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

Abstract

To provide a reflection type mask blank, a reflection type mask, a method for manufacturing a reflection type mask, and a method for manufacturing a semiconductor device which can prevent occurrence of electrostatic breakdown in a substrate peripheral part.SOLUTION: A reflection type mask blank 100 includes a substrate 10, a multilayer reflection film 12 on the substrate 10, a protective film 14 on the multilayer reflection film 12, and an absorber film 16 on the protective film 14. The absorber film 16 has a buffer layer 18, and an absorption layer 20 provided on the buffer layer 18. When a distance between a center of the substrate 10 and an outer peripheral end of the protective film 14 is represented by Lcap and a distance between the center of the substrate 10 and an outer peripheral end of the buffer layer 18 is represented by Lbuf, Lcap≤Lbuf is satisfied. In a range within 0.5 mm from the side face of the substrate 10 toward the center of the substrate 10, there exists at least one part in which the total film thickness of the protective film 14 and the buffer layer 18 is 4.5 nm or more.SELECTED DRAWING: Figure 1

Description

[Technical 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 VLSI devices, EUV lithography, an exposure technology using extreme ultraviolet (EUV) light, is seen as promising. EUV light refers to light in the wavelength band of the soft X-ray region or vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm.

[0003] A reflective mask has a multilayer reflective film formed on a substrate for reflecting exposure light, and an absorber pattern, which is a patterned absorber film formed on the multilayer reflective film for absorbing the exposure light. Light incident on a reflective mask mounted on an exposure machine for transferring a pattern onto a semiconductor substrate is absorbed in the area with the absorber pattern, and is reflected by the multilayer reflective film in the area without the absorber pattern. The optical image reflected by the multilayer reflective film is transferred onto a semiconductor substrate such as a silicon wafer through a reflection optical system.

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

[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 successively formed on a substrate, wherein, when the distance from the center of the substrate to the outer circumferential edge of the multilayer reflective film is L(ML), the distance from the center of the substrate to the outer circumferential edge of the protective film is L(Cap), the distance from the center of the substrate to the outer circumferential edge of the absorber film is L(Abs), and the distance from the center of the substrate to the outer circumferential edge of the resist film is L(Res), L(Abs)>L(Res)>L(Cap)≧L(ML), and the outer circumferential edge of the resist film is located inside the outer circumferential edge of the substrate.

[0006] Patent Document 2 describes a reflective mask blank for exposure comprising a substrate, a multilayer reflective film for reflecting exposure light and an absorbing film for absorbing exposure light, which are successively formed on the substrate, the multilayer reflective film being formed by alternately laminating heavy element material films and light element material films having different refractive indices, and characterized in that the multilayer reflective film has a protective layer for protecting at least the peripheral edge of the heavy element material film. Patent Document 2 also describes that an absorbing film is formed in a deposition region larger than the deposition region of the multilayer reflective film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 021235 [Patent Document 2] JP 2003-257824 A Summary of the Invention [Problem to be solved by the invention]

[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 a reflective mask is manufactured using a reflective mask blank, a resist film for electron beam drawing is first formed on the surface of the reflective mask blank. Next, a desired pattern is drawn on the resist film with an electron beam, and the pattern is developed to form a resist pattern. Next, the absorber film is dry-etched using the resist pattern as a mask to form an absorber pattern (transfer pattern). This allows the manufacture of a reflective mask in which an absorber pattern is formed on a multilayer reflective film.

[0009] FIG. 14 is an enlarged cross-sectional view of the outer peripheral end 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 absorber film 216 formed on the protective film 214, an etching mask film 218 formed on the absorber film 216, and a resist film 220 formed on the etching mask film 218. The protective film 214 has a 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 dry etching the absorber film 216 to form an absorber pattern (transfer pattern). The resist film 220 is a film for forming a pattern in the etching mask film 218. When the etching mask film 218 is not provided, a resist pattern is formed in the resist film 220, and the absorber film 216 is dry etched using this resist pattern as a mask to form an absorber pattern (transfer pattern).

[0010] The resist film 220 is formed on the entire surface of the reflective mask blank 200, but in order to prevent the resist film 220 from peeling off and generating dust at the peripheral portion of the substrate 210, the resist film 220 at the peripheral portion of the substrate where the 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 peripheral portion of the substrate 210 using a resist stripper. As shown in FIG. 14, in the region R where the resist film 220 has been removed by edge rinse, the etching mask film 218 below the resist film 220 is exposed.

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

[0012] Fig. 15 is an enlarged cross-sectional view of the outer peripheral end of the reflective mask blank 200 on which the reference mark FM is formed. As shown in Fig. 15, the reference mark FM is formed in an area outside an area PA in which a pattern is formed in the absorber film 216. When forming the reference mark FM, first, a resist pattern 220a for forming the reference mark FM is formed in the resist film 220 by electron beam drawing, and the etching mask film 218 and the absorber film 216 are etched by dry etching using this resist pattern 220a as a mask, thereby forming the reference mark FM.

[0013] As described above, in the region R where the resist film 220 has been removed by edge rinsing, the etching mask film 218 below the resist film 220 is exposed. Therefore, the etching mask film 218 and the absorber film 216 in the region R where the resist film 220 has been removed are removed by dry etching when forming the fiducial mark FM, and the protective film 214 below the absorber film 216 is exposed. At this time, the exposed protective film 214 is damaged by etching, and as shown in FIG. 16, an isolated island-shaped protective film 214a may be formed. This isolated island-shaped protective film 214a is a portion that is separated from the surroundings and is not connected to the protective film 214b on the center side of the substrate 210.

