuse between the low-refractive-index and high-refractive-index layers. If this diffusion phenomenon occurs, the reflectivity of the multilayer reflective film will decrease.

[0017] Therefore, the object of the present invention is to provide a substrate with a multilayer reflective film, a reflective shield substrate, and a reflective shield, wherein the multilayer reflective film has a shallow effective reflective surface and can suppress the diffusion of atoms as materials between low-refractive-index layers and high-refractive-index layers. Furthermore, the object of the present invention is to provide a method for manufacturing a semiconductor device using the above-mentioned reflective shield.

[0018] To solve the above-mentioned problems, the present invention has the following structure.

[0019] (Structure 1) The present invention comprises a substrate with a multilayer reflective film, having a substrate and a multilayer reflective film disposed on the substrate; the multilayer reflective film comprises a multilayer film having an alternatingly deposited low refractive index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high refractive index layer containing silicon (Si); the low refractive index layer further contains an additive element having a work function in the range of greater than 3.7 eV but less than 4.7 eV.

[0020] (Structure 2) The structure 2 of the present invention is the substrate with a multilayer reflective film as in the structure 1, wherein the low refractive index layer contains at least one additive element selected from thallium (Tl), hafnium (Hf), titanium (Ti), zirconium (Zr), manganese (Mn), indium (In), gallium (Ga), cadmium (Cd), bismuth (Bi), tantalum (Ta), lead (Pb), silver (Ag), aluminum (Al), vanadium (V), niobium (Nb), tin (Sn), zinc (Zn), mercury (Hg), chromium (Cr), iron (Fe), antimony (Sb), tungsten (W), molybdenum (Mo), and copper (Cu).

[0021] (Structure 3) The structure 3 of the present invention is a substrate with a multilayer reflective film as in structure 1 or 2, wherein when the stacked structure of the low refractive index layer and the high refractive index layer is taken as 1 period, the stacked structure is less than 40 periods.

[0022] (Construction 4) The present invention is a substrate with a multilayer reflective film as in any of the constructions 1 to 3, wherein a protective film is provided on the multilayer reflective film.

[0023] (Structure 5) The structure 5 of the present invention is the same as the substrate with a multilayer reflective film as the structure 4, wherein the protective film contains the same material as the low refractive index layer.

[0024] (Structure 6) The structure 6 of the present invention is a substrate with a multilayer reflective film as in structure 4 or 5, wherein the protective film contains at least one additive element selected from ruthenium (Ru) and rhodium (Rh) that is the same as that of the low refractive index layer.

[0025] (Structure 7) The present invention comprises a reflective shielding substrate having an absorber film on the protective film of a substrate with a multilayer reflective film as described in any of the configurations 4 to 6.

[0026] (Structure 8) The present invention is a reflective shielding substrate, which has an absorber film on the multilayer reflective film of a substrate with a multilayer reflective film as in any of the configurations 1 to 3.

[0027] (Structure 9) The present invention is a reflective mask having an absorber pattern that patterns the absorber film of the reflective mask substrate such as the structure 7 or 8.

[0028] (Structure 10) The structure 10 of the present invention is a method for manufacturing a semiconductor device, which includes a process of using a reflective mask as in Structure 9 to perform a photolithography process using an exposure device to form a transfer pattern on a transfer object.

[0029] According to the present invention, a substrate with a multilayer reflective film, a reflective shield substrate, and a reflective shield are provided. The multilayer reflective film has a shallow effective reflective surface, which can suppress the diffusion of atoms as materials between low-refractive-index layers and high-refractive-index layers. Furthermore, according to the present invention, a method for manufacturing a semiconductor device using the above-mentioned reflective shield is provided.

Implementation Method

[0031] Hereinafter, embodiments of the present invention will be specifically described with reference to drawings. Furthermore, the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] FIG1 is a cross-sectional schematic diagram showing an example of a substrate 90 with a multilayer reflective film according to this embodiment. The substrate 90 with a multilayer reflective film according to this embodiment includes a substrate 1 and a multilayer reflective film 2 disposed on the substrate 1. The multilayer reflective film 2 includes a multilayer film having a specific low refractive index layer and a specific high refractive index layer alternately deposited. An inner conductive film 5 for an electrostatic clamp can be formed on the inner surface of the substrate 1 (the side opposite to the side where the multilayer reflective film 2 is formed).

[0033] FIG2 is a cross-sectional schematic diagram showing another example of a substrate 90 with a multilayer reflective film according to this embodiment. The substrate 90 with a multilayer reflective film shown in FIG2 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. An inner conductive film 5 for an electrostatic clamp can be formed on the inner surface of the substrate 1 (the side opposite to the side where the multilayer reflective film 2 is formed).

[0034] In this specification, "the thin film B is disposed (formed) on the thin film A (or substrate)" means not only that the thin film B is disposed (formed) by being in contact with the surface of the thin film A (or substrate), but also that there is another thin film C between the thin film A (or substrate) and the thin film B. Furthermore, in this specification, for example, "the thin film B is disposed by being in contact with the surface of the thin film A (or substrate)" means that there is no other thin film between the thin film A (or substrate) and the thin film B, and the thin film A (or substrate) and the thin film B are directly in contact. Also, in this specification, "above" does not necessarily refer to the upper side in the vertical direction. "Above" simply indicates the relative positional relationship of the thin film and the substrate, etc.

[0035] The substrate 90 with a multilayer reflective film of this embodiment will be specifically described.

[0036] <Substrate 1> In order to prevent the transfer pattern from deforming due to heat during exposure to EUV light, it is preferable to use a material with a low coefficient of thermal expansion in the range of 0±5 ppb / ℃. As a material with a low coefficient of thermal expansion in this range, such as SiO2-TiO2 based glass, multi-component glass ceramics, etc. can be used.

[0037] The main surface (first main surface) of the substrate 1 on the side where the transfer pattern (absorber pattern 4a described later) is formed is preferably processed to improve flatness. By improving the flatness of the main surface of the substrate 1, the positional accuracy or transfer accuracy of the pattern can be improved. For example, in the case of EUV exposure, in the 132mm × 132mm area of ​​the main surface of the substrate 1 on the side where the transfer pattern is formed, the flatness is preferably 0.1μm or less, more preferably 0.05μm or less, and particularly preferably 0.03μm or less. Furthermore, the second main surface (inner surface) on the opposite side from the side where the transfer pattern is formed is fixed to the surface of the exposure apparatus by means of an electrostatic clamp. In the 142mm × 142mm area of ​​the inner surface, the flatness is 0.1μm or less, more preferably 0.05μm or less, and particularly preferably 0.03μm or less. Furthermore, in this specification, flatness is a value representing the deflection (deformation) of a surface as expressed in TIR (Total Indicated Reading). Flatness (TIR) ​​is the absolute value of the height difference between the highest position on the surface of the substrate 1 above the focal plane, which is defined by the least flat method, and the lowest position on the surface of the substrate 1 below the focal plane, with the surface of the substrate 1 as a reference.

[0038] In the case of EUV exposure, the surface roughness of the main surface of the substrate 1 on the side where the transfer pattern is formed is preferably below 0.1 nm in terms of root mean square roughness (Rq). In addition, the surface roughness can be measured by atomic force microscopy.

[0039] To prevent the substrate 1 from deforming due to the film stress of the thin film (multilayer reflective film 2, etc.) formed thereon, it is preferable to have high rigidity. It is especially preferable to have a high Young's coefficient of 65 GPa or higher.

[0040] <Multilayer Reflective Film 2> The multilayer reflective film 2 is composed of a plurality of layers periodically laminated with elements of different refractive indices as the main components. Generally, the multilayer reflective film 2 comprises a multilayer film in which thin films of light elements or their compounds of high refractive index materials (high refractive index layers) and thin films of heavy elements or their compounds of low refractive index materials (low refractive index layers) are alternately laminated.

[0041] In order to form the multilayer reflective film 2, a plurality of high-refractive-index layers and low-refractive-index layers can be sequentially deposited from the substrate 1 side. In this case, one (high-refractive-index layer / low-refractive-index layer) stacked structure becomes one cycle.

