Reflective mask blank, reflective mask, and method for manufacturing semiconductor device

Abstract

Provided is a reflective mask blank for manufacturing a reflective mask with which it is possible to reduce reflection of EUV light and out-of-band light in a light-blocking region of the reflective mask. This reflective mask blank has a substrate, a multilayer reflective film provided on the substrate, an absorber film provided on the multilayer reflective film, and a light-blocking film provided on the absorber film. The light-blocking film includes a plurality of layers. The absolute difference in refractive index with respect to the EUV light between layers in mutual contact among the plurality of layers is 0.06 or lower, and the absolute difference in extinction coefficient with respect to the EUV light between the layers in mutual contact is 0.03 or lower.

Description

Reflective mask blank, reflective mask, and method for manufacturing semiconductor device

[0001] The present disclosure relates to a reflective mask blank used in manufacturing a semiconductor device, a reflective mask, and a method for manufacturing a semiconductor device.

[0002] In general, in the manufacturing process of semiconductor devices, fine patterns are formed using photolithography. Furthermore, to form these fine patterns, a number of transfer masks, also known as photomasks, are typically used. These transfer masks are generally formed by providing a fine pattern made of a metal thin film or the like on a glass substrate. Photolithography is also used to manufacture these transfer masks.

[0003] In recent years, with the increasing integration density of semiconductor devices in the semiconductor industry, there has been a demand for finer patterns that exceed the transfer limit of conventional photolithography using ultraviolet light. One technique that enables the formation of such fine patterns is EUV lithography, an exposure technology using extreme ultraviolet (EUV) light. Here, EUV light refers to light in the wavelength range of the soft X-ray region or the vacuum ultraviolet region. Specifically, EUV light has a wavelength of around 13.5 nm, including 13.5 nm. In EUV lithography, a reflective mask is used as the transfer mask. Such a reflective mask includes a substrate, a multilayer reflective film formed on the substrate to reflect EUV light, which is the exposure light, and an absorber film formed in a pattern on the multilayer reflective film to absorb EUV light.

[0004] As described above, there is an increasing demand for finer patterns in lithography processes, but new problems have also arisen, as described below. Specifically, the shadowing effect is known as one of the problems with EUV lithography using a reflective mask. EUV light, which is the exposure light, is incident on the reflective mask at a certain angle (usually about 6 degrees) with respect to the perpendicular surface. This causes a shadow of the absorber film due to the film thickness of the absorber film. Since the exposure light is not reflected in this shadowed region, a dimensional difference occurs in the reflected image of the pattern, resulting in a distortion of the pattern image.

[0005] The shadowing effect can be reduced by reducing the thickness of the absorber film. However, thinning the absorber film creates a new problem: the light-shielding performance in the light-shielding region of the reflective mask deteriorates. The "light-shielding region" here refers to a region located on the periphery of the region containing the transfer pattern so that the transfer pattern of the reflective mask is exposed. This light-shielding region prevents exposure light from leaking into regions adjacent to the block on the semiconductor substrate to which the pattern is transferred during pattern transfer using a reflective mask. In actual exposure operations, multiple chips are mounted on a single semiconductor substrate. Therefore, if the reflected light from this light-shielding region is large, problems such as multiple exposures at the boundary regions between adjacent chips can occur, resulting in reduced yield. Therefore, the reflectance of the exposure light in this light-shielding region must be sufficiently small. However, as described above, thinning the absorber film to reduce the shadowing effect increases the amount of light emitted from the absorber film to the outside of the reflective mask. As a result, a new problem arises: the light-shielding performance in the light-shielding region cannot be sufficiently ensured.

[0006] Therefore, in one embodiment, Patent Document 1 proposes a method of forming a groove region dug from the surface of the light absorber layer to reach the multilayer reflective film outside a circuit pattern region formed in the light absorber layer of a reflective mask. In Patent Document 1, by using this groove region as a light-shielding frame (light-shielding region) for EUV light, reflection of EUV light in this light-shielding region is suppressed even when the light absorber layer is thin.

[0007] Japanese Patent Application Laid-Open No. 2009-212220

[0008] However, light sources that generate EUV light often emit not only light in the EUV region (EUV light) with a wavelength of around 13.5 nm, but also light in the deep ultraviolet region with a wavelength ranging from 190 nm to 270 nm. In this disclosure, the deep ultraviolet region with a wavelength ranging from 190 nm to 270 nm is sometimes referred to as DUV (Deep Ultraviolet). Light near this deep ultraviolet region is generally also referred to as out-of-band light. Therefore, out-of-band light is also incident on a reflective mask along with EUV light. For this reason, it is desirable that the light-shielding region of a reflective mask not only ensures EUV light-shielding performance but also has a sufficiently low reflectance for out-of-band light. Therefore, the light-shielding region of a reflective mask is also required to ensure light-shielding performance against out-of-band light. However, while the method proposed in the above-mentioned Patent Document 1 ensures a certain degree of EUV light-shielding performance in the light-shielding region of the reflective mask, it is not necessarily sufficient. Furthermore, the method proposed in Patent Document 1 may not be able to sufficiently ensure the light-shielding performance against the out-of-band light in the light-shielding region of the reflective mask. Furthermore, in recent years, exposure apparatuses with larger numerical apertures (NA) in the projection optical systems have been considered in order to improve resolution. Considering the use of such exposure apparatuses, it is expected that the reflection of EUV light and out-of-band light in the light-shielding region will be further reduced.

[0009] Therefore, the present disclosure has been made in consideration of such conventional problems, and its object is, first, to provide a reflective mask blank and a reflective mask for manufacturing a reflective mask that can reduce reflection of EUV light and out-of-band light in the light-shielding region of the reflective mask and has good light-shielding performance in the light-shielding region. A second object of the present disclosure is to provide a method for manufacturing a semiconductor device using this reflective mask.

[0010] In order to solve the problems of the past, the present inventors have continued their intensive research focusing on the configuration of a light-shielding film that forms a light-shielding region of a reflective mask, and have completed the following configuration: (Configuration 1) A reflective mask blank comprising: a substrate, a multilayer reflective film provided on the substrate, an absorber film provided on the multilayer reflective film, and a light-shielding film provided on the absorber film, the light-shielding film including a plurality of layers, wherein an absolute difference in refractive index for EUV light between adjacent layers of the plurality of layers is 0.06 or less, and an absolute difference in extinction coefficient for EUV light between the adjacent layers is 0.03 or less.

[0011] (Configuration 2) A reflective mask blank comprising: a substrate; a multilayer reflective film provided on the substrate; an absorber film provided on the multilayer reflective film; and a light-shielding film provided on the absorber film, wherein the light-shielding film has a refractive index with respect to EUV light that decreases toward the substrate in a film thickness direction.

[0012] (Structure 3) The reflective mask blank according to Structure 1 or 2, characterized in that the absolute difference between the refractive index for the EUV light of the outermost surface of the light-shielding film farthest from the substrate or the uppermost layer of the light-shielding film farthest from the substrate and the refractive index for the EUV light in a vacuum is 0.06 or less. (Structure 4) The reflective mask blank according to any of Structures 1 to 3, characterized in that the absolute difference between the extinction coefficient for the EUV light of the outermost surface of the light-shielding film farthest from the substrate or the uppermost layer of the light-shielding film farthest from the substrate and the extinction coefficient for the EUV light in a vacuum is 0.03 or less.

[0013] (Structure 5) The reflective mask blank according to any one of Structures 1 to 4, wherein the light-shielding film contains at least one of chromium, tantalum, and silicon. (Structure 6) The reflective mask blank according to any one of Structures 1 to 5, wherein the light-shielding film has an extinction coefficient for the EUV light that increases toward the substrate in a film thickness direction.

[0014] (Structure 7) The reflective mask blank according to any one of Structures 1 to 6, wherein the light-shielding film is a compositionally graded film made of a plurality of elements, in which the composition ratio of the plurality of elements changes continuously or stepwise in the film thickness direction.

[0015] (Structure 8) The reflective mask blank according to any one of Structures 1 to 7, wherein the multilayer reflective film includes a plurality of pairs of low refractive index layers and high refractive index layers, and the multilayer reflective film has an interface between the low refractive index layers and the high refractive index layers that are in contact with each other in some regions, and does not have the interface in other regions.

[0016] (Structure 9) The reflective mask blank according to any one of Structures 1 to 8, characterized in that it has a first etching mask film between the absorber film and the light-shielding film. (Structure 10) The reflective mask blank according to any one of Structures 1 to 9, characterized in that it has a second etching mask film on the light-shielding film.

[0017] (Structure 11) A reflective mask manufactured from the reflective mask blank according to any one of Structures 1 to 10, the reflective mask having a transfer pattern formed in the absorber film and a light-shielding pattern formed in the light-shielding film, the light-shielding pattern being provided on the periphery of an area including the transfer pattern so that the transfer pattern is exposed.

[0018] (Configuration 12) A method for manufacturing a semiconductor device, comprising: using the reflective mask according to configuration 11, transferring the transfer pattern of the reflective mask onto a transfer target on a semiconductor substrate.

[0019] According to the present disclosure, it is possible to provide a reflective mask blank for manufacturing a reflective mask that can reduce reflection of EUV light and out-of-band light in the light-shielding region of the reflective mask and has good light-shielding performance in the light-shielding region, and a reflective mask. Furthermore, according to the present disclosure, it is possible to provide a method for manufacturing a semiconductor device that can perform high-precision pattern transfer using this reflective mask.

[0020] FIG. 1 is a schematic cross-sectional view showing a reflective mask blank according to a first embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing a reflective mask blank according to a second embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view showing a reflective mask according to an embodiment of the present disclosure. FIG. 4 is a plan view of a reflective mask showing an example of a transfer pattern region and a light-shielding region. FIG. 5 is a schematic cross-sectional view showing a first step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 6 is a schematic cross-sectional view showing a second step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 7 is a schematic cross-sectional view showing a third step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 8 is a schematic cross-sectional view showing a fourth step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 9 is a schematic cross-sectional view showing a fifth step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 10 is a schematic cross-sectional view showing a sixth step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 11 is a schematic cross-sectional view showing a seventh step of manufacturing a reflective mask from the reflective mask blank of the present disclosure. FIG. 12 is a schematic cross-sectional view showing an eighth step of manufacturing a reflective mask from the reflective mask blank of the present disclosure.

