Reflection type mask blank, reflection type mask, and method for manufacturing semiconductor device

Abstract

To provide a reflection type mask blank for manufacturing a reflection type mask that can reduce reflection light of EUV light and out-of-band light in a light-shielding region of a reflection type mask.SOLUTION: A reflection type mask blank has: a substrate; a multilayer reflection film provided on the substrate; an absorber film provided on the multilayer reflection film; and a light-shielding film provided on the absorber film. The light-shielding film includes a plurality of layers, an absolute difference of refractive indices to EUV light between layers contacting with each other out of the plurality of layers is 0.06 or less, and an absolute difference of extinction coefficients to EUV light between the layers contacting with each other is 0.03 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask blank used in the manufacture of a semiconductor device, a reflective mask, and a method for manufacturing a semiconductor device. [Background technology]

[0002] In general, in the manufacturing process of semiconductor devices, fine patterns are formed by using a photolithography method. In addition, in forming these fine patterns, a number of transfer masks, called photomasks, are usually used. These transfer masks are generally formed by providing fine patterns made of metal thin films or the like on a glass substrate, and photolithography is also used in the manufacture of these transfer masks.

[0003] In recent years, in the semiconductor industry, with the increasing integration of semiconductor devices, fine patterns exceeding the transfer limit of conventional photolithography using ultraviolet light are required. As a technique that enables the formation of such fine patterns, there is EUV lithography, which is an exposure technique using extreme ultraviolet (hereinafter referred to as "EUV") light. Here, EUV light refers to light in a wavelength band in the soft X-ray region or the vacuum ultraviolet region, and specifically, light with a wavelength of about 13.5 nm including 13.5 nm is used. In such a reflective mask used as a transfer mask in EUV lithography, a multilayer reflective film that reflects the EUV light, which is the exposure light, is formed on a substrate, and an absorber film that absorbs the EUV light is formed in a pattern on the multilayer reflective film.

[0004] As described above, there is an increasing demand for finer patterns in the lithography process, but new problems are also emerging. The shadowing effect is known as one of the problems with lithography using a reflective mask. Since the EUV light, which is the exposure light, is incident at a certain angle (usually about 6 degrees) with respect to the vertical surface of the reflective mask, a shadow of the absorber film is generated due to the film thickness of the absorber film. Since the exposure light is not reflected in this shadowed area, a dimensional difference occurs in the reflected image of the pattern, and the pattern image becomes distorted.

[0005] The influence of this shadowing effect can be reduced by reducing the thickness of the absorber film, but when the absorber film is made thinner, a new problem of light-shielding performance occurs in the light-shielding region of the reflective mask. The light-shielding region here is a region provided on the periphery of the region including the transfer pattern so that the transfer pattern of the reflective mask is exposed, and is intended to prevent the exposure light from leaking into the region adjacent to the block on the semiconductor substrate to which the pattern is transferred when the pattern is transferred using the reflective mask. In the actual exposure work, multiple chips are attached to one semiconductor substrate. Therefore, if the reflected light from this light-shielding region is large, the problem of reduced yield occurs due to the effect of multiple exposure in the boundary region between adjacent chips. Therefore, it is required that the reflectance of the exposure light in this light-shielding region is sufficiently small. However, as described above, when the absorber film is made thinner to reduce the shadowing effect, the light radiated from the absorber film to the outside of the mask increases. As a result, a problem occurs in which the light-shielding performance in the light-shielding region cannot be sufficiently secured.

[0006] Therefore, a method has been proposed in Patent Document 1 in which a groove region is formed outside a circuit pattern region formed in the light absorber layer of the mask, by carving a groove region from the surface of the light absorber layer to reach the multilayer reflective film. This groove region serves as a light shielding region against EUV light, and even if the light absorber layer is made thin, it is possible to suppress reflection of EUV light in this light shielding region. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-212220 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in many cases, a light source that generates EUV light not only emits light in the EUV region with a wavelength of about 13.5 nm, but also light in the deep ultraviolet region with a wavelength of, for example, 190 nm to 270 nm. In this specification, the deep ultraviolet region with a wavelength of 190 nm to 270 nm is sometimes called DUV. Light in the vicinity of this region is generally called out-of-band light. Since out-of-band light is also incident on the reflective mask along with the EUV light, it is desirable that the light-shielding region of the reflective mask not only has the ability to shield EUV light, but also has a sufficiently small reflectance for out-of-band light. For this reason, light-shielding properties against out-of-band light are also required. However, in the method proposed in the above Patent Document 1, although the light-shielding region of the reflective mask can obtain a certain degree of light-shielding property against EUV light, it is not necessarily sufficient, and the light-shielding property against the above-mentioned out-of-band light may also be insufficient. In addition, in recent years, exposure apparatuses with a larger numerical aperture (NA) of the projection optical system have been considered in order to improve the resolution performance. Considering the use of such exposure apparatuses, it is expected that the reflectance of EUV light and out-of-band light in the light-shielding region can be further reduced.

[0009] The present invention has been made in consideration of such conventional problems, and has as its object, firstly, 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 area of ​​a reflective mask and has good light-shielding performance in the light-shielding area. A second object of the present invention is to provide a method for manufacturing a semiconductor device using this reflective mask. [Means for solving the problem]

[0010] In order to solve the problems of the prior art, the present inventors have focused on the configuration of a light-shielding film that forms a light-shielding region of a reflective mask and continued their intensive research, resulting in the completion of the following invention. (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 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.

[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 for EUV light that decreases in a thickness direction toward the substrate.

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

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

[0014] (Configuration 7) 7. A reflective mask blank according to any one of structures 1 to 6, wherein the light-shielding film is a compositionally gradient film made of a plurality of elements, the composition ratio of the plurality of elements changing continuously or stepwise in the film thickness direction.

[0015] (Configuration 8) The reflective mask blank according to any one of structures 1 to 7, 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.

[0016] (Configuration 9) 9. The reflective mask blank according to any one of structures 1 to 8, further comprising a first etching mask film between the absorber film and the light-shielding film. (Configuration 10) 10. The reflective mask blank according to any one of structures 1 to 9, further comprising a second etching mask film on the light-shielding film.

[0017] (Configuration 11) 11. A reflective mask manufactured from the reflective mask blank according to any one of configurations 1 to 10, 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.