[0042] The multilayer reflective film 2 of this embodiment comprises a multilayer film in which a low refractive index layer containing at least one of ruthenium (Ru) and rhodium (Rh) is alternately laminated with a high refractive index layer containing silicon (Si).

[0043] In this embodiment, the high refractive index layer is a silicon (Si) layer. The high refractive index layer may contain Si monomers or Si compounds. 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 Si-containing layer as the high refractive index layer, a multilayer reflective film 2 with excellent EUV light reflectivity can be obtained. To obtain higher reflectivity, the high refractive index layer is preferably composed of silicon (Si). Furthermore, "the high refractive index layer is composed of silicon (Si)" means that it does not prevent the presence of impurities other than Si that are unavoidably mixed in the high refractive index layer. The same applies to other thin films and other elements.

[0044] In this embodiment, the low refractive index layer contains at least one element selected from ruthenium (Ru) and rhodium (Rh). By containing ruthenium (Ru) and / or rhodium (Rh) in the low refractive index layer, a shallow effective reflective surface can be obtained compared to conventional Mo / Si multilayer reflective films.

[0045] As the node (minimum linewidth) of the transfer substrate becomes narrower, the impact of the 3D effect on the transfer characteristics increases. The 3D effect refers to the influence of the three-dimensional structure of the reflective mask 200, including the height direction, on the fidelity of the transfer pattern relative to the mask pattern. In EUV lithography, to suppress the 3D effect, the reflective surface of the reflective mask 200 must be controlled. Specifically, as a control of the reflective surface, the effective reflective surface of the multilayer reflective film 2 must be as close to the surface as possible. By having a shallow effective reflective surface, the EUV light reflected from the multilayer reflective film 2 can be controlled to not diffuse, thus suppressing the 3D effect. By comprising a multilayer film having alternating layers of a low-refractive-index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high-refractive-index layer containing silicon (Si), the effective reflective surface of the multilayer reflective film 2 can be made shallower compared to the conventional Mo / Si multilayer reflective film.

[0046] On the other hand, when Ru and / or Rh are used as the material of the low refractive index layer, there is a problem that the reflectivity of the multilayer reflective film 2 decreases relative to EUV light due to Si diffusion from the high refractive index layer. In this embodiment, this problem can be suppressed by making the low refractive index layer contain specific additive elements other than Ru and / or Rh.

[0047] The low-refractive-index layer of the substrate 90 with the multilayer reflective film in this embodiment further contains an additive element with a work function greater than 3.7 eV but less than 4.7 eV as a specific additive element. Furthermore, since the work function of Ru is 4.71 eV and that of Rh is 4.98 eV, the work function of the additive element is lower than that of Ru. Therefore, by adding the additive element to the low-refractive-index layer, the diffusion of material (Si) from the high-refractive-index layer to the low-refractive-index layer can be suppressed. On the other hand, when the high-refractive-index layer contains an element with a work function equal to or greater than that of Ru, the problem of Si from the high-refractive-index layer diffusing to the low-refractive-index layer occurs. Also, since the work function of Mg is 3.66 eV, the work function of the additive element is higher than that of Mg. Adding an element with a work function equal to or lower than that of Mg to the low-refractive-index layer makes it difficult to manufacture a pure metal target for film deposition by sputtering. Therefore, the work function of the added element must be within the above range. The work function of the added element refers to the work function of a metal composed of only one added element, not an alloy.

[0048] Furthermore, the work function is considered to be the difference between the vacuum energy level and the Fermi level. Therefore, the added elements can also be selected based on the magnitude of the Fermi level of the metal. That is, the added elements contained in the low refractive index layer are metallic elements with a Fermi level higher than that of Ru and lower than that of magnesium (Mg).

[0049] Silicon (Si) materials, which are known to be high-refractive-index layers, have the property of easily diffusing into metals. The ease of Si diffusion into a metal depends on the work function of the metal. That is, if the work function of the metal in the low-refractive-index layer increases, Si will diffuse more easily into the metal (low-refractive-index layer). As a result, the reflectivity of EUV light caused by the multilayer reflective film 2 will decrease. This decrease in reflectivity occurs particularly significantly after the annealing of the multilayer reflective film 2. Conversely, if the work function of the metal decreases, Si will not diffuse as easily into the metal (low-refractive-index layer). Therefore, the additive element in the low-refractive-index layer used to form the multilayer reflective film 2 in combination with a high-refractive-index layer containing Si is preferably a metal with a small work function.

[0050] Similarly, when the Si thin film and the metal thin film are in contact, if the work function of the metal increases, the adhesion between the Si thin film and the metal thin film will decrease. Conversely, if the work function of the metal decreases, the adhesion between the Si thin film and the metal thin film will increase. Therefore, the additive element contained in the low refractive index layer of the multilayer reflective film 2, which is combined with a high refractive index layer containing Si, is preferably a metal with a small work function.

[0051] As can be understood from the above, compared to low-refractive-index layers composed solely of Ru, low-refractive-index layers composed solely of Rh, and low-refractive-index layers composed solely of Ru and Rh, the diffusion of Si into the low-refractive-index layer can be reduced when an additive element with a work function smaller than that of Ru (4.71 eV) is included. Furthermore, it can be understood that the adhesion between the low-refractive-index layer and the high-refractive-index layer can be improved.

[0052] Furthermore, in the case of pure semiconductor Si without impurities, the work function of Si is 4.61 eV (the difference between the vacuum level and the exact midpoint of the band gap (Fermi level)). By using a metal with a lower work function than that of Si as an additive element, the diffusion of Si into the low refractive index layer can be suppressed more reliably.

[0053] As described above, by using a low-refractive-index layer of a material containing specific additive elements in Ru and / or Rh, a shallow effective reflective surface is achieved, which can suppress the diffusion of Si atoms from the high-refractive-index layer containing Si to the low-refractive-index layer. As a result, the decrease in reflectivity of the multilayer reflective film 2 of the substrate 90 with the multilayer reflective film to EUV light can be suppressed. Furthermore, the adhesion between the low-refractive-index layer and the high-refractive-index layer of the multilayer reflective film 2 can be improved.

[0054] Figure 7 shows the relationship between the atomic number of a metallic element and its work function. The elements inside the quadrilateral shown by the dashed lines in Figure 7 are metallic elements with a work function greater than 3.7 eV but less than 4.7 eV. By including these metallic elements in the low-refractive-index layer as additives, the diffusion of Si atoms from the high-refractive-index layer containing Si to the low-refractive-index layer can be suppressed, thereby improving the adhesion between the low-refractive-index layer and the high-refractive-index layer.

[0055] Table 2 is a list of additive elements contained in the low-refractive-index layer of the multilayer reflective film 2 of the substrate 90 with the multilayer reflective film of this embodiment. Table 2 shows the work function, refractive index (n), and extinction coefficient (k) of each additive element. In addition, there are cases in this specification where additive elements are represented as "X". For example, when the low-refractive-index layer is made of Ru and the additive element, the material of the low-refractive-index layer may be recorded as RuX.

[0056] In this embodiment, the low-refractive-index layer contains at least one additive element selected from thallium (Tl), hafnium (Hf), titanium (Ti), zirconium (Zr), manganese (Mn), indium (In), gallium (Ga), cadmium (Cd), bismuth (Bi), tantalum (Ta), lead (Pb), silver (Ag), aluminum (Al), vanadium (V), niobium (Nb), tin (Sn), zinc (Zn), mercury (Hg), chromium (Cr), iron (Fe), antimony (Sb), tungsten (W), molybdenum (Mo), and copper (Cu). The work function of these additive elements is in the range of greater than 3.7 eV but less than 4.7 eV. Therefore, the diffusion of Si atoms from the high-refractive-index layer containing Si to the low-refractive-index layer can be suppressed, thereby improving the adhesion between the low-refractive-index layer and the high-refractive-index layer.

