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

Abstract

To provide a reflection type mask blank for manufacturing a reflection type mask which can suppress peeling of an absorber pattern, while suppressing an increase in thickness of an absorber film, when EUV exposure is performed in an atmosphere containing hydrogen gas.SOLUTION: A reflection type mask blank includes a substrate, a multilayered reflection film on the substrate, and an absorber film on the multilayered reflection film. The absorber film includes an absorption layer and a reflectance adjustment layer. The absorption layer contains at least one addition element selected from tantalum (Ta), nitrogen (N), hydrogen (H), and deuterium (D). The absorption layer includes a lower surface region including the surface on the substrate side and an upper surface region including a surface on a side opposite to the substrate. A concentration (atom%) of the addition element in the lower surface region and a concentration (atom%) of the addition element in the upper surface region are different.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a reflective mask used in the manufacture of semiconductor devices and the like, and a reflective mask blank used for manufacturing the reflective mask. The present invention also relates to a method for manufacturing a semiconductor device using the above reflective mask.

Background Art

[0002] The types of light sources of exposure apparatuses in semiconductor device manufacturing have evolved while gradually shortening the wavelength, including g-line with a wavelength of 436 nm, i-line with a wavelength of 365 nm, KrF laser with a wavelength of 248 nm, ArF laser with a wavelength of 193 nm, and extreme ultraviolet light (EUV: Extreme Ultra Violet) with a wavelength near 13.5 nm. In order to achieve finer pattern transfer, EUV lithography using EUV light has been developed. In EUV lithography, since there are few materials transparent to EUV light, a reflective mask is used. This reflective mask has a mask structure having a low thermal expansion substrate, a multilayer reflective film, a protective film, and a transfer pattern as a basic structure. A multilayer reflective film that reflects exposure light is formed on the low thermal expansion substrate. A protective film for protecting the multilayer reflective film is formed on the multilayer reflective film. A desired transfer pattern is formed on the protective film. Also, as typical transfer patterns, there are a binary type reflective mask composed of a relatively thick absorber pattern that sufficiently absorbs EUV light, and a phase shift type reflective mask (halftone phase shift type reflective mask) composed of a relatively thin absorber pattern that attenuates EUV light by light absorption and generates reflected light with a substantially inverted phase (phase inversion of about 180°) with respect to the reflected light from the multilayer reflective film. This phase shift type reflective mask, like a transmissive optical phase shift mask, can obtain a high transfer optical image contrast due to the phase shift effect. Therefore, the phase shift type reflective mask has an effect of improving resolution. Also, since the film thickness of the absorber pattern (phase shift pattern) of the phase shift type reflective mask is thin, a fine phase shift pattern can be formed with high accuracy.

[0003] Such reflective masks for EUV lithography and technologies related to mask blanks for fabricating them are disclosed in Patent Documents 1 and 2.

[0004] Patent Document 1 describes a reflective mask blank for EUV lithography, in which at least a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed on a substrate in that order. Specifically, the reflective mask blank of Patent Document 1 is described in which the absorber layer contains tantalum (Ta), nitrogen (N), and hydrogen (H), with the total content of Ta and N in the absorber layer being 50 to 99.9 at%, and the content of H being 0.1 to 50 at%. Patent Document 1 is described in which the reflective mask blank of Patent Document 1 has an amorphous crystalline state for the film of the absorber layer, and also reduces stress and surface roughness.

[0005] Furthermore, Patent Document 2 describes a reflective mask blank for EUV lithography in which a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed on a substrate in that order. Specifically, the reflective mask blank of Patent Document 2 is described in which the absorber layer contains at least tantalum (Ta), boron (B), nitrogen (N), and hydrogen (H), and in the absorber layer, the content of B is 1 at% or more and less than 5 at%, the content of H is 0.1 to 5 at%, the total content of Ta and N is 90 to 98.9 at%, and the composition ratio of Ta to N (Ta:N) is 8:1 to 1:1. As a result, in the reflective mask blank of Patent Document 2, the crystalline state of the absorber layer film becomes amorphous, and stress and surface roughness are also reduced. Furthermore, Patent Document 2 states that the reflective mask blank of Patent Document 2 has a low B content in the absorber layer (less than 5 at%), and therefore does not cause problems such as a decrease in the film deposition rate or unstable discharge during film deposition when depositing the absorber layer. Specifically, Patent Document 2 states that there is no risk of problems such as variations in film composition or film thickness, or even the inability to deposit the film at all. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2009 / 116348 [Patent Document 2] International Publication No. 2010 / 050518 [Disclosure of the Invention]

[0007] In EUV lithography, exposure contamination, such as the deposition of carbon films on reflective masks due to EUV exposure, is known to occur. To suppress this, a technique of introducing hydrogen gas into the exposure atmosphere has been adopted in recent years.

[0008] As disclosed in Patent Documents 1 and 2, tantalum (Ta) has conventionally been used as a material for forming absorber films in reflective mask blanks. However, when EUV exposure is performed in an atmosphere containing hydrogen gas, a problem can occur in which the absorber pattern peels off. The reason for this problem is thought to be as follows: During EUV exposure, hydrogen gas in the exposure atmosphere containing hydrogen gas is absorbed by the absorber pattern as atomic hydrogen (H), causing the volume of the absorber pattern to expand and increasing the compressive stress. As a result, cracks occur at the interface with weak adhesion in the thin film (e.g., protective film) placed on the substrate side of the absorber pattern. When a protective film is placed on the substrate side of the absorber pattern, hydrogen may also penetrate the protective film. When hydrogen penetrates the protective film, many cracks may occur at the interface between the protective film and the multilayer reflective film. It is thought that atomic hydrogen (H) gathers in the space of the generated cracks and becomes hydrogen gas, causing the space to expand and peel off the absorber pattern.

[0009] Furthermore, when addressing the issue of absorber pattern peeling due to changes in the absorber film material, it is necessary to ensure that the extinction coefficient k of the absorber film does not become too low. If the extinction coefficient k of the absorber film becomes too low, it becomes necessary to thicken the absorber film to ensure the absorption of the required EUV light by the absorber film. However, if the absorber film is thickened, another problem arises: the shadowing effect of the reflective mask prevents the formation of fine patterns.

[0010] Therefore, the present invention aims to provide a reflective mask that can suppress the thickening of the absorber film and prevent the peeling of the absorber pattern when EUV exposure is performed in an atmosphere containing hydrogen gas. The present invention also aims to provide a reflective mask blank for manufacturing a reflective mask that can suppress the peeling of the absorber pattern.

[0011] The inventors have discovered that by pre-containing hydrogen in the absorber membrane, it is possible to eliminate the possibility of new atomic hydrogen (H) entering the absorber membrane and suppress the peeling of the absorber pattern. More specifically, they have found that by suppressing membrane stress fluctuations due to hydrogen intrusion into the absorber pattern, it is possible to prevent the absorber pattern from becoming prone to peeling or from actually peeling off. When the absorber membrane contains hydrogen, the membrane density of the absorber membrane decreases, resulting in a lower extinction coefficient k. This leads to another problem: the absorber membrane becomes thicker. Therefore, the inventors have discovered that by changing the hydrogen content of the absorber membrane in the direction of film thickness, it is possible to prevent the peeling of the absorber pattern while suppressing the thickening of the absorber membrane, leading to the present invention.

[0012] To solve the above problems, the present invention has the following configuration.

[0013] (Composition 1) Configuration 1 of the present invention is a reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, and an absorbent film on the multilayer reflective film, The absorbent membrane includes an absorption layer and a reflectance adjusting layer. The absorption layer comprises tantalum (Ta) and nitrogen (N), and at least one additive element selected from hydrogen (H) and deuterium (D). The absorption layer includes a lower surface region including the surface on the substrate side and an upper surface region including the surface on the opposite side from the substrate. This reflective mask blank is characterized in that the concentration (atomic %) of the additive element in the lower surface region is different from the concentration (atomic %) of the additive element in the upper surface region.

[0014] (Configuration 2) Configuration 2 of the present invention is a reflective mask blank of Configuration 1, characterized in that the concentration (atomic %) of the additive element in the lower surface region is higher than the concentration (atomic %) of the additive element in the upper surface region.

[0015] (Composition 3) Configuration 3 of the present invention is a reflective mask blank of Configuration 1, characterized in that the concentration (atomic %) of the additive element in the upper surface region is higher than the concentration (atomic %) of the additive element in the lower surface region.

[0016] (Composition 4) Configuration 4 of the present invention is a reflective mask blank according to any of Configurations 1 to 3, characterized in that the content of the additive element in the absorption layer is 0.1 atomic% or more and 30 atomic% or less.

[0017] (Composition 5) Configuration 5 of the present invention is a reflective mask blank according to any of configurations 1 to 4, characterized in that the reflectance adjustment layer contains tantalum (Ta) and oxygen (O), and at least one additive element selected from hydrogen (H) and deuterium (D).

[0018] (Composition 6) Configuration 6 of the present invention is a reflective mask blank according to any of configurations 1 to 5, characterized in that it includes a protective film between the multilayer reflective film and the absorber film, and the protective film contains ruthenium (Ru) and at least one additive element selected from hydrogen (H) and deuterium (D).

