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

Abstract

To provide a reflective mask blank that reduces the shadowing effect of a reflective mask even more and enables the formation of a fine and highly accurate phase shift pattern.SOLUTION: A reflective mask blank has, in this order on a substrate, a multilayer reflection film and a phase shift film which shifts the phase of EUV light, where the phase shift film has a first layer and a second layer, the first layer is composed of a material including at least one element selected from tantalum (Ta) and chromium (Cr), and the second layer is composed of a material that contains metals including ruthenium (Ru) and at least one element selected from chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W) and rhenium (Re).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask blank, which is an original plate for producing an exposure mask used in the manufacture of a semiconductor device, a reflective mask, and a method for manufacturing a reflective mask and a semiconductor device. [Background technology]

[0002] The types of light sources of exposure devices in semiconductor device manufacturing have evolved with gradually shorter wavelengths, from g-line with a wavelength of 436 nm, i-line with a wavelength of 365 nm, KrF laser with a wavelength of 248 nm, and ArF laser with a wavelength of 193 nm. In order to realize finer pattern transfer, EUV lithography using extreme ultraviolet (EUV: Extreme Ultra Violet) with a wavelength of about 13.5 nm has been developed. In EUV lithography, a reflective mask is used because there are few materials transparent to EUV light. In this reflective mask, a multilayer reflective film that reflects exposure light is formed on a low thermal expansion substrate, and a mask structure in which a desired transfer pattern is formed on a protective film for protecting the multilayer reflective film is used as a basic structure. In addition, from the configuration of the transfer pattern, representative ones include a binary type reflective mask and a phase shift type reflective mask (halftone phase shift type reflective mask). A binary type reflective mask has a relatively thick absorber pattern that sufficiently absorbs EUV light. A phase-shifting reflective mask has a relatively thin absorber pattern (phase-shifting pattern) that attenuates EUV light by optical absorption and generates reflected light that is almost inverted in phase (about 180 degrees inversion) with respect to the reflected light from the multilayer reflective film. This phase-shifting reflective mask has the effect of improving resolution because it can obtain a high transfer optical image contrast due to the phase shift effect, just like a transmission optical phase-shifting mask. In addition, because the absorber pattern (phase-shifting pattern) of the phase-shifting reflective mask is thin, it is possible to form a fine phase-shifting pattern with high precision.

[0003] In EUV lithography, a projection optical system consisting of multiple reflecting mirrors is used due to the light transmittance. EUV light is incident on the reflective mask at an angle to prevent these multiple reflecting mirrors from blocking the projection light (exposure light). Currently, the incidence angle is mainly set to 6 degrees with respect to the vertical plane of the reflective mask substrate. As the numerical aperture (NA) of the projection optical system improves, studies are underway to change the angle to a more oblique incidence angle of around 8 degrees.

[0004] In EUV lithography, the exposure light is incident at an angle, which creates an inherent problem called the shadowing effect. The shadowing effect is a phenomenon in which exposure light is incident at an angle on an absorber pattern with a three-dimensional structure, casting a shadow on the shaded side and changing the dimensions and position of the transferred pattern. The three-dimensional structure of the absorber pattern acts as a wall, casting a shadow on the shaded side, changing the dimensions and position of the transferred pattern. For example, differences in the dimensions and positions of the transferred patterns occur between cases where the orientation of the absorber pattern is parallel to the direction of the obliquely incident light and cases where it is perpendicular, reducing the transfer accuracy.

[0005] Such reflective masks for EUV lithography and techniques related to mask blanks for fabricating the same are disclosed in Patent Documents 1 to 3. Patent Document 1 also discloses the shadowing effect. By using a phase-shift reflective mask as a reflective mask for EUV lithography, the film thickness of the phase-shift pattern is made relatively thinner than the film thickness of the absorber pattern of a binary reflective mask, thereby suppressing the deterioration of transfer accuracy caused by the shadowing effect.

[0006] [Patent Document 1] JP 2010-080659 A [Patent Document 2] JP 2004-207593 A [Patent Document 3] JP 2009-206287 A DISCLOSURE OF THEINVENTION

[0007] The finer the pattern and the higher the accuracy of the pattern dimensions and pattern position, the better the electrical characteristics and performance of the semiconductor device, and the higher the integration degree and the smaller the chip size. Therefore, EUV lithography is required to have a higher precision fine dimension pattern transfer performance than before. Currently, there is a demand for ultra-fine, high-precision pattern formation compatible with the hp16nm (half pitch 16nm) generation. In response to this demand, there is a demand to further reduce the thickness of the absorber film (phase shift film) in order to reduce the shadowing effect. In particular, in the case of EUV exposure, there is a demand to make the thickness of the absorber film (phase shift film) less than 60 nm, preferably 50 nm or less.

[0008] As disclosed in Patent Documents 1 to 3, Ta has been used as a material for forming an absorber film (phase shift film) of a reflective mask blank. However, the refractive index n of Ta in EUV light (for example, wavelength 13.5 nm) is about 0.943. Therefore, even if the phase shift effect of Ta is utilized, the lower limit of the film thickness of an absorber film (phase shift film) formed only of Ta is 60 nm. In order to make the film thickness thinner, for example, a metal material with a small refractive index n (large phase shift effect) can be used. Metal materials with a small refractive index n at a wavelength of 13.5 nm include Mo (n=0.921) and Ru (n=0.887), as shown in, for example, FIG. 7 of Patent Document 1. However, Mo is very easily oxidized, and cleaning resistance is a concern, and Ru has a low etching rate, making processing and correction difficult.

[0009] In view of the above, an object of the present invention is to provide a reflective mask blank that can further reduce the shadowing effect of a reflective mask and form a fine, highly accurate phase shift pattern, a reflective mask manufactured using the same, and a method for manufacturing a semiconductor device.

[0010] In order to solve the above problems, the present invention has the following configuration.

[0011] (Configuration 1) A first aspect of the present invention is a reflective mask blank having, on a substrate, a multilayer reflective film and a phase shift film for shifting the phase of EUV light, in this order, the phase shift film has a first layer and a second layer; The first layer is made of a material containing at least one of tantalum (Ta) and chromium (Cr), The second layer is a reflective mask blank characterized by being made of a material containing a metal including ruthenium (Ru) and at least one element selected from the group consisting of chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W) and rhenium (Re).

[0012] According to the first aspect of the present invention, a phase shift film having a small thickness required for light reflected from a phase shift pattern to obtain a predetermined phase difference compared to light reflected from an opening of a reflective mask pattern can be obtained. Therefore, the shadowing effect caused by the phase shift pattern in a reflective mask can be further reduced. According to the first aspect of the present invention, a phase shift film having a high relative reflectance (relative reflectance when the reflectance of EUV light reflected at a portion without a phase shift pattern is 100%) can be obtained. Furthermore, by using a reflective mask manufactured from the reflective mask blank of the first aspect of the present invention, the throughput during semiconductor device manufacturing can be improved.

[0013] (Configuration 2) A second aspect of the present invention is a reflective mask blank according to the first aspect, wherein the second layer is made of a material containing a metal including ruthenium (Ru) and at least one element selected from the group consisting of chromium (Cr), nickel (Ni) and cobalt (Co).

[0014] According to the second aspect of the present invention, the etching rate by the dry etching gas when patterning the phase shift film can be increased, so that the thickness of the resist film can be reduced, which is advantageous for forming a fine pattern of the phase shift film. (Configuration 3) Configuration 3 of the present invention is the reflective mask blank of configuration 1 or 2, further comprising a protective film between the multilayer reflective film and the phase shift film, the protective film being made of a material containing ruthenium (Ru), and the first layer and the second layer being laminated in this order on the protective film.

[0015] According to configuration 3 of the present invention, a first layer containing tantalum (Ta) and / or chromium (Cr) is disposed between a protective film containing ruthenium (Ru) and a second layer, so that an etching gas to which the protective film containing ruthenium (Ru) is resistant can be used when etching the first layer of the phase shift film.

[0016] (Configuration 4) A fourth aspect of the present invention is the reflective mask blank according to the first or second aspect, further comprising a protective film between the multilayer reflective film and the phase shift film, the protective film being made of a material containing silicon (Si) and oxygen (O), and the second layer and the first layer being laminated in this order on the protective film.

[0017] According to the fourth aspect of the present invention, a second layer containing ruthenium (Ru) is disposed on a protective film containing silicon (Si) and oxygen (O), so that the second layer of the phase shift film can be etched using an etching gas to which the protective film is resistant.

[0018] (Configuration 5) A fifth aspect of the present invention is a reflective mask having a phase shift pattern formed by patterning the phase shift film in the reflective mask blank according to any one of the first to fourth aspects.

[0019] According to configuration 5 of the present invention, the phase shift pattern of the reflective mask absorbs EUV light and can reflect a portion of the EUV light with a predetermined phase difference from the openings (portions where the phase shift pattern is not formed), so that the reflective mask (EUV mask) of the present invention can be manufactured by patterning the phase shift film of the reflective mask blank.

[0020] (Configuration 6) Configuration 6 of the present invention is a method for manufacturing a reflective mask, characterized in that the first layer in the reflective mask blank of any one of configurations 1 to 4 is made of a material containing tantalum (Ta), the second layer is patterned by a dry etching gas containing a chlorine-based gas and an oxygen gas, and the first layer is patterned by a dry etching gas containing a halogen-based gas not containing oxygen gas, thereby forming a phase shift pattern.

[0021] The first layer containing tantalum (Ta) can be etched by a dry etching gas containing a halogen-based gas that does not contain oxygen gas. On the other hand, the second layer containing ruthenium (Ru) is resistant to a dry etching gas containing a halogen-based gas that does not contain oxygen gas. According to the sixth aspect of the present invention, the first layer and the second layer are etched by different dry etching gases, respectively, so that the phase shift film including the first layer and the second layer can be finely patterned with high accuracy.

[0022] (Configuration 7) Configuration 7 of the present invention is a method for manufacturing a reflective mask, characterized in that the first layer in the reflective mask blank of any one of configurations 1 to 4 is made of a material containing chromium (Cr), the second layer is patterned by a dry etching gas containing oxygen gas, and the first layer is patterned by a dry etching gas containing a chlorine-based gas not containing oxygen gas, thereby forming a phase shift pattern.

[0023] The first layer containing chromium (Cr) can be etched by a dry etching gas containing a chlorine-based gas that does not contain oxygen gas. On the other hand, the second layer containing ruthenium (Ru) is resistant to a dry etching gas containing a chlorine-based gas that does not contain oxygen gas. According to the seventh aspect of the present invention, the first layer and the second layer are etched by different dry etching gases, respectively, so that the phase shift film including the first layer and the second layer can be finely patterned with high accuracy.

[0024] (Configuration 8) Configuration 8 of the present invention is a method for manufacturing a reflective mask, characterized in that the first layer in the reflective mask blank of any one of configurations 1 to 4 is made of a material containing chromium (Cr), and a phase shift pattern is formed by patterning the second layer and the first layer with a dry etching gas containing a chlorine-based gas and an oxygen gas.

[0025] According to the eighth aspect of the present invention, the first layer containing chromium (Cr) and the second layer containing ruthenium (Ru) are etched with a predetermined type of dry etching gas, whereby the phase shift film including the first layer and the second layer can be patterned in a single etching process.

[0026] (Configuration 9) Configuration 9 of the present invention is a method for manufacturing a semiconductor device, comprising the steps of setting the reflective mask of configuration 5 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a transfer substrate.

[0027] According to the semiconductor device manufacturing method of the present invention, a reflective mask can be used for manufacturing a semiconductor device, which can reduce the thickness of the phase shift film, reduce the shadowing effect, and form a fine and highly accurate phase shift pattern with a stable cross-sectional shape with less sidewall roughness. Therefore, a semiconductor device having a fine and highly accurate transfer pattern can be manufactured.

[0028] According to the reflective mask blank of the present invention (the reflective mask manufactured by using the reflective mask blank), the thickness of the phase shift film can be made thin, the shadowing effect can be reduced, and a fine and highly accurate phase shift pattern can be formed with a stable cross-sectional shape with little sidewall roughness. Therefore, a reflective mask manufactured using the reflective mask blank of this structure can form the phase shift pattern itself formed on the mask finely and with high precision, and can prevent a decrease in accuracy during transfer due to shadowing. Furthermore, by performing EUV lithography using this reflective mask, it is possible to provide a method for manufacturing a fine and highly accurate semiconductor device. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic cross-sectional view of a main portion for explaining a general configuration of a reflective mask blank of the present invention. FIG. [Diagram 2] 1A to 1C are process diagrams showing, in schematic cross-sectional views of essential parts, steps for producing a reflective mask from a reflective mask blank. [Diagram 3] FIG. 13 is a graph showing the relationship between the thickness of a phase shift film and the relative reflectance and phase difference for light with a wavelength of 13.5 nm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the following embodiment is one form for embodying the present invention, and does not limit the scope of the present invention. Note that in the drawings, the same or corresponding parts are given the same reference numerals, and the description thereof may be simplified or omitted.