[0021]

[0023] Embodiments of the present disclosure will be described in detail below. [Reflective Mask Blank] First, the reflective mask blank of the present disclosure will be described. Note that in this disclosure, refractive indexes and extinction coefficients may be described without mentioning the wavelength of reference light or electromagnetic waves, but unless otherwise specified, these refractive indexes and extinction coefficients refer to values ​​for EUV light.

[0022] First Embodiment Fig. 1 is a schematic cross-sectional view showing a reflective mask blank according to a first embodiment of the present disclosure. As shown in Fig. 1, a reflective mask blank 10A according to this first embodiment includes a substrate 1, a multilayer reflective film 2 provided on a front surface (also referred to as the "first main surface") of the substrate 1, a protective film 3 provided on the multilayer reflective film 2, an absorber film 4 provided on the protective film 3, a first etching mask film 5 provided on the absorber film 4, a light-shielding film 6A provided on the first etching mask film 5, and a second etching mask film 7 provided on the light-shielding film 6A. The reflective mask blank 10A also includes a back surface conductive film 8 on a back surface (also referred to as the "second main surface") of the substrate 1. In this first embodiment, the light-shielding film 6A includes multiple layers and is formed of a three-layer stack of a first layer 6a, a second layer 6b, and a third layer 6c, from the side closest to the substrate 1. However, the light-shielding film 6A may be a laminated film made up of two layers or four or more layers. In the following, a case where the light-shielding film 6A is a laminated film made up of three layers will be described.

[0023] 3 and 4, in a reflective mask 20 manufactured from the reflective mask blank 10A of the first embodiment, the light-shielding pattern formed in the light-shielding film 6A is provided on the periphery of an area A containing the transfer pattern (hereinafter also referred to as a "transfer pattern area") so as to expose the transfer pattern formed in the absorber film 4. The light-shielding pattern forms a light-shielding area B.

[0024] In the first embodiment, the light-shielding film 6A is characterized in that the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the adjacent layers is 0.03 or less. Here, "absolute difference" means the absolute value of the difference between two values. The light-shielding film 6A is formed of a three-layer stack of a first layer 6a, a second layer 6b, and a third layer 6c, from the side closest to the substrate 1. In this case, the absolute difference in refractive index for EUV light between the first layer 6a and the second layer 6b is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the first layer 6a and the second layer 6b is 0.03 or less. Furthermore, the absolute difference in refractive index for EUV light between the second layer 6b and the third layer 6c is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the second layer 6b and the third layer 6c is 0.03 or less.

[0025] That is, when the light-shielding film 6A is a stacked film consisting of M layers, all of the M layers satisfy the following conditions: The absolute difference in refractive index for EUV light between the Nth layer from the substrate side of the light-shielding film 6A and the (N+1)th layer in contact with the Nth layer is 0.06 or less; and The absolute difference in extinction coefficient for EUV light between the Nth layer and the (N+1)th layer is 0.03 or less, where M is an integer equal to or greater than 2, and N is an integer equal to or greater than 1 and less than M.

[0026] Here, EUV light refers to light (electromagnetic waves) with a wavelength of around 13.5 nm, including 13.5 nm. In this disclosure, EUV light specifically refers to light in the wavelength range of 13.395 nm to 13.665 nm. In this disclosure, light includes not only visible light but also electromagnetic waves.

[0027] In the first embodiment, as described above, the light-shielding film 6A includes multiple layers (a first layer 6a, a second layer 6b, and a third layer 6c). The absolute difference in refractive index for EUV light between adjacent layers among the multiple layers is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between adjacent layers among the multiple layers is 0.03 or less. The smaller the absolute difference in refractive index for EUV light and the absolute difference in extinction coefficient between adjacent layers among the multiple layers, the lower the reflectivity of EUV light at the interfaces between the layers. The reduction in reflectivity of EUV light at each interface can suppress reflection of EUV light from the entire light-shielding film. Furthermore, by satisfying the configuration features of the light-shielding film disclosed herein, reflection from the light-shielding film can be suppressed not only for EUV light but also for the out-of-band light described above. In the present disclosure, out-of-band light refers to light in the deep ultraviolet (DUV) range, for example, with wavelengths ranging from 190 nm to 270 nm (hereinafter also referred to as "DUV light").

[0028] Furthermore, in the first embodiment, although not essential, it is preferable that in the light-shielding film 6A, the absolute difference in refractive index for light with a wavelength of 230 nm between adjacent layers among the plurality of layers is 2.0 or less, and the absolute difference in extinction coefficient for light with a wavelength of 230 nm between the adjacent layers is 2.0 or less.

[0029] In the first embodiment, the light-shielding film 6A is formed of a three-layer laminate film consisting of a first layer 6a, a second layer 6b, and a third layer 6c, from the side closest to the substrate 1. In this case, it is preferable that the absolute difference in refractive index between the first layer 6a and the second layer 6b for light with a wavelength of 230 nm is 2.0 or less, and that the absolute difference in extinction coefficient between the first layer 6a and the second layer 6b for light with a wavelength of 230 nm is 2.0 or less. It is also preferable that the absolute difference in refractive index between the second layer 6b and the third layer 6c for light with a wavelength of 230 nm is 2.0 or less, and that the absolute difference in extinction coefficient between the second layer 6b and the third layer 6c for light with a wavelength of 230 nm is 2.0 or less.

[0030] That is, when the light-shielding film 6A is a laminated film consisting of M layers, it is preferable that all of the M layers satisfy the following condition: It is preferable that the absolute difference in refractive index for light with a wavelength of 230 nm between the Nth layer from the substrate side of the light-shielding film 6A and the (N+1)th layer in contact with the Nth layer is 2.0 or less. It is also preferable that the absolute difference in extinction coefficient for light with a wavelength of 230 nm between the Nth layer and the (N+1)th layer is 2.0 or less. Here, M is an integer of 2 or more, and N is an integer of 1 or more and less than M. This can further suppress reflection at the light-shielding film even with respect to DUV light.

[0031] In the first embodiment, it is preferable that the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers (first layer 6a, second layer 6b, third layer 6c) of the light-shielding film 6A is greater than 0 (zero). Similarly, it is preferable that the absolute difference in extinction coefficient for EUV light between adjacent layers is also greater than 0 (zero). This makes it possible to reduce reflection of EUV light and DUV light in the light-shielding film (light-shielding region). The same applies to the refractive index and extinction coefficient for light with a wavelength of 230 nm.

[0032] In the first embodiment, it is preferable that the light-shielding film 6A has a smaller refractive index for EUV light as the layer is closer to the substrate 1 in the film thickness direction, and a larger extinction coefficient as the layer is closer to the substrate 1. This makes it possible to more effectively reduce reflection of EUV light and DUV light at the light-shielding film (light-shielding region).

[0033] When the light-shielding film 6A includes multiple layers and is formed as a stack of three layers, a first layer 6a, a second layer 6b, and a third layer 6c, from the side closest to the substrate 1, as in the first embodiment, the refractive index n of each layer with respect to EUV light is as follows: The refractive index n of the bottom layer (the first layer 6a) closest to the substrate 1 is preferably 0.88 or more. The refractive index n of the bottom layer (the first layer 6a) is preferably 0.97 or less. The refractive index n of the top layer (the third layer 6c) farther from the substrate 1 is preferably 0.94 or more. The refractive index n of the top layer (the third layer 6c) is preferably 1.01 or less. The refractive index n of the intermediate layer (the second layer 6b) between the bottom layer and the top layer is preferably 0.91 or more. The refractive index n of the intermediate layer (the second layer 6b) is preferably 0.97 or less.

[0034] The extinction coefficient k of each layer with respect to EUV light is as follows: The extinction coefficient k of the bottom layer (the first layer 6a) closest to the substrate 1 is preferably 0.01 or more. The extinction coefficient k of the bottom layer (the first layer 6a) is preferably 0.05 or less. The extinction coefficient k of the top layer (the third layer 6c) farther from the substrate 1 is preferably 0.0 or more. The extinction coefficient k of the top layer (the third layer 6c) is preferably 0.03 or less. The extinction coefficient k of the intermediate layer (the second layer 6b) between the bottom layer and the top layer is preferably 0.01 or more. The extinction coefficient k of the intermediate layer (the second layer 6b) is preferably 0.04 or less.

[0035] The light-shielding film 6A preferably has a minimum reflectance value for light with a wavelength near 13.53 nm. The light-shielding film 6A preferably has a minimum reflectance value within a light wavelength range of 13.40 nm or more and 13.67 nm or less. The reflectance spectrum of the light-shielding film 6A preferably has a minimum value within a wavelength range of 13 nm or more and 14 nm or less, more preferably within a wavelength range of 13.40 nm or more and 13.67 nm or less. The light-shielding films of each example described below satisfied all of the above conditions. The light-shielding film 6A having such a configuration can effectively suppress reflection of EUV light. The same applies to the light-shielding film 6B in the second embodiment described below. Furthermore, as long as the light-shielding film 6A can reduce the reflectance of DUV light to a desired value, the shape of the reflectance spectrum of the light-shielding film 6A in the DUV wavelength range is not particularly limited. However, the reflectance spectrum of the light-shielding film 6A can have a maximum value, for example, within a wavelength range of 190 nm to 270 nm. For example, if the maximum reflectance of the light-shielding film 6A within the wavelength range of 190 nm to 270 nm is 3.0% or less and the slope of the tangent to the reflectance spectrum of the light-shielding film 6A is positive, the reflectance of light within a wavelength range of less than 190 nm, which may cause unwanted exposure of the resist film, can also be reduced. Furthermore, if the light-shielding film 6A has the above-described configuration, even if a slight change in the thickness of the light-shielding film 6A causes a slight shift in the wavelength at which the reflectance of the light-shielding film 6A is maximized within the wavelength range of 190 nm to 270 nm, the reflectance of not only light within the wavelength range of 190 nm to 270 nm but also light within a wavelength range less than 190 nm can be reduced. The same applies to the light-shielding film 6B in the second embodiment described below. In the first embodiment, the case where the light-shielding film 6A is formed of a three-layer laminate film consisting of a first layer 6a, a second layer 6b, and a third layer 6c has been described. However, in the present disclosure, the number of layers in the laminate film that forms the light-shielding film does not need to be particularly restricted.