[0014] When an isolated island-shaped protective film 214a is formed, the isolated island-shaped protective film 214a becomes charged during electron beam drawing to form a pattern on the absorber film 216. When the isolated island-shaped protective film 214a becomes charged, the isolated island-shaped protective film 214a may suddenly release the charge, causing electrostatic breakdown, since the isolated island-shaped protective film 214a does not have a means (e.g., a conductive pin) for dissipating the charge. When the reflective mask blank 200 is damaged by electrostatic breakdown, the reflective mask blank 200 becomes unusable as a product, which has been a problem.

[0015] The present invention has been made to solve the above-mentioned problems, 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 are capable of preventing electrostatic breakdown from occurring at the peripheral edge of a substrate. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention has the following configuration.

[0017] (Configuration 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 absorber film on the protective film, The absorber film has a buffer layer and an absorption layer provided on the buffer layer. When the distance from the center of the substrate to the outer peripheral end of the protective film is Lcap and the distance from the center of the substrate to the outer peripheral end of the buffer layer is Lbuf, Lcap ≦ Lbuf. A reflective mask blank, characterized in that at least one location where the total film thickness of the protective film and the buffer layer is 4.5 nm or more exists within a range of 0.5 mm or less from the side surface of the substrate toward the center of the substrate.

[0018] (Configuration 2) The reflective mask blank according to Configuration 1, wherein the buffer layer contains at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y).

[0019] (Configuration 3) The reflective mask blank according to Configuration 1 or 2, wherein 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.

[0020] (Configuration 4) The reflective mask blank according to any one of Configurations 1 to 3, wherein when the distance from the center of the substrate to the outer peripheral end of the absorption layer is Labs, Lcap ≦ Labs.

[0021] (Configuration 5) The reflective mask blank according to any one of Configurations 1 to 4, wherein the protective film contains ruthenium (Ru).

[0022] (Configuration 6) A resist film is provided on the absorber film. When the distance from the center of the substrate to the outer peripheral end of the resist film is Lres, the reflective mask blank according to any one of Claims 1 to 5, characterized in that Lres < Lcap ≦ Lbuf.

[0023] (Configuration 7) 7. A reflective mask having an absorber pattern formed by patterning the absorber layer in the reflective mask blank according to any one of configurations 1 to 6.

[0024] (Configuration 8) The reflective mask according to configuration 7, wherein a reference mark is formed in the absorbing layer of the absorber film.

[0025] (Configuration 9) A method for producing a reflective mask, comprising patterning the absorbing layer of the reflective mask blank according to any one of Configurations 1 to 6 to form an absorber pattern.

[0026] (Configuration 10) A method for manufacturing a semiconductor device, comprising the steps of setting the reflective mask according to Structure 7 or 8 in an exposure apparatus having an exposure light source that emits EUV light, and transferring a transfer pattern to a resist film formed on a transfer substrate. Effect of the Invention

[0027] According to the present invention, it is possible to provide a reflective mask blank, a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a semiconductor device, which are capable of preventing electrostatic breakdown from occurring at the peripheral edge of a substrate. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of a reflective mask blank of the present embodiment, in which the outer peripheral edge portion of a substrate is enlarged. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another example of a reflective mask blank of the present embodiment, in which the outer peripheral end portion of the substrate is enlarged. [Diagram 3] FIG. 2 is an enlarged cross-sectional view of the outer circumferential end portion of a reflective mask blank on which a reference mark is formed. [Figure 4] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Diagram 5]3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 6] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 7] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 8] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 9] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 10] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 11] 3 is a schematic diagram for explaining the size relationship among a protective film, a buffer layer, an absorption layer, an etching mask film, and a resist film. FIG. [Figure 12] 1A to 1C are schematic diagrams showing an example of a method for manufacturing a reflective mask. [Figure 13] FIG. 1 is a diagram showing a schematic configuration of an EUV exposure apparatus. [Figure 14] FIG. 1 is an enlarged cross-sectional view of an outer peripheral end portion of a conventional reflective mask blank. [Figure 15] FIG. 11 is an enlarged cross-sectional view of the outer circumferential end portion of a conventional reflective mask blank on which a reference mark FM is formed. [Figure 16] FIG. 1 is an enlarged cross-sectional view of an outer peripheral end portion of a conventional reflective mask blank on which an island-shaped protective film is formed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are merely for the purpose of specifically explaining the present invention, and are not intended to limit the scope of the present invention.

[0030] Fig. 1 is a schematic cross-sectional view showing an example of a reflective mask blank 100 of this embodiment, and is an enlarged view of the outer peripheral end 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 absorber film 16 formed on the protective film 14. The absorber film 16 has a two-layer structure, and includes a buffer layer 18 formed so as to be in contact with the protective film 14, and an absorber layer 20 formed on the buffer layer 18. A back surface conductive film 22 for electrostatic chuck may be formed on the back surface of the substrate 10 (the surface opposite to the side on which the multilayer reflective film 12 is formed).

[0031] In this specification, "on" a substrate or a film includes not only the case of contacting the upper surface of the substrate or film, but also the case of not contacting the upper surface of the substrate or film. In other words, "on" a substrate or a film includes the case where a new film is formed above the substrate or film, or the case where another film is interposed between the substrate or film. Furthermore, "on" does not necessarily mean the upper side in the vertical direction. "On" merely indicates the relative positional relationship of the substrate, film, etc.

[0032] <Substrate> To prevent distortion of the transferred pattern due to heat during exposure to EUV light, the substrate 10 is preferably one having a low thermal expansion coefficient within the range of 0±5 ppb / ° C. Materials having a low thermal expansion coefficient within this range include, for example, SiO2-TiO2 glass, multi-component glass ceramics, etc.

