Reflection-type mask blank and method for manufacturing reflection-type mask

Abstract

An absorption film of a reflective mask blank which is formed on a protective film and can be etched by ion beam etching or methanol etching is patterned by providing an etching prevention film in contact with both the protective film and the absorption film and a first hard mask film on the absorption film, and using the pattern of the first hard mask film as an etching mask. The absorber film is patterned by ion beam etching or methanol etching.

Description

Technical Field

[0001] The present invention relates to a reflective mask blank which is a material for a reflective mask used for manufacturing a semiconductor device such as an LSI, and a method for manufacturing a reflective mask from the reflective mask blank. Background Art

[0002] In the manufacturing process of semiconductor devices, photolithography technology is repeatedly used, in which a transfer mask is irradiated with exposure light, and the circuit pattern formed on the transfer mask is transferred to a semiconductor substrate (semiconductor wafer) through a reduced projection optical system. In the past, the mainstream wavelength of exposure light was 193nm using argon fluoride (ArF) excimer laser. By adopting a process called multi-patterning that combines the exposure process and the processing process multiple times, a pattern with a size smaller than the exposure wavelength is finally formed.

[0003] However, since it is necessary to form finer patterns under the continuous miniaturization of device patterns, extreme ultraviolet lithography technology using extreme ultraviolet (hereinafter referred to as "EUV") light having a wavelength shorter than that of ArF excimer laser as exposure light is used. EUV light is light having a wavelength of about 0.2 to 100 nm, in particular, light having a wavelength of about 13.5 nm. EUV light has very low transmittance to matter and cannot be used in previous transmissive projection optical systems or masks, so a reflective type optical element device is applied. Therefore, a reflective mask is also proposed as a mask for pattern transfer.

[0004] In a reflective mask, a multilayer reflective film that reflects EUV light is generally formed on one main surface of a low thermal expansion substrate made of glass, and further, a patterned absorption film that absorbs EUV light is formed on the multilayer reflective film. On the other hand, the material before the absorption film is patterned (including the material forming the resist film) is called a reflective mask blank, and is used as a reflective mask material. In a reflective mask blank, a multilayer reflective film that reflects EUV light is formed on one main surface of a low thermal expansion substrate made of glass, and further, an absorption film that absorbs EUV light is formed on the multilayer reflective film. The reflective mask blank has a basic structure including a multilayer reflective film and an absorption film.

[0005] As a multilayer reflective film, a Mo / Si multilayer reflective film in which molybdenum (Mo) layers and silicon (Si) layers are alternately stacked to ensure reflectivity to EUV light is generally used. In addition, as a material for an absorption film, a material containing tantalum (Ta) or the like as a main component having a relatively large extinction coefficient with respect to EUV light is used (Patent Document 1: JP-A 2002-246299). On the other hand, a back surface conductive film such as a metal film is formed on the other main surface of the substrate for electrostatic clamping when the reflective mask is held on an exposure device. As a back surface conductive film, a film mainly containing chromium (Cr) or tantalum (Ta) is used.

[0006] In addition, a protective film for protecting the multilayer reflective film is often formed between the multilayer reflective film and the absorption film. The protective film is formed to protect the multilayer reflective film from being exposed to an etching gas during etching for forming a mask pattern in the absorption film or from being exposed to a cleaning liquid during cleaning after the mask pattern is formed, and also to protect the multilayer reflective film from being damaged during pattern correction processing performed when detecting defects after the mask pattern is formed. As a material for the protective film, for example, ruthenium (Ru) is used (Patent Document 2: JP-A 2002-122981), and it has also been proposed to use a material obtained by adding niobium (Nb), rhodium (Rh), zirconium (Zr), etc. to ruthenium (Ru).

[0007] Reference List

[0008] Patent Document 1: JP-A 2002-246299

[0009] Patent Document 2: JP-A 2002-122981 Summary of the invention

[0010] In a reflective mask blank for EUV exposure, a material containing tantalum (Ta) is generally used for an absorption film. When forming a pattern of an absorption film including a material containing tantalum (Ta), dry etching using a chlorine-based gas or a fluorine-based gas is often used.