[0036] The material of the light-shielding film 6A is not particularly limited as long as it satisfies the characteristics of the light-shielding film configuration of the present disclosure. For example, the material of the light-shielding film 6A may include a material containing one or more elements selected from Cr, Ta, Ru, Rh, Mo, Nb, Ti, Zr, Y, Si, Pd, Ag, Pt, Au, Ir, W, Co, Mn, Sn, V, Ni, Fe, Hf, Cu, Te, Zn, Mg, Ge, Al, etc. Particularly preferred materials for the light-shielding film 6A include a material containing one or more elements selected from Cr, Ta, and Si. In addition to the above, the material of the light-shielding film 6A may further include at least one element selected from O, N, C, B, H, and rare gases (He, Ne, Ar, Kr, Xe, etc.). When the light-shielding film 6A contains a rare gas as its material, the content thereof is preferably 5 atomic % or less, and more preferably 3 atomic % or less.

[0037] The properties of thin films, including the light-shielding film 6A, such as the refractive index and extinction coefficient, are not determined solely by the composition of the thin film. The film density and crystalline state of the thin film also affect the properties of the thin film. Therefore, the conditions for forming a thin film by sputtering are adjusted to ensure that the thin film has the desired properties. For example, a wide range of conditions, such as the pressure in the film formation chamber, the power applied to the sputtering target, the positional relationship between the target and the substrate, and the target formation conditions, are adjusted to ensure that the thin film has the desired properties. Furthermore, these film formation conditions are specific to the film formation apparatus and are adjusted as appropriate to ensure that the thin film has the desired properties.

[0038] When the light-shielding film 6A includes, for example, multiple layers (first layer 6a, second layer 6b, third layer 6c) as in the first embodiment, the materials of each of the multiple layers may be selected from the materials described above. In this case, the light-shielding film may be composed of multiple layers having different constituent elements, or multiple layers having the same constituent elements but different composition ratios. The light-shielding film 6A may be a film whose composition changes stepwise or continuously in the film thickness direction. When the light-shielding film 6A is a film whose composition changes stepwise or continuously in the film thickness direction, the region where the content of the first element is highest can be considered as the first layer, the region where the content of the second element is highest can be considered as the second layer, and the region where the content of the nth element is highest can be considered as the nth layer. In this case, the light-shielding film 6A is a stacked film consisting of the first layer, the second layer, the nth layer, and so on. Here, n is a natural number greater than or equal to 2. The refractive index and extinction coefficient of the first layer respectively refer to the average refractive index and extinction coefficient in the film thickness direction of the first layer. The same applies to the second layer, ..., nth layer. The stacking order of the first layer, second layer, ..., nth layer is not particularly limited.

[0039] The absolute difference in refractive index for EUV light between the light-shielding film 6A and the film below the light-shielding film 6A (first etching mask film 5 or absorber film 4) does not necessarily have to be small, but it is preferable that it is small. For example, the absolute difference in refractive index for EUV light is preferably 0.06 or less. Similarly, the absolute difference in extinction coefficient for EUV light is preferably small, for example, 0.04 or less. This makes it possible to more effectively reduce the reflection of EUV light and DUV light in the light-shielding film 6A (light-shielding region B). It is preferable that the absolute differences in both refractive index and extinction coefficient for EUV light are greater than 0.

[0040] The absolute difference in refractive index for light with a wavelength of 230 nm between the light-shielding film 6A and the film below it (first etching mask film 5 or absorber film 4) does not necessarily have to be small, but is preferably 2.0 or less, for example. Similarly, the absolute difference in extinction coefficient for light with a wavelength of 230 nm is also preferably small, and is preferably 2.5 or less. This makes it possible to more effectively reduce reflection of DUV light in the light-shielding film 6A (light-shielding region B).

[0041] Of the multiple layers of the light-shielding film 6A, the refractive index and extinction coefficient of the top layer (the third layer 6c) or the outermost surface farthest from the substrate 1 are preferably close to the refractive index and extinction coefficient of the EUV light in a vacuum. Specifically, of the multiple layers of the light-shielding film 6A, the absolute difference between the refractive index of the top layer (the third layer 6c) or the outermost surface farthest from the substrate 1 and the refractive index of the EUV light in a vacuum is preferably 0.06 or less. Furthermore, the absolute difference between the extinction coefficient of the top layer (the third layer 6c) or the outermost surface farthest from the substrate 1 and the extinction coefficient of the EUV light in a vacuum is preferably 0.03 or less. This makes it possible to more effectively reduce reflection of EUV light and DUV light in the light-shielding film 6A (light-shielding region B). The material of the top layer of the light-shielding film 6A in this case is not particularly limited, but may be, for example, SiO ２ , TaBO, CrOCN, TaON, TaO, CrO, and CrON are preferred.

[0042] Furthermore, although not shown, when a light-shielding pattern is formed after the absorber film pattern is formed, the light-shielding film 6A can function as a mask when etching the first etching mask film 5 (between the absorber film 4 and the light-shielding film 6) or the absorber film 4. Therefore, by using the reflective mask blank 10A of the first embodiment, it is possible to form an absorber film pattern with higher accuracy. In particular, if the light-shielding film 6A is a laminated film in which layers with high etching selectivity are stacked one on top of the other, the cross-sectional shape of the light-shielding film 6A after etching will be better, and the accuracy of the absorber film pattern can be further improved.

[0043] In the case of EUV exposure, the substrate 1 in the reflective mask blank 10A of the first embodiment has a thickness of 0±1.0×10 －７ / °C, more preferably 0±0.3×10 －７ Materials having a low thermal expansion coefficient within this range are preferably used. 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.

[0044] The first main surface of the substrate 1 on which the transfer pattern is formed is surface-processed to have a high degree of flatness in order to improve at least the pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the first main surface on which the transfer pattern is formed preferably has a flatness of 0.1 μm or less, particularly preferably 0.05 μm or less, over an area of, for example, 142 mm × 142 mm. The second main surface of the substrate 1 opposite the first main surface on which the transfer pattern is formed is the surface that is electrostatically chucked when set in an exposure apparatus, and has a flatness of 0.1 μm or less, preferably 0.05 μm or less, over an area of, for example, 142 mm × 142 mm.

[0045] As described above, the substrate 1 is made of SiO ２ -TiO ２ Materials having a low thermal expansion coefficient, such as silicon-based glass, are preferably used. It is difficult to achieve high surface smoothness, for example, a root-mean-square roughness (Rq) of 0.1 nm or less, by precision polishing with such materials. Therefore, in order to reduce the surface roughness of the substrate 1 or to reduce defects on the surface of the substrate 1, an underlayer (not shown) may be formed on the first main surface of the substrate 1. The material for such an underlayer does not need to be transparent to the exposure light, and is preferably selected from materials that provide high smoothness and good defect quality when the surface of the underlayer is precision polished. For example, Si or a silicon compound containing Si (e.g., SiO ２, SiON, etc.) are preferably used as the material for the underlayer because they can obtain high smoothness when precision polished and have good defect quality. Si is particularly preferred as the material for the underlayer.

[0046] The surface of the underlayer is preferably precision-polished to have the smoothness required for a reflective mask blank substrate. The surface of the underlayer is desirably precision-polished to a root-mean-square roughness (Rq) of 0.15 nm or less, particularly preferably 0.1 nm or less. Furthermore, in consideration of the influence on the surface of the multilayer reflective film 2 formed on the underlayer, the surface of the underlayer is desirably precision-polished so that, in relation to the maximum height (Rmax), Rmax / Rq is preferably 2 to 10, particularly preferably 2 to 8. The film thickness of the underlayer is preferably in the range of 10 nm to 300 nm, for example.

[0047] The multilayer reflective film 2 provided on the first main surface of the substrate 1 (or on the underlayer if one is formed) includes a plurality of pairs of low-refractive-index layers and high-refractive-index layers. Specifically, the multilayer reflective film 2 is a multilayer film in which low-refractive-index layers and high-refractive-index layers are alternately stacked, and typically, a multilayer film is used in which first thin films (high-refractive-index layers) made of heavy elements or their compounds and second thin films (low-refractive-index layers) made of light elements or their compounds are alternately stacked in approximately 30 to 60 periods. For example, a Mo / Si periodic stacked film in which Mo films and Si films are alternately stacked in approximately 40 periods is preferably used as the multilayer reflective film 2 for EUV light with a wavelength of 13 to 14 nm. Other examples of the multilayer reflective film 2 used in the EUV light region include a Ru / Si periodic multilayer film, a Mo / Be periodic multilayer film, a Mo compound / Si compound periodic multilayer film, a Si / Nb periodic multilayer film, a Si / Mo / Ru periodic multilayer film, a Si / Mo / Ru / Mo periodic multilayer film, and a Si / Ru / Mo / Ru periodic multilayer film. The material may be appropriately selected depending on the exposure wavelength. Furthermore, another functional layer may be formed between the low refractive index layer and the high refractive index layer. For example, the other functional layer may be a film that reduces or suppresses diffusion between the low refractive index layer and the high refractive index layer.

[0048] In the first embodiment, the multilayer reflective film 2 is preferably modified by laser light irradiation or ion implantation. In the laser-irradiated region of the multilayer reflective film 2, diffusion occurs between the adjacent low-refractive index layers and high-refractive index layers. Therefore, it is presumed that this diffusion results in an interface between the low-refractive index layers and the high-refractive index layers being eliminated. This further reduces the reflection of EUV light and DUV light in the light-shielding film 6A (light-shielding region B). This allows the light-shielding film 6A to be made thinner, thereby improving the accuracy of the absorber film pattern. Even if the other functional layers described above are formed between the low-refractive index layers and the high-refractive index layers, diffusion can be induced by laser light irradiation or ion implantation.