[0057] Additives with low work functions reduce Si diffusion towards the low-refractive-index layer. Therefore, additives can be divided into three diffusion prevention groups based on their work functions. Diffusion prevention group A contains additives with work functions higher than 3.7 eV but lower than 4.3 eV. Diffusion prevention group B contains additives with work functions higher than 4.3 eV but lower than 4.5 eV. Diffusion prevention group C contains additives with work functions higher than 4.5 eV but lower than 4.7 eV. The diffusion prevention groups for each additive are shown in the "Diffusion Prevention Groups" column of Table 2.

[0058] In addition, the additive elements belonging to diffusion prevention group A are Tl, Hf, Ti, Zr, Mn, In, Ga, Cd, Bi, Ta, Pb, Ag, Al, V, Nb, and Sn. The additive elements belonging to diffusion prevention group B are Zn, Hg, Cr, and Fe. The additive elements belonging to diffusion prevention group C are Sb, W, Mo, and Cu.

[0059] Since Si diffusion towards the low-refractive-index layer is more likely to occur when the amount of the added element is relatively small compared to the low-refractive-index layer, the reflectivity of the multilayer reflective film 2 may decrease. In order to suppress the diffusion of Si towards the low-refractive-index layer, the added elements belonging to diffusion prevention groups A, B, and C may have a lower limit for the amount added to the low-refractive-index layer. The amount of added element in diffusion prevention group A is preferably 1 atomic% or more, more preferably 3 atomic% or more. The amount of added element in diffusion prevention group B is preferably 4 atomic% or more, more preferably 7 atomic% or more. The amount of added element in diffusion prevention group C is preferably 8 atomic% or more, more preferably 12 atomic% or more. The diffusion prevention group of each added element is shown in the "Lower Limit (atomic %)" column of Table 2.

[0060] Furthermore, the ratio (content of additive element / content of main material) of diffusion prevention group A to the content of the main material (Ru content, Rh content, or RuRh content) of the low refractive index layer is preferably 0.01 or more, and more preferably 0.03 or more. The ratio of the content of additive element of diffusion prevention group B to the content of the main material of the low refractive index layer is preferably 0.04 or more, and more preferably 0.08 or more. The ratio of the content of additive element of diffusion prevention group C to the content of the main material of the low refractive index layer is preferably 0.09 or more, and more preferably 0.13 or more.

[0061] In order to suppress the diffusion of Si into the low refractive index layer, the added element is preferably an added element belonging to diffusion prevention group A and B, and more preferably an added element belonging to diffusion prevention group A. Furthermore, the added element may also be selected from multiple groups of diffusion prevention group A, B, and / or C.

[0062] Figure 8 shows the relationship between the refractive index (n) and extinction coefficient (k) of the added element. In Figure 8, the curve shown by the solid line is the curve representing the relationship between the refractive index (n) and the extinction coefficient (k) according to the following equation (1). Equation (1): k=(1.735 / n-1.716) 2 When the material of the low refractive index layer is the case of the refractive index (n) and extinction coefficient (k) on the solid line of equation (1), when forming a multilayer reflective film 2 with the stacked structure of the low refractive index layer and the high refractive index layer of Si, the reflectivity of the multilayer reflective film 2 relative to EUV light with a wavelength of 13.5nm can be predicted by simulation. Furthermore, the simulation model uses a multilayer film consisting of two layers sequentially stacked, one high-refractive-index layer (Si) and one low-refractive-index layer with a refractive index (n) of 0.88 to 0.96 and an extinction coefficient (k) of 0 to 0.08, as one period, and stacking these layers for 40 periods. Also, "reflectivity relative to EUV light at a wavelength of 13.5 nm" refers to the maximum reflectivity calculated in the above simulation using the reflectivity described below, where the thickness of the high-refractive-index layer can vary within the range of 0 nm to 6 nm, and the thickness of the low-refractive-index layer can vary within the range of 0 nm to 6 nm.

[0063] Furthermore, in Figure 8, the curve shown by the dashed line is the curve representing the relationship between the refractive index (n) and the extinction coefficient (k) according to the following equation (2). Equation (2): k = 0.0021n -51.65 When the material of the low refractive index layer is the same as the refractive index (n) and extinction coefficient (k) on the dashed line of equation (2), when forming a multilayer reflective film 2 with the stacked structure of the low refractive index layer and the high refractive index layer of Si, the reflectivity of the multilayer reflective film 2 relative to EUV light with a wavelength of 13.5 nm can be predicted to be 35% by simulation. In addition, in the simulation, a multilayer film with 40 cycles of stacked layers is used as the model, consisting of 1 high refractive index layer (Si) and 1 low refractive index layer with a refractive index (n) of 0.88 to 0.96 and an extinction coefficient (k) of 0 to 0.08. Furthermore, "reflectivity relative to EUV light with a wavelength of 13.5 nm" refers to the maximum reflectivity calculated in the above simulation using the reflectivity described below, where the thickness of the high refractive index layer can be varied within the range of 0 nm to 6 nm and the thickness of the low refractive index layer can be varied within the range of 0 nm to 6 nm.

[0064] Figure 8 shows the relationship between the refractive index (n) and extinction coefficient (k) of each added element. The reflectivity relative to EUV light with a wavelength of 13.5 nm can be predicted using the values ​​of the refractive index (n) and extinction coefficient (k) of the added elements. For example, in the case of a multilayer reflective film 2 having a low refractive index layer of Mo and a high refractive index layer of Si, the reflectivity of the multilayer reflective film 2 relative to EUV light can be predicted using the values ​​of the refractive index (n) and extinction coefficient (k) of Mo shown in Figure 8. Furthermore, the model used to predict this reflectivity is a multilayer film with two layers sequentially stacked, one high refractive index layer (Si) and one low refractive index layer, as one period, and stacked for 40 periods. The reflectivity is the maximum reflectivity predicted by varying the film thickness of the high refractive index layer within the range of 0 nm to 6 nm and the film thickness of the low refractive index layer within the range of 0 nm to 6 nm. Furthermore, although Figure 8 shows a prediction when the number of layers of the multilayer reflective film 2 is 40 cycles, the same trend can be said to apply when the number of layers is less than 40 cycles, such as around 35 cycles.

[0065] Based on the relationship shown in Figure 8, the added elements can be divided into three optical characteristic groups according to their influence on the reflectance of the added elements. The added elements contained in optical characteristic group a (represented as "Group a" in Figure 8) are those with reflectance higher than the solid line (50% reflectance) of Equation (1). The added elements contained in optical characteristic group b (represented as "Group b" in Figure 8) are those with reflectance lower than the solid line (50% reflectance) of Equation (1) but higher than the dashed line (35% reflectance) of Equation (2). The added elements contained in optical characteristic group c (represented as "Group c" in Figure 8) are those with reflectance lower than the dashed line (35% reflectance) of Equation (2). The optical characteristic groups of each added element are displayed in the "Optical Characteristic Group" column of Table 2.

[0066] In order to improve and maintain the reflectivity of the multilayer reflective film 2 relative to EUV light, the amount of elements added to the low-refractive-index layer can be capped. This is because if the amount of added elements relative to the low-refractive-index layer is too large, the reflectivity of the multilayer reflective film 2 will decrease. The amount of added elements in optical property group a is preferably 50 atomic percent or less, more preferably 40 atomic percent or less. The amount of added elements in optical property group b is preferably 30 atomic percent or less, more preferably 20 atomic percent or less. The amount of added elements in optical property group c is preferably 15 atomic percent or less, more preferably 10 atomic percent or less. The optical property groups of each added element are shown in the "Upper Limit (atomic %)" column of Table 2.

[0067] Furthermore, the ratio (content of added element / content of main material) of optical property group a to the content of the main material (Ru content, Rh content, or RuRh content) of the low refractive index layer is preferably 0.56 or less, more preferably 0.44 or less. The ratio of the content of added element of optical property group b to the content of the main material of the low refractive index layer is preferably 0.33 or less, more preferably 0.22 or less. The ratio of the content of added element of optical property group c to the content of the main material of the low refractive index layer is preferably 0.17 or less, more preferably 0.11 or less.

