Substrate with reflective film, mask blank, reflective mask, and method for manufacturing semiconductor device

Abstract

To provide a substrate with a reflection film capable of suppressing occurrence of a blister in a reflection film formed on an end face of the substrate.SOLUTION: A substrate with a reflection film comprises: a substrate which has an end face which is connected to outer edges of two main surfaces and facing two main surfaces; and a reflection film which is formed on the main surfaces and at least a part on the end face. The reflection film on the main surface has a structure in which a low refractive index layer and a high refractive index layer are alternately laminated. The reflection film on the end face has a single layer structure including: an element whose content is largest in the low refractive index layer; and an element whose content is largest in the high refractive index layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a substrate with a reflective film, a mask blank, a reflective mask, and a method for manufacturing a semiconductor device, which are used in EUV lithography. [Background technology]

[0002] In general, in the manufacturing process of semiconductor devices, fine patterns are formed by photolithography. In addition, a number of transfer masks, called photomasks, are usually used to form these fine patterns. The transfer mask is generally a light-transmitting glass substrate on which a fine pattern made of a metal thin film or the like is provided, and the photolithography method is also used to manufacture the transfer mask.

[0003] In recent years, in the semiconductor industry, with the increasing integration of semiconductor devices, fine patterns exceeding the transfer limit of conventional photolithography using ultraviolet light are required. To enable the formation of such fine patterns, EUV lithography, an exposure technology using extreme ultraviolet (hereinafter referred to as "EUV") light, is considered promising. Here, EUV light refers to light in a wavelength band in the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm. A reflective mask has been proposed as a mask used in this EUV lithography. In such a reflective mask, a multilayer reflective film that reflects exposure light is formed on a substrate, and an absorber film that absorbs exposure light is formed in a pattern on the multilayer reflective film (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 116348 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the increasing demand for miniaturization in the lithography process, issues in the lithography process are becoming more prominent. One of these issues is the problem of contamination on the mirrors and masks of the exposure machine caused by EUV light irradiation in the EUV lithography process.

[0006] To solve this problem, techniques that suppress the adhesion of contamination during EUV exposure by creating a hydrogen atmosphere, such as hydrogen radicals, inside the exposure chamber, and cleaning methods that remove contamination using hydrogen plasma are beginning to be used.

[0007] However, when the above technology is applied, a new problem occurs in which hydrogen penetrates into the mask film, condenses, and causes the film to bulge, known as "blisters." When such a film bulges and bursts, it generates dust, causing contamination inside the exposure chamber. It has been found that hydrogen that penetrates into the film is likely to be captured at the interface with other films, depending on the film material, and blisters are likely to occur at the interface between two stacked films.

[0008] Meanwhile, a reflective mask used in EUV lithography has a reflective film formed on a substrate to reflect exposure light (EUV light). This reflective film is a multilayer film having a structure in which low-refractive index layers and high-refractive index layers are alternately laminated, and is formed on one main surface of the substrate by, for example, a sputtering method. In this case, the film is not only formed on one main surface of the substrate, but also deposited around the edge surface of the substrate. If the film deposited on the edge surface has a multilayer film structure similar to that of the film formed on the main surface, the risk of blisters occurring at the interface of the multilayer film increases.

[0009] Therefore, the object of the present invention is, first, to provide a substrate with a reflective film and a mask blank capable of suppressing the occurrence of blisters, particularly in a reflective film formed on an edge face of a substrate, and, second, to provide a reflective mask using this mask blank, capable of suppressing the occurrence of blisters, particularly in a reflective film formed on an edge face of a substrate. Another object of the present invention is to provide a method for manufacturing a semiconductor device using this reflective mask. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the inventors of the present invention have pursued extensive research, focusing in particular on the structure of a film that, when a reflective film is formed on a main surface of a substrate, also adheres to the edge faces of the substrate, and as a result have completed the present invention. That is, in order to solve the above problems, the present invention has the following configuration.

[0011] (Configuration 1) A substrate with a reflective film, comprising: a substrate having two opposing main surfaces and end faces connected to outer edges of the two main surfaces; and a reflective film formed on one of the main surfaces and on at least a part of the end faces, wherein the reflective film on the main surfaces has a structure in which low refractive index layers and high refractive index layers are alternately laminated, and the reflective film on the end faces has a single-layer structure containing an element that is most abundant in the low refractive index layer and an element that is most abundant in the high refractive index layer.

[0012] (Configuration 2) The substrate with a reflective film according to configuration 1, characterized in that the ratio of the content [atomic %] of the element most abundant in the low refractive index layer to the total content [atomic %] of the element most abundant in the low refractive index layer and the element most abundant in the high refractive index layer contained in the reflective film formed on the end face is less than 0.4. (Configuration 3) 3. The substrate with a reflective film according to configuration 1 or 2, wherein the thickness of the reflective film at the portion formed on the end face is thinner than the thickness of the reflective film at the portion formed on the main surface.

[0013] (Configuration 4) The substrate with a reflective film according to any one of structures 1 to 3, characterized in that the element contained most abundantly in the low refractive index layer is molybdenum, and the element contained most abundantly in the high refractive index layer is silicon. (Configuration 5) 5. The substrate with a reflective film according to any one of configurations 1 to 4, wherein the surface roughness (root mean square roughness) Rq of the reflective film formed on the end face is 1.5 nm or more.

[0014] (Configuration 6) 1. A mask blank comprising: a substrate having two opposing main surfaces and end faces connected to outer edges of the two main surfaces; a reflective film formed on one of the main surfaces and on at least a part of the end faces; and a thin film for pattern formation formed on the reflective film, wherein the reflective film on the main surfaces has a structure in which low-refractive index layers and high-refractive index layers are alternately laminated, and the reflective film on the end faces has a single-layer structure containing an element having the highest content in the low-refractive index layer and an element having the highest content in the high-refractive index layer.