[0049] In the multilayer reflective film 2, a state in which diffusion occurs or a state in which no interface is present specifically refers to a film thickness of the diffusion region, described below, of 20 nm or greater. When the multilayer reflective film 2 is analyzed by energy dispersive X-ray spectroscopy (EDX), the diffusion region has a first difference D1 obtained by subtracting a first minimum value Y1 (atomic %) of the content of a first element having the highest content in the multilayer reflective film 2 from a first maximum value X1 (atomic %) of the content of the first element, which is 30 or less, and a second difference D2 obtained by subtracting a second minimum value Y2 (atomic %) of the content of a second element having the second highest content in the multilayer reflective film 2 from a second maximum value X2 (atomic %) of the content of the second element, which is 30 or less. That is, (X1-Y1)≦30 and (X2-Y2)≦30. Furthermore, both (X1-Y1) and (X2-Y2) are 0 or greater. It is more preferable that the film thickness of the diffusion region be 30 nm or greater. In the present disclosure, the depth resolution of the EDX is set to 1.56 nm.

[0050] The laser light irradiation may be performed at any stage after the formation of the multilayer reflective film 2. For example, it is preferable to irradiate the multilayer reflective film 2 corresponding to the light-shielding region B, or the multilayer reflective film 2 and the protective film 3, with laser light after the formation of the multilayer reflective film 2 or the protective film 3 and before the formation of the absorber film 4. Alternatively, the multilayer reflective film 2 (and the protective film 3) in the region corresponding to the light-shielding region B may be irradiated with laser light after other films such as the absorber film 4 or the light-shielding film 6A are formed on the multilayer reflective film 2 (and the protective film 3). Alternatively, the multilayer reflective film 2 (and the protective film 3) in the region corresponding to the light-shielding region B may be irradiated with laser light at any stage in producing a reflective mask from a reflective mask blank. The multilayer reflective film 2 (and the protective film 3) may be irradiated with laser light directly, or may be irradiated with laser light via another film or via the back surface of the substrate (and the back surface conductive film).

[0051] The light source for the laser light irradiation is, for example, F ２ laser (wavelength approximately 157 nm), ArF excimer laser (wavelength approximately 193 nm), KrF excimer laser (wavelength approximately 248 nm), YAG laser 4th harmonic (wavelength approximately 266 nm), XeCl excimer laser (wavelength approximately 308 nm), Ar laser (wavelength approximately 488 nm), YAG laser (wavelength 1064 nm), CO ２ A preferred example is a laser (wavelength 10.6 μm).

[0052] By modifying the multilayer reflective film 2, for example, by irradiating it with laser light, the multilayer reflective film 2 does not have an interface between the low refractive index layer and the high refractive index layer that are in contact with each other in some regions (regions irradiated with laser light), but has the interface in other regions (regions not irradiated with laser light).

[0053] Typically, for the purpose of protecting the multilayer reflective film 2 during patterning or pattern modification of the absorber film 4, it is preferable to provide a protective film 3 (sometimes referred to as a capping layer) on the multilayer reflective film 2. Such a protective film 3 is formed, for example, from a material containing ruthenium as a main component. Examples of materials containing ruthenium as a main component include simple Ru metal, 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), chromium (Cr), and rhenium (Re), and materials containing nitrogen in these alloys. The thickness of the protective film 3 is preferably in the range of, for example, about 1 nm to 5 nm.

[0054] The methods for forming the light-shielding film 6A, the underlayer, the multilayer reflective film 2, and the protective film 3 described above are not particularly limited, but ion beam sputtering, magnetron sputtering, or the like are typically suitable. At least one of the sputtering target and the sputtering gas used to form each film (layer) contains the elements that constitute that film (layer). Using such a sputtering target and sputtering gas, each film (layer) can be formed by adjusting various conditions, such as the power applied to the sputtering target and the gas flow rate, so as to have desired properties (e.g., the refractive index and extinction coefficient of the light-shielding film 6A).

[0055] Next, the absorber film 4 will be described. The absorber film 4 that absorbs EUV light is formed on the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2. The absorber film 4 is a film that absorbs EUV light, which is exposure light. Specifically, the absorber film 4 may have a desired reflectance difference between light reflected from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and light reflected from a transfer pattern (absorber film pattern) 4a formed on the absorber film 4 in a reflective mask 20 (see FIG. 3 ) fabricated using a reflective mask blank. For example, the reflectance difference of the absorber film 4 for EUV light is selected between 0.1% or more and 40% or less.

[0056] In addition to the reflectivity difference, the absorber film 4 may have a desired phase difference between the light reflected from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and the light reflected from the transfer pattern (absorber film pattern) 4 a. When a desired phase difference is present between the light reflected from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and the light reflected from the transfer pattern (absorber film pattern) 4 a, the absorber film 4 in the reflective mask blank may be referred to as a phase shift film. When a desired phase difference is provided between the light reflected from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and the light reflected from the transfer pattern (absorber film pattern) 4 a to improve contrast, the phase difference is preferably set in the range of 170 degrees to 260 degrees, and the reflectivity difference of the absorber film 4 for EUV light is preferably set to 3% or more and 40% or less.

[0057] The absorber film 4 may have a single layer or a laminated structure. In the case of a laminated structure, the absorber film 4 may be a laminated film of the same material or a laminated film of different materials. The laminated film may have a material or composition that changes stepwise and / or continuously in the film thickness direction.

[0058] The material of the absorber film 4 is not particularly limited as long as it absorbs EUV light, can be processed by etching or the like, and has a high etching selectivity with respect to the multilayer reflective film 2 or the protective film 3. The material of the absorber film 4 is preferably capable of being dry-etched with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas. Materials having the above-described functions are preferably selected from the group consisting of palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), osmium (Os), 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), alloys containing two or more metals, or compounds thereof. The compounds may contain oxygen (O), nitrogen (N), carbon (C), boron (B), and / or hydrogen (H) in addition to the metal or alloy.

[0059] The thickness of the absorber film 4 is preferably in the range of, for example, about 30 nm to 100 nm. There are no particular restrictions on the method for forming the absorber film 4, but magnetron sputtering, ion beam sputtering, or the like is usually preferred.

[0060] The absorber film 4 may also be configured as a laminated film of a top layer and other layers made of materials with different etching selectivities from each other. In this case, the absorber film 4 may be configured so that the top layer functions as a hard mask film (etching mask film) for the other layers.

[0061] The reflective mask blank 10A of the first embodiment also includes a first etching mask film 5 between the absorber film 4 and the light-shielding film 6A. The first etching mask film 5 functions as a mask when patterning the absorber film 4 and is made of a material with different etching selectivity from the material of the top layer of the absorber film 4. For example, when the absorber film 4 is Ta alone or a material containing Ta, the first etching mask film 5 can be made of a material such as chromium or a chromium compound, or silicon or a silicon compound. Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, as well as metal silicon (metal silicide) and metal silicon compounds (metal silicide compounds) containing a metal in silicon or a silicon compound. Examples of metal silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C, and H. Furthermore, when the absorber film 4 is made of a material containing Cr, the material of the first etching mask film 5 can be selected from silicon, a silicon compound, a metal silicide, a metal silicide compound, a tantalum compound, etc., which have etching selectivity for materials containing Cr. Examples of tantalum compounds include materials containing Ta and at least one element selected from N, O, C, B, and H.

[0062] Furthermore, the reflective mask blank 10A of the first embodiment has a second etching mask film 7 on the light-shielding film 6A. The second etching mask film 7 functions as a mask when patterning the light-shielding film 6A and is made of a material with etching selectivity different from that of at least the uppermost layer (the third layer 6c) of the light-shielding film 6A. For example, if the uppermost layer (the third layer 6c) of the light-shielding film 6A is made of a material containing silicon or a silicon compound, the second etching mask film 7 can be made of a material containing chromium or tantalum. Examples of materials containing chromium include Cr metal and the above-mentioned chromium compounds. Examples of materials containing tantalum include Ta metal and the above-mentioned tantalum compounds.

[0063] The second etching mask film 7 can be a single layer film or a laminated film including multiple layers. When the second etching mask film 7 includes multiple layers, the second etching mask film 7 may be a laminated film of multiple films made of the same material, or a laminated film of multiple layers made of different materials. For example, the second etching mask film 7 may include a TaBN layer and a CrN layer formed on the TaBN layer. Furthermore, the laminated film may have a material or composition that changes stepwise and / or continuously in the film thickness direction.

[0064] Second Embodiment Fig. 2 is a schematic cross-sectional view showing a reflective mask blank according to a second embodiment of the present disclosure. As shown in Fig. 2, a reflective mask blank 10B according to the second embodiment includes a substrate 1, a multilayer reflective film 2 provided on a front surface (also referred to as a "first main surface") of the substrate 1, a protective film 3 provided on the multilayer reflective film 2, an absorber film 4 provided on the protective film 3, a first etching mask film 5 provided on the absorber film 4, a light-shielding film 6B provided on the first etching mask film 5, and a second etching mask film 7 provided on the light-shielding film 6B. The reflective mask blank 10B also includes a back surface conductive film 8 on a back surface (also referred to as a "second main surface") of the substrate 1.

[0065] The reflective mask blank 10B of the second embodiment differs from the reflective mask blank 10A of the first embodiment in that the light-shielding film 6B is a single-layer film, not a laminated film.

[0066] In the second embodiment, the light-shielding film 6B has a refractive index for EUV light that decreases in the thickness direction toward the substrate 1. By satisfying the structural features of the light-shielding film of the second embodiment, it is possible to suppress reflection of EUV light at the light-shielding film 6B. Furthermore, it is possible to suppress reflection of not only EUV light but also the above-mentioned DUV light at the light-shielding film 6B.

