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

Abstract

The present invention provides a reflective mask blank capable of preventing electrostatic breakdown from occurring at the periphery of a substrate, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device. The reflective mask blank (100) comprises a substrate (10), a multilayer reflective film (12) on the substrate (10), a protective film (14) on the multilayer reflective film (12), and an absorbent film (16) on the protective film (14). The absorbent film (16) comprises a buffer layer (18) and an absorbing layer (20) installed on the buffer layer (18). When the distance from the center of the substrate (10) to the outer edge of the protective film (14) is Lcap and the distance from the center of the substrate (10) to the outer edge of the buffer layer (18) is Lbuf, Lcap ≤ Lbuf. In a range of 0.5 mm from the side of the substrate (10) toward the center of the substrate (10), there is at least one location where the total film thickness of the protective film (14) and the buffer layer (18) is 4.5 nm or more.

Description

Technology Field

[0001] The present invention relates to a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device. Background Technology

[0002] In recent years, with the increasing demand for higher density and precision in ultra-LSI devices, EUV lithography, an exposure technology using Extreme Ultra Violet (hereinafter referred to as EUV) light, is considered promising. EUV light refers to light in the wavelength range of the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm.

[0003] A reflective mask comprises a multilayer reflective film formed on a substrate for reflecting exposure light, and an absorber pattern formed on the multilayer reflective film, which is a patterned absorber film for absorbing exposure light. Light incident on the reflective mask, which is mounted on an exposure machine for performing pattern transfer on a semiconductor substrate, is absorbed in the areas where the absorber pattern is present and reflected by the multilayer reflective film in the areas where the absorber pattern is absent. The light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate, such as a silicon wafer, through a reflective optical system.

[0004] Generally, a multilayer film in which elements with different refractive indices are periodically stacked is used as a multilayer reflective film. For example, as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm, a Mo / Si periodic stacked film in which Mo films and Si films are alternately stacked for about 40 periods is preferably used.

[0005] Patent Document 1 describes a reflective mask blank in which a multilayer reflective film that reflects EUV light, a protective film for protecting the multilayer reflective film, an absorber film that absorbs EUV light, and a resist film are formed in sequence on a substrate, wherein L(ML) is the distance from the center of the substrate to the outer edge of the multilayer reflective film, L(Cap) is the distance from the center of the substrate to the outer edge of the protective film, L(Abs) is the distance from the center of the substrate to the outer edge of the absorber film, and L(Res) is the distance from the center of the substrate to the outer edge of the resist film, such that L(Abs) > ​​L(Res) > L(Cap) ≥ L(ML), and furthermore, the outer edge of the resist film is located on the center side rather than the outer edge of the substrate.

[0006] Patent Document 2 describes a reflective mask blank for exposure, comprising a substrate, a multilayer reflective film that reflects exposure light formed sequentially on the substrate, and an absorbing film that absorbs exposure light, wherein the multilayer reflective film is formed by alternately stacking a heavy element material film and a light element material film with different refractive indices, and is characterized by having a protective layer that protects at least the peripheral end portion of the heavy element material film among the multilayer reflective films. Additionally, Patent Document 2 describes forming an absorbing film in a film formation area that is larger than the film formation area of ​​the multilayer reflective film. Prior art literature

[0007] International Publication No. 2014 / 021235, Japanese Patent Publication No. 2003-257824 The problem to be solved

[0008] A reflective mask blank generally has a structure in which a multilayer reflective film that reflects exposure light (EUV light) is formed on one main surface of a substrate, and an absorber film that absorbs exposure light (EUV light) is formed on the multilayer reflective film. When manufacturing a reflective mask using a reflective mask blank, first, a resist film for electron beam lithography is formed on the surface of the reflective mask blank. Next, a desired pattern is lithographed onto this resist film using an electron beam, and the pattern is developed to form a resist pattern. Subsequently, using this resist pattern as a mask, the absorber film is dry-etched to form an absorber pattern (transfer pattern). By doing this, a reflective mask with an absorber pattern formed on a multilayer reflective film can be manufactured.

[0009] FIG. 14 is an enlarged cross-sectional view of the outer edge of a conventional reflective mask blank (200). As shown in FIG. 14, the reflective mask blank (200) has a substrate (210), a multilayer reflective film (212) formed on the substrate (210), a protective film (214) formed on the multilayer reflective film (212), an absorbent film (216) formed on the protective film (214), an etching mask film (218) formed on the absorbent film (216), and a resist film (220) formed on the etching mask film (218). The protective film (214) has the function of protecting the multilayer reflective film (212) from dry etching and cleaning in the manufacturing process of the reflective mask. The etching mask film (218) is a film for forming an absorbent pattern (transfer pattern) by dry etching the absorbent film (216). The resist film (220) is a film for forming a pattern on the etching mask film (218). In addition, if the etching mask film (218) is not installed, a resist pattern is formed on the resist film (220), and using this resist pattern as a mask, the absorber film (216) is dry-etched to form an absorber pattern (transfer pattern).

[0010] A resist film (220) is formed on the entire surface of a reflective mask blank (200). In order to suppress dust generation by peeling off the resist film (220) at the periphery of the substrate (210), the resist film (220) at the periphery of the substrate where a mask pattern is not formed is usually removed (edge ​​rinse). This edge rinse is performed, for example, by removing the resist film (220) with a width of about 1 to 1.5 mm along the periphery of the substrate (210) using a resist peeling solution. As shown in FIG. 14, in the region (R) where the resist film (220) is removed by the edge rinse, the etching mask film (218) located beneath the resist film (220) is exposed.

[0011] In a reflective mask that uses EUV light as the exposure light, it is important to accurately manage the location of defects present on the multilayer reflective film. This is because defects present on the multilayer reflective film are almost impossible to correct and can become significant phase defects in the transfer pattern. For this reason, in the reflective mask blank (200), a reference mark may be formed to manage the location of defects on the multilayer reflective film (212). This reference mark may also be called a fiducial mark.

[0012] FIG. 15 is an enlarged cross-sectional view of the outer edge of a reflective mask blank (200) on which a reference mark (FM) is formed. As shown in FIG. 15, the reference mark (FM) is formed in an area outside the region (PA) where a pattern is formed on the absorber film (216). When forming the reference mark (FM), first, a resist pattern (220a) for forming the reference mark (FM) is formed on the resist film (220) by electron beam lithography, and the reference mark (FM) is formed by etching the etching mask film (218) and the absorber film (216) by dry etching using the resist pattern (220a) as a mask.

[0013] As described above, in the area (R) where the resist film (220) is removed by edge rinsing, the etching mask film (218) located beneath the resist film (220) is exposed. Because of this, the etching mask film (218) and the absorber film (216) located in the area (R) where the resist film (220) is removed are removed by dry etching when forming the reference mark (FM), so the protective film (214) located beneath the absorber film (216) is exposed. At this time, as the exposed protective film (214) is damaged by etching, an isolated island-shaped protective film (214a) may be formed as shown in FIG. 16. This isolated island-shaped protective film (214a) is a part separated from the surroundings and is not connected to the protective film (214b) on the central side of the substrate (210).

