Method for manufacturing a reflective photomask substrate, a reflective photomask, and a reflective photomask and a semiconductor device.

Abstract

This invention provides a reflective photomask substrate that further reduces the shadowing effect of reflective photomasks and can form fine and high-precision phase-shifting patterns. The present invention is a reflective photomask substrate characterized by having, sequentially, multiple reflective films and phase-shifting films that shift the phase of EUV light on a substrate, wherein the phase-shifting films have a thin film containing a metal, the metal containing at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), cobalt (Co), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), germanium (Ge), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re).

Description

Technical Field

[0001] This invention relates to a primary image of an exposure mask, namely a reflective mask substrate, used in the manufacture of semiconductor devices, a method for manufacturing the reflective mask and the same, and a method for manufacturing semiconductor devices. Prior Technology

[0002] In semiconductor device manufacturing, the types of light sources used in exposure equipment, such as g-lines with a wavelength of 436 nm, i-lines with a wavelength of 365 nm, KrF lasers with a wavelength of 248 nm, and ArF lasers with a wavelength of 193 nm, are constantly evolving with increasingly shorter wavelengths. To achieve finer pattern transfer, EUV lithography, using extreme ultraviolet (EUV) light with a wavelength around 13.5 nm, has been developed. In EUV lithography, since there are fewer materials transparent to EUV light, reflective photomasks are used. The basic structure of this reflective photomask involves forming a multilayer reflective film on a low thermal expansion substrate that reflects the exposure light, and then forming the desired transfer pattern on a protective film that protects the multilayer reflective film. Regarding the composition of the transfer pattern, representative examples include binary reflective photomasks and phase-shifted reflective photomasks (halftone phase-shifted reflective photomasks). The binary reflective mask has a relatively thick absorber pattern that effectively absorbs EUV light. The phase-shifted reflective mask has a relatively thin absorber pattern (phase-shifted pattern) that reduces EUV light through light absorption and produces reflected light that is approximately 180 degrees phase-reversed relative to the reflected light from the multilayer reflective film. Like the transmissive phase-shifted mask, this phase-shifted reflective mask achieves higher contrast in the transferred optical image through the phase-shifting effect, thus improving resolution. Furthermore, because the absorber pattern (phase-shifted pattern) of the phase-shifted reflective mask is thinner, it can form a precise and finely detailed phase-shifted pattern.

[0003] In EUV lithography, a projection optics system comprising multiple mirrors is used due to the need for high light transmittance. Furthermore, for reflective photomasks, EUV light is incident at an oblique angle so that the multiple mirrors do not block the projection light (exposure light). Currently, the mainstream method sets the incident angle to 6 degrees relative to the vertical plane of the reflective photomask substrate. Research has been conducted on a more oblique incident angle of approximately 8 degrees, which is possible as the numerical aperture (NA) of the projection optics system increases.

[0004] In EUV lithography, the exposed light is incident at an oblique angle, thus creating an inherent problem known as the shadow effect. The shadow effect refers to the phenomenon where the exposed light, incident at an oblique angle onto the three-dimensional absorber pattern, creates shadows, resulting in changes in the size or position of the transferred pattern. The three-dimensional structure of the absorber pattern acts as a wall, creating shadows on the shaded side, causing changes in the size or position of the transferred pattern. For example, when the orientation of the absorbed pattern is parallel to or perpendicular to the direction of the obliquely incident light, differences in the size and position of the transferred pattern occur, reducing transfer accuracy.

[0005] The reflective photomask used in EUV lithography and the related technology for fabricating it are disclosed in Patent Documents 1 to 3. Furthermore, Patent Document 1 also discloses the shading effect. By using a phase-shifted reflective photomask as the reflective photomask for EUV lithography, the film thickness of the phase-shifted pattern is relatively thinner than the film thickness of the absorber pattern in the binary reflective photomask, thereby suppressing the reduction in transfer accuracy caused by the shading effect.

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2010-080659 [Patent Document 2] Japanese Patent Application Publication No. 2004-207593 [Patent Document 3] Japanese Patent Application Publication No. 2009-206287 Summary of the Invention

[0007] The finer the pattern, and the higher the precision of the pattern size or position, the better the electrical characteristics and performance of the semiconductor device, and the greater the integration density or the smaller the wafer size. Therefore, EUV lithography requires higher precision micro-pattern transfer performance than before. Currently, there is a need to address the formation of ultra-fine, high-precision patterns using hp16 nm (half-pitch 16 nm). To meet this need, in order to reduce shading effects, the thickness of the absorber film (phase-shifting film) needs to be thinner. Especially in EUV exposure, the thickness of the absorber film (phase-shifting film) needs to be set to less than 60 nm, preferably less than 50 nm.

[0008] As disclosed in Patent Documents 1 to 3, Ta has been used as a material for forming absorber films (phase-shifting films) of reflective photomask substrates since the past. However, the refractive index n of Ta in EUV light (e.g., wavelength 13.5 nm) is approximately 0.943. Therefore, even utilizing the phase-shifting effect of Ta, the lower limit of the thickness of absorber films (phase-shifting films) formed solely by Ta is limited to 60 nm. To make the film thickness thinner, for example, a metal material with a lower refractive index n (a larger phase-shifting effect) can be used. As a metal material with a lower refractive index n at a wavelength of 13.5 nm, as illustrated in Figure 7 of Patent Document 1, there are Mo (n=0.921) and Ru (n=0.887). However, Mo is very easily oxidized and its cleaning resistance is questionable, while Ru has a lower etching rate and is more difficult to process or correct.

[0009] In view of the above aspects, the present invention aims to provide a reflective photomask substrate that further reduces the shadowing effect of reflective photomasks and can form fine and high-precision phase shift patterns, a reflective photomask made thereon, and a method for manufacturing a semiconductor device.

[0010] To solve the above problems, the present invention has the following structure.

[0011] (Component 1) The present invention comprises a reflective photomask substrate, characterized in that: it has a series of reflective films and a phase shifting film for shifting the phase of EUV light sequentially on the substrate, and the phase shifting film has a thin film containing a metal, wherein the metal contains at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), cobalt (Co), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), germanium (Ge), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re).

[0012] According to configuration 1 of the present invention, a phase-shifting film with a thinner film thickness than the reflected light from the opening of the reflective photomask pattern, which requires a specific phase difference, can be obtained. Therefore, in a reflective photomask, the shading effect caused by the phase-shifting pattern can be further reduced. Furthermore, according to configuration 1 of the present invention, a phase-shifting film with a higher relative reflectivity (the relative reflectivity when the EUV light reflected from the portion without the phase-shifting pattern is set to 100%) can be obtained. As a result, by using a reflective photomask substrate manufactured with configuration 1 of the present invention, the yield rate in manufacturing semiconductor devices can be increased.

[0013] (Component 2) The present invention, configuration 2, is the same as the reflective photomask substrate of configuration 1, characterized in that the crystalline structure of the phase shift film is amorphous.

[0014] According to configuration 2 of the present invention, by making the crystalline structure of the material constituting the phase shift film amorphous, the adverse effects caused by crystalline particles such as metals when forming the phase shift pattern can be reduced.

[0015] (Component 3) The present invention comprises 3 as described in 1 or 2, which is a reflective photomask substrate, characterized in that the phase shift film is a thin film containing a metal, wherein the metal contains at least one of the elements selected from ruthenium (Ru), chromium (Cr), nickel (Ni) and cobalt (Co).

[0016] According to configuration 3 of the present invention, the etching rate of the dry etching gas during the patterning of the phase shift film can be accelerated, thereby reducing the thickness of the resist film and which is beneficial for the formation of fine patterns in the phase shift film.

[0017] (Component 4) The present invention comprises a reflective photomask substrate as described in configuration 3, characterized in that the composition ratio of Ru to Cr (Ru:Cr) is 15:1 to 1:20.

[0018] According to configuration 4 of the present invention, by using Cr, which can be etched with the same etching gas as Ru, and the composition ratio of Ru to Cr is within a specific range, a phase shift film with good processing characteristics and a specific phase difference can be obtained at a relatively thin film thickness.

[0019] (Component 5) The present invention comprises a reflective photomask substrate as described in configuration 5, wherein the composition ratio of Ru to Ni (Ru:Ni) is 20:1 to 1:4.

[0020] According to configuration 5 of the present invention, by using Ni, which has a large extinction coefficient, as the metal used with Ru, and by having the composition ratio of Ru to Ni within a specific range, a phase shifting film that can obtain a specific phase difference with a higher reflectivity at a thinner film thickness can be obtained.

[0021] (Composition 6) The present invention comprises a reflective photomask substrate of configuration 6 as described in configuration 3, characterized in that the composition ratio (Ru:Co) of Ru to Co is 20:1 to 1:5.

[0022] According to the configuration 6 of the present invention, by using Co, which has a large extinction coefficient, as the metal used with Ru, and by having the composition ratio of Ru to Co within a specific range, a phase shifting film that can obtain a specific phase difference with a higher reflectivity at a thinner film thickness can be obtained.

[0023] (Component 7) The present invention comprises a reflective photomask substrate as described in any one of 1 to 6, characterized in that a protective film is further provided between the multilayer reflective film and the phase shift film, the protective film comprising a material containing silicon (Si) and oxygen (O).

[0024] According to configuration 7 of the present invention, by forming a protective film on the multilayer reflective film, damage to the surface of the multilayer reflective film during the manufacture of a reflective photomask (EUV photomask) using a substrate with a multilayer reflective film can be suppressed, thus improving the reflectivity characteristics for EUV light. Since the protective film contains materials containing silicon (Si) and oxygen (O), it is resistant to the dry etching gas used to pattern the phase shift film, therefore the protective film will not be etched, and damage to the protective film can be suppressed.

[0025] (Composition 8) The present invention comprises a reflective photomask, characterized in that it has a phase shift pattern formed by patterning the phase shift film in the reflective photomask substrate as described in any one of the embodiments 1 to 7.

[0026] According to configuration 8 of the present invention, the phase shift pattern of the reflective photomask can absorb EUV light, and also reflects a portion of EUV light with a specific phase difference from the opening (the part where the phase shift pattern is not formed). Therefore, by patterning the phase shift film of the reflective photomask substrate, the reflective photomask (EUV photomask) of the present invention can be manufactured.

[0027] (Composition 9) The present invention comprises a method for manufacturing a reflective photomask, characterized in that: the phase shift film of the reflective photomask substrate as described in any one of the embodiments 1 to 7 is patterned by using a dry etching gas containing chlorine gas and oxygen to form a phase shift pattern.

[0028] According to configuration 9 of the present invention, a reflective photomask can be manufactured such that the phase shift film thickness can be reduced, the shadowing effect can be reduced, and a fine and high-precision phase shift pattern can be formed with a stable cross-sectional shape with less sidewall roughness.

[0029] (Composition 10) The present invention, configuration 10, is a method for manufacturing a semiconductor device, characterized by the following steps: setting a reflective photomask as in configuration 8 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern onto a resist film formed on a substrate to be transferred.

[0030] According to the manufacturing method of the semiconductor device comprising 10 of the present invention, a reflective photomask can be used to manufacture the semiconductor device. This reflective photomask can reduce the thickness of the phase shift film, reduce the shading effect, and form a fine and high-precision phase shift pattern with a stable cross-sectional shape and less sidewall roughness. Therefore, a semiconductor device with a fine and high-precision transfer pattern can be manufactured.

[0031] According to the reflective photomask substrate of the present invention (the reflective photomask fabricated therefrom), the phase shift film thickness can be reduced, shading effects can be decreased, and fine and high-precision phase shift patterns can be formed with a stable cross-sectional shape and less sidewall roughness. Therefore, the reflective photomask fabricated using the reflective photomask substrate with this structure can form the phase shift pattern itself on the photomask with fine and high precision, and can prevent the reduction in accuracy during transfer caused by shading. Furthermore, by using the reflective photomask for EUV lithography, a method for manufacturing fine and high-precision semiconductor devices can be provided. Simple Explanation of the Diagram

[0032] Figure 1 is a schematic cross-sectional view of the main parts of the reflective photomask substrate of the present invention. Figures 2(a) to (d) are schematic diagrams showing the steps of fabricating a reflective photomask from a reflective photomask substrate, using cross-sectional views of the main parts. Figure 3 shows the relationship between the thickness of the phase shift film and the relative reflectivity and phase difference of light with a wavelength of 13.5 nm. Implementation

[0033] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Furthermore, the following embodiments are one embodiment of the present invention and are not intended to limit the invention to its scope. Also, in the drawings, there are instances where the same or equivalent parts are given the same symbol and their descriptions are simplified or omitted.

[0034] <Composition and Manufacturing Method of Reflective Photomask Substrate 100> Figure 1 is a schematic cross-sectional view illustrating the main components of the reflective photomask substrate 100 of this embodiment. As shown in Figure 1, the reflective photomask substrate 100 includes a photomask substrate 1 (also simply referred to as "substrate 1"), a multilayer reflective film 2, a protective film 3, and a phase shift film 4, which are sequentially stacked. The multilayer reflective film 2 reflects the EUV light exposed on the first main surface (front side). The protective film 3 is provided to protect the multilayer reflective film 2 and is formed of a material resistant to the etchant and cleaning solution used when patterning the phase shift film 4. The phase shift film 4 absorbs EUV light. Furthermore, a back conductive film 5 for electrostatic chucks is formed on the second main surface (back side) of the substrate 1.

[0035] In this specification, the phrase "having a multilayer reflective film 2 on the main surface of the photomask substrate 1" means not only that the multilayer reflective film 2 is disposed in contact with the front surface of the photomask substrate 1, but also that there are other films between the photomask substrate 1 and the multilayer reflective film 2. The same applies to other films. For example, the phrase "having a film B on film A" means not only that film A and film B are disposed in direct contact, but also that there are other films between film A and film B. Furthermore, in this specification, for example, the phrase "disposed with the surfaces of film A and film B in contact" means that film A and film B are disposed in direct contact without any other films separating them.