[0031] <Configuration of the Reflective Mask Blank 100 and Its Manufacturing Method> FIG. 1 is a schematic cross-sectional view of a main part for explaining the configuration of a reflective mask blank 100 of this embodiment. As shown in the figure, the reflective mask blank 100 has a mask blank substrate 1 (also simply referred to as "substrate 1"), a multilayer reflective film 2, a protective film 3, and a phase shift film 4 (lower layer 41 and upper layer 42), which are laminated in this order. The multilayer reflective film 2 reflects EUV light, which is exposure light formed on the first main surface (front surface) side. The protective film 3 is provided to protect the multilayer reflective film 2, and is made of a material that is resistant to an etchant and a cleaning solution used when patterning the phase shift film 4 described later. The phase shift film 4 absorbs EUV light. In addition, a rear conductive film 5 for electrostatic chuck is formed on the second main surface (rear surface) side of the substrate 1.

[0032] In this specification, "having a multilayer reflective film 2 on the main surface of a mask blank substrate 1" means that the multilayer reflective film 2 is disposed in contact with the surface of the mask blank substrate 1, and also includes the case where another film is disposed between the mask blank substrate 1 and the multilayer reflective film 2. The same applies to other films. For example, "having a film B on a film A" means that the film A and the film B are disposed so as to be in direct contact with each other, and also includes the case where another film is disposed between the film A and the film B. In addition, in this specification, for example, "the film A is disposed in contact with the surface of the film B" means that the film A and the film B are disposed so as to be in direct contact with each other, without another film being interposed between the film A and the film B.

[0033] In this specification, when the second layer is, for example, a "thin film made of a material containing metals including ruthenium (Ru) and chromium (Cr)", it means that the second layer is a thin film made of a material containing at least substantially ruthenium (Ru) and chromium (Cr). On the other hand, when the second layer is a "thin film made of ruthenium (Ru) and chromium (Cr)", it may mean that the second layer is made of only ruthenium (Ru) and chromium (Cr). In either case, it includes the fact that the second layer contains impurities that are inevitably mixed in.

[0034] Each layer will be explained below.

[0035] <<Substrate 1>> In order to prevent distortion of the phase shift pattern 4a due to heat during exposure to EUV light, the substrate 1 is preferably one having a low thermal expansion coefficient within the range of 0±5 ppb / ° C. Examples of materials having a low thermal expansion coefficient within this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0036] The first main surface of the substrate 1 on which a transfer pattern (constituting the phase shift film 4 described later) is formed is surface-processed to have a high flatness in terms of obtaining at least pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm area of ​​the main surface of the substrate 1 on which a transfer pattern is formed. The second main surface on the opposite side to the side on which the transfer pattern is formed is a surface that is electrostatically chucked when set in an exposure device, and the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less in a 132 mm×132 mm area. The flatness of the second main surface side of the reflective mask blank 100 is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less in a 142 mm×142 mm area.

[0037] In addition, the surface smoothness of the substrate 1 is also an extremely important item. The surface roughness of the first main surface of the substrate 1 on which the transfer phase shift pattern 4a is formed is preferably 0.1 nm or less in terms of root mean square roughness (RMS). The surface smoothness can be measured by an atomic force microscope.

[0038] Furthermore, the substrate 1 preferably has high rigidity to prevent deformation due to film stress of the films (such as the multilayer reflective film 2) formed thereon, and in particular, preferably has a high Young's modulus of 65 GPa or more.

[0039] <<Multilayer reflective film 2>> The multilayer reflective film 2 imparts a function of reflecting EUV light to the reflective mask 200, and is a multilayer film in which layers containing elements with different refractive indices as main components are periodically laminated.

[0040] Generally, a multilayer film in which a thin film (high refractive index layer) of a light element or its compound, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or its compound, which is a low refractive index material, are alternately stacked for about 40 to 60 periods, is used as the multilayer reflective film 2. The multilayer film may be stacked multiple times, with a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 side as one period. The multilayer film may also be stacked multiple times, with a low refractive index layer / high refractive index layer stacked in this order from the substrate 1 side as one period. Note that the top layer of the multilayer reflective film 2, that is, the surface layer of the multilayer reflective film 2 on the opposite side to the substrate 1, is preferably a high refractive index layer. In the above-mentioned multilayer film, when a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 is stacked multiple times, with a high refractive index layer / low refractive index layer stacked in this order from the substrate 1 as one period, the top layer is a low refractive index layer. In this case, if the low refractive index layer constitutes the top surface of the multilayer reflective film 2, it is easily oxidized, and the reflectance of the reflective mask 200 decreases. For this reason, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form the multilayer reflective film 2. On the other hand, in the above-mentioned multilayer film, when a laminate structure of low refractive index layer / high refractive index layer in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side is one period, the uppermost layer is the high refractive index layer and may be left as it is.

[0041] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. As the material containing Si, in addition to simple Si, a Si compound containing Si, boron (B), carbon (C), nitrogen (N), and oxygen (O) can be used. By using a layer containing Si as the high refractive index layer, a reflective mask 200 for EUV lithography with excellent reflectance of EUV light can be obtained. In addition, in this embodiment, a glass substrate is preferably used as the substrate 1. Si also has excellent adhesion to the glass substrate. In addition, as the low refractive index layer, a simple metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof is used. For example, as the multilayer reflective film 2 for EUV light with a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 periods is preferably used. Alternatively, the high refractive index layer, which is the uppermost layer of the multilayer reflective film 2, may be made of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the uppermost layer (Si) and the Ru-based protective film 3. This can improve the mask cleaning resistance.

[0042] The reflectance of such a multilayer reflective film 2 alone is usually 65% ​​or more, with the upper limit usually being 73%. The film thickness and period of each constituent layer of the multilayer reflective film 2 may be appropriately selected according to the exposure wavelength, and are selected so as to satisfy the law of Bragg reflection. The multilayer reflective film 2 has a plurality of high refractive index layers and a plurality of low refractive index layers, but the film thicknesses of the high refractive index layers and the low refractive index layers do not have to be the same. The film thickness of the Si layer on the outermost surface of the multilayer reflective film 2 can be adjusted within a range that does not reduce the reflectance. The film thickness of the Si (high refractive index layer) on the outermost surface can be 3 nm to 10 nm.

[0043] The method of forming the multilayer reflective film 2 is known in the art. For example, the multilayer reflective film 2 can be formed by depositing each layer by ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, a Si film having a thickness of about 4 nm is first deposited on the substrate 1 using a Si target by ion beam sputtering, for example. Then, a Mo film having a thickness of about 3 nm is deposited using a Mo target. This Si film / Mo film is regarded as one period, and 40 to 60 periods are laminated to form the multilayer reflective film 2 (the outermost layer is a Si layer). In addition, when depositing the multilayer reflective film 2, it is preferable to form the multilayer reflective film 2 by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering.

[0044] <<Protective film 3>> In order to protect the multilayer reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 200 described later, a protective film 3 can be formed on the multilayer reflective film 2 or in contact with the surface of the multilayer reflective film 2. The protective film 3 also serves to protect the multilayer reflective film 2 when repairing black defects in the phase shift pattern 4a using an electron beam (EB). Here, FIG. 1 shows the case where the protective film 3 is a single layer, but it can also have a laminated structure of three or more layers. The protective film 3 is made of a material that is resistant to an etchant and a cleaning solution used when patterning the phase shift film 4. By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 can be suppressed when manufacturing the reflective mask 200 (EUV mask) using a substrate with a multilayer reflective film. Therefore, the reflectance characteristic of the multilayer reflective film 2 to EUV light is improved.

[0045] In the following, an example will be described in which the protective film 3 is a single layer. When the protective film 3 includes multiple layers, the properties of the material of the uppermost layer of the protective film 3 (the layer in contact with the phase shift film 4) become important in relation to the phase shift film 4.

[0046] In the reflective mask blank 100 of this embodiment, a material that is resistant to an etching gas used in dry etching for patterning the phase shift film 4 formed on the protective film 3 can be selected as the material of the protective film 3. When the phase shift film 4 is formed in multiple layers, a material that is resistant to an etching gas used in dry etching for patterning the bottom layer (layer in contact with the protective film 3) of the phase shift film 4 among the layers forming the phase shift film 4 can be selected as the material of the protective film 3 (when the protective film 3 includes multiple layers, the top layer of the protective film 3). The material of the protective film 3 is preferably a material that provides an etching selectivity ratio (etching rate of the bottom layer of the phase shift film 4 / etching rate of the protective film 3) of 1.5 or more, preferably 3 or more, of the bottom layer of the phase shift film 4 to the protective film 3.

[0047] For example, when the bottom layer of the phase shift film 4 is a thin film made of a material containing metal including ruthenium (Ru) and at least one of chromium (Cr), nickel (Ni) and cobalt (Co) (predetermined Ru-based material), or a material containing metal including ruthenium (Ru) and at least one of vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W) and rhenium (Re) (predetermined Ru-based material), the bottom layer of the phase shift film 4 can be etched by a mixed gas of chlorine-based gas and oxygen gas, or a dry etching gas using oxygen gas. As a material of the protective film 3 that is resistant to this etching gas, a silicon-based material such as silicon (Si), a material containing silicon (Si) and oxygen (O), or a material containing silicon (Si) and nitrogen (N) can be selected. Therefore, when the bottom layer of the phase shift film 4 in contact with the surface of the protective film 3 is a thin film made of a predetermined Ru-based material, the protective film 3 is preferably made of the above-mentioned silicon-based material. The silicon-based material has resistance to a mixed gas of a chlorine-based gas and an oxygen gas, or a dry etching gas using an oxygen gas, and the higher the oxygen content, the higher the resistance. Therefore, the material of the protective film 3 is silicon oxide (SiO x, 1≦x≦2) is more preferable, the larger x is, the more preferable, and SiO2 is particularly preferable.

[0048] Furthermore, when the bottom layer of the phase shift film 4 in contact with the surface of the protective film 3 is a thin film made of a material containing tantalum (Ta), the bottom layer of the phase shift film 4 can be etched by dry etching using a halogen-based gas that does not contain oxygen gas. A material containing ruthenium (Ru) as a main component can be selected as a material for the protective film 3 that is resistant to this etching gas.

[0049] Furthermore, when the bottom layer of the phase shift film 4 in contact with the surface of the protective film 3 is a thin film made of a material containing chromium (Cr), the bottom layer of the phase shift film 4 can be etched by dry etching using a dry etching gas of a chlorine-based gas not containing oxygen gas or a mixed gas of oxygen gas and a chlorine-based gas. As a material of the protective film 3 that is resistant to this etching gas, a material containing ruthenium (Ru) as a main component can be selected, as in the case where the above-mentioned material containing tantalum (Ta) is used for the bottom layer of the phase shift film 4.

[0050] When the bottom layer of the phase shift film 4 is made of a material containing tantalum (Ta) or chromium (Cr), the material of the protective film 3 that can be used is a material containing ruthenium as a main component, as described above. Specific examples of the material containing ruthenium as a main component include simple Ru metal, Ru alloys containing at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and materials containing nitrogen in Ru metal or Ru alloys.

[0051] In addition, the material of the protective film 3 can be made of a material containing ruthenium (Ru), which is the same material as the layer above the bottom layer of the phase shift film 4 (e.g., upper layer 42), and a metal containing at least one element selected from the group consisting of cobalt (Co), niobium (Nb), molybdenum (Mo), and rhenium (Re).

[0052] In addition, when the bottom layer of the phase shift film 4 is made of a material containing tantalum (Ta) or chromium (Cr), the protective film 3 may have, for example, the bottom and top layers made of a material containing ruthenium as the main component, with a metal or alloy other than Ru interposed between the bottom and top layers.