[0014] When a high-level protective film (214a) is formed, the high-level protective film (214a) becomes charged during electron beam lithography to form a pattern on the absorber film (216). When the high-level protective film (214a) is charged, since there is no means (e.g., a conductive pin) installed on the high-level protective film (214a) to discharge the charge, electrostatic failure may occur as the charge is discharged from the high-level protective film (214a) all at once. This was a problem because if the reflective mask blank (200) is damaged by electrostatic failure, the reflective mask blank (200) becomes useless as a product.

[0015] The present invention is made to solve the above-mentioned problem and aims to provide a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device that can prevent electrostatic breakdown from occurring at the periphery of a substrate. means of solving the problem

[0016] To solve the above problem, the present invention has the following configuration.

[0017] (Composition 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,

[0018] The above absorbent membrane has a buffer layer and an absorbent layer installed on the buffer layer, and

[0019] When the distance from the center of the substrate to the outer edge of the protective film is Lcap and the distance from the center of the substrate to the outer edge of the buffer layer is Lbuf, Lcap ≤ Lbuf, and

[0020] A reflective mask blank characterized by having at least one location within a range of 0.5 mm from the side of the substrate toward the center of the substrate, wherein the total film thickness of the protective film and the buffer layer is 4.5 nm or more.

[0021] (Configuration 2) The above buffer layer comprises at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y), characterized in that it is a reflective mask blank described in Configuration 1.

[0022] (Configuration 3) A reflective mask blank as described in Configuration 1 or 2, characterized in that the total film thickness of the protective film and the buffer layer at the center of the substrate is 4.5 nm or more and 35 nm or less.

[0023] (Configuration 4) A reflective mask blank according to any one of configurations 1 to 3, characterized in that when the distance from the center of the substrate to the outer edge of the absorption layer is denoted as Labs, Lcap ≤ Labs.

[0024] (Configuration 5) The above protective film is a reflective mask blank described in any one of configurations 1 to 4, characterized by including ruthenium (Ru).

[0025] (Configuration 6) A reflective mask blank according to any one of configurations 1 to 5, characterized in that a resist film is provided on the absorbing film, and when the distance from the center of the substrate to the outer edge of the resist film is Lres, Lres < Lcap ≤ Lbuf.

[0026] (Composition 7)

[0027] A reflective mask characterized in that the absorption layer in the reflective mask blank described in any one of configurations 1 to 6 has a patterned absorbent pattern.

[0028] (Configuration 8) A reflective mask described in Configuration 7, characterized in that a reference mark is formed on the absorption layer of the absorbent membrane.

[0029] (Configuration 9) A method for manufacturing a reflective mask characterized by patterning the absorption layer of a reflective mask blank described in any one of configurations 1 to 6 to form an absorbent pattern.

[0030] (Composition 10)

[0031] A method for manufacturing a semiconductor device characterized by having a process of setting a reflective mask described in configuration 7 or 8 in an exposure device having an exposure light source that emits EUV light, and transferring a transfer pattern onto a resist film formed on a transfer substrate. Effects of the invention

[0032] According to the present invention, a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device can be provided, which can prevent electrostatic breakdown from occurring in the periphery of a substrate. Brief explanation of the drawing

[0033] FIG. 1 is a schematic cross-sectional view showing an example of a reflective mask blank of the present embodiment, and is an enlarged view of the outer periphery of a substrate. FIG. 2 is a schematic cross-sectional view showing another example of a reflective mask blank of the present embodiment, and is an enlarged view of the outer periphery of the substrate. Figure 3 is an enlarged cross-sectional view of the outer edge of a reflective mask blank with a reference mark formed thereon. Figure 4 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 5 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 6 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 7 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 8 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 9 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 10 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. Figure 11 is a schematic diagram illustrating the relationship between the protective film, buffer layer, absorption layer, etching mask film, and resist film. FIG. 12a is a schematic diagram showing an example of a method for manufacturing a reflective mask. FIG. 12b is a schematic diagram further illustrating an example of a method for manufacturing a reflective mask. FIG. 12c is a schematic diagram further illustrating an example of a method for manufacturing a reflective mask. FIG. 12d is a schematic diagram further illustrating an example of a method for manufacturing a reflective mask. FIG. 12e is a schematic diagram further illustrating an example of a method for manufacturing a reflective mask. FIG. 12f is a schematic diagram further illustrating an example of a method for manufacturing a reflective mask. Figure 13 is a diagram showing the schematic configuration of an EUV exposure device. FIG. 14 is an enlarged cross-sectional view of the outer end of a conventional reflective mask blank. FIG. 15 is an enlarged cross-sectional view of the outer end of a conventional reflective mask blank in which a reference mark (FM) is formed. FIG. 16 is an enlarged cross-sectional view of the outer end of a conventional reflective mask blank in which a protective film of the high-grade type is formed. Specific details for implementing the invention

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Furthermore, the following embodiments are forms intended to specifically explain the present invention and do not limit the scope of the present invention.

[0035] FIG. 1 is a schematic cross-sectional view showing an example of a reflective mask blank (100) of the present embodiment, and is an enlarged view of the outer periphery of a substrate (10). The reflective mask blank (100) shown in FIG. 1 has a substrate (10), a multilayer reflective film (12) formed on the substrate (10), a protective film (14) formed on the multilayer reflective film (12), and an absorbent film (16) formed on the protective film (14). The absorbent film (16) has a two-layer structure and includes a buffer layer (18) formed to be in contact with the protective film (14) and an absorption layer (20) formed on the buffer layer (18). On the back side of the substrate (10) (the side opposite to the side where the multilayer reflective film (12) is formed), a back side conductive film (22) for an electrostatic chuck may be formed.

[0036] Furthermore, in this specification, the term "on" a substrate or film includes not only cases where it is in contact with the upper surface of the substrate or film, but also cases where it is not in contact with the upper surface of the substrate or film. That is, the term "on" a substrate or film includes cases where a new film is formed on the upper surface of the substrate or film, or where another film is interposed between the substrate or film. Also, the term "on" does not necessarily mean the upper side in the vertical direction. The term "on" merely indicates the relative positional relationship of the substrate or film.

[0037] <Circuit Board>

[0038] The substrate (10) is preferably used to have a low coefficient of thermal expansion within the range of 0±5 ppb / ℃ in order to prevent distortion of the transfer pattern due to heat during exposure to EUV light. For example, materials having a low coefficient of thermal expansion within this range may include SiO2-TiO2 glass, multi-component glass ceramics, etc.