[0036] In this specification, the term "phase shift film 4" refers to, for example, "a thin film comprising a material containing a metal, wherein the metal comprises ruthenium (Ru) and chromium (Cr)," meaning that the phase shift film 4 is a thin film that at least substantially comprises a material containing ruthenium (Ru) and chromium (Cr). On the other hand, the term "phase shift film 4" means "a thin film containing ruthenium (Ru) and chromium (Cr)," implying that the phase shift film 4 is composed solely of ruthenium (Ru) and chromium (Cr). Furthermore, in either case, there is an unavoidable inclusion of impurities within the phase shift film 4.

[0037] The following is a description of each layer.

[0038] <<Substrate 1>> To prevent deformation of the phase shift pattern 4a caused by heat during EUV light exposure, the substrate 1 is preferably made of a material with a low coefficient of thermal expansion in the range of 0 ± 5 ppb / ℃. Materials with this low coefficient of thermal expansion include, for example, SiO2-TiO2 based glass and multi-component glass-ceramics.

[0039] From the viewpoint of achieving at least pattern transfer accuracy and positional accuracy, the first main surface of the substrate 1 on the side where the transfer pattern (the phase offset film 4 described below constitutes the transfer pattern) is surface-processed to achieve high flatness. In the case of EUV exposure, the flatness of the 132 mm × 132 mm area of ​​the main surface of the substrate 1 on the side where the transfer pattern is formed is preferably 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less. Furthermore, the second main surface on the opposite side of the side where the transfer pattern is formed is the surface that is electrostatically attracted during exposure; in the 132 mm × 132 mm area, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and even more preferably 0.03 μm or less. Furthermore, regarding the flatness of the second principal surface side of the reflective photomask substrate 100, in a region of 142 mm × 142 mm, the flatness is preferably less than 1 μm, more preferably less than 0.5 μm, and even more preferably less than 0.3 μm.

[0040] Furthermore, the surface smoothness of substrate 1 is also an extremely important factor. The surface roughness of the first main surface of substrate 1, which is used to form the phase shift pattern 4a for transfer, is preferably less than 0.1 nm in terms of root mean square roughness (RMS). Moreover, the surface smoothness can be measured using atomic force microscopy.

[0041] Furthermore, in order to prevent deformation caused by the film stress of the film (such as the multilayer reflective film 2) formed thereon, the substrate 1 preferably has high rigidity. It is especially preferred to have a high Young's modulus of 65 GPa or higher.

[0042] <<Multilayer Reflective Coating 2>> The multilayer reflective film 2 is used in the reflective photomask 200 to give it the function of reflecting EUV light, and it is a multilayer film formed by periodically stacking layers of elements with different refractive indices as the main components.

[0043] Generally, a multilayer reflective film 2 is formed by alternately depositing thin films of light elements or their compounds as high-refractive-index materials (high-refractive-index layers) and thin films of heavy elements or their compounds as low-refractive-index materials (low-refractive-index layers) for about 40 to 60 cycles. Alternatively, the multilayer film can be constructed by sequentially depositing high-refractive-index layers and low-refractive-index layers from the substrate 1 side, forming a high-refractive-index layer / low-refractive-index layer stacking structure as one cycle, and then stacking multiple cycles. Furthermore, the multilayer film can also be constructed by sequentially depositing low-refractive-index layers and high-refractive-index layers from the substrate 1 side, forming a low-refractive-index layer / high-refractive-index layer stacking structure as one cycle, and then stacking multiple cycles. Moreover, the outermost layer of the multilayer reflective film 2, i.e., the surface layer on the side of the multilayer reflective film 2 opposite to the substrate 1, is preferably a high-refractive-index layer. In the aforementioned multilayer film, when the stacking structure of a high-refractive-index layer and a low-refractive-index layer, formed by sequentially stacking a high-refractive-index layer and a low-refractive-index layer from the substrate 1, is considered as one cycle and multiple cycles are stacked, the uppermost layer becomes a low-refractive-index layer. In this case, if the low-refractive-index layer forms the outermost surface of the multilayer reflective film 2, it is prone to oxidation, and the reflectivity of the reflective photomask 200 decreases. Therefore, it is preferable to form a high-refractive-index layer on the uppermost low-refractive-index layer to fabricate the multilayer reflective film 2. On the other hand, in the aforementioned multilayer film, when the stacking structure of a low-refractive-index layer and a high-refractive-index layer, formed by sequentially stacking a low-refractive-index layer and a high-refractive-index layer from the substrate 1 side, is considered as one cycle and multiple cycles are stacked, the uppermost layer becomes a high-refractive-index layer, so it is preferable to keep this condition unchanged.

[0044] In this embodiment, a silicon (Si) layer is used as the high refractive index layer. Besides elemental Si, Si compounds containing boron (B), carbon (C), nitrogen (N), and oxygen (O) can also be used as the Si-containing material. By using a Si-containing layer as the high refractive index layer, an EUV lithography reflective mask 200 with excellent EUV light reflectivity can be obtained. Furthermore, in this embodiment, a glass substrate is preferably used as the substrate 1. Si also exhibits excellent adhesion to the glass substrate. As the low refractive index layer, a single metal component selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or alloys thereof, is used. For example, as the multilayer reflective film 2 for EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic laminated film formed by alternating layers of Mo and Si films for approximately 40 to 60 cycles is preferred. Furthermore, the uppermost layer of the multilayer reflective film 2, namely the high refractive index layer, can also be formed from silicon (Si).

[0045] The reflectivity of this type of multilayer reflective film 2 is typically above 65%, with an upper limit of 73%. Furthermore, the thickness and period of each constituent layer of the multilayer reflective film 2 can be appropriately selected according to the exposure wavelength, in a manner that satisfies the Bourgue reflection law. In the multilayer reflective film 2, multiple high-refractive-index layers and multiple low-refractive-index layers exist, but the thicknesses of the high-refractive-index layers and the low-refractive-index layers can also be different. Moreover, the thickness of the outermost Si layer of the multilayer reflective film 2 can be adjusted within a range without reducing reflectivity. The thickness of the outermost Si (high-refractive-index layer) can be set from 3 nm to 10 nm.

[0046] The method for forming the multilayer reflective film 2 is known in the art. For example, it can be formed by depositing each layer of the multilayer reflective film 2 using an ion beam sputtering method. In the case of the above-mentioned Mo / Si periodic multilayer film, for example, by ion beam sputtering, a Si film with a thickness of about 4 nm is first deposited on a substrate 1 using a Si target. Then, a Mo film with a thickness of about 3 nm is deposited using a Mo target. The Si film / Mo film is deposited as one period, and 40 to 60 periods are accumulated to form the multilayer reflective film 2 (the outermost layer is set as the Si layer). Furthermore, when forming the multilayer reflective film 2, it is preferable to supply krypton (Kr) ion particles from an ion source and perform ion beam sputtering to form the multilayer reflective film 2.

[0047] <<Protective Film 3>> To protect the multilayer reflective film 2 from the dry etching and cleaning processes during the manufacturing of the reflective photomask 200, a protective film 3 can be formed on or in contact with the surface of the multilayer reflective film 2. This also protects the multilayer reflective film 2 during the correction of black spot defects using the phase shift pattern 4a with an electron beam (EB). Figure 1 shows a single-layer protective film 3, but it can also be a multilayer structure with three or more layers. The protective film 3 is formed of a material resistant to the etchant and 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 during the manufacturing of the reflective photomask 200 (EUV photomask) using a substrate with the multilayer reflective film can be suppressed. Therefore, the reflectivity characteristics of the multilayer reflective film 2 for EUV light become excellent.

[0048] The following explanation will use the case where the protective film 3 and the phase shifting film 4 each consist of one layer as an example. Furthermore, when the protective film 3 comprises multiple layers, the material properties of the uppermost layer of the protective film 3 (the layer in contact with the phase shifting film 4) are crucial in its relationship with the phase shifting film 4. Similarly, when the phase shifting film 4 comprises multiple layers, the material properties of the lowermost layer of the phase shifting film 4 (the layer in contact with the protective film 3) are crucial in its relationship with the uppermost layer of the protective film 3.

[0049] In the reflective photomask substrate 100 of this embodiment, the material of the protective film 3 can be selected to be a material that is resistant to the etching gas used in the dry etching process for patterning the phase shift film 4 formed on the protective film 3.

[0050] For example, when the phase shift film 4 in contact with the surface of the protective film 3 is a thin film containing a metal (a specific Ru-based material), and the metal contains at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), cobalt (Co), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), germanium (Ge), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re), the material of the protective film 3 can be selected from silicon-based materials such as silicon (Si), materials containing silicon (Si) and oxygen (O), materials containing silicon (Si) and nitrogen (N), and chromium (Cr), or chromium-based materials containing chromium (Cr), oxygen (O), nitrogen (N), and carbon (C).

[0051] For example, when the phase shift film 4 in contact with the surface of the protective layer 3 is a thin film containing a metal (specifically a Ru-based material), and the metal contains at least one element selected from ruthenium (Ru), aluminum (Al), silicon (Si), titanium (Ti), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re), a fluorine-based gas can be used as the dry etching gas for patterning the phase shift film 4, and the aforementioned chromium-based material can be selected as the material of the protective film 3.

[0052] For example, when the phase shift film 4 in contact with the surface of the protective layer 3 is a thin film containing a metal (specifically a Ru-based material), and the metal contains at least one element selected from ruthenium (Ru), aluminum (Al), silicon (Si), titanium (Ti), germanium (Ge), tin (Sn), and hafnium (Hf), a fluorine-based gas or an oxygen-free chlorine-based gas can be used as the dry etching gas for patterning the phase shift film 4. In this case, the aforementioned silicon-based material and the aforementioned chromium-based material can be selected as the material for the protective layer 3.

[0053] For example, when the phase shift film 4, which is in contact with the surface of the protective film 3, is a thin film containing a metal (specifically a Ru-based material), and the metal contains at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), and cobalt (Co), or contains at least one element selected from ruthenium (Ru), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re), an oxygen-containing chlorine-based gas can be used as the dry etching gas for patterning the phase shift film 4. In this case, silicon-based materials such as silicon (Si), materials containing silicon (Si) and oxygen (O), or materials containing silicon (Si) and nitrogen (N) can be selected as the material of the protective film 3. Furthermore, when the phase shift film 4 comprises multiple layers, if the layer of the phase shift film 4 in contact with the surface of the protective film 3 is a thin film other than a specific Ru-based material, the material of the protective film 3 can be selected according to the etching characteristics of the material.

[0054] The protective film 3 of the reflective photomask substrate 100 in this embodiment is preferably a material containing silicon (Si) or containing both silicon (Si) and oxygen (O) (silicon-based materials). The phase shift film 4, containing a metal containing at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), and cobalt (Co) (specific Ru-based materials), and a metal containing at least one element selected from ruthenium (Ru), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re) (specific ruthenium (Ru)-based materials), can be dry-etched using chlorine-based gases or oxygen. Silicon-based materials, such as silicon (Si), materials containing both silicon (Si) and oxygen (O), or materials containing both silicon (Si) and nitrogen (N), are resistant to these dry etching gases; the higher the oxygen content, the greater the resistance. Therefore, the material of the protective film 3 is preferably silicon oxide (SiOx, 1≦x≦2), and even more preferably the one with a larger x, especially SiO2.

[0055] In EUV lithography, there are few substances that are transparent to the exposed light, making the EUV photomask protective film, which prevents foreign matter from adhering to the patterned surface of the photomask, technically challenging. Due to this, the use of a photomask without a protective film has become mainstream. Furthermore, in EUV lithography, exposure contamination such as carbon film deposition or oxide film growth occurs due to EUV exposure. Therefore, in the stage of using EUV reflective photomasks in the manufacture of semiconductor devices, repeated cleaning is required to remove foreign matter or contamination from the photomask. Thus, EUV reflective photomasks require a significantly different level of cleaning tolerance compared to transmissive photomasks used in photolithography. By incorporating a protective film 3 into the reflective photomask 200, the cleaning tolerance to cleaning solutions can be improved.

[0056] The thickness of the protective film 3 is not particularly limited as long as it can achieve the function of protecting the multilayer reflective film 2. From the viewpoint of EUV light reflectivity, the thickness of the protective film 3 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm.

[0057] As for the method of forming the protective film 3, there are no particular restrictions on using the same known film forming methods. For specific examples, sputtering and ion beam sputtering can be cited.

[0058] <<Phase Shifting Film 4>> A phase offset film 4 having a phase offset that causes the EUV light is formed on top of the protective film 3 . In the portion formed with phase offset film 4 (phase offset pattern 4a ), a portion of the light is reflected to the extent that it absorbs EUV light and subtracts light and has no adverse effect on pattern transfer. On the other hand, in the opening (the part without phase offset film 4 ), EUV light is reflected from the multilayer reflective film 2 through the protective film 3 . The reflected light from the part forming the film with a phase offset 4 forms the desired phase difference with the reflected light from the opening. The phase offset film 4 is formed in such a way that the phase difference between the reflected light from the phase offset film 4 and the reflected light from the multilayer reflected film 2 becomes 160 to 200 degrees. Lights with phase difference resorting to the inversion near 180 degrees interfere with each other at the edge part of the pattern, and the image contrast of the projected optical image is improved. Along with the improvement of the resolution of its image contrast, the exposure margin, and the focal margin and other various margins regarding exposure expand. It also varies according to the pattern or exposure conditions, but in general, the standard for the reflectance of the phase offset film 4 used to obtain that phase offset effect is 2% or more in terms of relative reflectivity. In order to obtain an adequate phase offset effect, the reflectance of the phase offset film 4 is preferably more than 6% with the relative reflectivity. Also, in cases where the relative reflectivity is higher, above 10%, and more preferably above 15%, in order to further improve the contrast, the phase difference can also be set to 130 degrees to 160 degrees, or 200 degrees to 230 degrees. Here, the relative reflectivity of the phase offset film 4 (phase offset pattern 4a ) refers to the EUV light reflected by the self-multilayer reflective film 2 (the multilayer reflective film 2 containing the protective film 3 attached to it) reflected by the self-multilayer reflective film 2 in the part without the phase offset pattern 4a as the reflectance of the EUV light reflected by the self-phase offset pattern 4a at a reflectivity of 100%. Furthermore, in this instruction book, relative reflectance is sometimes referred to as “reflectivity.”