[0019] (Configuration 7) Configuration 7 of the present invention is a reflective mask characterized in that the absorber pattern in any one of the reflective mask blanks of Configurations 1 to 6 has an absorber film that is patterned.

[0020] (Configuration 8) Configuration 8 of the present invention is a method for manufacturing a reflective mask, characterized by patterning the absorber film of any one of the reflective mask blanks of Configurations 1 to 6 to form an absorber pattern.

[0021] (Configuration 9) Configuration 9 of the present invention is a method for manufacturing a semiconductor device, characterized by having a step of setting the reflective mask of Configuration 7 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.

[0022] According to the present invention, when performing EUV exposure in an atmosphere containing hydrogen gas, it is possible to provide a reflective mask that can suppress the thickening of the absorber film and suppress the peeling of the absorber pattern. Further, according to the present invention, it is possible to provide a reflective mask blank for manufacturing a reflective mask that can suppress the peeling of the absorber pattern.

Brief Description of the Drawings

[0023] [Figure 1] It is a schematic cross-sectional view of a main part for explaining the schematic configuration of an embodiment of the reflective mask blank of the present invention. [Figure 2] It is a schematic cross-sectional view of a main part for explaining the schematic configuration of another embodiment of the reflective mask blank of the present invention. [Figure 3A-E] It is an example of a process diagram showing, in a schematic cross-sectional view of a main part, the process of manufacturing a reflective mask from a reflective mask blank. [Figure 4A-E] It is another example of a process diagram showing, in a schematic cross-sectional view of a main part, the process of manufacturing a reflective mask from a reflective mask blank.

Embodiments for Carrying Out the Invention

[0024] The embodiments of the present invention will be described in detail below with reference to the drawings. The following embodiments are merely examples of how the present invention can be implemented, and do not limit the present invention to their scope. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and their descriptions may be simplified or omitted.

[0025] <Structure of reflective mask blank 100 and method for manufacturing the same> Figure 1 is a schematic cross-sectional view of the main parts illustrating the configuration of a reflective mask blank 100 according to an embodiment of the present invention. As shown in Figure 1, the reflective mask blank 100 of this embodiment includes a substrate 1, a multilayer reflective film 2 that reflects EUV light, which is exposure light, formed on the first main surface (front surface) side, and an absorber film 4 that absorbs EUV light formed on the multilayer reflective film 2, which are stacked in this order. In the reflective mask blank 100 of this embodiment, the absorber film 4 includes an absorption layer 42 and a reflectance adjustment layer 44 provided on the absorption layer 42. The absorption layer 42 has a lower surface region 46 that includes the surface on the substrate 1 side and an upper surface region 48 that includes the surface opposite to the substrate 1. Furthermore, the reflective mask blank 100 of this embodiment shown in Figure 1 may further include a protective film 3 provided between the multilayer reflective film 2 and the absorber film 4 to protect the multilayer reflective film 2. In addition, a back surface conductive film 5 for an electrostatic chuck can be formed on the second main surface (back surface) side of the substrate 1.

[0026] Figure 2 shows a reflective mask blank 100 of another embodiment. As shown in Figure 2, the reflective mask blank 100 of this embodiment may further have an etching mask film 6 formed on the absorber film 4.

[0027] Furthermore, the reflective mask blank 100 of other embodiments includes a configuration in which the back surface conductive film 5 is not formed. In addition, the reflective mask blank 100 also includes a configuration of a mask blank with a resist film in which a resist film 11 is formed on the etching mask film 6.

[0028] In this specification, for example, the phrase "multilayer reflective film 2 formed on substrate 1" or "multilayer reflective film 2 on substrate 1" means not only that the multilayer reflective film 2 is positioned in contact with the surface of substrate 1, but also that there is another film between substrate 1 and the multilayer reflective film 2. The same applies to other films. Furthermore, in this specification, for example, "film A is positioned in contact with film B" means that film A and film B are positioned in direct contact without any other film in between.

[0029] In this specification, hydrogen (H) and / or deuterium (D) contained in the thin film such as the absorber film 4 of the reflective mask blank 100 of this embodiment are referred to as "additive elements." Furthermore, since hydrogen (H) and deuterium (D) exhibit similar properties, unless otherwise specified, some or all of the hydrogen (H) constituting a given thin film can be replaced with deuterium (D).

[0030] The following provides a detailed explanation of each component of the reflective mask blank 100.

[0031] <<Circuit Board 1>> To prevent distortion of the absorber pattern 4a due to heat during exposure with EUV light, the substrate 1 is preferably made of a material with a low thermal expansion coefficient in the range of 0 ± 5 ppb / °C. Examples of materials with a low thermal expansion coefficient in this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0032] The first main surface of the substrate 1 on the side where the transfer pattern (which is composed of the patterned absorber film 4 described later) is formed is surface-processed to achieve high flatness, at least from the viewpoint of obtaining pattern transfer accuracy and positional accuracy. 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 particularly preferably 0.03 μm or less. The second main surface on the side opposite to the side where the absorber film 4 is formed is the surface that is electrostatically chucked when set in the exposure apparatus, and the flatness of the 142 mm × 142 mm area is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less.

[0033] Furthermore, the surface smoothness of the substrate 1 is also an extremely important factor. The surface roughness of the first main surface of the substrate 1 on which the transfer absorber pattern 4a is formed is preferably 0.1 nm or less in terms of root mean square roughness (RMS). Surface smoothness can be measured using an atomic force microscope.

[0034] Furthermore, the substrate 1 is preferably made of high rigidity in order to prevent deformation due to film stress of the film (such as the multilayer reflective film 2) formed thereon. In particular, it is preferable that it has a high Young's modulus of 65 GPa or more.

[0035] <<Multilayer reflective film 2>> The multilayer reflective film 2 provides the reflective mask 200 with the function of reflecting EUV light. The multilayer reflective film 2 is a multilayer film in which layers, each mainly composed of elements with different refractive indices, are periodically stacked.

[0036] Generally, a multilayer film is used as the multilayer reflective film 2, in which thin films of light elements or compounds thereof, which are high refractive index materials (high refractive index layers), and thin films of heavy elements or compounds thereof, which are low refractive index materials, are alternately stacked for about 40 to 60 periods. The multilayer film may be stacked in multiple periods, with a high refractive index layer / low refractive index layer stacking structure, where the high refractive index layer and the low refractive index layer are stacked in this order from the substrate 1 side, as one period, or it may be stacked in multiple periods, with a low refractive index layer / high refractive index layer stacking structure, where the low refractive index layer and the high refractive index layer are stacked in this order from the substrate 1 side, as one period. It is preferable that the outermost layer of the multilayer reflective film 2, i.e., the surface layer of the multilayer reflective film 2 opposite to the substrate 1, be a high refractive index layer. In the above-described multilayer film, when a high refractive index layer / low refractive index layer stacking structure, where the high refractive index layer and the low refractive index layer are stacked in this order from the substrate 1, is stacked in multiple periods, the uppermost layer becomes a low refractive index layer. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 2, it will be easily oxidized, and the reflectivity of the reflective mask 200 will decrease. Therefore, it is preferable to further form a high refractive index layer on the uppermost low refractive index layer to form a multilayer reflective film 2. On the other hand, in the above-described multilayer film, if a low refractive index layer and a high refractive index layer are stacked in this order from the substrate 1 side, and multiple periods of stacking are performed with this low refractive index layer / high refractive index layer structure as one period, the uppermost layer will be the high refractive index layer, so it is fine as is.

[0037] In this embodiment, a layer containing silicon (Si) is used as the high refractive index layer. The Si-containing material may be Si alone, or a Si compound containing boron (B), carbon (C), nitrogen (N), and oxygen (O). By using the Si-containing layer as the high refractive index layer, a reflective mask 200 for EUV lithography with excellent EUV light reflectivity can be obtained. In this embodiment, a glass substrate is preferably used as the substrate 1. Si also exhibits excellent adhesion to the glass substrate. Furthermore, a metal element selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof, can be used as the low refractive index layer. For example, as the multilayer reflective film 2 for EUV light with wavelengths of 13 nm to 14 nm, a Mo / Si periodic multilayer film is preferably used, in which Mo films and Si films are alternately stacked for approximately 40 to 60 periods. Alternatively, the uppermost high-refractive-index layer of the multilayer reflective film 2 may be formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen may be formed between the uppermost layer (Si) and the Ru-based protective film 3. This can improve the mask's resistance to washing.

[0038] The reflectivity of such a multilayer reflective film 2 on its own is typically 65% ​​or higher, with an upper limit of typically 73%. The thickness and period of each constituent layer of the multilayer reflective film 2 can be appropriately selected according to the exposure wavelength, and are chosen to satisfy Bragg's law of reflection. In the multilayer reflective film 2, there are multiple high-refractive-index layers and multiple low-refractive-index layers, but the thicknesses of the high-refractive-index layers and the low-refractive-index layers do not have to be the same. In addition, the thickness of the Si layer on the outermost surface of the multilayer reflective film 2 can be adjusted within a range that does not reduce the reflectivity. The thickness of the outermost Si (high-refractive-index layer) can be from 3 nm to 10 nm.