[0011] In order to reduce the shielding effect in the exposure using a reflective mask, a thinned absorption film is required to form a finer pattern of the absorption film as needed. However, thinning the absorption film using a material containing tantalum (Ta) is limited. Therefore, an absorption film composed of a material containing another metal is required. For the material that can thin the absorption film, it is necessary to use a material having a high extinction coefficient k compared to the material containing tantalum (Ta), and further a material having a low refractive index n compared to the material containing tantalum (Ta) in the case of forming the absorption film to act as a phase shift film.

[0012] However, among materials containing another metal, materials having a higher extinction coefficient k than materials containing tantalum (Ta) and materials having a lower refractive index n than materials containing tantalum (Ta) tend to be inferior in etching processability. In this case, it is difficult to form a pattern by dry etching using a chlorine-based gas or a fluorine-based gas used in forming a pattern of an absorption film composed of a material containing tantalum (Ta).

[0013] In order to form a pattern of the absorption film that is difficult to form by dry etching using a chlorine-based gas or a fluorine-based gas, other etching methods such as ion beam etching or methanol etching may be used. However, since these etching methods can etch the protective film formed below the absorption film (on the substrate side) and further etch the multilayer reflection film, after etching the absorption film, these etching methods damage the protective film and further damage the multilayer reflection film.

[0014] The present invention is proposed to solve the above-mentioned problems, and an object of the present invention is to provide a reflective mask blank, wherein, including a film formed below an absorbing film (on the substrate side), even when the absorbing film is composed of a material containing a metal that can be thinned, and even when etching with high processability other than dry etching using a chlorine-based gas or a fluorine-based gas is used for etching the absorbing film in absorbing film patterning, the film formed below the absorbing film (on the substrate side) is difficult to be damaged. In addition, another object of the present invention is to provide a method for manufacturing a reflective mask from the reflective mask blank.

[0015] The inventors have conducted in-depth research to solve the above problem. As a result, the inventors have found that the problem can be solved by forming the absorption film of the reflective mask blank using a material containing a metal that can thin the absorption film, and forming an etching stopper film between the absorption film and the protective film formed below the absorption film (on the substrate side) to protect the protective film to prevent etching from reaching the protective film during patterning of the absorption film; and further, the inventors have found that the absorption film can be processed and patterned by providing a hard mask film above the absorption film (on the side away from the substrate) and using the pattern of the hard mask film as an etching mask.

[0016] In one aspect, the present invention provides a reflective mask blank, which is a reflective mask material used in EUV lithography using EUV light as exposure light, comprising: a substrate; a multilayer reflective film formed on one main surface of the substrate to reflect the exposure light; a protective film formed on the multilayer reflective film; and an absorption film formed on the protective film to absorb the exposure light, wherein the reflective mask blank includes an etch stop film formed in contact with both the protective film and the absorption film and a first hard mask film formed on the absorption film.

[0017] Preferably, when the absorption film and the etching stopper film are ion-beam etched under the same conditions, the etching selectivity of the etching stopper film to the absorption film is less than 1.

[0018] Preferably, when the absorption film and the etching stopper film are subjected to methanol etching under the same conditions, the etching selectivity of the etching stopper film to the absorption film is less than 1.

[0019] Preferably, when the absorption film and the etching stopper film are dry-etched using a chlorine-based gas or a fluorine-based gas under the same conditions, the etching selectivity of the etching stopper film to the absorption film is greater than 1.

[0020] Preferably, when the first hard mask film and the absorption film are dry-etched using a chlorine-based gas or a fluorine-based gas under the same conditions, an etching selectivity of the absorption film to the first hard mask film is not more than 0.3.

[0021] Preferably, the reflective mask blank further includes a second hard mask film on the first hard mask film.

[0022] Preferably, the second hard mask film contains chromium (Cr).

[0023] On the other hand, the present invention provides a first method for manufacturing a reflective mask from a reflective mask blank, comprising the steps of: dry etching a first hard mask film using a chlorine-based gas or a fluorine-based gas; patterning an absorption film by ion beam etching or ion beam etching and methanol etching; and dry etching an etch stop film using a chlorine-based gas or a fluorine-based gas.