[0059] Also, in order to obtain an adequate phase offset effect, the absolute reflectivity of the phase offset film 4 is better than 9%. Here, the absolute reflectivity of phase offset film 4 (phase offset pattern 4a ) refers to the reflectance (ratio of incident light intensity to reflected light intensity) of EUV light reflected by self phase offset film 4 (or phase offset pattern 4a ).

[0060] In order to understand the further improvement of imageability and the improvement of output when manufacturing semiconductor devices, the relative reflectivity of phase offset pattern 4a is better at 6%~40%. demand its better to be 6~35%, then better to be 15%~35%, and then better to be 15%~25%.

[0061] In order to understand the further improvement of imageability and the improvement of output when fabricating semiconductor devices, the absolute reflectivity of phase offset film 4 (or phase offset pattern 4a ) is more ideally 4%~27% and more preferably 10%~17%.

[0062] The phase shift film 4 of this embodiment has a thin film containing a metal, which contains at least one element selected from ruthenium (Ru), chromium (Cr), nickel (Ni), cobalt (Co), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), germanium (Ge), niobium (Nb), molybdenum (Mo), tin (Sn), tellurium (Te), hafnium (Hf), tungsten (W), and rhenium (Re).

[0063] The phase shift film 4 of the reflective photomask substrate 100 of this embodiment, by using a specific material, can obtain a phase shift pattern 4a with a relative reflectivity of 6% to 40%. The phase shift film 4 of the reflective photomask substrate 100 of this embodiment, by using a specific material, can achieve an absolute reflectivity of 4% to 27%. Furthermore, the phase shift film 4 of the reflective photomask substrate 100 of this embodiment has a thinner film thickness required to obtain a specific phase difference (the phase difference between the reflected light from the opening and the reflected light from the phase shift pattern 4a). Therefore, in the reflective photomask 200, the shading effect caused by the phase shift pattern 4a can be further reduced. Moreover, by using the reflective photomask 200 manufactured from the reflective photomask substrate 100 of this embodiment, the yield rate in the manufacture of semiconductor devices can be increased.

[0064] The material of the phase shift film 4 of the reflective photomask substrate 100 in this embodiment (hereinafter, sometimes simply referred to as "specific Ru-based material") will be further described.

[0065] In this embodiment, the phase shift film 4 of the reflective photomask substrate 100 preferably has an amorphous crystal structure.

[0066] Ru has a refractive index n = 0.886 (extinction coefficient k = 0.017), making it a favorable material for the high-reflectivity phase-shifting film 4. However, Ru-based compounds such as RuO tend to crystallize, resulting in poor processing characteristics. Specifically, the sidewall roughness of the crystallized metal particles tends to increase when forming the phase-shifting pattern 4a. Therefore, there are instances where this can have adverse effects when forming a specific phase-shifting pattern 4a. On the other hand, when the crystalline structure of the phase-shifting film 4 is amorphous, the adverse effects of forming the phase-shifting pattern 4a can be reduced. By adding a specific element (X) to Ru, the crystalline structure of the phase-shifting film 4 can be made amorphous, and the etching rate can be accelerated, the pattern shape can be improved, or the processing characteristics can be enhanced. The specific element (X) can be at least one of Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re.

[0067] Furthermore, Ni has a refractive index n = 0.948 and an extinction coefficient k = 0.073. Co has n = 0.933 and k = 0.066, and Cr has n = 0.932 and k = 0.039. Binary materials (RuCr, RuNi, and RuCo) with specific elements (X) added to Ru can achieve a thinner phase-shifting film 4 compared to RuTa, which was previously used as the material. Also, Ni and Co have larger extinction coefficients k than Cr; therefore, choosing Ni and / or Co as element (X) compared to choosing Cr results in a thinner phase-shifting film 4.

[0068] Furthermore, the refractive index n and extinction coefficient k of Al are n=1.003 and k=0.03, respectively; the refractive index n and extinction coefficient k of Si are n=0.999 and k=0.002, respectively; the refractive index n and extinction coefficient k of Ti are n=0.952 and k=0.014, respectively; the refractive index n and extinction coefficient k of V are n=0.944 and k=0.025, respectively; the refractive index n and extinction coefficient k of Ge are n=0.995 and k=0.032, respectively; and the refractive index n and extinction coefficient k of Nb are n=0.933 and k=0.005, respectively. The refractive index n and extinction coefficient k of Mo are n=0.923 and k=0.007, respectively; the refractive index n and extinction coefficient k of Sn are n=0.941 and k=0.074, respectively; the refractive index n and extinction coefficient k of Te are n=0.973 and k=0.075, respectively; the refractive index n and extinction coefficient k of Hf are n=0.961 and k=0.035, respectively; the refractive index n and extinction coefficient k of W are n=0.933 and k=0.033, respectively; and the refractive index n and extinction coefficient k of Re are n=0.914 and k=0.04, respectively.

[0069] Furthermore, Sn, Te, and Re have larger extinction coefficients k compared to Cr. Therefore, choosing Sn, Te, and Re as elements (X) compared to choosing Cr can result in a thinner phase-shifting film 4.

[0070] Furthermore, the refractive index n and extinction coefficient k range for the phase shifting film 4 when the phase difference is 160 degrees to 200 degrees are as follows. When the relative reflectance of the phase shifting film 4 is 6% to 40% or the absolute reflectance is 4% to 27%, the refractive index n of the material containing the specific element (X) added to Ru for 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 6% to 35% or the absolute reflectance is 4% to 23%, the refractive index n of the material containing the specific element (X) added to Ru for EUV light is preferably 0.880 to 0.950, and the extinction coefficient k is preferably 0.012 to 0.095. When the relative reflectance is 15%~35% or the absolute reflectance is 10%~23%, the refractive index n of the material with the addition of a specific element (X) to Ru is preferably 0.880~0.950 and the extinction coefficient k is preferably 0.012~0.050 for EUV light. When the relative reflectance is 15%~25% or the absolute reflectance is 10%~17%, the refractive index n of the material with the addition of a specific element (X) to Ru is preferably 0.890~0.950 and the extinction coefficient k is preferably 0.020~0.050 for EUV light.

[0071] Furthermore, the refractive index n and extinction coefficient k range for the phase shift film 4 when the phase difference is 130 degrees to 160 degrees 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 material with the added specific element (X) to Ru for EUV light is preferably 0.860 to 0.950, and the extinction coefficient k is preferably 0.009 to 0.095. When the relative reflectance is 15% to 35% or the absolute reflectance is 10% to 23%, the refractive index n of the material with the added specific element (X) to Ru for EUV light is preferably 0.860 to 0.950, and the extinction coefficient k is preferably 0.01 to 0.073.

[0072] Furthermore, the refractive index n and extinction coefficient k range for the phase shifting film 4 when the phase difference is 200 to 230 degrees are as follows. When the relative reflectance of the phase shifting film 4 is 10% to 40% or the absolute reflectance is 6.7% to 27%, the refractive index n of the material with the added specific element (X) to Ru for 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 material with the added specific element (X) to Ru for EUV light is preferably 0.860 to 0.939, and the extinction coefficient k is preferably 0.009 to 0.045.

[0073] The phase difference and reflectivity of the phase-shifting film 4 can be adjusted by changing the refractive index n, extinction coefficient k, and film thickness. The film thickness of the phase-shifting film 4 is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. The film thickness of the phase-shifting film 4 is preferably 25 nm or more. Furthermore, when a protective film 3 is present, the phase difference and reflectivity of the phase-shifting film 4 can also be adjusted by considering the refractive index n, extinction coefficient k, and film thickness of the protective film 3.

[0074] Binary materials (RuCr, RuNi, and RuCo) containing specific elements (X) exhibit better processing characteristics compared to the previously used RuTa material. If Ta is oxidized, it is difficult to etch with chlorine-based gases and oxygen. In particular, RuCr demonstrates excellent processing characteristics.

[0075] Binary materials (RuCr, RuNi, and RuCo) containing a specific element (X) are amorphous and can be easily etched using a mixture of chlorine and oxygen gases. These materials can also be etched using oxygen. The same applies to ternary materials (RuCrNi, RuCrCo, and RuNiCo) and quaternary materials (RuCrNiCo).

[0076] Furthermore, in addition to the aforementioned binary materials, binary materials of Ru containing V, Nb, Mo, W, or Re (RuV, RuNb, RuMo, RuW, and RuRe) exhibit better processability compared to RuTa, which was previously used as a material. Similar to RuCr, RuW and RuMo show particularly superior processability.

[0077] Furthermore, binary materials (RuV, RuNb, RuMo, RuW, and RuRe) containing specific elements (X) are amorphous and can be easily etched using a mixture of chlorine and oxygen gases. These materials can also be etched using oxygen. The same applies to ternary and quaternary materials.

[0078] Secondly, regarding the material of the phase shift film 4 in this embodiment, namely a specific Ru-based material, the mixing ratio of Ru and a specific element (X) is explained.

[0079] The higher the Ru content, the higher the relative and absolute reflectivity of a specific Ru-based material. Furthermore, the reflected light from the phase-shifting film 4 is an overlap of the front-reflected light from the front of the phase-shifting film 4 and the back-reflected light passing through the phase-shifting film 4 and appearing on the back side of the phase-shifting film 4 (the interface between the phase-shifting film 4 and the protective film 3 or the multilayer reflective film 2). Therefore, the intensity of the reflected light from the phase-shifting film 4 has a periodic structure dependent on the film thickness. As a result, as shown in an example in Figure 3, the reflectivity and phase difference of the phase-shifting film 4 also exhibit a periodic structure dependent on the film thickness. Moreover, Figure 3 shows the relationship between the film thickness of the phase-shifting film 4 (which is a RuCr film with an atomic ratio of Ru:Cr = 56:44) and the relative reflectivity and phase difference of EUV light. The refractive index n and extinction coefficient k of the phase-shifting film 4 material affect this periodic structure. On the other hand, the reflected light from the phase-shifting pattern 4a needs to have a specific phase difference (e.g., a phase difference of 180 degrees) relative to the reflected light from the opening. Considering the above, a study was conducted on the relationship between the relative reflectivity of the phase-shifting film 4, the specific Ru-based material composition, and the film thickness. The results show that, as described below, a better range can be achieved for the specific Ru-based material composition and film thickness based on the relative reflectivity of the phase-shifting film 4. As shown in Figure 3, when the phase-shifting film 4 is formed from a RuCr film (Ru:Cr=56:44), the film thickness is 32.6 nm, the relative reflectivity relative to the multilayer reflective film (with a protective film) is 20%, and the phase difference is approximately 180 degrees. Furthermore, in the above description, the relative reflectivity of the phase-shifting film 4 can be referred to as the absolute reflectivity. In Figure 3, when the phase-shifting film 4 is formed from a RuCr film (Ru:Cr=56:44), the film thickness is 32.6 nm, the absolute reflectivity is 13.3%, and the phase difference is approximately 180 degrees.

[0080] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Cr, the composition ratio of Ru to Cr (Ru:Cr) is preferably 15:1 to 1:20.

[0081] Specifically, when the phase-shifting film 4 contains Ru and Cr, the relationship between the relative reflectance, absolute reflectance, specific Ru-based material composition (atomic ratio), and film thickness of the phase-shifting film 4 is as follows: That is, when the relative reflectance of the phase-shifting film 4 is 6% or more (absolute reflectance 4% or more), with the Ru atomic ratio set to 1, Cr is 20 or less, and the film thickness is 50 nm or less. When the relative reflectance of the phase-shifting film 4 is 15% or more (absolute reflectance 10% or more), with the Ru atomic ratio set to 1, Cr is 4 or less, and the film thickness is 45 nm or less. When the relative reflectance of the phase-shifting film 4 is 25% or less (absolute reflectance 17% or less), with the Cr atomic ratio set to 1, Ru is 5 or less, and the film thickness is 30 nm or more. When the relative reflectivity of the phase-shifted film 4 is less than 40% (absolute reflectivity less than 27%), and the atomic ratio of Cr is set to 1, the Ru is less than 15, and the film thickness is more than 25 nm.

[0082] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Ni, the composition ratio of Ru to Ni (Ru:Ni) is preferably 20:1 to 1:4.

[0083] Specifically, when the phase-shifting film 4 contains Ru and Ni, the relationship between the relative reflectivity, absolute reflectivity, specific Ru-based material composition (atomic ratio), and film thickness of the phase-shifting film 4 is as follows: That is, when the relative reflectivity of the phase-shifting film 4 is 6% or higher (absolute reflectivity 4% or higher), with the Ru atomic ratio set to 1, Ni is 4 or lower, and the film thickness is 45 nm or lower. When the relative reflectivity of the phase-shifting film 4 is 15% or higher (absolute reflectivity 10% or higher), with the Ru atomic ratio set to 1, Ni is 1 or lower, and the film thickness is 45 nm or lower. When the relative reflectivity of the phase-shifting film 4 is 25% or lower (absolute reflectivity 17% or lower), with the Ni atomic ratio set to 1, Ru is 10 or lower, and the film thickness is 30 nm or higher. When the relative reflectivity of the phase-shifted film 4 is less than 40% (absolute reflectivity less than 27%), the atomic ratio of Ni is set to 1, Ru is less than 20, and the film thickness is more than 25 nm.

