Reflective photomask manufacturing method

Abstract

SOLUTION: To provide a reflection type photomask blank including: a substrate; a multilayer reflection film for reflecting exposure light which is extreme ultraviolet region light; a protective film for protecting the multilayer reflection film; a light absorption film for absorbing the exposure light; and a hard mask film formed in contact with the light absorption film, where the hard mask is constituted by a multilayer including a first layer formed from a material containing silicon and containing no chromium, and disposed on the side most alienated from the substrate, and a second layer formed from a material containing chromium and containing no silicon.EFFECT: A resist pattern for forming a refined assist pattern can be made hard to collapse against impact in a development process of resist pattern formation, and an assist pattern with a line width of about 30 nm, particularly about 25 nm can be favorably formed by thinning the thickness of a resist film. Therefore, high resolution can be obtained in a transfer pattern of a reflection type photomask produced from a reflection type photomask blank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective photomask for use in the manufacture of semiconductor devices and the like. Ku's Manufacturing method By law Regarding. [Background technology]

[0002] As semiconductor devices become increasingly miniaturized, particularly with the increasing integration of large-scale integrated circuits, higher pattern resolution is required for projection exposure. To address this issue, phase-shift masks have been developed as a photomask technique for improving the resolution of transferred patterns. The principle of phase-shifting is that the phase of light passing through an opening in the phase-shift film of a photomask is adjusted to be approximately 180 degrees inverted relative to the phase of light passing through the portion of the phase-shift film adjacent to the opening. This causes interference between the transmitted light at the boundary between the opening and the adjacent portion, reducing the light intensity. As a result, the resolution and depth of focus of the transferred pattern are improved. Photomasks that use this principle are collectively called phase-shift masks.

[0003] Phase shift mask blanks, which are used to manufacture phase shift masks, are most commonly constructed by laminating a phase shift film on a transparent substrate such as a glass substrate, and then laminating a film made of a chromium (Cr)-containing material on the phase shift film. Phase shift films typically have a phase difference of 175 to 185 degrees and a transmittance of approximately 6 to 30% relative to the exposure light. They are typically made of silicon (Si)-containing films, particularly those made of materials containing molybdenum (Mo) and silicon (Si). The chromium-containing film is typically adjusted to a thickness that, combined with the phase shift film, achieves the desired optical density. The chromium-containing film is typically used as both a light-shielding film and a hard mask when etching the phase shift film.

[0004] A typical method for manufacturing a phase shift mask by patterning a phase shift film from a phase shift mask blank having a transparent substrate on which a phase shift film made of a silicon-containing material and a light-shielding film made of a chromium-containing material are formed in this order is as follows: First, a resist film is formed on the light-shielding film made of a chromium-containing material of the phase shift mask blank, and a pattern is written on the resist film using light or an electron beam and developed to form a resist pattern. Next, using the resist pattern as an etching mask, the light-shielding film made of a chromium-containing material is etched with a chlorine-based gas to form a light-shielding film pattern. Furthermore, using the light-shielding film pattern as an etching mask, the phase shift film made of a silicon-containing material is etched with a fluorine-based gas to form a phase shift film pattern, and then the resist pattern is removed, and the light-shielding film pattern is removed by etching with a chlorine-based gas.

[0005] In this case, the light-shielding film is left outside the portion where the phase shift film pattern (circuit pattern) is formed, and the outer peripheral edge of the phase shift mask is made into a light-shielding portion (light-shielding pattern) with an optical density of 3 or more, which is the combination of the phase shift film and the light-shielding film. This is to prevent exposure light from leaking from the outer peripheral edge of the phase shift mask and irradiating the resist film on the adjacent chip of the wafer from the portion outside the circuit pattern when the circuit pattern is transferred to the wafer using a wafer exposure device. A typical method for forming such a light-shielding pattern involves forming a phase shift film pattern, removing the resist pattern, forming a new resist film, and then patterning and developing the resist pattern, leaving the resist film on the outer peripheral edge of the phase shift mask. Using this resist pattern as an etching mask, a film made of a chromium-containing material is etched, leaving the light-shielding film on the outer peripheral edge of the phase shift mask.

[0006] For phase shift masks, which require highly accurate pattern formation, dry etching using gas plasma is the mainstream method of etching. For dry etching of films made of chromium-containing materials, dry etching using chlorine-based gases (chlorine-based dry etching) is used, while for dry etching of silicon-containing films or films containing molybdenum and silicon, dry etching using fluorine-based gases (fluorine-based dry etching) is used. In particular, for dry etching of films made of chromium-containing materials, it is known that using an etching gas in which 10 to 25 volume percent of oxygen gas (O2 gas) is mixed with chlorine gas (Cl2 gas) increases chemical reactivity and improves the etching rate.

[0007] As circuit patterns become finer, technology is required to form finer circuit patterns on phase shift masks. In particular, assist patterns for line patterns, which support the resolution of the main pattern of a phase shift mask, must be smaller than the main pattern so that they are not transferred to the wafer when the circuit pattern is transferred to the wafer using a wafer exposure tool. For phase shift masks of the generation in which the half pitch of the circuit line and space pattern on the wafer is 10 nm, the line width of the assist patterns for the circuit line pattern on the phase shift mask is required to be approximately 40 nm.

[0008] Chemically amplified resists, which can form fine patterns, consist of a base resin, an acid generator, a surfactant, etc., and can be used in many reactions in which the acid generated by exposure acts as a catalyst, making it possible to achieve high sensitivity, and the use of chemically amplified resists makes it possible to form mask patterns such as fine phase shift film patterns with line widths of 0.1 μm or less. The resist is applied to a photomask blank by spin coating using a resist coater.

[0009] The thickness of the resist film used in cutting-edge phase shift mask blanks is 100 to 150 nm. The reason why it is difficult to form a finer assist pattern on a phase shift mask is that the resist pattern for forming the assist pattern, which is formed on a light-shielding film made of a material containing chromium, has a high aspect ratio, and therefore collapses due to impact with the developer or pure water during the rinsing process in the development step of resist pattern formation.

[0010] Therefore, in order to reduce the impact of the developer or pure water, it has been considered to reduce the aspect ratio of the resist pattern. In this case, the resist film is thinned. However, if the resist film is thinned, if the resist film disappears during dry etching of the light-shielding film made of a material containing chromium, pinhole defects will be formed in the light-shielding film made of a material containing chromium. When the phase shift film is dry-etched using the light-shielding film made of a material containing chromium as an etching mask, plasma generated during etching of the phase shift film will reach the phase shift film through the pinholes, causing pinhole defects in the phase shift film, making it impossible to manufacture a normal phase shift mask.

[0011] To solve this problem, a hard mask film made of a silicon-containing material is provided on a light-shielding film made of a chromium-containing material. In this case, the hard mask film made of a silicon-containing material is a thin film with a thickness of 5 to 15 nm, and the resist film formed on the hard mask film is thin, with a thickness of 80 to 110 nm.

[0012] When dry etching a light-shielding film made of a material containing chromium using a chlorine-based gas, it is necessary to perform over-etching of 100 to 300% of the clear time in addition to the clear time required for the light-shielding film made of a material containing chromium to disappear. This is because chlorine-based dry etching is an isotropic etching dominated by chemical components, and the pattern of the light-shielding film made of a material containing chromium is insufficiently etched at the boundary with the phase shift film, resulting in a footing shape and preventing the desired pattern width from being stably formed.

[0013] Furthermore, because this is isotropic etching is dominated by chemical components, chlorine-based plasma moves both vertically and horizontally relative to the substrate, causing side etching of the light-shielding film pattern made of a material containing chromium. To make the critical dimension (CD), which is the pattern line width, uniform across the entire mask surface, it is necessary to obtain the same amount of side etching across the entire mask surface. To achieve this, long dry etching is required until the amount of side etching stabilizes due to saturation.

[0014] On the other hand, when dry etching a phase shift film made of a silicon-containing material using a fluorine-based gas, over-etching is performed for up to about 20% of the clear time (e.g., a short over-etching of 1 to 6 seconds) in addition to the clear time required for the silicon-containing phase shift film to disappear, and the transparent substrate in contact with the phase shift film is also slightly etched by dry etching to adjust the phase difference to 175 to 185 degrees with respect to the exposure light. In this case, the phase shift film made of a silicon-containing material is generally set to have an initial phase difference of 175 to 179 degrees, and the transparent substrate is then dug by over-etching to achieve the desired phase difference, i.e., 175 to 185 degrees.

[0015] The reason why fluorine-based dry etching requires only a short period of over-etching is that fluorine-based dry etching is anisotropic etching in which the physical component is dominant, and the pattern of the phase shift film made of a material containing silicon does not have a trailing shape at the boundary with the substrate, and the fluorine-based plasma moves in a direction perpendicular to the substrate surface, faithfully reproducing the CD of the light-shielding film made of a material containing chromium that functions as an etching mask, so long over-etching is not required.

[0016] Since fluorine-based dry etching is anisotropic etching dominated by physical components, the amount of resist loss is generally greater than that in chlorine-based dry etching. Therefore, a resist film for forming a pattern on a hard mask film made of a silicon-containing material must have a certain thickness. However, a hard mask film made of a silicon-containing material functions as an etching mask when dry etching a light-shielding film made of a chromium-containing material using a chlorine-based gas, and has sufficient etching resistance to the chlorine-based gas. This allows the hard mask film made of a silicon-containing material to be thin. A thinner hard mask film made of a silicon-containing material shortens the time required for fluorine-based dry etching of the hard mask film, thereby reducing the thickness of the resist film required for forming a pattern on a hard mask film made of a silicon-containing material. For these reasons, using a hard mask film made of a silicon-containing material allows the resist film used for etching the hard mask film, i.e., the resist film initially used in a phase shift mask blank, to be thin. Furthermore, by thinning the resist film, the aspect ratio of the resist pattern is reduced, which reduces the effects of impact from the developer in the development step of resist pattern formation or from pure water during the rinsing process, making it possible to form a good assist pattern and achieve high resolution in the transfer pattern.