[0033] The main surface of the substrate 10 on which a transfer pattern (an absorber pattern described later) is formed is preferably processed to increase its flatness. By increasing the flatness of the main surface of the substrate 10, the positional accuracy and transfer accuracy of the pattern can be increased. For example, in the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less, in a 132 mm×132 mm area of ​​the main surface of the substrate 10 on which a transfer pattern is formed. In addition, the main surface (back surface) on the opposite side to the side on which the transfer pattern is formed is a surface fixed by an electrostatic chuck to an exposure device, and in a 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 this specification, flatness is a value that represents the surface warpage (deformation amount) indicated by TIR (Total Indicated Reading), and is the absolute value of the difference in height between the highest point on the substrate surface above the focal plane, which is determined by the least squares method with the substrate surface as the reference plane, and the lowest point on the substrate surface below the focal plane.

[0034] In the case of EUV exposure, the surface roughness of the main surface of the substrate 10 on which the transfer pattern is formed is preferably 0.1 nm or less in terms of root mean square roughness (Rq). The surface roughness can be measured by an atomic force microscope.

[0035] The substrate 10 preferably has high rigidity to prevent deformation due to film stress of the films (such as the multilayer reflective film 12) formed thereon, and in particular, preferably has a high Young's modulus of 65 GPa or more.

[0036] <Multilayer reflective film> The multilayer reflective film 12 has a structure in which a plurality of layers mainly composed of elements with different refractive indexes are laminated periodically. In general, the multilayer reflective film 12 is made of a multilayer film in which thin films (high refractive index layers) of light elements or compounds thereof, which are high refractive index materials, and thin films (low refractive index layers) of heavy elements or compounds thereof, which are low refractive index materials, are alternately laminated for about 40 to 60 periods. To form the multilayer reflective film 12, a high refractive index layer and a low refractive index layer may be laminated in this order multiple times from the substrate 10 side. In this case, one laminate structure of (high refractive index layer / low refractive index layer) constitutes one period.

[0037] In addition, the top layer of the multilayer reflective film 12, that is, the surface layer of the multilayer reflective film 12 opposite to the substrate 10, is preferably a high refractive index layer. When a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 10 side, the top layer is a low refractive index layer. However, when the low refractive index layer is the surface of the multilayer reflective film 12, the reflectance of the surface of the multilayer reflective film is reduced by the low refractive index layer being easily oxidized, so it is preferable to form a high refractive index layer on the low refractive index layer. On the other hand, when a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 10 side, the top layer is a high refractive index layer. In that case, the topmost high refractive index layer is the surface of the multilayer reflective film 12.

[0038] 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 contain simple Si or a Si compound. The Si compound may contain 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 reflectance for EUV light can be obtained.

[0039] The low refractive index layer included in the multilayer reflective film 12 is a layer made of a material containing 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. The low refractive index layer is more preferably a layer made of a material containing Mo.

[0040] For example, as the multilayer reflective film 12 for EUV light with a wavelength of 13 to 14 nm, a Mo / Si multilayer film in which Mo films and Si films are alternately laminated in about 40 to 60 periods can be preferably used.

[0041] The reflectance of such a single multilayer reflective film 12 is, for example, 65% or more. The upper limit of the reflectance of the multilayer reflective film 12 is, for example, 73%. The thickness and period of the layers included in the multilayer reflective film 12 can be selected so as to satisfy Bragg's law.

[0042] The multilayer reflective film 12 can be formed by a known method, for example, an ion beam sputtering method.

[0043] For example, when the multilayer reflective film 12 is a Mo / Si multilayer film, a Mo film having a thickness of about 3 nm is formed on the substrate 10 by ion beam sputtering using a Mo target. Next, a Si film having a thickness of about 4 nm is formed using a Si target. By repeating such an operation, the multilayer reflective film 12 can be formed in which 40 to 60 periods of Mo / Si films are stacked. At this time, the surface layer of the multilayer reflective film 12 on the side opposite to the substrate 10 is a layer containing Si (Si film). The thickness of one period of the Mo / Si film is 7 nm.

[0044] <Protective film> The reflective mask blank 100 of this embodiment has a protective film 14 formed on the multilayer reflective film 12. The protective film 14 has a function of protecting the multilayer reflective film 12 from dry etching and cleaning in the manufacturing process of the reflective mask 110, which will be described later. The protective film 14 also has a function of protecting the multilayer reflective film 12 when correcting a black defect 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 multilayer reflective film 12 has good reflectance characteristics for EUV light.

[0045] The protective film 14 can be formed by using a known method. Examples of the method 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.

[0046] The protective film 14 can be formed of a material having a different etching selectivity from the buffer layer 18. Examples of the material of the protective film 14 include Ru, Ru-(Nb,Rh,Zr,Y,B,Ti,La,Mo), Si-(Ru,Rh,Cr,B), Si,Zr,Nb,La,B, and the like. Among these, when a material containing ruthenium (Ru) is used, the reflectance characteristics of the multilayer reflective film 12 become better. Specifically, Ru and Ru-(Nb,Rh,Zr,Y,B,Ti,La,Mo) are preferable. Such a protective film 14 is particularly effective when the buffer layer 18 is patterned by dry etching using a chlorine-based gas or a fluorine-based gas.

[0047] <Absorber membrane> As described above, the absorber film 16 includes the buffer layer 18 formed in contact with the protective film 14 and the absorber layer 20 formed on the buffer layer 18 . The basic function of the absorber film 16 (including the absorber layer 20 and the buffer layer 18) is to absorb EUV light. The absorber film 16 may be an absorber film 16 for absorbing EUV light, or an absorber film 16 having a phase shift function that also takes into account the phase difference of EUV light. The absorber film 16 having a phase shift function absorbs EUV light and reflects a part of it to shift the phase. That is, in a reflective mask in which the absorber film 16 having a phase shift function is patterned, the absorber film 16 absorbs EUV light to reduce the light, and reflects a part of the light at a level that does not adversely affect pattern transfer in the portion where the absorber film 16 is formed. In addition, in the region (field portion) in which the absorber film 16 is not formed, the EUV light is reflected by the multilayer reflective film 12 via the protective film 14. Therefore, a desired phase difference is generated between the reflected light from the absorber film 16 having a phase shift function and the reflected light from the field portion. The absorber film 16 having a phase shift function is preferably formed so that the phase difference between the reflected light from the absorber film 16 and the reflected light from the multilayer reflective film 12 is 170 degrees to 190 degrees. Light beams with an inverted phase difference of about 180 degrees interfere with each other at the pattern edge, improving the image contrast of the projected optical image. With the improvement in image contrast, the resolution increases, and various exposure tolerances such as exposure dose tolerance and focus tolerance can be increased.