[0053] The Ru content of this Ru alloy is 50 atomic % or more and less than 100 atomic %, preferably 80 atomic % or more and less than 100 atomic %, and more preferably 95 atomic % or more and less than 100 atomic %. In particular, when the Ru content of the Ru alloy is 95 atomic % or more and less than 100 atomic %, it is possible to suppress diffusion of the constituent element (silicon) of the multilayer reflective film 2 into the protective film 3, while sufficiently ensuring the reflectance of EUV light, and to provide the functions of the protective film 3, namely, mask cleaning resistance, etching stopper function when the phase shift film 4 is etched, and prevention of deterioration of the multilayer reflective film 2 over time.

[0054] In EUV lithography, since there are few substances transparent to the exposure light, it is not technically easy to use an EUV pellicle that prevents foreign matter from adhering to the mask pattern surface. For this reason, pellicle-less operation that does not use a pellicle has become mainstream. In addition, in EUV lithography, exposure contamination occurs, such as the deposition of a carbon film on the mask and the growth of an oxide film due to EUV exposure. Therefore, when an EUV reflective mask is used in the manufacture of semiconductor devices, it is necessary to frequently clean the mask to remove foreign matter and contamination on the mask. For this reason, the EUV reflective mask is required to have a mask cleaning resistance that is orders of magnitude higher than that of a transmission mask for optical lithography. The reflective mask 200 has a protective film 3, which can increase the cleaning resistance against cleaning liquid.

[0055] The thickness of the protective film 3 is not particularly limited as long as it can perform the function of protecting the multilayer reflective film 2. From the viewpoint of the reflectance of EUV light, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, more preferably 1.5 nm to 6.0 nm.

[0056] The method for forming the protective film 3 can be any known film formation method without any particular limitations, and specific examples include sputtering and ion beam sputtering.

[0057] <<Phase shift film 4>> A phase shift film 4 that shifts the phase of EUV light is formed on the protective film 3. In the portion where the phase shift film 4 (phase shift pattern 4a) is formed, the EUV light is absorbed and reduced while a part of the light is reflected at a level that does not adversely affect pattern transfer. On the other hand, in the opening (the portion where the phase shift film 4 is not formed), the EUV light is reflected from the multilayer reflective film 2 through the protective film 3. The reflected light from the portion where the phase shift film 4 is formed forms a desired phase difference with the reflected light from the opening. The phase shift film 4 is formed so that the phase difference between the reflected light from the phase shift film 4 and the reflected light from the multilayer reflective film 2 is 160 degrees to 200 degrees. The light with an inverted phase difference of about 180 degrees interferes with each other at the pattern edge portion, thereby improving the image contrast of the projected optical image. With the improvement in image contrast, the resolution increases and various latitudes related to exposure such as exposure dose latitude and focus latitude are expanded. Although it depends on the pattern and exposure conditions, the target reflectance of the phase shift film 4 to obtain this phase shift effect is generally 2% or more in terms of relative reflectance. In order to obtain a sufficient phase shift effect, the reflectance of the phase shift film 4 is preferably 6% or more in terms of relative reflectance. When the relative reflectance is high, 10% or more, more preferably 15% or more, the phase difference can be set to 130 degrees to 160 degrees, or 200 degrees to 230 degrees in order to further improve the contrast. Here, the relative reflectance of the phase shift film 4 (phase shift pattern 4a) is the reflectance of the EUV light reflected from the phase shift pattern 4a when the reflectance of the EUV light reflected from the multilayer reflective film 2 (including the multilayer reflective film 2 with the protective film 3) in the part without the phase shift pattern 4a is 100%. In this specification, the relative reflectance may be simply referred to as "reflectance".

[0058] In order to obtain a sufficient phase shift effect, the absolute reflectance of the phase shift film 4 is preferably 9% or more. Here, the absolute reflectance of the phase shift film 4 (phase shift pattern 4a) refers to the reflectance (ratio of incident light intensity to reflected light intensity) of EUV light reflected from the phase shift film 4 (or phase shift pattern 4a).

[0059] In order to further improve the resolution and the throughput in manufacturing the semiconductor device, the relative reflectance of the phase shift pattern 4a is preferably 6% to 40%, more preferably 6% to 35%, even more preferably 15% to 35%, and even more preferably 15% to 25%.

[0060] In order to further improve the resolution and increase the throughput in manufacturing semiconductor devices, the absolute reflectance of the phase shift film 4 (or the phase shift pattern 4a) is desirably 4% to 27%, and more desirably 10% to 17%.

[0061] The phase shift film 4 of this embodiment has a first layer and a second layer. The first layer is made of a material containing at least one of tantalum (Ta) and chromium (Cr). The second layer is made of a material containing a metal including ruthenium (Ru) and at least one of chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).

[0062] The phase shift film 4 of the reflective mask blank 100 of this embodiment includes a first layer and a second layer of a predetermined material, and thus a phase shift pattern 4a having a relative reflectance of 6% to 40% can be obtained. The phase shift film 4 of the reflective mask blank 100 of this embodiment can have an absolute reflectance of 4% to 27% by using a predetermined material. Furthermore, the phase shift film 4 of the reflective mask blank 100 of this embodiment has a small film thickness required to obtain a predetermined phase difference (phase difference between the light reflected from the opening and the light reflected from the phase shift pattern 4a). Therefore, in the reflective mask 200, the shadowing effect caused by the phase shift pattern 4a can be further reduced. Furthermore, by using the reflective mask 200 manufactured from the reflective mask blank 100 of this embodiment, the throughput during the manufacture of a semiconductor device can be improved.

[0063] The following describes the first layer of the phase shift film 4 of the reflective mask blank 100 of this embodiment. The first layer is made of a material containing at least one of tantalum (Ta) and chromium (Cr).

[0064] The material of the first layer containing tantalum (Ta) includes a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H). Among these, it is particularly preferable that the material of the first layer is a material containing tantalum (Ta) and nitrogen (N). Specific examples of such a material include tantalum nitride (TaN), tantalum oxynitride (TaON), tantalum boride nitride (TaBN), and tantalum boride oxynitride (TaBON).

[0065] When the first layer contains Ta and N, the composition range of Ta and N (atomic ratio, Ta:N) is preferably from 3:1 to 20:1, more preferably from 4:1 to 12:1. The film thickness is preferably from 2 to 55 nm, more preferably from 2 to 30 nm.

[0066] The material of the first layer containing chromium (Cr) includes a material containing chromium (Cr) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H). Among these, it is particularly preferable that the material of the first layer is a material containing chromium (Cr) and carbon (C). Specific examples of such materials include chromium nitride (CrC), chromium oxide nitride (CrOC), chromium carbonitride (CrCN), and chromium oxide carbonitride (CrOCN).

[0067] When the first layer contains Cr and C, the composition range of Cr and C (atomic ratio, Cr:C) is preferably from 5:2 to 20:1, more preferably from 3:1 to 12:1. The film thickness is preferably from 2 to 55 nm, more preferably from 2 to 25 nm.

[0068] When the phase difference of the phase shift film 4 is 160 degrees to 200 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows. When the relative reflectance of the phase shift film 4 is 6% to 40% or the absolute reflectance is 4% to 27%, the first layer made of a material containing at least one of tantalum (Ta) and chromium (Cr) preferably has a refractive index n of 0.930 to 0.960 and an extinction coefficient k of 0.020 to 0.041 for EUV light. When the relative reflectance is 6% to 35% or the absolute reflectance is 4% to 23%, the first layer preferably has a refractive index n of 0.930 to 0.960 and an extinction coefficient k of 0.023 to 0.041 for EUV light. When the relative reflectance is 15% to 35% or the absolute reflectance is 10% to 23%, the refractive index n of the first layer to EUV light is preferably 0.930 to 0.950 and the extinction coefficient k is preferably 0.023 to 0.033.When the relative reflectance is 15% to 25% or the absolute reflectance is 10% to 17%, the refractive index n of the first layer to EUV light is preferably 0.935 to 0.950 and the extinction coefficient k is preferably 0.026 to 0.033.

[0069] When the phase difference of the phase shift film 4 is 130 degrees to 160 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows: When the relative reflectance of the phase shift film 4 is 10% to 40% or the absolute reflectance is 6.7% to 27%, the first layer made of a material containing at least one of tantalum (Ta) and chromium (Cr) preferably has a refractive index n of 0.930 to 0.960 and an extinction coefficient k of 0.025 to 0.046 for EUV light.

[0070] When the phase difference of the phase shift film 4 is 200 degrees to 230 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows: When the relative reflectance of the phase shift film 4 is 10% to 40% or the absolute reflectance is 6.7% to 27%, it is preferable that the refractive index n of the first layer to EUV light is 0.930 to 0.960 and the extinction coefficient k is 0.015 to 0.036.

[0071] The second layer (hereinafter, may be simply referred to as "predetermined Ru-based material") of the phase shift film 4 of the reflective mask blank 100 of this embodiment will be described. The second layer is made of a material containing a metal including ruthenium (Ru) and at least one element selected from the group consisting of chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).

[0072] The refractive index n of Ru is n=0.886 (extinction coefficient k=0.017), which is preferable as a material for the phase shift film 4 with high reflectance. However, Ru-based compounds such as RuO tend to have a crystallized structure and have poor processing characteristics. That is, crystal grains of crystallized metal tend to have large sidewall roughness when forming the phase shift pattern 4a. This may have an adverse effect when forming the predetermined phase shift pattern 4a. On the other hand, if the metal material of the phase shift film 4 is amorphous, the adverse effect when forming the phase shift pattern 4a can be reduced. By adding a predetermined element (X) to Ru, the metal material of the phase shift film 4 can be made amorphous and the processing characteristics can be improved. At least one of Cr, Ni, Co, V, Nb, Mo, W, and Re can be selected as the predetermined element (X).

[0073] The refractive index n and extinction coefficient k of Ni are n=0.948 and k=0.073. The refractive index n and extinction coefficient k of Co are n=0.933 and k=0.066, and the refractive index n and extinction coefficient k of Cr are n=0.932 and k=0.039. The refractive index n and extinction coefficient k of V are n=0.944 and k=0.025, the refractive index n and extinction coefficient k of Nb are n=0.933 and k=0.005, the refractive index n and extinction coefficient k of Mo are n=0.923 and k=0.007, the refractive index n and extinction coefficient k of W are n=0.933 and k=0.033, and the refractive index n and extinction coefficient k of Re are n=0.914 and k=0.04. Binary materials (RuCr, RuNi, and RuCo) in which a specific element (X) is added to Ru can reduce the thickness of the phase shift film 4 compared to the conventional material RuTa. In addition, since Ni and Co have a larger extinction coefficient k than Cr, the thickness of the phase shift film 4 can be reduced by selecting Ni and / or Co as the element (X) compared to selecting Cr.

[0074] When the phase difference of the phase shift film 4 is 160 degrees to 200 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows. When the relative reflectance of the phase shift film 4 is 6% to 40% or the absolute reflectance is 4% to 27%, the refractive index n of the second layer made of a material in which a predetermined element (X) is added to Ru is preferably 0.860 to 0.950 and the extinction coefficient k is preferably 0.008 to 0.095 for EUV light. When the relative reflectance is 6% to 35% or the absolute reflectance is 4% to 23%, the refractive index n of the second layer to EUV light is preferably 0.860 to 0.950 and the extinction coefficient k is preferably 0.008 to 0.095. When the relative reflectance is 15% to 35% or the absolute reflectance is 10% to 23%, the refractive index n is preferably 0.860 to 0.950 and the extinction coefficient k is preferably 0.008 to 0.050. When the relative reflectance is 15% to 25% or the absolute reflectance is 10% to 17%, the refractive index n of the second layer to EUV light is preferably 0.890 to 0.950 and the extinction coefficient k is preferably 0.020 to 0.050.

[0075] When the phase difference of the phase shift film 4 is 130 degrees to 160 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows. When the relative reflectance of the phase shift film 4 is 10% to 40% or the absolute reflectance is 6.7% to 27%, the refractive index n of the second layer made of a material in which a specific element (X) is added to Ru is preferably 0.860 to 0.950 and the extinction coefficient k is preferably 0.009 to 0.095 for EUV light. When the relative reflectance is 15% to 35% or the absolute reflectance is 10% to 23%, the refractive index n of the second layer to EUV light is preferably 0.860 to 0.950 and the extinction coefficient k is preferably 0.01 to 0.073.