[0017] A typical method for manufacturing a phase shift mask by patterning a phase shift film from a phase shift mask blank having a transparent substrate on which a phase shift film made of a silicon-containing material, a light-shielding film made of a chromium-containing material, and a hard mask film made of a silicon-containing material are formed in this order is as follows: First, a resist film is formed on the hard mask film, and a pattern is written on the resist film using light or an electron beam and developed to form a resist pattern. Next, using the resist pattern as an etching mask, the hard mask film made of a silicon-containing material is dry-etched with a fluorine-based gas to form a hard mask film pattern, and then the resist pattern is removed. Next, using the hard mask film pattern as an etching mask, the light-shielding film made of a chromium-containing material is dry-etched with a chlorine-based gas to form a light-shielding film pattern. Furthermore, using the light-shielding film pattern as an etching mask, the phase shift film made of a silicon-containing material is dry-etched with a fluorine-based gas to form a phase shift film pattern, and simultaneously the hard mask film pattern is removed, and then the light-shielding film pattern is removed by etching with a chlorine-based gas.

[0018] Furthermore, the higher pattern resolution required for projection exposure in recent years has become difficult to achieve even with phase shift masks, so EUV lithography, which uses extreme ultraviolet light for exposure, has come to be used.

[0019] Extreme ultraviolet light is easily absorbed by all materials, making it impossible to use transmission lithography such as conventional photolithography using ArF excimer laser light. For this reason, EUV lithography uses a reflective optical system. The wavelength of extreme ultraviolet light used in EUV lithography is 13 to 14 nm, while the wavelength of conventional ArF excimer laser light is 193 nm. Therefore, compared to photolithography using conventional ArF excimer laser light, the exposure wavelength is shorter and it is possible to transfer finer patterns on a photomask.

[0020] Photomasks used in EUV lithography generally have a structure in which a reflective film that reflects extreme ultraviolet light, a protective film for protecting the reflective film, and a light-absorbing film that absorbs extreme ultraviolet light are formed in this order on a substrate such as a glass substrate. The reflective film is a multilayer reflective film in which low-refractive index layers and high-refractive index layers are alternately stacked to increase the reflectivity when extreme ultraviolet light is irradiated onto the surface of the reflective film. Typically, a molybdenum (Mo) layer is used as the low-refractive index layer of the multilayer reflective film, and a silicon (Si) layer is used as the high-refractive index layer. A ruthenium (Ru) film is typically used as the protective film. Meanwhile, the light-absorbing film is made of a material with a high absorption coefficient for EUV light, specifically, a material containing, for example, chromium (Cr) or tantalum (Ta) as its main component.

[0021] A typical method for producing a reflective photomask by patterning a light-absorbing film from a reflective photomask blank having a substrate on which a reflective film that reflects light in the extreme ultraviolet region, a protective film for protecting the reflective film, and a light-absorbing film that absorbs light in the extreme ultraviolet region are formed in this order is as follows: First, a resist film is formed on the light-absorbing film, and a pattern is written on this resist film using light or an electron beam and developed to form a resist pattern. Next, a pattern is formed on the light-absorbing film, and then the resist pattern is removed.

[0022] In the reflective photomasks required for EUV lithography, the assist patterns of the line patterns, which support the resolution of the main pattern, become even smaller as the main pattern becomes finer, and the line width of the assist patterns needs to be reduced to around 30 nm, especially around 25 nm. Therefore, compared to phase-shift mask blanks, reflective photomask blanks require even thinner resist films.

[0023] In order to form an assist pattern of a line pattern of about 30 nm, particularly about 25 nm, in a reflective photomask, the thickness of the resist film needs to be 80 nm or less. For example, when a pattern (circuit pattern) of a light-absorbing film containing tantalum as its main component is formed by fluorine-based dry etching using the resist pattern as an etching mask, fluorine-based dry etching is anisotropic etching dominated by physical components, and the etching rate for the resist pattern is relatively fast. Therefore, if the resist pattern is too thin, the resist pattern will disappear during dry etching of the light-absorbing film, resulting in the formation of pinhole defects in the light-absorbing film, making it impossible to manufacture a normal reflective photomask.

[0024] To prevent pinhole defects, the resist film must be thickened. However, the thicker the resist film, the higher the aspect ratio of the resist pattern required to form a finer assist pattern. Therefore, the resist film may collapse due to impact from the developer or pure water during the rinsing process during the development process, making it impossible to achieve the desired resolution.

[0025] For example, International Publication No. 2012 / 105508 (Patent Document 1) describes a reflective mask blank for EUV lithography, in which a layer that reflects EUV light, an absorber layer that absorbs EUV light, and a hard mask layer are formed in this order on a substrate. In this case, the absorber layer is a layer mainly composed of at least one of tantalum (Ta) and palladium (Pd), and the hard mask layer is a layer containing chromium (Cr), nitrogen (N) or oxygen (O), and hydrogen (H), with a total content of Cr and N or Cr and O of 85 to 99.9 at % and a H content of 0.1 to 15 at %, thereby reducing the surface roughness of the hard mask layer, providing a sufficiently high etching selectivity under etching conditions for the absorber layer, and making the crystalline state amorphous, thereby enabling a sufficiently low surface roughness. As a result, a high-resolution pattern can be obtained without increasing the line edge roughness of the hard mask layer pattern or the absorber layer pattern formed using the hard mask layer pattern.

[0026] Furthermore, WO 2012 / 105508 (Patent Document 1) describes the procedure for forming a pattern on a reflective mask blank for EUV lithography as follows: First, a resist film is formed on the hard mask layer of the EUV mask blank, and a pattern is formed on the resist film using an electron beam lithography machine. Next, using the patterned resist film as a mask, etching is performed by a chlorine-based gas process to form a pattern on the hard mask layer. Next, using the patterned hard mask layer as a mask, etching is performed by a fluorine-based gas process to form a pattern on the absorber layer. Next, etching is performed by a chlorine-based gas process to remove the hard mask layer. [Prior art documents] [Patent documents]

[0027] [Patent Document 1] International Publication No. 2012 / 105508 Summary of the Invention [Problem to be solved by the invention]

[0028] In the method described in International Publication No. 2012 / 105508 (Patent Document 1), for example, a CrNH film or CrOH film is used as a hard mask layer, and a tantalum-containing film is used as an absorber layer, and the absorber layer is patterned by fluorine-based dry etching. In this case, films formed from chromium-containing materials (CrNH film and CrOH film) have high resistance to fluorine-based dry etching and therefore have a slow etching rate, while films containing tantalum as a primary component have low resistance to fluorine-based dry etching and therefore have a fast etching rate, allowing for a thin hard mask layer. On the other hand, tantalum-containing films are patterned by chlorine-based dry etching, and a thinner hard mask layer reduces the amount of resist film lost during dry etching, allowing for a thinner resist film formed on the hard mask layer. As a result, the aspect ratio of the resist pattern is reduced, and the impact of developer impact or pure water impact during the rinsing process during the development step of resist pattern formation is reduced, allowing for the formation of a good assist pattern using the hard mask layer.

[0029] However, as mentioned above, when dry etching a hard mask layer made of a material containing chromium using a chlorine-based gas, in addition to the clear time required for the hard mask layer made of a material containing chromium to disappear, overetching of 100 to 300% of the clear time is required. In this case, the thickness of the resist film cannot be reduced to 80 nm or less.

[0030] Another factor that hinders the formation of a good assist pattern is a problem caused by a film formed from a material containing chromium. When a resist film is formed on a film formed from a material containing chromium, if particles are generated on the surface or inside of the resist film, using the resist film as is can lead to defects in the phase shift mask or reflective photomask. Therefore, it is common practice to first remove the resist film from which particles have been generated by cleaning, and then reapply resist to form a resist film.

[0031] A typical resist film is stripped and cleaned using a mixture of sulfuric acid and hydrogen peroxide (SPM). After stripping the resist film using this mixture, the surface of the chromium-containing film is acidic, and then rinsed with alkaline ammonia-added water (ammonia-added hydrogen peroxide (APM)). However, sulfuric acid typically corrodes the surface of the chromium-containing film, and the sulfuric acid cannot be completely removed from the surface of the chromium-containing film that has been corroded by sulfuric acid, resulting in residual sulfate ions remaining on the surface of the chromium-containing film. Residual sulfate ions on the surface of the chromium-containing film can impair the adhesion between the chromium-containing film and a subsequently formed resist film. Therefore, resist patterns, particularly line patterns such as assist patterns, are prone to collapse due to impacts from the developer or pure water during the rinsing process during the development process of resist pattern formation. As a result, the line patterns, such as assist patterns, cannot be formed satisfactorily. Therefore, the film that comes into contact with the resist film is required to have good adhesion to the resist film and not to deteriorate in adhesion to the resist film even when it comes into contact with a mixture of sulfuric acid and hydrogen peroxide solution.

[0032] In the method described in the aforementioned International Publication No. 2012 / 105508 (Patent Document 1), a pattern of a hard mask layer, which is a film formed of a material containing chromium, is formed from a reflective mask blank for EUV lithography in which a layer that reflects EUV light, an absorption layer that absorbs EUV light, and a hard mask layer are formed in that order on a substrate.When forming the pattern of the hard mask layer, a resist film is formed on the hard mask layer.In this case, too, stripping the resist film using a mixture of sulfuric acid and hydrogen peroxide solution results in a deterioration in adhesion between the hard mask layer and the resist film.