[0084] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Co, the composition ratio of Ru to Co (Ru:Co) is preferably 20:1 to 1:5.

[0085] Specifically, when the phase-shifting film 4 contains Ru and Co, the relationship between the relative reflectivity, absolute reflectivity, specific Ru-based material composition (atomic ratio), and film thickness of the phase-shifting film 4 is as follows: That is, when the relative reflectivity of the phase-shifting film 4 is 6% or higher (absolute reflectivity 4% or higher), with the Ru atomic ratio set to 1, Co is 5 or lower, and the film thickness is 40 nm or lower. When the relative reflectivity of the phase-shifting film 4 is 15% or higher (absolute reflectivity 10% or higher), with the Ru atomic ratio set to 1, Co is 1.5 or lower, and the film thickness is 40 nm or lower. When the relative reflectivity of the phase-shifting film 4 is 25% or lower (absolute reflectivity 17% or lower), with the Co atomic ratio set to 1, Ru is 10 or lower, and the film thickness is 30 nm or higher. When the relative reflectivity of the phase-shifted film 4 is less than 40% (absolute reflectivity less than 27%), and the atomic ratio of Co is set to 1, the Ru is less than 20, and the film thickness is more than 25 nm.

[0086] As described above, by using a specific range of the composition (atomic ratio) of Ru, Cr, Ni and Co, a phase shift film 4 with higher reflectivity and a specific phase difference can be obtained with a thinner film thickness.

[0087] Furthermore, the relationship between the relative reflectivity, absolute reflectivity, specific Ru-based material composition (atomic ratio), and film thickness of the phase shifting film 4 in the cases containing Ru and Al, Ru and Si, Ru and Ti, Ru and V, Ru and Ge, Ru and Nb, Ru and Mo, Ru and Sn, Ru and Te, Ru and Hf, Ru and W, and Ru and Re is as follows.

[0088] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Al, the composition ratio of Ru to Al (Ru:Al) is preferably 20:1 to 4:5.

[0089] When the relative reflectivity of the phase-shifting film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 4, the Al content is 5 or less, and the film thickness is 67 nm or less. When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 13, the Al content is 7 or less, and the film thickness is 50 nm or less. When the relative reflectivity of the phase-shifting film 4 is 25% or less (absolute reflectivity 17% or less), with the Al atomic ratio set to 1, the Ru content is 4 or less, and the film thickness is 36 nm or more. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), with the Al atomic ratio set to 1, the Ru content is 20 or less, and the film thickness is 30 nm or more.

[0090] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Si, the composition ratio of Ru to Si (Ru:Si) is preferably 20:1 to 1:1.

[0091] When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), the atomic ratio of Ru is set to 1, the Si content is 1 or less, and the film thickness is 70 nm or less. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), the atomic ratio of Si is set to 1, the Ru content is 20 or less, and the film thickness is 30 nm or more.

[0092] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Ti, the composition ratio of Ru to Ti (Ru:Ti) is preferably 20:1 to 1:20.

[0093] When the relative reflectivity of the phase-shifted film 4 is 15% or more (absolute reflectivity 10%), with the atomic ratio of Ru set to 1, the amount of Ti is 20 or less, and the film thickness is 66 nm or less. When the relative reflectivity of the phase-shifted film 4 is 25% or less (absolute reflectivity 17% or less), with the atomic ratio of Ti set to 6, the amount of Ru is 4 or less, and the film thickness is 45 nm or more. When the relative reflectivity of the phase-shifted film 4 is 40% or less (absolute reflectivity 27% or less), with the atomic ratio of Ti set to 1, the amount of Ru is 20 or less, and the film thickness is 30 nm or more.

[0094] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and V, the composition ratio of Ru to V (Ru:V) is preferably 20:1 to 1:20.

[0095] When the relative reflectivity of the phase-shifting film 4 is 6% or higher, with the Ru atomic ratio set to 1, V is 20 or less, and the film thickness is 55 nm or less. When the relative reflectivity of the phase-shifting film 4 is 15% or higher, with the Ru atomic ratio set to 2, V is 7 or less, and the film thickness is 47 nm or less. When the relative reflectivity of the phase-shifting film 4 is 25% or lower, with the V atomic ratio set to 9, Ru is 11 or less, and the film thickness is 37 nm or higher. When the relative reflectivity of the phase-shifting film 4 is 40% or lower, with the V atomic ratio set to 1, Ru is 20 or less, and the film thickness is 30 nm or higher.

[0096] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Ge, the composition ratio of Ru to Ge (Ru:Ge) is preferably 20:1 to 1:1.

[0097] When the relative reflectivity of the phase-shifted film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 1, Ge is 1 or less, and the film thickness is 66 nm or less. When the relative reflectivity of the phase-shifted film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 7, Ge is 3 or less, and the film thickness is 46 nm or less. When the relative reflectivity of the phase-shifted film 4 is 25% or less (absolute reflectivity 17% or less), with the Ge atomic ratio set to 1, Ru is 5 or less, and the film thickness is 38 nm or more. When the relative reflectivity of the phase-shifted film 4 is 40% or less (absolute reflectivity 27% or less), with the Ge atomic ratio set to 1, Ru is 20 or less, and the film thickness is 31 nm or more.

[0098] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Nb, the composition ratio of Ru to Nb (Ru:Nb) is preferably 20:1 to 5:1.

[0099] When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), the atomic ratio of Ru is set to 20, Nb is 1 or more, and the film thickness is 30 nm or more. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), the atomic ratio of Nb is set to 1, Ru is 5 or more, and the film thickness is 32 nm or less.

[0100] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Mo, the composition ratio of Ru to Mo (Ru:Mo) is preferably 20:1 to 4:1.

[0101] When the relative reflectivity of the phase-shifted film 4 is 15% or more (absolute reflectivity 10% or more), the atomic ratio of Ru is set to 20, the Mo content is 1 or more, and the film thickness is 30 nm or more. When the relative reflectivity of the phase-shifted film 4 is 40% or less (absolute reflectivity 27% or less), the atomic ratio of Mo is set to 1, the Ru content is 4 or more, and the film thickness is 33 nm or less.

[0102] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Sn, the composition ratio of Ru to Sn (Ru:Sn) is preferably 20:1 to 3:2.

[0103] When the relative reflectivity of the phase-shifting film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 3, Sn is 2 or less, and the film thickness is 39 nm or less. When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 4, Sn is 1 or less, and the film thickness is 33 nm or less. When the relative reflectivity of the phase-shifting film 4 is 25% or less (absolute reflectivity 17% or less), with the Sn atomic ratio set to 2, Ru is 23 or less, and the film thickness is 31 nm or more. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), with the Sn atomic ratio set to 1, Ru is 20 or less, and the film thickness is 30 nm or more.

[0104] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Te, the composition ratio of Ru to Te (Ru:Te) is preferably 20:1 to 3:1.

[0105] When the relative reflectivity of the phase-shifted film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 3, the Te content is 1 or less, and the film thickness is 40 nm or less. When the relative reflectivity of the phase-shifted film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 8, the Te content is 1 or less, and the film thickness is 33 nm or less. When the relative reflectivity of the phase-shifted film 4 is 25% or less (absolute reflectivity 17% or less), with the Te atomic ratio set to 1, the Ru content is 15 or less, and the film thickness is 31 nm or more. When the relative reflectivity of the phase-shifted film 4 is 40% or less (absolute reflectivity 27% or less), with the Te atomic ratio set to 1, the Ru content is 20 or less, and the film thickness is 30 nm or more.

[0106] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Hf, the composition ratio of Ru to Hf (Ru:Hf) is preferably 20:1 to 1:2.

[0107] When the relative reflectivity of the phase-shifting film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 1, Hf is 2 or less, and the film thickness is 58 nm or less. When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 16, Hf is 9 or less, and the film thickness is 40 nm or less. When the relative reflectivity of the phase-shifting film 4 is 25% or less (absolute reflectivity 17% or less), with the Hf atomic ratio set to 9, Ru is 41 or less, and the film thickness is 32 nm or more. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), with the Hf atomic ratio set to 1, Ru is 20 or less, and the film thickness is 30 nm or more.

[0108] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and W, the composition ratio of Ru to W (Ru:W) is preferably 20:1 to 1:20.

[0109] When the relative reflectivity of the phase-shifting film 4 is 6% or more (absolute reflectivity 4% or more), with the Ru atomic ratio set to 1, W is 20 or less, and the film thickness is 46 nm or less. When the relative reflectivity of the phase-shifting film 4 is 15% or more (absolute reflectivity 10% or more), with the Ru atomic ratio set to 17, W is 33 or less, and the film thickness is 39 nm or less. When the relative reflectivity of the phase-shifting film 4 is 25% or less (absolute reflectivity 17% or less), with the W atomic ratio set to 7, Ru is 13 or less, and the film thickness is 32 nm or more. When the relative reflectivity of the phase-shifting film 4 is 40% or less (absolute reflectivity 27% or less), with the W atomic ratio set to 1, Ru is 20 or less, and the film thickness is 30 nm or more.

[0110] When the phase shift film 4 of the reflective photomask substrate 100 in this embodiment contains Ru and Re, the composition ratio of Ru to Re (Ru:Re) is preferably 20:1 to 1:20.

[0111] When the relative reflectance of the phase-shifted film 4 is 6% or more (absolute reflectance 4% or more), with the Ru atomic ratio set to 1, the Re content is 20 or less, and the film thickness is 38 nm or less. When the relative reflectance of the phase-shifted film 4 is 15% or more (absolute reflectance 10% or more), with the Ru atomic ratio set to 9, the Re content is 16 or less, and the film thickness is 33 nm or less. When the relative reflectance of the phase-shifted film 4 is 25% or less (absolute reflectance 17% or less), with the Re atomic ratio set to 9, the Ru content is 16 or less, and the film thickness is 32 nm or more. When the relative reflectance of the phase-shifted film 4 is 40% or less (absolute reflectance 27% or less), with the Re atomic ratio set to 1, the Ru content is 20 or less, and the film thickness is 29 nm or more.

[0112] As described above, by using a specific range of composition (atomic ratio) of Ru with Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W or Re, a phase shift film 4 with higher reflectivity and a specific phase difference can be obtained with a thinner film thickness.

[0113] The above description primarily focuses on specific binary Ru-based materials. However, ternary materials (e.g., RuCrNi, RuCrCo, RuNiCo, and RuCrW) and quaternary materials (e.g., RuCrNiCo and RuCrCoW) also possess the same properties as the specific binary Ru-based materials. Therefore, ternary or quaternary materials can be used as specific Ru-based materials.

[0114] The phase shift film 4 is a specific Ru-based material containing at least one element selected from Ru, Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re, and further containing other elements, within a range that does not significantly affect the refractive index and extinction coefficient. The specific Ru-based material may contain elements such as nitrogen (N), oxygen (O), carbon (C), or boron (B). For example, adding nitrogen (N) to a specific Ru-based material can suppress the oxidation of the phase shift film 4, thereby stabilizing the properties of the phase shift film 4. Furthermore, when nitrogen (N) is added to a specific Ru-based material, the crystalline state can be easily changed to an amorphous state regardless of the sputtering conditions. In this case, the nitrogen content is preferably 1 atomic% or more, more preferably 3 atomic% or more. Also, the nitrogen content is preferably 10 atomic% or less. Regarding oxygen (O), carbon (C), and boron (B), they can be added to the material of the phase shifting film 4 within a range that does not significantly affect the refractive index and extinction coefficient, in order to stabilize the phase shifting film 4. When the material of the phase shifting film 4 contains Ru, and at least one of the elements selected from Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re, and other elements, the content of the aforementioned elements other than those elements is preferably 10 atomic% or less, more preferably 5 atomic% or less.

[0115] The phase shift film 4 of the aforementioned specific Ru-based material can be formed using known methods such as DC (Direct Current) sputtering and RF (Radio Frequency) sputtering, or magnetron sputtering. Furthermore, the target can be an alloy target of Ru with at least one of the elements selected from Cr, Ni, Co, Al, Si, Ti, V, Ge, Nb, Mo, Sn, Te, Hf, W, and Re.

[0116] Furthermore, as targets, Ru targets, as well as Cr targets, Ni targets, Co targets, Al targets, Si targets, Ti targets, V targets, Ge targets, Nb targets, Mo targets, Sn targets, Te targets, Hf targets, W targets, and / or Re targets, can be used for co-sputtering to form films. Co-sputtering has the advantage of easily adjusting the composition ratio of metal elements, but compared with alloy targets, the crystalline state of the film is more likely to become columnar. During sputtering, by forming the film with nitrogen (N), the crystalline state can be changed to an amorphous form.

[0117] The phase shift film 4 can be a single-layer film containing only a specific Ru-based material, or it can be a multilayer film containing two or more layers. In the case of a single-layer film, it has the advantage of reducing the number of steps in the photomask substrate manufacturing process and improving production efficiency. Furthermore, when the phase shift film 4 is, for example, a single-layer film that is substantially oxygen-free, such as a specific Ru-based material film, a natural oxide film forms on the surface after the phase shift film 4 is exposed to the atmosphere. In this case, it is preferable to remove the natural oxide film using a fluorine-based gas, followed by etching using a chlorine-based gas.

[0118] Due to its short wavelength, EUV light tends to exhibit a high degree of dependence on film thickness for both phase difference and reflectivity. Therefore, stability of the phase difference and reflectivity is required for variations in the film thickness of the phase shift film 4. However, as shown in Figure 3, the phase difference and reflectivity exhibit distinct vibrational structures depending on the film thickness of the phase shift film 4. Because the vibrational structures of the phase difference and reflectivity differ, it is difficult to determine a film thickness that simultaneously stabilizes both the phase difference and reflectivity.