[0076] When the phase difference of the phase shift film 4 is 200 degrees to 230 degrees, the ranges of the refractive index n and the extinction coefficient k are as follows. When the relative reflectance of the phase shift film 4 is 10% to 40% or the absolute reflectance is 6.7% to 27%, the refractive index n of the second layer to EUV light is preferably 0.860 to 0.940 and the extinction coefficient k is preferably 0.008 to 0.057. When the relative reflectance is 15% to 35% or the absolute reflectance is 10% to 23%, the refractive index n of the second layer to EUV light is preferably 0.860 to 0.939 and the extinction coefficient k is preferably 0.009 to 0.045.

[0077] The phase difference and reflectance of the phase shift film 4 can be adjusted by changing the refractive index n, the extinction coefficient k, the thickness of the first layer, and the thickness of the second layer. The thickness of the first layer is preferably 55 nm or less, more preferably 30 nm or less. The thickness of the first layer is preferably 2 nm or more. The thickness of the second layer is preferably 50 nm or less, more preferably 35 nm or less. The thickness of the second layer is preferably 5 nm or more, more preferably 15 nm or more. The thickness of the phase shift film 4 (total thickness of the first layer and the second layer) is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. The thickness of the phase shift film 4 is preferably 25 nm or more. In addition, when the protective film 3 is provided, the phase difference and reflectance of the phase shift film 4 can also be adjusted in consideration of the refractive index n, extinction coefficient k, and thickness of the protective film 3.

[0078] Binary materials (RuCr, RuNi, and RuCo) in which a specific element (X) is added to Ru have better processing characteristics than the conventional material RuTa. When Ta is oxidized, it is difficult to etch it with chlorine-based gas and oxygen gas. In particular, RuCr has excellent processing characteristics because it can be easily etched with a mixed gas of chlorine-based gas and oxygen gas. Furthermore, when the material of the first layer contains Cr, RuCr makes it possible to process the first and second layers with the same dry etching gas.

[0079] Binary materials (RuCr, RuNi, and RuCo) in which a specific element (X) is added to Ru have an amorphous structure and can be easily etched with a mixture of chlorine gas and oxygen gas. These materials can also be etched with oxygen gas. The same is thought to be true for ternary materials (RuCrNi, RuCrCo, and RuNiCo) and quaternary materials (RuCrNiCo).

[0080] In addition to the above binary materials, binary materials in which V, Nb, Mo, W or Re are added to Ru (RuV, RuNb, RuMo, RuW and RuRe) have better workability than the conventional material RuTa. Like RuCr, RuW and RuMo have particularly excellent workability.

[0081] In addition, binary materials (RuV, RuNb, RuMo, RuW, and RuRe) in which a specific element (X) is added to Ru have an amorphous structure and can be easily etched with a mixture of chlorine gas and oxygen gas. These materials can also be etched with oxygen gas. The same is thought to be true for ternary and quaternary materials.

[0082] Next, the compounding ratio of Ru and the predetermined element (X) in the predetermined Ru-based material will be described.

[0083] The relative reflectance and absolute reflectance of a given Ru-based material increase with increasing Ru content. The reflected light of the phase shift film 4 is a superposition of the surface reflected light from the surface of the phase shift film 4 and the back-reflected light transmitted through the phase shift film 4 at the back surface of the phase shift film 4 (the interface between the phase shift film 4 and the protective film 3 or the multilayer reflective film 2). Therefore, the intensity of the reflected light of the phase shift film 4 has a periodic structure that depends on the film thickness of the phase shift film 4. As a result, the reflectance and phase difference of the phase shift film 4 also show a periodic structure that depends on the film thickness, as shown in an example in FIG. 3. FIG. 3 is a diagram showing the relationship between the thickness of the phase shift film 4 and the relative reflectance and phase difference of EUV light when the thickness of the lower layer 41 (TaN film) is fixed at 15.5 nm and the thickness of the upper layer 42 (RuCr film) is changed, in the case where the phase shift film 4 is composed of two layers, a lower layer 41 of a TaN film and an upper layer 42 of a RuCr film, and the atomic ratio of Ru and Cr in the RuCr film is Ru:Cr=90:10. The refractive index n and extinction coefficient k of the material of the phase shift film 4 affect this periodic structure. On the other hand, the reflected light from the phase shift pattern 4a needs to have a predetermined phase difference (for example, a phase difference of 180 degrees) with respect to the reflected light from the opening. Taking the above into consideration, the relationship between the relative reflectance of the phase shift film 4, the composition and the film thickness of a predetermined Ru-based material was examined, and as a result, a preferable range can be shown for the composition and film thickness of a predetermined Ru-based material according to the relative reflectance of the phase shift film 4, as described below. As shown in FIG. 3, when the lower layer 41 of the phase shift film 4 is a 15.5 nm TaN film and the upper layer 42 is a RuCr film (Ru:Cr=90:10), the thickness of the RuCr film is 22.8 nm (the thickness of the phase shift film 4 is 38.3 nm), the relative reflectance to the multilayer reflective film (with a protective film) is 20.1% (absolute reflectance is 13.4%), and the phase difference is approximately 180 degrees.

[0084] Specifically, when phase shift film 4 is composed of two layers, a first layer and a second layer, and the first layer of phase shift film 4 is made of a material containing at least one of tantalum (Ta) and chromium (Cr), when the relative reflectance of the material of the second layer is 6% to 40%, the relationship between the composition (atomic ratio) of a specified Ru-based material and the film thickness is as follows:

[0085] That is, when the material of the second layer contains Ru and Cr, the composition range (atomic ratio) of Ru and Cr is preferably Ru:Cr=40:1 to 1:20, more preferably 40:1 to 3:7, and the film thickness is preferably 5 to 50 nm, more preferably 15 to 35 nm.

[0086] When the material of the second layer contains Ru and Ni, the composition range (atomic ratio) of Ru and Ni is preferably Ru:Ni=40:1 to 1:6, more preferably 40:1 to 1:1. The film thickness is preferably 5 to 45 nm, more preferably 12 to 33 nm.

[0087] When the material of the second layer contains Ru and Co, the composition range (atomic ratio) of Ru and Co is preferably Ru:Co=40:1 to 1:7, more preferably 40:1 to 2:3, and the film thickness is preferably 5 to 40 nm, more preferably 10 to 30 nm.

[0088] When the material of the second layer contains Ru and V, the composition range (atomic ratio) of Ru and V is preferably Ru:V=40:1 to 1:20, more preferably 40:1 to 2:7, and the film thickness is preferably 5 to 60 nm, more preferably 16 to 50 nm.

[0089] When the material of the second layer contains Ru and Nb, the composition range (atomic ratio) of Ru and Nb is preferably Ru:Nb=40:1 to 5:1, more preferably 40:1 to 9:1, and the film thickness is preferably 5 to 33 nm, more preferably 16 to 33 nm.

[0090] When the material of the second layer contains Ru and Mo, the composition range (atomic ratio) of Ru and Mo is preferably Ru:Mo=40:1 to 4:1, more preferably 40:1 to 9:1, and the film thickness is preferably 5 to 33 nm, more preferably 15 to 33 nm.

[0091] When the material of the second layer contains Ru and W, the composition range (atomic ratio) of Ru and W is preferably Ru:W=40:1 to 1:20, more preferably 40:1 to 17:33, and the film thickness is preferably 5 to 50 nm, more preferably 16 to 40 nm.

[0092] When the material of the second layer contains Ru and Re, the composition range (atomic ratio) of Ru and Re is preferably Ru:Re=40:1 to 1:20, more preferably 40:1 to 9:16, and the film thickness is preferably 5 to 38 nm, more preferably 16 to 33 nm.

[0093] As described above, by setting the composition ratio of Ru to Cr, Ni, Co, V, Nb, Mo, W and Re within a predetermined range, it is possible to obtain a second layer having a thin film thickness and providing a phase shift film 4 with high reflectance and a predetermined phase difference.

[0094] In the above description, the binary Ru-based material has been mainly described, but the ternary materials (RuCrNi, RuCrCo, RuNiCo, and RuCrW) and the quaternary materials (RuCrNiCo and RuCrCoW) have the same properties as the binary Ru-based material. Therefore, the ternary or quaternary material can be used as the Ru-based material.

[0095] The predetermined Ru-based material may contain at least one of Ru, Cr, Ni, Co, V, Nb, Mo, W, and Re, and other elements, within a range that does not significantly affect the refractive index and extinction coefficient. The predetermined Ru-based material may contain elements such as nitrogen (N), oxygen (O), carbon (C), and boron (B). For example, when nitrogen (N) is added to the predetermined Ru-based material, oxidation of the phase shift film 4 can be suppressed, and the properties of the phase shift film 4 can be stabilized. When nitrogen (N) is added to the predetermined Ru-based material, the crystalline state can be easily made amorphous regardless of the film formation conditions of sputtering. In this case, the nitrogen content is preferably 1 atomic % or more, and more preferably 3 atomic % or more. The nitrogen content is preferably 10 atomic % or less. Oxygen (O), carbon (C), boron (B), and the like can also be added to the material of the phase shift film 4 within a range that does not significantly affect the refractive index and extinction coefficient in order to stabilize the phase shift film 4. When the material of the phase shift film 4 contains Ru and at least one of Cr, Ni, Co, V, Nb, Mo, W, and Re, and other elements, the content of the other elements is preferably 10 atomic % or less, and more preferably 5 atomic % or less.

[0096] The phase shift film 4 of the above-mentioned predetermined Ru-based material can be formed by a known method such as a magnetron sputtering method such as a DC sputtering method or an RF sputtering method, etc. Also, the target can be an alloy target of Ru and at least one element selected from the group consisting of Cr, Ni, Co, V, Nb, Mo, W, and Re.

[0097] In addition, a film can be formed by co-sputtering using a Ru target, a Cr target, a Ni target, a Co target, a V target, a Nb target, a Mo target, a W target, and / or a Re target as targets. Co-sputtering has the advantage that the composition ratio of metal elements can be easily adjusted, but compared with alloy targets, the crystalline state of the film may tend to have a columnar structure. During sputtering, the film can be formed so that nitrogen (N) is contained in the film, thereby making the crystalline state amorphous.

[0098] In this specification, when the phase shift film 4 is composed of two layers, the layer in contact with the multilayer reflective film 2 or the protective film 3 is referred to as the lower layer 41, and the layer disposed on the surface of the phase shift film 4 opposite to the multilayer reflective film 2 or the protective film 3 is referred to as the upper layer 42. When the phase shift film 4 is composed of three or more layers, the lower layer 41 is generally disposed at an arbitrary position on the side where the multilayer reflective film 2 or the protective film 3 is present, relative to the upper layer 42. The lower layer 41 can be the bottom layer of the phase shift film 4 (the layer in contact with the multilayer reflective film 2 or the protective film 3 among the layers forming the phase shift film 4), and the upper layer 42 can be the top layer of the phase shift film 4 (the layer farthest from the bottom layer among the layers forming the phase shift film 4). In the following description, each of the first layer and the second layer is either the upper layer 42 or the lower layer 41. That is, if the first layer of a given material is top layer 42, the second layer of the given material is bottom layer 41, and if the first layer of a given material is bottom layer 41, the second layer of the given material is top layer 42.

[0099] The phase shift film 4 can be composed of only two layers, the first layer and the second layer, described above. The phase shift film 4 can also include a film other than the first layer and the second layer. In this embodiment, the phase shift film 4 is preferably composed of only two layers, the first layer and the second layer, described above. When the phase shift film 4 is composed of only two layers, the first layer and the second layer, the number of steps in manufacturing the mask blank can be reduced, improving production efficiency.

[0100] Furthermore, when the phase shift film 4 includes two or more layers, the reflectance and phase difference can be changed by adjusting the film thickness without changing the composition of either the first layer or the second layer, or the compositions of the first layer and the second layer.

[0101] When the phase shift film 4 includes three or more layers, it can have a laminated structure in which the first layer and the second layer are alternately laminated in three or more layers. By adjusting the film thickness of the first layer and the second layer, it is possible to improve the stability of the phase difference and reflectance against the film thickness fluctuation. In addition, by making the second layer the uppermost layer of the phase shift film 4, it is possible to improve the cleaning resistance.

[0102] As described above, the phase shift film 4 may be composed of three or more layers, but for ease of explanation, the arrangement of the first and second layers will be described using an example in which the phase shift film 4 is composed of two layers, the first and second layers. The following example will also describe a case in which the reflective mask blank 100 has a protective film 3. As described below, it is preferable to appropriately select the type of material of the protective film 3 and the arrangement of the first and second layers, taking into consideration the type of material of the protective film 3 and which of the first and second layers is to be the lower layer 41. This is because the type of dry etching gas capable of dry etching and the type of dry etching gas resistant to dry etching differ depending on the type of material.