[0068] In addition, the additive elements belonging to optical property group a are zirconium (Zr), niobium (Nb), and molybdenum (Mo). The additive elements belonging to optical property group b are thallium (Tl), titanium (Ti), manganese (Mn), indium (In), cadmium (Cd), tantalum (Ta), lead (Pb), silver (Ag), vanadium (V), mercury (Hg), chromium (Cr), and tungsten (W). The additive elements belonging to optical property group c are hafnium (Hf), gallium (Ga), bismuth (Bi), aluminum (Al), tin (Sn), zinc (Zn), iron (Fe), antimony (Sb), and copper (Cu).

[0069] In order to obtain good optical properties, the added element is preferably an added element belonging to optical property groups a and b, and more preferably an added element belonging to optical property group a. Alternatively, a plurality of added elements may be selected from optical property groups a, b and / or c.

[0070] As described above, the preferred content range of the added elements in the low refractive index layer is shown in Table 2. Furthermore, when Tl is the added element, the content of the main material (Ru content, Rh content, or RuRh content) in the low refractive index layer is preferably greater than 70 atomic% but less than 99 atomic%. When Hf is the added element, the content of the main material is preferably greater than 85 atomic% but less than 99 atomic%. When Ti is the added element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Zr is the added element, the content of the main material is preferably greater than 50 atomic% but less than 99 atomic%. When Mn is the added element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When In is the added element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Ga is the added element, the content of the main material is preferably greater than 85 atomic% but less than 99 atomic. When Cd is an additive element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Bi is an additive element, the content of the main material is preferably greater than 85 atomic% but less than 99 atomic%. When Ta is an additive element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Pb is an additive element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Ag is an additive element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Al is an additive element, the content of the main material is preferably greater than 85 atomic% but less than 99 atomic%. When V is an additive element, the content of the main material is preferably greater than 70 atomic% but less than 99 atomic%. When Nb is an additive element, the content of the main material is preferably greater than 50 atomic% but less than 99 atomic%. When Sn is an additive element, the content of the main material is preferably greater than 85 atomic% but less than 99 atomic%. When Zn is an additive element, the content of the main material is preferably greater than 85 atomic% but less than 96 atomic%. When Hg is an additive element, the preferred content of the main material is greater than 70 atomic% but less than 96 atomic%. When Cr is an additive element, the preferred content of the main material is greater than 70 atomic% but less than 96 atomic%. When Fe is an additive element, the preferred content of the main material is greater than 85 atomic% but less than 96 atomic%. When Sb is an additive element, the preferred content of the main material is greater than 85 atomic% but less than 92 atomic%. When W is an additive element, the preferred content of the main material is greater than 70 atomic% but less than 92 atomic%. When Mo is an additive element, the preferred content of the main material is greater than 50 atomic% but less than 92 atomic%. When Cu is an additive element, the preferred content of the main material is greater than 85 atomic% but less than 92 atomic%.

[0071] When the alloy contains multiple additive elements, the appropriate mixing amount of the alloy additive elements in the low-refractive-index layer can be estimated based on the appropriate content of each additive element and the mixing amount of each element in the alloy. Furthermore, the low-refractive-index layer preferably does not contain Ru and Rh, the main materials, or elements other than those listed in Table 2. This is because if elements other than the main materials and additive elements are present, the possibility of Si from the high-refractive-index layer diffusing into the low-refractive-index layer increases. Therefore, the low-refractive-index layer is preferably composed only of Ru and / or Rh, and specific additive elements.

[0072] In this embodiment, when the substrate 90 with the multilayer reflective film has a stacked structure of low-refractive-index layers and high-refractive-index layers as one cycle, the stacked structure preferably has fewer than 40 cycles. The stacked structure of the multilayer reflective film 2 preferably has 35 cycles or less, and more preferably 30 cycles or less. Since the effective reflective surface of the multilayer reflective film 2 in this embodiment is very shallow, it can obtain appropriate reflectivity with fewer cycles compared to conventional multilayer reflective films 2. Therefore, the 3D effect can be suppressed by using the substrate 90 with the multilayer reflective film in this embodiment. Furthermore, in order to make the multilayer reflective film 2 have appropriate reflectivity, the stacked structure preferably has 20 cycles or more, and more preferably 25 cycles or more.

[0073] When forming the multilayer reflective film 2, a high refractive index layer can be formed first on the surface of the substrate 1, followed by a low refractive index layer. In this case, the multilayer reflective film 2 is a stacked structure on the substrate 1 with a specific number of cycles, where the high refractive index layer and the low refractive index layer are each one cycle. The uppermost layer of the multilayer reflective film 2 is a low refractive index layer. In this case of the multilayer reflective film 2 structure, if the outermost surface of the multilayer reflective film 2 is composed of a low refractive index layer, it will be easily oxidized depending on the material constituting the low refractive index layer, resulting in a reduction in the reflectivity of the reflective shield 200. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 2. Alternatively, a Si layer made of Si can be formed on the uppermost low refractive index layer instead of the high refractive index layer.

[0074] When forming the multilayer reflective film 2, a low-refractive-index layer can be formed first on the surface of the substrate 1, followed by high- and low-refractive-index layers. In this case, the multilayer reflective film 2 is a stacked structure on the substrate 1 with a specific number of cycles, where the low-refractive-index layer and the high-refractive-index layer are one cycle. In this case, since the topmost layer is a high-refractive-index layer, it can remain as is.

[0075] Furthermore, as described above, when the uppermost layer of the multilayer reflective film 2 is a high refractive index layer, it is preferable to form the protective film 3 (described later) on the multilayer reflective film 2.

[0076] On the other hand, when the low-refractive-index layer of the multilayer reflective film 2 in this embodiment contains ruthenium (Ru), the uppermost layer of the multilayer reflective film 2 can be a low-refractive-index layer. This is because Ru has the function of protecting the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective shield 200 described later. In this case, the uppermost low-refractive-index layer can also function as a protective film 3.

[0077] As described above, the structure of the multilayer reflective film 2 is preferably as follows: the low-refractive-index layer preferably contains Ru, and a high-refractive-index layer and a low-refractive-index layer containing Ru are sequentially deposited from the substrate 1 side, with the uppermost layer being a low-refractive-index layer. Furthermore, the thickness and composition of the uppermost low-refractive-index layer can be appropriately adjusted from the perspective of dry etching tolerance and cleaning tolerance. In addition, to obtain a high-reflectivity multilayer reflective film 2, the thickness and composition of the uppermost low-refractive-index layer are preferably the same as the thickness and composition of the other low-refractive-index layers.

[0078] The reflectivity of the multilayer reflective film 2 used in this embodiment is, for example, 65% or more. The upper limit of the reflectivity of the multilayer reflective film 2 is, for example, 73%. Furthermore, the thickness and period of the layers contained in the multilayer reflective film 2 can be selected to satisfy Bragg's law. In the case of the multilayer reflective film 2 used to reflect EUV light with a wavelength of 13.5 nm, the film thickness of one period (one pair of high refractive index layers and low refractive index layers) is preferably about 7 nm.

[0079] The multilayer reflective film 2 can be formed by known methods. The multilayer reflective film 2 can be formed by, for example, ion beam sputtering, magnetron sputtering and reactive sputtering.

[0080] For example, when the multilayer reflective film 2 is a RuNb / Si multilayer film with Nb as the additive element of the low refractive index layer, a RuNb film with a thickness of about 3 nm is formed on the substrate 1 by ion beam sputtering using a RuNb target. Next, a Si film with a thickness of about 4 nm is formed using a Si target. By repeating the above operations, a multilayer reflective film 2 with 20 to 39 RuNb / Si films can be formed. At this time, the surface layer on the opposite side of the substrate 1 of the multilayer reflective film 2 is a layer containing Si (Si film). The thickness of one RuNb / Si film is preferably 7 nm.

[0081] <Protective film 3> As shown in FIG2, the substrate 90 with multilayer reflective film in this embodiment preferably has a protective film 3 disposed on the multilayer reflective film 2.