[0119] Therefore, ideally, even if the thickness of the phase shift film 4 varies slightly from the design value (e.g., within ±0.5% of the design thickness), the phase difference unevenness between surfaces is within a specific range of ±2 degrees (e.g., 180 degrees ± 2 degrees when the phase difference is 180 degrees), and the reflectivity unevenness between surfaces is within a specific range of ±0.2% (e.g., 6% ± 0.2% when the relative reflectivity is 6%). When the phase shift film 4 is a multilayer film, controlling the phase difference unevenness and reflectivity unevenness between surfaces within specific ranges becomes easier. Thus, by making the phase shift film 4 a multilayer film, various functions can be added to each layer.

[0120] When the phase shift film 4 is formed from the uppermost layer and the lower layers excluding the uppermost layer, the vibration structure can be smoothed out by suppressing the reflected EUV light from the surface of the uppermost layer, thereby obtaining a stable phase difference and reflectivity that are not affected by film thickness variations. The material of this uppermost layer is preferably a silicon compound or a tantalum compound having a refractive index greater than that of the lower layers of the phase shift film 4. Examples of silicon compounds include those containing Si and at least one element selected from N, O, C, and H, with SiO2, SiON, and Si3N4 being preferred. Examples of tantalum compounds include those containing Ta and at least one element selected from N, O, C, H, and B, with materials containing both Ta and O being preferred. The film thickness of the uppermost layer is preferably 10 nm or less, more preferably 1 to 6 nm, and even more preferably 3 to 5 nm. When the lower layer is a RuCr film, for example, the uppermost layer can be a SiO2 film or a Ta2O5 film.

[0121] A phase shift film 4 of a specific ruthenium (Ru)-based material, containing a metal of at least one element selected from Ru, Cr, Ni, Co, V, Nb, Mo, W, and Re, can be dry-etched using an oxygen-containing chlorine-based gas or oxygen. Alternatively, a phase shift film 4 of a specific ruthenium (Ru)-based material, containing Ru, and at least one element selected from Al, Si, Ti, Ge, Sn, and Hf, can be dry-etched using an oxygen-free chlorine-based gas. Chlorine-based gases such as Cl2, SiCl4, CHCl3, CCl4, and BCl3 can be used. These etching gases may, as needed, contain inert gases such as He and / or Ar.

[0122] Furthermore, the phase shift film 4 of a specific ruthenium (Ru)-based material containing Ru and at least one of the elements selected from Al, Si, Ti, Nb, Mo, Sn, Te, Hf, W, and Re can be dry-etched using a fluorine-based gas. Fluorine-based gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, C3F8, and / or SF6 can be used. These etching gases can be used individually or as a mixture of two or more of the aforementioned fluorine-based gases. Additionally, inert gases such as He and / or Ar, or O2 gas, may be included as needed.

[0123] <<Etching Photomask>> An etching mask film can be formed on or in contact with the surface of the phase shift film 4. As the material for the etching mask film, a material with a higher etch selectivity ratio relative to the phase shift film 4 is used. Here, "etch selectivity ratio of B relative to A" refers to the ratio of the etching rate of the layer not to be etched (the layer that becomes the mask), i.e., A, to the etching rate of the layer to be etched, i.e., B. Specifically, it is defined by the formula "etch selectivity ratio of B relative to A = etching rate of B / etching rate of A". Furthermore, "higher selectivity ratio" means that the selectedivity ratio value defined above is larger relative to the comparison object. The etch selectivity ratio of the phase shift film 4 relative to the etching mask film is preferably 1.5 or higher, and more preferably 3 or higher.

[0124] The phase shift film 4, which is a specific ruthenium (Ru)-based material containing a metal of at least one of the elements selected from Ru, Cr, Ni, Co, V, Nb, Mo, W, and Re, can be etched by dry etching using an oxygen-containing chlorine gas or oxygen. As a material with higher etching selectivity than the etch mask film, the phase shift film 4 can be made of silicon or silicon compounds, or tantalum (Ta)-based materials.

[0125] Examples of silicon compounds that can be used for etching photomasks include: materials containing Si and at least one element selected from N, O, C, and H; and materials containing a metal, such as metallic silicon (metal silicates) or metallic silicon compounds (metal silicate compounds). Examples of metallic silicon compounds include materials containing a metal and Si, and at least one element selected from N, O, C, and H.

[0126] As tantalum (Ta)-based materials that can be used as etching photomasks, examples include materials in which tantalum (Ta) contains one or more elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H). Among these, materials containing both tantalum (Ta) and oxygen (O) are particularly preferred as etching photomask materials. Specific examples of such materials include tantalum oxide (TaO), tantalum oxynitride (TaON), boron tantalum oxide (TaBO), and boron tantalum oxynitride (TaBON).

[0127] Furthermore, the phase shift film 4 of a specific ruthenium (Ru)-based material containing Ru and at least one of the elements selected from Al, Si, Ti, Ge, Sn, and Hf can be etched by dry etching using an oxygen-free chlorine gas. Silicon or silicon compounds can be used as materials with higher etching selectivity for the specific ruthenium (Ru)-based phase shift film 4 compared to the etch mask film. Examples of silicon compounds include: materials containing Si and at least one element selected from N, O, C, and H; and materials containing a metal, such as metal silicon (metal silicates) or metal silicon compounds (metal silicate compounds). Examples of metal silicon compounds include materials containing a metal and Si, and at least one element selected from N, O, C, and H.

[0128] Furthermore, the phase shift film 4 of a specific ruthenium (Ru)-based material containing Ru and at least one of the elements selected from Al, Si, Ti, Nb, Mo, Sn, Te, Hf, W and Re can be dry-etched using fluorine-based gases.

[0129] Furthermore, when the phase shift film 4 comprises multiple layers and the uppermost layer of the phase shift film 4 is etched using a fluorine-based gas, chromium or a chromium compound can be used as the material for etching the photomask. Examples of chromium compounds include those containing Cr and at least one element selected from N, O, C, and H.

[0130] From the viewpoint of achieving the function of an etching mask by accurately forming a transfer pattern on the phase shift film 4, the thickness of the etching mask film is ideally 3 nm or more. Furthermore, from the viewpoint of thinning the thickness of the resist film 11, the thickness of the etching mask film is ideally 15 nm or less.

[0131] <<Back Conductive Film 5>> Generally, a back conductive film 5 for electrostatic chucks is formed on the second main surface (back side) of substrate 1 (opposite to the surface where the multilayer reflective film 2 is formed). The required electrical characteristics (sheet resistance) of the back conductive film 5 for electrostatic chucks are typically below 100 Ω / □ (Ω / Square). The back conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering, using a target made of metals and alloys such as chromium and tantalum.

[0132] The chromium (Cr) material of the back conductive film 5 is preferably a Cr compound containing Cr and further containing at least one of boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include: CrN, CrON, CrCN, CrCO, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.

[0133] As the material containing tantalum (Ta) for the back conductive film 5, it is preferable to use Ta (tantalum), a Ta-containing alloy, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon. Examples of Ta compounds include: TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0134] As for materials containing tantalum (Ta) or chromium (Cr), it is preferable that the nitrogen (N) content in the surface layer is low. Specifically, the nitrogen content in the surface layer of the conductive film 5 on the back side of the material containing tantalum (Ta) or chromium (Cr) is preferably less than 5 atomic%, and more preferably, the surface layer contains no nitrogen at all. The reason for this is that in the conductive film 5 on the back side of the material containing tantalum (Ta) or chromium (Cr), a lower nitrogen content in the surface layer results in improved wear resistance.

[0135] The back conductive film 5 is preferably made of a material containing tantalum and boron. By including tantalum and boron in the back conductive film 5, a back conductive film 5 with wear resistance and chemical resistance can be obtained. When the back conductive film 5 contains tantalum (Ta) and boron (B), the B content is preferably 5 to 30 atomic%. The ratio of Ta to B (Ta:B) in the sputtering target used for forming the back conductive film 5 is preferably 95:5 to 70:30.

[0136] The thickness of the back conductive film 5 is not particularly limited as long as it meets the function of being used as an electrostatic chuck. The thickness of the back conductive film 5 is typically 10 nm to 200 nm. Furthermore, the back conductive film 5 also takes into account the stress adjustment of the second main surface side of the photomask substrate 100, and is adjusted in a way that balances the stress from the various films formed on the first main surface side to obtain a flat reflective photomask substrate 100.

[0137] <Reflective Photomask 200 and its Manufacturing Method> This embodiment is a reflective photomask 200 having a phase shift pattern 4a patterned on the phase shift film 4 of the aforementioned reflective photomask substrate 100. The phase shift pattern 4a can be formed by patterning the phase shift film 4 of the aforementioned reflective photomask substrate 100 using a specific dry etching gas (e.g., a dry etching gas containing chlorine-based gases and oxygen). The phase shift pattern 4a of the reflective photomask 200 can absorb EUV light and reflect a portion of EUV light with a specific phase difference (e.g., 180 degrees) with the opening (the portion where the phase shift pattern is not formed). The specific dry etching gas can be a chlorine-based gas and oxygen, a chlorine-based gas, or a fluorine-based gas and oxygen, etc. In order to pattern the phase shift film 4, an etched photomask film can also be provided on the phase shift film 4 as needed, the etched photomask film pattern can be used as a photomask, and the phase shift film 4 can be dry etched to form the phase shift pattern 4a.

[0138] The method for manufacturing a reflective photomask 200 using the reflective photomask substrate 100 of this embodiment will be described. Here, only a brief description will be given, and thereafter, detailed descriptions will be provided with reference to the drawings in the embodiments.

[0139] A reflective photomask substrate 100 is prepared, and a resist film 11 is formed on the phase shift film 4 on its first main surface (this step is not necessary when the resist film 11 is used as the reflective photomask substrate 100). The desired pattern is drawn (exposed) on the resist film 11, and then developed and washed to form a specific resist pattern 11a.

[0140] In the case of a reflective photomask substrate 100, the resist pattern 11a is used as a photomask to etch the phase shift film 4 to form a phase shift pattern 4a. The resist pattern 11a is then removed using an ashing solution or resist stripping solution, thereby forming the phase shift pattern 4a. Finally, a wet cleaning process using an acidic or alkaline aqueous solution is performed.

[0141] The etching gas for the phase shift film 4 is appropriately selected based on the specific Ru-based material. For example, when the material of the phase shift film 4 contains Ru and at least one of the elements selected from Cr, Ni, Co, V, Nb, Mo, W, and Re, an oxygen-containing chlorine-based gas or oxygen is used as the etching gas for the phase shift film 4. By using a protective film 3 containing silicon (Si) or a material containing both silicon (Si) and oxygen (O), the surface of the protective film 3 will not become rough during the etching of the phase shift film 4.

[0142] Furthermore, when the material of the phase shift film 4 is a material containing at least one of the elements selected from Ru, Al, Si, Ti, Ge, Sn, and Hf, a fluorine-based gas or a chlorine-based gas that does not contain oxygen is used as the etching gas for the phase shift film 4. In this case, by appropriately selecting the material of the protective film 3 from silicon (Si), a silicon-based material containing silicon (Si) and oxygen (O), or a silicon-based material containing silicon (Si) and nitrogen (N), and chromium (Cr), or a chromium-based material containing Cr (Cr), oxygen (O), nitrogen (N), and carbon (C), the surface of the protective film 3 will not become rough during the etching of the phase shift film 4.

[0143] Through the above steps, a reflective photomask 200 with high-precision micro-patterns and less shadowing effect and less sidewall roughness can be obtained.

[0144] <Semiconductor Device Manufacturing Methods> This embodiment describes a method for manufacturing a semiconductor device. By placing the reflective photomask 200 of this embodiment on an exposure apparatus with an exposure light source having EUV light, and transferring the transfer pattern onto a resist film formed on a substrate to be transferred, a semiconductor device can be manufactured.

[0145] Specifically, by using the reflective photomask 200 of this embodiment for EUV exposure, the reduction in transfer dimensional accuracy caused by the shading effect can be suppressed, and the desired transfer pattern based on the phase shift pattern 4a can be formed on the semiconductor substrate. Furthermore, since the phase shift pattern 4a is a fine and high-precision pattern with low sidewall roughness, a high-dimensional-accuracy and desired pattern can be formed on the semiconductor substrate. Through various steps, including etching of the processed film, formation of insulating and conductive films, introduction of dopants, and annealing, in addition to this photolithography step, a semiconductor device with a desired electronic circuit can be manufactured.

[0146] In more detail, the EUV exposure apparatus includes a laser plasma light source that generates EUV light, an illumination optics system, a photomask stage system, a reduction projection optics system, a wafer platform system, and vacuum equipment. The light source has a debris trap function, as well as a cutoff filter to block long-wavelength light other than the exposure light, and equipment for differential vacuum exhaust. The illumination optics system and the reduction projection optics system include reflective mirrors. The EUV exposure reflective photomask 200 is electrostatically attached to the photomask stage by a conductive film 5 formed on the back of its second main surface.

[0147] EUV light is emitted from an illumination optics system at an angle of 6 to 8 degrees relative to the vertical plane of the reflective photomask 200. Reflected light from the reflective photomask 200, relative to the incident light, is reflected at an angle opposite to the incident direction and the same as the incident angle (unidirectional emission) and directed to a reflective projection optics system, typically with a 1 / 4 scale-down ratio, for exposure of a resist on a wafer (semiconductor substrate) placed on a wafer platform. During this process, vacuum is evacuated at least at the location through which the EUV light passes. Furthermore, during this exposure, scanning exposure, where the photomask stage and wafer platform are synchronized according to the scale-down ratio of the projection optics system, and exposure is performed through a slit, is the mainstream method. By developing the resist film after exposure, a resist pattern can be formed on the semiconductor substrate. In this embodiment, a photomask with a thin film exhibiting minimal shading effect and a high-precision phase-shift pattern with low sidewall roughness is used. Therefore, resist patterns formed on semiconductor substrates are desirable for achieving high dimensional accuracy. By using the resist pattern as a photomask and performing etching, specific wiring patterns can be formed on, for example, a semiconductor substrate. Semiconductor devices are then manufactured through such exposure steps or processing film steps, forming steps of insulating or conductive films, dopant introduction steps, or annealing steps, and other necessary steps.