[0024] On the other hand, the present invention provides a second method for manufacturing a reflective mask from a reflective mask blank including a second hard mask film, comprising the following steps: dry etching the second hard mask film using a gas containing chlorine (Cl) and oxygen (O); dry etching the first hard mask film using a chlorine-based gas or a fluorine-based gas; patterning the absorption film by ion beam etching or ion beam etching and methanol etching; and dry etching the etch stop film using a chlorine-based gas or a fluorine-based gas.

[0025] On the other hand, the present invention provides a third method for manufacturing a reflective mask from a reflective mask blank, wherein the reflective mask blank includes: a substrate; a multilayer reflective film that reflects exposure light formed on one main surface of the substrate; a protective film formed on the multilayer reflective film; and an absorption film that absorbs exposure light formed by patterning the absorption film on the protective film, wherein, in the reflective mask blank, an etching stop film is provided so as to contact both the protective film and the absorption film, and a first hard mask film is provided on the absorption film, wherein the method includes patterning the absorption film by the following steps: forming a pattern of the first hard mask film by dry etching using a chlorine-based gas or a fluorine-based gas; patterning the absorption film by ion beam etching or ion beam etching and methanol etching using the pattern of the first hard mask film as an etching mask; and removing the etching stop film by dry etching using a chlorine-based gas or a fluorine-based gas.

[0026] Preferably, in the third manufacturing method, in the reflective mask blank, a second hard mask film is also provided on the first hard mask film; a pattern of the second hard mask film is formed by dry etching using a gas containing chlorine (Cl) and oxygen (O); and a pattern of the first hard mask film is formed using the pattern of the second hard mask film as an etching mask.

[0027] Preferably, in the third manufacturing method, an etching selectivity of the etching stopper film to the absorption film in ion beam etching is less than 1.

[0028] Preferably, in the third manufacturing method, an etching selectivity of the etching stopper film to the absorber film in methanol etching is less than 1.

[0029] Preferably, in the step of removing the etching stopper film, an etching selectivity of the etching stopper film to the absorption film is greater than 1 in dry etching using a chlorine-based gas or a fluorine-based gas.

[0030] Preferably, in the step of forming the pattern of the first hard mask film, an etching selectivity of the absorber film to the first hard mask film in dry etching using a chlorine-based gas or a fluorine-based gas is not more than 0.3.

[0031] Preferably, the absorption film contains a metal other than tantalum (Ta).

[0032] Preferably, the metal other than tantalum (Ta) is at least one metal selected from the group consisting of platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co) and zinc (Zn).

[0033] Preferably, the etch stopper film contains tantalum (Ta).

[0034] Preferably, the first hard mask film contains tantalum (Ta).

[0035] Preferably, the etch stopper film and the first hard mask film each contain tantalum (Ta) and nitrogen (N).

[0036] Preferably, the multilayer reflective film includes: a high refractive index layer composed of a material containing silicon (Si) and a low refractive index layer composed of a material containing molybdenum (Mo).

[0037] Preferably, the protective film contains ruthenium (Ru).

[0038] Advantageous Effects of the Invention

[0039] According to the present invention, a reflective mask blank including a thinner absorption film that can reduce the shielding effect can be provided. In addition, a reflective mask including a fine absorption film pattern can be provided by patterning an absorption film made of a material that can be thinned without damaging a protective film formed under the absorption film (on the substrate side). BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a cross-sectional view showing an example (first embodiment) of the reflective mask blank of the present invention.

[0042] Figure 2It is a cross-sectional view showing an example (second embodiment) of the reflective mask blank of the present invention.

[0043] Figure 3 It is a cross-sectional view showing an example of the reflective mask of the present invention. DETAILED DESCRIPTION

[0044] The reflective mask blank of the present invention includes a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate to reflect exposure light, a protective film formed on the multilayer reflective film, and an absorption film formed on the protective film to absorb exposure light. In addition, the reflective mask blank of the present invention includes an etching stopper film formed between the protective film and the absorption film. In addition, the reflective mask blank of the present invention includes a first hard mask film formed on the protective film.