[0048] The absorbing layer 20 in the absorber film 16 is a film that mainly has the function of the absorber film 16 described above, and may be a single layer film or a multilayer film consisting of multiple films. In the case of a single layer film, the number of steps during mask blank manufacturing can be reduced, improving production efficiency. In the case of a multilayer film, the optical constant and film thickness of the upper absorbing layer can be appropriately set so that it becomes an anti-reflection film during mask pattern defect inspection using light. This improves the inspection sensitivity during mask pattern defect inspection using light. In addition, if a film to which oxygen (O) and nitrogen (N) that improve oxidation resistance are added is used as the upper absorbing layer, the stability over time is improved. In this way, by making the absorbing layer 20 a multilayer film, it is possible to add various functions to the absorbing layer 20. When the absorbing layer 20 has a phase shift function, by making it a multilayer film, the range of adjustment on the optical surface can be increased, making it easier to obtain a desired reflectance.

[0049] The material of the absorption layer 20 is not particularly limited as long as it has the function of absorbing EUV light, can be processed by etching or the like (preferably can be etched by dry etching with a chlorine (Cl)-based gas and / or a fluorine (F)-based gas), and has a high etching selectivity with respect to the buffer layer 18. As a material 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, can be preferably used.

[0050] The absorbing layer 20 can be formed by magnetron sputtering such as DC sputtering and RF sputtering. For example, the absorbing layer 20 made of a tantalum compound or the like can be formed by reactive sputtering using a target containing tantalum and boron and argon gas to which oxygen or nitrogen is added.

[0051] The tantalum compound for forming the absorbing layer 20 includes an alloy of Ta and the above-mentioned metal. When the absorbing layer 20 is an alloy of Ta, the crystal state of the absorbing layer 20 is preferably an amorphous or microcrystalline structure in terms of smoothness and flatness. If the surface of the absorbing layer 20 is not smooth or flat, the edge roughness of the absorber pattern described below may increase, and the dimensional accuracy of the pattern may deteriorate. The surface roughness of the absorbing layer 20 is preferably 0.5 nm or less, more preferably 0.4 nm or less, and even more preferably 0.3 nm or less, in terms of root mean square roughness (Rms).

[0052] Examples of tantalum compounds for forming the 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 further 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.

[0053] Ta is a material that has a large absorption coefficient of EUV light and can be easily dry etched with a chlorine-based gas or a fluorine-based gas. Therefore, it can be said that Ta is a material for the absorber layer 20 that is excellent in processability. Furthermore, by adding B, Si, and / or Ge, etc. to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber layer 20 can be improved. Furthermore, by adding N and / or O to Ta, the resistance of the absorber layer 20 to oxidation is improved, and therefore the stability over time can be improved.

[0054] <Etching mask film> Fig. 2 is a schematic cross-sectional view showing another example of the reflective mask blank 100 of this embodiment, and is an enlarged view of the outer circumferential edge of the substrate 10. As shown in Fig. 2, the reflective mask blank 100 can further have another thin film, such as a resist film 26, on the absorber film 16. In addition, the reflective mask blank 100 may further have an etching mask film 24 between the absorber layer 20 and the resist film 26. The etching mask film 24 is preferably made of a material having a high etching selectivity of the absorbing layer 20 to the etching mask film 24. The etching selectivity of the absorbing layer 20 to the etching mask film 24 is preferably 1.5 or more, and more preferably 3 or more.

[0055] The reflective mask blank 100 of this embodiment preferably has an etching mask film 24 containing chromium (Cr) on the absorbing layer 20. When the absorbing layer 20 is etched with a fluorine-based gas, it is preferable to use chromium or a chromium compound as the material of 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. The etching mask film 24 more preferably contains 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.

[0056] When the absorption layer 20 is etched with a chlorine-based gas that does not substantially contain oxygen, or when the absorption layer 20 is etched with a mixed gas of a chlorine-based gas and an oxygen gas, it is preferable to use silicon or a silicon compound as the material of 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, as well as metal silicon (metal silicide) and metal silicon compounds (metal silicide compounds) containing metal in silicon and silicon compounds. Examples of metal silicon compounds include materials containing 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 of the etching mask film. Specific examples of such materials include SiN and SiO. When the absorption layer 20 is etched with a chlorine-based gas that does not substantially contain oxygen, or when the absorption layer 20 is etched with a mixed gas of a chlorine-based gas and an oxygen gas, an etching mask film 24 containing tantalum (Ta) can be used. Examples of materials containing Ta include materials containing Ta and one or more elements selected from O, N, C, B, and H. Among these, it is particularly preferable to use a material containing Ta and O as the material of the etching mask film. Specific examples of such materials include TaO, TaON, TaBO, and TaBON. Furthermore, as the material of the etching mask film, 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.

[0057] The thickness of the etching mask film 24 is preferably 3 nm or more in order to accurately form a pattern in the absorption layer 20. Moreover, 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.