[0015] (Configuration 7) The mask blank according to configuration 6, characterized in that the ratio of the content [atomic %] of the element most abundant in the low refractive index layer to the total content [atomic %] of the element most abundant in the low refractive index layer and the element most abundant in the high refractive index layer contained in the reflective film formed on the end face is less than 0.4. (Configuration 8) 8. The mask blank according to claim 6, wherein the thickness of the reflective film at the end faces is thinner than the thickness of the reflective film at the main surface.

[0016] (Configuration 9) 9. The mask blank according to any one of structures 6 to 8, wherein the element contained most abundantly in the low refractive index layer is molybdenum, and the element contained most abundantly in the high refractive index layer is silicon. (Configuration 10) 10. The mask blank according to any one of configurations 6 to 9, wherein the surface roughness (root-mean-square roughness) Rq of the reflective film formed on the end face is 1.5 nm or more.

[0017] (Configuration 11) A reflective mask comprising: a substrate having two opposing main surfaces and end faces connected to the outer edges of the two main surfaces; a reflective film formed on one of the main surfaces and on at least a portion of the end faces; and a thin film formed on the reflective film and having a transfer pattern, wherein the reflective film on the main surfaces has a structure in which low refractive index layers and high refractive index layers are alternately laminated, and the reflective film on the end faces has a single-layer structure containing the element most abundant in the low refractive index layer and the element most abundant in the high refractive index layer.

[0018] (Configuration 12) The reflective mask of configuration 11, characterized in that the ratio of the content [atomic %] of the element most abundant in the low refractive index layer to the total content [atomic %] of the element most abundant in the low refractive index layer and the element most abundant in the high refractive index layer contained in the reflective film formed on the end surface is less than 0.4. (Configuration 13) 13. The reflective mask according to structure 11 or 12, wherein the thickness of the reflective film at the portion formed on the end face is thinner than the thickness of the reflective film at the portion formed on the main surface.

[0019] (Configuration 14) 14. A reflective mask according to any one of structures 11 to 13, wherein the element most abundant in the low refractive index layer is molybdenum, and the element most abundant in the high refractive index layer is silicon. (Configuration 15) 15. The reflective mask according to any one of structures 11 to 14, wherein the surface roughness (root mean square roughness) Rq of the reflective film formed on the end face is 1.5 nm or more.

[0020] (Configuration 16) 16. A method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using a reflective mask according to any one of configurations 11 to 15. Effect of the Invention

[0021] According to the present invention, the reflective film on the end face has a single layer structure containing the element that is most abundant in the low refractive index layer and the element that is most abundant in the high refractive index layer, and therefore it is possible to provide a substrate with a reflective film and a mask blank that can suppress the occurrence of blisters, particularly in the reflective film formed on the end face of the substrate.

[0022] Furthermore, according to the present invention, by using this mask blank, it is possible to provide a reflective mask that can suppress the occurrence of blisters, particularly in the reflective film formed on the edge face of the substrate. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a semiconductor device using this reflective mask. [Brief description of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view showing a configuration of an embodiment of a substrate with a reflective film of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the film configuration of a reflective film. [Diagram 3] 1 is a cross-sectional view showing a configuration of an embodiment of a mask blank of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a reflective mask manufactured using the mask blank of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described in detail. [Substrate with reflective film] First, the substrate with a reflective film according to the present invention will be described. FIG. 1 is a cross-sectional view showing the configuration of one embodiment of a substrate with a reflective film of the present invention. As shown in FIG. 1, a substrate with a reflective film 10 according to an embodiment of the present invention includes a substrate 1 and a reflective film 2. The substrate 1 has two opposing main surfaces 1a, 1b, and end surfaces 1c, 1d connected to the outer edges of the two main surfaces 1a, 1b.

[0025] The substrate 1 used in the present invention is rectangular in shape, and has four end faces connected to the outer edges of the two main surfaces 1a and 1b. In the present invention, the term "end face" refers to these four end faces. In the cross-sectional view of FIG. 1, two end faces 1c and 1d facing the left and right sides of the substrate are shown, but the substrate also has two other end faces facing the front and back of the substrate. Therefore, the reflective film 2 is formed on at least a part of the other two end faces not shown in FIG. 1. In the following description of this embodiment, for convenience of explanation, the two end faces 1c and 1d will be described, but the same applies to the other two opposing end faces not shown in FIG. 1.

[0026] The reflective film 2 is formed on one main surface 1a and at least a part of the end faces 1c and 1d.

[0027] 2, the reflective film 2a formed on the main surface 1a has a multilayer structure in which low refractive index layers 21 and high refractive index layers 22 are alternately laminated. In this specification, the low refractive index and the high refractive index are based on the refractive index for the wavelength of EUV light. In addition, the reflective films 2c, 2d formed on the end faces 1c, 1d have a single-layer structure containing the element that is most abundant in the low refractive index layer 21 and the element that is most abundant in the high refractive index layer 22.

[0028] Here, the content of the element having the highest content in the low refractive index layer 21 is preferably more than 50 atomic %, more preferably 70 atomic % or more, and even more preferably 90 atomic % or more. Similarly, the content of the element having the highest content in the high refractive index layer 22 is preferably more than 50 atomic %, more preferably 70 atomic % or more, and even more preferably 90 atomic % or more.

[0029] On the other hand, the reflective films 2c, 2d formed on the end faces 1c, 1d may have a single layer structure containing a material in which the main component elements of the low refractive index layer 21 and the main component elements of the high refractive index layer 22 are mixed.

[0030] Here, the "main constituent elements" of the low refractive index layer 21 (high refractive index layer 22) refer to the constituent elements excluding elements whose content in the low refractive index layer 21 (high refractive index layer 22) is less than 5 atomic %. That is, the total content of the "main constituent elements" in the low refractive index layer 21 (high refractive index layer 22) in this case is 95 atomic % or more. Therefore, even if the formed reflective film contains, for example, impurity components contained in the target material or impurity components derived from structures such as a shield in the film formation chamber, such components are not the main constituent elements of the low refractive index layer or the high refractive index layer.