[0045] The reflective mask blank of the present invention is suitable for a reflective mask material used in EUV lithography using EUV light as exposure light. The wavelength of EUV light used in EUV lithography using EUV light as exposure light is 13 to 14 nm, usually about 13.5 nm. The reflective mask blank and the reflective mask using EUV light as exposure light are also referred to as EUV mask blank and EUV mask, respectively.

[0046] Figure 1 The sectional view is a diagram showing an example (first embodiment) of a reflective mask blank of the present invention. The reflective mask blank 11 includes: a substrate 1; and on the substrate 1, a multilayer reflective film 2 formed in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, an etching stopper film 4 formed in contact with the protective film 3, an absorption film 5 formed in contact with the etching stopper film 4, and a first hard mask film 6 formed in contact with the absorption film 5.

[0047] In the case of EUV light exposure, the substrate preferably has low thermal expansion properties. For example, the substrate preferably comprises a thermal expansion coefficient within ±2×10 -8 / ℃, preferably within ±5×10 -9 / ℃ within the material. As a material, titanium dioxide doped quartz glass (SiO2-TiO2 glass) is exemplified. In addition, it is preferred to use a substrate with a very flat surface. The surface roughness of the main surface of the substrate is preferably not more than 0.5nm, more preferably not more than 0.2nm in RMS value. Such surface roughness can be obtained by polishing the substrate, etc. The substrate preferably has a main surface size of 152mm square and a thickness of 6.35mm. A substrate with this size is called a 6025 substrate, which has a main surface size of 6 inches square and a thickness of 0.25 inches.

[0048] The multilayer reflective film is a film that reflects the exposure light in the reflective mask. The multilayer reflective film is preferably formed in contact with one main surface of the substrate, but can be formed via another film, such as an underlying film on one main surface of the substrate. The multilayer reflective film includes a high refractive index layer having a relatively high refractive index relative to the exposure light and a low refractive index layer having a relatively low refractive index relative to the exposure light. The multilayer reflective film generally has a periodic stacked structure in which high refractive index layers and low refractive index layers are alternately stacked.

[0049] The high refractive index layer is preferably composed of a silicon-containing (Si) material. The high refractive index layer may contain at least one additive element selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H). In addition, the high refractive index layer may be configured as a multilayer, comprising a layer containing additive elements and a layer not containing additive elements. The thickness of the high refractive index layer is preferably not less than 3.5nm, more preferably not less than 4nm, and preferably not more than 4.9nm, more preferably not more than 4.4nm.

[0050] The low refractive index layer is preferably composed of a molybdenum (Mo)-containing material. The low refractive index layer may include a ruthenium (Ru)-containing material. The low refractive index layer may contain at least one additive element selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H). In addition, the low refractive index layer may be configured as a multilayer, comprising a layer containing additive elements and a layer not containing additive elements. The thickness of the low refractive index layer is preferably not less than 2.1 nm, more preferably not less than 2.6 nm, and preferably not more than 3.5 nm, more preferably not more than 3 nm.

[0051] The periodic stacked structure may include a high refractive index layer and a low refractive index layer, and may include at least one high refractive index layer and at least one low refractive index layer in one cycle. One cycle includes at least two layers and may be configured as, for example, a high refractive index layer and a low refractive index layer. In addition, one cycle may include at least two high refractive index layers (such as different composition ratios, or different compositions with and without added elements) that are different from each other, and may include at least two low refractive index layers (such as different composition ratios, or different compositions with and without added elements) that are different from each other. In this case, one cycle includes at least three layers and may include four, five or more layers, but is preferably no more than eight layers. The number of cycles of the periodic stacked structure is preferably no less than 30 cycles, and is preferably no more than 50 cycles, more preferably no more than 40 cycles. In the case where the low refractive index layer includes a material containing ruthenium (Ru), the layer (uppermost layer) farthest from the substrate in the periodic stacked structure is preferably a high refractive index layer.

[0052] The thickness of the multilayer reflective film having a periodic stacking structure is adjusted according to the exposure wavelength and the incident angle of the exposure light, and the thickness of the multilayer reflective film is preferably not less than 200nm, more preferably not less than 270nm, and preferably not more than 400nm, more preferably not more than 290nm.