[0148] According to the semiconductor device manufacturing method of this embodiment, a reflective photomask 200 can be used to manufacture a semiconductor device. This reflective photomask 200 can reduce the thickness of the phase shift film 4, reduce the shading effect, and form a fine and high-precision phase shift pattern 4a with a stable cross-sectional shape and less sidewall roughness. Therefore, a semiconductor device with a fine and high-precision transfer pattern can be manufactured. [Example]

[0149] The following description refers to both the drawings and the embodiments. This embodiment is not limited to these embodiments. Furthermore, in the embodiments, the same reference numerals are used for the same constituent elements, and descriptions are simplified or omitted.

[0150] [Example 1] Figure 2 is a schematic cross-sectional view of the main parts of the steps in manufacturing a reflective photomask 200 from a reflective photomask substrate 100.

[0151] The reflective photomask substrate 100 has a back 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 in Embodiment 1 contains a material containing RuCr. Furthermore, as shown in FIG2(a), a resist film 11 is formed on the phase shift film 4.

[0152] First, the reflective photomask substrate 100 of Example 1 will be described.

[0153] Prepare a 6025-sized (approximately 152 mm × 152 mm × 6.35 mm) low thermal expansion glass substrate, i.e., a SiO2-TiO2-based glass substrate, with two main surfaces, the first and second main surfaces, after grinding, and designate it as substrate 1. Grinding is performed in a manner that makes the main surfaces flat and smooth, including rough grinding, precision grinding, local processing, and contact grinding steps.

[0154] A back conductive film 5 containing a CrN film is formed on the second main surface (back side) of a SiO2-TiO2 glass substrate 1 under the following conditions by magnetron sputtering (reactive sputtering). The formation conditions of the back conductive film 5 are: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0155] Next, a multilayer reflective film 2 is formed on the main surface (first main surface) of the substrate 1 opposite to the side where the back conductive film 5 is formed. The multilayer reflective film 2 formed on the substrate 1 is a periodic multilayer reflective film containing Mo and Si, designed to be suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 2 is formed by alternately depositing Mo and Si layers on the substrate 1 using a Mo target and a Si target in an Ar gas atmosphere via ion beam sputtering. First, a Si film with a thickness of 4.2 nm is formed, followed by a Mo film with a thickness of 2.8 nm. This is considered one cycle, and the same process is repeated for 40 cycles. Finally, a Si film with a thickness of 4.0 nm is formed, thus creating the multilayer reflective film 2. Here, 40 cycles are used, but it is not limited to this; for example, 60 cycles are also possible. While the number of steps increases compared to 40 cycles when 60 cycles are used, the reflectivity for EUV light can be improved.

[0156] Subsequently, in an Ar gas atmosphere, a protective film 3 containing a SiO2 film was formed on the surface of the multilayer reflective film 2 with a film thickness of 2.5 nm by using RF sputtering with a SiO2 target.

[0157] Secondly, a phase-shifted film 4 containing a RuCr film was formed by DC magnetron sputtering. The RuCr film was formed using a RuCr target in an Ar gas atmosphere to achieve a film thickness of 45.0 nm. The atomic ratio of the RuCr film was Ru:Cr = 7:93. The crystal structure of the RuCr film was determined by X-ray diffraction (XRD), and the results showed that the RuCr film has an amorphous structure.

[0158] 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 are as follows. RuCr membrane: n=0.929, k=0.037

[0159] The phase-shifting film 4 containing the RuCr film has a relative reflectance of 6% (absolute reflectance of 4%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 45.0 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 31% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0160] Next, using the aforementioned reflective photomask substrate 100, a reflective photomask 200 is manufactured.

[0161] As described above, a resist film 11 with a thickness of 100 nm is formed on the phase shift film 4 of the reflective photomask substrate 100 (Fig. 2(a)). Then, the desired pattern is drawn (exposed) on the resist film 11, followed by development and washing, thereby forming a specific resist pattern 11a (Fig. 2(b)). Next, the resist pattern 11a is used as a photomask, and the RuCr film (phase shift film 4) is dry-etched using a mixture of Cl2 gas and O2 gas (gas flow ratio Cl2:O2=4:1), thereby forming a phase shift pattern 4a (Fig. 2(c)).

[0162] Subsequently, the resist pattern 11a is removed using an ashing solution or resist stripping solution. Finally, a wet cleaning with pure water (DIW) is performed to manufacture the reflective photomask 200 (Fig. 2(d)). Furthermore, if necessary, a photomask defect inspection can be performed after wet cleaning, and appropriate photomask defect corrections can be made.

[0163] In the reflective photomask 200 of Example 1, since the phase shift film 4 is made of RuCr material, the good processability of the mixed gas of Cl2 and O2 allows the phase shift pattern 4a to be formed with high precision. Furthermore, the phase shift pattern 4a has a film thickness of 45.0 nm, which is thinner than the absorber film formed from Ta-based materials previously, thus reducing the shadowing effect compared to Comparative Example 1.

[0164] Furthermore, the reflective photomask 200 fabricated in Example 1 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER (Line Edge Roughness) or in-plane unevenness of the transferred resist pattern is less, resulting in higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity (reflectivity relative to the reflectivity of the multilayer reflective film with protective film) of the phase shift surface is 6% (absolute reflectivity is 4%), a sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0165] The reflective photomask 200 fabricated in Example 1 is placed on an EUV scanner to perform EUV exposure on a wafer on which a processing film and a resist film are formed on a semiconductor substrate. Then, by developing the exposed resist film, a resist pattern is formed on the semiconductor substrate on which the processing film is formed. The resist pattern is transferred to the processing film by etching. Furthermore, through various steps such as the formation of insulating and conductive films, the introduction of dopants, and annealing, a semiconductor device with the desired characteristics can be manufactured.

[0166] [Example 2] Example 2 is an example in which the material of the phase shift film 4 is a RuNi film, and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0167] That is, in Example 2, a phase shift film 4 containing a RuNi film was formed on a protective film 3 containing a SiO2 film by DC magnetron sputtering. The RuNi film was formed using a RuNi target in an Ar gas atmosphere to a thickness of 38.2 nm. The atomic ratio of the RuNi film was Ru:Ni = 45:55. The crystal structure of the RuNi film was determined by X-ray diffraction (XRD), and the results showed that the RuNi film has an amorphous structure.

[0168] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuNi film formed in Example 2 as described above at a wavelength of 13.5 nm are as follows. RuNi film: n=0.917, k=0.045

[0169] The phase-shifting film 4 containing the RuNi film has a relative reflectance of 6% (absolute reflectance of 4%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 38.2 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 41% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0170] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0171] In the reflective photomask 200 of Example 2, since the phase shift film 4 is made of RuNi material, the good processability of the mixed gas of Cl2 and O2 allows the phase shift pattern 4a to be formed with high precision. Furthermore, the phase shift pattern 4a has a film thickness of 38.2 nm, which is thinner than the absorber film formed from Ta-based materials previously, thus reducing the shadowing effect compared to Comparative Example 1.

[0172] Furthermore, the reflective photomask 200 fabricated in Example 2 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 6% (absolute reflectivity is 4%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0173] Similar to Example 1, the reflective photomask 200 fabricated in Example 2 can be used to manufacture a semiconductor device with the desired characteristics.

[0174] [Example 3] Example 3 is an example in which the material of the phase shift film 4 is a RuCo film, and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0175] Specifically, in Example 3, a phase shift film 4 containing a RuCo film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuCo film was formed using a RuCo target in an Ar gas atmosphere to a thickness of 37.9 nm. The atomic ratio of the RuCo film was Ru:Co = 36:64. The crystal structure of the RuCo film was determined by X-ray diffraction (XRD), and the results showed that the RuCo film has an amorphous structure.

[0176] 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 are as follows. RuCo membrane: n=0.914, k=0.046

[0177] The phase-shifting film 4 containing the RuCo film has a relative reflectance of 6% (absolute reflectance of 4%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 37.9 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 42% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below, thereby reducing shading effects.

[0178] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0179] In the reflective photomask 200 of Example 3, since the phase shift film 4 is made of RuCo material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 37.9 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced compared with Comparative Example 1.

[0180] Furthermore, the reflective photomask 200 fabricated in Example 3 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 6% (absolute reflectivity is 4%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0181] Similar to Example 1, the reflective photomask 200 fabricated in Example 3 can be used to manufacture a semiconductor device with the desired characteristics.

[0182] [Example 4] Example 4 is an example in which the relative reflectivity of the phase shift film 4 is changed to 15% (the absolute reflectivity is 10%) and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1 and also includes the material (RuCr film).

[0183] Specifically, in Example 4, a phase shift film 4 containing a RuCr film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuCr film was formed using a RuCr target in an Ar gas atmosphere to a thickness of 37.9 nm. The atomic ratio of the RuCr film was Ru:Cr = 39:61. The crystal structure of the RuCr film was determined by X-ray diffraction (XRD), and the results showed that the RuCr film has an amorphous structure.

[0184] 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 are as follows. RuCr membrane: n=0.913, k=0.030

[0185] The phase-shifting film 4 containing the RuCr film has a relative reflectance of 15% (absolute reflectance of 10%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 37.9 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 42% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0186] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0187] In the reflective photomask 200 of Example 4, since the phase shift film 4 is made of RuCr material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 37.9 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced compared with Example 1.

[0188] Furthermore, the reflective photomask 200 fabricated in Example 4 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 15% (absolute reflectivity is 10%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0189] Similar to Example 1, the reflective photomask 200 fabricated in Example 4 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the reflectivity of the phase-shifted surface is 15%, the yield can be increased compared to Example 1.

[0190] [Example 5] Example 5 is an example in which the material of the phase shift film 4 is set to RuNi film, so that the relative reflectivity of the phase shift film 4 becomes 15% (absolute reflectivity is 10%), and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0191] Specifically, in Example 5, a phase-shifting film 4 containing a RuNi film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuNi film was formed using a RuNi target in an Ar gas atmosphere to a thickness of 32.2 nm. The atomic ratio of the RuNi film was Ru:Ni = 67:33. The crystal structure of the RuNi film was determined by X-ray diffraction (XRD), and the results showed that the RuNi film has an amorphous structure.

[0192] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuNi film formed as described above in Example 5 are as follows. RuNi film: n=0.904, k=0.033

[0193] The phase-shifting film 4 containing the RuNi film has a relative reflectance of 15% (absolute reflectance of 10%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 32.2 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 50% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0194] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0195] In the reflective photomask 200 of Example 5, since the phase shift film 4 is made of RuNi material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 32.2 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced compared with Example 2.

[0196] Furthermore, the reflective photomask 200 fabricated in Example 5 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 15% (absolute reflectivity is 10%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0197] Similar to Example 1, the reflective photomask 200 fabricated in Example 5 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the relative reflectivity of the phase-shifted surface is 15% (absolute reflectivity is 10%), the yield can be increased compared to Example 2.

[0198] [Example 6] Example 6 is an example in which the material of the phase shift film 4 is set to RuCo film, so that the relative reflectivity of the phase shift film 4 becomes 15% (absolute reflectivity is 10%), and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0199] Specifically, in Example 6, a phase shift film 4 containing a RuCo film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuCo film was formed using a RuCo target in an Ar gas atmosphere to a thickness of 31.9 nm. The atomic ratio of the RuCo film was Ru:Co = 61:39. The crystal structure of the RuCo film was determined by X-ray diffraction (XRD), and the results showed that the RuCo film has an amorphous structure.

[0200] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCo film of Example 6 formed as described above at a wavelength of 13.5 nm are as follows. RuCo membrane: n=0.902, k=0.034

[0201] The phase-shifting film 4 containing the RuCo film has a relative reflectance of 15% (absolute reflectance of 10%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 31.9 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 51% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0202] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0203] In the reflective photomask 200 of Example 6, since the phase shift film 4 is made of RuCo material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 31.9 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced compared with Example 3.

[0204] Furthermore, the reflective photomask 200 fabricated in Example 6 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 15% (absolute reflectivity is 10%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0205] Similar to Example 1, the reflective photomask 200 fabricated in Example 6 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the relative reflectivity of the phase-shifted surface is 15% (absolute reflectivity is 10%), the yield can be increased compared to Example 3.

[0206] [Example 7] Example 7 is an example in which the relative reflectivity of the phase shift film 4 is changed to 20% (absolute reflectivity is 13.3%) and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1 and also includes the material (RuCr film).

[0207] Specifically, in Example 7, a phase-shifting film 4 containing a RuCr film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuCr film was formed using a RuCr target in an Ar gas atmosphere to a thickness of 32.6 nm. The atomic ratio of the RuCr film was Ru:Cr = 56:44. The crystal structure of the RuCr film was determined by X-ray diffraction (XRD), and the results showed that the RuCr film has an amorphous structure.

[0208] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCr film of Example 7 formed as described above at a wavelength of 13.5 nm are as follows. RuCr membrane: n=0.905, k=0.026

[0209] The phase-shifting film 4 containing the RuCr film has a relative reflectance of 20% (absolute reflectance of 13.3%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 32.6 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 50% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0210] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0211] In the reflective photomask 200 of Example 7, since the phase shift film 4 is made of RuCr material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 32.6 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced compared with Example 4.

[0212] Furthermore, the reflective photomask 200 fabricated in Example 7 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 20% (absolute reflectivity is 13.3%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0213] Similar to Example 1, the reflective photomask 200 fabricated in Example 7 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the relative reflectivity of the phase-shifted surface is 20% (absolute reflectivity is 13.3%), the yield can be increased compared to Example 4.