[0039] It is preferable that the main surface of the substrate (10) on the side where the transfer pattern (the absorber pattern described later) is formed be processed to increase flatness. By increasing the flatness of the main surface of the substrate (10), the positional precision of the pattern and the transfer precision can be increased. For example, in the case of EUV exposure, in the 132 mm × 132 mm area of ​​the main surface of the substrate (10) on the side where the transfer pattern is formed, it is preferable that the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In addition, the main surface (back side) on the side opposite to the side where the transfer pattern is formed is a surface fixed by an electrostatic chuck to the exposure device, and in the 142 mm × 142 mm area, the flatness is 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. In addition, in this specification, flatness is a value indicating the warping (deformation amount) of a surface represented by TIR (Total Indicated Reading), and is defined by the least squares method with respect to the substrate surface as the hyperplane, and is the absolute value of the difference in height between the highest position of the substrate surface above the hyperplane and the lowest position of the substrate surface below the hyperplane.

[0040] In the case of EUV exposure, the surface roughness of the main surface on the side where the transfer pattern of the substrate (10) is formed is preferably 0.1 nm or less as root mean square roughness (Rq). In addition, the surface roughness can be measured using an atomic force microscope.

[0041] It is desirable for the substrate (10) to have high rigidity to prevent deformation caused by film stress of a film (multilayer reflective film (12), etc.) formed thereon. In particular, it is desirable to have a high Young's modulus of 65 GPa or higher.

[0042] <Multilayer Reflective Film>

[0043] The multilayer reflective film (12) has a configuration in which multiple layers of elements with different refractive indices are periodically stacked. Generally, the multilayer reflective film (12) is composed of a multilayer film in which a thin film of a light element or its compound, which is a high refractive index material (high refractive index layer), and a thin film of a heavy element or its compound, which is a low refractive index material (low refractive index layer), are alternately stacked for about 40 to 60 cycles.

[0044] To form a multilayer reflective film (12), a high-refractive-index layer and a low-refractive-index layer may be stacked in this order multiple times from the substrate (10) side. In this case, one stacked structure of (high-refractive-index layer / low-refractive-index layer) becomes one period.

[0045] In addition, the uppermost layer of the multilayer reflective film (12), that is, the surface layer opposite to the substrate (10) of the multilayer reflective film (12), is preferably a high refractive index layer. When the high refractive index layer and the low refractive index layer are stacked in this order from the substrate (10) side, the uppermost layer becomes the low refractive index layer. However, if the low refractive index layer is the surface of the multilayer reflective film (12), the low refractive index layer is easily oxidized, causing the reflectance of the surface of the multilayer reflective film to decrease; therefore, it is preferable to form the high refractive index layer on the low refractive index layer. On the other hand, when the low refractive index layer and the high refractive index layer are stacked in this order from the substrate (10) side, the uppermost layer becomes the high refractive index layer. In that case, the high refractive index layer of the uppermost layer becomes the surface of the multilayer reflective film (12).

[0046] The high refractive index layer included in the multilayer reflective film (12) is a layer made of a material containing Si. The high refractive index layer may include Si as a single element or Si as a compound. The Si compound may include Si and at least one element selected from the group consisting of B, C, N, O, and H. By using a layer containing Si as the high refractive index layer, a multilayer reflective film with excellent reflectivity of EUV light is obtained.

[0047] The low-refractive-index layer included in the multilayer reflective film (12) is a layer made of a material including a transition metal. The transition metal included in the low-refractive-index layer is preferably at least one transition metal selected from the group consisting of Mo, Ru, Rh, and Pt. It is more preferable that the low-refractive-index layer is a layer made of a material including Mo.

[0048] For example, as a multilayer reflective film (12) for EUV light of wavelength 13 to 14 nm, preferably, a Mo / Si multilayer film can be used in which Mo films and Si films are alternately stacked for about 40 to 60 cycles.

[0049] The reflectance of such a multilayer reflective film (12) alone is, for example, 65% or more. The upper limit of the reflectance of the multilayer reflective film (12) is, for example, 73%. In addition, the thickness and period of the layers included in the multilayer reflective film (12) can be selected to satisfy Bragg's law.

[0050] The multilayer reflective film (12) can be formed by a known method. The multilayer reflective film (12) can be formed, for example, by an ion beam sputtering method.

[0051] For example, when the multilayer reflective film (12) is a Mo / Si multilayer film, a Mo film with a thickness of about 3 nm is formed on the substrate (10) using a Mo target by ion beam sputtering. Next, a Si film with a thickness of about 4 nm is formed using a Si target. By repeating this operation, a multilayer reflective film (12) with 40 to 60 cycles of Mo / Si films can be formed. At this time, the surface layer opposite to the substrate (10) of the multilayer reflective film (12) is a layer containing Si (Si film). The thickness of the Mo / Si film in one cycle is 7 nm.

[0052] <Protective Shield>

[0053] The reflective mask blank (100) of the present embodiment has a protective film (14) formed on a multilayer reflective film (12). The protective film (14) has the function of protecting the multilayer reflective film (12) from dry etching and cleaning during the manufacturing process of the reflective mask (110) described later. In addition, the protective film (14) also has the function of protecting the multilayer reflective film (12) when correcting black defects in a transfer pattern using an electron beam (EB). By forming the protective film (14) on the multilayer reflective film (12), damage to the surface of the multilayer reflective film (12) during the manufacturing of the reflective mask (110) can be suppressed. As a result, the reflectance characteristics of the multilayer reflective film (12) with respect to EUV light are improved.

[0054] The protective film (14) can be formed using known methods. Examples of methods for forming the protective film (14) include ion beam sputtering, magnetron sputtering, reactive sputtering, chemical vapor deposition (CVD), and vacuum deposition. The protective film (14) may be formed continuously by ion beam sputtering after the formation of the multilayer reflective film (12).

[0055] The protective film (14) can be formed from a material with different etching selectivity from the buffer layer (18). For example, materials such as Ru, Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo), Si-(Ru, Rh, Cr, B), Si, Zr, Nb, La, B, etc. can be used as the material for the protective film (14). Among these, if a material containing ruthenium (Ru) is applied, the reflectivity characteristics of the multilayer reflective film (12) become better. Specifically, it is preferable to use Ru or Ru-(Nb, Rh, Zr, Y, B, Ti, La, Mo). Such a protective film (14) is particularly effective when the buffer layer (18) is patterned by dry etching with a chlorine-based gas or a fluorine-based gas.

[0056] <Absorbent Membrane>

[0057] As described above, the absorbent membrane (16) includes a buffer layer (18) formed to be in contact with the protective membrane (14) and an absorbent layer (20) formed on the buffer layer (18).