[0082] In order to protect the multilayer reflective film 2 from the dry etching and cleaning processes in the manufacturing process of the reflective mask 200 described later, a protective film 3 may be formed on or adjacent to the surface of the multilayer reflective film 2. Furthermore, the protective film 3 also has the function of protecting the multilayer reflective film 2 when using electron beams (EB) to correct black defects in the transfer pattern (absorber pattern 4a). Because a protective film 3 is formed on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 during the manufacturing of the reflective mask 200 can be suppressed. As a result, the reflectivity characteristics of the multilayer reflective film 2 relative to EUV light become better.

[0083] Figure 2 shows the case where the protective film 3 is a single layer. Alternatively, the protective film 3 can be a two-layer laminated structure. Furthermore, the protective film 3 can be a three-layer or more laminated structure, with the bottom and top layers being layers composed of a substance containing, for example, Ru, and a metal or alloy other than Ru being interposed between the bottom and top layers. The protective film 3 is formed from a material containing, for example, ruthenium as a main component. Examples of materials containing ruthenium as a main component include Ru metal monomers, Rh metal monomers, Ru alloys containing 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 containing nitrogen.

[0084] The Ru content of the Ru alloy used in the protective film 3 is 50 atomic% or more but less than 100 atomic%, preferably 80 atomic% or more but less than 100 atomic%, and more preferably 95 atomic% or more but less than 100 atomic%. Under these conditions, the protective film 3 can sufficiently ensure the reflectivity of EUV light, while also having the functions of mask cleaning resistance, etching stop function during etching of the absorber film 4, and preventing the multilayer reflective film 2 from changing over time.

[0085] In this embodiment, the substrate 90 with the multilayer reflective film preferably contains the same material as the low refractive index layer in the protective film 3. Furthermore, in this embodiment, the substrate 90 with the multilayer reflective film preferably contains at least one additive element (X) selected from ruthenium (Ru) and rhodium (Rh), which is the same as that in the low refractive index layer.

[0086] As described above, the low-refractive-index layer contains at least one of ruthenium (Ru) and rhodium (Rh) as well as the aforementioned specific additive element X. Therefore, the protective film 3 preferably contains the same material as the low-refractive-index layer (RuX, RhX, or RuRhX). By making the protective film 3 contain the same material as the low-refractive-index layer, the substrate 90 with the multilayer reflective film of this embodiment can be expected to achieve the function of being part of the multilayer reflective film 2. Therefore, the reflectivity of the multilayer reflective film 2 can be improved. Furthermore, by using the same material as the low-refractive-index layer, the protective film 3 can be formed more easily. In addition, the protective film 3 is preferably composed of a material with the same elements and the same composition ratio as the low-refractive-index layer.

[0087] The thickness of the protective film 3 is not particularly limited as long as it can achieve the function of the protective film 3. From the viewpoint of EUV light reflectivity, 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.

[0088] When the protective film 3 is made of the same material as the low-refractive-index layer, the thickness of the protective film 3 is preferably the same as the thickness of the low-refractive-index layer of the multilayer reflective film 2. In this case, the protective film 3 is preferably formed in contact with the surface of the high-refractive-index layer of the multilayer reflective film 2. As a result, the protective film 3 can function as part of the multilayer reflective film 2.

[0089] When the uppermost layer of the multilayer reflective film 2 is a low-refractive-index layer, this uppermost low-refractive-index layer can also serve as a protective film 3. Since the low-refractive-index layer in this embodiment is a thin film made of ruthenium (Ru) and / or rhodium (Rh) and specific additive elements, it can function as a protective film 3. Therefore, when using the reflective mask substrate 100 described later to manufacture the reflective mask 200 (EUV mask), damage to the surface of the multilayer reflective film 2 can be suppressed, and the reflectivity characteristics relative to EUV light become better.

[0090] There are no particular limitations on the method of forming the protective film 3, and known film forming methods can be used. Specific examples include ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum evaporation as methods for forming the protective film 3.

[0091] <Absorber film 4> The reflective shielding substrate 100 of this embodiment has an absorber film 4 on the multilayer reflective film 2 of the substrate 90 with the multilayer reflective film or on the protective film 3 formed on the multilayer reflective film 2.

[0092] FIG3 is a cross-sectional schematic diagram showing an example of a reflective shielding substrate 100 of this embodiment. The reflective shielding substrate 100 shown in FIG3 has an absorber film 4 for absorbing EUV light on the multilayer reflective film 2 of the substrate 90 with multilayer reflective film shown in FIG1. ​​In addition, the reflective shielding substrate 100 may have other thin films such as a resistive film 11 on the absorber film 4. In the configuration shown in FIG3, the uppermost layer of the multilayer reflective film 2 is preferably a low refractive index layer containing RuX or RuRhX.

[0093] FIG4 is a cross-sectional schematic diagram showing an example of a reflective shielding substrate 100 of this embodiment. The reflective shielding substrate 100 shown in FIG4 has an absorber film 4 for absorbing EUV light on the protective film 3 of the substrate 90 with multilayer reflective films shown in FIG2. In addition, the reflective shielding substrate 100 may have other thin films such as a blocking film 11 on the absorber film 4.

[0094] FIG5 is a cross-sectional schematic diagram showing another example of the reflective mask substrate 100 of this embodiment. As shown in FIG5, the reflective mask substrate 100 may have an etched mask film 6 on the absorber film 4. In addition, the reflective mask substrate 100 may have other thin films such as a resist film 11 on the etched mask film 6.

[0095] Since the absorber film 4 of the reflective shield substrate 100 of this embodiment can absorb EUV light, the reflective shield 200 (EUV shield) of the present invention can be manufactured by patterning the absorber film 4 of the reflective shield substrate 100. By using the reflective shield substrate 100 of this embodiment, a reflective shield substrate 100 having a multilayer reflective film 2 can be obtained. The multilayer reflective film 2 has a shallow effective reflective surface, which can suppress the diffusion of atoms as materials between the low refractive index layer and the high refractive index layer.

[0096] The basic function of the absorber film 4 is to absorb EUV light. The absorber film 4 can be an absorber film 4 intended for absorbing EUV light, or it can be an absorber film 4 with a phase-shifting function that also takes into account the phase difference of EUV light. The absorber film 4 with a phase-shifting function refers to a film that absorbs EUV light and reflects a portion of the EUV light to shift the phase. That is, in the reflective mask 200 after the absorber film 4 with a phase-shifting function is patterned, in the area where the absorber film 4 is formed, some light is reflected to a degree that absorbs EUV light to weaken it and does not adversely affect the pattern transfer. Furthermore, in the area where the absorber film 4 is not formed (field region), EUV light (in the case of a protective film 3, it is reflected through the protective film 3) will be reflected by the multilayer reflective film 2. Thus, the desired phase difference will be generated between the reflected light from the absorber film 4 with a phase-shifting function and the reflected light from the field region. The absorber film 4 with phase-shifting function is preferably configured such 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 phase-reversed light interferes with each other at the edges of the pattern, thereby improving the image contrast of the projected optical image. Resolution increases with this improved image contrast, thus enhancing various exposure-related margins such as exposure margin and focus margin.

[0097] The absorber film 4 can be a single-layer film or a multilayer film composed of multiple films (e.g., a lower absorber film and an upper absorber film). In the case of a single-layer film, the number of processes in the mask substrate manufacturing can be reduced to improve production efficiency. In the case of a multilayer film, its optical constants and film thickness can be appropriately set so that the upper absorber film becomes an anti-reflective film when using light to inspect mask pattern defects. In this way, the inspection sensitivity when using light to inspect mask pattern defects is improved. Furthermore, if films containing oxygen (O) and nitrogen (N) that can improve oxidation resistance are added to the upper absorber film, the stability over time will be improved. In this way, by making the absorber film 4 a multilayer film, various functions can be added to the absorber film 4. When the absorber film 4 has a phase-shifting function, by making it a multilayer film, the adjustment range on the optical surface can be increased, thus making it easier to obtain the desired reflectivity.