[0031] In the case of EUV exposure, the substrate 1 is set to a thickness of 0±1.0×10 in order to prevent distortion of the pattern due to heat during exposure. -7 / °C, more preferably within 0±0.3×10 -7 Materials having a low thermal expansion coefficient within the range of 100 / °C are preferably used, and examples of materials having a low thermal expansion coefficient within this range include SiO2-TiO2 glass and multi-component glass ceramics.

[0032] When the glass substrate is used as the substrate 1, the main surface of the glass substrate on which the transfer pattern is formed is surface-processed to have a high flatness from the viewpoint of obtaining at least pattern transfer accuracy and positional accuracy. In the case of EUV exposure, the main surface of the glass substrate on which the transfer pattern is formed has a flatness of preferably 0.1 μm or less, particularly preferably 0.05 μm or less, in a 132 mm×132 mm area or a 142 mm×142 mm area. In addition, the main surface on the side opposite to the side on which the transfer pattern is formed is a surface that is electrostatically chucked when set in an exposure device, and has a flatness of 1 μm or less, preferably 0.5 μm or less, in a 142 mm×142 mm area.

[0033] The reflective film 2 is a multilayer film in which low refractive index layers 21 and high refractive index layers 22 are alternately laminated, and generally, a multilayer film in which thin films of heavy elements or their compounds and thin films of light elements or their compounds are alternately laminated for about 40 to 60 periods is used. For example, as a reflective film for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films (low refractive index layers) and Si films (high refractive index layers) are alternately laminated in 40 or more periods is preferably used. Other multilayer reflective films used in the EUV light region include Ru / Si periodic multilayer films, Mo / Be periodic multilayer films, Mo compound / Si compound periodic multilayer films, Si / Nb periodic multilayer films, Si / Mo / Ru periodic multilayer films, Si / Mo / Ru / Mo periodic multilayer films, and Si / Ru / Mo / Ru periodic multilayer films. The material of the reflective film 2 may be appropriately selected depending on the exposure wavelength. The reflective film 2 can be formed by, for example, ion beam sputtering or atomic layer deposition (ALD).

[0034] In order to solve the above-mentioned problems, the present inventors have conducted extensive research, paying particular attention to the structure of the film that is attached to the edge of the substrate when forming a reflective film on the main surface of the substrate. As a result, the inventors have found that the reflective film attached to the edge of the substrate does not need to reflect the exposure light at all, and therefore does not need to have a multilayer film structure like the reflective film formed on the main surface of the substrate. Furthermore, the inventors have found that a single-layer film without an interface in the film can solve the problem from the viewpoint of suppressing the generation of blisters.

[0035] In the substrate with a reflective film 10 according to the present embodiment described above, when the reflective film 2 is formed on the main surface of the substrate 1, the reflective film 2c (or 2d) formed on the end face 1c (or 1d) of the substrate 1 has a single-layer structure containing an element (e.g., molybdenum) having the highest content in the low refractive index layer 21 and an element (e.g., silicon) having the highest content in the high refractive index layer 22. The reflective film 2c (or 2d) is formed by mixing and diffusing at least the element having the highest content in the low refractive index layer 21 and the element having the highest content in the high refractive index layer 22. Such a reflective film 2c (or 2d) is a film having a single-layer structure without a clear interface. In addition, the reflective film 2c (or 2d) is a single-layer film having no interface, which is formed by mixing and diffusing a main component element (e.g., molybdenum) of the low refractive index layer 21, which is the film constituent material of the reflective film 2, and a main component element (e.g., silicon) of the high refractive index layer 22. Therefore, even if a technique for suppressing the adhesion of contamination due to hydrogen radicals or hydrogen plasma is applied during EUV exposure using a mask blank and a reflective mask described below that are fabricated using the reflective film-coated substrate 10 of this embodiment, the risk of blisters occurring can be significantly reduced.

[0036] On the other hand, as described above, the reflective film 2c (or 2d) can also be a single-layer structure film having no interface, by mixing and diffusing a constituent element (e.g., molybdenum) of the main component of the low refractive index layer 21, which is the film-constituting material of the reflective film 2, and a constituent element (e.g., silicon) of the main component of the high refractive index layer 22. In this case, the reflective film-coated substrate 10 can also significantly reduce the risk of blisters occurring by applying a technique for suppressing adhesion of contamination due to hydrogen radicals or hydrogen plasma during EUV exposure using a mask blank and a reflective mask, which will be described later, produced using the reflective film.

[0037] The film configuration of the substrate with a reflective film according to the present invention may be such that, as shown in FIG. 1, at least a reflective film 2 that reflects exposure light (e.g., EUV light) is provided on a substrate 1, and the substrate may further include other films such as an undercoat layer (described below) and a protective film formed on the reflective film 2.

[0038] In the substrate 1 according to the present embodiment shown in Fig. 1, the end faces connected to the outer edges of the two opposing main surfaces 1a, 1b are surfaces that are substantially perpendicular to these two main surfaces, but the substrate end faces may have chamfered surfaces. In other words, when the end faces of the substrate have side faces that are substantially perpendicular to the two main surfaces and two chamfered surfaces that connect the side faces to the outer edges of the two main surfaces, and the reflective film 2 is formed on at least a portion of these side faces and chamfered surfaces, the "reflective film on the end faces" refers to the reflective film formed on at least a portion of these side faces and chamfered surfaces.

[0039] Similarly, in the substrate with reflective film 10 of the present embodiment, the ratio (hereinafter referred to as L / [L+H] ratio) of the content [atomic %] of the element (main component element of the low refractive index layer 21) contained in the reflective film 2c (or 2d) formed on the end face 1c (or 1d) with the highest content in the low refractive index layer 21 (main component element of the low refractive index layer 21, e.g., molybdenum) and the element (main component element of the high refractive index layer 22, e.g., silicon) with the highest content in the high refractive index layer 22 is preferably smaller than 0.4. From the viewpoint of reflectance, the reflective film 2a formed on the main surface 1a of the substrate 1 preferably has a thickness ratio of 4:6 between the low refractive index layer and the high refractive index layer (i.e., the L / [L+H] ratio of the entire reflective film 2a formed on the main surface 1a is 0.4.