[0058] The basic function of the absorbing film (16) (including the absorbing layer (20) and the buffer layer (18)) is to absorb EUV light. The absorbing film (16) may be an absorbing film (16) intended for the absorption of EUV light, or it may be an absorbing film (16) having a phase shift function that takes into account the phase difference of EUV light. An absorbing film (16) having a phase shift function is one that absorbs EUV light and simultaneously reflects a portion of it to shift the phase. That is, in a reflective mask patterned with an absorbing film (16) having a phase shift function, in the part where the absorbing film (16) is formed, EUV light is absorbed and photosensitive, while a portion of the light is reflected at a level that does not adversely affect pattern transfer. Also, in the area (field part) where the absorbing film (16) is not formed, EUV light is reflected from the multilayer reflective film (12) through the protective film (14). Therefore, a desired phase difference is created between the reflected light from the absorber film (16) having a phase shift function and the reflected light from the field portion. It is preferable that the absorber film (16) having a phase shift function be formed such that the phase difference between the reflected light from the absorber film (16) and the reflected light from the multilayer reflector film (12) is 170 degrees to 190 degrees. As the light with an inverted phase difference of approximately 180 degrees interferes with each other at the pattern edge portion, the image contrast of the projected optical image is improved. Along with the improvement in image contrast, the resolution increases, and various margins related to exposure, such as exposure amount margin and focus margin, can be greatly increased.

[0059] The absorption layer (20) in the absorbing film (16) is a film that primarily performs the function of the absorbing film (16) described above, and may be a single-layer film or a multilayer film composed of multiple films. In the case of a single-layer film, the number of process steps during mask blank manufacturing can be reduced, thereby improving production efficiency. In the case of a multilayer film, the optical constant and film thickness can be appropriately set so that the upper absorption layer becomes an anti-reflection film during mask pattern defect inspection using light. By doing so, the inspection sensitivity during mask pattern defect inspection using light is improved. In addition, if a film containing oxygen (O) and nitrogen (N), which improve oxidation resistance, is added to the upper absorption layer, stability over time is improved. In this way, by making the absorption layer (20) a multilayer film, it becomes possible to add various functions to the absorption layer (20). When the absorption layer (20) has a phase shift function, by making it a multilayer film, the range of adjustment in the optical plane can be greatly increased, making it easier to obtain the desired reflectance.

[0060] The material of the absorption layer (20) is not particularly limited as long as it is a material that has the function of absorbing EUV light, can be processed by etching, etc. (preferably etched by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity ratio with respect to the buffer layer (18). As having such a function, at least one metal selected from palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), chromium (Cr), cobalt (Co), manganese (Mn), tin (Sn), tantalum (Ta), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc (Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y), and silicon (Si), or a compound thereof, may be preferably used.

[0061] The absorption layer (20) can be formed by a magnetron sputtering method such as DC sputtering and RF sputtering. For example, the absorption layer (20), such as a tantalum compound, can be formed by a reactive sputtering method using argon gas with added oxygen or nitrogen, using a target containing tantalum and boron.

[0062] The tantalum compound for forming the absorption layer (20) includes an alloy of Ta and the metal described above. When the absorption layer (20) is an alloy of Ta, in terms of smoothness and flatness, the crystalline state of the absorption layer (20) is preferably an amorphous or microcrystalline structure. If the surface of the absorption layer (20) is not smooth or flat, the edge roughness of the absorber pattern described later increases, and the dimensional accuracy of the pattern may be poor. The preferred surface roughness of the absorption layer (20) is root mean square roughness (Rms), which is 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less.

[0063] Examples of tantalum compounds for forming an absorption layer (20) include a compound containing Ta and B, a compound containing Ta and N, a compound containing Ta, O and N, a compound containing Ta and B and also containing at least one of O and N, a compound containing Ta and Si, a compound containing Ta, Si and N, a compound containing Ta and Ge, and a compound containing Ta, Ge and N.

[0064] Ta is a material that has a high absorption coefficient of EUV light and can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, Ta can be considered a material for an absorption layer (20) with excellent processability. In addition, by adding B, Si and / or Ge, etc. to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorption layer (20) can be improved. Also, by adding N and / or O to Ta, the resistance to oxidation of the absorption layer (20) is improved, so the stability over time can be improved.

[0065] <Etching Mask>

[0066] FIG. 2 is a schematic cross-sectional view showing another example of a reflective mask blank (100) of the present embodiment, and is an enlarged view of the outer periphery of a substrate (10). As shown in FIG. 2, the reflective mask blank (100) may additionally have another thin film, such as a resist film (26), on the absorber film (16). Also, the reflective mask blank (100) may additionally have an etching mask film (24) between the absorber layer (20) and the resist film (26).

[0067] As for the material of the etching mask film (24), it is preferable to use a material that has a high etching selectivity ratio of the absorption layer (20) to the etching mask film (24). The etching selectivity ratio of the absorption layer (20) to the etching mask film (24) is preferably 1.5 or higher, and more preferably 3 or higher.

[0068] The reflective mask blank (100) of the present embodiment preferably has an etching mask film (24) containing chromium (Cr) on the absorption layer (20). When etching the absorption layer (20) with a fluorine-based gas, it is preferable to use chromium or a chromium compound as the material for the etching mask film (24). Examples of chromium compounds include materials containing Cr and at least one element selected from N, O, C, and H. It is more preferable that the etching mask film (24) includes CrN, CrO, CrC, CrON, CrOC, CrCN, or CrOCN, and it is particularly preferable to use a material containing Cr and N and / or O. Specific examples of such materials include CrN, CrO, and CrON.

[0069] When the absorption layer (20) is etched with a chlorine-based gas that is substantially oxygen-free or with a mixed gas of chlorine-based gas and oxygen gas, it is preferable to use silicon or a silicon compound as the material for the etching mask film (24). Examples of silicon compounds include materials containing Si and at least one element selected from N, O, C, and H, metallic silicon (metal silicide) containing a metal in silicon and silicon compounds, and metallic silicon compounds (metal silicide compounds). Examples of metallic silicon compounds include materials containing a metal, Si, and at least one element selected from N, O, C, and H. Among these, it is particularly preferable to use a material containing Si and N and / or O as the material for the etching mask film (24). Specific examples of such materials include SiN and SiO.

[0070] When the absorption layer (20) is etched with a chlorine-based gas that is substantially oxygen-free or with a mixed gas of chlorine-based gas and oxygen gas, an etching mask film (24) containing tantalum (Ta) may be used. As a material containing Ta, a material containing one or more elements selected from O, N, C, B, and H may be used. Among these, it is particularly preferable to use a material containing Ta and O as the material for the etching mask film (24). Specific examples of such materials may include TaO, TaON, TaBO, and TaBON.

[0071] In addition, as a material for the etching mask film (24), at least one metal selected from iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf) and yttrium (Y), or a compound thereof may be used.

[0072] The thickness of the etching mask film (24) is preferably 3 nm or more in order to form a pattern on the absorption layer (20) with good precision. In addition, the thickness of the etching mask film (24) is preferably 15 nm or less in order to make the thickness of the resist film (26) thin.

[0073] <Backside Challenge Screen>

[0074] A back surface conductive film (22) for an electrostatic chuck may be formed on the back surface of the substrate (10) (the side opposite to the side where the multilayer reflective film (12) is formed). For an electrostatic chuck, the sheet resistance required for the back surface conductive film (22) is typically 100Ω / □ (Ω / square) or less. The back surface conductive film (22) can be formed by a magnetron sputtering method or an ion beam sputtering method using a target of a metal such as chromium or tantalum, or an alloy thereof, for example. The material of the back surface conductive film (22) is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back surface conductive film (22) is preferably a Cr compound containing at least one selected from boron, nitrogen, oxygen, and carbon in addition to Cr. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Additionally, the material of the back conductive film (22) is preferably 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.