[0214] [Example 8] Example 8 is an example in which the material of the phase shift film 4 is set to RuNi film, so that the relative reflectivity of the phase shift film 4 becomes 20% (absolute reflectivity is 13.3%), and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0215] Specifically, in Example 8, a phase shift film 4 containing a RuNi film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuNi film was formed using a RuNi target in an Ar gas atmosphere to a thickness of 31.8 nm. The atomic ratio of the RuNi film was Ru:Ni = 73:27. The crystal structure of the RuNi film was determined by X-ray diffraction (XRD), and the results showed that the RuNi film has an amorphous structure.

[0216] The refractive index n and extinction coefficient (imaginary part of complex refractive index) k of the RuNi film formed in Example 8 as described above at a wavelength of 13.5 nm are as follows. RuNi film: n=0.900, k=0.030

[0217] The phase-shifting film 4 containing the RuNi film has a relative reflectance of 20% (absolute reflectance of 13.3%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 31.8 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 51% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0218] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0219] In the reflective photomask 200 of Example 8, since the phase shift film 4 is made of RuNi material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 31.8 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced to the same extent as in Example 5.

[0220] Furthermore, the reflective photomask 200 fabricated in Example 8 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 20% (absolute reflectivity is 13.3%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0221] Similar to Example 1, the reflective photomask 200 fabricated in Example 8 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the relative reflectivity of the phase-shifted surface is 20% (absolute reflectivity is 13.3%), the yield can be increased compared to Example 5.

[0222] [Example 9] Example 9 is an example in which the material of the phase shift film 4 is set to RuCo film, so that the relative reflectivity of the phase shift film 4 becomes 20% (absolute reflectivity is 13.3%), and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0223] Specifically, in Example 9, a phase shift film 4 containing a RuCo film was formed on a protective film 3 containing a SiO2 film using DC magnetron sputtering. The RuCo film was formed using a RuCo target in an Ar gas atmosphere to a thickness of 31.6 nm. The atomic ratio of the RuCo film was Ru:Co = 69:31. The crystal structure of the RuCo film was determined by X-ray diffraction (XRD), and the results showed that the RuCo film has an amorphous structure.

[0224] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCo film of Example 9, formed as described above, at a wavelength of 13.5 nm are as follows. RuCo membrane: n=0.899, k=0.030

[0225] The phase-shifting film 4 containing the RuCo film has a relative reflectance of 20% (absolute reflectance of 13.3%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 31.6 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 51% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0226] Secondly, similar to Example 1, a reflective photomask 200 is manufactured using the above-described reflective photomask substrate 100.

[0227] In the reflective photomask 200 of Example 9, since the phase shift film 4 is made of RuCo material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 31.6 nm, which is thinner than the absorber film formed by the previous Ta-based material, and the shadowing effect can be reduced to the same extent as in Example 6.

[0228] Furthermore, the reflective photomask 200 fabricated in Example 9 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 20% (absolute reflectivity is 13.3%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0229] Similar to Example 1, the reflective photomask 200 fabricated in Example 9 can be used to manufacture a semiconductor device with the desired characteristics. In this case, since the relative reflectivity of the phase-shifted surface is 20% (absolute reflectivity is 13.3%), the yield can be increased compared to Example 6.

[0230] [Example 10] Example 10 is an embodiment in which the phase shift film 4 is made of RuNb film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuNb film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuNb film is formed using a RuNb target in an Ar gas atmosphere to achieve a film thickness of 30.3 nm. The RuNb content ratio (atomic ratio) is Ru:Nb = 20:1. The crystal structure of the RuNb film was determined by X-ray diffraction (XRD), and the results showed that the RuNb film has an amorphous structure.

[0231] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuNb film of Example 10 formed as described above at a wavelength of 13.5 nm are as follows. RuNb membrane: n=0.888, k=0.017

[0232] The phase-shifting film 4 containing the RuNb film has a relative reflectance of 39.7% (absolute reflectance of 26.5%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 30.3 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 53% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0233] Next, under the same conditions as in Example 1, a reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 10, since the phase shift film 4 is made of RuNb material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 30.3 nm, which is thinner than the absorber film formed from the previous Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0234] Furthermore, the reflective photomask 200 fabricated in Example 10 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 39.7% (absolute reflectivity is 26.5%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0235] Similar to Example 1, the reflective photomask 200 fabricated in Example 10 can be used to manufacture a semiconductor device with the desired characteristics.

[0236] [Example 11] Example 11 is an embodiment in which the phase shift film 4 is made of RuV film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuV film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuV film is formed using a RuV target in an Ar gas atmosphere, with a film thickness of 39.7 nm. The RuV film has an atomic ratio of Ru:V = 40:60. The crystal structure of the RuV film was determined by X-ray diffraction (XRD), and the results showed that the RuV film has an amorphous structure.

[0237] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuV film of Example 10 formed as described above at a wavelength of 13.5 nm are as follows. RuV membrane: n=0.921, k=0.022

[0238] The phase-shifting film 4 containing the RuV film has a relative reflectance of 18.8% (absolute reflectance of 12.5%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 39.7 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 39% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0239] Next, under the same conditions as in Example 1, a reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 11, since the phase shift film 4 is made of RuV material, the processability of the mixed gas of Cl2 and O2 is better, and the phase shift pattern 4a can be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 39.7 nm, which is thinner than the absorber film formed from the previous Ta-based material, and the shadowing effect can be reduced compared to Comparative Example 1.

[0240] Furthermore, the reflective photomask 200 fabricated in Example 11 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 18.8% (absolute reflectivity is 12.5%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0241] Similar to Example 1, the reflective photomask 200 fabricated in Example 11 can be used to manufacture a semiconductor device with the desired characteristics.

[0242] [Example 12] Example 12 is an embodiment in which the phase shift film 4 is made of RuHf film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuHf film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuHf film is formed using a RuHf target in an Ar gas atmosphere to achieve a film thickness of 45.2 nm. The RuHf film has an atomic ratio (Ru:Hf) of 56:44. The crystal structure of the RuHf film was determined by X-ray diffraction (XRD), and the results showed that the RuHf film has an amorphous structure.

[0243] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuHf film of Example 12 formed as described above at a wavelength of 13.5 nm are as follows. RuHf membrane: n=0.928, k=0.027

[0244] The phase-shifting film 4 containing the RuHf film has a relative reflectance of 12.3% (absolute reflectance of 8.2%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 45.2 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 30% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0245] Secondly, compared to Example 1, the dry etching gas was changed to Cl2 gas. Otherwise, under the same conditions as in Example 1, the reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 11, since the phase shift film 4 is made of RuHf material, although Cl2 gas was used, the dry etching time was slightly longer than in Example 1, but the processability was better, and the phase shift pattern 4a could be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 45.2 nm, which is thinner than the absorber film formed from Ta-based materials previously, and the shading effect can be reduced compared to Comparative Example 1.

[0246] Furthermore, the reflective photomask 200 fabricated in Example 12 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 12.3% (absolute reflectivity is 8.2%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0247] Similar to Example 1, the reflective photomask 200 fabricated in Example 12 can be used to manufacture a semiconductor device with the desired characteristics.

[0248] [Example 13] Example 13 is an example in which the phase shift film 4 is made of RuSn film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuSn film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuSn film is formed using a RuSn target in an Ar gas atmosphere to achieve a film thickness of 32.2 nm. The atomic ratio of the RuSn film is Ru:Sn = 80:20. The crystal structure of the RuSn film was determined by X-ray diffraction (XRD), and the result showed that the RuSn film has an amorphous structure.

[0249] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuSn film of Example 13 formed as described above at a wavelength of 13.5 nm are as follows. RuSn membrane: n=0.904, k=0.036

[0250] The phase-shifting film 4 containing the RuSn film has a relative reflectance of 12.8% (absolute reflectance of 8.5%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 32.2 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 50% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0251] Secondly, compared to Example 1, the dry etching gas was changed to Cl2 gas. Otherwise, under the same conditions as in Example 1, the reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 13, since the phase shift film 4 is made of RuSn material, although Cl2 gas was used, the dry etching time was slightly longer than in Example 1, but the processability was better, and the phase shift pattern 4a could be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 32.2 nm, which is thinner than the absorber film formed from Ta-based materials previously, and the shading effect can be reduced compared to Comparative Example 1.

[0252] Furthermore, the reflective photomask 200 fabricated in Example 13 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 12.8% (absolute reflectivity is 8.5%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0253] Similar to Example 1, the reflective photomask 200 fabricated in Example 13 can be used to manufacture a semiconductor device with the desired characteristics.

[0254] [Example 14] Example 14 is an embodiment in which the phase shift film 4 is made of RuSi film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuSi film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuSi film is formed using a RuSi target in an Ar gas atmosphere to achieve a film thickness of 34.1 nm. The atomic ratio of the RuSi film is Ru:Si = 86:14. The crystal structure of the RuSi film was measured using X-ray diffraction (XRD), and the results showed that the RuSi film has an amorphous structure.

[0255] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuSi film of Example 14 formed as described above at a wavelength of 13.5 nm are as follows. RuSi film: n=0.907, k=0.014

[0256] The phase-shifting film 4 containing the RuSi film has a relative reflectance of 34.1% (absolute reflectance of 22.7%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 34.1 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 48% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0257] Secondly, compared to Example 1, the dry etching gas was changed to Cl2 gas. Otherwise, under the same conditions as in Example 1, the reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 14, since the phase shift film 4 is made of RuSi material, although Cl2 gas was used, the dry etching time was slightly longer than in Example 1, but the processability was better, and the phase shift pattern 4a could be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 34.1 nm, which is thinner than the absorber film formed from Ta-based materials previously, and the shading effect can be reduced compared to Comparative Example 1.

[0258] Furthermore, the reflective photomask 200 fabricated in Example 14 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 34.1% (absolute reflectivity is 22.7%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0259] Similar to Example 1, the reflective photomask 200 fabricated in Example 14 can be used to manufacture a semiconductor device with the desired characteristics.

[0260] [Example 15] Example 15 is an example in which the phase shift film 4 is made of RuTi film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. Otherwise, it is the same as Example 1. Specifically, a phase shift film 4 containing a RuTi film is formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuTi film is formed using a RuTi target in an Ar gas atmosphere to achieve a film thickness of 45.7 nm. The atomic ratio of the RuTi film is Ru:Ti = 40:60. The crystal structure of the RuTi film was measured using X-ray diffraction (XRD), and the results showed that the RuTi film has an amorphous structure.

[0261] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuTi film of Example 15 formed as described above at a wavelength of 13.5 nm are as follows. RuTi membrane: n=0.930, k=0.015

[0262] The phase-shifting film 4 containing the RuTi film has a relative reflectance of 29.0% (absolute reflectance of 19.3%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 45.7 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 30% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0263] Secondly, compared to Example 1, the dry etching gas was changed to Cl2 gas. Otherwise, under the same conditions as in Example 1, the reflective photomask 200 was manufactured using the aforementioned reflective photomask substrate 100. In the reflective photomask 200 of Example 15, since the phase shift film 4 is made of RuTi material, although Cl2 gas was used, the dry etching time was slightly longer than in Example 1, but the processability was better, and the phase shift pattern 4a could be formed with higher precision. Furthermore, the film thickness of the phase shift pattern 4a is 45.7 nm, which is thinner than the absorber film formed from Ta-based materials previously, and the shading effect can be reduced compared to Comparative Example 1.

[0264] Furthermore, the reflective photomask 200 fabricated in Example 15 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity of the phase shift surface is 29.0% (absolute reflectivity is 19.3%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0265] Similar to Example 1, the reflective photomask 200 fabricated in Example 15 can be used to manufacture a semiconductor device with the desired characteristics.

[0266] [Example 16] Example 16 is an example in which the material of the phase shift film 4 is a RuV film, and the film thickness is adjusted to achieve a phase difference of 180 degrees. The reflective photomask substrate 100 of Example 16 is the same as that of Example 1, except that the protective film 3 is a CrOC film in the reflective photomask substrate 100 of Example 1, and a phase shift film 4 containing a RuV film is formed.

[0267] That is, in Example 16, similarly to Example 1, a back conductive film 5 containing a CrN film is formed on the second main surface (back side) of the SiO2-TiO2 glass substrate 1, and a multilayer reflective film 2 is formed on the main surface (first main surface) of the substrate 1 on the opposite side. A protective film 3 containing a CrOC film is formed by DC magnetron sputtering. The CrOC film is formed using a Cr target and reactive sputtering in a mixed gas atmosphere of Ar, CO2 and He gases to achieve a film thickness of 2.5 nm. The atomic ratio of the CrOC film is Cr:O:C = 71:15:14.

[0268] Next, a phase-shifting film 4 containing a RuV film was formed on the protective film 3 by DC magnetron sputtering. The RuV film was formed using a RuV target in an Ar gas atmosphere to a thickness of 33.0 nm. The atomic ratio of the RuV film was Ru:V = 60:40. The crystal structure of the RuV film was determined by X-ray diffraction (XRD), and the results showed that the RuV film has an amorphous structure.

[0269] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuV film of Example 16 formed as described above at a wavelength of 13.5 nm are as follows. RuV membrane: n=0.906, k=0.024

[0270] The phase-shifting film 4 containing the RuV film has a relative reflectance of 21.1% (absolute reflectance of 14.1%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 33.0 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 49% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0271] Next, using the aforementioned reflective photomask substrate 100, a reflective photomask 200 is manufactured.

[0272] First, a resist film 11 with a thickness of 100 nm is formed on the phase shift film 4 of the reflective photomask substrate 100. Then, the desired pattern is drawn (exposed) on the resist film 11, and then developed and washed to form a specific resist pattern 11a. Next, by using the resist pattern 11a as a photomask, the RuV film (phase shift film 4) is dry-etched using a mixture of CF4 gas and O2 gas (gas flow ratio CF4:O2=1:1) to form a phase shift pattern 4a.