[0098] As for the material of the absorber film 4, as long as it has the function of absorbing EUV light, it can be processed by etching or the like (preferably by dry etching with chlorine (Cl) gas and / or fluorine (F) gas), and there are no particular restrictions on the material that has a higher etching selectivity than the protective film 3. Preferably, the metal possessing such functionality is an alloy containing two or more of the following metals: palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or a compound thereof. The compound may contain oxygen (O), nitrogen (N), carbon (C), and / or boron (B) in the aforementioned metals or alloys.

[0099] The absorber film 4 can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, the absorber film 4 of tantalum compounds can be formed by using a target containing tantalum and boron, and by using reactive sputtering with argon gas containing oxygen or nitrogen.

[0100] Furthermore, from the viewpoint of smoothness and flatness, the crystalline state of the absorber film 4 is preferably amorphous or microcrystalline. If the surface of the absorber film 4 is not smooth or flat, the edge roughness of the absorber pattern 4a will increase, leading to a deterioration in the dimensional accuracy of the pattern. The surface roughness of the absorber film 4, in terms of root mean square roughness (RMS), is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less.

[0101] <Etching Mask Film 6> As shown in FIG5, the reflective mask substrate 100 of this embodiment may have an etching mask film 6 on the absorber film 4. As the material for the etching mask film 6, it is preferable to use a material with a high etch selectivity ratio (etching rate of absorber film 4 / etching rate of etching mask film 6) relative to the etch mask film 4. The etch selectivity ratio of absorber film 4 to the etch mask film 6 is preferably 1.5 or higher, and more preferably 3 or higher.

[0102] In this embodiment, the reflective masking substrate 100 preferably has an etched masking film 6 on the absorber film 4.

[0103] 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 is more preferably composed of CrN, CrO, CrC, CrON, CrOC, CrCN or CrOCN, and more preferably a CrO-based film (CrO film, CrON film, CrOC film or CrOCN film) containing chromium and oxygen.

[0104] Tantalum or a tantalum compound is preferably used as the material for the etching mask film 6. Examples of tantalum compounds include materials containing Ta and at least one element selected from N, O, B and H. The etching mask film 6 is more preferably composed of TaN, TaO, TaON, TaBN, TaBO or TaBON.

[0105] Silicon or silicon compounds are preferably used as the material for etching the mask film 6. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as metallic silicon (metal silicates) and metallic silicon compounds (metal silicate compounds) containing a metal. Examples of metallic silicon compounds include materials containing a metal and Si and at least one element selected from N, O, C, and H.

[0106] In order to form a pattern on the absorber film 4 with good precision, the thickness of the etched mask film 6 is preferably 3 nm or more. Furthermore, in order to make the resist film 11 thinner, the thickness of the etched mask film 6 is preferably 15 nm or less.

[0107] <Inner Surface Conductive Film 5> An inner surface conductive film 5 for an electrostatic clamp can be formed on the inner surface of the substrate 10 (the side opposite to the side where the multilayer reflective film 2 is formed). For use as an electrostatic clamp, the sheet resistance of the inner surface conductive film 5 is generally required to be 100 Ω / □ (Ω / square) or less. The inner surface conductive film 5 can be formed by magnetron sputtering or ion beam sputtering using a target material of metals such as chromium or tantalum or alloys thereof. The material of the inner surface conductive film 5 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the inner surface conductive film 5 is preferably a Cr compound containing at least one of boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Furthermore, the material of the inner 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. 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.

[0108] The thickness of the inner conductive film 5 is not particularly limited as long as it functions as a film for use as an electrostatic clamp. The thickness of the inner conductive film 5 is, for example, 10 nm to 200 nm.

[0109] <Reflective Mask 200>

[0110] As shown in FIG6D, the reflective mask 200 of this embodiment has an absorber pattern 4a after the absorber film 4 of the reflective mask substrate 100 is patterned.

[0111] Figures 6A-6D are schematic diagrams showing an example of a manufacturing method for a reflective mask 200. Using the reflective mask substrate 100 of this embodiment described above, the reflective mask 200 of this embodiment can be manufactured. Hereinafter, an example of a manufacturing method for the reflective mask 200 will be described.

[0112] First, a reflective mask substrate 100 is prepared, comprising 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 1 is formed on the absorber film 4 to obtain a reflective mask substrate 100 with a resist film 11 attached (Fig. 6A). A pattern is drawn on the resist film 11 using an electronic line drawing apparatus, and a resist pattern 11a is further formed through a developing and washing process (Fig. 6B).

[0113] The absorber film 4 is dry etched using the resist pattern 11a as a mask. In this way, the portion of the absorber film 4 not covered by the resist pattern 11a is etched to form the absorber pattern 4a (Fig. 6C).

[0114] For example, fluorine-based gases and / or chlorine-based gases can be used as etching gases for the absorber membrane 4. Fluorine-based gases include CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2. Chlorine-based gases include Cl2, SiCl4, CHCl3, CCl4, and BCl3. Furthermore, a mixture of fluorine-based gases and / or chlorine-based gases with O2 in a specific ratio can be used. These etching gases may further contain inactive gases such as He and / or Ar as needed.

[0115] After the absorber pattern 4a is formed, the resist pattern 11a is removed by resist stripping solution. After removing the resist pattern 11a, the reflective mask 200 of this embodiment can be obtained by a wet cleaning process using an acidic or alkaline aqueous solution (Fig. 6D).

[0116] Furthermore, when a reflective mask substrate 100 is used to form an etch mask film 6 on the absorber film 4, after using the resist pattern 11a as a mask to form a pattern (etch mask pattern) on the etch mask film 6, an additional step is added to use the etch mask pattern as a mask to form a pattern on the absorber film 4.

[0117] The reflective mask 200 obtained in this way will have a structure in which multiple reflective films 2, protective films 3 and absorber patterns 4a are deposited on the substrate 1.

[0118] The area exposed by the multilayer reflective film 2 (including the protective film 3) has the function of reflecting EUV light. The area of ​​the multilayer reflective film 2 (including the protective film 3) covered by the absorber pattern 4a has the function of absorbing EUV light. The reflective mask 200 of this embodiment has a multilayer reflective film with a shallow effective reflective surface, which can suppress the diffusion of atoms as materials between the low refractive index layer and the high refractive index layer. Therefore, by using the reflective mask 200 of this embodiment, finer patterns can be transferred onto the substrate.

[0119] <Method for Manufacturing a Semiconductor Device> The method for manufacturing a semiconductor device according to this embodiment includes a process of using the above-mentioned reflective mask 200 to perform a photolithography process using an exposure device to form a transfer pattern on a transfer object.

[0120] By using the photolithography of the reflective mask 200 of this embodiment, a transfer pattern can be formed on a semiconductor substrate (the transfer object). The transfer pattern has the shape of the pattern on which the reflective mask 200 is transferred. By forming a transfer pattern on a semiconductor substrate using the reflective mask 200, a semiconductor device can be manufactured.

[0121] According to this embodiment, a semiconductor device can be manufactured using a reflective mask 200 having a multilayer reflective film 2. The multilayer reflective film 2 has a shallow effective reflective surface, which can suppress the diffusion of atoms as materials between low-refractive-index layers and high-refractive-index layers. Therefore, by using the reflective mask 200 of this embodiment, the semiconductor device can be made more dense and more precise.

[0122] Using FIG9, a method for transferring a pattern onto a resist-coated semiconductor substrate 60 by means of EUV light will be described.

[0123] Figure 9 shows a schematic configuration of an apparatus (i.e., EUV exposure apparatus 50) used to transfer a transfer pattern onto a resist film formed on a semiconductor substrate 60. The EUV exposure apparatus 50 is precisely configured with an EUV light generating unit 51, an irradiation optical system 56, a photomask stage 58, a projection optical system 57, and a wafer stage 59 along the light path axis of the EUV light. The container of the EUV exposure apparatus 50 is filled with hydrogen gas.

[0124] The EUV light generation unit 51 includes a laser light source 52, a tin droplet generation unit 53, a collection unit 54, and a light-collecting unit 55. When a high-power carbon dioxide gas laser from the laser light source 52 irradiates tin droplets ejected from the tin droplet generation unit 53, the tin droplets undergo plasmaization to generate EUV light. The generated EUV light is focused in the light-collecting unit 55 and then incident on a reflective mask 200 provided on a photomask stage 58 via an irradiation optical system 56. The EUV light generation unit 51 generates EUV light with a wavelength of, for example, 13.53 nm.