[0040] In contrast, the reflective film 2c (or 2d) formed on the end face 1c (or 1d) of the present embodiment is a film with a single layer structure containing the element with the highest content in the low refractive index layer 21 and the element with the highest content in the high refractive index layer 22. Alternatively, the reflective film 2c (or 2d) is a film with a single layer structure in which the main component element of the low refractive index layer 21 and the main component element of the high refractive index layer 22 are mixed. In addition, the element with the highest content in the low refractive index layer 21 (the main component element of the low refractive index layer 21) is often a transition metal (e.g., molybdenum). The element with the highest content in the low refractive index layer 21 (the main component element of the low refractive index layer 21) has lower chemical resistance than the element with the highest content in the high refractive index layer 22 (the main component element of the high refractive index layer 22), and is easily dissolved from the single layer film. From this viewpoint, it can be said that the L / [L+H] ratio of the reflective film 2c (or 2d) formed on the end face 1c (or 1d) is preferably smaller than the L / [L+H] ratio of the entire reflective film 2a formed on the main surface 1a. The L / [L+H] ratio of the reflective film 2c (or 2d) formed on the end face 1c (or 1d) is preferably 0.33 or less, more preferably 0.3 or less. In particular, when the element with the highest content in the low refractive index layer 21 (the element constituting the main component of the low refractive index layer) is a transition metal and the element with the highest content in the high refractive index layer 22 (the element constituting the main component of the high refractive index layer) is silicon, the chemical resistance is improved when the content of the transition metal is less than the stoichiometrically stable ratio of transition metal:silicon=1:2 of the transition metal silicide material.

[0041] Furthermore, it is desirable that the film thickness of the portion of the reflective film 2 formed on the end face (the film thickness of the reflective film 2c (or 2d)) is thinner than the film thickness of the portion of the reflective film 2 formed on the main surface (the film thickness of the reflective film 2a). If the film thickness of the portion of the reflective film 2 formed on the end face is thick, there is a higher risk of dust generation due to film peeling at the substrate end face. Also, there is a higher possibility of an interface being formed in the film. The ratio of the film thickness of the reflective film 2c (or 2d) to the film thickness of the reflective film 2a is preferably 0.4 or less, and more preferably 0.3 or less.

[0042] The surface roughness (root-mean-square roughness) Rq of the reflective film 2c (or 2d) formed on the end face 1c (or 1d) is, for example, 1.5 nm or more. The surface roughness (root-mean-square roughness) Rq of the reflective film 2c (or 2d) is preferably 2 nm or more. On the other hand, the surface roughness (root-mean-square roughness) Rq of the reflective film 2c (or 2d) is preferably 3 nm or less.

[0043] As described above, according to the substrate with reflective film 10 of this embodiment, when the reflective film 2 is formed on the main surface of the substrate 1, the reflective film 2c (or 2d) formed on the end face 1c (or 1d) of the substrate 1 has a single layer structure containing an element (e.g., molybdenum) having the highest content in the low refractive index layer 21 and an element (e.g., silicon) having the highest content in the high refractive index layer 22. This reflective film 2c (or 2d) is a film with a single layer structure that does not have a clear interface. Furthermore, according to the substrate with a reflective film 10 of this embodiment, when the reflective film 2 is formed on the main surface of the substrate 1, the reflective film 2c (or 2d) formed on the end face 1c (or 1d) of the substrate 1 is a single-layer film having no interface, in which the main component element of the low refractive index layer (e.g., molybdenum) and the main component element of the high refractive index layer (e.g., silicon) which are the film constituent materials of the reflective film 2 are mixed and diffused. Therefore, even if a technique for suppressing the adhesion of contamination due to hydrogen radicals or hydrogen plasma is applied during EUV exposure using a reflective mask manufactured using the reflective film-coated substrate 10 of this embodiment, it is possible to significantly reduce the risk of blisters occurring.

[0044] [Mask blank] Next, a mask blank according to the present invention will be described. A mask blank according to the present invention comprises a substrate having two opposing main surfaces and an end face connected to outer edges of the two main surfaces, a reflective film formed on one of the main surfaces and on at least a part of the end face, and a thin film for pattern formation formed on the reflective film, wherein the reflective film on the main surfaces has a structure in which low-refractive index layers and high-refractive index layers are alternately laminated, and the reflective film on the end face has a single-layer structure containing the element most abundant in the low-refractive index layer and the element most abundant in the high-refractive index layer.

[0045] Alternatively, a mask blank according to the present invention is a mask blank comprising a substrate, a reflective film, and a thin film for pattern formation, the substrate having two opposing main surfaces and an end face connected to outer edges of the two main surfaces, the reflective film being formed on one of the main surfaces and at least a part of the end face, the reflective film on the main surface having a structure in which low-refractive-index layers and high-refractive-index layers are alternately laminated, the reflective film on the end face having a single-layer structure containing a material in which a constituent element of a main component of the low-refractive-index layer and a constituent element of a main component of the high-refractive-index layer are mixed, and the thin film for pattern formation is formed on the reflective film.

[0046] The film configuration of the mask blank according to the present invention may be such that it has at least a reflective film that reflects exposure light (e.g., EUV light) and a thin film for pattern formation on a substrate, and may have other films such as an undercoat layer described below, a protective film formed on the reflective film, and an etching mask film formed on the thin film for pattern formation. The thin film for pattern formation may be an absorber film that absorbs EUV light. The thin film for pattern formation may be a phase shift film that has a function of transmitting EUV light at a predetermined transmittance and a function of generating a predetermined phase difference between EUV light that has passed through the thin film, been reflected at the interface with the reflective film, and been emitted again from the thin film, and EUV light that has passed through a vacuum and been directly reflected by the reflective film.