[0058] <Backside conductive film> A back conductive film 22 for electrostatic chuck may be formed on the back surface of the substrate 10 (the surface opposite to the surface on which the multilayer reflective film 12 is formed). The sheet resistance required for the back conductive film 22 for electrostatic chuck is usually 100 Ω / □ (Ω / square) or less. The back conductive film 22 can be formed by magnetron sputtering or ion beam sputtering using a target of a metal such as chromium or tantalum, or an alloy thereof. The material of the back conductive film 22 is preferably a material containing chromium (Cr) or tantalum (Ta). For example, the material of the back conductive film 22 is preferably a Cr compound containing at least one element selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of Cr compounds include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. The material of the back surface 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.

[0059] The thickness of the back surface conductive film 22 is not particularly limited as long as it functions as a film for an electrostatic chuck, and is, for example, 10 nm to 200 nm.

[0060] The above-mentioned buffer layer 18 will now be described in detail. 2, the resist film 26 is formed on the entire surface of the reflective mask blank 100, but in order to prevent the resist film 26 from peeling off and generating dust at the peripheral portion of the substrate 10, the resist film 26 is usually removed from the peripheral portion of the substrate where the mask pattern is not formed (edge ​​rinsing). In the region R where the resist film 26 has been removed by edge rinsing, the etching mask film 24 underneath the resist film 26 is exposed. In the case of a reflective mask blank 100 without the etching mask film 24, the absorbing layer 20 is exposed.

[0061] In a reflective mask that uses EUV light as exposure light, it is important to accurately manage the positions 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 may become serious phase defects in the transfer pattern. For this reason, a mark serving as a reference for managing the positions of defects on the multilayer reflective film 12 may be formed in the reflective mask blank 100. This reference mark may also be called a fiducial mark.

[0062] Fig. 3 is an enlarged cross-sectional view of the outer peripheral end of the reflective mask blank 100 on which the fiducial mark FM is formed. As shown in Fig. 3, the fiducial mark FM is formed in an area outside an area PA in which a pattern is formed in the absorption layer 20. When forming the fiducial mark FM, first, a resist pattern 26a for forming the fiducial mark FM is formed in the resist film 26 by electron beam drawing, and then the etching mask film 24 and the absorption layer 20 are etched by dry etching using this resist pattern 26a as a mask, to form the fiducial mark FM.

[0063] As described above, in the region R from which the resist film 26 has been removed by the edge rinse, the etching mask film 24 (or the absorbing layer 20) underlying the resist film 26 is exposed. For this reason, the etching mask film 24 and the absorbing layer 20 in the region R from which the resist film 26 has been removed are removed by dry etching performed when forming the reference mark FM in the absorbing layer 20.

[0064] In the reflective mask blank 100 of this embodiment, the absorber film 16 includes a buffer layer 18 formed so as to be in contact with the protective film 14, and an absorbing layer 20 formed on the buffer layer 18. The buffer layer 18 is a layer having etching resistance with respect to the absorbing layer 20, and is a layer for preventing the formation of isolated islands of the protective film. Therefore, even if the etching mask film 24 and the absorption layer 20 are removed by dry etching when forming the reference mark FM in the region R from which the resist film 26 has been removed by edge rinsing, the buffer layer 18 remains on the protective film 14, so that it is possible to prevent the protective film 14 from being damaged by the etching.

[0065] The buffer layer 18 can be formed by a known film formation method, for example, a magnetron sputtering method such as a DC sputtering method or an RF sputtering method.

[0066] The material of the buffer layer 18 is not particularly limited, but is preferably a material that is resistant to an etchant used in dry etching when forming the reference mark FM in the absorption layer 20. The buffer layer 18 can be formed of, for example, the same material as the above-mentioned etching mask film 24. The buffer layer 18 preferably contains 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, the buffer layer 18 is preferably formed of the same material as the etching mask film 24.

[0067] According to the reflective mask blank 100 of the present embodiment, the buffer layer 18 remains on the protective film 14, so it is possible to prevent the protective film 14 from being damaged by dry etching when forming the fiducial marks FM. This makes it possible to prevent the occurrence of "isolated islands of protective film" that conventionally occurred when forming the fiducial marks FM, and makes it possible to prevent electrostatic breakdown caused by the isolated islands of protective film becoming charged.

[0068] In the reflective mask blank 100 of this embodiment, when the distance from the center of the substrate 10 to the outer circumferential edge of the protective film 14 is Lcap and the distance from the center of the substrate 10 to the outer circumferential edge of the buffer layer 18 is Lbuf, Lcap≦Lbuf holds. When the protective film 14 and the buffer layer 18 satisfy such conditions, the buffer layer 18 remains on the protective film 14 in the region R from which the resist film 26 has been removed by edge rinsing. Because the buffer layer 18 remains on the protective film 14, it is possible to prevent the generation of isolated islands of the protective film 14 in the region R from which the resist film 26 has been removed by edge rinsing.

[0069] In the reflective mask blank 100 of this embodiment, within a range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10, there is at least one location where the total thickness T of the protective film 14 and the buffer layer 18 is 4.5 nm or more. When the protective film 14 and the buffer layer 18 satisfy such conditions, in a region R from which the resist film 26 has been removed by edge rinsing (region R is usually a region with a width of about 1 to 1.5 mm from the side surface 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 where the total 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 from which the resist film 26 has been removed by edge rinsing, it is possible to ensure that the total thickness T of the protective film 14 and the buffer layer 18 is sufficiently large, and it is possible to more reliably prevent the generation of isolated island-like protective films 14. In the range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10, the total thickness T of the protective film 14 and the buffer layer 18 is preferably 5.0 nm or more, more preferably 5.5 nm or more. Moreover, the total thickness T is preferably 35 nm or less, more preferably 30 nm or less.

[0070] In the reflective mask blank 100 of this 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. Moreover, 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 such conditions, it is possible to ensure that the total film thickness T of the protective film 14 and the buffer layer 18 is sufficiently large even in the region R from which the resist film 26 has been removed by edge rinsing, and therefore it is possible to more reliably prevent the generation of isolated islands of the protective film 14.