[0039] 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 Mo / Si periodic multilayer film described above, for example, using an ion beam sputtering method, first a Si film with a thickness of about 4 nm is deposited on the substrate 1 using a Si target, and then a Mo film with a thickness of about 3 nm is deposited using a Mo target. The Si and Mo films deposited in this way constitute one period, and 40 to 60 periods are stacked to form the multilayer reflective film 2 (the outermost layer is the Si layer). Furthermore, it is preferable to form the multilayer reflective film 2 by supplying krypton (Kr) ion particles from an ion source and performing ion beam sputtering during the deposition of the multilayer reflective film 2.

[0040] <<Protective film 3>> In this embodiment, it is preferable that the reflective mask blank 100 has a protective film 3 between the multilayer reflective film 2 and the absorber film 4. By forming the protective film 3 on the multilayer reflective film 2, damage to the surface of the multilayer reflective film 2 when manufacturing a reflective mask 200 (EUV mask) using the reflective mask blank 100 can be suppressed. As a result, the reflectivity characteristics for EUV light are improved.

[0041] The protective film 3 is formed on the multilayer reflective film 2 to protect it from dry etching and cleaning during the manufacturing process of the reflective mask 200, which will be described later. The protective film 3 also serves to protect the multilayer reflective film 2 during black defect correction of the absorber pattern 4a using an electron beam (EB). The protective film 3 is made of a material that is resistant to etchants and cleaning solutions. Here, Figure 1 shows the case where the protective film 3 is a single layer, but it can also be a laminated structure of three or more layers. For example, the bottom layer and the top layer may be made of the material containing Ru, and a protective film 3 may have a metal or alloy other than Ru interposed between the bottom layer and the top layer. For example, the protective film 3 can also be made of a material mainly composed of ruthenium. In other words, the material of the protective film 3 may be pure Ru metal, or it may be a Ru alloy containing Ru and at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and rhenium (Re), and may also contain nitrogen. Such a protective film 3 is particularly effective when the absorption layer 42 of the absorber film 4 is patterned by dry etching with a chlorine-based gas (Cl-based gas). It is preferable that the protective film 3 is formed from a material such that the etching selectivity ratio of the absorber film 4 to the protective film 3 (etching rate of the absorber film 4 / etching rate of the protective film 3) in dry etching using a chlorine-based gas is 1.5 or higher, preferably 3 or higher.

[0042] The Ru content of this Ru alloy is 50 atomic% or more and less than 100 atomic%, preferably 80 atomic% or more and less than 100 atomic%, and more preferably 95 atomic% or more and less than 100 atomic%. In particular, when the Ru content of the Ru alloy is 95 atomic% or more and less than 100 atomic%, it is possible to suppress the diffusion of elements (silicon) constituting the multilayer reflective film 2 into the protective film 3, while ensuring sufficient reflectivity of EUV light, and to combine mask washing resistance, etching stopper function when the absorber film 4 is etched, and protective film function to prevent deterioration of the multilayer reflective film 2 over time.

[0043] The protective film 3 of the reflective mask blank 100 in this embodiment preferably contains ruthenium (Ru) and at least one additive element selected from hydrogen (H) and deuterium (D). When the protective film 3 contains an additive element (hydrogen (H) and / or deuterium (D)), the total content of the additive element is preferably more than 5 atomic percent, and more preferably 10 atomic percent or more. By having the protective film 3 between the multilayer reflective film 2 and the absorber film 4, damage to the surface of the multilayer reflective film 2 when manufacturing a reflective mask 200 using the reflective mask blank 100 can be suppressed. Furthermore, by using a predetermined material as the material for the protective film 3, the adhesion between the multilayer reflective film 2 and the absorber film 4 can be further improved. Therefore, peeling of the protective film 3 and the absorber pattern 4a can be more reliably suppressed. Moreover, by the protective film 3 containing at least one additive element selected from hydrogen (H) and deuterium (D), peeling of the film caused by the interface of the protective film 3 can be suppressed.

[0044] Furthermore, if the total content of additive elements (hydrogen (H) and / or deuterium (D)) in the protective film 3 is greater than the total content of additive elements in the absorption layer 42, the total content of hydrogen (H) or deuterium (D) in the protective film 3 does not necessarily have to be more than 5 atomic percent, but can be 5 atomic percent or less.

[0045] Furthermore, according to the inventors' findings, if the total content of the additive elements (hydrogen (H) and / or deuterium (D)) in the protective film 3 is greater than 5 atomic percent, it may be possible to sufficiently prevent film peeling caused by the interface of the protective film 3. In that case, it may not be necessary to include the additive elements in the absorber film 4, or a low concentration of the additive elements may suffice.

[0046] In other words, the reflective mask blank 100 in this embodiment is a reflective mask blank 100 having a multilayer reflective film 2, a protective film 3, and an absorber film 4 on a substrate 1 in this order. The absorber film 4 of this reflective mask blank 100 contains tantalum (Ta) and at least one additive element selected from hydrogen (H) and deuterium (D). The protective film 3 of this reflective mask blank 100 contains ruthenium (Ru) and at least one additive element selected from hydrogen (H) and deuterium (D). The content of the additive element in the protective film 3 of this reflective mask blank 100 is more than 5 atomic percent. By using such a reflective mask blank 100, peeling of the absorber pattern 4a of the reflective mask 200 can also be suppressed.

[0047] In EUV lithography, since there are few materials that are transparent to exposure light, the EUV pellicle, which prevents foreign matter from adhering to the mask pattern surface, is not technically easy to manufacture. For this reason, pellicle-less operation is the mainstream. In addition, exposure contamination occurs in EUV lithography, such as the deposition of carbon films or the growth of oxide films on the mask due to EUV exposure. Therefore, when using the EUV reflective mask 200 in the manufacturing of semiconductor devices, it is necessary to frequently clean the mask to remove foreign matter and contamination. For this reason, the EUV reflective mask 200 requires a level of mask cleaning resistance that is orders of magnitude higher than that of transmissive masks used for photolithography. By using a Ru-based protective film 3 containing Ti, the mask can meet the requirements for mask cleaning resistance by exhibiting particularly high cleaning resistance to cleaning solutions such as sulfuric acid, sulfuric acid hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, or ozone water with a concentration of 10 ppm or less.

[0048] The thickness of the protective film 3, which is composed of Ru or an alloy thereof, is not particularly limited as long as it can perform its function as a protective film 3. From the viewpoint of EUV light reflectance, 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.

[0049] The method for forming the protective film 3 can be any known film formation method without any particular limitations. Specific examples include sputtering and ion beam sputtering.

[0050] <<Absorbing membrane 4>> In the reflective mask blank 100 of this embodiment, an absorber film 4 that absorbs EUV light is formed on the multilayer reflective film 2 (or on the protective film 3 if a protective film 3 is formed). The absorber film 4 has the function of absorbing EUV light. The absorber film 4 of this embodiment has an absorption layer 42 and a reflectance adjustment layer 44 provided on the absorption layer 42 (on the surface of the absorption layer 42 opposite to the substrate 1).

[0051] The absorber film 4 of this embodiment has an absorption layer 42. The absorption layer 42 contains tantalum (Ta) and nitrogen (N), and at least one additive element selected from hydrogen (H) and deuterium (D). By pre-containing additive elements such as hydrogen in the absorber film 4, when EUV exposure is performed in an atmosphere containing hydrogen gas, it is possible to obtain a reflective mask 200 that eliminates the possibility of new atomic hydrogen (H) entering the absorber film and suppresses the peeling of the absorber pattern 4a.

[0052] As shown in Figures 1 and 2, the absorption layer 42 of the reflective mask blank 100 in this embodiment includes a lower region 46 that includes the surface on the substrate 1 side and an upper region 48 that includes the surface on the opposite side of the substrate 1. In this embodiment, the concentration (atomic %) of the additive element in the lower region 46 of the absorption layer 42 is different from the concentration (atomic %) of the additive element in the upper region 48. By adding the additive element at a higher concentration to the required part of the absorber film (lower region 46 or upper region 48), a decrease in the film density of the absorber film can be prevented, thereby suppressing the thickening of the absorber film. Therefore, by changing the hydrogen content of the absorber film 4 in the film thickness direction, a reflective mask 200 can be obtained that suppresses the thickening of the absorber film 4 while suppressing the peeling of the absorber pattern 4a when EUV exposure is performed in an atmosphere containing hydrogen gas.

[0053] In this specification, the layer of the absorption layer 42 that includes the lower surface region 46 may be referred to as the lower layer. Similarly, the layer that includes the upper surface region 48 may be referred to as the upper layer. Furthermore, an intermediate region may be included between the lower layer and the upper layer. In the examples in Figures 1 and 2, the lower layer is identical to the lower surface region 46, the upper layer is identical to the upper surface region 48, and there is no intermediate region.