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

[0019] According to the present invention, it is possible to provide a reflective mask blank and a reflective mask for producing a reflective mask that can reduce reflection of EUV light and out-of-band light in the light-shielding area of ​​a reflective mask and has good light-shielding performance in the light-shielding area. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device that can perform highly accurate pattern transfer using this reflective mask. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a reflective mask blank of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another embodiment of the reflective mask blank of the present invention. [Diagram 3] 1 is a schematic cross-sectional view showing one embodiment of a reflective mask of the present invention. [Figure 4] FIG. 2 is a plan view of a reflective mask showing an example of a transfer pattern region and a light-shielding region. [Diagram 5] 1A to 1C are schematic cross-sectional views showing the steps of producing a reflective mask from the reflective mask blank of the present invention. [Figure 6] 6 is a schematic cross-sectional view showing a continuation of the step shown in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail. [Reflective mask blank] First, the reflective mask blank of the present invention will be described. In this specification, the refractive index and extinction coefficient are sometimes described without referring to the wavelength of the reference light or electromagnetic wave, but unless otherwise specified, the refractive index and extinction coefficient are both values ​​relative to EUV light.

[0022] <First embodiment> FIG. 1 is a schematic cross-sectional view showing one embodiment (first embodiment) of the reflective mask blank of the present invention. As shown in FIG. 1, the reflective mask blank 10A of this embodiment includes a substrate 1, a multilayer reflective film 2 provided on 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, and a back conductive film 8 is provided on the back side of the substrate 1. In this embodiment, the light-shielding film 6A includes a plurality of layers, and is formed of a three-layer laminate film of a layer 6a, a layer 6b, and a layer 6c from the side closer to the substrate 1. The light-shielding film 6A may be a laminate film consisting of two layers or four or more layers. The case of a laminate film consisting of three layers will be described below.

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

[0024] In this embodiment, the light-shielding film 6A is characterized in that the absolute difference in refractive index for EUV light between the layers in contact with each other among the plurality of layers is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the layers in contact with each other is 0.03 or less. The absolute difference means the absolute value of the difference between two values. When the light-shielding film 6A is formed of a three-layer laminate film of the layer 6a, the layer 6b, and the layer 6c from the side closer to the substrate 1, the absolute difference in refractive index for EUV light between the layer 6a and the layer 6b is 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the layer 6a and the layer 6b is 0.03 or less. In addition, the absolute difference in refractive index for EUV light between the layer 6b and the layer 6c is also 0.06 or less, and the absolute difference in extinction coefficient for EUV light between the layer 6b and the layer 6c is 0.03 or less.

[0025] That is, when the light-shielding film 6A is made up 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. Also, the absolute difference in extinction coefficient for EUV light between the Nth layer and the (N+1)th layer is 0.03 or less. Here, M is an integer of 2 or more, and N is an integer of 1 or more and less than M.

[0026] Here, EUV light refers to light (electromagnetic waves) having a wavelength of around 13.5 nm, including 13.5 nm, and in the present invention, specifically refers to light in the wavelength region of 13.395 nm to 13.665 nm. In this specification, light includes not only visible light but also electromagnetic waves.

[0027] In this embodiment, as described above, the light-shielding film 6A includes a plurality of layers 6a, 6b, and 6c, and the absolute difference in the refractive index for EUV light between the layers in contact with each other among the plurality of layers is 0.06 or less, and the absolute difference in the extinction coefficient for EUV light between the layers in contact with each other among the plurality of layers is 0.03 or less. The smaller the absolute difference in the refractive index and the absolute difference in the extinction coefficient between the layers in contact with each other among the plurality of layers, the lower the reflectance of EUV light at the interface between the layers. The lowering of the reflectance of EUV light at each interface can suppress the EUV light reflectance of the entire light-shielding film. In addition, by satisfying the characteristics of the configuration of the light-shielding film of the present invention, the reflectance of the light-shielding film can be suppressed not only for EUV light but also for the above-mentioned out-of-band light, for example, light in the deep ultraviolet region (DUV) having a wavelength of 190 nm to 270 nm (hereinafter also referred to as "DUV light").

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

[0029] When the light-shielding film 6A is formed of a three-layer laminate film of layers 6a, 6b, and 6c from the side closer to the substrate 1, it is preferable that the absolute difference in refractive index between layers 6a and 6b for light with a wavelength of 230 nm is 2.0 or less, and the absolute difference in extinction coefficient between layers 6a and 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 layers 6b and 6c for light with a wavelength of 230 nm is 2.0 or less, and the absolute difference in extinction coefficient between layers 6b and 6c for light with a wavelength of 230 nm is 2.0 or less.

[0030] That is, when the light-shielding film 6A is composed 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 makes it possible to further suppress the reflectance of the light-shielding film even for DUV light.

[0031] In this embodiment, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers 6a, 6b, and 6c of the light-shielding film 6A is preferably greater than 0 (zero). Similarly, the absolute difference in extinction coefficient for EUV light between adjacent layers is preferably 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 this 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 in the light-shielding film (light-shielding region).

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

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

[0035] The light-shielding film 6A preferably has a minimum reflectance value for light with a wavelength of about 13.53 nm. The light-shielding film 6A preferably has a minimum reflectance value when the light wavelength is in the 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 in the wavelength range of 13 nm or more and 14 nm or less, more preferably in the wavelength range of 13.40 nm or more and 13.67 nm or less. The light-shielding films of each example described below satisfy all of the above conditions. The light-shielding film 6A has such a configuration, so that the EUV light reflectance can be effectively suppressed. The same applies to the light-shielding film 6B in the second embodiment described below. In addition, 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, but the reflectance spectrum of the light-shielding film 6A can have a maximum value, for example, in a wavelength range of 190 nm to 270 nm. For example, in a wavelength range of 190 nm to 270 nm, if the maximum value of the reflectance of the light-shielding film 6A is 3.0% or less and the slope of the tangent of the reflectance spectrum of the light-shielding film 6A has a positive value, the reflectance of light in a wavelength range of less than 190 nm, which may cause unnecessary exposure of the resist film, can also be reduced. In addition, if the light-shielding film 6A has the above-mentioned configuration, even if the wavelength at which the reflectance of the light-shielding film 6A is maximum in the wavelength range of 190 nm to 270 nm is shifted slightly due to a slight change in the thickness of the light-shielding film 6A, the reflectance of not only light in the wavelength range of 190 nm to 270 nm but also light in the wavelength range of less than 190 nm can be reduced. The same applies to a light-shielding film 6B in a second embodiment described later. In this embodiment, the light-shielding film 6A is described as being formed of a three-layer laminate film consisting of layers 6a, 6b, and 6c. However, in the present invention, 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, and may be any material that satisfies the characteristics of the light-shielding film of the present invention. For example, materials containing one or more 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. are exemplified. In particular, materials containing one or more selected from Cr, Ta, and Si are exemplified. In addition to the above, at least one or more selected from O, N, C, B, H, and rare gases (He, Ne, Ar, Kr, Xe, etc.) may be further included. When a rare gas is included, the content thereof is preferably 5 atomic % or less, more preferably 3 atomic % or less.