[0033] The present invention has been made to solve the above-mentioned problems, and provides a method for manufacturing a reflective photomask from a reflective photomask blank that includes, on a substrate, a multilayer reflective film that reflects exposure light in the extreme ultraviolet region, a protective film for protecting the multilayer reflective film, and a light absorbing film that absorbs exposure light, wherein even if a mixed solution of sulfuric acid and hydrogen peroxide is used to strip the resist film, the adhesion of the reformed resist film is unlikely to decrease. Ku It is possible to form an assist pattern with a line width of about 30 nm, particularly about 25 nm. Ru, Specifically, even if the resist film is thin, for example, a resist film having a thickness of 80 nm or less, an assist pattern with a line width of about 30 nm, particularly about 25 nm, can be formed satisfactorily. 、 Reflective Photomask Blank Ku or How to manufacture reflective photomask blanks from The law To provide the eyes The target. [Means for solving the problem]

[0034] As mentioned above, conventional reflective photomask blanks had the problem that when a resist film was 80 nm or less in thickness, no resist film remained after dry etching, making it impossible to form a fine assist pattern well, and also had the problem that the adhesion of the resist film deteriorated due to the mixed solution of sulfuric acid and hydrogen peroxide solution.

[0035] Therefore, the present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that a reflective photomask blank includes a multilayer reflective film that reflects exposure light in the extreme ultraviolet region, a protective film for protecting the multilayer reflective film, and a light absorbing film that absorbs exposure light, and the hard mask film is provided on the light absorbing film in contact with the light absorbing film, and functions as a hard mask when patterning the light absorbing film by dry etching, and the hard mask film is a multilayer including a first layer formed of a material that contains silicon and does not contain chromium, and a second layer formed of a material that contains chromium and does not contain silicon, the first layer and the second layer being provided on the side farthest from the substrate, and in particular, the first layer and the second layer being formed to have a predetermined composition and / or a predetermined thickness. Then, the resist film is re-formed in contact with the hard mask film of the reflective photomask blank. The present inventors have found that the above-mentioned problems can be solved by doing so, and have thus completed the present invention.

[0036] Therefore, the present invention provides the following method for manufacturing a reflective photomask. 1. A substrate; a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region; a protective film formed on the multilayer reflective film for protecting the multilayer reflective film; formed on the protective film, Contains tantalum and has a thickness of 50 nm or more and 74 nm or less; a light absorbing film that absorbs the exposure light; a hard mask film formed on and in contact with the light absorbing film, the hard mask film functioning as a hard mask when patterning the light absorbing film by dry etching; Equipped with The hard mask film includes a first layer and a second layer provided on the side farthest from the substrate. Consists of It consists of multiple layers, The first layer is silicon and oxygen , the second layer is formed of a material that does not contain chromium, and nitrogen and a method for producing a reflective photomask having a pattern of the light absorbing film from a reflective photomask blank formed of a material containing no silicon, the method comprising: the material of the first layer has a silicon content of 34 atomic % or more and 56 atomic % or less, and a thickness of the first layer is 2 nm or more and 12 nm or less; the material of the second layer has a chromium content of 33 atomic % or more and 85 atomic % or less, a nitrogen content of 12 atomic % or more and 49 atomic % or less, and a thickness of the second layer is 10 nm or more and 16 nm or less; (A) forming a resist film in contact with the side of the hard mask film that is away from the substrate; (A1) stripping the resist film with a mixed solution of sulfuric acid and hydrogen peroxide; (A2) after stripping the resist film in the step (A1), re-forming a resist film in contact with the side of the hard mask film from which the resist film has been stripped, the side facing away from the substrate; (B) patterning the resist film reformed in the (A2) step to form a resist pattern; (C) patterning the first layer by dry etching using a fluorine-based gas using the resist pattern as an etching mask to form a pattern of the first layer; (D) removing the resist pattern; (E) patterning the second layer by dry etching using a chlorine-based gas using the pattern of the first layer as an etching mask to form a pattern of the second layer; (F) patterning the light absorbing film by dry etching using a fluorine-based gas using the pattern of the second layer as an etching mask; Includes line patterns with widths of 25 nm or less forming a pattern of the light absorbing film and simultaneously removing the pattern of the first layer; (G) removing the pattern of the second layer by dry etching using a chlorine-based gas; A method for manufacturing a reflective photomask, comprising: 2. A substrate; a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region; a protective film formed on the multilayer reflective film for protecting the multilayer reflective film; formed on the protective film, Contains tantalum and has a thickness of 50 nm or more and 74 nm or less; a light absorbing film that absorbs the exposure light; a hard mask film formed on and in contact with the light absorbing film, the hard mask film serving as a hard mask when patterning the light absorbing film by dry etching; a resist film formed on the hard mask film in contact with the hard mask film; Equipped with The hard mask film includes a first layer and a second layer provided on the side farthest from the substrate. Consists of It consists of multiple layers, The first layer is silicon and oxygen , the second layer is formed of a material that does not contain chromium, and nitrogen and a method for producing a reflective photomask having a pattern of the light absorbing film from a reflective photomask blank formed of a material containing no silicon, the method comprising: the material of the first layer has a silicon content of 34 atomic % or more and 56 atomic % or less, and a thickness of the first layer is 2 nm or more and 12 nm or less; the material of the second layer has a chromium content of 33 atomic % or more and 85 atomic % or less, a nitrogen content of 12 atomic % or more and 49 atomic % or less, and a thickness of the second layer is 10 nm or more and 16 nm or less; (A1) stripping the resist film with a mixed solution of sulfuric acid and hydrogen peroxide; (A2) after stripping the resist film in the step (A1), re-forming a resist film in contact with the side of the hard mask film from which the resist film has been stripped, the side facing away from the substrate; (B) patterning the resist film reformed in the (A2) step to form a resist pattern; (C) patterning the first layer by dry etching using a fluorine-based gas using the resist pattern as an etching mask to form a pattern of the first layer; (D) removing the resist pattern; (E) patterning the second layer by dry etching using a chlorine-based gas using the pattern of the first layer as an etching mask to form a pattern of the second layer; (F) patterning the light absorbing film by dry etching using a fluorine-based gas using the pattern of the second layer as an etching mask; Includes line patterns with widths of 25 nm or less forming a pattern of the light absorbing film and simultaneously removing the pattern of the first layer; (G) removing the pattern of the second layer by dry etching using a chlorine-based gas; A method for manufacturing a reflective photomask, comprising: 3. The thickness of the resist film is 58 nm or less 1 or 2 The manufacturing method described in 42. The manufacturing method described in 1 or 2, wherein the material of the second layer further contains oxygen, the oxygen content being 40 atomic % or less. 5 The material of the second layer further contains carbon, and the carbon content is 20 atomic % or less. 4 The manufacturing method described in [Effects of the Invention]

[0037] According to the present invention, even when a mixture of sulfuric acid and hydrogen peroxide solution is used to strip the resist film, the adhesion of the reformed resist film is not likely to decrease, and therefore the resist pattern for forming a fine assist pattern can be made less likely to collapse due to impact from the developer in the development step of resist pattern formation or impact from pure water during the rinsing process. Furthermore, according to the present invention, the thickness of the resist film can be reduced, and the aspect ratio of the resist pattern can be reduced, allowing for the successful formation of an assist pattern with a line width of approximately 30 nm, particularly approximately 25 nm. Therefore, high resolution can be obtained in the transfer pattern of a reflective photomask manufactured from the reflective photomask blank. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a first embodiment of a reflective photomask blank of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a second embodiment of the reflective photomask blank of the present invention. [Figure 3] 1 is a cross-sectional view showing an example of a reflective photomask of the present invention. [Figure 4] 1(A) to 1(G) are cross-sectional views illustrating the steps of producing a reflective photomask from the reflective photomask blank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be described in more detail below. A reflective photomask blank according to a first aspect of the present invention comprises a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region, a protective film formed on the multilayer reflective film to protect the multilayer reflective film, a light-absorbing film formed on the protective film and absorbing exposure light in the extreme ultraviolet region, and a hard mask film formed on and in contact with the light-absorbing film and functioning as a hard mask when patterning the light-absorbing film by dry etching. The hard mask film is a multilayer film (laminated film) including a first layer and a second layer provided on the side farthest from the substrate.

[0040] The reflective photomask blank of the present invention may further comprise a resist film. A reflective photomask blank of a second aspect of the present invention comprises a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region, a protective film formed on the multilayer reflective film for protecting the multilayer reflective film, a light-absorbing film formed on the protective film and absorbing exposure light in the extreme ultraviolet region, a hard mask film formed on and in contact with the light-absorbing film and functioning as a hard mask when patterning the light-absorbing film by dry etching, and a resist film formed on and in contact with the hard mask film. This hard mask film is a film (laminated film) composed of multiple layers including a first layer provided on the side farthest from the substrate and a second layer.

[0041] From the reflective photomask blanks of the first and second embodiments, it is possible to obtain a reflective photomask comprising, for example, a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light that is extreme ultraviolet region light, a protective film formed on the multilayer reflective film for protecting the multilayer reflective film, and a pattern (circuit pattern or photomask pattern) of a light absorbing film formed on the protective film and absorbing exposure light that is extreme ultraviolet region light.

[0042] The structures of the reflective photomask blank and reflective photomask of the present invention will be described below with reference to the drawings. In the description of the drawings, the same components are given the same reference numerals and their description may be omitted. Furthermore, the drawings may be enlarged for convenience, and the dimensional ratios of the components may not necessarily be the same as in reality.