[0273] Subsequently, the resist pattern is removed using an ashing or resist stripping solution. Finally, a wet cleaning with pure water (DIW) is performed to manufacture the reflective photomask 200. Furthermore, if necessary, a defect inspection of the photomask after wet cleaning can be performed, and appropriate defects can be corrected.

[0274] In the reflective photomask 200 of Example 16, since the phase shift film is made of RuV material, the processability of fluorine-based gases is better, and the phase shift pattern can be formed with higher precision. Furthermore, the thickness of the phase shift pattern is 33.0 nm, which is thinner than the absorber film formed by the previous Ta-based material.

[0275] Furthermore, the reflective photomask 200 fabricated in Example 16 has less sidewall roughness and a more stable cross-sectional shape due to the phase shift pattern 4a. Therefore, the LER or in-plane non-uniformity of the transferred resist pattern is less, and it has higher transfer accuracy. In addition, as mentioned above, since the relative reflectivity (reflectivity relative to the reflectivity of the multilayer reflective film surface with protective film) of the phase shift surface is 21.1% (absolute reflectivity is 14.1%), sufficient phase shift effect can be obtained, enabling EUV exposure with high exposure margin or focus margin.

[0276] The reflective photomask 200 fabricated in Example 16 is placed on an EUV scanner, and EUV exposure is performed on a wafer on a semiconductor substrate with a film to be processed and a resist film formed thereon. Then, by developing the exposed resist film, a resist pattern is formed on the semiconductor substrate with the film to be processed. The resist pattern is transferred to the film to be processed by etching. Then, through various steps such as the formation of insulating and conductive films, the introduction of dopants, and annealing, a semiconductor device with the desired characteristics can be manufactured.

[0277] [Example 17] Example 17 is an example in which the relative reflectivity of the phase shift film 4 is changed to 27% (absolute reflectivity is 18%) and the film thickness is adjusted in such a way that the phase difference is 220 degrees. Otherwise, it is the same as Example 1 and also includes the material (RuCr film).

[0278] Specifically, in Example 17, a phase shift film 4 containing a RuCr film was formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuCr film was formed using a RuCr target in an Ar gas atmosphere to achieve a film thickness of 38.6 nm. The atomic ratio of the RuCr film was Ru:Cr = 85:15. The crystal structure of the RuCr film was determined by X-ray diffraction (XRD), and the results showed that the RuCr film has an amorphous structure.

[0279] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCr film of Example 17 formed as described above at a wavelength of 13.5 nm are as follows. RuCr membrane: n=0.895, k=0.020

[0280] The phase-shifting film 4 containing the RuCr film has a relative reflectance of 27% (absolute reflectance of 18%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 38.6 nm. This thickness corresponds to a phase difference of 220 degrees when the phase-shifting film 4 is patterned. This is approximately 41% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0281] Secondly, under the same conditions as in Example 1, a reflective photomask 200 was fabricated using the aforementioned reflective photomask substrate 100. Furthermore, the film thickness of the phase shift pattern 4a is 38.6 nm, which is thinner than the absorber film formed from the previous Ta-based material, thus reducing the shadowing effect compared to Comparative Example 1. Also, compared to the reflective photomask fabricated using the same material as in Example 17 and adjusted to a relative reflectivity of 27% (absolute reflectivity of 18%) and a phase difference of 180 degrees, the contrast is improved by 1.3 times.

[0282] Similar to Example 1, the reflective photomask 200 fabricated in Example 17 can be used to manufacture a semiconductor device with the desired characteristics.

[0283] [Example 18] Example 18 is an example in which the relative reflectivity of the phase shift film 4 is changed to 20% (absolute reflectivity is 13.3%) and the film thickness is adjusted in such a way that the phase difference is 140 degrees. Otherwise, it is the same as Example 1 and also includes the material (RuCr film).

[0284] Specifically, in Example 18, a phase shift film 4 containing a RuCr film was formed on a substrate with a protective film 3 containing a SiO2 film and a multilayer reflective film by DC magnetron sputtering. The RuCr film was formed using a RuCr target in an Ar gas atmosphere to achieve a film thickness of 30.4 nm. The atomic ratio of the RuCr film was Ru:Cr = 66:34. The crystal structure of the RuCr film was determined by X-ray diffraction (XRD), and the results showed that the RuCr film has an amorphous structure.

[0285] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCr film of Example 18 formed as described above at a wavelength of 13.5 nm are as follows. RuCr membrane: n=0.916, k=0.031

[0286] The phase-shifting film 4 containing the RuCr film has a relative reflectance of 20% (absolute reflectance of 13.3%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 30.4 nm. This thickness corresponds to a phase difference of 140 degrees when the phase-shifting film 4 is patterned. This is approximately 53% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0287] Secondly, under the same conditions as in Example 1, a reflective photomask 200 was fabricated using the aforementioned reflective photomask substrate 100. Furthermore, the phase shift pattern 4a has a film thickness of 30.4 nm, which is thinner than the previous absorber film formed from Ta-based materials, thus reducing the shadowing effect compared to Comparative Example 1. Also, compared to the reflective photomask fabricated using the same material as in Example 18 and adjusted to a relative reflectivity of 20% (absolute reflectivity of 13.3%) and a phase difference of 180 degrees, the contrast ratio is increased by 1.5 times.

[0288] Similar to Example 1, the reflective photomask 200 fabricated in Example 18 can be used to manufacture a semiconductor device with the desired characteristics.

[0289] [Example 19] Example 19 is an example in which the thickness of the protective film is changed, the material of the phase shift film 4 is set to RuCrN film, and the film thickness is adjusted in such a way that the phase difference is 180 degrees. Otherwise, it is the same as Example 1.

[0290] Specifically, in Example 18, a phase shift film 4 containing a RuCrN film was formed on a substrate with a multilayer reflective film and a protective film 3 containing a SiO2 film with a thickness of 3.2 nm on it by DC magnetron sputtering. The RuCrN film was formed using a Ru target and a Cr target in an Ar gas and N2 gas atmosphere to achieve a film thickness of 34.6 nm. The atomic ratio of the RuCrN film was Ru:Cr:N = 55:38:7. The crystal structure of the RuCrN film was determined by X-ray diffraction (XRD), and the result showed that the RuCrN film has an amorphous structure.

[0291] The refractive index n and extinction coefficient (imaginary part of refractive index) k of the RuCrN film of Example 19 formed as described above at a wavelength of 13.5 nm are as follows. RuCr membrane: n=0.905, k=0.025

[0292] The phase-shifting film 4 containing the RuCrN film has a relative reflectance of 16% (absolute reflectance of 10.7%) at a wavelength of 13.5 nm. Furthermore, the phase-shifting film 4 has a thickness of 34.6 nm. This thickness corresponds to a phase difference of 180 degrees when the phase-shifting film 4 is patterned. This is approximately 47% thinner than the 65 nm thickness of the phase-shifting film 4 of the TaN film in Comparative Example 1 below.

[0293] Secondly, under the same conditions as in Example 1, a reflective photomask 200 was fabricated using the aforementioned reflective photomask substrate 100. Furthermore, the phase shift pattern 4a has a film thickness of 34.6 nm, which is thinner than the absorber film formed from the previous Ta-based material, and can reduce the shadowing effect compared to Comparative Example 1.

[0294] Similar to Example 1, the reflective photomask 200 fabricated in Example 19 can be used to manufacture a semiconductor device with the desired characteristics.

[0295] [Comparative Example 1] In Comparative Example 1, a Ru film was used as the protective film 3, and a single-layer TaN film was used as the phase shift film 4. Otherwise, a reflective photomask substrate 100 and a reflective photomask 200 were manufactured using the same structure and method as in Example 1. Furthermore, a semiconductor device was manufactured using the same method as in Example 1.

[0296] A Ru film (protective film 3) is formed on the multilayer reflective film 2 of the photomask substrate structure of Example 1. This Ru film is formed by using Ru as a target and depositing it in an Ar gas atmosphere using ion beam sputtering to a thickness of 2.5 nm. A monolayer TaN film is formed on the Ru film. This TaN film is formed by using Ta as a target and performing reactive sputtering in a mixed gas atmosphere of Xe and N2. The TaN film has a thickness of 65 nm, and the elemental composition of the film is 88 atomic% Ta and 12 atomic% N.

[0297] 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 are as follows. TaN film: n=0.949, k=0.032

[0298] The phase shift film 4, which includes a single-layer TaN film, has a phase difference of 180 degrees at a wavelength of 13.5 nm. Its relative reflectivity to the two surfaces of the multilayer reflective film is 1.7%. Furthermore, the absolute reflectivity of the phase shift film 4 is 1.1%.

[0299] Subsequently, using the same method as in Example 1, a resist film 11 is formed on a phase shift film 4 comprising a monolayer TaN film, and the desired pattern is drawn (exposed), developed, and washed to form a resist pattern 11a. Furthermore, using this resist pattern 11a as a photomask, the phase shift film 4 comprising a monolayer TaN film is dry-etched using chlorine gas to form a phase shift pattern 4a. The removal of the resist pattern 11a or the cleaning of the photomask is also performed using the same method as in Example 1, thereby manufacturing a reflective photomask 200.

[0300] The phase-shift pattern 4a has a film thickness of 65 nm, which cannot reduce the shadowing effect. In addition, as mentioned above, since the relative reflectance of the phase-shift surface is 1.7% (absolute reflectance is 1.1%), a sufficient phase-shifting effect cannot be obtained, and EUV exposure with high exposure margin or focus margin cannot be performed.

[0301] As described above, the total thickness of the phase shift film 4 in Examples 1 to 19 is about 30% thinner than the 65 nm thickness of the phase shift film 4 in Comparative Example 1. Therefore, it is obvious that the shadowing effect can be reduced in the reflective photomask 200 of Examples 1 to 19.

[0302] 1:Substrate 2: Multilayer reflective film 3: Protective film 4: Phase shifting film 4a: Phase shift pattern 5: Back conductive film 11: Anti-corrosion film 11a: Anti-corrosion pattern 100: Reflective photomask substrate 200: Reflective photomask

Claims

1. A reflective photomask substrate, characterized in that: it comprises, sequentially having, multiple reflective films and phase-shifting films on a substrate, wherein the relative reflectivity of the phase-shifting films is 6% to 40%, the phase-shifting films comprise a thin film containing ruthenium (Ru) and at least one element selected from cobalt (Co), titanium (Ti), niobium (Nb), molybdenum (Mo) and rhenium (Re), and when the thin film contains Co, the composition ratio of Ru to Co (Ru:Co) is 20:1 to 1:5; when the thin film contains Ti, the composition ratio of Ru to Ti (Ru:Ti) is 20:1 to 1:20; when the thin film contains Nb, the composition ratio of Ru to Nb (Ru:Nb) is 20:1 to 5:1; when the thin film contains Mo, the composition ratio of Ru to Mo (Ru:Mo) is 20:1 to 4:1; and when the thin film contains Re, the composition ratio of Ru to Re (Ru:Re) is 20:1 to 1:

20.

2. A reflective photomask substrate, characterized in that: it comprises, sequentially having, multiple reflective films and phase-shifting films on a substrate, wherein the phase difference of the phase-shifting films is 130°–160° or 200°–230°, the phase-shifting films comprising a thin film containing ruthenium (Ru) and at least one element selected from cobalt (Co), titanium (Ti), niobium (Nb), molybdenum (Mo), and rhenium (Re), wherein when the thin film contains Co, the composition ratio of Ru to Co (Ru:Co) is 20:1–1:5; when the thin film contains Ti, the composition ratio of Ru to Ti (Ru:Ti) is 20:1–1:20; when the thin film contains Nb, the composition ratio of Ru to Nb (Ru:Nb) is 20:1–5:1; and when the thin film contains Mo, the composition ratio of Ru to Mo (Ru:Mo) is 20:1–4:

1. When the above-mentioned film contains Re, the composition ratio of Ru to Re (Ru:Re) is 20:1 to 1:

20.

3. A reflective photomask substrate, characterized in that: it comprises, sequentially having, multiple reflective films and phase-shifting films on a substrate, wherein the phase-shifting films comprise a thin film containing ruthenium (Ru) and at least one element selected from cobalt (Co), titanium (Ti), niobium (Nb), molybdenum (Mo), and rhenium (Re), and when the thin film contains Co, the composition ratio of Ru to Co (Ru:Co) is 20:1 to 1:5, and the film thickness is 40 nm or less; when the thin film contains Ti, the composition ratio of Ru to Ti (Ru:Ti) is 20:1 to 1:20, and the film thickness is 66 nm or less; when the thin film contains Nb, the composition ratio of Ru to Nb (Ru:Nb) is 20:1 to 5:1, and the film thickness is 32 nm or less; when the thin film contains Mo, the composition ratio of Ru to Mo (Ru:Mo) is 20:1 to 4:1, and the film thickness is 33 nm or less. When the above-mentioned thin film contains Re, the composition ratio of Ru to Re (Ru:Re) is 20:1 to 1:20, and the film thickness is less than 38 nm.

4. The reflective photomask substrate of any one of claims 1 to 3, wherein the crystalline structure of the aforementioned thin film is amorphous.

5. The reflective photomask substrate of any one of claims 1 to 3, wherein the refractive index n of the thin film is 0.860 to 0.950 and the extinction coefficient k is 0.008 to 0.

095.

6. A reflective photomask, characterized in that it has a phase shift pattern formed by patterning the aforementioned phase shift film in the reflective photomask substrate as described in any one of claims 1 to 5.

7. A method for manufacturing a reflective photomask, characterized in that: the phase shift film of the reflective photomask substrate as claimed in any one of claims 1 to 5 is patterned by a dry etching gas containing chlorine gas and oxygen to form a phase shift pattern.

8. A method for manufacturing a semiconductor device, characterized by comprising the following steps: setting a reflective photomask as claimed in claim 6 on an exposure apparatus having an exposure light source emitting EUV light, and transferring a transfer pattern onto a resist film formed on a substrate to be transferred.

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