[0053] Examples of methods for forming a multilayer reflective film include a sputtering method in which power is supplied to a target and a plasma of an atmosphere gas is formed by the supplied power (the atmosphere gas is ionized) for sputtering, and an ion beam sputtering method in which an ion beam is irradiated on a target. Sputtering methods include a DC sputtering method in which a DC voltage is applied to a target and an RF sputtering method in which a high-frequency voltage is applied to a target. The sputtering method is a film forming method that utilizes the sputtering phenomenon of gas ions generated by applying a voltage to a target and introducing a sputtering gas into a chamber to ionize the gas. In particular, the magnetron sputtering method has advantages in terms of productivity. Power can be applied to the target by a DC system or an RF system. The DC system also includes a pulse sputtering in which a negative bias voltage applied to a target is reversed for a short time to prevent charge-up of the target.

[0054] The multilayer reflective film can be formed by, for example, a sputtering method using a sputtering device capable of mounting a plurality of targets. In particular, the multilayer reflective film can be formed by using a target appropriately selected from the following: a molybdenum (Mo) target for forming a molybdenum (Mo)-containing layer, a ruthenium (Ru) target for forming a ruthenium (Ru)-containing layer, a silicon (Si) target for forming a silicon (Si)-containing layer, and other targets as targets, and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas as a sputtering gas.

[0055] In addition, in the case where the sputtering is reactive sputtering using a reactive gas, a nitrogen-containing gas such as nitrogen (N2) gas to form a nitrogen (N)-containing film, an oxygen-containing gas such as oxygen (O2) gas to form an oxygen (O)-containing film, a nitrogen oxide gas such as nitrous oxide (N2O) gas, nitric oxide (NO) gas and nitrogen dioxide (NO2) gas to form a nitrogen (N) and oxygen (O)-containing film, a carbon oxide gas such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas to form a carbon (C) and (O)-containing film, a hydrogen-containing gas such as hydrogen (H2) gas to form a hydrogen (H)-containing film or a hydrocarbon gas such as methane (CH4) gas to form a carbon (C) and hydrogen (H)-containing film can be used together with a rare gas.

[0056] In addition, a molybdenum (Mo) target to which boron (B) is added (molybdenum boride (MoB) target) or a silicon (Si) target to which boron (B) is added (silicon boride (SiB) target) may be used to form a layer containing boron (B).

[0057] The protective film is also called a capping film and is a film used to protect the multilayer reflective film. The protective film is usually formed in contact with the multilayer reflective film. The protective film preferably contains ruthenium (Ru) and preferably contains a ruthenium (Ru)-containing material.

[0058] Examples of ruthenium (Ru)-containing materials include simple substances of ruthenium (Ru), and alloys containing ruthenium (Ru) and another metal or metalloid different from ruthenium (Ru). Examples of other metals or metalloids different from ruthenium (Ru) include niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr), silicon (Si), etc. In ruthenium (Ru)-containing materials, simple substances of ruthenium (Ru) or alloys containing ruthenium (Ru) and niobium (Nb) are particularly preferred. The content of other metals or metalloids different from ruthenium (Ru) in the protective film is preferably not more than 30 atomic %, more preferably not more than 20 atomic % on average of the entire film. The lower limit of the content of other metals or metalloids different from ruthenium (Ru) in the protective film is preferably not less than 5 atomic %, more preferably not less than 10 atomic % on average of the entire film, but is not particularly limited thereto.

[0059] The protective film may have a single-layer structure or a multilayer structure in which a plurality of layers having different compositions are combined. In addition, each layer constituting the single layer or the multilayer may have a composition gradient structure in which the composition continuously changes along the thickness direction. The thickness of the protective film is preferably not less than 2 nm, more preferably not less than 3 nm, and preferably not more than 5 nm, more preferably not more than 4 nm.