[0071] In this specification, the center of the substrate 10 means the position of the center of gravity of the rectangular (e.g., square) substrate 10 (the position of the point on the main surface 10a of the substrate 10 corresponding to the position of the center of gravity). The side surface 10b of the substrate 10 is a surface that is approximately perpendicular to the two main surfaces of the substrate 10, and is sometimes called a "T-surface." The outer peripheral edge of the film or layer means the end of the film or layer that is located farthest from the center of the substrate 10. In addition, the deposition area (distance from the center of the substrate to the outer peripheral 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 peripheral edge of the substrate 10 can be appropriately adjusted by the opening dimensions of the PVD shield, the tapered shape of the opening, the distance between the shield and the substrate, etc.

[0072] 4 to 11 are schematic diagrams for explaining the size relationships among the protective film 14, the buffer layer 18, the absorption layer 20, the etching mask film 24, and the resist film 26 in the reflective mask blank 100 of this embodiment. In order to simplify the drawings, the thickness of each layer is approximately constant toward its outer circumferential edge in Figs. 4 to 11.

[0073] Here, the distance from the center of the substrate 10 to the outer circumferential edge of each layer is defined as follows. Lcap: distance from the center of the substrate 10 to the outer circumferential edge of the protective film 14 Lbuf: distance from the center of the substrate 10 to the outer circumferential edge of the buffer layer 18 Labs: Distance from the center of the substrate 10 to the outer edge of the absorption layer 20 Letc: distance from the center of the substrate 10 to the outer circumferential edge of the etching mask film 24 Lres: distance from the center of the substrate 10 to the outer periphery of the resist film 26

[0074] In Figure 4, Lres <Lcap<Lbuf<Labs<Letcとなっている。 During dry etching for forming the fiducial 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, resulting in the removal of the region surrounded by the dotted line in Fig. 4. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and thus preventing the generation of "isolated islands of the protective film."

[0075] In Figure 5, Lres <Lcap<Labs<Lbuf<Letcとなっている。 During dry etching for forming the fiducial 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 (that is, the buffer layer 18 and the etching mask film 24 are etched at the same time). After that, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, so that the region surrounded by the dotted line in FIG. 5 is removed. Even in this case, the entire surface of the protective film 14 is kept covered by the buffer layer 18, so that it is possible to prevent the protective film 14 from being damaged by etching and thus generating an "isolated island-like protective film."

[0076] In Figure 6, Lres <Lcap<Lbuf<Letc<Labsとなっている。 During dry etching for forming the fiducial 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, resulting in the removal of the region surrounded by the dotted line in Fig. 6. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and thus preventing the generation of "isolated islands of the protective film."

[0077] In Figure 7, Lres <Lcap<Labs<Letc<Lbufとなっている。 During dry etching for forming the fiducial 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 (that is, the buffer layer 18 and the etching mask film 24 are etched at the same time). After that, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, so that the region surrounded by the dotted line in FIG. 7 is removed. Even in this case, the entire surface of the protective film 14 is kept covered by the buffer layer 18, so that it is possible to prevent the protective film 14 from being damaged by etching and thus generating an "isolated island-like protective film."

[0078] In Figure 8, Lres <Lcap<Letc<Lbuf<Labsとなっている。 During dry etching for forming the fiducial 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, resulting in the removal of the region surrounded by the dotted line in Fig. 8. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and thus preventing the generation of "isolated islands of the protective film."

[0079] In Figure 9, Lres <Lcap<Letc<Labs<Lbufとなっている。 During dry etching for forming the fiducial 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 (that is, the buffer layer 18 and the etching mask film 24 are etched at the same time). After that, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, so that the region surrounded by the dotted line in FIG. 9 is removed. Even in this case, the entire surface of the protective film 14 is kept covered by the buffer layer 18, so that it is possible to prevent the protective film 14 from being damaged by etching and thus generating an "isolated island-like protective film."

[0080] In Figure 10, Lres <Letc<Lcap<Lbuf<Labsとなっている。 During dry etching for forming the fiducial 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, resulting in the removal of the region surrounded by the dotted line in Fig. 10. Even in this case, the entire surface of the protective film 14 remains covered by the buffer layer 18, so it is possible to prevent the protective film 14 from being damaged by etching and thus preventing the generation of "isolated islands of the protective film."

[0081] In Figure 11, Lres <Letc<Lcap<Labs<Lbufとなっている。 During dry etching for forming the fiducial 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 (that is, the buffer layer 18 and the etching mask film 24 are etched at the same time). After that, the absorption layer 20 that is not covered by the resist film 26 is etched by dry etching, so that the region surrounded by the dotted line in FIG. 11 is removed. Even in this case, the entire surface of the protective film 14 is kept covered by the buffer layer 18, so that it is possible to prevent the protective film 14 from being damaged by etching and thus generating an "isolated island-like protective film."

[0082] In the reflective mask blank 100 of this embodiment, it is preferable that Lcap≦Labs. When Lcap≦Labs, even when the etching mask film 24 and the buffer layer 18 are etched with the same etchant, the entire surface of the protective film 14 is kept covered with the buffer layer 18, so that it is possible to more reliably prevent the protective film 14 from being damaged by etching and generating "isolated islands of the protective film."

[0083] In the reflective mask blank 100 of the present embodiment, it is preferable that Lres < Lcap ≤ Lbuf. When the resist film 26 at the peripheral edge of the substrate 10 is removed by the edge rinse, Lres < Lcap often occurs. Even in this case, during the dry etching for forming the reference mark FM, since the entire surface of the protective film 14 is maintained covered with the buffer layer 18, it is possible to more reliably prevent the occurrence of "isolated protective films" due to the protective film 14 being damaged by etching.