[0075] The thickness of the back conductive film (22) is not particularly limited as long as it functions as a film for an electrostatic chuck, but is, for example, 10 nm to 200 nm.

[0076] Below, the above-described buffer layer (18) will be explained in detail.

[0077] As shown in FIG. 2, a resist film (26) is formed on the front surface of a reflective mask blank (100). In order to suppress peeling and oscillation of the resist film (26) at the periphery of the substrate (10), the resist film (26) at the periphery of the substrate where the mask pattern is not formed is usually removed (edge ​​rinse). In the region (R) where the resist film (26) is removed by the edge rinse, the etching mask film (24) located beneath the resist film (26) is exposed. Additionally, in the case of a reflective mask blank (100) without an etching mask film (24), the absorption layer (20) is exposed.

[0078] In a reflective mask that uses EUV light as the exposure light, it is important to accurately manage the location of defects present on the multilayer reflective film (12). This is because defects present on the multilayer reflective film (12) are almost impossible to correct and can become significant phase defects in the transfer pattern. For this reason, in the reflective mask blank (100), a reference mark is formed to manage the location of defects on the multilayer reflective film (12). This reference mark is sometimes called a fiducial mark.

[0079] FIG. 3 is an enlarged cross-sectional view of the outer edge of a reflective mask blank (100) on which a reference mark (FM) is formed. As shown in FIG. 3, the reference mark (FM) is formed in an area outside the region (PA) where a pattern is formed on the absorption layer (20). When forming the reference mark (FM), first, a resist pattern (26a) for forming the reference mark (FM) is formed on the resist film (26) by electron beam lithography, and the reference mark (FM) is formed by etching the etching mask film (24) and the absorption layer (20) by dry etching using the resist pattern (26a) as a mask.

[0080] As described above, in the area (R) where the resist film (26) is removed by edge rinsing, the etching mask film (24) (or absorption layer (20)) located beneath the resist film (26) is exposed. Because of this, the etching mask film (24) and the absorption layer (20) in the area (R) where the resist film (26) is removed are removed by dry etching when forming a reference mark (FM) on the absorption layer (20).

[0081] In the reflective mask blank (100) of the present embodiment, the absorbing film (16) includes a buffer layer (18) formed to be in contact with a protective film (14) and an absorbing layer (20) formed on the buffer layer (18). The buffer layer (18) is a layer that has etching resistance to the absorbing layer (20) and is a layer that prevents the formation of a protective film of a high degree.

[0082] For this reason, in the region (R) where the resist film (26) is removed by edge rinse, even if the etching mask film (24) and the absorption layer (20) are removed by dry etching when forming the reference mark (FM), the buffer layer (18) remains on the protective film (14), so it is possible to prevent the protective film (14) from being damaged by etching.

[0083] The buffer layer (18) can be formed by a known film formation method. The buffer layer (18) can be formed by, for example, a magnetron sputtering method such as DC sputtering and RF sputtering.

[0084] The material of the buffer layer (18) is not particularly limited, but it is preferable that it be a material resistant to the etchant used for dry etching when forming a reference mark (FM) on the absorption layer (20). The buffer layer (18) can be formed, for example, from a material such as the etching mask film (24) described above. The buffer layer (18) preferably comprises at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y). In addition, in the case of a reflective mask blank (100) having an etching mask film (24), it is preferable that the buffer layer (18) be formed from a material such as the etching mask film (24).

[0085] According to the reflective mask blank (100) of the present embodiment, since a buffer layer (18) remains on the protective film (14), it is possible to prevent the protective film (14) from being damaged by dry etching when forming the reference mark (FM). Because of this, it is possible to prevent the occurrence of a “high-grade protective film” that was previously generated when forming the reference mark (FM), and it is possible to prevent electrostatic failure caused by the high-grade protective film becoming charged.

[0086] In the reflective mask blank (100) of the present embodiment, when the distance from the center of the substrate (10) to the outer edge of the protective film (14) is Lcap and the distance from the center of the substrate (10) to the outer edge of the buffer layer (18) is Lbuf, Lcap ≤ Lbuf. When the protective film (14) and the buffer layer (18) satisfy these conditions, the buffer layer (18) remains on the protective film (14) in the region (R) where the resist film (26) is removed by edge rinse. Since the buffer layer (18) remains on the protective film (14), it is possible to prevent the formation of a high-grade protective film (14) in the region (R) where the resist film (26) is removed by edge rinse.

[0087] In the reflective mask blank (100) of the present embodiment, there is at least one location in which the total film thickness (T) of the protective film (14) and the buffer layer (18) is 4.5 nm or more within a range of 0.5 mm from the side of the substrate (10) toward the center of the substrate (10). When the protective film (14) and the buffer layer (18) satisfy these conditions, in the region (R) where the resist film (26) is removed by edge rinse (the region (R) is typically a region with a width of about 1 to 1.5 mm from the side of the substrate (10) toward the center of the substrate (10), the buffer layer (18) remains on the protective film (14), and there is at least one location in which the total film thickness (T) of the protective film (14) and the buffer layer (18) is 4.5 nm or more. As a result, in the region (R) where the resist film (26) is removed by edge rinse, it is possible to secure a sufficiently large total film thickness (T) of the protective film (14) and the buffer layer (18), thereby making it possible to more reliably prevent the occurrence of a high-grade protective film (14). In addition, in the range of 0.5 mm from the side of the substrate (10) toward the center of the substrate (10), the total film thickness (T) of the protective film (14) and the buffer layer (18) is preferably 5.0 nm or more, and more preferably 5.5 nm or more. Also, the total film thickness (T) is preferably 35 nm or less, and more preferably 30 nm or less.

[0088] In the reflective mask blank (100) of the present embodiment, the total film thickness of the protective film (14) and the buffer layer (18) at the center of the substrate (10) is preferably 4.5 nm or more, and more preferably 5.5 nm or more. In addition, the total film thickness is preferably 35 nm or less, and more preferably 30 nm or less. When the protective film (14) and the buffer layer (18) satisfy these conditions, it becomes possible to secure a sufficiently large total film thickness (T) of the protective film (14) and the buffer layer (18) even in the region (R) where the resist film (26) is removed by edge rinse, so it becomes possible to more reliably prevent the occurrence of a high-grade protective film (14).

[0089] In addition, in the present specification, the center of the substrate (10) refers to the position of the center of gravity (the position of a point on the main surface (10a) of the substrate (10) corresponding to the position of the center) in the case of a rectangular (e.g., square) substrate (10). Also, the side surface (10b) of the substrate (10) is a plane approximately perpendicular to the two main surfaces of the substrate (10) and is sometimes referred to as the "T-plane." The outer edge of the film or layer refers to the end of the film or layer located furthest from the center of the substrate (10).