[0047] The mask blank according to the present invention is also characterized in that the reflective film is formed on one of the main surfaces and at least a part of the end surface, the reflective film on the main surface has a structure in which low-refractive index layers and high-refractive index layers are alternately laminated, and the reflective film on the end surface has a single-layer structure containing a material in which a constituent element of the main component of the low-refractive index layer and a constituent element of the main component of the high-refractive index layer are mixed. These characteristics are as explained in detail in the above-mentioned "substrate with reflective film", so a duplicate explanation will be omitted here.

[0048] Moreover, the following points regarding the mask blank according to the present invention are the same as those in the case of the above-mentioned "substrate with reflective film," so a description thereof will be omitted here. (1) The ratio (L / [L+H] ratio) of the content [atomic %] of the element most abundant in the low refractive index layer (the main component element of the low refractive index layer) to the total content [atomic %] of the element most abundant in the low refractive index layer (the main component element of the low refractive index layer) and the element most abundant in the high refractive index layer (the main component element of the high refractive index layer) contained in the reflective film formed on the end face is less than 0.4. (2) The thickness of the portion of the reflective film formed on the end face is thinner than the thickness of the portion of the reflective film formed on the main surface. (3) The low refractive index layer is made of, for example, a material containing molybdenum, and the high refractive index layer is made of, for example, a material containing silicon. (4) The surface roughness (root-mean-square roughness) Rq of the reflective film formed on the end face is 1.5 nm or more. (5) Any other matters related to (1) to (4).

[0049] Fig. 3 is a cross-sectional view showing the configuration of an embodiment of a mask blank of the present invention, in which the same reference numerals are used to designate the same parts as those in Fig. 1. 3 according to an embodiment of the present invention includes a substrate 1, a reflective film 2 that reflects, for example, EUV light, formed on the substrate 1, a protective film 3, and a pattern-forming thin film 4. In this embodiment, a case will be described in which the pattern-forming thin film 4 is an absorber film that absorbs exposure light (for example, EUV light).

[0050] The details of the substrate 1 and the reflective film 2 are as described above.

[0051] In the case of EUV exposure, as described above, a glass substrate having a low thermal expansion coefficient such as SiO2-TiO2-based glass is preferably used as the substrate 1, but it may be difficult to achieve high smoothness of, for example, 0.1 nm or less in RMS (root mean square roughness) as the surface roughness of such a glass substrate by precision polishing. Therefore, it is preferable to form an underlayer (not shown) on the surface of the glass substrate (above substrate 1) for the purpose of reducing the surface roughness of the glass substrate or reducing defects on the glass substrate surface. As the material of such an underlayer, it is not necessary to have translucency to the exposure light, and a material that can obtain high smoothness and good defect quality when the underlayer surface is precision polished is preferably selected. For example, Si or a silicon compound containing Si (e.g., SiO2, SiON, etc.) is preferably used because it can obtain high smoothness and good defect quality when precision polished. As the material of the underlayer, Si is particularly preferable.

[0052] The surface of such an underlayer is preferably precision-polished to have a smoothness required for a mask blank substrate. The surface of the underlayer is desirably precision-polished to have a root-mean-square roughness (Rq) of 0.15 nm or less, more preferably 0.1 nm or less. In addition, in consideration of the influence on the surface of the reflective film 2 formed on the underlayer, the surface of the underlayer is desirably precision-polished to have a relationship with the maximum surface roughness (Rmax) of preferably Rmax / Rq of 2 to 10, more preferably 2 to 8. The thickness of the underlayer is preferably in the range of, for example, 75 nm to 300 nm.

[0053] In general, in order to protect the reflective film 2 during patterning or pattern correction of the above-mentioned pattern-forming thin film 4, it is desirable to provide a protective film 3 between the reflective film 2 and the pattern-forming thin film 4 as in this embodiment.

[0054] The protective film 3 is formed on the reflective film 2 to protect the reflective film 2 from dry etching and cleaning in the manufacturing process of the reflective mask 30. In addition, the protective film 3 can protect the reflective film 2 during black defect correction (EB defect correction) of a transfer pattern using an electron beam (EB). The protective film 3 can have a laminated structure of three or more layers. For example, the protective film 3 can have a structure in which the bottom layer and the top layer are layers made of a material containing Ru, and a metal other than Ru or an alloy of a metal other than Ru is interposed between the bottom layer and the top layer. The material of the protective film 3 is composed of, for example, a material containing ruthenium as a main component. As the material containing ruthenium as a main component, Ru metal alone or a Ru alloy containing Ru and metals such as titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La), cobalt (Co), and / or rhenium (Re) can be used. Moreover, these materials for the protective film 3 may further contain nitrogen. The protective film 3 is effective when the pattern-forming thin film 4 is patterned by dry etching using a Cl-based gas.

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

[0056] The protective film 3 may be provided on the reflective film 2c (or 2d) formed on the end face 1c (or 1d), but it is not essential to provide it. The reflective film 2c (or 2d) on the end face 1c (or 1d) often does not have a pattern-forming thin film 4 provided thereon, and is less susceptible to dry etching or EB defect correction. Furthermore, the reflective film 2c (or 2d) is a single-layer structure film containing the element with the highest content in the low refractive index layer and the element with the highest content in the high refractive index layer, or a single-layer structure film formed of a material in which the constituent elements of the main components of the low refractive index layer and the main components of the high refractive index layer are mixed, and has high resistance to these, including chemical resistance. For these reasons, there is little need to provide the protective film 3 on the reflective film 2c (or 2d). Note that the surface layer of the reflective film 2c (or 2d) (for example, a region 5 nm or less from the surface) may have a composition in which the constituent elements of the protective film 3 are also mixed.