[0103] First, the etching characteristics of the first layer, the second layer and the protective film 3 will be described below.

[0104] When the first layer is made of a material containing tantalum (Ta), the first layer can be patterned by a dry etching gas containing a halogen-based gas that does not contain oxygen gas.

[0105] When the first layer is a material containing chromium (Cr), the first layer can be patterned by a chlorine-based dry etching gas, which may or may not contain oxygen gas.

[0106] The second layer, which is a predetermined Ru-based material, can be patterned by a dry etching gas containing oxygen, such as a gas containing only oxygen or a gas containing oxygen and a chlorine-based gas.

[0107] When the material of the protective film 3 is silicon (Si), a material containing silicon (Si) and oxygen (O), or a material containing silicon (Si) and nitrogen (N), the protective film 3 is resistant to dry etching using a mixed gas of a chlorine-based gas and oxygen gas, or a dry etching gas using oxygen gas. Note that the second layer, which is a predetermined Ru-based material, can be etched using this dry etching gas.

[0108] When the material of the protective film 3 contains ruthenium (Ru) as a main component, the protective film 3 is resistant to dry etching using a halogen-based gas that does not contain oxygen gas. Note that the first layer containing tantalum (Ta) can be etched using this dry etching gas.

[0109] When the material of the protective film 3 contains ruthenium (Ru) as a main component, the protective film 3 is resistant to dry etching using a dry etching gas that does not contain oxygen gas or contains a chlorine-based gas with a reduced amount of oxygen gas. The first layer containing chromium (Cr) can be etched using this dry etching gas.

[0110] In view of the etching characteristics of the first layer, the second layer, and the protective film 3 described above, it is preferable that the type of material for the protective film 3 and the arrangement of the first layer and the second layer are as follows.

[0111] When the protective film 3 is made of a material containing ruthenium (Ru), it is preferable that a first layer and a second layer are laminated in this order on the protective film 3. By disposing the first layer containing tantalum (Ta) and / or chromium (Cr) between the protective film 3 containing ruthenium (Ru) and the second layer, an etching gas that is resistant to the protective film 3 containing ruthenium (Ru) can be used when etching the first layer of the phase shift film 4.

[0112] When the protective film 3 is a silicon-based material made of a material containing silicon (Si) and oxygen (O) or a material containing silicon (Si) and nitrogen (N), it is preferable that a second layer and a first layer are laminated in this order on the protective film 3. By disposing the second layer containing ruthenium (Ru) on the protective film 3 containing a silicon-based material, an etching gas that is resistant to the protective film 3 containing a silicon-based material can be used when etching the second layer containing ruthenium (Ru) of the phase shift film 4.

[0113] When the first layer of the phase shift film 4 is made of a material containing tantalum (Ta), the first layer can be patterned by a dry etching gas containing a halogen-based gas that does not contain oxygen gas. Also, the second layer can be patterned by a dry etching gas containing a chlorine-based gas and oxygen gas. This is because the material of the first layer containing tantalum (Ta) is resistant to the dry etching gas containing a chlorine-based gas and oxygen gas, and the material of the second layer is resistant to the dry etching gas that does not contain oxygen gas. In this case, it is necessary to appropriately select the material of the protective film 3 depending on which of the first layer and the second layer is in contact with the protective film 3 (the lower layer 41). That is, when the first layer is the lower layer 41, a material containing ruthenium (Ru) as a main component can be used as the protective film 3. Also, when the second layer is the lower layer 41, a silicon-based material, particularly a material containing silicon (Si) and oxygen (O) can be used as the protective film 3.

[0114] When the first layer of the phase shift film 4 is a material containing chromium (Cr), the second layer can be patterned by a dry etching gas containing oxygen gas, and the first layer can be patterned by a dry etching gas containing a chlorine-based gas not containing oxygen gas. In this case, it is necessary to appropriately select the material of the protective film 3 depending on which of the first layer and the second layer is in contact with the protective film 3 (the lower layer 41). That is, when the first layer is the lower layer 41, the protective film 3 can be made of a material containing ruthenium (Ru) as a main component. When the second layer is the lower layer 41, the protective film 3 can be made of a silicon-based material, particularly a material containing silicon (Si) and oxygen (O). By etching the first layer containing chromium (Cr) and the second layer containing ruthenium (Ru) with different dry etching gases, the phase shift film 4 can be finely patterned with high precision.

[0115] When the first layer of the phase shift film 4 is made of a material containing chromium (Cr), the second layer and the first layer can be patterned by a dry etching gas containing a chlorine-based gas and an oxygen gas. In this case, both the first layer and the second layer can be etched in a single etching process. Therefore, the phase shift film 4 can be patterned with an appropriate throughput. In this case, the flow rate ratio of the chlorine-based gas:oxygen-based gas is preferably 3:1 to 10:1.

[0116] It is preferable to use a silicon-based material, particularly a material containing silicon (Si) and oxygen (O), that is resistant to the dry etching gas of a mixed gas of a chlorine-based gas and an oxygen gas, for the protective film 3. A material containing ruthenium (Ru) as a main component can also be used for the protective film 3, but in this case, it is necessary to reduce the amount of oxygen gas in the mixed gas so that the protective film 3 is not etched by the dry etching gas. Therefore, in this case, the flow rate ratio of the chlorine-based gas:oxygen gas is preferably 10:1 to 40:1.

[0117] In addition, the material of the protective film 3 may be any material other than those mentioned above, so long as the etching selectivity ratio of the phase shift film 4 to the protective film 3 (etching rate of the phase shift film 4 / etching rate of the protective film 3) is 1.5 or more, preferably 3 or more, in dry etching using a predetermined dry etching gas.

[0118] The halogen-based gas used in the above-mentioned dry etching may be a fluorine-based gas and / or a chlorine-based gas. The fluorine-based gas may be CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, or F2. The chlorine-based gas may be Cl2, SiCl4, CHCl3, CCl4, or BCl3. If necessary, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 at a predetermined ratio may be used. These etching gases may further contain an inert gas such as He and / or Ar, if necessary.

[0119] Since EUV light has a short wavelength, the phase difference and reflectance tend to be highly dependent on the film thickness. Therefore, the phase difference and reflectance are required to be stable against the film thickness fluctuation of the phase shift film 4. However, as shown in FIG. 3, the phase difference and reflectance each show an oscillation structure with respect to the film thickness of the phase shift film 4. Since the oscillation structures of the phase difference and reflectance are different, it is difficult to determine a film thickness that simultaneously stabilizes the phase difference and reflectance.

[0120] Therefore, even if the thickness of phase shift film 4 varies slightly from the design value (for example, within a range of ±0.5% from the designed thickness), it is desirable that the phase difference variation between surfaces be within a range of a predetermined phase difference of ±2 degrees (for example, a range of 180 degrees ±2 degrees when the phase difference is 180 degrees), and that the reflectance variation between surfaces be within a range of a predetermined reflectance of ±0.2% (for example, a range of 6% ±0.2% when the relative reflectance is 6%).

[0121] Since the upper layer 42 of the phase shift film 4 may be thinned during removal and / or cleaning of the resist film or etching mask film, when attention is focused on suppressing the phase difference variation of the phase shift film 4, it is preferable to place the second layer, which has a large contribution to the phase difference, in the lower layer 41.

[0122] In addition, when the phase shift film 4 is formed of the top layer, the upper layer 42, and the lower layer 41, the reflection of EUV light from the surface of the top layer is suppressed, so that the vibration structure is smoothed and a stable phase difference and reflectance can be obtained against film thickness fluctuation. The material of such a top layer is preferably a silicon compound or a tantalum compound having a refractive index larger than that of the upper layer 42 of the phase shift film 4. The silicon compound includes a material containing Si and at least one element selected from N, O, C, and H, and preferably includes SiO2, SiON, and Si3N4. The tantalum compound includes a material containing Ta and at least one element selected from N, O, C, H, and B, and preferably includes a material containing Ta and O. The film thickness of the top layer is preferably 10 nm or less, more preferably 1 to 6 nm, and even more preferably 3 to 5 nm. When the upper layer 42 is a RuCr film, for example, the top layer can be a SiO2 film or a Ta2O5 film.

[0123] In this way, by forming the phase shift film 4 as a multi-layer film, it becomes possible to add various functions to each layer.

[0124] The crystal structure of the phase shift film 4 of the reflective mask blank 100 of this embodiment is preferably amorphous. By making the crystal structure of the phase shift film 4 amorphous, adverse effects of crystal particles of metal or the like when forming the phase shift pattern 4a can be reduced. Therefore, by making the crystal structure of the phase shift film 4 amorphous, it is possible to increase the etching speed when etching the phase shift film 4, improve the pattern shape, and improve processing characteristics.

[0125] Furthermore, when attention is focused on improving the cross-sectional shape of the phase shift pattern 4a, it is preferable to dispose the first layer, which has a faster etching rate than the second layer, in the lower layer 41.

[0126] <<Etching mask film>> An etching mask film can be formed on the phase shift film 4 or in contact with the surface of the phase shift film 4. The material of the etching mask film is one that has a high etching selectivity of the phase shift film 4 to the etching mask film. Here, the "etching selectivity of B to A" refers to the ratio of the etching rate of A, which is a layer that is not to be etched (a layer that serves as a mask), to B, which is a layer that is to be etched. Specifically, it is specified by the formula "etching selectivity of B to A=etching rate of B / etching rate of A". In addition, "high selectivity" refers to a selectivity value defined above that is high with respect to a comparative object. The etching selectivity of the phase shift film 4 to the etching mask film is preferably 1.5 or more, more preferably 3 or more.

[0127] When the second layer (predetermined ruthenium (Ru)-based material) is the top layer of the phase shift film 4, the second layer can be etched by dry etching using a chlorine-based gas containing oxygen or oxygen gas. As a material for the etching mask film that increases the etching selectivity of the phase shift film 4 made of a predetermined ruthenium (Ru)-based material to the etching mask film, a silicon (Si)-based material or a tantalum (Ta)-based material can be used.

[0128] When the top layer of the phase shift film 4 is the second layer, the silicon (Si)-based material that can be used for the etching mask film is a material of silicon or a silicon compound. Examples of the silicon compound include a material containing Si and at least one element selected from N, O, C, and H, and a silicon-based material such as metal silicon (metal silicide) or a metal silicon compound (metal silicide compound) containing a metal in silicon or a silicon compound. Examples of the metal silicon compound include a material containing a metal, Si, and at least one element selected from N, O, C, and H.

[0129] When the top layer of the phase shift film 4 is the second layer, the tantalum (Ta)-based material that can be used as the etching mask film can be a material containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H). Among these, it is particularly preferable to use a material containing tantalum (Ta) and oxygen (O) as the material of the etching mask film. Specific examples of such materials include tantalum oxide (TaO), tantalum oxynitride (TaON), tantalum boride oxide (TaBO), and tantalum boride oxynitride (TaBON).

[0130] When the first layer is the top layer of the phase shift film 4 and is made of a material containing tantalum (Ta), examples of the material of the etching mask film that increases the etching selectivity of the first layer to the etching mask film include chromium (Cr)-based materials and silicon (Si)-based materials. Examples of the chromium (Cr)-based materials include chromium or chromium compound materials. Examples of the chromium compound include materials containing Cr and at least one element selected from N, O, C, and H. Examples of the silicon compound that can be used are the same materials as those described above when the second layer is the top layer of the phase shift film 4.

[0131] When the first layer is the top layer of the phase shift film 4 and is made of a material containing chromium (Cr), examples of the material of the etching mask film that increases the etching selectivity of the first layer to the etching mask film include silicon (Si)-based materials and tantalum (Ta)-based materials. The silicon (Si)-based materials and tantalum (Ta)-based materials may be the same as those described above when the second layer is the top layer of the phase shift film 4.

[0132] The thickness of the etching mask film is desirably 3 nm or more from the viewpoint of obtaining the function as an etching mask for accurately forming a transfer pattern on the phase shift film 4. Moreover, the thickness of the etching mask film is desirably 15 nm or less from the viewpoint of making the thickness of the resist film 11 thin.

[0133] <<Backside conductive film 5>> A back surface conductive film 5 for an electrostatic chuck is generally formed on the second main surface (back surface) side of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The electrical characteristics (sheet resistance) required for the back surface conductive film 5 for an electrostatic chuck are generally 100 Ω / □ (Ω / Square) or less. The back surface conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering using a target of a simple metal or an alloy such as chromium or tantalum.