[0037] In addition, the various properties such as the refractive index and extinction coefficient of the thin film including the light-shielding film 6A are not determined only by the composition of the thin film. The film density and crystal state of the thin film are also factors that affect the various properties of the thin film. For this reason, the conditions for forming the thin film by sputtering are adjusted so that the thin film has the specified properties. For example, a wide range of conditions such as the pressure in the film formation chamber when forming the thin film, the power applied to the sputtering target, the positional relationship such as the distance between the target and the substrate to be filmed, and the target formation conditions are adjusted so that the thin film has the specified properties. In addition, these film formation conditions are specific to the film formation device and are appropriately adjusted so that the thin film has the specified properties.

[0038] In the present embodiment, when the light-shielding film 6A includes a plurality of layers 6a, 6b, and 6c, the material of each of the layers may be selected from the above materials. In this case, the light-shielding film may be composed of a plurality of layers having different constituent elements, or may be composed of a plurality of 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 rate of the first element is the highest among the contents of the first element, the second element, ..., the nth element contained in the light-shielding film 6A can be regarded as the first layer, the region where the content rate of the second element is the highest, and the region where the content rate of the nth element is the highest can be regarded as the nth layer. In this case, the light-shielding film 6A is a laminated film consisting of the first layer, the second layer, ..., the nth layer. Here, n is a natural number of 2 or more. The refractive index and extinction coefficient of the first layer respectively mean the average refractive index and the average extinction coefficient in the film thickness direction of the first layer. The same applies to the second, ..., nth layers. The stacking order of the first, second, ..., nth layers 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 (light-shielding region). It is preferable that both absolute differences 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 the light-shielding film 6A (first etching mask film 5 or absorber film 4) does not necessarily have to be small, but is preferably, for example, 2.0 or less. 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 (light-shielding region).

[0041] Of the multiple layers of the light-shielding film 6A, the refractive index and extinction coefficient of the top layer (above layer 6c) or the top surface farthest (farthest) from the substrate 1 for EUV light are preferably close to the refractive index and extinction coefficient for EUV light in vacuum. Specifically, of the multiple layers of the light-shielding film 6A, the absolute difference between the refractive index of the top layer (above layer 6c) or the top surface farthest from the substrate 1 for EUV light and the refractive index for EUV light in vacuum is preferably 0.06 or less. In addition, the absolute difference between the extinction coefficient of the top layer (above layer 6c) or the top surface farthest from the substrate 1 for EUV light and the extinction coefficient for EUV light in vacuum is preferably 0.03 or less. This makes it possible to more effectively reduce the reflection of EUV light and DUV light in the light-shielding film (light-shielding region). In this case, the material of the top layer of the light-shielding film is not particularly limited, but for example, SiO2, TaBO, CrOCN, TaON, TaO, CrO, and CrON are preferably mentioned.

[0042] Furthermore, although not shown, in the case where 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. For this reason, by using the reflective mask blank 10A of this embodiment, the absorber film pattern can be formed with higher accuracy. In particular, when the light-shielding film 6A is a laminated film in which layers having high etching selectivity are laminated to each other, the cross-sectional shape of the light-shielding film 6A after etching becomes better, and the accuracy of the absorber film pattern can be further improved.

[0043] In the case of the substrate 1 in the reflective mask blank 10A of the present embodiment, in order to prevent distortion of the pattern due to heat during exposure, particularly in the case of EUV exposure, the substrate 1 has a thickness of 0±1.0×10 -7 / °C, more preferably within 0±0.3×10 -7 Materials having a low thermal expansion coefficient within the range of 100 / ° C. / ° C. are preferably used. Examples of materials having a low thermal expansion coefficient within this range include SiO2-TiO2 glass and multi-component glass ceramics.

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

[0045] As described above, the substrate 1 is preferably made of a material having a low thermal expansion coefficient, such as SiO2-TiO2-based glass. It is difficult to achieve high smoothness, such as a root mean square roughness (Rq) of 0.1 nm or less, as the surface roughness of such a material by precision polishing. Therefore, in order to reduce the surface roughness of the substrate 1 or to reduce defects on the surface of the substrate 1, a base layer (not shown) may be formed on the surface of the substrate 1. As the material for such a base layer, it is not necessary to have translucency to the exposure light, and a material that can provide high smoothness and good defect quality when the surface of the base layer is precision polished is preferably selected. For example, Si or a silicon compound containing Si (e.g., SiO2, SiON, etc.) is preferably used as the material for the base layer because it provides high smoothness and good defect quality when precision polished. The material for the base layer is particularly preferably Si.

[0046] The surface of the underlayer is preferably precision-polished to have a smoothness required for a reflective mask blank substrate. The surface of the underlayer is desirably precision-polished to have a root-mean-square roughness (Rq) of 0.15 nm or less, more preferably 0.1 nm or less. In addition, 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 to have a relationship with the maximum height (Rmax) of preferably Rmax / Rq of 2 to 10, more preferably 2 to 8. The thickness of the underlayer is preferably in the range of, for example, 10 nm to 300 nm.