[0067] In order to satisfy the characteristics of the configuration of the light-shielding film of the second embodiment, the light-shielding film 6B is preferably a compositionally graded film composed of a plurality of elements, in which the composition ratio of these elements changes continuously or stepwise in the film thickness direction. Preferred materials for the light-shielding film 6B include the same materials as those for the light-shielding film 6A in the reflective mask blank 10A of the first embodiment. At least one of the sputtering target and sputtering gas used to form the light-shielding film 6B contains elements that constitute the light-shielding film 6B. Using such a sputtering target and sputtering gas, the light-shielding film 6B can be formed by adjusting various conditions, such as the power applied to the sputtering target and the gas flow rate, so that the light-shielding film 6B has the desired properties (refractive index, extinction coefficient).

[0068] In the second embodiment, the light-shielding film 6B preferably has a smaller refractive index for EUV light as it approaches the substrate 1 in its film thickness direction, but preferably has a larger extinction coefficient as it approaches the substrate 1. This makes it possible to more effectively reduce reflection of EUV light and DUV light at the light-shielding film 6B (light-shielding region B). Furthermore, although not limited to this, the above effect can be further enhanced if the extinction coefficient of the light-shielding film 6B for light with a wavelength of 230 nm increases as it approaches the substrate 1.

[0069] As described above, in the second embodiment, the light-shielding film 6B is preferably a compositionally graded film. In this case, the refractive index n of the light-shielding film 6B with respect to EUV light is as follows: The refractive index n of the lower region of the light-shielding film closer to the substrate 1 is preferably 0.88 or more. The refractive index n of the lower region is preferably 0.97 or less. The lower region refers to a region extending from 5 nm to 10 nm in the film thickness direction from the interface between the light-shielding film 6B and the first etching mask film 5. The refractive index and extinction coefficient of the lower region refer to the average refractive index and the average extinction coefficient in the film thickness direction of the lower region, respectively. The refractive index n of the upper region of the light-shielding film farther from the substrate 1 is preferably 0.94 or more. The refractive index n of the upper region is preferably 1.01 or less. The upper region refers to a region extending from 5 nm to 10 nm in the film thickness direction from the surface of the light-shielding film 6B farthest from the substrate 1 (the interface with the second etching mask film 7). The refractive index and extinction coefficient of the upper region respectively refer to the average value of the refractive index and the average value of the extinction coefficient in the film thickness direction of the upper region.

[0070] The extinction coefficient k of the light-shielding film 6B for EUV light is as follows: The extinction coefficient k of the lower region of the light-shielding film 6B closer to the substrate 1 is preferably 0.01 or more. The extinction coefficient k of the lower region is preferably 0.06 or less. The extinction coefficient k of the upper region of the light-shielding film 6B farther from the substrate 1 is preferably 0.0 or more. The extinction coefficient k of the upper region is preferably 0.03 or less.

[0071] The absolute difference in refractive index for EUV light between the lower region of the light-shielding film 6B and the film below the light-shielding film 6B (first etching mask film 5 or absorber film 4) does not necessarily have to be small, but it is preferable that it is small. For example, the absolute difference in refractive index is preferably 0.06 or less. Similarly, the absolute difference in extinction coefficient for EUV light is preferably small, for example, 0.04 or less. This makes it possible to more effectively reduce reflection of EUV light and DUV light at the light-shielding film 6B (light-shielding region B).

[0072] The absolute difference in refractive index for light with a wavelength of 230 nm between the lower region and the film below the light-shielding film 6B (first etching mask film 5 or absorber film 4) does not necessarily have to be small, but is preferably 2.0 or less, for example. Similarly, the absolute difference in extinction coefficient for light with a wavelength of 230 nm is also preferably small, and is preferably 2.5 or less. This makes it possible to more effectively reduce reflection of DUV light in the light-shielding film 6B (light-shielding region B).

[0073] The refractive index and extinction coefficient for EUV light of the upper region or the outermost surface farthest from the substrate of the light-shielding film 6B are preferably close to the refractive index and extinction coefficient for EUV light in a vacuum, respectively. Specifically, the absolute difference between the refractive index for EUV light of the upper region or the outermost surface farthest from the substrate and the refractive index for EUV light in a vacuum is preferably 0.06 or less. Furthermore, the absolute difference between the extinction coefficient for EUV light of the upper region or the outermost surface farthest from the substrate and the extinction coefficient for EUV light in a vacuum is preferably 0.03 or less. This makes it possible to more effectively reduce reflection of EUV light and DUV light at the light-shielding film 6B (light-shielding region B).

[0074] Furthermore, the refractive index and extinction coefficient for light with a wavelength of 230 nm in the upper region or the outermost surface farthest from the substrate of the light-shielding film 6B are preferably close to the refractive index and extinction coefficient for light with a wavelength of 230 nm in a vacuum, respectively. Specifically, the absolute difference between the refractive index for light with a wavelength of 230 nm in the upper region or the outermost surface farthest from the substrate and the refractive index for light with a wavelength of 230 nm in a vacuum is preferably 2.0 or less. Furthermore, the absolute difference between the extinction coefficient for light with a wavelength of 230 nm in the upper region or the outermost surface farthest from the substrate and the extinction coefficient for light with a wavelength of 230 nm in a vacuum is preferably 2.0 or less. This makes it possible to more effectively reduce reflection of DUV light in the light-shielding film 6B (light-shielding region B).

[0075] The absolute difference between the refractive index for EUV light of the upper region of the light-shielding film 6B and the refractive index for EUV light of the lower region of the light-shielding film 6B is preferably 0.08 or less. Furthermore, the absolute difference between the extinction coefficient for EUV light of the upper region and the extinction coefficient for EUV light of the lower region is preferably 0.03 or less. This makes it possible to more effectively reduce reflection of EUV light and DUV light at the light-shielding film 6B (light-shielding region B).

[0076] Furthermore, the absolute difference between the refractive index of the upper region for light with a wavelength of 230 nm and the refractive index of the lower region for light with a wavelength of 230 nm is preferably 2.0 or less. Furthermore, the absolute difference between the extinction coefficient of the upper region for light with a wavelength of 230 nm and the extinction coefficient of the lower region for light with a wavelength of 230 nm is preferably 2.5 or less, and more preferably 2.0 or less. This makes it possible to more effectively reduce reflection of DUV light at the light-shielding film 6B (light-shielding region B).

[0077] Other than the light-shielding film 6B, the configurations of the substrate 1, underlayer (not shown), multilayer reflective film 2, protective film 3, absorber film 4, first etching mask film 5, and second etching mask film 7 in the reflective mask blank 10B of the second embodiment are all the same as those of these films in the reflective mask blank 10A of the first embodiment described above. Furthermore, the modification of the multilayer reflective film 2 by irradiation with laser light or ion implantation is also the same as in the first embodiment.

[0078] The reflective mask blank of the present disclosure has been described above with reference to the first and second embodiments, but according to the reflective mask blank of the present disclosure, for example, it is possible to reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region of a reflective mask manufactured from this reflective mask blank, and to achieve good light-shielding performance in the light-shielding region. Specifically, according to the reflective mask blank of the present disclosure, it is possible to reduce the reflectance of EUV light in the light-shielding region of a reflective mask to, for example, 0.1% or less, and the reflectance of DUV light to, for example, 3.0% or less.

[0079] [Reflective Mask] Next, a reflective mask according to the present disclosure will be described. FIG. 3 is a schematic cross-sectional view showing a reflective mask 20 according to an embodiment of the present disclosure. FIG. 4 is a plan view of the reflective mask 20 showing an example of a transfer pattern region and a light-shielding region. As shown in FIG. 3, the reflective mask 20 according to an embodiment of the present disclosure is manufactured using, for example, the above-described reflective mask blank 10A (10B), and has a transfer pattern 4a formed in the absorber film 4 and a light-shielding pattern formed in the light-shielding film 6A (6B). As shown in FIG. 4, the light-shielding pattern is provided on the periphery of a transfer pattern region A containing the transfer pattern 4a so that the transfer pattern 4a is exposed, thereby forming a light-shielding region B.

[0080] For example, the substrate 1 may have a rectangular shape with dimensions of approximately 152.0 mm x approximately 152.0 mm (6-inch square). In this case, the transfer pattern area A may be an area with dimensions of 132 mm x 132 mm, and the light-shielding area B may be a strip-shaped area with a width of 2.0 mm to 4.0 mm.

[0081] According to the reflective mask 20 of this embodiment, it is possible to reduce the reflection of both EUV light and out-of-band light in the light-shielding region B of the reflective mask 20, thereby making it possible to provide a reflective mask 20 with good light-shielding performance in the light-shielding region B.

[0082] The present disclosure also provides reflective masks of the following configurations A and B. (Configuration A) A reflective mask comprising: a substrate, a multilayer reflective film provided on the substrate, an absorber film provided on the multilayer reflective film, a light-shielding film provided on the absorber film, a transfer pattern formed on the absorber film, and a light-shielding pattern formed on the light-shielding film, wherein the light-shielding film includes a plurality of layers, wherein an absolute difference in refractive index for EUV light between adjacent layers of the plurality of layers in the light-shielding film is 0.06 or less and an absolute difference in extinction coefficient for EUV light between the adjacent layers is 0.03 or less, and the light-shielding pattern is provided on the periphery of an area including the transfer pattern so that the transfer pattern is exposed.

[0083] (Structure B) A reflective mask comprising: a substrate; a multilayer reflective film provided on the substrate; an absorber film provided on the multilayer reflective film; a light-shielding film provided on the absorber film; a transfer pattern formed on the absorber film; and a light-shielding pattern formed on the light-shielding film, wherein the light-shielding film has a refractive index for EUV light that decreases as it approaches the substrate in a film thickness direction, and the light-shielding pattern is provided on the periphery of an area including the transfer pattern so that the transfer pattern is exposed.

[0084] Next, a method for manufacturing the reflective mask 20 of this embodiment will be described. Figures 5A to 5H are schematic cross-sectional views showing the steps for manufacturing the reflective mask 20 from the reflective mask blank 10A (or 10B) of this embodiment.