[0134] The chromium (Cr)-containing material of the back surface conductive film 5 is preferably a Cr compound containing Cr and at least one element selected from boron, nitrogen, oxygen, and carbon. Examples of the Cr compound include CrN, CrON, CrCN, CrCO, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.

[0135] The tantalum (Ta)-containing material of the back surface conductive film 5 is preferably Ta, an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0136] It is preferable that the material containing tantalum (Ta) or chromium (Cr) has a small amount of nitrogen (N) present in its surface layer. Specifically, the nitrogen content in the surface layer of the back surface conductive film 5 made of a material containing tantalum (Ta) or chromium (Cr) is preferably less than 5 atomic %, and more preferably the surface layer does not substantially contain nitrogen. This is because the lower the nitrogen content in the surface layer of the back surface conductive film 5 made of a material containing tantalum (Ta) or chromium (Cr), the higher the wear resistance.

[0137] The back surface conductive film 5 is preferably made of a material containing tantalum and boron. By making the back surface conductive film 5 of a material containing tantalum and boron, it is possible to obtain a back surface conductive film 5 having wear resistance and chemical resistance. When the back surface conductive film 5 contains tantalum (Ta) and boron (B), the B content is preferably 5 to 30 atomic %. The ratio of Ta and B (Ta:B) in the sputtering target used for depositing the back surface conductive film 5 is preferably 95:5 to 70:30.

[0138] The thickness of the back surface conductive film 5 is not particularly limited as long as it satisfies the function for electrostatic chuck. The thickness of the back surface conductive film 5 is usually 10 nm to 200 nm. The back surface conductive film 5 also functions to adjust the stress on the second main surface side of the mask blank 100, and is adjusted to obtain a flat reflective mask blank 100 by balancing with the stress from various films formed on the first main surface side.

[0139] <Reflection mask 200 and its manufacturing method> This embodiment is a reflective mask 200 having a phase shift pattern 4a obtained by patterning the phase shift film 4 of the above-mentioned reflective mask blank 100. The phase shift pattern 4a can be formed by patterning the phase shift film 4 of the above-mentioned reflective mask blank 100 with a predetermined dry etching gas (e.g., a dry etching gas containing a chlorine-based gas and an oxygen gas). The phase shift pattern 4a of the reflective mask 200 can absorb EUV light and reflect a part of the EUV light with a predetermined phase difference (e.g., 180 degrees) from an opening (a portion where the phase shift pattern is not formed). In order to pattern the phase shift film 4, an etching mask film may be provided on the phase shift film 4 as necessary, and the phase shift film 4 may be dry-etched using the etching mask film pattern as a mask to form the phase shift pattern 4a.

[0140] A method for manufacturing a reflective mask 200 using the reflective mask blank 100 of this embodiment will be described below. Only an outline will be given here, and a detailed description will be given later in examples with reference to the drawings.

[0141] A reflective mask blank 100 is prepared, and a resist film 11 is formed on the phase shift film 4 on the first main surface thereof (not necessary if the reflective mask blank 100 is provided with the resist film 11). A desired pattern is drawn (exposed) on this resist film 11, which is then developed and rinsed to form a predetermined resist pattern 11a.

[0142] In the case of the reflective mask blank 100, the phase shift film 4 (upper layer 42 and lower layer 41) are etched using a predetermined etching gas with this resist pattern 11a as a mask to form the phase shift pattern 4a, and the resist pattern 11a is removed by ashing, a resist stripper, or the like to form the phase shift pattern 4a. Finally, wet cleaning is performed using an acidic or alkaline aqueous solution.

[0143] Here, as for the etching gas for the phase shift film 4 (upper layer 42 and lower layer 41), it is necessary to select an appropriate etching gas according to the materials used, as described above. By appropriately selecting the materials of the phase shift film 4 (upper layer 42 and lower layer 41) and the protective film 3, and the corresponding etching gas, it is possible to prevent the surface of the protective film 3 from becoming rough when the phase shift film 4 is etched.

[0144] Through the above steps, a reflective mask 200 is obtained that has a highly accurate fine pattern with little shadowing effect and little sidewall roughness.

[0145] <Method of Manufacturing Semiconductor Device> The present embodiment is a method for manufacturing a semiconductor device. A semiconductor device can be manufactured by setting the reflective mask 200 of the present embodiment in an exposure tool having an exposure light source of EUV light and transferring a transfer pattern to a resist film formed on a transfer substrate.

[0146] Specifically, by performing EUV exposure using the reflective mask 200 of the present embodiment, a desired transfer pattern based on the phase shift pattern 4a on the reflective mask 200 can be formed on a semiconductor substrate while suppressing deterioration of transfer dimensional accuracy due to the shadowing effect. In addition, since the phase shift pattern 4a is a fine and highly accurate pattern with little sidewall roughness, a desired pattern can be formed on a semiconductor substrate with high dimensional accuracy. In addition to this lithography process, various processes such as etching of the processed film, formation of an insulating film and a conductive film, introduction of a dopant, and annealing can be performed to manufacture a semiconductor device having a desired electronic circuit formed thereon.

[0147] More specifically, the EUV exposure tool is composed of a laser plasma light source that generates EUV light, an illumination optical system, a mask stage system, a reduction projection optical system, a wafer stage system, and a vacuum facility. The light source is equipped with a debris trap function, a cut filter that cuts out long-wavelength light other than the exposure light, and a vacuum differential pumping facility. The illumination optical system and the reduction projection optical system are composed of reflective mirrors. The EUV exposure reflective mask 200 is electrostatically attracted by the back conductive film 5 formed on its second main surface and placed on the mask stage.

[0148] The light from the EUV light source is irradiated onto the reflective mask 200 at an angle of 6 to 8 degrees with respect to the vertical plane of the reflective mask 200 via an illumination optical system. The light reflected from the reflective mask 200 in response to this incident light is reflected (specularly reflected) in the opposite direction to the incident direction and at the same angle as the incident angle, and is guided to a reflective projection optical system having a reduction ratio of usually 1 / 4, and exposure is performed on the resist on the wafer (semiconductor substrate) placed on the wafer stage. During this time, at least the area through which the EUV light passes is evacuated to a vacuum. In addition, for this exposure, the mask stage and the wafer stage are scanned in synchronization at a speed according to the reduction ratio of the reduction projection optical system, and exposure is performed through a slit, which is a mainstream scanning exposure method. By developing this exposed resist film, a resist pattern can be formed on the semiconductor substrate. In this embodiment, a mask is used that is a thin film with a small shadowing effect and has a highly accurate phase shift pattern with little sidewall roughness. Therefore, the resist pattern formed on the semiconductor substrate has a desired high dimensional accuracy. By performing etching or the like using this resist pattern as a mask, a predetermined wiring pattern can be formed on the semiconductor substrate, for example. A semiconductor device is manufactured through such exposure steps, a process for processing the film to be processed, a process for forming an insulating film or a conductive film, a dopant introduction step, an annealing step, and other necessary steps.

[0149] According to the method for manufacturing a semiconductor device of this embodiment, the thickness of the phase shift film 4 can be reduced, the shadowing effect can be reduced, and the reflective mask 200 capable of forming a fine and highly accurate phase shift pattern 4a with a stable cross-sectional shape with little sidewall roughness can be used for manufacturing a semiconductor device. Therefore, a semiconductor device having a fine and highly accurate transfer pattern can be manufactured. EXAMPLES

[0150] Hereinafter, examples will be described with reference to the drawings. The present invention is not limited to these examples. In the examples, the same components are designated by the same reference numerals, and the description will be simplified or omitted.

[0151] [Example 1] FIG. 2 is a schematic cross-sectional view of a main part showing a process for producing a reflective mask 200 from a reflective mask blank 100. As shown in FIG.

[0152] The reflective mask blank 100 has a back surface conductive film 5, a substrate 1, a multilayer reflective film 2, a protective film 3, and a phase shift film 4. The phase shift film 4 of Example 1 has a lower layer 41 (first layer) of a TaN film and an upper layer 42 of a RuCr film (second layer). Then, as shown in FIG. 2(a), a resist film 11 is formed on the phase shift film 4.

[0153] First, a reflective mask blank 100 according to the first embodiment will be described.

[0154] A SiO2-TiO2-based glass substrate, which is a low-thermal expansion glass substrate having a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) with both the first and second main surfaces polished, was prepared as substrate 1. In order to obtain a flat and smooth main surface, polishing was performed through a rough polishing process, a precision polishing process, a localized polishing process, and a touch polishing process.

[0155] A back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the SiO2-TiO2 based glass substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. Conditions for forming the back surface conductive film 5: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0156] Next, a multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 opposite to the side on which the back conductive film 5 was formed. The multilayer reflective film 2 formed on the substrate 1 was a periodic multilayer reflective film made of Mo and Si in order to make the multilayer reflective film 2 suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 2 was formed by alternately laminating Mo layers and Si layers on the substrate 1 by ion beam sputtering in an Ar gas atmosphere using a Mo target and a Si target. First, a Si film was formed with a thickness of 4.2 nm, and then a Mo film was formed with a thickness of 2.8 nm. This was set as one cycle, and 40 cycles were similarly laminated, and finally a Si film was formed with a thickness of 4.0 nm to form the multilayer reflective film 2. Here, 40 cycles were used, but this is not limited thereto, and for example, 60 cycles may be used. In the case of 60 cycles, the number of steps increases compared to 40 cycles, but the reflectance for EUV light can be increased.

[0157] Subsequently, in an Ar gas atmosphere, a protective film 3 made of a Ru film was formed to a thickness of 2.5 nm by ion beam sputtering using a Ru target.

[0158] Next, a first layer made of a TaN film was formed as the lower layer 41 of the phase shift film 4 by DC magnetron sputtering. The TaN film was formed to a thickness of 15.5 nm by reactive sputtering in a N2 gas atmosphere using a Ta target. The content ratio (atomic ratio) of the TaN film was Ta:N=88:12. When the crystal structure of the TaN film was measured by an X-ray diffraction device (XRD), it was found that the TaN film had an amorphous structure.

[0159] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the TaN film of Example 1 formed as described above at a wavelength of 13.5 nm were as follows. TaN film: n=0.949, k=0.032

[0160] Next, a second layer made of a RuCr film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The RuCr film was formed to a thickness of 22.8 nm in an Ar gas atmosphere using a RuCr target. The content ratio (atomic ratio) of the RuCr film was Ru:Cr=90:10. When the crystal structure of the RuCr film was measured by an X-ray diffraction device (XRD), the RuCr film had an amorphous structure.

[0161] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCr film of Example 1 formed as described above at a wavelength of 13.5 nm were as follows. RuCr film: n=0.890, k=0.019

[0162] The relative reflectance of the phase shift film 4 made of the TaN film and the RuCr film at a wavelength of 13.5 nm was 20.1%. The total thickness of the phase shift film 4 was 38.3 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 41% thinner than the thickness of the phase shift film 4 made of a TaN film, 65 nm, in Comparative Example 1 described later.

[0163] Next, a reflective mask 200 was manufactured using the reflective mask blank 100 described above.

[0164] A resist film 11 was formed to a thickness of 100 nm on the phase shift film 4 of the reflective mask blank 100 (FIG. 2(a)). A desired pattern was then drawn (exposed) on this resist film 11, which was then developed and rinsed to form a predetermined resist pattern 11a (FIG. 2(b)).

[0165] Next, using the resist pattern 11a as a mask, the RuCr film (upper layer 42) was dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1) to form an upper layer pattern 42a (Figure 2(c)).

[0166] Next, using the resist pattern 11a and the upper layer pattern 42a as a mask, the TaN film (lower layer 41) was dry-etched using a halogen-based gas to form a lower layer pattern 41a (FIG. 2(d)). Specifically, the oxide film on the surface of the TaN film was dry-etched using CF4 gas, and then the TaN film was dry-etched using Cl2 gas.

[0167] Thereafter, the resist pattern 11a was removed by ashing, using a resist stripper, etc. Finally, wet cleaning was performed using deionized water (DIW) to manufacture the reflective mask 200 of Example 2 (FIG. 2(e)). If necessary, a mask defect inspection can be performed after the wet cleaning, and mask defect correction can be performed as appropriate.