[0047] The multilayer reflective film 2 provided on the substrate 1 (on the underlayer if the underlayer is formed) includes a plurality of pairs of low refractive index layers and high refractive index layers, and specifically is a multilayer film in which low refractive index layers and high refractive index layers are alternately stacked. Generally, a multilayer film is used in which thin films of heavy elements or their compounds and thin films of light elements or their compounds are alternately stacked for about 30 to 60 periods. For example, as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 periods is preferably used. Other multilayer reflective films used in the EUV light region include Ru / Si periodic multilayer film, Mo / Be periodic multilayer film, Mo compound / Si compound periodic multilayer film, Si / Nb periodic multilayer film, Si / Mo / Ru periodic multilayer film, Si / Mo / Ru / Mo periodic multilayer film, and Si / Ru / Mo / Ru periodic multilayer film. The material may be appropriately selected according to the exposure wavelength. In addition, 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 present invention, it is preferable to modify the multilayer reflective film 2 by laser irradiation or ion implantation. In the laser-irradiated region of the multilayer reflective film 2, for example, diffusion occurs between the low refractive index layer and the high refractive index layer that are in contact with each other. Therefore, it is presumed that there is no interface between the low refractive index layer and the high refractive index layer. This makes it possible to further reduce the reflection of EUV light and DUV light in the light-shielding film (light-shielding region). Therefore, the film thickness of the light-shielding film can be made thinner, and the accuracy of the absorber film pattern can be further improved. Note that even if the other functional layer is formed between the low refractive index layer and the high refractive index layer, diffusion can be caused by laser irradiation or ion implantation.

[0049] In the multilayer reflective film 2, the state where diffusion occurs or the state where there is no interface specifically means that the film thickness of the diffusion region described later is 20 nm or more. When the multilayer reflective film 2 is analyzed by energy dispersive X-ray spectroscopy (EDX), in the diffusion region, the difference D1 obtained by subtracting the minimum value Y1 (atomic %) of the content of the first element having the highest content in the multilayer reflective film 2 from the maximum value X1 (atomic %) of the content of the first element is 30 or less, and the difference D2 obtained by subtracting the minimum value Y2 (atomic %) of the content of the second element having the highest content in the multilayer reflective film 2 from the maximum value X2 (atomic %) of the content of the second element is 30 or less. That is, (X1-Y1)≦30 and (X2-Y2)≦30. Moreover, both X1-Y1 and X2-Y2 are 0 or more. The film thickness of the diffusion region is more preferably 30 nm or more. In this specification, the depth resolution of the EDX is 1.56 nm.

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

[0051] Preferred examples of light sources for laser irradiation include F2 laser (wavelength: approximately 157 nm), ArF excimer laser (wavelength: approximately 193 nm), KrF excimer laser (wavelength: approximately 248 nm), fourth harmonic YAG laser (wavelength: approximately 266 nm), XeCl excimer laser (wavelength: approximately 308 nm), Ar laser (wavelength: approximately 488 nm), YAG laser (wavelength: 1064 nm), and CO2 laser (wavelength: 10.6 μm).

[0052] By modifying the above-mentioned multilayer reflective film 2, for example, by laser irradiation, the multilayer reflective film 2 has no interface between the low refractive index layer and the high refractive index layer that are in contact with each other in some regions (laser irradiated regions), but has the interface in other regions (non-laser irradiated regions).

[0053] Usually, in order to protect the multilayer reflective film 2 during patterning or pattern correction of the absorber film 4, it is preferable to provide a protective film 3 (sometimes called a capping layer) on the multilayer reflective film 2. Such a protective film 3 is formed of a material containing ruthenium as a main component, for example. Examples of materials containing ruthenium as a main component include simple Ru metal, Ru alloys containing at least one metal selected from titanium (Ti), niobium (Nb), rhodium (Rh), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), chromium (Cr) and rhenium (Re), and materials containing nitrogen therein. The thickness of the protective film 3 is preferably in the range of, for example, about 1 nm to 5 nm.

[0054] The above-described light-shielding film 6A, undercoat layer, multilayer reflective film 2, and protective film 3 may be formed by any method, but ion beam sputtering, magnetron sputtering, or the like is usually preferred. At least one of the sputtering target and sputtering gas used to form each film (layer) contains an element that constitutes each 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 characteristics (e.g., the refractive index and extinction coefficient of the light-shielding film 6A).

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

[0056] In addition to the reflectance difference, the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 may have a desired phase difference between the reflected light from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and the reflected light from the transfer pattern (absorber film pattern) 4a. When the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 has a desired phase difference between the reflected light from the transfer pattern (absorber film pattern) 4a, 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 reflected light from the multilayer reflective film 2 or the protective film 3 formed on the multilayer reflective film 2 and the reflected light from the transfer pattern (absorber film pattern) 4a to improve contrast, the phase difference is preferably set in the range of 170 degrees to 260 degrees, and the EUV light reflectance of the absorber film 4 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, it 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 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. As a material having the above-mentioned functions, at least one metal selected from 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), an alloy containing two or more metals, or a compound thereof can be preferably used. The compound may contain oxygen (O), nitrogen (N), carbon (C), boron (B) and / or hydrogen (H) in said 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. Although there are no particular limitations on the method for forming the absorber film 4, magnetron sputtering, ion beam sputtering, or the like is usually suitable.

[0060] In addition, the absorber film 4 can be configured as a laminated film of a top layer and other layers made of materials with different etching selectivities, with the top layer functioning as a hard mask film (etching mask film) for the other layers.

[0061] The reflective mask blank 10A of this embodiment also has a first etching mask film 5 between the absorber film 4 and the light-shielding film 6A. The first etching mask film 5 has a mask function when the absorber film 4 is patterned, and is made of a material having an etching selectivity different from that of 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, and materials such as metal silicon (metal silicide) and metal silicon compound (metal silicide compound) 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. In addition, 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 to 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] Moreover, the reflective mask blank 10A of this embodiment has a second etching mask film 7 on the light-shielding film 6A. The second etching mask film 7 has a mask function when the light-shielding film 6A is patterned, and is made of a material having an etching selectivity different from that of at least the uppermost layer (the layer 6c) of the light-shielding film 6A. For example, when the uppermost layer (the 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 a material containing tantalum. Examples of the material containing chromium include Cr metal and the above-mentioned chromium compounds. Examples of the material 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, multiple films of the same material may be laminated, or multiple layers of different materials may be laminated. For example, the second etching mask film 7 can include a TaBN layer and a CrN layer formed on the TaBN layer. The laminated film can have a material or composition that changes stepwise and / or continuously in the thickness direction.

[0064] <Second embodiment> FIG. 2 is a schematic cross-sectional view showing another embodiment (second embodiment) of the reflective mask blank of the present invention. As shown in FIG. 2, the reflective mask blank 10B of this embodiment has a substrate 1, a multilayer reflective film 2 provided on 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, and has a back surface conductive film 8 on the back surface side of the substrate 1.