[0085] First, in the first step, a resist for electron beam lithography is applied onto the above-mentioned reflective mask blank 10A (or 10B) and baked to form a resist film 9 (see FIG. 5A). Subsequently, in the second step, the resist film 9 is lithographed and developed using an electron beam lithography system to form a predetermined resist pattern 9a in the resist film 9 (see FIG. 5B).

[0086] 5A to 5H, the light-shielding film is indicated by the reference symbol 6, which represents the light-shielding film 6A in the reflective mask blank 10A of the first embodiment described above or the light-shielding film 6B in the reflective mask blank 10B of the second embodiment described above. Also, the back surface conductive film 8 is not shown in FIGS. 5A to 5H.

[0087] Thereafter, in the third step, the second etching mask film 7 is patterned by dry etching using the resist pattern 9a as a mask (see FIG. 5C).

[0088] Next, in the fourth step, the light-shielding film 6 is patterned by dry etching using the patterned second etching mask film 7 as a mask (see FIG. 5D). The light-shielding pattern thus formed in the light-shielding film 6 forms the light-shielding region B in the reflective mask 20 that is finally fabricated. The remaining resist pattern 9a is peeled off and removed before or after the step of patterning the light-shielding film 6.

[0089] Next, in the fifth step, a resist film is formed on the reflective mask blank on which the above-mentioned light-shielding pattern has been formed in the same manner as described above, and this resist film is patterned and developed to form a predetermined resist pattern 9b (see Figure 5E).

[0090] Thereafter, in a sixth step, the first etching mask film 5 is patterned by dry etching using the resist pattern 9b as a mask (see FIG. 5F).

[0091] Next, in the seventh step, the absorber film 4 is patterned by dry etching using the patterned first etching mask film 5 as a mask to form an absorber film pattern (see FIG. 5G). This forms a predetermined transfer pattern 4a (see FIG. 3) in the absorber film 4. The remaining resist pattern 9b is peeled off and removed before or after the patterning step of the absorber film 4. Finally, in the eighth step, unnecessary first etching mask film 5 and second etching mask film 7 are appropriately removed to complete a reflective mask 20 (see FIG. 5H).

[0092] In Figures 5A to 5H, the absorber film pattern is formed after the light-shielding pattern is formed. Alternatively, although not shown, the light-shielding pattern may be formed after the absorber film pattern is formed. In this case, the following process can be performed. First, the second etching mask film 7, the light-shielding film 6, and the first etching mask film 5 are etched using the resist pattern as a mask. Then, the absorber film 4 is etched using the etched first etching mask film 5 (and the second etching mask film 7 and the light-shielding film 6) as a mask to form the absorber film pattern (transfer pattern 4a). Furthermore, the light-shielding film is etched using the resist pattern obtained from the newly formed resist film as a mask to form the light-shielding pattern. Thereafter, the remaining second etching mask film 7 is removed as appropriate. Note that unnecessary resist film is peeled off and removed as appropriate at any stage of the above process. Through the above steps, the reflective mask 20 can be obtained.

[0093] [Method of Manufacturing a Semiconductor Device] The present disclosure also provides a method of manufacturing a semiconductor device using the reflective mask 20. That is, by using the reflective mask 20 of the above-described embodiment to expose and transfer the transfer pattern of the reflective mask 20 to a transfer target on a semiconductor substrate, highly accurate pattern transfer can be performed, and a high-quality semiconductor device with few defects can be manufactured.

[0094] The embodiments of the present disclosure will be described in more detail below with reference to examples. Example 1: Using a double-side polishing machine, a SiO 2 substrate was polished in stages with cerium oxide abrasive grains and colloidal silica abrasive grains, and the substrate surface was then surface-treated with low-concentration hydrosilicofluoric acid. ２ -TiO ２ A glass substrate (a 6-inch square substrate with dimensions of approximately 152.0 mm x 152.0 mm and a thickness of approximately 6.35 mm) was prepared. The surface roughness of the resulting glass substrate (Substrate 1) was 0.25 nm in root mean square roughness (Rq). The surface roughness was measured using an atomic force microscope (AFM) over a measurement area of ​​1 μm x 1 μm.

[0095] Next, using an ion beam sputtering apparatus, 40 periods of a Si film (film thickness: 4.0 nm) and a Mo film (film thickness: 3.1 nm) were stacked on the first main surface of the glass substrate 1, and finally a Si film (film thickness: 3.3 nm) was formed to form a multilayer reflective film 2. Furthermore, a protective film 3 (film thickness: 3.5 nm) made of Ru was formed on the multilayer reflective film 2 to obtain a substrate with a multilayer reflective film.

[0096] Next, using a DC magnetron sputtering apparatus, an absorber film 4 was formed on the protective film 3 of the multilayer reflective film-coated substrate obtained above, which was composed of a TaBN film (film thickness: 13.2 nm), a TaBO film (film thickness: 4.9 nm), and a RuN film (film thickness: 30.7 nm) laminated in this order. In addition, a TaB conductive film 8 (film thickness: 70 nm) was formed on the back surface of the multilayer reflective film-coated substrate.

[0097] Subsequently, a DC magnetron sputtering device was used to deposit SiO ２ A first etching mask film 5 (thickness: 16.0 nm) made of a film was formed.

[0098] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 60.4 nm), a RuCrO film (film thickness: 11.5 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a CrN film (film thickness: 24.1 nm) and a RuCrO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n = 0.929, k = 0.039 RuCrO film: n = 0.921, k = 0.027 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 2.711, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.393, 1.286, and 0.001, respectively.

[0099] Subsequently, a second etching mask film 7 (film thickness: 25 nm) made of a TaBN film was formed on the light-shielding film 6A using a DC magnetron sputtering device. In this manner, a reflective mask blank 10A of Example 1 was produced.

[0100] Next, a reflective mask 20 was fabricated using this reflective mask blank 10A according to the manufacturing process described above (see FIGS. 5A to 5H). First, a resist for electron beam lithography was applied to the reflective mask blank 10A and baked to form a resist film 9 (see FIG. 5A). Subsequently, the resist film 9 was written and developed using an electron beam lithography system to form a predetermined resist pattern 9a in the resist film 9 (see FIG. 5B).

[0101] Thereafter, the second etching mask film 7 was patterned by dry etching with a chlorine-based gas using the resist pattern 9a as a mask (see FIG. 5C).

[0102] Next, using the patterned second etching mask film 7 as a mask, SiO ２ The light-shielding film 6A was patterned by successively dry-etching the RuCrO film and the CrN film with a chlorine-based gas containing oxygen (see FIG. 5D). The light-shielding pattern thus formed in the light-shielding film 6A was to form the light-shielding region B in the reflective mask 20 that was finally fabricated. The remaining resist pattern was peeled off and removed before the patterning step of the light-shielding film 6A.

[0103] Next, a resist film was formed in the same manner as above on the reflective mask blank on which the light-shielding pattern had been formed, and this resist film was patterned and developed to form a predetermined resist pattern (see FIG. 5E).

[0104] Thereafter, the first etching mask film 5 was patterned by dry etching using a fluorine-based gas, using the resist pattern as a mask (see FIG. 5F).

[0105] Next, the remaining resist pattern was peeled off and the absorber film 4 was patterned by dry etching using the patterned first etching mask film 5 as a mask (see FIG. 5G). Specifically, the RuN film was etched with a chlorine-based gas containing oxygen, and the absorber film 4 was etched with a fluorine-based gas (CF ４ The TaBO film was then heated with a chlorine-based gas (Cl ２ The TaBN film was then successively etched away using a gas (gas). This resulted in a predetermined transfer pattern being formed in the absorber film 4. Finally, the unnecessary first etching mask film and second etching mask film were removed to produce a reflective mask 20 (see FIG. 5H).

[0106] The reflectance of EUV light and DUV light was measured in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20. The reflectance of EUV light was taken as the average value of the reflectance for light with wavelengths of 13.395 nm to 13.665 nm. The reflectance of DUV light was taken as the average value of the reflectance for light with wavelengths of 190 nm to 270 nm.

[0107] As a result, the reflectance of EUV light in the light-shielding region B of the reflective mask 20 obtained in Example 1 was 0.010%, and the reflectance of DUV light was 1.30%. According to this Example 1, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0108] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0109] Example 2 SiO prepared in the same manner as in Example 1 above ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0110] Next, a RuCrO film (film thickness: 72.8 nm), a CrO film (film thickness: 13.8 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a RuCrO film (film thickness: 24.6 nm) and a CrO film (film thickness: 24.6 nm) in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: RuCrO film: n = 0.921, k = 0.027 CrO film: n = 0.941, k = 0.032 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 2.711, 2.369, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 1.286, 0.849, and 0.001, respectively.

[0111] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 2 was produced.

[0112] Next, this reflective mask blank 10A was used to fabricate a reflective mask 20 by the same manufacturing process as in Example 1. However, in this Example 2, in the patterning process of the light-shielding film 6A, SiO ２ The CrO film and the RuCrO film were successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film 6A.

[0113] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 2 was 0.019%, and the reflectance of DUV light was 2.06%. According to this Example 2, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0114] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0115] Example 3 SiO prepared in the same manner as in Example 1 above ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0116] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 62.9 nm), a TaBO film (film thickness: 10.8 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a CrN film (film thickness: 18.6 nm) and a TaBO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n = 0.929, k = 0.039 TaBO film: n = 0.952, k = 0.029 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0117] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 3 was produced.

[0118] Next, this reflective mask blank 10A was used to fabricate a reflective mask 20 by the same manufacturing process as in Example 1. However, in this Example 3, in the patterning process of the light-shielding film 6A, SiO ２ The light-shielding film 6A was patterned by etching the TaBO film and the CrN film in succession with a chlorine-based gas containing oxygen.

[0119] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 3 was 0.018%, and the reflectance of DUV light was 1.15%. According to this Example 3, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0120] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0121] Example 4 SiO prepared in the same manner as in Example 1 ２ -TiO ２ On a glass substrate 1 of the system, a multilayer reflective film 2 and a protective film 3 were formed in this order in the same manner as in Example 1.