[0168] In the reflective mask 200 of Example 1, the phase shift film 4 is a TaN film and a RuCr film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 38.3 nm, which is thinner than the absorber film formed of a conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0169] In addition, the reflective mask 200 produced in Example 1 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface (reflectance with respect to the reflectance of the surface of the multilayer reflective film 2 with the protective film 3) was 20.1%, so that a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0170] The reflective mask 200 produced in Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which a film to be processed and a resist film were formed on a semiconductor substrate. The exposed resist film was then developed to form a resist pattern on the semiconductor substrate on which the film to be processed was formed. This resist pattern was transferred to the film to be processed by etching, and various processes such as the formation of an insulating film and a conductive film, the introduction of a dopant, and annealing were performed to manufacture a semiconductor device having desired characteristics.

[0171] [Example 2] Example 2 is an example in which a phase shift film 4 is formed by using a lower layer 41 of a CrOC film (first layer) and an upper layer 42 of a RuNi film (second layer), and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0172] That is, in Example 2, similarly to Example 1, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of a SiO2-TiO2-based glass substrate 1, a multilayer reflective film 2 was formed on the main surface (first main surface) of the opposite substrate 1, and a protective film 3 made of a Ru film was formed on the surface of the multilayer reflective film 2.

[0173] Next, a first layer made of a CrOC film was formed as the lower layer 41 of the phase shift film 4 by DC magnetron sputtering. The CrOC film was formed to a thickness of 13.8 nm by reactive sputtering using a Cr target and a mixed gas of Ar gas, CO2 gas, and He gas. The content ratio (atomic ratio) of the CrOC film was Cr:O:C=70:15:15. When the crystal structure of the CrOC film was measured by an X-ray diffraction device (XRD), it was found that the CrOC film had an amorphous structure.

[0174] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the CrOC film of Example 2 formed as described above at a wavelength of 13.5 nm were as follows. CrOC film: n=0.941, k=0.031

[0175] Next, a second layer made of a RuNi film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The RuNi film was formed to a thickness of 23.5 nm in an Ar gas atmosphere using a RuNi target. The content ratio (atomic ratio) of the RuNi film was Ru:Ni=90:10. When the crystal structure of the RuNi film was measured by an X-ray diffraction device (XRD), the RuNi film had an amorphous structure.

[0176] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuNi film of Example 2 formed as described above at a wavelength of 13.5 nm were as follows. RuNi film: n=0.891, k=0.022

[0177] The relative reflectance of the phase shift film 4 made of the CrOC film and the RuNi film at a wavelength of 13.5 nm was 20.2%. The total thickness of the phase shift film 4 was 37.3 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 43% thinner than the thickness of the phase shift film 4 made of a TaN film in Comparative Example 1 described later, which was 65 nm.

[0178] Next, in the same manner as in Example 1, the reflective mask 200 of Example 2 was manufactured using the reflective mask blank 100 described above.

[0179] As in Example 1, a resist film 11 was formed to a thickness of 100 nm on the phase shift film 4 of the reflective mask blank 100 (FIG. 2(a)). A desired pattern was then drawn (exposed) on this resist film 11, which was then developed and rinsed to form a predetermined resist pattern 11a (FIG. 2(b)).

[0180] Next, the RuNi film (upper layer 42) was dry-etched using O 2 gas with the resist pattern 11a as a mask to form an upper layer pattern 42a (FIG. 2(c)).

[0181] Next, using the resist pattern 11a and the upper layer pattern 42a as a mask, the CrOC film (lower layer 41) was dry-etched using Cl2 gas to form a lower layer pattern 41a (FIG. 2(d)).

[0182] Thereafter, the resist pattern 11a was removed and cleaning was performed in the same manner as in Example 1, thereby producing a reflective mask 200 of Example 2 (FIG. 2(e)).

[0183] In the reflective mask 200 of Example 2, the phase shift film 4 is a CrOC film and a RuNi film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 37.3 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0184] In addition, the reflective mask 200 produced in Example 2 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 20.2%, so that a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0185] As in the case of the first embodiment, the reflective mask 200 produced in the second embodiment was used to manufacture a semiconductor device having desired characteristics.

[0186] [Example 3] Example 3 is an example in which a SiO2 film is used as the protective film 3, a lower layer 41 of a RuCo film (second layer) and an upper layer 42 of a TaN film (first layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0187] That is, in Example 3, similarly to Example 1, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of a SiO2-TiO2-based glass substrate 1, and a multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 on the opposite side.

[0188] Subsequently, a protective film 3 made of a SiO2 film was formed on the surface of the multilayer reflective film 2 to a thickness of 2.5 nm by RF sputtering using a SiO2 target in an Ar gas atmosphere.

[0189] Next, a second layer made of a RuCo film was formed as the lower layer 41 of the phase shift film 4 by DC magnetron sputtering. The RuCo film was formed to a thickness of 23.2 nm in an Ar gas atmosphere using a RuCo target. The content ratio (atomic ratio) of the RuCo film was Ru:Co=90:10. When the crystal structure of the RuCo film was measured by an X-ray diffraction device (XRD), the RuCo film had an amorphous structure.

[0190] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCo film of Example 3 formed as described above at a wavelength of 13.5 nm were as follows: RuCo film: n=0.890, k=0.021

[0191] Next, a first layer made of a TaN film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The TaN film was formed to a thickness of 13.9 nm by reactive sputtering in a N2 gas atmosphere using a Ta target. The content ratio (atomic ratio) of the TaN film was Ta:N=88:12. When the crystal structure of the TaN film was measured by an X-ray diffraction device (XRD), it was found that the TaN film had an amorphous structure.

[0192] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the TaN film of Example 3 formed as described above at a wavelength of 13.5 nm were as follows. TaN film: n=0.949, k=0.032

[0193] The relative reflectance of the phase shift film 4 made of the RuCo film and the TaN film at a wavelength of 13.5 nm was 19.9%. The total thickness of the phase shift film 4 was 37.1 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 43% thinner than the thickness of the phase shift film 4 made of a TaN film, 65 nm, in Comparative Example 1 described later.

[0194] Next, in the same manner as in Example 1, the reflective mask blank 100 was used to manufacture a reflective mask 200 of Example 3.

[0195] As in Example 1, a resist film 11 was formed to a thickness of 100 nm on the phase shift film 4 of the reflective mask blank 100 (FIG. 2(a)). A desired pattern was then drawn (exposed) on this resist film 11, which was then developed and rinsed to form a predetermined resist pattern 11a (FIG. 2(b)).

[0196] Next, using the resist pattern 11a as a mask, the TaN film (upper layer 42) was dry-etched using a halogen-based gas to form an upper layer pattern 42a (FIG. 2(c)). Specifically, the oxide film on the surface of the TaN film was dry-etched using CF4 gas, and then the TaN film was dry-etched using Cl2 gas.

[0197] Next, using the resist pattern 11a and the upper layer pattern 42a as masks, the RuCo film (lower layer 41) was dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1) to form a lower layer pattern 41a (Figure 2(d)).

[0198] Thereafter, the resist pattern 11a was removed and cleaning was performed in the same manner as in Example 1, thereby producing a reflective mask 200 of Example 3 (FIG. 2(e)).

[0199] In the reflective mask 200 of Example 3, the phase shift film 4 is a TaN film and a RuCo film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 37.1 nm, which is thinner than the absorber film formed of a conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0200] In addition, the reflective mask 200 produced in Example 3 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 19.9%, so a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0201] As in the case of the first embodiment, the reflective mask 200 produced in the third embodiment was used to manufacture a semiconductor device having desired characteristics.

[0202] [Example 4] Example 4 is an example in which a lower layer 41 of a RuCr film (second layer) and an upper layer 42 of a CrOC film (first layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 3.

[0203] That is, in Example 4, similarly to Example 3, a back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the SiO2-TiO2-based glass substrate 1, and a multilayer reflective film 2 and a protective film 3 made of a SiO2 film were formed on the main surface (first main surface) of the substrate 1 on the opposite side.

[0204] Next, a second layer made of a RuCr film was formed as the lower layer 41 of the phase shift film 4 by DC magnetron sputtering. The RuCr film was formed to a thickness of 22.2 nm in an Ar gas atmosphere using a RuCr target. The content ratio (atomic ratio) of the RuCr film was Ru:Cr=90:10. When the crystal structure of the RuCr film was measured by an X-ray diffraction device (XRD), the RuCr film had an amorphous structure.

[0205] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCr film of Example 4 formed as described above at a wavelength of 13.5 nm were as follows. RuCr film: n=0.890, k=0.019

[0206] Next, a first layer made of a CrOC film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The CrOC film was formed to a thickness of 15.4 nm by reactive sputtering using a Cr target and a mixed gas of Ar gas, CO2 gas, and He gas. The content ratio (atomic ratio) of the CrOC film was Cr:O:C=70:15:15. When the crystal structure of the CrOC film was measured by an X-ray diffraction device (XRD), it was found that the CrOC film had an amorphous structure.

[0207] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the CrOC film of Example 4 formed as described above at a wavelength of 13.5 nm were as follows. CrOC film: n=0.941, k=0.031

[0208] The relative reflectance of the phase shift film 4 made of the RuCr film and the CrOC film at a wavelength of 13.5 nm was 20.2%. The total thickness of the phase shift film 4 was 37.6 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 42% thinner than the thickness of the phase shift film 4 made of a TaN film in Comparative Example 1 described later, which was 65 nm.

[0209] Next, in the same manner as in Example 1, the reflective mask blank 100 was used to manufacture a reflective mask 200 of Example 4.

[0210] As in Example 1, a resist film 11 was formed to a thickness of 100 nm on the phase shift film 4 of the reflective mask blank 100 (FIG. 2(a)). A desired pattern was then drawn (exposed) on this resist film 11, which was then developed and rinsed to form a predetermined resist pattern 11a (FIG. 2(b)).

[0211] Next, using the resist pattern 11a as a mask, the CrOC film (upper layer 42) was dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1) to form an upper layer pattern 42a (Figure 2(c)).

[0212] Subsequently, the RuCr film (lower layer 41) was dry-etched using the same mixed gas (mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1)) as that for the CrOC film (upper layer 42) to form a lower layer pattern 41a (FIG. 2(d)). The dry etching of the upper layer 42 and the lower layer 41 were performed continuously.

[0213] Thereafter, the resist pattern 11a was removed and cleaning was performed in the same manner as in Example 1, thereby producing a reflective mask 200 of Example 4 (FIG. 2(e)).

[0214] In the reflective mask 200 of Example 4, the phase shift film 4 is a CrOC film and a RuCr film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, since both the CrOC film and the RuCr film can be continuously etched using the same etching gas, the productivity is high. In addition, the total film thickness of the phase shift pattern 4a is 37.6 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0215] In addition, the reflective mask 200 produced in Example 4 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 20.2%, so that a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0216] As in the case of the first embodiment, the reflective mask 200 produced in the fourth embodiment was used to manufacture a semiconductor device having desired characteristics.

[0217] [Example 5] Example 5 is an example in which a RuNb film is used as the protective film 3, a lower layer 41 of a TaN film (first layer) and an upper layer 42 of a RuNb film (second layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0218] That is, in Example 5, a protective film 3 made of a RuNb film was formed on the surface of a multilayer reflective film 2 similar to that in Example 1. The RuNb film was formed to a thickness of 2.5 nm in an Ar gas atmosphere using a RuNb target. The content ratio (atomic ratio) of the RuNb film was Ru:Nb=80:20.

[0219] Next, a first layer made of a TaN film was formed on the RuNb film as the lower layer 41 of the phase shift film 4. The TaN film was formed to a thickness of 16.5 nm by the same film formation method as in Example 1. The refractive index n and extinction coefficient k of the TaN film at a wavelength of 13.5 nm were the same as in Example 1.

[0220] Thereafter, a second layer made of a RuNb film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The RuNb film was formed to a thickness of 22.9 nm in an Ar gas atmosphere using a RuNb target. The content ratio (atomic ratio) of the RuNb film was Ru:Nb=80:20. When the crystal structure of the RuNb film was measured by an X-ray diffraction device (XRD), the RuNb film had an amorphous structure.

[0221] The refractive index n and extinction coefficient k at a wavelength of 13.5 nm of the RuNb film of Example 5 formed as described above were as follows. RuNb film: n=0.897, k=0.014

[0222] The relative reflectance of the phase shift film 4 at a wavelength of 13.5 nm was 19.6% (absolute reflectance was 13.1%). The total thickness of the phase shift film 4 was 39.4 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 39% thinner than the thickness of 65 nm of the phase shift film 4 made of a TaN film in Comparative Example 1 described later.