[0060] The protective film can be formed by using a target appropriately selected from the following targets as a target: a ruthenium (Ru) target, a target of other metals or metalloids other than ruthenium (Ru), in particular a niobium (Nb) target, a rhenium (Re) target, a zirconium (Zr) target, a titanium (Ti) target, a chromium (Cr) target, a silicon (Si) target, a target selected from niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr) and silicon (Si) A target of a mixture of two or more, and a target of ruthenium (Ru) and at least one metal or metalloid other than ruthenium (Ru) selected from niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr) and silicon (Si), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas and xenon (Xe) gas as a sputtering gas, sputtering. Sputtering is preferably performed by a magnetron sputtering method.

[0061] In a reflective mask, the absorption film is a film that absorbs exposure light and reduces reflectivity. In a reflective mask, a transfer pattern is formed by a reflectivity difference between a portion where the absorption film is formed and a portion where the absorption film is not formed. The absorption film may be composed of a single layer or a multilayer, and an anti-reflection layer may be formed at a surface portion of the absorption film.

[0062] The present invention is suitable for the case where the material constituting the absorption film is a material that is less easily etched by dry etching using a chlorine-based gas or a fluorine-based gas, and in particular, a material that is substantially not etched by dry etching using a chlorine-based gas or a fluorine-based gas.

[0063] In the present invention, the absorption film preferably contains a metal other than tantalum (Ta), and more preferably a metal other than both tantalum (Ta) and chromium (Cr). In the present invention, the absorption film preferably does not contain tantalum (Ta). In addition, the absorption film preferably does not contain chromium (Cr). The absorption film is a film containing a material that absorbs EUV light and can be processed into a pattern.

[0064] The metal other than tantalum (Ta) is preferably at least one metal selected from the following: platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co) and zinc (Zn). Compared with the absorption film composed of a material containing tantalum (Ta), the absorption film can be thinned by a material containing the metal. Among these metals, platinum (Pt) or nickel (Ni) is more preferred. The material constituting the absorption film may contain oxygen (O), nitrogen (N), carbon (C) or other metals, and may contain another metal, such as ruthenium (Ru) and at least one metal selected from the following: platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co) and zinc (Zn).

[0065] In the absorption film, the content of metals other than tantalum (Ta), in particular, metals other than both tantalum (Ta) and chromium (Cr) is preferably not less than 20 atomic %, more preferably not less than 30 atomic %. In the absorption film, the content of metals other than tantalum (Ta), in particular, metals other than both tantalum (Ta) and chromium (Cr) is 100 atomic % or less, preferably less than 100 atomic %, more preferably not more than 90 weight %.

[0066] The thickness of the absorption film is preferably not less than 10 nm, more preferably not less than 20 nm, further preferably not less than 30 nm, and preferably not more than 80 nm, more preferably not more than 70 nm. The sheet resistance of the absorption film is preferably not more than 1×10 6 Ω / square, more preferably not more than 1×10 5 Ω / square The surface roughness Sq of the absorption film is preferably not more than 0.8 nm, more preferably not more than 0.6 nm.

[0067] The absorption film can be formed by sputtering, and the sputtering is preferably performed by a magnetron sputtering method. Specifically, with respect to the absorption film, according to the composition, it can be formed by using a target selected from a target of a metal constituting the absorption film, a target of a compound of a metal constituting the absorption film (a target containing a metal constituting the absorption film and oxygen (O), nitrogen (N), carbon (C), etc.), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas and xenon (Xe) gas as a sputtering gas; or according to the composition, it can be formed by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, a carbon-containing gas or other gas and a rare gas as a sputtering gas. Examples of reactive gases include oxygen (O2) gas, nitrogen (N2) gas, nitrogen oxide gases such as nitrous oxide (N2O) gas, nitric oxide (NO) gas and nitrogen dioxide (NO2) gas, and carbon oxide gases such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas.

[0068] In the present invention, the etching stopper film is a film for protecting the protective film to prevent etching from reaching the protective film during patterning of the absorbing film. The etching stopper film is usually formed in contact with both the protective film and the absorbing film. The etching stopper film preferably has an etching resistance and a thickness such that etching in the pattern forming the absorbing film cannot reach the protective film below the etching stopper film (on the substrate side), in other words, after etching in the pattern forming the absorbing film reaches the etching stopper film, for example, during over-etching, the etching stopper film does not disappear during etching in the pattern forming the absorbing film.