[0054] The lower region 46 is the region of the absorption layer 42 of the absorber film 4 that includes the surface on the substrate 1 side. In the examples shown in Figures 1 and 2, the lower region 46 includes the surface (interface) of the absorption layer 42 of the absorber film 4 that is in contact with the protective film 3 (referred to as the "lower surface" in this specification), and the region near that surface. The upper region 48 is the region of the absorption layer 42 of the absorber film 4 that includes the surface opposite to the substrate 1 (referred to as the "upper surface" in this specification), one of the two surfaces (interfaces). In the examples shown in Figures 1 and 2, the upper region 48 includes the surface of the absorber film 4 that is in contact with the reflectance adjustment layer 44, and the region near that surface. The absorption layer 42 can have only these two regions: the lower region 46 and the upper region 48. In this case, the lower region 46 corresponds to the lower layer, and the upper region 48 corresponds to the upper layer. The absorption layer 42 may also include an intermediate region (not shown) between the lower region 46 and the upper region 48. The lower region 46 and the upper region 48 have different concentrations of the added elements. However, the ratio of the concentrations of elements other than the added elements, particularly tantalum (Ta) and nitrogen (N), can be basically the same. However, the concentration distribution of the given elements within the lower region 46 and the upper region 48 does not need to be uniform. The concentration of the given element within the lower region 46 and the upper region 48 can be the average value of the concentration of the given element within each region.

[0055] In this embodiment, the concentration (atomic %) of the additive element in the lower region 46 can be higher than the concentration (atomic %) of the additive element in the upper region 48. By increasing the concentration of the additive element in the lower region 46 compared to the upper region 48, even when hydrogen attempts to penetrate from the sidewall of the absorber pattern 4a, it is possible to suppress the penetration of hydrogen from the lower region 46 to the interface between the absorption layer 42 and the layer below it. Therefore, the peeling of the protective film 3 and the absorber pattern 4a can be more reliably suppressed. In addition, since the concentration of the additive element in the upper region 48 is relatively low, a decrease in the film density of the upper region 48 can be prevented. Therefore, the thickening of the absorber film 4 can be suppressed. The ratio of the film thickness of the lower region 46 to the film thickness of the absorption layer 42 (film thickness of the lower region 46 / film thickness of the absorption layer 42) is preferably 0.1 or higher, and more preferably 0.2 or higher.

[0056] In this embodiment, the concentration (atomic %) of the additive element in the upper region 48 can be higher than the concentration (atomic %) of the additive element in the lower region 46. By increasing the concentration of the additive element in the upper region 48 compared to the lower region 46, it is possible to suppress the intrusion of hydrogen from the surface of the absorber pattern 4a. Therefore, it is possible to more reliably suppress the peeling of the protective film 3 and the absorber pattern 4a. In addition, since the concentration of the additive element in the lower region 46 is relatively low, it is possible to prevent a decrease in the film density of the lower region 46. Therefore, it is possible to suppress the thickening of the absorber film 4. The ratio of the film thickness of the upper region 48 to the film thickness of the absorber layer 42 (film thickness of upper region 48 / film thickness of absorber layer 42) is preferably 0.1 or higher, and more preferably 0.2 or higher.

[0057] The content of the additive element (hydrogen (H) and / or deuterium (D)) in the lower region 46 can be uniform or substantially uniform throughout the entire lower region 46. Similarly, the content of the additive element (hydrogen (H) and / or deuterium (D)) in the upper region 48 can be uniform or substantially uniform throughout the entire upper region 48. Furthermore, the content of the additive element in the lower region 46 and / or upper region 48 can have a predetermined concentration distribution. Adding the additive element to the absorption layer 42 tends to decrease the membrane density of the absorber film 4. Therefore, it is preferable to add the additive element to the absorption layer 42 only in the necessary areas. To achieve this, as described above, it is necessary that the concentration of the additive element in one of the upper region 48 and the lower region 46 is higher than that of the other. The concentration in the upper region 48 and the lower region 46 can be determined by considering the concentration of hydrogen gas in the exposure atmosphere and examining which region is more likely to allow hydrogen to penetrate from, thereby deciding which region should have a higher concentration.

[0058] An intermediate region may be present between the lower region 46 and the upper region 48 of the absorption layer 42. The concentration distribution of the additive element in the intermediate region is arbitrary. The concentration distribution of the additive element in the absorption layer 42 (the lower region 46 and the upper region 48, and the intermediate region if one is included) can be monotonically decreasing or monotonically increasing in the depth direction. If the concentration of the additive element in the lower region 46 is lower than the concentration of the additive element in the upper region 48, the concentration of the additive element in the absorption layer 42 can monotonically decrease in the depth direction of the absorption layer 42 from the upper region 48 to the lower region 46. Also, if the concentration of the additive element in the lower region 46 is higher than the concentration of the additive element in the upper region 48, the concentration of the additive element in the absorption layer 42 can monotonically increase in the depth direction of the absorption layer 42 from the upper region 48 to the lower region 46. Within the upper region 48, the concentration of the additive element can also monotonically decrease or monotonically increase in the depth direction. Similarly, within the lower region 46, the concentration of the additive element can decrease or increase monotonically in the depth direction. The change in the concentration of the additive element in the depth direction can change uniformly in a gradient, or it can change (increase or decrease) in a stepwise manner. In this specification, a monotonically decreasing concentration of an element includes a stepwise decrease in the concentration of the element. In this specification, a monotonically increasing concentration of an element includes a stepwise increase in the concentration of the element.

[0059] The tantalum content in the absorption layer 42, including the lower region 46 and the upper region 48, is preferably 40 atomic percent or more, more preferably 50 atomic percent or more, and even more preferably 60 atomic percent or more. The tantalum content in the absorption layer 42 is preferably 95 atomic percent or less. The upper limit of the nitrogen content in the absorption layer 42 is preferably 50 atomic percent or less, and more preferably 30 atomic percent or less.

[0060] The content of the additive elements (hydrogen (H) and / or deuterium (D)) in the absorption layer 42, including the lower region 46 and the upper region 48 (the total content of both if both hydrogen (H) and deuterium (D) are included) is 0.1 atomic% or more and 30 atomic% or less, preferably 5 atomic% or more, more preferably 10 atomic% or more, and even more preferably more than 15 atomic%. By including hydrogen (H) and / or deuterium (D) as additive elements in the absorption layer 42, it is possible to eliminate the possibility of new atomic hydrogen (H) entering the absorber film 4 during EUV exposure in an exposure atmosphere containing hydrogen gas. Therefore, by using the reflective mask blank 100 of this embodiment, it is possible to more reliably suppress the peeling of the absorber pattern 4a of the reflective mask 200. Furthermore, if the content of the additive elements exceeds 30 atomic%, the film density of the absorption layer 42 decreases, the extinction coefficient k becomes smaller, and it becomes difficult to have the function of absorbing EUV light.

[0061] In EUV exposure in an exposure atmosphere containing hydrogen gas, the same effect can be obtained in reducing the penetration of atomic hydrogen (H) into the absorption layer 42, regardless of whether hydrogen (H) or deuterium (D) is used as the additive element. However, compared to hydrogen (H), deuterium (D) has stronger bonds with other elements in the absorption layer 42 and can therefore exist stably in the absorption layer 42. For this reason, it is preferable to use deuterium (D) as the additive element for the absorption layer 42.

[0062] The absorption layer 42 may contain boron (B). The boron (B) content of the absorption layer 42 is more than 5 atomic percent, preferably 10 atomic percent to 30 atomic percent. By containing boron (B) in the absorber membrane 4, it becomes easier to amorphousize the crystalline structure, resulting in an absorber membrane 4 with excellent smoothness. In addition, in this embodiment, the absorber membrane 4 contains hydrogen to suppress peeling of the absorber pattern 4a. When the absorber membrane 4 contains hydrogen, the membrane density of the absorber membrane 4 tends to decrease. By containing boron in the absorber membrane 4 of this embodiment, an amorphous absorber membrane 4 with suppressed membrane density reduction can be obtained.

[0063] Furthermore, if the absorption layer 42 contains boron (B), it is preferable that the nitrogen content be less than the boron content. This is because a lower nitrogen content results in a faster etching rate with chlorine gas, making it easier to remove the absorption layer 42.

[0064] Furthermore, if the absorption layer 42 contains boron (B), only one of the lower region 46 (lower layer) and the upper region 48 (upper layer) may contain boron (B). Alternatively, both the lower region 46 (lower layer) and the upper region 48 (upper layer) may contain boron (B).

[0065] Of the absorber membrane 4, the lower layer material including the lower surface region 46 is preferably a TaNH film or a TaBNH film if it contains additive elements, and preferably a TaN film or a TaBN film if it does not contain additive elements. Similarly to the lower layer, the upper layer material including the upper surface region 48 of the absorber membrane 4 is preferably a TaNH film or a TaBNH film if it contains additive elements, and preferably a TaN film or a TaBN film if it does not contain additive elements. To obtain an absorber membrane 4 with excellent smoothness, it is more preferable that the materials of the lower surface region 46 (lower layer) and the upper surface region 48 (upper layer) of the absorber membrane 4 contain boron (B). Note that in the above materials, hydrogen (H) can be substituted with deuterium (D).

[0066] The absorption layer 42 made of the above-mentioned materials can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, the absorption layer 42 can be deposited using a target made of tantalum by a reactive sputtering method using nitrogen gas and a rare gas such as argon (Ar) gas, krypton (Kr) gas, and / or xenon (Xe) gas, which are doped with an additive element gas (hydrogen (H) gas and / or deuterium (D) gas). If one of the lower region 46 and the upper region 48 does not contain an additive element, the film can be deposited by a reactive sputtering method using a rare gas doped with nitrogen gas, but without the additive element gas. Furthermore, if the absorption layer 42 contains boron (B), it can be deposited using a target containing tantalum and boron.