[0084] <Method for manufacturing a reflective mask> Using the reflective mask blank 100 of the present embodiment, the reflective mask 110 of the present embodiment can be manufactured. Hereinafter, an example of a method for manufacturing a reflective mask will be described.

[0085] FIG. 12 is a schematic diagram showing an example of a method for manufacturing a reflective mask 110. As shown in FIG. 12, first, a reflective mask blank 100 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 absorber film 16 (buffer layer 18 and absorber layer 20) formed on the protective film 14, and a backside conductive film 22 formed on the back surface of the substrate 10 is prepared (FIG. 12(a)). Next, a resist film 26 is formed on the absorber film 16 (FIG. 12(b)). In order to suppress dust generation due to peeling of the resist film 26 at the peripheral edge 27 of the substrate, the resist film 26 at the peripheral edge 27 of the substrate is removed with a solvent in which the resist film 26 dissolves (edge rinse) (FIG. 12(c)). A pattern is drawn on the resist film 26 by an electron beam lithography apparatus, and through a development and rinse process, a resist pattern 26a is formed (FIG. 12(d)).

[0086] Using the resist pattern 26a as a mask, the absorber layer 20 of the absorber film 16 is dry-etched. As a result, the portion of the absorber layer 20 not covered by the resist pattern 26a is etched, and a pattern is formed in the absorber layer 20 (FIG. 12(e)).

[0087] As the etching gas for the absorption layer 20, for example, a fluorine-based gas and / or a chlorine-based gas can be used. As the fluorine-based gas, CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, SF6, F2, etc. can be used. As the chlorine-based gas, Cl2, SiCl4, CHCl3, CCl4, BCl3, etc. can be used. In addition, a mixed gas containing a fluorine-based gas and / or a chlorine-based gas and O2 at a predetermined ratio can be used. These etching gases can further contain an inert gas such as He and / or Ar as necessary.

[0088] After the pattern is formed in the absorber layer 20, the buffer layer 18 is patterned by dry etching to form an absorber pattern 16a. The resist pattern 26a is removed by a resist remover. After removing the resist pattern 26a, a wet cleaning process is performed using an acidic or alkaline aqueous solution to obtain the reflective mask 110 of this embodiment (FIG. 12(f)).

[0089] In addition, when a reflective mask blank 100 in which an etching mask film 24 is formed on the absorber film 16 is used, an additional process is performed in which a pattern (etching mask pattern) is formed in the etching mask film 24 using the resist pattern 26a as a mask, and then a pattern is formed in the absorption layer 20 using the etching mask pattern as a mask.

[0090] The reflective mask 110 thus obtained has a structure in which a multilayer reflective film 12, a protective film 14, and an absorber pattern 16a are laminated on a substrate 10.

[0091] An area 30 where the multilayer reflective film 12 (including the protective film 14) is exposed has a function of reflecting EUV light. An area 32 where the multilayer reflective film 12 (including the protective film 14) is covered with the absorber pattern 16a has a function of absorbing EUV light.

[0092] <Method of Manufacturing Semiconductor Device> A transfer pattern can be formed on a semiconductor substrate by lithography using the reflective mask 110 of this embodiment. This transfer pattern has a shape transferred from the pattern of the reflective mask 110. By forming a transfer pattern on a semiconductor substrate using the reflective mask 110, a semiconductor device can be manufactured.

[0093] 13 shows a schematic configuration of an EUV exposure tool 50 which is a tool for transferring a transfer pattern onto a resist film formed on a semiconductor substrate 60. In the EUV exposure tool 50, an EUV light generation unit 51, an irradiation optical system 56, a reticle stage 58, a projection optical system 57, and a wafer stage 59 are precisely arranged along the optical path axis of the EUV light. The container of the EUV exposure tool 50 is filled with hydrogen gas.

[0094] 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 the high-power carbon dioxide laser from the laser light source 52 is irradiated onto the tin droplets released from the tin droplet generation unit 53, the tin in the droplet state is converted into plasma and EUV light is generated. The generated EUV light is collected by the collector 55 and passes through the irradiation optical system 56 to be incident on a reflective mask 110 set on a reticle stage 58. The EUV light generation unit 51 generates EUV light with a wavelength of, for example, 13.53 nm.

[0095] The EUV light reflected by the reflective mask 110 is reduced to a pattern image light, usually about 1 / 4, by the projection optical system 57 and projected onto the semiconductor substrate 60 (transferred substrate). As a result, a given circuit pattern is transferred onto the resist film on the semiconductor substrate 60.

[0096] By developing the exposed resist film, a resist pattern can be formed on the 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. Through these steps and other necessary steps, a semiconductor device can be manufactured. EXAMPLES

[0097] Examples 1 to 3 and Comparative Example 1 will be described below.

[0098] First, a substrate 10 having a polished main surface and a size of 6025 (approximately 152 mm × 152 mm × 6.35 mm) was prepared. This substrate 10 was made of low thermal expansion glass (SiO2-TiO2-based glass). The main surface of the substrate 10 was polished by a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process.

[0099] 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 a periodic multilayer reflective film 12 made of Mo and Si in order to make the multilayer reflective film 12 suitable for EUV light with a wavelength of 13.5 nm. The multilayer reflective film 12 was formed by alternately laminating Mo films and Si films on the substrate 10 by an ion beam sputtering method using a Mo target and a Si target and krypton (Kr) as a process gas. First, a Si film was formed to a thickness of 4.2 nm, and then a Mo film was formed to a thickness of 2.8 nm. This constitutes one period, and 40 periods were similarly laminated, and finally a Si film was formed to a thickness of 4.0 nm.

[0100] 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 thickness of the protective film 14 (thickness at the center of the substrate 10) was 3.5 nm.

[0101] 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 layers 18 of Example 1, Example 3, and Comparative Example 1 were 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.

[0102] 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 layers 20 of Example 1, Example 3, and Comparative Example 1 were 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.