[0090] In addition, the film formation area (distance from the center of the substrate to the outer edge) and inclined cross-sectional shape (gradient profile) of the protective film (14), buffer layer (18), absorption layer (20), and etching mask film (24) at the outer edge of the substrate (10) can be appropriately adjusted according to the opening dimensions of the PVD shield, the taper shape of the opening, the gap between the shield and the substrate, etc.

[0091] FIGS. 4 to 11 are schematic diagrams for explaining the relationship between the protective film (14), buffer layer (18), absorption layer (20), etching mask film (24), and resist film (26) in the reflective mask blank (100) of the present embodiment. In addition, in FIGS. 4 to 11, for the simplification of the drawings, the thickness of each layer is made almost constant toward its outer edge.

[0092] Here, the distance from the center of the substrate (10) to the outer edge of each layer is defined as follows.

[0093] Lcap: Distance from the center of the substrate (10) to the outer edge of the protective film (14).

[0094] Lbuf: Distance from the center of the substrate (10) to the outer edge of the buffer layer (18).

[0095] Labs: Distance from the center of the substrate (10) to the outer edge of the absorption layer (20).

[0096] Letc: Distance from the center of the substrate (10) to the outer edge of the etching mask film (24)

[0097] Lres: Distance from the center of the substrate (10) to the outer edge of the resist film (26).

[0098] In Figure 4, Lres < Lcap < Lbuf < Labs < Letc.

[0099] When dry etching to form a reference mark (FM), the etching mask film (24) and the absorption layer (20) that are not covered by the resist film (26) are removed by etching, so the area enclosed by the dotted line in FIG. 4 is removed. Even in this case, since the front surface of the protective film (14) is maintained in a state covered by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0100] In Figure 5, Lres < Lcap < Labs < Lbuf < Letc.

[0101] When dry etching to form a reference mark (FM), the etching mask film (24) that is not covered by the resist film (26) is removed by dry etching. When the etching mask film (24) and the buffer layer (18) are etched by the same etchant (for example, when the etching mask film (24) and the buffer layer (18) are made of the same material), the buffer layer (18) that is not covered by the absorption layer (20) is etched by the same etchant as the etching mask film (24) (i.e., the buffer layer (18) and the etching mask film (24) are etched simultaneously). After that, since the absorption layer (20) that is not covered by the resist film (26) is etched by dry etching, the area enclosed by the dotted line in FIG. 5 is removed. Even in this case, since the front surface of the protective film (14) is maintained by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0102] In Fig. 6, Lres < Lcap < Lbuf < Letc < Labs.

[0103] When dry etching to form a reference mark (FM), the etching mask film (24) and the absorption layer (20) that are not covered by the resist film (26) are removed by etching, so the area enclosed by the dotted line in FIG. 6 is removed. Even in this case, since the front surface of the protective film (14) is maintained in a state covered by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0104] In Fig. 7, Lres < Lcap < Labs < Letc < Lbuf.

[0105] When dry etching to form a reference mark (FM), the etching mask film (24) that is not covered by the resist film (26) is removed by dry etching. When the etching mask film (24) and the buffer layer (18) are etched by the same etchant (for example, when the etching mask film (24) and the buffer layer (18) are made of the same material), the buffer layer (18) that is not covered by the absorption layer (20) is etched by the same etchant as the etching mask film (24) (i.e., the buffer layer (18) and the etching mask film (24) are etched simultaneously). After that, since the absorption layer (20) that is not covered by the resist film (26) is etched by dry etching, the area enclosed by the dotted line in FIG. 7 is removed. Even in this case, since the front surface of the protective film (14) is maintained by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0106] In Fig. 8, Lres < Lcap < Letc < Lbuf < Labs.

[0107] When dry etching to form a reference mark (FM), the etching mask film (24) and the absorption layer (20) that are not covered by the resist film (26) are removed by etching, so the area enclosed by the dotted line in FIG. 8 is removed. Even in this case, since the front surface of the protective film (14) is maintained in a state covered by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0108] In Fig. 9, Lres < Lcap < Letc < Labs < Lbuf.

[0109] When dry etching to form a reference mark (FM), the etching mask film (24) that is not covered by the resist film (26) is removed by dry etching. When the etching mask film (24) and the buffer layer (18) are etched by the same etchant (for example, when the etching mask film (24) and the buffer layer (18) are made of the same material), the buffer layer (18) that is not covered by the absorption layer (20) is etched by the same etchant as the etching mask film (24) (i.e., the buffer layer (18) and the etching mask film (24) are etched simultaneously). After that, since the absorption layer (20) that is not covered by the resist film (26) is etched by dry etching, the area enclosed by the dotted line in FIG. 9 is removed. Even in this case, since the front surface of the protective film (14) is maintained by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0110] In Fig. 10, Lres < Letc < Lcap < Lbuf < Labs.

[0111] When dry etching to form a reference mark (FM), the etching mask film (24) and the absorption layer (20) that are not covered by the resist film (26) are removed by etching, so the area enclosed by the dotted line in FIG. 10 is removed. Even in this case, since the front surface of the protective film (14) is maintained in a state covered by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0112] In Fig. 11, Lres < Letc < Lcap < Labs < Lbuf.

[0113] When dry etching to form a reference mark (FM), the etching mask film (24) that is not covered by the resist film (26) is removed by dry etching. When the etching mask film (24) and the buffer layer (18) are etched by the same etchant (for example, when the etching mask film (24) and the buffer layer (18) are made of the same material), the buffer layer (18) that is not covered by the absorption layer (20) is etched by the same etchant as the etching mask film (24) (i.e., the buffer layer (18) and the etching mask film (24) are etched simultaneously). After that, since the absorption layer (20) that is not covered by the resist film (26) is etched by dry etching, the area enclosed by the dotted line in FIG. 11 is removed. Even in this case, since the front surface of the protective film (14) is maintained by the buffer layer (18), it is possible to prevent the "high-grade protective film" from being damaged by etching on the protective film (14).

[0114] In the reflective mask blank (100) of the present embodiment, it is preferable that Lcap ≤ Labs. In the case where Lcap ≤ Labs, even if the etching mask film (24) and the buffer layer (18) are etched by the same etchant, the entire surface of the protective film (14) is maintained in a state covered by the buffer layer (18), so that the "high-grade protective film" can be more reliably prevented from being damaged by etching on the protective film (14).

[0115] In the reflective mask blank (100) of the present embodiment, it is preferable that Lres < Lcap ≤ Lbuf. When the resist film (26) on the periphery of the substrate (10) is removed by edge rinsing, Lres < Lcap is common. Even in this case, when dry etching to form a reference mark (FM), the entire surface of the protective film (14) is maintained in a state covered by the buffer layer (18), so that the "high-grade protective film" is more reliably prevented from being damaged by etching on the protective film (14).