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

[0066] In this embodiment, the light-shielding film 6B has a refractive index for EUV light that decreases toward the substrate 1 in the film thickness direction. By satisfying the configuration features of the light-shielding film of this embodiment, the reflectance of EUV light at the light-shielding film can be suppressed. Also, the reflectance at the light-shielding film can be suppressed not only for EUV light but also for the above-mentioned DUV light.

[0067] In order to satisfy the characteristics of the light-shielding film of this embodiment, the light-shielding film 6B is preferably 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. The material of the light-shielding film 6B may preferably be the same as the material of the light-shielding film 6A in the reflective mask blank 10A of the first embodiment described above. At least one of the sputtering target and the sputtering gas used to form the light-shielding film 6B contains the 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 characteristics (refractive index, extinction coefficient).

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

[0069] As described above, in this embodiment, the light-shielding film 6B is preferably a compositionally graded film, and 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, and preferably 0.97 or less. The lower region refers to a region 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 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 lower region. The refractive index n of the upper region of the light-shielding film far from the substrate 1 is preferably 0.94 or more, and preferably 1.01 or less. The upper region refers to a region from the surface of the light-shielding film 6B farthest from the substrate 1 (the interface with the second etching mask film 7) to 5 nm to 10 nm in the film thickness direction. 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 with respect to EUV light is as follows. The extinction coefficient k of the light-shielding film in the lower region closer to the substrate 1 is preferably 0.01 or more, and more preferably 0.06 or less. Moreover, the extinction coefficient k of the light-shielding film in the upper region far from the substrate 1 is preferably 0.0 or more, and more 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, it is preferably 0.06 or less. Similarly, it is preferable that the absolute difference in extinction coefficient for EUV light is small, for example, it is preferably 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 (light-shielding region).

[0072] The absolute difference in refractive index for light with a wavelength of 230 nm between the lower region and the film (first etching mask film 5 or absorber film 4) below the light-shielding film 6B does not necessarily have to be small, but is preferably, for example, 2.0 or less. 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 (light-shielding region).

[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. 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. Also, 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 in the light-shielding film (light-shielding region).

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

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

[0076] In addition, 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. In addition, 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 in the light-shielding film (light-shielding region).

[0077] Except for the light-shielding film 6B in the reflective mask blank 10B of this embodiment, 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 are all similar to those films in the reflective mask blank 10A of the above-mentioned first embodiment. In addition, the modification of the multilayer reflective film 2 by laser irradiation or ion implantation is also similar to the first embodiment.

[0078] The reflective mask blank of the present invention has been described above with reference to the first and second embodiments, but according to the reflective mask blank of the present invention, for example, the reflected light 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 can be reduced, and good light-shielding performance can be achieved in the light-shielding region. Specifically, according to the reflective mask blank of the present invention, the reflectance of EUV light in the light-shielding region of a reflective mask can be suppressed to, for example, 0.1% or less, and the reflectance of DUV light can be suppressed to, for example, 3.0% or less.

[0079] [Reflective mask] Next, the reflective mask of the present invention will be described. Fig. 3 is a schematic cross-sectional view showing one embodiment of the reflective mask of the present invention, and Fig. 4 is a plan view of the reflective mask showing an example of a transfer pattern region and a light-shielding region. As shown in FIG. 3, a reflective mask 20 of one embodiment of the present invention is manufactured, for example, by using the above-mentioned reflective mask blank, 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), and the light-shielding pattern is provided on the outer periphery of a transfer pattern area A including the transfer pattern 4a so that the transfer pattern 4a is exposed, thereby forming a light-shielding area B.

[0080] For example, if the size of the substrate is approximately 152.0 mm x approximately 152.0 mm (6 inch square), the transfer pattern area can be, for example, an area measuring 132 mm x 132 mm, and the shading area B can be a strip-shaped area with a width of 2.0 mm or more and 4.0 mm or less.

[0081] According to the reflective mask of the present invention, it is possible to reduce the reflected light of both EUV light and out-of-band light in the light-shielding region of the reflective mask, thereby providing a reflective mask with good light-shielding performance in the light-shielding region.

[0082] The present invention also provides reflective masks having the following configurations A and B. (Configuration A) A reflective mask, 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; A light-shielding pattern formed on the light-shielding film, The light-shielding film includes a plurality of layers, in the light-shielding film, an absolute difference in refractive index for EUV light between adjacent layers among 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, A reflective mask, characterized in that the light-shielding pattern is provided on the outer periphery of an area including the transfer pattern so that the transfer pattern is exposed.

[0083] (Configuration B) A reflective mask, 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; A light-shielding pattern formed on the light-shielding film, the light-shielding film has a refractive index with respect to EUV light that decreases toward the substrate in a thickness direction; A reflective mask, characterized in that the light-shielding pattern is provided on the outer periphery of an area including the transfer pattern so that the transfer pattern is exposed.

[0084] Next, a method for producing a reflective mask according to the present invention will be described. FIG. 5 is a schematic cross-sectional view showing a process for producing a reflective mask from a reflective mask blank of the present invention, and FIG. 6 is a schematic cross-sectional view showing a continuation of the process shown in FIG.

[0085] First, 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. 5(a)). The resist film is then lithographed and developed using an electron beam lithography device to form a predetermined resist pattern 9a in the resist film (see FIG. 5(b)).

[0086] 5 and 6, 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 above-mentioned first embodiment or the light-shielding film 6B in the reflective mask blank 10B of the above-mentioned second embodiment. Also, in FIGS. 5 and 6, the back surface conductive film 8 is omitted from illustration.

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

[0088] Next, the light-shielding film 6 is patterned by dry etching using the patterned second etching mask film 7 as a mask (see FIG. 5(d)). 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 patterning step of the light-shielding film.

[0089] Next, a resist film is formed in the same manner as above on the reflective mask blank on which the light-shielding pattern is formed, and this resist film is patterned and developed to form a predetermined resist pattern 9b (see FIG. 6(e)).

[0090] Thereafter, the first etching mask film 5 is patterned by dry etching using the resist pattern 9b as a mask (see FIG. 6(f)).

[0091] Next, 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. 6(g)). As a result, a predetermined transfer pattern 4a (see FIG. 3) is formed 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, the unnecessary first etching mask film 5 and second etching mask film 7 are appropriately removed, and the reflective mask 20 is completed (see FIG. 6(h)).