[0125] The EUV light reflected by the reflective mask 200 is reduced to a pattern image light, typically about 1 / 4 of its original size, by the projection optics system 57 and projected onto the semiconductor substrate 60 (the substrate to be transferred). This transfers the desired circuit pattern onto a resist film on the semiconductor substrate 60. By developing the exposed resist film, a resist pattern can be formed on the semiconductor substrate 60. Using the resist pattern as a mask, the semiconductor substrate 60 is etched, thereby forming an integrated circuit pattern on the semiconductor substrate. Through the above-described process and other necessary processes, a semiconductor device is manufactured.

[0126] [Example] Hereinafter, examples and comparative examples will be described with reference to drawings.

[0127] (Fabrication of substrate 90 with multilayer reflective film in Examples 1-10) First, a substrate 1 with dimensions of 6025 (approximately 152mm × 152mm × 6.35mm) is prepared after the first and second main surfaces have been ground. The substrate 1 is a substrate 1 made of low thermal expansion glass (SiO2-TiO2-based glass). The main surfaces of the substrate 1 are ground by a rough grinding process, a precision grinding process, a local processing process, and a contact grinding process.

[0128] Next, a multilayer reflective film 2 consisting of a high-refractive-index Si layer and a specific low-refractive-index layer is formed on the main surface (first main surface) of the substrate 1. Table 1 shows the material and composition of the low-refractive-index layer (RuX or RuRhX, where X is an additive element) in Examples 1 to 10. The material of the high-refractive-index layer in Examples 1 to 10 is Si. Table 1 shows the work function of the additive element (X) and the content (atomic %) of the additive element (X) in the low-refractive-index layer.

[0129] The multilayer reflective film 2 is formed by ion beam sputtering using a Si target and a RuX target or a RuRhX target (X being an additive element) and a Kr gas. First, a high-refractive-index Si layer with a thickness of 4.2 nm is formed using a Si target in contact with the main surface of the substrate 1. Then, a low-refractive-index RuX or RuRhX layer with a thickness of 2.8 nm is formed using a RuX target or a RuRhX target (X being an additive element). The multilayer reflective film 2 is formed by depositing 35 cycles (pairs) of one high-refractive-index layer and one low-refractive-index layer on the main surface of the substrate 1.

[0130] Next, a RuRhNb film was formed on the multilayer reflective film 2 of Examples 1-10 as a protective film 3. The protective film 3 was formed with a thickness of 3.5 nm using a RuRhNb target and by magnetron sputtering in an Ar gas atmosphere. The composition ratio (atomic %) of the protective film 3 was Ru:Rh:Nb = 64:16:20.

[0131] The substrate 90 with multilayer reflective film of Examples 1 to 10 was manufactured in accordance with the above method.

[0132] (Fabrication of substrate 90 with multilayer reflective film in Comparative Examples 1 and 2) The substrate 90 with multilayer reflective film was manufactured in the same manner as in Examples 1-10, except that the material of the low refractive index layer was Ru (Comparative Example 1) or RuRh (Comparative Example 2). Therefore, the low refractive index layers of Comparative Examples 1 and 2 do not contain additive element (X). Furthermore, a Ru target was used when forming the low refractive index layer of Comparative Example 1, while a RuRh target was used when forming the low refractive index layer of Comparative Example 2. Table 1 shows the composition ratio (atomic %) of the low refractive index layers of Comparative Examples 1 and 2.

[0133] (Evaluation of the reflectivity of the substrate 90 with multilayer reflective film) The reflectivity change of the substrate 90 with multilayer reflective film caused by heat treatment was measured using the substrate 90 with multilayer reflective film of the embodiment and comparative example made in accordance with the above method.

[0134] Specifically, firstly, the reflectance (R1, in %) of the substrate 90 with a multilayer reflective film of the embodiment and comparative example relative to EUV light (wavelength 13.5 nm) was measured. Next, the substrate 90 with a multilayer reflective film was heated at 200°C for 10 minutes in an atmospheric environment to perform heat treatment. After heat treatment, the reflectance (R2, in %) of the substrate 90 with a multilayer reflective film relative to EUV light was measured. The change in EUV reflectance of the substrate 90 with a multilayer reflective film due to heat treatment was obtained by subtracting the reflectance (R2) of the substrate 90 with a multilayer reflective film after heat treatment from the reflectance (R1) value of the substrate 90 with a multilayer reflective film before heat treatment. Table 1 shows the change in EUV reflectance caused by heat treatment.

[0135] As shown in Table 1, the reflectivity of the substrate 90 with multilayer reflective film in Examples 1-10 before and after heat treatment at 200°C for 10 minutes changed by less than 9.4% (Example 7). Since the material of the low-refractive-index layer of the multilayer reflective film 2 in Examples 1-10 is RuX or RuRhX containing a specific additive element (X), the diffusion of Si from the high-refractive-index layer to the low-refractive-index layer is suppressed. Therefore, it is speculated that the change in reflectivity before and after heat treatment will be small. In particular, the change in reflectivity in Example 1, where the material of the low-refractive-index layer is RuNb, is the smallest (6.9%).

[0136] On the other hand, before and after the heat treatment at 200°C for 10 minutes, the reflectivity of the substrate 90 with the multilayer reflective film in Comparative Examples 1 and 2 changed significantly relative to EUV light. It is speculated that in Comparative Examples 1 and 2, Si diffuses from the high-refractive-index layer to the low-refractive-index layer to form metal silicides (RuSi or RuRhSi) in the high-refractive-index layer, thus causing a significant change in reflectivity.

[0137] (Reflective mask substrate 100) Next, the reflective mask substrate 100 of Examples 1 to 10 will be described.

[0138] An inner conductive film 5 is formed on the inner surface of the substrate 1 of the substrate 90 with a multilayer reflective film manufactured in the manner described above, and an absorber film 4 is formed on the protective film 3 to manufacture the reflective shielding substrate 100 of Examples 1 to 10.

[0139] First, an inner conductive film 5, consisting of a CrN film, is formed on the second main surface (inner surface) of the substrate 1 of the substrate 90 with a multilayer reflective film by magnetron sputtering (reactive sputtering) under the following conditions. The formation conditions of the inner conductive film 5 are: Cr target material, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), and film thickness of 20 nm.

[0140] Next, a TaBN film with a thickness of 55 nm is formed on the protective film 3 of the substrate 90 with the multilayer reflective film to serve as the absorber film 4. The absorber film 4 has a composition of Ta:B:N = 75:12:13 (atomic ratio) and a thickness of 55 nm.

[0141] The reflective mask substrate 100 of Examples 1 to 10 was manufactured in accordance with the above method.

[0142] (Reflective Mask 200) Next, a reflective mask 200 is manufactured using the reflective mask substrate 100 of Examples 1 to 10. The manufacture of the reflective mask 200 will be described with reference to Figures 6A to 6D.

[0143] First, as shown in FIG6A, a resist film 11 is formed on the absorber film 4 of the reflective mask substrate 100. Then, a desired pattern, such as a circuit pattern, is drawn (exposed) on the resist film 11, and further developed and washed to form a specific resist pattern 11a (FIG. 6B). Next, using the resist pattern 11a as a mask, the absorber film 4 (TaBN film) is dry etched using Cl2 gas to form the absorber pattern 4a (FIG. 6C). Afterward, the resist pattern 11a is removed (FIG. 6D).

[0144] Finally, the reflective shields 200 of Examples 1 to 10 are manufactured by wet washing with pure water (DIW).

[0145] (Manufacturing of a semiconductor device) The reflective mask 200 of Examples 1 to 10 is mounted on an EUV scanner to perform EUV exposure on a wafer on a transfer substrate (semiconductor substrate 60) on which a processing film and a resist film are formed. Then, by developing the exposed resist film, a resist pattern is formed on the semiconductor substrate 56 on which the processing film is formed.