[0057] In the mask blank 20 of this embodiment, the pattern-forming thin film 4 may be a single-layer film or a multi-layer film made up of multiple films. In the case of a single-layer film, the number of steps in manufacturing the mask blank can be reduced, improving production efficiency. In the case of a multi-layer film, the optical constants and film thickness of the upper thin film can be appropriately set so that it serves as an anti-reflection film during the mask pattern defect inspection using light. This improves the inspection sensitivity during the mask pattern defect inspection using light. In addition, if a film containing oxygen (O) and nitrogen (N), which improve oxidation resistance, is used as the upper thin film, the stability over time is improved.

[0058] The material of the pattern-forming thin film 4 is not particularly limited as long as it has a function of absorbing EUV light and can be processed by etching or the like (preferably by dry etching with chlorine (Cl) and / or fluorine (F)-based gas). As a material having such a function, tantalum (Ta) alone or a material containing Ta can be preferably used.

[0059] Examples of materials containing Ta include materials containing Ta and B, materials containing Ta and N, materials containing Ta, B and at least one of O and N, materials containing Ta and Si, materials containing Ta, Si and N, materials containing Ta and Ge, materials containing Ta, Ge and N, materials containing Ta and Pd, materials containing Ta and Ru, and materials containing Ta and Ti.

[0060] The pattern-forming thin film 4 can be formed from a material containing at least one selected from the group consisting of, for example, simple Ni, a material containing Ni, simple Cr, a material containing Cr, simple Ru, a material containing Ru, simple Pd, a material containing Pd, simple Mo, and a material containing Mo.

[0061] The pattern-forming thin film 4 can be formed by, for example, a sputtering method. The thickness of the pattern-forming thin film 4 is preferably in the range of, for example, 25 nm to 70 nm.

[0062] In addition, an etching mask film may be provided on the pattern-forming thin film 4. By providing the etching mask film, the resist film formed on the absorber film can be made thinner when patterning the pattern-forming thin film 4, so that a fine pattern can be formed on the pattern-forming thin film 4 with high accuracy.

[0063] Such an etching mask film is made of a material having etching selectivity with respect to the pattern-forming thin film 4, and when the absorber film is made of the tantalum-based material, the etching mask film is preferably made of, for example, a chromium-based material. Examples of chromium-based materials include chromium (Cr) alone or chromium compounds (chromium oxide, chromium nitride, chromium oxynitride, chromium carbide, etc.). The etching mask film can be formed by, for example, a sputtering method, and the thickness of the etching mask film is preferably in the range of, for example, 5 nm to 15 nm.

[0064] The mask blank 20 according to the present embodiment as shown in Fig. 3 described above can be manufactured by successively forming the reflective film 2, the protective film 3, and the pattern-forming thin film 4 on the substrate 1. If necessary, a base layer (not shown) can be formed between the substrate 1 and the reflective film 2. If necessary, an etching mask film (not shown) can be formed on the pattern-forming thin film 4.

[0065] Also in the mask blank 20 according to the present embodiment described above, when the reflective film 2 is formed on the main surface of the substrate 1, the film formed on the edge face of the substrate 1 is a single-layer film in which the film constituent materials of the reflective film 2, for example, Si and Mo, are mixed and diffused and have no interface. Therefore, even if a technique for suppressing adhesion of contamination due to hydrogen radicals or hydrogen plasma is used during EUV exposure, it is possible to significantly reduce the risk of blisters occurring.

[0066] [Reflective mask] The present invention also provides a reflective mask. The reflective mask according to the present invention is a reflective mask characterized in that a transfer pattern is provided on the pattern-forming thin film of the mask blank having the above-mentioned configuration. Fig. 4 is a cross-sectional view of a reflective mask manufactured using the mask blank of the present invention, in which the same reference numerals are used to designate the same parts as those in Fig. 1 or 3. FIG. 4 shows a reflective mask 30 having a transfer pattern 4a formed by patterning the pattern-forming thin film 4 in the mask blank 20 shown in FIG.

[0067] For example, photolithography is the most suitable method for patterning the pattern-forming thin film 4 in the above-mentioned mask blank 20. That is, in order to obtain the reflective mask of the present invention, a manufacturing method is suitable which includes at least the steps of forming a resist film on the surface of the mask blank 20 using the above-mentioned mask blank 20, forming a resist pattern on this resist film by electron beam drawing and development, and patterning the above-mentioned pattern-forming thin film 4 by dry etching using the formed resist pattern as a mask.

[0068] As described above, in the reflective mask 30 according to the present embodiment, when the reflective film 2 is formed on the main surface of the substrate 1, the film formed on the end face of the substrate 1 is a single-layer film in which the film constituent materials of the reflective film 2, for example, Si and Mo, are mixed and diffused and have no interface. Therefore, even if a technique for suppressing adhesion of contamination due to hydrogen radicals or hydrogen plasma is applied during EUV exposure using this reflective mask 30, it is possible to suppress the occurrence of blisters and significantly reduce the risk of blister occurrence.

[0069] [Method of manufacturing semiconductor devices] The present invention also provides a method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the above-mentioned reflective mask. By using the reflective mask according to the present invention, it is possible to significantly reduce the risk of blisters occurring during EUV exposure, even if a technique for suppressing contamination adhesion due to hydrogen radicals or hydrogen plasma is used. Therefore, according to the present invention, it is possible to perform good pattern transfer and manufacture high-quality semiconductor devices on which highly accurate device patterns are formed. EXAMPLES

[0070] The following examples further illustrate the embodiments of the present invention. Example 1 A SiO2-TiO2-based glass substrate (size: about 152.4 mm x about 152.4 mm, thickness: about 6.35 mm) was prepared by polishing in stages with cerium oxide abrasive grains and colloidal silica abrasive grains using a double-sided polishing machine, and then treating the substrate surface with low-concentration hydrosilicofluoric acid. The surface roughness of the obtained glass substrate 1 was 0.20 nm in terms of root-mean-square roughness (Rq). The surface roughness was measured with an atomic force microscope (AFM), and the measurement area was 1 μm x 1 μm.