[0122] Next, using a DC magnetron sputtering apparatus, an absorber film 4 was formed on the protective film 3 of the multilayer reflective film-coated substrate obtained above, by laminating a TaBN film (film thickness: 68.0 nm) and a TaBO film (film thickness: 2.0 nm) in this order.

[0123] Subsequently, a first etching mask film 5 was formed on the absorber film 4 by laminating a CrOCN film (film thickness: 6.0 nm) and a TaBO film (film thickness: 4.0 nm) in this order using a DC magnetron sputtering device.

[0124] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 30.9 nm), a TaBO film (film thickness: 10.8 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a CrN film (thickness: 18.2 nm) and a TaBO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n = 0.929, k = 0.039 TaBO film: n = 0.952, k = 0.029 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0125] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 4 was produced.

[0126] Next, this reflective mask blank 10A was used to fabricate a reflective mask 20 by the same manufacturing process as in Example 1. However, in this Example 4, in the patterning process of the light-shielding film 6A, SiO ２The light-shielding film 6A was patterned by successively etching the TaBO film and the CrN film with a chlorine-based gas containing oxygen. In the patterning process of the first etching mask film 5, the TaBO film was successively patterned with a fluorine-based gas, and the CrOCN film was successively patterned with a chlorine-based gas containing oxygen. In the patterning process of the absorber film 4, the TaBO film was successively patterned with a fluorine-based gas, and the TaBN film was successively patterned with a chlorine-based gas.

[0127] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 4 was 0.017%, and the reflectance of DUV light was 1.16%. According to this Example 4, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0128] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0129] Example 5 SiO prepared in the same manner as in Example 1 ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0130] Next, a DC magnetron sputtering device was used to deposit a TaBO film (film thickness: 70.0 nm), a CrO film (film thickness: 27.6 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a TaBO film (film thickness: 30.2 nm) and a CrO film (film thickness: 30.2 nm) in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: TaBO film: n = 0.952, k = 0.029 CrO film: n = 0.941, k = 0.032 SiO ２film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 2.773, 2.369, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 0.791, 0.849, and 0.001, respectively.

[0131] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 5 was produced.

[0132] Next, this reflective mask blank 10A was used to fabricate a reflective mask 20 by the same manufacturing process as in Example 1. However, in this Example 5, in the patterning process of the light-shielding film 6A, SiO ２ The CrO film was etched with a chlorine-based gas containing oxygen, and the TaBO film was etched with a fluorine-based gas in succession, thereby patterning the light-shielding film 6A.

[0133] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 5 was 0.021%, and the reflectance of DUV light was 1.78%. According to this Example 5, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0134] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0135] Example 6 SiO prepared in the same manner as in Example 1２ -TiO ２ A multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were sequentially formed on a glass substrate 1 of the system in the same manner as in Example 1. In this Example 6, between the formation of the protective film 3 and the formation of the absorber film 4, a laser beam was irradiated onto the multilayer reflective film 2 (and the protective film 3) corresponding to the light-shielding region B to form a diffusion region.

[0136] When the multilayer reflective film 2 after irradiation with laser light was observed with an electron microscope, an interface between the Si film (high refractive index layer) and the Mo film (low refractive index layer) was confirmed in the region of the multilayer reflective film 2 that was not irradiated with laser light. On the other hand, no interface between the Si film and the Mo film was confirmed in the region of the multilayer reflective film 2 that was irradiated with laser light. Furthermore, when the multilayer reflective film 2 was analyzed using energy dispersive X-ray spectroscopy with a depth resolution of 1.56 nm, diffusion occurred throughout the entire thickness of the multilayer reflective film 2 in the region that was irradiated with laser light. Specifically, when the total thickness of the multilayer reflective film 2 was 287.3 nm, the first difference D1 obtained by subtracting the first minimum value Y1 (atomic %) of the silicon content, which is the largest content in the multilayer reflective film 2, from the first maximum value X1 (atomic %) of the silicon content was 26. Furthermore, a second difference D2 obtained by subtracting the second minimum value Y2 (atomic %) of the molybdenum content from the second maximum value X2 (atomic %) of the molybdenum content, which was the second largest content in the multilayer reflective coating 2, was 17. That is, in the laser light irradiated region of the multilayer reflective coating 2 of Example 6, the film thickness of the diffusion region was 20 nm or more.

[0137] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 14.4 nm), a TaBO film (film thickness: 9.0 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a CrN film (film thickness: 18.6 nm) and a TaBO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n = 0.929, k = 0.039 TaBO film: n = 0.952, k = 0.029 SiO ２film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0138] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 6 was produced.

[0139] Next, using this reflective mask blank 10A, a reflective mask 20 was fabricated by the same manufacturing process as in Example 1. However, in this Example 6, in the patterning process of the light-shielding film 6A, SiO ２ The light-shielding film 6A was patterned by etching the TaBO film and the CrN film in succession with a chlorine-based gas containing oxygen.

[0140] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B of the reflective mask 20 obtained in Example 6 was 0.011%, and the reflectance of DUV light was 1.13%. According to Example 6, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20. Furthermore, since the film thickness of the light-shielding film 6A could be made smaller, the cross-sectional shape of the light-shielding pattern was also better.

[0141] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0142] Example 7 SiO prepared in the same manner as in Example 1 ２ -TiO ２ On a glass substrate 1 of the system, a multilayer reflective film 2 and a protective film 3 were formed in this order in the same manner as in Example 1.

[0143] Next, an absorber film 4 made of a TaN film (film thickness: 60.0 nm) was formed on the protective film 3 of the multilayer reflective film coated substrate obtained above using a DC magnetron sputtering device.

[0144] Subsequently, a first etching mask film 5 was formed on the absorber film 4 by laminating a CrON film (film thickness: 6.0 nm) and a TaBO film (film thickness: 4.0 nm) in this order using a DC magnetron sputtering device.

[0145] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 39.6 nm), a TaBO film (film thickness: 11.0 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a CrN film (film thickness: 19.5 nm) and a TaBO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n = 0.929, k = 0.039 TaBO film: n = 0.952, k = 0.029 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0146] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 7 was produced.

[0147] Next, using this reflective mask blank 10A, a reflective mask 20 was fabricated by the same manufacturing process as in Example 1. However, in this Example 7, in the patterning process of the light-shielding film 6A, SiO ２ The light-shielding film 6A was patterned by successively etching the TaBO film and the CrN film with a chlorine-based gas containing oxygen. In the patterning process of the first etching mask film 5, the TaBO film was successively patterned with a fluorine-based gas, and the CrON film was successively patterned with a chlorine-based gas containing oxygen. In the patterning process of the absorber film 4, the TaN film was patterned with a chlorine-based gas.

[0148] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 7 was 0.017%, and the reflectance of DUV light was 1.11%. According to Example 7, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0149] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0150] Example 8 SiO prepared in the same manner as in Example 1 ２ -TiO ２ On a glass substrate 1 of the system, a multilayer reflective film 2, a protective film 3, and an absorber film 4 were formed in this order in the same manner as in Example 1.

[0151] Subsequently, a first etching mask film 5 made of a TaBO film (film thickness: 9.0 nm) was formed on the absorber film 4 using a DC magnetron sputtering device.

[0152] Next, a DC magnetron sputtering device was used to deposit a CrOCN film (film thickness: 6.3 nm) and a SiO ２The light-shielding film 6A was formed by laminating a CrOCN film (film thickness: 22.0 nm) and a SiO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrOCN film: n=0.951, k=0.023 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indexes n of the films for light with a wavelength of 230 nm were 2.220 and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 1.098 and 0.001, respectively.

[0153] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 8 was produced.

[0154] Next, this reflective mask blank 10A was used to fabricate a reflective mask 20 by the same manufacturing process as in Example 1. However, in this Example 8, in the patterning process of the light-shielding film 6A, SiO ２ The CrOCN film was then etched in succession with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film 6A.

[0155] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 8 was 0.013%, and the reflectance of DUV light was 0.46%. According to Example 8, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0156] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0157] Example 9 SiO prepared in the same manner as in Example 1 ２ -TiO ２ On a glass substrate 1 of the system, a multilayer reflective film 2, a protective film 3, and an absorber film 4 were formed in this order in the same manner as in Example 1.

[0158] Subsequently, a first etching mask film 5 made of a TaBO film (film thickness: 9.0 nm) was formed on the absorber film 4 using a DC magnetron sputtering device.

[0159] Next, a DC magnetron sputtering device was used to deposit a RuCrN film (film thickness: 105.5 nm), a TaBO film (film thickness: 12.0 nm), and a SiO ２ The light-shielding film 6A was formed by laminating a RuCrN film (film thickness: 25.5 nm) and a TaBO film in this order. The refractive index n and extinction coefficient k of each film for EUV light were as follows: RuCrN film: n = 0.900, k = 0.021 TaBO film: n = 0.952, k = 0.029 SiO ２ film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers of the light-shielding film 6A was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. ２ The refractive indices n of the films for light with a wavelength of 230 nm were 1.418, 2.773, and 1.545, respectively. ２ The extinction coefficients k of the films for light with a wavelength of 230 nm were 2.895, 0.791, and 0.001, respectively.

[0160] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6A in the same manner as in Example 1. In this manner, a reflective mask blank 10A of Example 9 was produced.

[0161] Next, using this reflective mask blank 10A, a reflective mask 20 was fabricated by the same manufacturing process as in Example 1. However, in this Example 9, in the patterning process of the light-shielding film 6A, SiO ２ The light-shielding film 6A was patterned by successively etching the TaBO film and the RuCrN film with a chlorine-based gas containing oxygen.