[0067] Furthermore, in order to include hydrogen in the absorption layer 42, it is preferable to reduce the power used when depositing the film by magnetron sputtering. On the other hand, reducing the power during film deposition can lead to another problem: an increase in tensile stress in the deposited thin film, resulting in a larger deformation of the substrate 1. The inventors have found that by specifying the composition ratio of hydrogen to nitrogen in the absorption layer 42, it is possible to reduce the film stress of the absorber film 4 while preventing delamination of the absorber pattern 4a. Specifically, in the composition of the absorption layer 42, if the nitrogen (N) content is 0.1 atomic% to 40 atomic%, the additive element content is 0.1 atomic% to 30 atomic%, and the composition ratio of the additive element to nitrogen (N) (additive element:nitrogen) is 5:95 to 50:50, preferably 15:85 to 40:60, it is possible to suppress another problem: an increase in tensile stress in the deposited thin film of the absorption layer 42, resulting in a larger deformation of the substrate 1.

[0068] The thickness of the absorption layer 42 is preferably 30 nm or more, and more preferably 40 nm or more. Furthermore, the thickness of the absorption layer 42 is preferably 80 nm or less, and more preferably 70 nm or less.

[0069] As shown in Figures 1 and 2, the absorber film 4 of this embodiment has a reflectance adjustment layer 44 on top of the absorption layer 42 (on the opposite side from the substrate 1).

[0070] The absorber film 4 is a laminated film having a reflectance adjustment layer 44 on top of an absorption layer 42, and by setting the thickness of the reflectance adjustment layer 44 to a predetermined thickness, the reflectance adjustment layer 44 becomes a film that adjusts reflectance when performing mask pattern defect inspection using inspection light such as DUV light. Therefore, the inspection sensitivity during mask pattern defect inspection can be increased. For example, if the material of the reflectance adjustment layer 44 is TaBO, setting the thickness to approximately 14 nm allows it to function effectively as a film that adjusts reflectance during mask pattern defect inspection.

[0071] The reflectance adjustment layer 44 preferably contains tantalum (Ta) and oxygen (O), and at least one additive element selected from hydrogen (H) and deuterium (D). Similar to the absorption layer 42, by including a predetermined additive element in the reflectance adjustment layer 44, the intrusion of atomic hydrogen (H) from the reflectance adjustment layer 44 can be suppressed when EUV exposure is performed in an atmosphere containing hydrogen gas. As a result, a reflective mask 200 can be obtained that can suppress the peeling of the absorber pattern 4a.

[0072] When the reflectance adjustment layer 44 contains a predetermined additive element, the content of the additive element in the reflectance adjustment layer 44 is preferably 0.1 atomic% or more and 30 atomic% or less, and more preferably more than 15 atomic% and 30 atomic% or less. Furthermore, the content of the additive element in the reflectance adjustment layer 44 is preferably 10 atomic% or more higher than the content of the additive element in the absorption layer 42. By having the content of the additive element in the reflectance adjustment layer 44 within the predetermined range, it becomes more reliable to obtain a reflective mask 200 that can suppress the peeling of the absorber pattern 4a.

[0073] The reflectance adjustment layer 44 preferably further contains boron(B). The inclusion of boron(B) in the reflectance adjustment layer 44 facilitates amorphous formation of the crystalline structure, resulting in an absorber film 4 with excellent smoothness. To ensure amorphous formation, the boron(B) content in the reflectance adjustment layer 44 is preferably more than 5 atomic percent, and more preferably 10 atomic percent to 30 atomic percent.

[0074] As described above, the material of the reflectance adjustment layer 44 includes tantalum (Ta) and oxygen (O), and optionally, predetermined additive elements (hydrogen (H) and / or deuterium (D)) and / or boron (B). The reflectance adjustment layer 44 is preferably a TaO film or a TaBO film. If the reflectance adjustment layer 44 contains additive elements, it is preferable to use a TaOH film (or TaOD film) or a TaBOH film (or TaBOD film).

[0075] The reflectance adjustment layer 44 made of the above-mentioned materials can be formed by magnetron sputtering methods such as DC sputtering and RF sputtering. For example, a reflectance adjustment layer 44 containing a predetermined additive element and boron (B) can be deposited by a reactive sputtering method using a target containing tantalum and boron, and using a rare gas such as argon (Ar) gas, krypton (Kr) gas, and / or xenon (Xe) gas with added oxygen gas and an additive element gas (hydrogen (H) gas and / or deuterium (D) gas). Also, for example, if the reflectance adjustment layer 44 does not contain the predetermined additive element, the reflectance adjustment layer 44 can be deposited by a reactive sputtering method using a target containing tantalum and boron, and using a rare gas with added oxygen gas. If the reflectance adjustment layer 44 does not contain boron (B), the reflectance adjustment layer 44 can be deposited using a target made of tantalum.

[0076] The thickness of the reflectance adjustment layer 44 is preferably 15 nm or less, and more preferably 8 nm or less. The thickness of the absorber film 4 is preferably 90 nm or less, and more preferably 80 nm or less. The surface roughness (RMS) of the surface of the absorber film 4 is preferably 0.5 nm or less.

[0077] The material Ta used for the absorber film 4 in this embodiment has a large absorption coefficient (extinction coefficient) for EUV light and can be easily dry-etched with chlorine-based gas and / or fluorine-based gas. Therefore, Ta is considered a material for the absorber film 4 with excellent processability. Furthermore, by adding B (and further Si and / or Ge, etc.) to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 4 can be improved. In addition, by adding N and / or O to Ta, the resistance of the absorber film 4 to oxidation is improved, thus improving its stability over time.

[0078] For etching the absorber film 4 in this embodiment, fluorine-based gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2 can be used. Chlorine-based gases such as Cl2, SiCl4, CHCl3, CCl4, and BCl3 can be used. These etching gases may also contain inert gases such as He and / or Ar as needed.

[0079] In the reflective mask blank 100 of this embodiment, by using the absorber film 4 described above, a reflective mask 200 can be obtained that suppresses the thickening of the absorber film 4 while suppressing the peeling of the absorber pattern 4a when EUV exposure is performed in an atmosphere containing hydrogen gas.

[0080] The absorber film 4 in this embodiment can be an absorber film 4 having a phase shift function that also takes into account the phase difference of EUV light. An absorber film 4 having a phase shift function absorbs EUV light and reflects a portion of it to shift its phase. That is, in a reflective mask 200 patterned with an absorber film 4 having a phase shift function, in the area where the absorber film 4 is formed, it absorbs EUV light to attenuate it while reflecting a portion of the light at a level that does not adversely affect pattern transfer. In the area where the absorber film 4 is not formed (field area), EUV light is reflected from the multilayer reflective film 2 via the protective film 3. Therefore, there is a desired phase difference between the light reflected from the absorber film 4 having a phase shift function and the light reflected from the field area. The absorber film 4 having a phase shift function is formed such that the phase difference between the light reflected from the absorber film 4 and the light reflected from the multilayer reflective film 2 is between 170 and 190 degrees. The light with inverted phase differences near 180 degrees interferes with each other at the pattern edge, improving the image contrast of the projected optical image. As image contrast improves, resolution increases, and various exposure-related margins, such as exposure margin and focus margin, can be increased.

[0081] <<Etching mask film 6>> The reflective mask blank 100 of this embodiment may have an etching mask film 6 on top of the absorber film 4.

[0082] Materials for the etching mask film 6 that have a high etching selectivity ratio of the absorber film 4 (especially the reflectivity adjustment layer 44) to the etching mask film 6 include chromium and chromium compounds. In this case, the absorber film 4 can be etched with a fluorine-based gas or a chlorine-based gas. Examples of chromium compounds include materials containing chromium (Cr) and at least one element selected from nitrogen (N), oxygen (O), carbon (C), and boron (B). Examples of chromium compounds include CrN, CrC, CrO, CrON, CrOC, CrCN, CrCON, CrBN, CrBC, CrBO, CrBON, CrBCN, and CrBOCN. Materials to which hydrogen (H) and / or deuterium (D) are added to these chromium compounds are also included. In order to increase the etching selectivity ratio with chlorine-based gas, it is preferable that the etching mask film 6 be made of a material that is substantially free of oxygen. Examples of substantially oxygen-free chromium compounds include CrN, CrC, CrCN, CrBN, CrBC, and CrBCN, and materials to which H and / or D are added to these chromium compounds. The Cr content of the chromium compound in the etching mask film 6 is preferably 50 atomic% or more and less than 100 atomic%, and more preferably 80 atomic% or more and less than 100 atomic%. Furthermore, "substantially oxygen-free" refers to a chromium compound in which the oxygen content is 10 atomic% or less, preferably 5 atomic% or less. The material may contain metals other than chromium to the extent that the effects of the embodiments of the present invention are obtained.

[0083] When an etching mask film 6 is formed, the thickness of the resist film 11 can be reduced, which is advantageous for miniaturizing the pattern. From the viewpoint of obtaining the function of an etching mask that accurately forms the transfer pattern on the absorber film 4, the thickness of the etching mask film 6 is preferably 3 nm or more. Furthermore, from the viewpoint of reducing the thickness of the resist film 11, the thickness of the etching mask film 6 is preferably 15 nm or less, and more preferably 10 nm or less.