[0043] 1 is a cross-sectional view showing an example of a first embodiment of a reflective photomask blank of the present invention. This reflective photomask blank 101 includes a substrate 1, a multilayer reflective film 2 formed on and in contact with the substrate 1 and reflecting exposure light in the extreme ultraviolet region, a protective film 3 formed on and in contact with the multilayer reflective film 2 for protecting the multilayer reflective film 2, a light-absorbing film 4 formed on and in contact with the protective film 3 for absorbing the exposure light, and a hard mask film 5 formed on and in contact with the light-absorbing film 4 and functioning as a hard mask when patterning the light-absorbing film 4 by dry etching. In this case, the hard mask film 5 is composed of two layers: a first layer 51 provided on the side farthest from the substrate, and a second layer 52 provided on the substrate 1 side of the first layer 51. In other words, this reflective photomask blank 101 has a multilayer reflective film 2, a protective film 3, a light absorbing film 4, a second layer 52 of the hard mask film 5, and a first layer 51 of the hard mask film 5 stacked in this order from the substrate 1 side.

[0044] 2 is a cross-sectional view showing an example of a second embodiment of the reflective photomask blank of the present invention. This reflective photomask blank 102 includes a substrate 1, a multilayer reflective film 2 formed on and in contact with the substrate 1 and reflecting exposure light in the extreme ultraviolet region, a protective film 3 formed on and in contact with the multilayer reflective film 2 for protecting the multilayer reflective film 2, a light-absorbing film 4 formed on and in contact with the protective film 3 and absorbing the exposure light, a hard mask film 5 formed on and in contact with the light-absorbing film 4 and functioning as a hard mask when patterning the light-absorbing film 4 by dry etching, and a resist film 6 formed on and in contact with the hard mask 5. In this case, the hard mask film 5 is composed of two layers: a first layer 51 provided on the side farthest from the substrate, and a second layer 52 provided on the side of the first layer 51 facing the substrate 1. In other words, in this reflective photomask blank 102, from the substrate 1 side, a multilayer reflective film 2, a protective film 3, a light absorbing film 4, a second layer 52 of the hard mask film 5, a first layer 51 of the hard mask film 5, and a resist film 6 are laminated in this order.

[0045] 3 is a cross-sectional view showing an example of a reflective photomask 200 of the present invention. This reflective photomask includes a substrate 1, a multilayer reflective film 2 formed on and in contact with the substrate 1 and reflecting exposure light in the extreme ultraviolet region, a protective film 3 formed on and in contact with the multilayer reflective film 2 for protecting the multilayer reflective film, and a light absorbing film pattern (circuit pattern or photomask pattern) 4a formed on and in contact with the protective film 3 and absorbing the exposure light. In other words, in this reflective photomask 200, the multilayer reflective film 2, the protective film 3, and the light absorbing film pattern 4a are laminated in this order from the substrate 1 side.

[0046] [substrate] There are no particular limitations on the type or size of the substrate, and the substrate of the reflective photomask blank and the reflective photomask may or may not be transparent at the exposure wavelength. For example, a glass substrate such as a quartz substrate can be used as the substrate. Furthermore, a substrate known as a 6025 substrate, which is 6 inches square and 0.25 inches thick as specified in the SEMI standard, is suitable as the substrate. In the SI unit system, a 6025 substrate is usually expressed as a substrate with a 152 mm square and a thickness of 6.35 mm.

[0047] [Multilayer reflective film] The multilayer reflective film is a film that reflects exposure light in the extreme ultraviolet region. The multilayer reflective film is preferably formed in contact with a substrate. This extreme ultraviolet region light is called EUV light, and the wavelength of EUV light is 13 to 14 nm, and EUV light is usually light with a wavelength of about 13.5 nm. The material constituting the multilayer reflective film is preferably a material that is resistant to dry etching (chlorine-based dry etching) using a chlorine-based gas (e.g., Cl2 gas only or a mixed gas of Cl2 gas and O2 gas) and can be removed by dry etching (fluorine-based dry etching) using a fluorine-based gas (e.g., CF4 gas or SF6 gas). Specific examples of materials constituting the multilayer reflective film include molybdenum (Mo) and silicon (Si). As the multilayer reflective film, a laminated film (Si / Mo laminated film) in which approximately 20 to 60 molybdenum (Mo) layers and silicon (Si) layers are alternately stacked is generally used. The thickness of the multilayer reflective film is preferably 200 nm or more, particularly 220 nm or more, and is preferably 340 nm or less, particularly 280 nm or less.

[0048] [Protective film] The protective film , manyThe protective film is a film for protecting the multilayer reflective film. The protective film is preferably formed in contact with the multilayer reflective film. The protective film is provided to protect the multilayer reflective film, for example, during cleaning in processing into a reflective photomask or during repair of the reflective photomask. In addition, the protective film preferably has the function of protecting the multilayer reflective film when the light-absorbing film is patterned by etching and preventing oxidation of the multilayer reflective film. The material constituting the protective film is preferably a material having etching properties different from those of the light-absorbing film, and specifically, a material having resistance to chlorine-based dry etching. Specific examples of materials constituting the protective film include materials containing ruthenium (Ru). The protective film may be a single-layer film or a multilayer film (for example, a film composed of 2 to 4 layers), or may be a film having a gradient composition. The thickness of the protective film is preferably 1 nm or more and 20 nm or less.

[0049] [Light-absorbing film] The light-absorbing film is a film that absorbs exposure light in the extreme ultraviolet region. The light-absorbing film is preferably formed in contact with the protective film. The light-absorbing film is preferably made of a material that is resistant to chlorine-based dry etching and can be removed by fluorine-based dry etching. The light-absorbing film is preferably made of a material containing tantalum (Ta). Specific examples of materials containing tantalum include elemental tantalum (Ta) and tantalum compounds containing tantalum (Ta) and one or more elements selected from oxygen (O), nitrogen (N), boron (B), etc. Examples of such materials include a material made of tantalum (Ta), a material made of tantalum and oxygen (TaO), a material made of tantalum and nitrogen (TaN), a material made of tantalum and boron (TaB), a material made of tantalum, oxygen, and nitrogen (TaON), a material made of tantalum, oxygen, and boron (TaOB), a material made of tantalum, nitrogen, and boron (TaNB), and a material made of tantalum, oxygen, nitrogen, and boron (TaONB). The light-absorbing film may be a single-layer film or a multilayer film (e.g., a film composed of 2 to 4 layers), or may have a gradient composition. The thickness of the light-absorbing film is preferably 30 nm or more, particularly 40 nm or more, and especially 50 nm or more, and is preferably 100 nm or less, particularly 80 nm or less, and especially 74 nm or less.

[0050] [Hard mask film] The hard mask film of the present invention is composed of multiple layers including a first layer provided on the side farthest from the substrate and a second layer provided on a side other than the side farthest from the substrate. The hard mask film is not limited to a two-layer structure, but may be composed of three or more layers, for example, three, four, or five layers. The second layer is preferably provided on the side closest to the substrate.

[0051] The first layer of the hard mask film is made of a material that contains silicon (Si) but does not contain chromium (Cr). The material of the first layer is resistant to chlorine-based dry etching and can be removed by fluorine-based dry etching. Due to these etching properties, the first layer functions as an etching mask when etching the second layer.

[0052] On the other hand, the second layer of the hard mask film is formed of a material containing chromium (Cr) but not silicon (Si). The material of the second layer is resistant to fluorine-based dry etching and removable by chlorine-based dry etching. Due to such etching properties, the second layer functions as an etching mask when etching the light absorbing film. It is preferable that the other layers constituting the hard mask film other than the first and second layers are formed of a material containing chromium (Cr) but not silicon (Si). The other layers may have the same or different constituent elements as the second layer. If the constituent elements of the other layers are the same as those of the second layer, it is preferable that the layer have a different ratio of the constituent elements. However, as long as the other layers are not in contact with the second layer, the ratio of the constituent elements may be the same as that of the second layer.

[0053] [First layer of hard mask film] The material of the first layer contains silicon but does not contain chromium. The first layer is the layer that comes into contact with the resist film, and is the layer that comes into contact with a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid / hydrogen peroxide, SPM) or ammonia-added water (ammonia-added hydrogen peroxide (APM)) during the stripping and cleaning of the resist film. The first layer also functions as an etching mask (hard mask) during the etching of the second layer.

[0054] The material of the first layer may contain, in addition to silicon, one or more elements selected from oxygen (O), nitrogen (N), and carbon (C), and is particularly preferably a material consisting of silicon and one or more elements selected from oxygen, nitrogen, and carbon. When the material of the first layer contains elements other than silicon, the silicon content is less than 100 atomic %, but preferably 65 atomic % or less, and particularly preferably 60 atomic % or less. The lower the silicon content, the higher the etching rate of the first layer in fluorine-based dry etching. On the other hand, the lower limit of the silicon content is usually 25 atomic % or more, and preferably 30 atomic % or more.

[0055] The material of the first layer preferably contains oxygen, and silicon oxide (SiO), which is made of silicon and oxygen, is particularly suitable. If the material of the first layer contains oxygen, the silicon content is preferably 25 atomic % or more, particularly 30 atomic % or more, and 65 atomic % or less, particularly 60 atomic % or less. On the other hand, the oxygen content is preferably 30 atomic % or more, particularly 38 atomic % or more, and 70 atomic % or less, particularly 68 atomic % or less.

[0056] The first layer is patterned by fluorine-based dry etching using a resist pattern formed on the first layer as an etching mask, and since the thinner the first layer, the shorter the etching time, the thickness of the first layer is preferably 16 nm or less, particularly 12 nm or less, and especially 10 nm or less. On the other hand, if the first layer is too thin, it will lose its function as an etching mask in etching the second layer and will also reduce the sensitivity of defect inspection of the hard mask film, so the thickness of the first layer is preferably 2 nm or more, particularly 4 nm or more.