[0162] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region of the reflective mask 20 obtained in Example 9 was 0.029%, and the reflectance of DUV light was 1.64%. According to this Example 9, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0163] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0164] Example 10: SiO prepared in the same manner as in Example 1 ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0165] Next, a magnetron sputtering device is used to deposit a TaBN film on the first etching mask film 5. ２ The light-shielding film 6B was formed in such a way that the composition of the film changed continuously. As a result, the light-shielding film 6B was obtained in which the refractive index n and the extinction coefficient k for EUV light and light with a wavelength of 230 nm both changed continuously in the film thickness direction of the light-shielding film 6B. The light-shielding film 6B of this Example 10 was formed by depositing a TaB target and SiO ２The targets were set, and the sputtering conditions, such as the power applied to each sputtering target and the flow rate of the sputtering gas (Ar, nitrogen), were changed over time to form the films. The total film thickness of the light-shielding film 6B was 154.0 nm. The refractive index n and extinction coefficient k of each film with respect to EUV light were as follows: TaBN film (lower region): n = 0.951, k = 0.033 SiO ２ Film (upper region): n = 0.973, k = 0.013. Therefore, the light-shielding film 6B had a refractive index for EUV light that decreased toward the substrate in the film thickness direction. Furthermore, in the light-shielding film 6B, the absolute difference between the refractive index of the lower region and the refractive index of the upper region for EUV light was 0.08 or less, and the absolute difference between the extinction coefficient of the lower region and the extinction coefficient of the upper region for EUV light was both 0.03 or less. Furthermore, the refractive index n for light with a wavelength of 230 nm was 2.234 in the lower region and 1.545 in the upper region. The extinction coefficient k for light with a wavelength of 230 nm was 2.283 in the lower region and 0.001 in the upper region.

[0166] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6B in the same manner as in Example 1. In this manner, a reflective mask blank 10B of Example 10 was produced.

[0167] Next, this reflective mask blank 10B was used to fabricate a reflective mask 20 by the same manufacturing process as in the above-described Example 1. However, in this Example 10, the light-shielding film 6B was etched with a fluorine-based gas, and then further etched with a chlorine-based gas, thereby forming a pattern in the light-shielding film 6B.

[0168] The reflectances of EUV light and DUV light in the light-shielding region B formed by the light-shielding pattern in the obtained reflective mask 20 were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B in the reflective mask 20 obtained in Example 10 was 0.026%, and the reflectance of DUV light was 2.45%. According to this Example 10, it was possible to sufficiently reduce the reflection of both EUV light and DUV light (out-of-band light) in the light-shielding region B of the reflective mask 20.

[0169] The reflective mask 20 thus obtained was set in an exposure device, and a pattern was transferred onto a semiconductor substrate on which a resist film had been formed. As a result, the pattern was transferred satisfactorily without any defects.

[0170] Comparative Example 1 SiO prepared in the same manner as in Example 1 above ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0171] Next, a light-shielding film 6' made of a TaBO film (film thickness: 91.0 nm) was formed on the first etching mask film 5 using a DC magnetron sputtering apparatus. The refractive index n and extinction coefficient k of the TaBO film for EUV light were as follows: TaBO film: n = 0.952, k = 0.029. The TaBO film was a single film with a uniform composition ratio in its thickness direction, except for the interface with another film formed in contact with the TaBO film. The refractive index n and extinction coefficient k for EUV light and light with a wavelength of 230 nm were both constant in its thickness direction, except for the interface. The TaBO film had a refractive index of 2.773 and an extinction coefficient of 0.791 for light with a wavelength of 230 nm.

[0172] Subsequently, a second etching mask film 7 was formed on the light-shielding film 6' in the same manner as in Example 1. In this manner, a reflective mask blank 10' of Comparative Example 1 was produced.

[0173] Next, this reflective mask blank 10′ was used to fabricate a reflective mask 20′ by the same manufacturing process as in Example 1. However, in this comparative example 1, in the patterning process of the light-shielding film 6′, the TaBO film was patterned using a fluorine-based gas.

[0174] The reflectances of EUV light and DUV light in the light-shielding region B' formed by the light-shielding pattern in the obtained reflective mask 20' were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B' of the reflective mask 20' obtained in Comparative Example 1 was 0.071%, and the reflectance of DUV light was 24.37%. In Comparative Example 1, it was not possible to sufficiently reduce the reflection of EUV light and DUV light (out-of-band light) in the light-shielding region B' of the reflective mask 20'. From these results, it is considered that if the light-shielding film 6' is a single film whose composition is uniform in the thickness direction except for the interfaces with other media above and below the light-shielding film 6', it is difficult for this light-shielding film 6' to sufficiently reduce the reflection of EUV light and DUV light (out-of-band light), regardless of the material of the light-shielding film 6'. Furthermore, since the light-shielding film 6' in Comparative Example 1 was a single film whose composition was uniform in the thickness direction except for the interfaces and whose thickness was large, the cross-sectional shape of the light-shielding pattern was also not satisfactory.

[0175] Comparative Example 2: SiO prepared in the same manner as in Example 1. ２ -TiO ２ In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, an absorber film 4, and a first etching mask film 5 were formed in this order on a glass substrate 1 of the system.

[0176] Next, a DC magnetron sputtering device was used to deposit a CrN film (film thickness: 38.6 nm), a RuN film (film thickness: 5.0 nm), and a SiO ２ The refractive index n and extinction coefficient k of each film for EUV light were as follows: CrN film: n=0.929, k=0.039 RuN film: n=0.888, k=0.017 SiO ２ Film: n=0.973, k=0.013. Therefore, the absolute difference in refractive index for EUV light between adjacent layers of the light-shielding film 6" exceeded 0.06. The light-shielding film 6" did not have a refractive index that decreases toward the substrate. In addition, the CrN film, RuN film, and SiO ２The refractive indices n of the films for light with a wavelength of 230 nm were 1.339, 1.168, and 1.545, respectively. ２ The extinction coefficients k of the RuN film of the light-shielding film 6" for light with a wavelength of 230 nm were 2.393, 2.986, and 0.001, respectively. ２ The difference from the extinction coefficient of the film for light with a wavelength of 230 nm was more than 2.0.

[0177] Subsequently, the second etching mask film 7 similar to that of Example 1 was formed on the light-shielding film 6 ″. In this manner, a reflective mask blank 10 ″ of Comparative Example 2 was produced.

[0178] Next, using this reflective mask blank 10", a reflective mask 20" was produced by the same manufacturing process as in Example 1. However, in this comparative example 2, in the patterning process of the light-shielding film 6", SiO ２ The RuN film and the CrN film were successively patterned using a chlorine-based gas containing oxygen.

[0179] The reflectances of EUV light and DUV light in the light-shielding region B" formed by the light-shielding pattern in the obtained reflective mask 20" were measured in the same manner as in Example 1. As a result, the reflectance of EUV light in the light-shielding region B" of the reflective mask 20" obtained in Comparative Example 2 was 0.159%, and the reflectance of DUV light was 31.96%. In Comparative Example 2, it was not possible to sufficiently reduce the reflection of EUV light and DUV light (out-of-band light) in the light-shielding region B" of the reflective mask 20".

[0180] REFERENCE SIGNS LIST 1 substrate 2 multilayer reflective film 3 protective film 4 absorber film 5 first etching mask film 6A, 6B, 6 light-shielding film 7 second etching mask film 8 back surface conductive film 9 resist film 10A, 10B reflective mask blank 20 reflective mask A transfer pattern area B light-shielding area

Claims

1. A reflective mask blank comprising: a substrate; a multilayer reflective film provided on the substrate; an absorber film provided on the multilayer reflective film; and a light-shielding film provided on the absorber film, wherein the light-shielding film includes a plurality of layers, and an absolute difference in refractive index for EUV light between adjacent layers among the plurality of layers in the light-shielding film is 0.06 or less, and an absolute difference in extinction coefficient for EUV light between the adjacent layers is 0.03 or less.

2. A reflective mask blank comprising: a substrate; a multilayer reflective film provided on the substrate; an absorber film provided on the multilayer reflective film; and a light-shielding film provided on the absorber film, wherein the light-shielding film has a refractive index for EUV light that decreases in the thickness direction toward the substrate.

3. A reflective mask blank as described in claim 1 or 2, characterized in that the absolute difference between the refractive index for the EUV light of the outermost surface of the light-shielding film which is farthest from the substrate or the uppermost layer of the light-shielding film which is farthest from the substrate and the refractive index for the EUV light in a vacuum is 0.06 or less.

4. A reflective mask blank as described in claim 1 or 2, characterized in that the absolute difference between the extinction coefficient for the EUV light of the outermost surface of the light-shielding film which is farthest from the substrate or the uppermost layer of the light-shielding film which is farthest from the substrate and the extinction coefficient for the EUV light in a vacuum is 0.03 or less.

5. The reflective mask blank according to claim 1 or 2, characterized in that the light-shielding film contains at least one of chromium, tantalum and silicon.

6. A reflective mask blank according to claim 1 or 2, characterized in that the light-shielding film has an extinction coefficient for the EUV light that increases in the thickness direction toward the substrate.

7. A reflective mask blank according to claim 1 or 2, characterized in that the light-shielding film is a compositionally graded film made of a plurality of elements, the composition ratio of the plurality of elements changing continuously or stepwise in the film thickness direction.

8. A reflective mask blank as described in claim 1 or 2, characterized in that the multilayer reflective film includes a plurality of pairs of low refractive index layers and high refractive index layers, and the multilayer reflective film has an interface between the low refractive index layers and the high refractive index layers that are in contact with each other in some regions, and does not have the interface in other regions.

9. A reflective mask blank according to claim 1 or 2, further comprising a first etching mask film between said absorber film and said light-shielding film.

10. The reflective mask blank according to claim 1 or 2, further comprising a second etching mask film on said light-shielding film.

11. A reflective mask manufactured from the reflective mask blank according to claim 1 or 2, comprising: a transfer pattern formed in the absorber film; and a light-shielding pattern formed in the light-shielding film, the light-shielding pattern being provided on the outer periphery of an area including the transfer pattern so that the transfer pattern is exposed.

12. A method for manufacturing a semiconductor device, comprising the steps of: using a reflective mask as defined in claim 11; and transferring the transfer pattern of the reflective mask onto a transfer target on a semiconductor substrate.

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