[0116] <Method for Manufacturing a Reflective Mask>

[0117] A reflective mask (110) of the present embodiment can be manufactured using the reflective mask blank (100) of the present embodiment. Below, an example of a method for manufacturing a reflective mask (110) will be described.

[0118] FIGS. 12a through f are schematic diagrams showing an example of a method for manufacturing a reflective mask (110).

[0119] As shown in FIG. 12a, first, a reflective mask blank (100) is prepared having a substrate (10), a multilayer reflective film (12) formed on the surface of the substrate (10), a protective film (14) formed on the multilayer reflective film (12), an absorbent film (16) (buffer layer (18) and absorbent layer (20)) formed on the protective film (14), and a back surface conductive film (22) formed on the back surface of the substrate (10) (Fig. 12a). Next, a resist film (26) is formed on the absorbent film (16) (Fig. 12b). In order to suppress oscillation caused by peeling of the resist film (26) on the periphery of the substrate (27), the resist film (26) on the periphery of the substrate (27) is removed by a solvent in which the resist film (26) dissolves (edge ​​rinse) (Fig. 12c). A pattern is drawn on the resist film (26) by an electron beam drawing device, and a resist pattern (26a) is formed by additionally undergoing a developing and rinsing process (Fig. 12d).

[0120] Using the resist pattern (26a) as a mask, the absorption layer (20) of the absorbent film (16) is dry-etched. By doing so, the portion of the absorption layer (20) that is not covered by the resist pattern (26a) is etched, and a pattern is formed on the absorption layer (20) (Fig. 12e).

[0121] For example, fluorine-based gas and / or chlorine-based gas may be used as the etching gas for the absorption layer (20). As fluorine-based gas, CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, and F2 may be used. As chlorine-based gas, Cl2, SiCl4, CHCl3, CCl4, and BCl3 may be used. In addition, a mixed gas containing fluorine-based gas and / or chlorine-based gas and O2 in a predetermined ratio may be used. These etching gases may additionally include inert gases such as He and / or Ar as needed.

[0122] After a pattern is formed on the absorption layer (20), the absorber pattern (16a) is formed by patterning the buffer layer (18) by dry etching. The resist pattern (26a) is removed by a resist stripping solution. After removing the resist pattern (26a), the reflective mask (110) of the present embodiment is obtained by undergoing a wet cleaning process using an acidic or alkaline aqueous solution (Fig. 12f).

[0123] In addition, when using a reflective mask blank (100) on which an etching mask film (24) is formed on an absorbing film (16), a process is added in which a pattern (etching mask pattern) is formed on the etching mask film (24) using a resist pattern (26a) as a mask, and then a pattern is formed on the absorbing layer (20) using the etching mask pattern as a mask.

[0124] The reflective mask (110) obtained in this way has a configuration in which a multilayer reflective film (12), a protective film (14), and an absorber pattern (16a) are laminated on a substrate (10).

[0125] The area (30) where the multilayer reflective film (12) (including the protective film (14)) is exposed has the function of reflecting EUV light. The area (32) where the multilayer reflective film (12) (including the protective film (14)) is covered by the absorber pattern (16a) has the function of absorbing EUV light.

[0126] <Method for manufacturing a semiconductor device>

[0127] A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask (110) of the present embodiment. The transfer pattern has a shape in which the pattern of the reflective mask (110) is transferred. A semiconductor device can be manufactured by forming a transfer pattern on a semiconductor substrate using the reflective mask (110).

[0128] FIG. 13 shows a schematic configuration of an EUV exposure device (50) for transferring a transfer pattern onto a resist film formed on a semiconductor substrate (60). The EUV exposure device (50) has an EUV light generating unit (51), an irradiation optical system (56), a reticle stage (58), a projection optical system (57), and a wafer stage (59) precisely arranged along the optical path axis of the EUV light. Hydrogen gas is filled inside the container of the EUV exposure device (50).

[0129] The EUV light generation unit (51) has a laser light source (52), a tin droplet generation unit (53), a capture unit (54), and a collector (55). When a high-power carbon dioxide laser from the laser light source (52) is irradiated onto a tin droplet emitted from the tin droplet generation unit (53), the tin in the droplet state is plasmafied to generate EUV light. The generated EUV light is concentrated by the collector (55) and passes through the irradiation optical system (56) to be incident on a reflective mask (110) set on the reticle stage (58). The EUV light generation unit (51) generates, for example, EUV light with a wavelength of 13.53 nm.

[0130] EUV light reflected from the reflective mask (110) is reduced to approximately 1 / 4 of its normal size by the projection optical system (57) and projected onto the semiconductor substrate (60) (substrate to be transferred). By this, a circuit pattern is transferred to the resist film on the semiconductor substrate (60).

[0131] By developing the exposed resist film, a resist pattern can be formed on a semiconductor substrate (60). By etching the semiconductor substrate (60) using the resist pattern as a mask, an integrated circuit pattern can be formed on the semiconductor substrate. By undergoing such a process and other necessary processes, a semiconductor device can be manufactured.

[0132] Examples

[0133] Examples 1 to 3 and Comparative Example 1 will be described below.

[0134] First, a substrate (10) of size 6025 (approx. 152 mm × 152 mm × 6.35 mm) with a polished main surface was prepared. This substrate (10) is a substrate made of low thermal expansion glass (SiO2-TiO2 glass). The main surface of the substrate (10) was polished by a rough polishing process, a precision polishing process, a localized process, and a touch polishing process.

[0135] Next, a multilayer reflective film (12) was formed on the main surface of the substrate (10). The multilayer reflective film (12) formed on the substrate (10) was made of a periodic multilayer reflective film (12) composed of Mo and Si in order to be a multilayer reflective film (12) suitable for EUV light of a wavelength of 13.5 nm. The multilayer reflective film (12) was formed by alternately stacking Mo films and Si films on the substrate (10) by an ion beam sputtering method using Mo targets and Si targets and krypton (Kr) as a process gas. First, a Si film was deposited to a thickness of 4.2 nm, and then a Mo film was deposited to a thickness of 2.8 nm. This was considered one cycle, and after stacking for 40 cycles in the same manner, finally, a Si film was deposited to a thickness of 4.0 nm.

[0136] Next, a protective film (14) made of RuNb was formed on the multilayer reflective film (12). The protective film (14) was formed by magnetron sputtering in an Ar gas atmosphere using a RuNb target. The film thickness of the protective film (14) (film thickness at the center of the substrate (10)) was 3.5 nm.

[0137] Next, a buffer layer (18) was formed on the protective film (14). The composition and film thickness (film thickness at the center of the substrate (10)) of the buffer layer (18) are shown in Table 1 below. The buffer layer (18) of Examples 1 and 3 and Comparative Example 1 was formed by magnetron sputtering in a mixed gas atmosphere of Ar gas, O2 gas, and N2 gas using a Cr target. The buffer layer (18) of Example 2 was formed by magnetron sputtering in a mixed gas atmosphere of Ar gas and O2 gas using a TaB target.