[0092] In FIG. 5 and FIG. 6, 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 steps 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 an 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 a 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 steps. As a result of the above, a reflective mask 20 can be obtained.

[0093] [Method of manufacturing semiconductor device] The present invention also provides a method for manufacturing a semiconductor device using a reflective mask. In other words, by using the above-mentioned reflective mask of the present invention and exposing and transferring the transfer pattern of the reflective mask to a transfer target on a semiconductor substrate, it is possible to perform high-precision pattern transfer and manufacture high-quality semiconductor devices with few defects. EXAMPLES

[0094] Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples. Example 1 A SiO2-TiO2-based glass substrate (a 6-inch square substrate with a size of approximately 152.0 mm x 152.0 mm and a thickness of approximately 6.35 mm) was prepared by polishing in stages with cerium oxide abrasive grains and colloidal silica abrasive grains using a double-sided polishing machine and then treating the substrate surface with low-concentration hydrosilicofluoric acid. The surface roughness of the obtained glass substrate (Substrate 1) was 0.25 nm in terms of root-mean-square roughness (Rq). The surface roughness was measured with an atomic force microscope (AFM) and the measurement area was 1 μm x 1 μm.

[0095] Next, using an ion beam sputtering device, 40 periods of Si films (thickness: 4.0 nm) and Mo films (thickness: 3.1 nm) were stacked on the main surface of the glass substrate, and finally a Si film (thickness: 3.3 nm) was formed, and a protective film made of Ru (thickness: 3.5 nm) was further formed on top of that to obtain a substrate with a multilayer reflective film.

[0096] Next, using a DC magnetron sputtering device, an absorber film was formed by laminating 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) in this order on the protective film of the multilayer reflective film-coated substrate obtained above. In addition, a TaB conductive film (film thickness: 70 nm) was formed on the back surface of the multilayer reflective film-coated substrate.

[0097] Subsequently, a first etching mask film (film thickness: 16.0 nm) made of SiO2 film was formed on the absorber film using a DC magnetron sputtering device.

[0098] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 60.4 nm), a RuCrO film (film thickness: 11.5 nm), and a SiO2 film (film thickness: 24.1 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 RuCrO film: n=0.921, k=0.027 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrN film, RuCrO film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 2.711, and 1.545, respectively. The extinction coefficients k of the CrN film, RuCrO film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 1.286, and 0.001, respectively.

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

[0100] Next, this reflective mask blank was used to fabricate a reflective mask according to the above-mentioned manufacturing process (see FIGS. 5 and 6). First, a resist for electron beam lithography was applied onto the above-mentioned reflective mask blank and baked to form a resist film (see FIG. 5(a)). The resist film was then patterned and developed using an electron beam lithography device to form a predetermined resist pattern on the resist film (see FIG. 5(b)).

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

[0102] Next, using the patterned second etching mask film as a mask, the SiO2 film was dry-etched with a fluorine-based gas, and the RuCrO film and the CrN film were dry-etched with a chlorine-based gas containing oxygen, respectively, to pattern the light-shielding film (see FIG. 5(d)). The light-shielding pattern thus formed in the light-shielding film was to form the light-shielding region in the reflective mask that was finally produced. The remaining resist pattern was peeled off and removed before the light-shielding film patterning step.

[0103] Next, a resist film was formed in the same manner as above on the reflective mask blank on which the light-shielding pattern was formed, and this resist film was patterned and developed to form a predetermined resist pattern (see FIG. 6(e)).

[0104] Thereafter, the first etching mask film was patterned by dry etching with a fluorine-based gas using the resist pattern as a mask (see FIG. 6(f)).

[0105] Next, the remaining resist pattern was peeled off, and the absorber film was patterned by dry etching using the patterned first etching mask film as a mask (see FIG. 6(g)). Specifically, the RuN film was etched off successively with a chlorine-based gas containing oxygen, the TaBO film was etched off with a fluorine-based gas (CF4 gas), and the TaBN film was etched off with a chlorine-based gas (Cl2 gas). This formed a predetermined transfer pattern in the absorber film. Finally, the unnecessary first etching mask film and second etching mask film were removed to produce a reflective mask (see FIG. 6(h)).

[0106] The reflectance of the resulting reflective mask to EUV light and DUV light in the light-shielding region formed by the light-shielding pattern was measured. The reflectance for EUV light was taken as the average value of the reflectance for light with wavelengths of 13.395 nm to 13.665 nm, and the reflectance for 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 was 0.010%, and the reflectance of DUV light was 1.30% in the light-shielding region of the reflective mask obtained in Example 1. According to this example, it was possible to sufficiently reduce the reflected light of both EUV light and DUV light (out-of-band light) in the light-shielding region of the reflective mask.

[0108] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0109] Example 2 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0110] Next, a light-shielding film was formed on the first etching mask film by laminating a RuCrO film (film thickness: 72.8 nm), a CrO film (film thickness: 13.8 nm), and a SiO2 film (film thickness: 24.6 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. RuCrO film: n=0.921, k=0.027 CrO film: n=0.941, k=0.032 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the RuCrO, CrO film, and SiO2 film for light with a wavelength of 230 nm were 2.711, 2.369, and 1.545, respectively. The extinction coefficients k of the RuCrO, CrO film, and SiO2 film for light with a wavelength of 230 nm were 1.286, 0.849, and 0.001, respectively.

[0111] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 2 was produced.

[0112] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film was successively etched with a fluorine-based gas, and the CrO film and the RuCrO film were successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film.

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

[0114] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0115] Example 3 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0116] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 62.9 nm), a TaBO film (film thickness: 10.8 nm), and a SiO2 film (film thickness: 18.6 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 TaBO film: n = 0.952, k = 0.029 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. The extinction coefficients k of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0117] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 3 was produced.

[0118] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film and the TaBO film were successively etched with a fluorine-based gas, and the CrN film was successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film.

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

[0120] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0121] Example 4 A multilayer reflective film and a protective film were formed in this order on a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1.

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

[0123] Next, a DC magnetron sputtering apparatus was used to form a first etching mask film made of a CrOCN film (film thickness: 6.0 nm) and a TaBO film (film thickness: 4.0 nm) laminated in this order on the absorber film.