[0071] Next, a conductive backside film (not shown) having a laminated structure of a lower layer made of CrON and an upper layer made of CrN was formed on the main surface 1b (the main surface opposite to the main surface 1a on the side where the reflective film 2 is provided) of the glass substrate 1. The lower layer (CrON layer) was formed to a thickness of 15 nm by reactive sputtering (DC magnetron sputtering) using a Cr target in a mixed gas atmosphere of Ar gas, N2 gas, and O2 gas. The upper layer (CrN layer) was formed to a thickness of 180 nm by reactive sputtering (DC magnetron sputtering) using a Cr target in a mixed gas atmosphere of Ar gas and N2 gas. The composition (atomic %) of the CrN layer was measured by X-ray photoelectron spectroscopy (XPS method), and the atomic ratio was 91 atomic % for chromium (Cr) and 9 atomic % for nitrogen (N).

[0072] Next, a reflective film 2 (total thickness 280 nm) consisting of a multilayer film was formed on the main surface 1a of the glass substrate 1 by stacking 40 periods of a high refractive index layer Si film (thickness: 2.8 nm) and a low refractive index layer Mo film (thickness: 4.2 nm) on the main surface 1a of the glass substrate 1 using an ion beam sputtering device. Specifically, the conductive back surface film of the glass substrate 1 was fixed to the stage of the ion beam sputtering device with an electrostatic chuck, and sputter particles (Si particles and Mo particles) were made to enter the main surface 1a of the glass substrate from an oblique direction to deposit on the main surface 1a and the end faces 1c and 1d, respectively, to form the reflective film 2. During this film formation, the end faces 1c and 1d of the glass substrate were not masked with a shield or the like. Through the above steps, a substrate with a reflective film of Example 1 was obtained.

[0073] The reflective film was formed not only on the main surface 1a of the glass substrate but also on the end surfaces (four end surfaces including 1c and 1d) of the glass substrate. The reflective film on the end surface of the glass substrate was analyzed using a transmission electron microscope (TEM). As a result, it was confirmed that the film thickness of the part of the reflective film formed on the end surface was thinner than that of the part of the reflective film formed on the main surface (about 40 nm). It was also confirmed that the reflective film on the end surface of the glass substrate was a single-layer structure, not a multilayer structure. Therefore, the reflective film on the end surface of the glass substrate does not have a reflecting function for the exposure light. In addition, the composition of the reflective film on the end surface of the glass substrate was analyzed using an energy dispersive transmission electron microscope (TEM-EDX), and it was confirmed that the reflective film contained the above-mentioned Si and Mo. That is, when the reflective film was formed on the main surface of the glass substrate, the film that was attached to the end surface of the glass substrate by wrapping around the end surface of the glass substrate was a single-layer structure film in which the film constituent materials of the reflective film, Si and Mo, were mixed and diffused, and did not have an interface.

[0074] The ratio of the content [atomic %] of Mo, which is a constituent element of the main component of the low refractive index layer contained in the reflective film formed on the end face of the substrate, divided by the total content [atomic %] of Mo, which is a constituent element of the main component of the low refractive index layer, and Si, which is a constituent element of the main component of the high refractive index layer, was 0.25. The surface roughness (root mean square roughness) Rq of the reflective film formed on the end face was 2 nm or more.

[0075] Next, using the same method as described above, a conductive back surface film was formed on the main surface 1b of the glass substrate 1, and a reflective film consisting of a multilayer film was formed on the main surface 1a by stacking 40 periods of Si films and Mo films, thereby obtaining a substrate with a reflective film. Next, using a DC magnetron sputtering device, a protective film (thickness: 2.5 nm) made of Ru, and an absorber film consisting of a laminated film of a TaN film (thickness: 48 nm, composition Ta:N=70 atomic %:30 atomic %) and a TaO film (thickness: 11 nm, composition Ta:O=35 atomic %:65 atomic %) were formed on the reflective film of the reflective film-coated substrate. Each composition was measured by X-ray photoelectron spectroscopy (XPS). In this manner, a mask blank (reflective mask blank) was produced.

[0076] Next, a reflective mask was produced using this mask blank. First, a positive resist film for electron beam lithography was formed as a resist film on the surface of the absorber film of the mask blank to a thickness of 80 nm. The resist film was formed by spin coating using a spinner (spin coating device).

[0077] Next, a predetermined mask pattern was drawn on the above-mentioned resist film by an electron beam drawing machine, and then development was carried out to form a resist pattern.

[0078] Next, using this resist pattern as a mask, the absorber film was etched away by a fluorine-based gas (CF4 gas) to remove the TaO film and a chlorine-based gas (Cl2 gas) to remove the TaN film, thereby forming an absorber film pattern. Furthermore, the resist pattern remaining on the absorber film pattern was removed with hot sulfuric acid to obtain the reflective mask for EUV lithography of Example 1. When the reflective films 2c and 2d on the end faces 1c and 1d of this reflective mask of Example 1 were observed, it was confirmed that there was no noticeable film loss.

[0079] When the reflective mask obtained as described above is set in an EUV exposure device and a pattern is transferred onto a semiconductor substrate on which a resist film is formed, it is desirable to make the exposure chamber have a hydrogen atmosphere such as hydrogen radicals in order to suppress contamination adhesion to the mirror and mask of the exposure device during EUV exposure, as described above. In the case of the reflective mask according to this embodiment, when the reflective film is formed on the main surface of the glass substrate, as described above, the film formed on the end surface of the glass substrate is not a multilayer film structure, but a single-layer film in which the film constituent materials of the reflective film, Si and Mo, are mixed and diffused and have no interface, so that it is possible to greatly reduce the risk of blisters occurring during EUV exposure, even if a technology for suppressing contamination adhesion due to hydrogen radicals or hydrogen plasma is used. Therefore, according to the present invention, good pattern transfer can be performed.