[0057] The silicon-containing, chromium-free material is resistant to chlorine-based dry etching of the second layer, and the pattern of the first layer functions as an etching mask during etching of the second layer. Furthermore, because the first layer can be etched using fluorine-based dry etching, which does not require prolonged overetching, the thickness of the resist film used for etching the first layer can be reduced. In particular, a material containing oxygen in addition to silicon but not containing chromium, preferably a material containing each element in the aforementioned content ratio, more preferably a material with a composition having a relatively high oxygen content, exhibits high adhesion to the resist film and is less likely to dissolve in a mixture of sulfuric acid and hydrogen peroxide or ammonia-added water compared to a chromium-containing material, allowing stable maintenance of optical properties necessary for defect inspection, etc. Furthermore, since the material is less corroded by sulfuric acid than a chromium-containing material, adhesion to the resist film is less likely to deteriorate even when contacted with a mixture of sulfuric acid and hydrogen peroxide. For this reason, by making the side of the etching mask film farthest from the substrate such a first layer, even a line pattern such as a fine assist pattern is less likely to collapse due to impact from the developer in the development step of resist pattern formation or impact from pure water during the rinsing process, making it possible to form a good resist pattern and obtain high resolution.

[0058] In addition, since the material of the first layer is a material that can be removed by fluorine-based dry etching, the pattern of the first layer can be removed simultaneously with the formation of the pattern of the light-absorbing film by fluorine-based dry etching when forming the pattern of the light-absorbing film.

[0059] [Second layer of hard mask film] The second layer is made of a material that contains chromium but does not contain silicon, and functions as an etching mask (hard mask) for etching the light absorbing film.

[0060] The material of the second layer may contain, in addition to chromium, one or more elements selected from oxygen (O), nitrogen (N), and carbon (C), and is particularly preferably a material consisting of chromium and one or more elements selected from oxygen, nitrogen, and carbon. When the material of the second layer contains elements other than chromium, the chromium content is less than 100 atomic %, but preferably 90 atomic % or less, and particularly preferably 88 atomic % or less. The lower the chromium content, the higher the etching rate of the second layer in chlorine-based dry etching. On the other hand, the lower limit of the chromium content is usually 30 atomic % or more, and preferably 31 atomic % or more.

[0061] The material of the second layer preferably contains nitrogen, and chromium nitride (CrN), which is made of chromium and nitrogen, is particularly suitable. If the material of the second layer contains nitrogen, the chromium content is preferably 30 atomic % or more, particularly 31 atomic % or more, and 90 atomic % or less, particularly 88 atomic % or less. On the other hand, the nitrogen content is preferably 8 atomic % or more, particularly 10 atomic % or more, and 55 atomic % or less, particularly 52 atomic % or less.

[0062] Furthermore, the material of the second layer preferably contains oxygen as well as nitrogen, and chromium oxynitride (CrNO), which is composed of chromium, nitrogen, and oxygen, is particularly suitable. When the material of the second layer contains oxygen, the oxygen content is preferably 40 atomic % or less, and particularly 38 atomic % or less. Furthermore, although there is no particular lower limit for the oxygen content, it is preferably 2 atomic % or more, and particularly 20 atomic % or more. When the material of the second layer contains oxygen, the chromium content and nitrogen content are preferably within the ranges described above.

[0063] Furthermore, the material of the second layer may contain carbon in addition to nitrogen and oxygen. If carbon is contained, chromium nitride oxide carbide (CrNOC), which is composed of chromium, nitrogen, oxygen, and carbon, is preferred. If the material of the second layer contains carbon, the carbon content is preferably 20 atomic % or less, particularly 15 atomic % or less. Furthermore, the lower limit of the carbon content is not particularly limited, but is preferably 2 atomic % or more, particularly 5 atomic % or more. If the material of the second layer contains carbon, the chromium content, nitrogen content, and oxygen content are preferably within the ranges described above.

[0064] The second layer is patterned by chlorine-based dry etching using the pattern of the first layer formed adjacent to the second layer as an etching mask. However, the first layer also gradually thins as it is exposed to the chlorine-based dry etching. If the first layer disappears, pinhole defects will form in the second layer. When the light-absorbing film is dry-etched using the second layer as an etching mask, the plasma generated during etching of the light-absorbing film will reach the light-absorbing film through the pinhole defects, resulting in pinhole defects in the light-absorbing film. Therefore, a thin second layer is preferable to shorten the etching time. The thickness of the second layer is preferably 16 nm or less, particularly 10 nm or less. On the other hand, if the second layer is too thin, it will lose its function as an etching mask during etching of the light-absorbing film and the sensitivity of defect inspection of the hard mask film will decrease. Therefore, the thickness of the second layer is preferably 2 nm or more, particularly 4 nm or more.

[0065] The chromium-containing, silicon-free material is resistant to fluorine-based dry etching of the light-absorbing film, and the second layer pattern functions as an etching mask for etching the light-absorbing film. In particular, a silicon-free material containing chromium and nitrogen, nitrogen and oxygen, or nitrogen, oxygen, and carbon, preferably containing each element in the aforementioned content ratio, more preferably a material with a relatively high nitrogen content or a relatively high nitrogen content and oxygen content, exhibits a high etching rate and a short etching time. For these reasons, providing the etching mask film with the second layer together with the first layer allows for high resolution.

[0066] Since the material of the second layer is a material that can be removed by chlorine-based dry etching, if the light-absorbing film is formed from a material that is resistant to chlorine-based dry etching, the pattern of the second layer can be removed by chlorine-based dry etching after the light-absorbing film pattern is formed, leaving the light-absorbing film pattern.

[0067] [Resist film] The resist film may be an electron beam resist that is written by an electron beam or a photoresist that is written by light, but a chemically amplified resist is preferred. The chemically amplified resist may be either positive or negative, and may, for example, contain a base resin such as a hydroxystyrene-based resin or a (meth)acrylic acid-based resin, an acid generator, and, if necessary, may contain a crosslinker, a quencher, a surfactant, or the like.

[0068] The hard mask film of the present invention has a first layer provided on the side farthest from the substrate, and the thickness of the resist film formed on this first layer can be thin, as described above. The thickness of the resist film is preferably 100 nm or less from the viewpoint of preventing the resist pattern for forming a fine assist pattern from collapsing due to impact with the developer or impact with pure water during the rinsing process in the development step of resist pattern formation. Furthermore, from the viewpoint of successfully forming a line pattern such as an assist pattern having a width of about 30 nm, particularly about 25 nm, the thickness is preferably 80 nm or less, particularly 60 nm or less. The lower limit of the resist film thickness is a thickness that functions as an etching mask in etching the first layer, and is sufficient as long as the resist pattern remains over the entire pattern of the first layer after etching. While not particularly limited, the lower limit is preferably 30 nm or more, particularly 40 nm or more.

[0069] The multilayer reflective film, protective film, light absorbing film, and hard mask film including the first and second layers of the present invention are preferably formed by sputtering, although the formation is not particularly limited, as this method is easy to control and allows for the formation of films with desired properties. The sputtering method may be DC sputtering, RF sputtering, or the like, and is not particularly limited.

[0070] When forming a laminated film of a molybdenum layer and a silicon layer as a multilayer reflective film, a molybdenum target and a silicon target can be used as sputtering targets. When forming a film made of a material containing ruthenium as a protective film, a ruthenium target can be used as a sputtering target. When forming a film made of a material containing tantalum as a light absorbing film, a tantalum target can be used as a sputtering target. When forming a first layer of a hard mask film made of a material containing silicon but not containing chromium, and a second layer of a hard mask film made of a material containing chromium but not containing silicon, a silicon target and a chromium target can be used as sputtering targets, respectively.

[0071] The power input to the sputtering target can be set appropriately depending on the size of the sputtering target, cooling efficiency, ease of control of film formation, etc., and is usually 50 to 3000 W / cm as the power per area of ​​the sputtering surface of the sputtering target. 2 In addition, rare gases such as helium gas (He gas), neon gas (Ne gas), and argon gas (Ar gas) are used as sputtering gases, and each film and the layers contained in the film are 、 When the film is formed using only the target element, only a rare gas may be used as the sputtering gas.

[0072] When each film and layer contained in the film is formed from a material containing oxygen, nitrogen, or carbon, sputtering is preferably reactive sputtering. Sputtering gases used in reactive sputtering include a rare gas such as helium gas (He gas), neon gas (Ne gas), or argon gas (Ar gas), and a reactive gas. For example, when forming a film from a material containing oxygen, oxygen gas (O gas) can be used as the reactive gas, and when forming a film from a material containing nitrogen, nitrogen gas (N gas) can be used as the reactive gas. When forming a film from a material containing both nitrogen and oxygen, the reactive gas can be appropriately selected from oxygen gas (O gas), nitrogen gas (N gas), and nitrogen oxide gases such as nitric oxide gas (NO gas), nitrogen dioxide gas (NO gas), and nitrous oxide gas (NO gas). When forming the film using a material containing carbon, a carbon-containing gas such as methane gas (CH4), carbon monoxide gas (CO gas), or carbon dioxide gas (CO2 gas) can be used as the reactive gas. When forming the film using a material containing oxygen, nitrogen, and carbon, for example, oxygen gas (O2 gas), nitrogen gas (N2 gas), and carbon dioxide gas (CO2) can be used simultaneously as the reactive gas.

[0073] The pressure during the formation of each film and layer contained in the film may be appropriately set in consideration of film stress, chemical resistance, cleaning resistance, etc., and is usually 0.01 Pa or more, particularly 0.03 Pa or more, and 1 Pa or less, particularly 0.3 Pa or less, to improve chemical resistance. The flow rate of each gas may be appropriately set to obtain the desired composition, and is usually 0.1 to 100 sccm.