[0124] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 30.9 nm), a TaBO film (film thickness: 10.8 nm), and a SiO2 film (film thickness: 18.2 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 TaBO film: n = 0.952, k = 0.029 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. The extinction coefficients k of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0125] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 4 was produced.

[0126] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film and the TaBO film were successively etched with a fluorine-based gas, and the CrN film was successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film. In the patterning step of the first etching mask film, the TaBO film was patterned by a fluorine-based gas, and the CrOCN film was patterned by a chlorine-based gas containing oxygen in succession. In the patterning process of the absorber film, the TaBO film was patterned by a fluorine-based gas, and the TaBN film was patterned by a chlorine-based gas in succession.

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

[0128] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0129] Example 5 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0130] Next, a light-shielding film was formed on the first etching mask film by laminating a TaBO film (film thickness: 70.0 nm), a CrO film (film thickness: 27.6 nm), and a SiO2 film (film thickness: 30.2 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. TaBO film: n = 0.952, k = 0.029 CrO film: n=0.941, k=0.032 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the TaBO film, CrO film, and SiO2 film for light with a wavelength of 230 nm were 2.773, 2.369, and 1.545, respectively. The extinction coefficients k of the TaBO film, CrO film, and SiO2 film for light with a wavelength of 230 nm were 0.791, 0.849, and 0.001, respectively.

[0131] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 5 was produced.

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

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

[0134] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0135] Example 6 A multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order on a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1. In this Example 6, between the formation of the protective film and the formation of the absorber film, a laser was irradiated onto the multilayer reflective film (and the protective film) corresponding to the light-shielding region to form a diffusion region.

[0136] When the multilayer reflective film after the laser irradiation was observed with an electron microscope, the interface between the Si film (high refractive index layer) and the Mo film (low refractive index layer) was confirmed in the area of ​​the multilayer reflective film that was not irradiated with the laser. On the other hand, the interface between the Si film and the Mo film was not confirmed in the area of ​​the multilayer reflective film that was irradiated with the laser. In addition, when the multilayer reflective film was analyzed with an energy dispersive X-ray spectroscopy with a depth resolution of 1.56 nm, diffusion occurred throughout the entire thickness of the multilayer reflective film in the area that was irradiated with the laser. Specifically, in the total thickness of the multilayer reflective film of 287.3 nm, the difference obtained by subtracting the minimum value Y1 (atomic %) of the silicon content, which is the highest content in the multilayer reflective film, from the maximum value X1 (atomic %) of the silicon content, which is the highest content in the multilayer reflective film, was 26. In addition, the difference obtained by subtracting the minimum value Y2 (atomic %) of the molybdenum content, which is the second highest content in the multilayer reflective film, from the maximum value X2 (atomic %) of the molybdenum content, which is the second highest content in the multilayer reflective film, was 17. That is, in the laser irradiated region of the multilayer reflective film of Example 6, the film thickness of the diffusion region was 20 nm or more.

[0137] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 14.4 nm), a TaBO film (film thickness: 9.0 nm), and a SiO2 film (film thickness: 18.6 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 TaBO film: n = 0.952, k = 0.029 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. The extinction coefficients k of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0138] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 6 was produced.

[0139] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film and the TaBO film were successively etched with a fluorine-based gas, and the CrN film was successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film.

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

[0141] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0142] Example 7 A multilayer reflective film and a protective film were formed in this order on a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1.

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

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

[0145] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 39.6 nm), a TaBO film (film thickness: 11.0 nm), and a SiO2 film (film thickness: 19.5 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 TaBO film: n = 0.952, k = 0.029 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 2.773, and 1.545, respectively. The extinction coefficients k of the CrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 0.791, and 0.001, respectively.

[0146] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 7 was produced.

[0147] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film and the TaBO film were successively etched with a fluorine-based gas, and the CrN film was successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film. In the patterning step of the first etching mask film, the TaBO film was patterned by a fluorine-based gas, and the CrON film was patterned by a chlorine-based gas containing oxygen in succession. In the above-mentioned patterning process of the absorber film, the TaN film was patterned using a chlorine-based gas.

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

[0149] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0150] Example 8 A multilayer reflective film, a protective film, and an absorber film were formed in this order on a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1.

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

[0152] Next, a light-shielding film was formed by laminating a CrOCN film (film thickness: 6.3 nm) and a SiO2 film (film thickness: 22.0 nm) in this order on the first etching mask film using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrOCN film: n=0.951, k=0.023 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the CrOCN film and the SiO2 film for light with a wavelength of 230 nm were 2.220 and 1.545, respectively. The extinction coefficients k of the CrOCN film and the SiO2 film for light with a wavelength of 230 nm were 1.098 and 0.001, respectively.

[0153] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 8 was produced.

[0154] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film was etched by a fluorine-based gas and the CrOCN film was etched by a chlorine-based gas containing oxygen in succession, thereby patterning the light-shielding film.

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

[0156] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0157] Example 9 A multilayer reflective film, a protective film, and an absorber film were formed in this order on a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1.

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

[0159] Next, a light-shielding film was formed on the first etching mask film by laminating a RuCrN film (film thickness: 105.5 nm), a TaBO film (film thickness: 12.0 nm), and a SiO2 film (film thickness: 25.5 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. RuCrN film: n=0.900, k=0.021 TaBO film: n = 0.952, k = 0.029 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in refractive index for EUV light between adjacent layers among the multiple layers of the light-shielding film was 0.06 or less, and the absolute difference in extinction coefficient for EUV light was 0.03 or less. The refractive indices n of the RuCrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 1.418, 2.773, and 1.545, respectively. The extinction coefficients k of the RuCrN film, TaBO film, and SiO2 film for light with a wavelength of 230 nm were 2.895, 0.791, and 0.001, respectively.

[0160] Subsequently, a second etching mask film similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 9 was produced.

[0161] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this embodiment, in the patterning process of the light-shielding film, the SiO2 film and the TaBO film were successively etched with a fluorine-based gas, and the RuCrN film was successively etched with a chlorine-based gas containing oxygen, thereby patterning the light-shielding film.