[0080] (Comparative Example) As in Example 1, a SiO2-TiO2-based glass substrate (size: about 152.4 mm x about 152.4 mm, thickness: about 6.35 mm) was prepared by polishing in stages with cerium oxide abrasive grains and colloidal silica abrasive grains using a double-sided polishing machine and then treating the substrate surface with low-concentration hydrosilicofluoric acid. The surface roughness of the obtained glass substrate 1 was 0.25 nm in terms of root-mean-square roughness (Rq). The surface roughness was measured with an atomic force microscope (AFM) and the measurement area was 1 μm x 1 μm.

[0081] Next, using the same procedure as in Example 1, a conductive back surface film (not shown) having a laminated structure of a lower layer made of CrON and an upper layer made of CrN was formed on main surface 1b of glass substrate 1.

[0082] Next, on the main surface 1a of the glass substrate 1, a reflective film (total thickness 280 nm) consisting of a multilayer film was formed by stacking 40 periods of a high refractive index layer Si film (thickness: 2.8 nm) and a low refractive index layer Mo film (thickness: 4.2 nm) on the main surface 1a of the glass substrate 1 using an ALD (Atomic Layer Deposition) device (a film formation device using atomic layer deposition). Si particles and Mo particles were incident on the main surface 1a of the glass substrate from an oblique direction, respectively, and deposited on the main surface 1a and the end faces 1c and 1d, respectively, to form a reflective film 2. During this film formation, the end faces 1c and 1d of the glass substrate were not masked with a shield or the like. Through the above steps, a substrate with a reflective film of the comparative example was obtained.

[0083] The reflective film was formed not only on the main surface of the glass substrate, but also on the end surface of the glass substrate. The structure of the reflective film on the end surface of the glass substrate was analyzed using a transmission electron microscope (TEM). As a result, it was confirmed that the reflective film on the end surface of the glass substrate had a multilayer structure in which Si films and Mo films were alternately laminated, similar to the reflective film formed on the main surface. In other words, when the reflective film was formed on the main surface of the glass substrate, the film that was attached to the end surface of the glass substrate by wrapping around was a multilayer structure having an interface.

[0084] Next, using the same method as described above, a conductive back surface film was formed on the main surface 1b of the glass substrate 1, and a reflective film consisting of a multilayer film was formed on the main surface 1a by stacking 40 periods of Si films and Mo films, thereby obtaining a substrate with a reflective film. Next, in the same manner as in the above-mentioned Example 1, a protective film made of Ru and an absorber film made of a laminated film of a TaN film and a TaO film were formed on the reflective film of this reflective film-coated substrate, thereby producing a mask blank (reflective mask blank) of the comparative example.

[0085] Next, using this mask blank, a reflective mask for EUV lithography as a comparative example was produced in the same manner as in Example 1 described above.

[0086] When the reflective mask obtained as described above is set in an EUV exposure device and a pattern is transferred onto a semiconductor substrate on which a resist film is formed, it is desirable to apply a technique for suppressing adhesion of contamination due to hydrogen radicals or hydrogen plasma during EUV exposure. However, in the case of the reflective mask according to this comparative example, as described above, the film formed on the end face of the glass substrate has a multi-layered film structure and has an interface between each layer, so that if a technique for suppressing adhesion of contamination due to hydrogen radicals or hydrogen plasma is used during EUV exposure, the risk of blisters occurring in the film on the end face of the substrate increases, which may cause contamination inside the exposure chamber, for example, making it difficult to perform good pattern transfer. [Explanation of symbols]

[0087] 1 Board 1a, 1b main surface 1c, 1d end face 2 Reflective film 2a Reflective film on the main surface of the substrate 2c, 2d Reflective film on the edge of the substrate 21 Low refractive index layer 22 High refractive index layer 3 Protective film 4 Thin films for pattern formation 4a Transcription pattern 10. Substrate with reflective film 20 Mask Blanks 30 Reflective mask

Claims

1. A substrate with a reflective film, a substrate having two opposing main surfaces and an end surface connected to outer edges of the two main surfaces; a reflective film formed on one of the main surfaces and at least a part of the end surface, the reflective film on the main surface has a structure in which low refractive index layers and high refractive index layers are alternately laminated, the reflective film on the end surface has a single-layer structure containing the element with the highest content in the low-refractive-index layer and the element with the highest content in the high-refractive-index layer, a L / [L+H] ratio of the content [atomic %] of the element most abundant in the low refractive index layer to the total content [atomic %] of the element most abundant in the low refractive index layer and the element most abundant in the high refractive index layer, which are contained in the reflective film formed on the end face, is smaller than the L / [L+H] ratio of the entire reflective film on the main surface.

2. A substrate with a reflective film as described in Claim 1, characterized in that the film thickness of the portion formed on the end surface of the reflective film is thinner than the film thickness of the portion formed on the main surface of the reflective film.

3. A substrate with a reflective film as described in claim 1 or 2, characterized in that the ratio of the film thickness of the portion of the reflective film formed on the end surface to the film thickness of the portion of the reflective film formed on the main surface is 0.4 or less.

4. A substrate with a reflective film described in any one of claims 1 to 3, characterized in that the element most abundant in the low refractive index layer is molybdenum, and the element most abundant in the high refractive index layer is silicon.

5. A substrate with a reflective film described in any one of claims 1 to 4, characterized in that the surface roughness (root mean square roughness) Rq of the reflective film formed on the end face is 1.5 nm or more.

6. A mask blank characterized by having a substrate with a reflective film described in any one of claims 1 to 5 and a thin film for pattern formation formed on the reflective film of the substrate with a reflective film.

7. A reflective mask comprising a substrate with a reflective film according to any one of claims 1 to 5, and a thin film formed on the reflective film of the substrate with a reflective film and having a transfer pattern.

8. A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the reflective mask described in claim 7.

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