[0074] In the manufacturing process of a reflective photomask blank, before forming a resist film, the substrate or the substrate and the film formed on the substrate may be subjected to a heat treatment. The heat treatment method may be infrared heating, resistance heating, or the like, and the treatment conditions are not particularly limited. The heat treatment may be carried out, for example, in an oxygen-containing gas atmosphere. The concentration of the oxygen-containing gas is not particularly limited, and in the case of oxygen gas (O2 gas), for example, it may be 1 to 100% by volume. The heat treatment temperature is preferably 200°C or higher, and particularly 400°C or higher.

[0075] Furthermore, in the manufacturing process of a reflective photomask blank, before forming a resist film, a film formed on a substrate, particularly a hard mask film, may be subjected to ozone treatment or plasma treatment, and the treatment conditions are not particularly limited. Either treatment can be performed for the purpose of increasing the oxygen concentration in the surface portion of the film, and in such a case, the treatment conditions may be appropriately adjusted to achieve a predetermined oxygen concentration. Note that when forming a film by sputtering, the oxygen concentration in the surface portion of the film can also be increased by adjusting the ratio of the rare gas in the sputtering gas to an oxygen-containing gas (oxidizing gas) such as oxygen gas (O gas), carbon monoxide gas (CO gas), or carbon dioxide gas (CO gas).

[0076] Furthermore, in the manufacturing process of a reflective photomask blank, a cleaning treatment may be performed before forming a resist film to remove defects present on the surface of the substrate or the film formed on the substrate. Cleaning can be performed using one or both of ultrapure water and functional water, which is ultrapure water containing ozone gas, hydrogen gas, etc. Furthermore, after cleaning with ultrapure water containing a surfactant, further cleaning may be performed using one or both of ultrapure water and functional water. Cleaning can be performed while irradiating with ultrasonic waves as necessary, and UV light irradiation can also be combined.

[0077] The method for forming the resist film (applying the resist) is not particularly limited, and known methods can be applied.

[0078] Next, a method for producing a reflective photomask from the reflective photomask blank of the present invention will be described with reference to the drawings. When producing a reflective photomask from the reflective photomask blank of the present invention, a method can be applied in which a resist pattern is formed from a resist film, and using the resist pattern as an etching mask, dry etching using a fluorine-based gas (fluorine-based dry etching) or dry etching using a chlorine-based gas (chlorine-based dry etching) is applied to the underlying film or layer depending on the material of the film or layer to form the pattern, and the pattern is then removed as appropriate. In addition, in the production of a reflective photomask, the resist film and resist pattern can be removed with sulfuric acid / hydrogen peroxide.

[0079] 4A and 4B are cross-sectional views illustrating the steps of producing a reflective photomask from the reflective photomask blank of the present invention. First, as shown in Fig. 4A, a resist film 6 is formed in contact with the side of the hard mask film 5 of the reflective photomask blank 101 of the first embodiment that faces away from the substrate 1 (i.e., in contact with the first layer 51) (step (A)). Here, the resist film 6 can be inspected, and if the resist film 6 has defects such as particles, the resist film 6 can be peeled off and then reformed.

[0080] Next, as shown in FIG. 4(B), the resist film 6 is patterned to form a resist pattern 6a (step (B)).

[0081] Next, as shown in FIG. 4(C), the first layer 51 is patterned by dry etching using a fluorine-based gas, using the resist pattern 6a as an etching mask, to form a first layer pattern 51a (step (C)).

[0082] Next, as shown in FIG. 4(D), the resist pattern 6a is removed (step (D)).

[0083] 4(E), the second layer 52 is patterned by dry etching using a chlorine-based gas using the first layer pattern 51a as an etching mask to form a second layer pattern 52a (step (E)). This forms a hard mask film pattern 5a including the first layer pattern 51a and the second layer pattern 52a.

[0084] 4(F), using the second layer pattern 52a as an etching mask, the light absorbing film 4 is patterned by dry etching using a fluorine-based gas to form a light absorbing film pattern 4a, and at the same time, the first layer pattern 51a is removed (step (F)). Here, the first layer pattern 51a formed of a material containing silicon but not chromium is removed by the fluorine-based dry etching, but the second layer pattern 52a formed of a material containing chromium but not silicon is resistant to the fluorine-based dry etching and therefore functions as an etching mask, remaining on the light absorbing film pattern 4a even after the dry etching.

[0085] Next, as shown in FIG. 4(G), the second layer pattern 52a is removed by dry etching using a chlorine-based gas (step (G)).

[0086] When a reflective photomask is manufactured from the reflective photomask blank of the second aspect of the present invention, since a resist film has already been formed, step (A) can be omitted and steps (B) to (G) can be carried out. Furthermore, before carrying out steps (B) to (G), the resist film 6 can be inspected, and if there are defects such as particles in the resist film 6, the resist film 6 can be peeled off and then reformed.

[0087] By using such a method, a thin resist film, for example, 80 nm or less, is formed on a reflective photomask blank, or a light-absorbing film is patterned from a reflective photomask blank on which a thin resist film, for example, 80 nm or less, has been formed, to obtain a reflective photomask on which a light-absorbing film pattern including a line pattern such as an assist pattern has been formed, which is satisfactory even if the line width is 30 nm or less (30 nm or less), particularly 25 nm or less (25 nm or less). In the present invention, the lower limit of the width of the line pattern such as an assist pattern formed in the light-absorbing film pattern of the reflective photomask is usually 10 nm or more. [Example]

[0088] EXAMPLES The present invention will be specifically explained below by showing examples and comparative examples, but the present invention is not limited to the following examples.

[0089] [Example 1] A reflective multilayer film, a protective film, a light-absorbing film, and a hard mask film consisting of a first layer and a second layer were laminated in this order on a quartz substrate measuring 152 mm square and approximately 6 mm thick, to produce a reflective photomask blank (reflective photomask blank of the first embodiment) as shown in FIG. 1 .

[0090] First, a molybdenum target and a silicon target were used as the targets, and argon gas was used as the sputtering gas. The power applied to the targets was adjusted, and the flow rate of the sputtering gas was also adjusted. Sputtering with the molybdenum target and sputtering with the silicon target were alternately performed to form a multilayer reflective film (thickness 280 nm) on a quartz substrate, which was an alternating laminate of molybdenum (Mo) and silicon (Si) layers with a reflectivity of 67% for light with a wavelength of 13.5 nm.

[0091] Next, using ruthenium as the target and argon gas as the sputtering gas, sputtering was performed by adjusting the power applied to the target and the flow rate of the sputtering gas to form a ruthenium (Ru) film (thickness 4 nm) on the multilayer reflective film as a protective film made of a material containing ruthenium.

[0092] Next, a tantalum target was used as the target, and argon gas and nitrogen gas were used as the sputtering gas. The power applied to the target was adjusted, and the flow rate of the sputtering gas was also adjusted to perform sputtering, thereby forming a tantalum nitride (TaN) film (thickness 64 nm) on the protective film as a light-absorbing film made of a material containing tantalum.

[0093] Next, a chromium target was used as the target, and argon gas, nitrogen gas, and oxygen gas were used as the sputtering gas. The power applied to the target was adjusted, and the flow rate of the sputtering gas was also adjusted to perform sputtering. A chromium nitride oxide (CrNO) layer was then formed on the light absorbing film as the second layer of the hard mask film, which was made of a material containing chromium but not silicon.

[0094] Furthermore, sputtering was performed using a silicon target and argon and oxygen gases as sputtering gases, adjusting the power applied to the target and the flow rate of the sputtering gas to form a silicon oxide (SiO) layer on the second layer as the first layer of the hard mask film formed from a material containing silicon but not containing chromium, thereby obtaining a reflective photomask blank. The compositions and thicknesses of the first and second layers are shown in Table 1. The compositions were measured using an X-ray photoelectron spectrometer, and the thicknesses were measured using an X-ray diffractometer (the same applies below).

[0095] [Example 2] Except for changing the ratio of silicon to oxygen in the first layer, a reflective photomask blank was obtained in the same manner as in Example 1. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0096] [Example 3] Except for changing the thicknesses of the first and second layers, a reflective photomask blank was obtained in the same manner as in Example 1. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0097] [Example 4] A reflective photomask blank was obtained in the same manner as in Example 3, except for the following changes in the formation of the second layer. For the second layer, a chromium nitride (CrN) layer was formed by sputtering using a chromium target as the target and argon gas and nitrogen gas as the sputtering gas, while adjusting the power applied to the target and the flow rate of the sputtering gas. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0098] [Example 5] Except for changing the thickness of the first layer and the ratio of chromium, nitrogen, and oxygen in the second layer, a reflective photomask blank was obtained in the same manner as in Example 1. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0099] [Example 6] Except for changing the thicknesses of the first and second layers, a reflective photomask blank was obtained in the same manner as in Example 2. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0100] [Example 7] A reflective photomask blank was obtained in the same manner as in Example 5, except for the following changes in the formation of the second layer. For the second layer, a chromium nitride oxycarbide (CrNOC) layer was formed by sputtering using a chromium target as the target and argon, nitrogen, and carbon dioxide gases as the sputtering gases, while adjusting the power applied to the target and the flow rate of the sputtering gas. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0101] [Example 8] Except for changing the thickness of the first layer, a reflective photomask blank was obtained in the same manner as in Example 1. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0102] [Example 9] Except for changing the silicon to oxygen ratio and thickness of the first layer, a reflective photomask blank was obtained in the same manner as in Example 1. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0103] [Example 10] By changing the ratio of silicon to oxygen and the thickness of the first layer and the ratio of chromium to nitrogen and the thickness of the second layer, reflective photomask blanks were obtained in the same manner as in Example 4. The compositions and thicknesses of the first and second layers are shown in Table 1.