[0084] <<Resist film 11>> The reflective mask blank 100 of this embodiment can have a resist film 11 on top of the absorber film 4 (or on top of the etching mask film 6 if an etching mask film 6 is formed). The reflective mask blank 100 of this embodiment also includes a form having a resist film 11. In the reflective mask blank 100 of this embodiment, the resist film 11 can also be made thinner by selecting an absorber film 4 (absorption layer 42 and reflectance adjustment layer 44) and etching gas of an appropriate material and / or appropriate film thickness.

[0085] For example, a chemically-amplified resist (CAR) can be used as the material for the resist film 11. By patterning the resist film 11 and etching the absorber film 4 (absorption layer 42 and reflectance adjustment layer 44), a reflective mask 200 having a predetermined transfer pattern can be manufactured.

[0086] <<Back surface conductive film 5>> Generally, a back-side conductive film 5 for electrostatic chucks is formed on the second main surface (back side) of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The required electrical properties (sheet resistance) of the back-side conductive film 5 for electrostatic chucks are usually 100 Ω / □ (Ω / Square) or less. The back-side conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering, using a target of a metal or alloy such as chromium or tantalum.

[0087] The chromium (Cr)-containing material of the back surface conductive film 5 is preferably a Cr compound containing at least one selected from boron, nitrogen, oxygen, and carbon. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.

[0088] As the tantalum (Ta)-containing material for the back surface conductive film 5, it is preferable to use Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of boron, nitrogen, oxygen, and carbon in any of these. Examples of Ta compounds include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON.

[0089] For materials containing tantalum (Ta) or chromium (Cr), it is preferable that the nitrogen (N) present on the surface layer is low. Specifically, the nitrogen content on the surface layer of the back conductive film 5 of a material containing tantalum (Ta) or chromium (Cr) is preferably less than 5 atomic percent, and it is more preferable that the surface layer is substantially nitrogen-free. This is because a lower nitrogen content on the surface layer of the back conductive film 5 of a material containing tantalum (Ta) or chromium (Cr) results in higher wear resistance.

[0090] The back surface conductive film 5 is preferably made of a material containing tantalum and boron. By making the back surface conductive film 5 of a material containing tantalum and boron, a back surface conductive film 5 with abrasion resistance and chemical resistance can be obtained. When the back surface conductive film 5 contains tantalum (Ta) and boron (B), the B content is preferably 5 to 30 atomic percent. The ratio of Ta to B (Ta:B) in the sputtering target used to deposit the back surface conductive film 5 is preferably 95:5 to 70:30.

[0091] The thickness of the back conductive film 5 is not particularly limited as long as it satisfies its function as an electrostatic chuck. The thickness of the back conductive film 5 is usually between 10 nm and 200 nm. In addition, this back conductive film 5 also serves to adjust the stress on the second main surface side of the mask blank 100. The back conductive film 5 is adjusted to balance the stress from the various films formed on the first main surface side so that a flat reflective mask blank 100 can be obtained.

[0092] <Reflective mask 200 and method for manufacturing the same> The reflective mask 200 of this embodiment has an absorbent pattern 4a in which the absorbent film 4 of the reflective mask blank 100 described above is patterned.

[0093] Since the absorber pattern 4a of the reflective mask 200 absorbs EUV light and the aperture of the absorber pattern 4a reflects EUV light, a predetermined fine transfer pattern can be transferred to the object to be transferred by irradiating the reflective mask 200 with EUV light using a predetermined optical system.

[0094] A reflective mask 200 is manufactured using the reflective mask blank 100 of this embodiment. Only an overview is given here, and a detailed explanation will be provided later in the examples. Furthermore, here we will describe the case in which the reflective mask blank 100 includes an etching mask film 6, as shown in Figures 3A to 3E.

[0095] A reflective mask blank 100 is prepared, and a resist film 11 is formed on the etching mask film 6 formed on the absorber film 4 on its first main surface (see Figure 3A; this step is unnecessary if the reflective mask blank 100 already includes a resist film 11). A desired pattern is drawn (exposed) onto this resist film 11, and then developed and rinsed to form a predetermined resist pattern 11a (see Figure 3B).

[0096] In the case of a reflective mask blank 100, the etching mask film 6 is etched using the resist pattern 11a as a mask to form an etching mask pattern 6a (see Figure 3C). The resist pattern 11a is removed by a wet treatment such as oxygen ashing or hot sulfuric acid. Next, the absorber film 4 (reflectance adjustment layer 44 and absorption layer 42) is etched using the etching mask pattern 6a as a mask to form an absorber pattern 4a (reflectance adjustment layer pattern 44a and absorption layer pattern 42a) (see Figure 3D). The etching mask pattern 6a is removed to form the absorber pattern 4a (reflectance adjustment layer pattern 44a and absorption layer pattern 42a) (see Figure 3E). Finally, the reflective mask 200 can be manufactured by wet cleaning with an acidic or alkaline aqueous solution.

[0097] Furthermore, the etching mask pattern 6a can also be removed by etching it simultaneously with the absorption layer 42 during the patterning of the absorption layer 42.

[0098] In the reflective mask 200 of this embodiment, the etching mask pattern 6a can be left on top of the absorber pattern 4a without being removed. However, in that case, it is necessary to leave the etching mask pattern 6a as a uniform thin film. To avoid non-uniformity as a thin film of the etching mask pattern 6a, it is preferable to remove the etching mask pattern 6a in the reflective mask 200 of this embodiment rather than placing it.

[0099] In the manufacturing method of the reflective mask 200 of this embodiment, it is preferable to pattern the etching mask film 6 of the reflective mask blank 100 of this embodiment described above with a dry etching gas containing a chlorine-based gas and an oxygen gas. In the case of an etching mask film 6 containing chromium (Cr), dry etching can be suitably performed using a chlorine-based gas and an oxygen gas. Furthermore, it is preferable to pattern the reflectance adjustment layer 44 with a dry etching gas containing a fluorine-based gas. In the case of a reflectance adjustment layer 44 made of a material containing tantalum (Ta) and oxygen (O), dry etching can be suitably performed using a fluorine-based gas. It is preferable to pattern the absorption layer 42 with a dry etching gas containing a fluorine-based gas or a chlorine-based gas that does not contain oxygen. In the case of an absorption layer 42 made of a material containing tantalum (Ta) and nitrogen (N), dry etching can be suitably performed using a fluorine-based gas or a chlorine-based gas that does not contain oxygen. In this way, the absorber pattern 4a of the reflective mask 200 can be formed.

[0100] Through the above process, a reflective mask 200 can be obtained that can suppress the peeling of the absorber pattern 4a when EUV exposure is performed in an atmosphere containing hydrogen gas.

[0101] <Manufacturing method for semiconductor devices> The semiconductor device manufacturing method of this embodiment includes the step of setting the reflective mask 200 of this embodiment in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a substrate to be transferred.

[0102] In the semiconductor device manufacturing method of this embodiment, since the above-described reflective mask blank 100 is used, when EUV exposure is performed in an atmosphere containing hydrogen gas using the reflective mask 200 of this embodiment, peeling of the absorber pattern 4a can be suppressed. Therefore, when manufacturing semiconductor devices, it is possible to manufacture semiconductor devices with fine and high-precision transfer patterns with a high yield.

[0103] By performing EUV exposure using the reflective mask 200 of this embodiment described above, a desired transfer pattern based on the absorber pattern 4a on the reflective mask 200 can be formed on a semiconductor substrate. In addition to this lithography process, a semiconductor device with a desired electronic circuit can be manufactured by going through various processes such as etching the workpiece, forming insulating films and conductive films, introducing dopants, and annealing.

[0104] More specifically, an EUV exposure system consists of a laser plasma light source that generates EUV light, an illumination optical system, a mask stage system, a reduction projection optical system, a wafer stage system, and vacuum equipment. The light source is equipped with a debris trap function, a cut filter to cut out long-wavelength light other than the exposure light, and equipment for differential vacuum pumping. The illumination optical system and the reduction projection optical system are composed of reflective mirrors. The EUV exposure reflective mask 200 is electrostatically attracted to the mask stage by a conductive film formed on its second main surface and placed on the mask stage.

[0105] Light from an EUV light source is irradiated onto the reflective mask 200 via an illumination optical system at an angle of 6° to 8° relative to the vertical plane of the reflective mask 200. The reflected light from the reflective mask 200 in response to this incident light is reflected in the opposite direction to the incident light and at the same angle as the incident light (specular reflection), and is guided to a reflective projection optical system, which usually has a reduction ratio of 1 / 4, to expose the resist on the wafer (semiconductor substrate) placed on the wafer stage. During this time, at least the area through which the EUV light passes is evacuated. In addition, hydrogen gas is introduced into the atmosphere during exposure to prevent exposure contamination. Furthermore, in this exposure, scan exposure is the mainstream method, in which the mask stage and wafer stage are scanned in synchronization at a speed corresponding to the reduction ratio of the reduction projection optical system, and exposure is performed through a slit. Then, by developing this exposed resist film, a resist pattern can be formed on the semiconductor substrate. In this embodiment, a reflective mask 200 is used that can suppress the peeling of the absorber pattern 4a when EUV exposure is performed in an atmosphere containing hydrogen gas. Therefore, even if the reflective mask 200 of this embodiment is repeatedly used in EUV exposure, the resist pattern formed on the semiconductor substrate will be a desired one with high dimensional accuracy. Then, by using this resist pattern as a mask to perform etching or the like, a predetermined wiring pattern can be formed on the semiconductor substrate, for example. A semiconductor device is manufactured by going through such exposure processes, workpiece processing processes, insulating film and conductive film formation processes, dopant introduction processes, annealing processes, and other necessary processes. [Examples]

[0106] The following describes the embodiments with reference to the drawings. In the embodiments, the same reference numerals are used for similar components, and their descriptions are simplified or omitted.