[0103] In Example 3, an etching mask film 24 made of the same CrON as the buffer layer 18 was further formed on the absorption layer 20. The film thickness of the etching mask film 24 was 6 nm.

[0104] In Example 1 and Example 2, the films of each layer were formed so that Lml < Lcap ≤ Lbuf ≤ Labs. In Example 3, the films of each layer were formed so that Lml < Lcap ≤ Lbuf < Labs = Letc. In Comparative Example 1, the films of each layer were formed so that Lml < Lbuf < Lcap. The meanings of the symbols are the same as those defined above. Lml means the distance from the center of the substrate 10 to the outer peripheral end of the multilayer reflective film 12. 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.

[0105] In Examples 1 to 3, the protective film 14 and the buffer layer 18 were deposited so that there was at least one location where the total thickness of the protective film 14 and the buffer layer 18 was 4.5 nm or more within a range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10, as shown in Table 1. In Comparative Example 1, the protective film 14 and the buffer layer 18 were deposited so that there was no location where the total thickness of the protective film 14 and the buffer layer 18 was 4.5 nm or more within a range of 0.5 mm from the side surface of the substrate 10 toward the center of the substrate 10. The thickness of each layer at the outer periphery was adjusted by the opening size of the PVD shield by magnetron sputtering.

[0106] [Table 1]

[0107] Next, a reflective mask 110 was produced using the reflective mask blank 100 prepared above. Specifically, first, a resist film 26 was formed on the absorption layer 20 or the etching mask film 24. After the resist film 26 was formed, the resist film 26 on the periphery of the substrate was removed with a resist remover (edge ​​rinse). After the edge rinse was performed, a pattern was drawn on the resist film 26 with an electron beam lithography device to form a resist pattern 26a. The absorption layer 20 was dry-etched using the resist pattern 26a as a mask to form a fiducial mark FM. Note that 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. In Example 3, the etching mask film 24 was dry-etched using a mixed gas of Cl2 gas and O2 gas with the resist pattern 26a as a mask to form an etching mask pattern, and then the absorption layer 20 was dry-etched using the etching mask pattern as a mask to form a fiducial mark FM.

[0108] After forming the reference mark FM on the absorbing layer 20, the resist pattern 26a on the absorbing layer 20 or the etching mask film 24 was removed by a resist remover. Then, a resist film for forming the absorber pattern 16a was formed on the absorbing layer 20 or the etching mask film 24. A pattern was drawn on the resist film by an electron beam lithography device to form a resist pattern, and then the absorbing layer 20 and the buffer layer 18 were dry-etched using the resist pattern as a mask to form the absorber pattern 16a. Note that the absorbing layer 20 of Examples 1 and 3 and Comparative Example 1 were dry-etched using Cl2 gas, and the buffer layer 18 was dry-etched using a mixed gas of Cl2 gas and O2 gas. Also, the absorbing 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. In addition, in Example 3, the etching mask film 24 was dry-etched using the resist pattern as a mask to form an etching mask pattern, 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 the absorber pattern 16a.

[0109] The top surface of the outermost periphery of the reflective mask 110 thus obtained was observed by TEM. As a result, in the reflective masks of Examples 1 to 3, no isolated island-shaped protective film was found in region R of the substrate periphery. Furthermore, no traces of electrostatic breakdown caused by isolated island-shaped protective film were found.

[0110] On the other hand, in the reflective mask of Comparative Example 1, isolated islands of the protective film were generated in the region R at the peripheral edge of the substrate. Also, traces of electrostatic breakdown caused by the isolated islands of the protective film were confirmed. [Explanation of symbols]

[0111] 10 Substrate 12 Multilayer reflective film 14 Protective film 16 Absorber membrane 18 Buffer layer 20 Absorption Layer 16a Absorber pattern 22 Back conductive film 24 Etching mask film 26a Resist pattern 26 Resist film 50 EUV exposure equipment 100 Reflective mask blank 110 Reflective mask

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 absorber film on the protective film, The absorber film has a buffer layer and an absorber layer provided on the buffer layer, where Lcap is the distance from the center of the substrate to the outer circumferential edge of the protective film, and Lbuf is the distance from the center of the substrate to the outer circumferential edge of the buffer layer, Lcap≦Lbuf; A reflective mask blank, characterized in that within a range of 0.5 mm from a side surface of the substrate toward the center of the substrate, there is at least one location where the total film thickness of the protective film and the buffer layer is 4.5 nm or more.

2. 2. The reflective mask blank according to claim 1, wherein the buffer layer contains at least one selected from tantalum (Ta), silicon (Si), chromium (Cr), iridium (Ir), platinum (Pt), palladium (Pd), zirconium (Zr), hafnium (Hf), and yttrium (Y).

3. 3. The reflective mask blank according to claim 1, wherein a total 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.

4. 4. The reflective mask blank according to claim 1, wherein, when the distance from the center of the substrate to the outer circumferential edge of the absorption layer is taken as Labs, Lcap≦Labs.

5. The reflective mask blank according to claim 1 , wherein the protective film contains ruthenium (Ru).

6. 6. The reflective mask blank according to claim 1, further comprising a resist film on the absorber film, wherein Lres is a distance from the center of the substrate to an outer peripheral edge of the resist film, and Lres<Lcap≦Lbuf.

7. 7. A reflective mask, comprising the absorbing layer in the reflective mask blank according to claim 1, which has an absorber pattern formed by patterning.

8. 8. The reflective mask according to claim 7, wherein a reference mark is formed in the absorbing layer of the absorber film.

9. A method for producing a reflective mask, comprising patterning the absorbing layer of the reflective mask blank according to claim 1 to form an absorber pattern.

10. 9. A method for manufacturing a semiconductor device, comprising the steps of: setting the reflective mask according to claim 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 transfer substrate.

Images