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

[0163] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0164] Example 10 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0165] Next, a light-shielding film with a composition that changes continuously from a TaBN film to a SiO2 film was formed on the first etching mask film using a magnetron sputtering device. This resulted in a light-shielding film in which both the refractive index n and the extinction coefficient k for EUV light and light with a wavelength of 230 nm change continuously in the thickness direction of the light-shielding film. The light-shielding film of this example was formed by placing a TaB target and a SiO2 target in the same chamber and changing the sputtering conditions such as the power applied to each sputtering target and the flow rate of the sputtering gas (Ar, nitrogen) over time. The total thickness of the light-shielding film was 154.0 nm. Here, the refractive index n and extinction coefficient k for each film with respect to EUV light were as follows: TaBN film (lower region): n=0.951, k=0.033 SiO2 film (upper region): n=0.973, k=0.013 Therefore, the light-shielding film had a refractive index for EUV light that decreased toward the substrate in the film thickness direction. In addition, in the light-shielding film, 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. 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 similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Example 10 was produced.

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

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

[0169] The reflective mask 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, there was no defect in the transferred pattern, and good pattern transfer was achieved.

[0170] Comparative Example 1 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0171] Next, a light-shielding film made of a TaBO film (film thickness: 91.0 nm) was formed on the first etching mask film using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of the TaBO film with respect to 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 the thickness direction, except for the interface with another film formed in contact with the TaBO film, and the refractive index n and extinction coefficient k for EUV light and light with a wavelength of 230 nm were both constant in the thickness direction, except for the interface. In addition, 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 similar to that in Example 1 was formed on the light-shielding film. In this manner, a reflective mask blank of Comparative Example 1 was produced.

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

[0174] The reflectance of EUV light and DUV light in the light-shielding region formed by the light-shielding pattern in the obtained reflective mask was measured in the same manner as in Example 1. As a result, the reflectance of EUV light and DUV light (out-of-band light) in the light-shielding region in the reflective mask obtained by Comparative Example 1 was 0.071%, and the reflectance of DUV light was 24.37%. In this comparative example, the reflected light of EUV light and DUV light (out-of-band light) in the light-shielding region of the reflective mask could not be sufficiently reduced. From this result, it is considered that when the light-shielding film is a single film having a uniform composition in the thickness direction except for the interfaces with other media above and below the light-shielding film, it is difficult for this light-shielding film to sufficiently reduce the reflected light of EUV light and DUV light (out-of-band light) regardless of its material. In addition, since the light-shielding film of Comparative Example 1 was a single film having a uniform composition in the thickness direction and a large thickness except for the above-mentioned interfaces, the cross-sectional shape of the light-shielding pattern was not good.

[0175] Comparative Example 2 On a SiO2-TiO2-based glass substrate prepared in the same manner as in Example 1, a multilayer reflective film, a protective film, an absorber film, and a first etching mask film were formed in this order in the same manner as in Example 1.

[0176] Next, a light-shielding film was formed on the first etching mask film by laminating a CrN film (film thickness: 38.6 nm), a RuN film (film thickness: 5.0 nm), and a SiO2 film (film thickness: 26.0 nm) in this order using a DC magnetron sputtering device. Here, the refractive index n and extinction coefficient k of each film with respect to EUV light were as follows. CrN film: n=0.929, k=0.039 RuN film: n=0.888, k=0.017 SiO2 film: n=0.973, k=0.013 Therefore, the absolute difference in the refractive index for EUV light between adjacent layers of the light-shielding film exceeded 0.06. The light-shielding film did not have a refractive index that decreased toward the substrate. The refractive indexes n of the CrN film, RuN film, and SiO2 film for light with a wavelength of 230 nm were 1.339, 1.168, and 1.545, respectively. The extinction coefficients k of the CrN film, RuN film, and SiO2 film for light with a wavelength of 230 nm were 2.393, 2.986, and 0.001, respectively. The difference between the extinction coefficient of the RuN film of the light-shielding film for light with a wavelength of 230 nm and the extinction coefficient of the SiO2 film for light with a wavelength of 230 nm exceeded 2.0.

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

[0178] Next, this reflective mask blank was used to fabricate a reflective mask by the same manufacturing process as in Example 1 described above. However, in this comparative example, in the patterning process of the light-shielding film, a SiO2 film was successively patterned on the light-shielding film using a fluorine-based gas, and a RuN film and a CrN film were successively patterned using a chlorine-based gas containing oxygen.

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

[0180] 1 Board 2 Multilayer reflective film 3 Protective film 4. Absorber membrane 5 First etching mask film 6A, 6B, 6 Light shielding film 7 Second etching mask film 8. Backside conductive film 9. Resist film 10A, 10B Reflective mask blanks 20 Reflective mask A Transcription pattern region B Shading area

Claims

1. A reflective mask blank, 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, The light-shielding film includes a plurality of layers, a reflective mask blank, characterized in that in the light-shielding film, an absolute difference in refractive index for EUV light between adjacent layers among 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.

2. A reflective mask blank, 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, The reflective mask blank, wherein the light-shielding film has a refractive index with respect to EUV light that decreases toward the substrate in a thickness direction.

3. 3. The reflective mask blank according to claim 1, wherein an absolute difference between a refractive index for the EUV light of a surface of the light-shielding film farthest from the substrate or a top layer of the light-shielding film farthest from the substrate and a refractive index for the EUV light in a vacuum is 0.06 or less.

4. 3. The reflective mask blank according to claim 1, wherein an absolute difference between an extinction coefficient for the EUV light of a surface of the light-shielding film farthest from the substrate or an uppermost layer of the light-shielding film farthest from the substrate and an extinction coefficient for the EUV light in a vacuum is 0.03 or less.

5. 3. The reflective mask blank according to claim 1, wherein the light-shielding film contains at least one of chromium, tantalum, and silicon.

6. 3. The reflective mask blank according to claim 1, wherein the light-shielding film has an extinction coefficient for the EUV light that increases in a thickness direction toward the substrate.

7. 3. The reflective mask blank according to claim 1, wherein 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 a thickness direction.

8. the multilayer reflective film includes a plurality of pairs of a low refractive index layer and a high refractive index layer; 3. The reflective mask blank according to claim 1, wherein the multilayer reflective film has an interface between the low refractive index layer and the high refractive index layer that are in contact with each other in some regions, and does not have the interface in other regions.

9. 3. The reflective mask blank according to claim 1, further comprising a first etching mask film between the absorber film and the light-shielding film.

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

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

12. 12. A method for manufacturing a semiconductor device, comprising the steps of: transferring the transfer pattern of the reflective mask to a transfer target on a semiconductor substrate, using the reflective mask according to claim 11.

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