[0104] [Comparative Example 1] A reflective photomask blank was obtained in the same manner as in Example 5, except that a hard mask film consisting only of a layer formed of a material containing chromium but not silicon (corresponding to a hard mask film consisting only of the second layer) was formed on the light-absorbing film. The composition and thickness of the hard mask film are shown in Table 1.

[0105] [Table 1]

[0106] [Clear time of fluorine-based dry etching of the first layer] The reflective photomask blanks obtained in Examples 1 to 10 were used to measure the time (clear time) until the first layer disappeared by fluorine-based dry etching. The clear time of fluorine-based dry etching was measured by performing dry etching on the first layer under the following conditions (condition 1), and the time until the end point was detected (time to endpoint). The results are shown in Table 2.

[0107] <Conditions for fluorine-based dry etching of the first layer (Condition 1)> Equipment: ICP (Inductively Coupled Plasma) method Gas: SF6 gas + O2 gas + He gas Gas pressure: 5.0 mTorr (0.66 Pa) ICP power: 400W

[0108] [Clear time for chlorine-based dry etching of the second layer] For the reflective photomask blanks obtained in Examples 1 to 10 and Comparative Example 1, the time required for the second layer to disappear (clear time) was measured by chlorine-based dry etching after measuring the clear time of the first layer by fluorine-based dry etching. The clear time of chlorine-based dry etching was measured by dry etching the second layer under the following conditions (condition 2), and the time required for the end point to be detected (time to endpoint). The results are shown in Table 2.

[0109] <Conditions for chlorine-based dry etching of the second layer (Condition 2)> Equipment: ICP (Inductively Coupled Plasma) method Gas: Cl2 gas + O2 gas Gas pressure: 3.0 mTorr (0.40 Pa) ICP power: 350W

[0110] [Table 2]

[0111] [Resist film loss during fluorine-based dry etching of the first layer] Using the reflective photomask blanks obtained in Examples 1 to 10, the amount (thickness) of the resist film reduced by fluorine-based dry etching until the first layer disappeared was measured. First, a positive chemically amplified electron beam resist was spin-coated on the first layer to form a resist film with a thickness of 60 nm. Next, using an electron beam lithography system, a dose of 100 μC / cm was applied. 2 A total of 20 isolated line patterns with long sides of 100,000 nm and short sides of 60 nm were written using a thermal processing device. Next, a post-exposure bake (PEB) was performed at 115°C for 14 minutes. Development was then performed using a puddle development for 42 seconds to form a resist pattern. Next, using the resist pattern as an etching mask, fluorine-based dry etching was performed on the first layer under the aforementioned condition 1 with 20% overetching to form a first-layer pattern. The thickness of the resist pattern remaining on the first-layer pattern was then measured, and the thickness reduction was calculated. The results are shown in Table 3. The thickness of the resist pattern was measured using an atomic force microscope (AFM), with a measurement area of ​​a 200 nm × 200 nm square region (same below).

[0112] Furthermore, from the obtained reduction amount, the thickness of the resist film required for the resist pattern to remain at a thickness of 20 nm after 20% overetching as fluorine-based dry etching of the first layer was calculated. The results are shown in Table 3. This thickness is the minimum thickness of the resist film required in manufacturing a reflective photomask using the reflective photomask blanks of Examples 1 to 10, which will be described later. If the thickness of the resist pattern remaining after etching is too thin, the fluorine-based plasma will reach the first layer and cause pinhole defects, so here, the thickness of the resist pattern remaining after dry etching was set to 20 nm.。

[0113] [Reduction of the first layer during chlorine-based dry etching of the second layer] Using the reflective photomask blanks obtained in Examples 1 to 10, the amount (thickness) of the first layer reduced by chlorine-based dry etching until the second layer disappeared was measured. First, a positive chemically amplified electron beam resist was spin-coated on the first layer to form a resist film with a thickness of 60 nm. Next, using an electron beam lithography system, a dose of 100 μC / cm was applied. 2 A total of 20 isolated line patterns with long sides of 100,000 nm and short sides of 60 nm were written using a thermal processing device. Next, a heat treatment (PEB: Post Exposure Bake) was performed at 115°C for 14 minutes. Next, a development process was performed using a puddle developer for 42 seconds to form a resist pattern. Next, using the resist pattern as an etching mask, fluorine-based dry etching was performed on the first layer under the aforementioned Condition 1 with 20% overetching to form a first layer pattern. Next, the remaining resist pattern was removed by washing with sulfuric acid / hydrogen peroxide mixture (a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid:hydrogen peroxide = 3:1)). Next, using the first layer pattern as an etching mask, the second layer was subjected to chlorine-based dry etching under the above-mentioned Condition 2 with 300% over-etching to form a second layer pattern. Thereafter, the thickness of the first layer pattern remaining on the second layer pattern was measured, and the thickness reduction was calculated. The results are shown in Table 3. The thickness of the first layer was measured using an X-ray diffraction device. As a result, it was confirmed that the first layer was not completely lost during the chlorine-based dry etching of the second layer in all of the reflective photomask blanks obtained in Examples 1 to 10.

[0114] [Resist film loss during chlorine-based dry etching of the second layer] Using the reflective photomask blank obtained in Comparative Example 1, the amount (thickness) of the resist film reduced by chlorine-based dry etching until the second layer disappeared was measured. First, a positive chemically amplified electron beam resist was spin-coated on the second layer to form a resist film with a thickness of 60 nm. Next, using an electron beam lithography system, a dose of 100 μC / cm was applied. 2 A total of 20 isolated line patterns with long sides of 100,000 nm and short sides of 60 nm were written using a thermal processing device. Next, a post-exposure bake (PEB) was performed at 115°C for 14 minutes. Development was then performed using a puddle developer for 42 seconds to form a resist pattern. Next, using the resist pattern as an etching mask, chlorine-based dry etching was performed on the second layer under the aforementioned condition 2 with 300% overetching to form a second-layer pattern. The thickness of the resist pattern remaining on the second-layer pattern was then measured, and the thickness reduction was calculated. The results are shown in Table 3.

[0115] Furthermore, from the obtained reduction amount, the thickness of the resist film required for the resist pattern to remain at a thickness of 20 nm after 300% overetching as chlorine-based dry etching of the second layer was calculated. The results are shown in Table 3. This thickness is the minimum thickness of the resist film required in manufacturing a reflective photomask using the reflective photomask blank of Comparative Example 1, which will be described later. If the thickness of the resist pattern remaining after etching is too thin, the chlorine-based plasma will reach the second layer and cause pinhole defects, so here, the thickness of the resist pattern remaining after dry etching was set to 20 nm.

[0116] [Table 3]

[0117] [Examples 11 to 20] A positive chemically amplified electron beam resist was spin-coated onto the hard mask film (first layer) of the reflective photomask blank obtained in Examples 1 to 10 to form a resist film, thereby obtaining a reflective photomask blank having a resist film (a reflective photomask blank of the second embodiment) as shown in Figure 2. The thickness of this resist film was set to a thickness that would allow a 20 nm thick resist pattern to remain after the above-mentioned fluorine-based dry etching, and was 40 nm or more, which is the lower limit of the thickness at which a resist film can be formed with a stable thickness using the resist material used. The thicknesses of the resist films are shown in Table 4.

[0118] To evaluate the resolution limit of a fine pattern equivalent to the assist pattern of an isolated line pattern, a reflective photomask was fabricated using a reflective photomask blank having the resist film obtained. First, an electron beam lithography system was used to fabricate a reflective photomask using a dose of 100 μC / cm. 2 As test patterns equivalent to the assist patterns of the line patterns, a total of 200,000 isolated patterns with different short-side dimensions, each with a long side dimension of 80 nm and a short-side dimension varying in 1-nm increments from 20 nm to 60 nm, were printed. Next, a post-exposure bake (PEB) was performed at 110°C for 14 minutes using a heat treatment device. Development was then performed using a puddle development system for 45 seconds to form a resist pattern. Using the resulting resist pattern as an etching mask, the first layer was subjected to fluorine-based dry etching under the aforementioned condition 1 with 20% overetching to form a first-layer pattern. The remaining resist pattern was then removed by cleaning with a sulfuric acid / hydrogen peroxide mixture (a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid:hydrogen peroxide = 3:1)). Next, using the first-layer pattern as an etching mask, the second layer was subjected to chlorine-based dry etching under the aforementioned condition 2 with 300% overetching to form a second-layer pattern.

[0119] Next, using the pattern of the second layer as an etching mask, the light absorbing film was subjected to fluorine-based dry etching under the following conditions (condition 3), to form a pattern of the light absorbing film and simultaneously remove the pattern of the first layer.

[0120] <Fluorine-based dry etching conditions for light-absorbing film (Condition 3)> Equipment: ICP (Inductively Coupled Plasma) method Gas: SF6 gas + He gas Gas pressure: 4.0 mTorr (0.53 Pa) ICP power: 400W

[0121] Next, the pattern of the second layer was subjected to chlorine-based dry etching under the above-mentioned condition 2 with 50% overetching to remove the pattern of the second layer, thereby obtaining a reflective photomask.

[0122] Next, the resolution limit of the obtained photomask test pattern was evaluated using a visual inspection device. All isolated patterns were evaluated for pattern loss, pattern collapse, and pattern shape defects. Isolated patterns in which the visual inspection device detected either pattern loss, pattern collapse, or pattern shape defects were considered to be defective, and the smallest short side dimension in which there were no isolated patterns with detected defects was considered to be the resolution limit. The results are shown in Table 4.