[0107] In the following description, the elemental composition of Ta, B, N, and O in the deposited thin film was measured by X-ray photoelectron spectroscopy (XPS), and the elemental composition of H was measured by elastic recoil detection analysis (ERDA).

[0108] [Example 1] The reflective mask blank 100 of Example 1 will now be described. As shown in Figure 2, the reflective mask blank 100 of Example 1 has a back surface conductive film 5, a substrate 1, a multilayer reflective film 2, a protective film 3, and an absorber film 4. The absorber film 4 consists of an absorption layer 42 and a reflectance adjustment layer 44. The absorption layer 42 consists of a lower layer, which is a lower surface region 46, and an upper layer, which is an upper surface region 48. Then, as shown in Figure 4A, a resist film 11 is formed on the absorber film 4. Figures 4A to 4E are schematic cross-sectional views of the main parts showing the process of manufacturing a reflective mask 200 from the reflective mask blank 100.

[0109] The substrate 1 used in Example 1 was prepared as follows. Specifically, a SiO2-TiO2 glass substrate, which is a 6025 size (approximately 152 mm × 152 mm × 6.35 mm) low thermal expansion glass substrate with both the first and second main surfaces polished, was prepared as substrate 1. Polishing consisting of a rough polishing process, a precision polishing process, a local polishing process, and a touch polishing process was performed to obtain a flat and smooth main surface.

[0110] A back surface conductive film 5 made of a CrN film was formed on the second main surface (back surface) of the SiO2-TiO2 glass substrate 1 by magnetron sputtering (reactive sputtering) under the following conditions. Formation conditions for the conductive film 5 on the back surface: Cr target, mixed gas atmosphere of Ar and N2 (Ar: 90%, N: 10%), film thickness 20 nm.

[0111] Next, a multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 opposite to the side where the back surface conductive film 5 was formed. To make the multilayer reflective film 2 formed on the substrate 1 suitable for EUV light with a wavelength of 13.5 nm, a periodic multilayer reflective film 2 made of Mo and Si was formed. The multilayer reflective film 2 was formed by alternately stacking Mo layers and Si layers on the substrate 1 using an ion beam sputtering method in an Ar gas atmosphere with a Mo target and a Si target. First, a Si film was deposited to a thickness of 4.2 nm, followed by a Mo film to a thickness of 2.8 nm. This constituted one period, and 40 periods were stacked in the same manner, and finally a Si film to a thickness of 4.0 nm was deposited to form the multilayer reflective film 2. Although 40 periods were used here, it is not limited to this, and for example, 60 periods could also be used. If 60 periods are used, the number of processes will increase compared to 40 periods, but the reflectivity for EUV light can be increased.

[0112] Subsequently, in an Ar gas atmosphere, a protective film 3 made of RuNb was deposited to a thickness of 2.5 nm using ion beam sputtering with a RuNb target.

[0113] Next, an absorber film 4 consisting of an absorption layer 42 (a lower layer with a lower surface region 46 and an upper layer with a upper surface region 48) and a reflectance adjustment layer 44 was formed on the protective film 3. Table 1 shows the materials, film thickness, type of target and deposition gas used during film formation (sputtering), hydrogen (H) content, boron (B) content, and material composition ratio of the protective film 3, absorption layer 42 (lower and upper layers), and reflectance adjustment layer 44 of Example 1. In Table 1, "at%" for material content and composition ratio means atomic percent. In Table 1, "RMS (nm)" indicates the root mean square roughness (RMS) of the mask blank after the formation of the absorber film 4.

[0114] Specifically, first, the lower layer (bottom region 46) of the absorption layer 42, which consists of a TaBNH film, was formed by DC magnetron sputtering. The TaBNH film was deposited using a TaB mixed sintering target by reactive sputtering in a mixed gas atmosphere of Xe gas, N2 gas, and H2 gas, with the film thickness shown in Table 1.

[0115] Next, the upper layer (upper surface region 48) of the absorption layer 42, which is made of a TaBN film, was formed by DC magnetron sputtering. The TaBN film was deposited using a TaB mixed sintering target by reactive sputtering in a mixed gas atmosphere of Xe gas and N2 gas, with the film thickness shown in Table 1.

[0116] Table 1 shows the elemental ratios of the TaBNH film (lower layer, bottom surface region 46) and the TaBN film (upper layer, top surface region 48) of Example 1.

[0117] Next, a reflectivity adjustment layer 44 made of a TaBO film was formed by magnetron sputtering. The TaBO film was deposited using a TaB mixed sintering target in a mixed gas atmosphere of Ar gas and O2 gas by reactive sputtering to the thickness shown in Table 1.

[0118] Table 1 shows the elemental ratios of the TaBO film (reflectance adjustment layer 44) in Example 1. Table 1 also shows the root mean square roughness (RMS) of the TaBO film (reflectance adjustment layer 44) after formation.

[0119] As described above, the reflective mask blank 100 of Example 1 was manufactured.

[0120] Next, the reflective mask 200 of Example 1 was manufactured using the reflective mask blank 100 of Example 1 described above.

[0121] A resist film 11 was formed to a thickness of 150 nm on the absorber film 4 of the reflective mask blank 100 (Figure 4A). Chemically amplified resist (CAR) was used to form the resist film 11. A desired pattern was drawn (exposed) on this resist film 11, and then developed and rinsed to form a predetermined resist pattern 11a (Figure 4B). Next, using the resist pattern 11a as a mask, a reflectivity adjustment layer pattern 44a was formed by dry etching of the TaBO film (reflectivity adjustment layer 44) using CF4 gas (Figure 4C). Subsequently, the TaBN film (upper layer, upper surface region 48) and the TaBNH film (lower layer, lower surface region 46) were patterned by dry etching using Cl2 gas to form an absorption layer pattern 42a (Figure 4D).

[0122] Subsequently, the resist pattern 11a was removed by oxygen ashing (Figure 4E). Finally, wet washing with pure water (DIW) was performed to produce the reflective mask 200 of Example 1.

[0123] Furthermore, if necessary, a mask defect inspection can be performed after wet cleaning, and mask defects can be corrected as appropriate.

[0124] The reflective mask 200 prepared in Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which the film to be processed and the resist film had been formed on the semiconductor substrate. To prevent exposure contamination, hydrogen gas was introduced into the atmosphere during EUV exposure. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate on which the film to be processed had been formed.

[0125] By transferring this resist pattern to the workpiece through etching, and then going through various processes such as forming insulating films and conductive films, introducing dopants, and annealing, we were able to manufacture a semiconductor device with the desired properties.

[0126] Using the reflective mask 200 of Example 1, EUV exposure was performed 1000 times, with hydrogen gas introduced into the exposure atmosphere. After 1000 exposures, the delamination of the absorber pattern 4a of the reflective mask 200 of Example 1 was evaluated, and it was confirmed that no delamination had occurred.

[0127] [Example 2] The reflective mask blank 100 of Example 2 will now be described. The reflective mask blank 100 of Example 2 is the same as the reflective mask blank 100 of Example 1, except that the hydrogen content and film thickness of the lower layer (bottom surface region 46) of the absorption layer 42 are different from those of Example 1. Table 1 shows the composition of the absorption layer 42 (lower and upper layers) of Example 2. In other words, in the reflective mask blank 100 of Example 2, the flow rate of H2 gas and the film deposition time in the mixed gas during reactive sputtering were changed so that the composition of the lower surface region 46, which is the lower layer, as shown in Table 1 was obtained.

[0128] Table 1 shows the elemental ratios of the TaBNH film (lower layer, bottom surface region 46) in Example 2. The elemental ratios of the TaBO film (reflectance adjustment layer 44) and the TaBN film (upper layer, top surface region 48) in Example 2 were the same as in Example 1.

[0129] As described above, the reflective mask blank 100 of Example 2 was manufactured.

[0130] Next, using the reflective mask blank 100 of Example 2 described above, a reflective mask 200 of Example 2 was manufactured in the same manner as in Example 1. Similar to Example 1, the delamination of the absorber pattern 4a of the reflective mask 200 of Example 2 was evaluated, and it was confirmed that no delamination occurred.