[0223] Next, the reflective mask 200 of Example 5 was manufactured using the reflective mask blank 100 in the same manner as in Example 1. The RuNb film was dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1). The TaN film was dry etched using CF4 gas to remove the oxide film on the surface, and then dry etched using Cl2 gas.

[0224] In the reflective mask 200 of Example 5, the phase shift film 4 is a TaN film and a RuNb film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 39.4 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0225] In addition, the reflective mask 200 produced in Example 5 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 19.6% (absolute reflectance was 13.1%), so a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0226] As in the case of the first embodiment, the reflective mask 200 produced in the fifth embodiment was used to manufacture a semiconductor device having desired characteristics.

[0227] [Example 6] Example 6 is an example in which a RuNb film is used as the protective film 3, a lower layer 41 of a CrOC film (first layer) and an upper layer 42 of a RuV film (second layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0228] That is, in the sixth embodiment, a protective film 3 made of a RuNb film similar to that in the fifth embodiment was formed on the surface of a multilayer reflective film 2 similar to that in the first embodiment.

[0229] Next, a first layer made of a CrOC film was formed on the RuNb film as the lower layer 41 of the phase shift film 4. The CrOC film was formed to a thickness of 14.7 nm by the same film formation method as in Example 2. The refractive index n and extinction coefficient k of the CrOC film at a wavelength of 13.5 nm were the same as in Example 2.

[0230] Thereafter, a second layer made of a RuV film was formed as the upper layer 42 of the phase shift film 4 by DC magnetron sputtering. The RuV film was formed to a thickness of 24 nm in an Ar gas atmosphere using a RuV target. The content ratio (atomic ratio) of the RuV film was Ru:V=70:30. When the crystal structure of the RuV film was measured by an X-ray diffraction device (XRD), the RuV film was found to have an amorphous structure.

[0231] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuV film of Example 6 formed as described above at a wavelength of 13.5 nm were as follows. RuV film: n=0.903, k=0.020

[0232] The relative reflectance of the phase shift film 4 at a wavelength of 13.5 nm was 20.1% (absolute reflectance was 13.4%). The total thickness of the phase shift film 4 was 38.7 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 40% thinner than the thickness of 65 nm of the phase shift film 4 made of a TaN film in Comparative Example 1 described later.

[0233] Next, the reflective mask 200 of Example 6 was manufactured using the reflective mask blank 100 in the same manner as in Example 1. The RuV film was dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1). The CrOC film was dry etched using Cl2 gas.

[0234] In the reflective mask 200 of Example 6, the phase shift film 4 is a CrOC film and a RuV film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 38.7 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0235] In addition, the reflective mask 200 produced in Example 6 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 20.1% (absolute reflectance was 13.4%), so a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0236] As in the case of the first embodiment, the reflective mask 200 produced in the sixth embodiment was used to manufacture a semiconductor device having desired characteristics.

[0237] [Example 7] Example 7 is an example in which a SiO2 film is used as the protective film 3, a lower layer 41 of a RuV film (second layer) and an upper layer 42 of a TaN film (first layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0238] That is, in Example 7, a protective film 3 made of a SiO 2 film similar to that in Example 3 was formed on the surface of a multilayer reflective film 2 similar to that in Example 1.

[0239] Next, a second layer made of a RuV film was formed on the SiO2 film as the lower layer 41 of the phase shift film 4. The RuV film was formed to a thickness of 29 nm by the same film formation method as in Example 6. The refractive index n and extinction coefficient k of the RuV film at a wavelength of 13.5 nm were the same as in Example 6.

[0240] Thereafter, a second layer made of a TaN film was formed as the upper layer 42 of the phase shift film 4. The TaN film was formed to a thickness of 9.2 nm by the same film formation method as in Example 1. The refractive index n and extinction coefficient k of the TaN film at a wavelength of 13.5 nm were the same as in Example 1.

[0241] The relative reflectance of the phase shift film 4 at a wavelength of 13.5 nm was 19.9% ​​(absolute reflectance was 13.3%). The total thickness of the phase shift film 4 was 33.2 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 49% thinner than the thickness of 65 nm of the phase shift film 4 made of a TaN film in Comparative Example 1 described later.

[0242] Next, the reflective mask 200 of Example 7 was manufactured using the reflective mask blank 100 in the same manner as in Example 1. The TaN film was dry-etched by using CF4 gas to dry-etch the oxide film on the surface, and then dry-etched using Cl2 gas. The RuV film was dry-etched using a mixture gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1).

[0243] In the reflective mask 200 of Example 7, the phase shift film 4 is a RuV film and a TaN film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 39.4 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0244] In addition, the reflective mask 200 produced in Example 7 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 19.9% ​​(absolute reflectance was 13.3%), so a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0245] As in the case of the first embodiment, the reflective mask 200 produced in the seventh embodiment was used to manufacture a semiconductor device having desired characteristics.

[0246] [Example 8] Example 8 is an example in which a SiO2 film is used as the protective film 3, a lower layer 41 of a RuNb film (second layer) and an upper layer 42 of a CrOC film (first layer) are used as the phase shift film 4, and the film thicknesses are adjusted to provide a phase difference of 180 degrees, and the rest is the same as Example 1.

[0247] That is, in Example 8, a protective film 3 made of a SiO 2 film similar to that in Example 3 was formed on the surface of a multilayer reflective film 2 similar to that in Example 1.

[0248] Next, a second layer made of a RuNb film was formed on the SiO2 film as the lower layer 41 of the phase shift film 4. The RuNb film was formed to a thickness of 18.3 nm by the same film formation method as in Example 5. The refractive index n and extinction coefficient k of the RuNb film at a wavelength of 13.5 nm were the same as in Example 5.

[0249] Thereafter, a second layer made of a CrOC film was formed as the upper layer 42 of the phase shift film 4. The CrOC film was formed to a thickness of 20.7 nm by the same film formation method as in Example 1. The refractive index n and extinction coefficient k of the CrOC film at a wavelength of 13.5 nm were the same as in Example 2.

[0250] The relative reflectance of the phase shift film 4 at a wavelength of 13.5 nm was 19.7% (absolute reflectance was 13.1%). The total thickness of the phase shift film 4 was 39 nm. This thickness corresponds to a phase difference of 180 degrees when the phase shift film 4 is patterned. This was about 40% thinner than the thickness of 65 nm of the phase shift film 4 made of a TaN film in Comparative Example 1 described later.

[0251] Next, in the same manner as in Example 1, a reflective mask 200 of Example 8 was manufactured using the reflective mask blank 100. The CrOC film and the RuNb film were dry etched using a mixed gas of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1).

[0252] In the reflective mask 200 of Example 8, the phase shift film 4 is a RuNb film and a CrOC film, so that the processability by dry etching using a predetermined etching gas is good, and the phase shift pattern 4a can be formed with high accuracy. In addition, the total film thickness of the phase shift pattern 4a is 39 nm, which is thinner than the absorber film formed of the conventional Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0253] In addition, the reflective mask 200 produced in Example 8 had low sidewall roughness of the phase shift pattern 4a and a stable cross-sectional shape, so that the LER and in-plane dimensional variation of the transferred resist pattern were small, and the mask had high transfer accuracy. In addition, as described above, the relative reflectance of the phase shift surface was 19.7% (absolute reflectance was 13.1%), so a sufficient phase shift effect was obtained, and EUV exposure with high exposure tolerance and focus tolerance was possible.

[0254] As in the case of the first embodiment, the reflective mask 200 produced in the eighth embodiment was used to manufacture a semiconductor device having desired characteristics.

[0255] [Comparative Example 1] In comparative example 1, a reflective mask blank 100 and a reflective mask 200 were manufactured with the same structure and method as in example 1, except that a single layer TaN film was used as the phase shift film 4, and a semiconductor device was manufactured with the same method as in example 1.

[0256] A single-layer TaN film (phase shift film 4) was formed on the protective film 3 of the mask blank structure of Example 1. The TaN film was formed by reactive sputtering in a mixed gas atmosphere of Xe gas and N2 gas using Ta as a target. The thickness of the TaN film was 65 nm, and the element ratio of this film was 88 atomic % Ta and 12 atomic % N.

[0257] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the TaN film formed as described above at a wavelength of 13.5 nm were as follows, respectively. TaN film: n=0.949, k=0.032

[0258] The phase difference of the phase shift film 4 made of the single-layer TaN film at a wavelength of 13.5 nm is 180 degrees. The reflectance of the two surfaces of the multilayer reflective film is 1.7%.

[0259] Thereafter, in the same manner as in Example 1, a resist film 11 was formed on the phase shift film 4 made of a single layer of TaN film, and a desired pattern was drawn (exposed), developed, and rinsed to form a resist pattern 11a. Then, using this resist pattern 11a as a mask, the phase shift film 4 made of a single layer of TaN film was dry-etched using chlorine gas to form a phase shift pattern 4a. Removal of the resist pattern 11a and mask cleaning were also performed in the same manner as in Example 1 to manufacture a reflective mask 200.

[0260] The thickness of the phase shift pattern 4a was 65 nm, and the shadowing effect could not be reduced. In addition, as described above, the relative reflectance of the phase shift surface (reflectance to the reflectance of the multilayer reflective film surface with a protective film) was 1.7%, so that a sufficient phase shift effect could not be obtained and EUV exposure with high exposure tolerance and focus tolerance could not be performed.

[0261] As described above, the total thickness of phase shift film 4 in Examples 1 to 8 was approximately 40% or more thinner than the 65 nm thickness of phase shift film 4 in Comparative Example 1. Therefore, it was clear that the shadowing effect could be reduced in reflective masks 200 in Examples 1 to 8. [Explanation of symbols]

[0262] 1 Board 2 Multilayer reflective film 3 Protective film 4 Phase shift film 4a Phase shift pattern 41 Lower layer 41a Lower Pattern 42 Upper layer 42a Upper layer pattern 5 Backside conductive film 11 Resist film 11a Resist pattern 100 Reflective mask blank 200 Reflective mask

Claims

1. A reflective mask blank having a multilayer reflective film and a phase-shifting film that shifts the phase of EUV light on a substrate in this order, The phase-shift film has a first layer and a second layer, The first layer is positioned on the side where the multilayer reflective film exists, The first layer contains at least one element selected from tantalum (Ta) and chromium (Cr), The second layer comprises ruthenium (Ru) and at least one of the following elements: chromium (Cr), nickel (Ni), vanadium (V), and tungsten (W). The thickness of the first layer is 2 to 16.5 nm. The thickness of the second layer is 22.8 to 50 nm. A reflective mask blank characterized in that the thickness of the phase-shift film is 25 to 60 nm.

2. The second layer comprises ruthenium (Ru) and chromium (Cr), The reflective mask blank according to claim 1, characterized in that the composition range (atomic ratio) of Ru and Cr is Ru:Cr = 40:1 to 1:

20.

3. The second layer comprises ruthenium (Ru) and nickel (Ni), The reflective mask blank according to claim 1, characterized in that the composition range (atomic ratio) of Ru and Ni is Ru:Ni = 40:1 to 1:

6.

4. The second layer comprises ruthenium (Ru) and vanadium (V), The reflective mask blank according to claim 1, characterized in that the composition range (atomic ratio) of Ru and V is Ru:V = 40:1 to 1:

20.

5. The second layer comprises ruthenium (Ru) and tungsten (W), The reflective mask blank according to claim 1, characterized in that the composition range (atomic ratio) of Ru and W is Ru:W = 40:1 to 1:

20.

6. The reflective mask blank according to any one of claims 1 to 5, characterized in that the second layer further comprises at least one selected from nitrogen (N), oxygen (O), carbon (C), and boron (B).

7. The reflective mask blank according to claim 6, characterized in that the nitrogen (N) content is 1 atomic% or more and 10 atomic% or less.

8. A protective film is further provided between the multilayer reflective film and the first layer. The reflective mask blank according to any one of claims 1 to 7, characterized in that the protective film contains ruthenium (Ru).

9. The reflective mask blank according to any one of claims 1 to 8, characterized in that the relative reflectance of the phase-shift film is 10% or more.

10. The reflective mask blank according to any one of claims 1 to 9, characterized in that the phase difference of the phase shift film is 130 degrees to 160 degrees, or 200 degrees to 230 degrees.

11. A reflective mask characterized in that the phase-shift film in the reflective mask blank according to any one of claims 1 to 10 has a patterned phase-shift pattern.

12. A method for manufacturing a semiconductor device, characterized by comprising the steps of setting a reflective mask according to claim 11 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a substrate to be transferred.

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