[0146] Since the reflective mask 200 of Examples 1 to 10 has a multilayer reflective film 2, which has a shallow effective reflective surface, it can suppress the phenomenon of the diffusion of atoms as materials between the low refractive index layer and the high refractive index layer. Therefore, fine and high-precision transfer patterns (resist patterns) can be formed on the semiconductor substrate 60 (the substrate to be transferred).

[0147] The resist pattern is transferred onto the processed film by etching, and through various processes such as the formation of insulating film and conductive film, introduction of dopants, or annealing, a semiconductor device with the desired characteristics can be manufactured with high yield.

[0148] [Table 1]

[0149] [Table 2] [Simplified Explanation of the Diagram]

[0030] Figure 1 is a cross-sectional schematic diagram showing an example of a substrate with a multilayer reflective film according to this embodiment. Figure 2 is a cross-sectional schematic diagram showing another example of a substrate with a multilayer reflective film according to this embodiment. Figure 3 is a cross-sectional schematic diagram showing an example of a reflective mask substrate according to this embodiment. Figure 4 is a cross-sectional schematic diagram showing another example of a reflective mask substrate according to this embodiment. Figure 5 is a cross-sectional schematic diagram showing yet another example of a reflective mask substrate according to this embodiment. Figures 6A-D are cross-sectional schematic diagrams showing an example of a manufacturing method of a reflective mask according to this embodiment. Figure 7 is a graph showing the relationship between the atomic number and work function of a metallic element. Figure 8 is a graph showing the relationship between the refractive index (n) and extinction coefficient (k) of an added element. Figure 9 is a schematic diagram showing an example of an EUV exposure apparatus.

Claims

1. A substrate with a multilayer reflective film, comprising a substrate and a multilayer reflective film disposed on the substrate; the multilayer reflective film comprising a multilayer film having an alternatingly deposited low refractive index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high refractive index layer containing silicon (Si); the low refractive index layer further comprising at least one additive element selected from thallium (Tl), hafnium (Hf), titanium (Ti), zirconium (Zr), manganese (Mn), indium (In), gallium (Ga), cadmium (Cd), bismuth (Bi), tantalum (Ta), lead (Pb), silver (Ag), aluminum (Al), vanadium (V), tin (Sn), zinc (Zn), mercury (Hg), chromium (Cr), iron (Fe), antimony (Sb), tungsten (W), and copper (Cu).

2. The substrate with a multilayer reflective film as described in claim 1 of the patent application satisfies the following conditions: When the added element contains zirconium (Zr), the amount of zirconium (Zr) added is more than 1 atomic% and less than 50 atomic%; When the added element contains thallium (Tl), titanium (Ti), manganese (Mn), indium (In), cadmium (Cd), tantalum (Ta), lead (Pb), silver (Ag) or vanadium (V), the amount of thallium (Tl), titanium (Ti), manganese (Mn), indium (In), cadmium (Cd), tantalum (Ta), lead (Pb), silver (Ag) or vanadium (V) added is more than 1 atomic% and less than 30 atomic%; When the added element contains hafnium (Hf), gallium (Ga), bismuth (Bi), aluminum (Al), or tin (Sn), the amount of hafnium (Hf), gallium (Ga), bismuth (Bi), aluminum (Al), or tin (Sn) added is 1 atomic% to 15 atomic%; when the added element contains mercury (Hg) or chromium (Cr), the amount of mercury (Hg) or chromium (Cr) added is 4 atomic% to 30 atomic%; when the added element contains zinc (Zn) or iron (Fe), the amount of zinc (Zn) or iron (Fe) added is 4 atomic% to 15 atomic%; when the added element contains tungsten (W), the amount of tungsten (W) added is 8 atomic% to 30 atomic%; When the added element contains antimony (Sb) or copper (Cu), the amount of antimony (Sb) or copper (Cu) added is more than 8 atomic% and less than 15 atomic%.

3. The substrate with a multilayer reflective film as claimed in claim 1 satisfies the following conditions: When the added element contains zirconium (Zr), the ratio of the zirconium (Zr) content to the content of the main material of the low refractive index layer is 0.01 to 0.56; When the added element contains thallium (Tl), titanium (Ti), manganese (Mn), indium (In), cadmium (Cd), tantalum (Ta), lead (Pb), silver (Ag), or vanadium (V), the ratio of the thallium (Tl), titanium (Ti), manganese (Mn), indium (In), cadmium (Cd), tantalum (Ta), lead (Pb), silver (Ag), or vanadium (V) content to the content of the main material of the low refractive index layer is 0.01 to 0.

33. When the added element contains hafnium (Hf), gallium (Ga), bismuth (Bi), aluminum (Al), or tin (Sn), the ratio of the content of hafnium (Hf), gallium (Ga), bismuth (Bi), aluminum (Al), or tin (Sn) to the content of the main material of the low refractive index layer is 0.01 to 0.17 or less; when the added element contains mercury (Hg) or chromium (Cr), the ratio of the content of mercury (Hg) or chromium (Cr) to the content of the main material of the low refractive index layer is 0.04 to 0.33 or less; when the added element contains zinc (Zn) or iron (Fe), the ratio of the content of zinc (Zn) or iron (Fe) to the content of the main material of the low refractive index layer is 0.04 to 0.17 or less; when the added element contains tungsten (W), the ratio of the content of tungsten (W) to the content of the main material of the low refractive index layer is 0.09 to 0.33 or less. When the added element contains antimony (Sb) or copper (Cu), the ratio of the content of antimony (Sb) or copper (Cu) to the content of the main material of the low refractive index layer is 0.09 to 0.

17.

4. A substrate with a multilayer reflective film, comprising a substrate and a multilayer reflective film disposed on the substrate; the multilayer reflective film comprising a multilayer film having an alternatingly deposited low-refractive-index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high-refractive-index layer containing silicon (Si); the low-refractive-index layer further comprising at least one additive element selected from niobium (Nb) and molybdenum (Mo); when the additive element contains niobium (Nb), the amount of niobium (Nb) added is 1 atomic% or more and 50 atomic% or less; when the additive element contains molybdenum (Mo), the amount of molybdenum (Mo) added is 8 atomic% or more and 50 atomic% or less.

5. A substrate with a multilayer reflective film, comprising a substrate and a multilayer reflective film disposed on the substrate; the multilayer reflective film comprising a multilayer film having an alternatingly deposited low-refractive-index layer containing at least one of ruthenium (Ru) and rhodium (Rh) and a high-refractive-index layer containing silicon (Si); the low-refractive-index layer further comprising at least one additive element selected from niobium (Nb) and molybdenum (Mo); when the additive element contains niobium (Nb), the ratio of the content of niobium (Nb) to the content of the main material of the low-refractive-index layer is 0.01 or more and 0.56 or less; when the additive element contains molybdenum (Mo), the ratio of the content of molybdenum (Mo) to the content of the main material of the low-refractive-index layer is 0.09 or more and 0.56 or less.

6. For a substrate with a multilayer reflective film as described in any of claims 1 to 5, wherein when the stacked structure of the low refractive index layer and the high refractive index layer is taken as 1 cycle, the stacked structure is less than 40 cycles.

7. The substrate with a multilayer reflective film as described in any of claims 1 to 5 of the patent application has a protective film on the multilayer reflective film.

8. The substrate with a multilayer reflective film as described in claim 7, wherein the protective film contains the same material as the low refractive index layer.

9. The substrate with a multilayer reflective film as claimed in claim 7, wherein the protective film contains at least one additive element selected from ruthenium (Ru) and rhodium (Rh) that is the same as that of the low refractive index layer.

10. A reflective shielding substrate having an absorber film on the protective film of a substrate with a multilayer reflective film as described in any of claims 7 to 9.

11. A reflective shield having an absorber pattern that patterns the absorber film of the reflective shield substrate as described in claim 10.

12. A method for manufacturing a semiconductor device, comprising a step of using a reflective mask as described in claim 11 of the claims to perform a photolithography process using an exposure device to form a transfer pattern on a transfer object.

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