[0123] Comparative Example 2 A reflective photomask blank was obtained by spin-coating a positive chemically amplified electron beam resist onto the hard mask film of the reflective photomask blank obtained in Comparative Example 1 to form a resist film. The thickness of this resist film was set to a thickness that would allow a 20 nm thick resist pattern to remain after the aforementioned chlorine-based dry etching, and to a thickness of 40 nm or more, which is the lower limit of the thickness at which a resist film can be formed with a stable thickness using the resist material used. The thickness of the resist film is shown in Table 4.

[0124] To evaluate the resolution limit of a fine pattern equivalent to the assist pattern of an isolated line pattern, a reflective photomask was manufactured using a reflective photomask blank having the obtained resist film. First, a resist pattern was formed using the same method as in the example. Next, using the obtained resist pattern as an etching mask, the hard mask film was subjected to chlorine-based dry etching under the above-mentioned Condition 2 with 300% overetching, thereby forming a hard mask film pattern. Next, the remaining resist pattern was removed by washing with sulfuric acid / hydrogen peroxide (a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid:hydrogen peroxide = 3:1)).

[0125] Next, using the pattern of the hard mask film as an etching mask, the light absorbing film was subjected to fluorine-based dry etching under the above-mentioned Condition 3 to form a pattern of the light absorbing film.

[0126] Next, the hard mask film pattern was subjected to chlorine-based dry etching under the above-mentioned Condition 2 with 50% overetching to remove the hard mask film pattern, thereby obtaining a reflective photomask. The resolution limit of the test pattern was evaluated using a visual inspection device in the same manner as in the example. The results are shown in Table 4.

[0127] [Examples 21 to 30, Comparative Example 3] The resist film formed on the hard mask film was washed with sulfuric acid / hydrogen peroxide and stripped, and then the resolution limit of a fine pattern corresponding to the assist pattern of an isolated line pattern when the resist was reformed was evaluated. The resist film formed on the hard mask film of the reflective photomask blank obtained in Examples 1 to 10 and Comparative Example 1 was once washed with sulfuric acid / hydrogen peroxide and stripped, and a resist film was again formed on the hard mask film in the same manner, and then a resist pattern was formed. Reflective photomasks were obtained in the same manner as in Examples 11 to 20 and Comparative Example 2, except that the resolution limit of the test pattern was evaluated using a visual inspection device in the same manner as in the Examples. The results are shown in Table 4.

[0128] [Table 4]

[0129] As shown in Table 4, the hard mask film of the reflective photomask blanks of Examples 1 to 10 has a first layer formed of a material containing silicon but not containing chromium on the side farthest from the substrate. In Examples 21 to 30, there is no effect from the sulfuric acid / hydrogen peroxide solution used to strip the resist film formed on the hard mask film, and the resolution limit does not change from the resolution limit of Examples 11 to 20. This is thought to be because the adhesion of the first layer of the hard mask film of the reflective photomask blanks of Examples 1 to 10 to the resist film is not reduced by cleaning with sulfuric acid / hydrogen peroxide solution. On the other hand, the hard mask film of the reflective photomask blank of Comparative Example 1 has a side farthest from the substrate formed of a material containing chromium but not containing silicon. In Comparative Example 3, there is an effect from the sulfuric acid / hydrogen peroxide solution used to strip the resist film formed on the hard mask film, and the resolution limit is worse than that of Comparative Example 2. This is thought to be because the adhesion of the hard mask film formed from a material containing chromium but not silicon to the resist film of the reflective photomask blank of Comparative Example 1 was reduced by cleaning with sulfuric acid / hydrogen peroxide.

[0130] In particular, it can be seen that the resist film can be made thinner and a particularly good resolution limit can be obtained in the reflective photomask blanks of Examples 1 to 7 compared to the reflective photomask blank of Comparative Example 1. This is thought to be because the thin resist film reduces the possibility of the resist pattern collapsing due to impact from the developer in the development step of resist pattern formation or impact from pure water during the rinsing process, even for patterns with narrow line widths.

[0131] Furthermore, the reason why the reflective photomask blanks of Examples 1 to 7 can have thinner resist films than the reflective photomask blanks of Examples 9 and 10 is thought to be because the silicon content of the first layer in Examples 1 to 7 is lower than the silicon content of the first layer in Examples 9 and 10. Furthermore, it can be seen that the reflective photomask blank of Example 8 has the same resist film thickness as the reflective photomask blank of Comparative Example 1, but achieves a better resolution limit than Comparative Example 1.

[0132] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has the same or substantially the same configuration as the technical idea of ​​the present invention and that provides the same or similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0133] 1 board 2 Multilayer reflective film 3 Protective film 4. Light-absorbing film 4a Light absorbing film pattern 5 Hard mask film 5a Hard mask film pattern 51 1st layer 51a 1st layer pattern 52 2nd layer 52a Second layer pattern 6. Resist film 6a Resist pattern 101, 102 Reflective photomask blanks 200 Reflective Photomask

Claims

1. A substrate; a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region; a protective film formed on the multilayer reflective film for protecting the multilayer reflective film; a light-absorbing film formed on the protective film, containing tantalum, having a thickness of 50 nm or more and 74 nm or less, and absorbing the exposure light; a hard mask film formed on and in contact with the light absorbing film, the hard mask film functioning as a hard mask when patterning the light absorbing film by dry etching; Equipped with the hard mask film is composed of multiple layers including a first layer provided on a side farthest from the substrate and a second layer, A method for manufacturing a reflective photomask having a pattern of the light absorbing film from a reflective photomask blank in which the first layer is formed of a material consisting of silicon and oxygen and not containing chromium, and the second layer is formed of a material containing chromium and nitrogen and not containing silicon, comprising: the material of the first layer has a silicon content of 34 atomic % or more and 56 atomic % or less, and a thickness of the first layer is 2 nm or more and 12 nm or less; the material of the second layer has a chromium content of 33 atomic % or more and 85 atomic % or less, a nitrogen content of 12 atomic % or more and 49 atomic % or less, and a thickness of the second layer is 10 nm or more and 16 nm or less; (A) forming a resist film in contact with a side of the hard mask film that is away from the substrate; (A1) stripping the resist film with a mixed solution of sulfuric acid and hydrogen peroxide; (A2) after stripping the resist film in the step (A1), re-forming a resist film in contact with the side of the hard mask film from which the resist film has been stripped, the side being away from the substrate; (B) patterning the resist film reformed in the (A2) step to form a resist pattern; (C) patterning the first layer by dry etching using a fluorine-based gas using the resist pattern as an etching mask to form a pattern of the first layer; (D) removing the resist pattern; (E) patterning the second layer by dry etching using a chlorine-based gas using the pattern of the first layer as an etching mask to form a pattern of the second layer; (F) patterning the light absorbing film by dry etching using a fluorine-based gas using the pattern of the second layer as an etching mask to form a pattern of the light absorbing film including a line pattern having a width of 25 nm or less, and simultaneously removing the pattern of the first layer; (G) removing the pattern of the second layer by dry etching using a chlorine-based gas; A method for manufacturing a reflective photomask, comprising:

2. A substrate; a multilayer reflective film formed on the substrate and reflecting exposure light in the extreme ultraviolet region; a protective film formed on the multilayer reflective film for protecting the multilayer reflective film; a light-absorbing film formed on the protective film, containing tantalum, having a thickness of 50 nm or more and 74 nm or less, and absorbing the exposure light; a hard mask film formed on and in contact with the light absorbing film, the hard mask film serving as a hard mask when patterning the light absorbing film by dry etching; a resist film formed on the hard mask film in contact with the hard mask film; Equipped with the hard mask film is composed of multiple layers including a first layer provided on a side farthest from the substrate and a second layer, A method for manufacturing a reflective photomask having a pattern of the light absorbing film from a reflective photomask blank in which the first layer is formed of a material consisting of silicon and oxygen and not containing chromium, and the second layer is formed of a material containing chromium and nitrogen and not containing silicon, comprising: the material of the first layer has a silicon content of 34 atomic % or more and 56 atomic % or less, and a thickness of the first layer is 2 nm or more and 12 nm or less; the material of the second layer has a chromium content of 33 atomic % or more and 85 atomic % or less, a nitrogen content of 12 atomic % or more and 49 atomic % or less, and a thickness of the second layer is 10 nm or more and 16 nm or less; (A1) stripping the resist film with a mixed solution of sulfuric acid and hydrogen peroxide; (A2) after stripping the resist film in the step (A1), re-forming a resist film in contact with the side of the hard mask film from which the resist film has been stripped, the side being away from the substrate; (B) patterning the resist film reformed in the (A2) step to form a resist pattern; (C) patterning the first layer by dry etching using a fluorine-based gas using the resist pattern as an etching mask to form a pattern of the first layer; (D) removing the resist pattern; (E) patterning the second layer by dry etching using a chlorine-based gas using the pattern of the first layer as an etching mask to form a pattern of the second layer; (F) patterning the light absorbing film by dry etching using a fluorine-based gas using the pattern of the second layer as an etching mask to form a pattern of the light absorbing film including a line pattern having a width of 25 nm or less, and simultaneously removing the pattern of the first layer; (G) removing the pattern of the second layer by dry etching using a chlorine-based gas; A method for manufacturing a reflective photomask, comprising:

3. 3. The method according to claim 1, wherein the resist film has a thickness of 58 nm or less.

4. 3. The manufacturing method according to claim 1, wherein the material of the second layer further contains oxygen, and the oxygen content is 40 atomic % or less.

5. 5. The method according to claim 4, wherein the material of the second layer further contains carbon, and the carbon content is 20 atomic % or less.

Images