[0131] [Example 3] The reflective mask blank 100 of Example 3 will now be described. The reflective mask blank 100 of Example 3 is the same as the reflective mask blank 100 of Example 1, except that the absorption layer 42 (lower and upper layers) and the reflectance adjustment layer 44 do not contain boron (B). Table 1 shows the composition of the absorption layer 42 (lower and upper layers) and the reflectance adjustment layer 44 of Example 3. In other words, when forming the absorption layer 42 (lower and upper layers) and the reflectance adjustment layer 44 of the reflective mask blank 100 of Example 3, a Ta target that does not contain boron (B) was used as the target during reactive sputtering so that the composition of the reflectance adjustment layer 44 shown in Table 1 would be achieved. The mixed gas used during reactive sputtering is the same as in Example 1.

[0132] Table 1 shows the elemental ratios of the TaNH film (lower layer, bottom surface region 46), the TaN film (upper layer, top surface region 48), and the TaO film (reflectance adjustment layer 44) of Example 3.

[0133] As described above, the reflective mask blank 100 of Example 3 was manufactured.

[0134] Next, using the reflective mask blank 100 of Example 3, a reflective mask 200 of Example 3 was manufactured in the same manner as in Example 1. Similar to Example 1, the delamination of the absorber pattern 4a of the reflective mask 200 of Example 3 was evaluated, and it was confirmed that no delamination occurred.

[0135] [Example 4] The reflective mask blank 100 of Example 4 will now be described. The reflective mask blank 100 of Example 4 is the same as the reflective mask blank 100 of Example 1, except that the lower layer, which is the lower surface region 46 of the absorption layer 42, does not contain hydrogen (H), while the upper layer, which is the upper surface region 48, contains hydrogen (H). Table 1 shows the composition of the absorption layer 42 (lower surface region 46 and upper surface region 48) of Example 4. Specifically, in the reflective mask blank 100 of Example 4, when forming the lower layer, which is the lower surface region 46, a mixed gas of Xe gas and N2 gas was used as the mixed gas during reactive sputtering, instead of H2 gas, to achieve the composition of the lower layer TaBN film shown in Table 1. Similarly, when forming the upper layer, which is the upper surface region 48, a mixed gas of Xe gas, N2 gas, and H2 gas was used as the mixed gas during reactive sputtering to achieve the composition of the upper layer TaBNH film shown in Table 1.

[0136] Table 1 shows the elemental ratios of the TaBN film (lower layer, bottom surface region 46) and the TaBNH film (upper layer, top surface region 48) in Example 4. The elemental ratio of the TaBO film (reflectance adjustment layer 44) in Example 4 was the same as in Example 1.

[0137] As described above, the reflective mask blank 100 of Example 4 was manufactured.

[0138] Next, using the reflective mask blank 100 of Example 4, a reflective mask 200 of Example 4 was manufactured in the same manner as in Example 1. At this time, the absorber pattern 4a was formed such that regions with sparse patterns and regions with dense patterns were formed. Similar to Example 1, when the delamination of the absorber pattern 4a of the reflective mask 200 of Example 4 was evaluated, it was confirmed that delamination occurred in the regions with sparse patterns, but not in the regions with dense patterns.

[0139] [Example 5] The reflective mask blank 100 of Example 5 will now be described. The reflective mask blank 100 of Example 5 is the same as the reflective mask blank 100 of Example 1, except that the lower layer (lower surface region 46 of the absorption layer 42), the upper layer (upper surface region 48 of the absorption layer 42), and the reflectance adjustment layer 44 contain hydrogen (H). Table 1 shows the composition of the absorption layer 42 (lower surface region 46, which is the lower layer) and the reflectance adjustment layer 44 of Example 5. Specifically, for the reflective mask blank 100 of Example 5, a mixed gas of Xe gas, N2 gas, and H2 gas was used as the mixed gas during reactive sputtering to achieve the composition of the lower and upper TaNH films shown in Table 1. Furthermore, when forming the reflectance adjustment layer 44, a mixed gas of Ar gas, O2 gas, and H2 gas was used as the mixed gas during reactive sputtering to achieve the composition of the TaOH film shown in Table 1.

[0140] Table 1 shows the elemental ratios of the TaNH film (lower layer, bottom surface region 46), the TaNH film (upper layer, top surface region 48), and the TaOH film (reflectance adjustment layer 44) of Example 5.

[0141] As described above, the reflective mask blank 100 of Example 5 was manufactured.

[0142] Next, using the reflective mask blank 100 of Example 5 described above, a reflective mask 200 of Example 5 was manufactured in the same manner as in Example 1. At this time, the absorber pattern 4a was made such that regions with sparse patterns and regions with dense patterns were formed. Similar to Example 1, when the film peeling of the absorber pattern 4a of the reflective mask 200 of Example 5 was evaluated, it was confirmed that no film peeling occurred in either the regions with sparse patterns or the regions with dense patterns.

[0143] [Example 6] The reflective mask blank 100 of Example 6 will now be described. The reflective mask blank 100 of Example 6 is the same as the reflective mask blank 100 of Example 1, except that the absorption layer 42 contains deuterium (D) (instead of hydrogen (H)). Table 1 shows the composition of the TaBND film (lower layer, bottom surface region 46) and the TaBN film (upper layer, top surface region 48) of Example 6. That is, in the reflective mask blank 100 of Example 6, when the absorption layer 42 was formed, the TaBND film was formed using D2 gas instead of H2 gas in the mixed gas during reactive sputtering so that the composition of the TaBND film (lower layer, bottom surface region 46) shown in Table 1 was achieved.

[0144] Table 1 shows the elemental ratios of the TaBND film (lower layer, bottom surface region 46) and the TaBN film (upper layer, top surface region 48) in Example 6. The elemental ratio of the TaBO film (reflectance adjustment layer 44) in Example 6 was the same as in Example 1.

[0145] As described above, the reflective mask blank 100 of Example 6 was manufactured.

[0146] Next, using the reflective mask blank 100 of Example 6, a reflective mask 200 of Example 6 was manufactured in the same manner as in Example 1. Similar to Example 1, the delamination of the absorber pattern 4a of the reflective mask 200 of Example 5 was evaluated, and it was confirmed that no delamination occurred.

[0147] [Comparative Example 1] As Comparative Example 1, a mask blank was manufactured using a TaBN film as the absorption layer 42. Comparative Example 1 is basically the same as Example 1, except that the absorption layer 42 is a TaBN film (single layer film). The TaBN film of the absorption layer 42 was deposited in the same manner as the TaBN film on top of the absorption layer 42 in Example 1.

[0148] Next, using the reflective mask blank 100 of Comparative Example 1, a reflective mask 200 of Comparative Example 1 was manufactured in the same manner as in Example 1.

[0149] The reflective mask 200 prepared in Comparative Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which the workpiece film and resist film had been formed on the semiconductor substrate. To prevent exposure contamination, hydrogen gas was introduced into the exposure atmosphere during EUV exposure. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate on which the workpiece film had been formed.

[0150] Using the reflective mask 200 of Comparative Example 1, EUV exposure was performed 1000 times with hydrogen gas introduced into the exposure atmosphere. After 1000 exposures, the delamination of the absorber pattern 4a of the reflective mask 200 of Comparative Example 1 was evaluated, and it was confirmed that delamination had occurred.

[0151] [Table 1] [Explanation of Symbols]

[0152] 1 circuit board 2 Multilayer reflective film 3 Protective film 4 Absorbent membrane 4a Absorber pattern 5. Conductive film on the back surface 6 Etching mask film 6a Etching mask pattern 11. Resist film 11a Resist Pattern 42 Absorption layer 42a Absorption layer pattern 44 Reflectance adjustment layer 44a Reflectance adjustment layer pattern 46 Bottom area 48 Top area 100 Reflective Mask Blanks 200 Reflective Masks

Claims

1. A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, a protective film on the multilayer reflective film, and an absorbent film on the protective film, The protective film comprises ruthenium (Ru) and at least one additive element selected from hydrogen (H) and deuterium (D). The absorbent membrane includes an absorbent layer in contact with the protective membrane. The absorption layer comprises tantalum (Ta) and nitrogen (N), and at least one additive element selected from hydrogen (H) and deuterium (D). A reflective mask blank characterized in that the concentration (atomic %) of the additive element in the protective film is greater than the concentration (atomic %) of the additive element in the absorption layer.

2. The reflective mask blank according to claim 1, characterized in that the absorbent membrane comprises tantalum (Ta) and nitrogen (N), and at least one additive element selected from hydrogen (H) and deuterium (D).

3. The reflective mask blank according to claim 1 or 2, characterized in that the concentration (atomic percent) of the additive element in the protective film is greater than 5 atomic percent.

4. The reflective mask blank according to any one of claims 1 to 3, characterized in that the protective film contains a Ru alloy in which Ru contains at least one metal selected from titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), lanthanum (La), cobalt (Co), and rhenium (Re).

5. The reflective mask blank according to any one of claims 1 to 4, characterized in that the concentration (atomic percent) of the additive element in the absorption layer is 0.1 atomic percent or more and 30 atomic percent or less.

6. The reflective mask blank according to any one of claims 1 to 5, characterized in that the absorption layer further contains boron (B), and the concentration of nitrogen (atomic %) is less than the concentration of boron (atomic %).

7. A reflective mask characterized in that the absorbent film in the reflective mask blank according to any one of claims 1 to 6 has a patterned absorbent pattern.

8. A method for manufacturing a semiconductor device, characterized by comprising the steps of setting a reflective mask according to claim 7 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a substrate to be transferred.

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