[0138] Next, an absorption layer (20) was formed on the buffer layer (18). The composition and film thickness of the absorption layer (20) are shown in Table 1 below. The absorption layer (20) of Examples 1 and 3 and Comparative Example 1 was formed by magnetron sputtering in a mixed gas atmosphere of Ar gas and N2 gas using a TaB target. The absorption layer (20) of Example 2 was formed by magnetron sputtering in an Ar gas atmosphere using a RuCr target.

[0139] In Example 3, an etching mask film (24) made of CrON, such as the buffer layer (18), was additionally formed on the absorption layer (20). The thickness of the etching mask film (24) was 6 nm.

[0140] In Examples 1 and 2, the film of each layer was formed such that Lml < Lcap ≤ Lbuf ≤ Labs. In Example 3, the film of each layer was formed such that Lml < Lcap ≤ Lbuf < Labs = Letc. In Comparative Example 1, the film of each layer was formed such that Lml < Lbuf < Lcap. The meaning of each symbol is the same as the meaning defined above. Lml represents the distance from the center of the substrate (10) to the outer edge of the multilayer reflective film (12). In addition, the adjustment of the film formation range of each layer was performed by a method using a shielding member as disclosed in International Publication No. 2014 / 021235.

[0141] In Examples 1 to 3, the protective film (14) and the buffer layer (18) were formed such that, within a range of 0.5 mm from the side of the substrate (10) toward the center of the substrate (10), there is at least one location where the total film thickness of the protective film (14) and the buffer layer (18) is 4.5 nm or more, as shown in Table 1. In Comparative Example 1, the protective film (14) and the buffer layer (18) were formed such that, within a range of 0.5 mm from the side of the substrate (10) toward the center of the substrate (10), there is no location where the total film thickness of the protective film (14) and the buffer layer (18) is 4.5 nm or more. Additionally, the film thickness of each layer at the outer edge was adjusted according to the aperture dimensions of the PVD shield produced by the magnetron sputtering method.

[0142]

[0143] Next, a reflective mask (110) was produced using the reflective mask blank (100) prepared above.

[0144] Specifically, first, a resist film (26) was formed on the absorption layer (20) or the etching mask film (24). After forming the resist film (26), the resist film (26) on the periphery of the substrate was removed by a resist stripping solution (edge ​​rinse). After performing the edge rinse, a pattern was drawn on the resist film (26) by an electron beam lithography device to form a resist pattern (26a). Using the resist pattern (26a) as a mask, the absorption layer (20) was dry-etched to form a reference mark (FM). Additionally, the absorption layer (20) of Examples 1 and 3 and Comparative Example 1 was dry-etched using Cl2 gas, and the absorption layer (20) of Example 2 was dry-etched using a mixed gas of Cl2 gas and O2 gas. Also, in Example 3, a resist pattern (26a) was used as a mask, and an etching mask film (24) was dry-etched using a mixed gas of Cl2 gas and O2 gas to form an etching mask pattern. Then, using this etching mask pattern as a mask, an absorption layer (20) was dry-etched to form a reference mark (FM).

[0145] After forming a reference mark (FM) on the absorption layer (20), the resist pattern (26a) on the absorption layer (20) or the etching mask film (24) was removed by a resist stripping solution. Then, a resist film was formed on the absorption layer (20) or the etching mask film (24) to form an absorber pattern (16a). After forming a resist pattern by drawing a pattern on this resist film using an electron beam lithography device, the absorber pattern (16a) was formed by dry etching the absorption layer (20) and the buffer layer (18) using this resist pattern as a mask. Additionally, dry etching was performed on the absorption layer (20) of Examples 1 and 3 and Comparative Example 1 using Cl2 gas, and on the buffer layer (18) using a mixed gas of Cl2 gas and O2 gas. In addition, the absorption layer (20) of Example 2 was dry-etched using a mixed gas of Cl2 gas and O2 gas, and the buffer layer (18) was dry-etched using Cl2 gas. Also, in Example 3, an etching mask pattern was formed by dry-etching an etching mask film (24) using a resist pattern as a mask, and then the absorption layer (20) was dry-etched using this etching mask pattern as a mask, and the etching mask pattern was removed simultaneously with the dry-etching of the buffer layer (18) to form an absorber pattern (16a).

[0146] The upper surface of the outermost portion of the reflective mask (110) obtained in this way was observed using TEM. As a result, in the reflective masks of Examples 1 to 3, no high-grade protective film was found in the region (R) of the substrate periphery. In addition, no traces of electrostatic breakdown caused by the high-grade protective film were found.

[0147] Meanwhile, in the reflective mask of Comparative Example 1, a high-grade protective film was formed in the region (R) of the substrate periphery. In addition, traces of electrostatic breakdown caused by the high-grade protective film were confirmed. Explanation of the symbols

[0148] 10: Substrate 12: Multilayer reflective film 14: Protective barrier 16: Absorbent membrane 18: Buffer layer 20: Absorption layer 16a: Absorber pattern 22: Backside conductive film 24: Etching mask 26a: Resist pattern 26: Resist film 50: EUV exposure device 100: Reflective mask blank 110: Reflective mask

Claims

Claim 1 A reflective mask blank comprising a substrate, a multilayer reflective film on the substrate, a protective film on the multilayer reflective film, an absorbent film on the protective film, and an etching mask film on the absorbent film, wherein the absorbent film has a buffer layer and an absorbent layer installed on the buffer layer, and wherein Lcap ≤ Lbuf < Letc is given by Lcap, where Lcap is the distance from the center of the substrate to the outer edge of the protective film, Lbuf is the distance from the center of the substrate to the outer edge of the buffer layer, and Letc is the distance from the center of the substrate to the outer edge of the etching mask film. Claim 2 A reflective mask blank according to claim 1, wherein the buffer layer comprises at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y). Claim 3 A reflective mask blank according to claim 1 or 2, wherein the etching mask film comprises at least one selected from chromium (Cr), silicon (Si), tantalum (Ta), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y). Claim 4 A reflective mask blank according to claim 1 or 2, characterized in that when the distance from the center of the substrate to the outer edge of the absorption layer is denoted as Labs, Lcap < Labs. Claim 5 A reflective mask blank according to claim 1 or 2, wherein the protective film comprises ruthenium (Ru). Claim 6 A reflective mask blank according to claim 1 or 2, wherein a resist film is provided on the absorbent film, and when the distance from the center of the substrate to the outer edge of the resist film is Lres, Lres < Lcap ≤ Lbuf. Claim 7 A reflective mask characterized in that the absorption layer in the reflective mask blank described in claim 1 or 2 has a patterned absorber pattern. Claim 8 A reflective mask according to claim 7, characterized in that a reference mark is formed on the absorption layer of the absorbent membrane. Claim 9 A method for manufacturing a reflective mask characterized by patterning the absorption layer of the reflective mask blank described in claim 1 or 2 to form an absorbent pattern. Claim 10 A method for manufacturing a semiconductor device characterized by having a process of setting a reflective mask described in claim 7 in an exposure device 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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