[0069] In the case where the material constituting the absorption film is a material that is less susceptible to being etched by dry etching using a chlorine-based gas or a fluorine-based gas, ion beam etching or methanol etching is preferably used as etching for forming the pattern of the absorption film. However, the protective film can also be etched by these etchings. Therefore, compared with the absorption film, the etching stop film preferably contains a material that is less susceptible to being etched by ion beam etching and methanol etching, that is, the etching stop film preferably has a lower etching rate than the absorption film. Specifically, it is preferred that the etching selectivity of the etching stop film to the absorption film in ion beam etching is preferably less than 1, more preferably not more than 0.9, and further more preferably not more than 0.8. The etching selectivity of the etching stop film to the absorption film in methanol etching is preferably less than 1, more preferably not more than 0.9, and further more preferably not more than 0.8. In the present invention, the etching selectivity is the ratio of the etching rates of the two films under the same conditions. For example, the etching selectivity of the etching stop film to the absorption film is the ratio of the etching rate of the etching stop film to the etching rate of the absorption film.

[0070] On the other hand, the etching stopper film is usually removed by etching after the pattern of the absorption film is formed. Therefore, in the case where the material constituting the absorption film is a material that is less easily etched by dry etching using a chlorine-based gas or a fluorine-based gas, the etching stopper film preferably contains a material that is easily etched by dry etching using a chlorine-based gas or a fluorine-based gas, that is, the etching stopper film preferably has a high etching rate compared with the absorption film. Specifically, it is preferred that the etching selectivity of the etching stopper film to the absorption film in dry etching using a chlorine-based gas or a fluorine-based gas is preferably greater than 1, more preferably not less than 5, and further more preferably not less than 10.

[0071] In the present invention, examples of dry etching using chlorine-based gases include dry etching using a gas containing chlorine (Cl), such as dry etching using a gas containing chlorine (Cl2) gas, dry etching using a gas containing hydrogen chloride (HCl) gas, and dry etching using a gas containing chlorine (Cl) and oxygen (O), such as dry etching using a gas containing chlorine (Cl2) gas and oxygen (O2) gas. On the other hand, examples of dry etching using fluorine-based gases include dry etching using a gas containing carbon tetrafluoride (CF4) gas or sulfur hexafluoride (SF6) gas.

[0072] The etching stopper film preferably contains tantalum (Ta) and is preferably composed of a tantalum (Ta)-containing material. The tantalum (Ta) content of the etching stopper film is preferably not less than 30 atomic %, more preferably not less than 40 atomic %. The material constituting the etching stopper film may contain oxygen (O), nitrogen (N), carbon (C), etc. In particular, the etching stopper film preferably contains nitrogen (N), and is more preferably composed of tantalum (Ta) and nitrogen (N). In the case where the metal contained in the absorption film is platinum (Pt) or nickel (Ni), an etching stopper film composed of tantalum (Ta) and nitrogen (N) is particularly preferred. In the case where the etching stopper film contains tantalum (Ta) and nitrogen (N), specifically in the case where it is composed of tantalum (Ta) and nitrogen (N), the nitrogen content of the etching stopper film is preferably not less than 10 atomic %, more preferably not less than 40 atomic %, and preferably not more than 70 atomic %, more preferably not more than 60 atomic %.

[0073] The material constituting the etching stopper film may contain a metal other than tantalum (Ta), preferably a metal other than both tantalum (Ta) and chromium (Cr), particularly a metal that is easily etched by dry etching using a chlorine-based gas or a fluorine-based gas. However, the metal preferably does not contain a metal contained in the absorption film, particularly platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co), and zinc (Zn).

[0074] The thickness of the etching stopper film is preferably not greater than the thickness of the absorption film, and more preferably not greater than half the thickness of the absorption film. Specifically, since it is preferred that the total thickness of the absorption film and the etching stopper film (the thickness of the portion of the circuit pattern or the mask pattern in the reflective mask) is thin, the thickness of the etching stopper film is preferably not greater than 10 nm, and more preferably not greater than 5 nm. On the other hand, the thickness of the etching stopper film is preferably not less than 1 nm, and more preferably not less than 2 nm, in order to prevent etching in the patterning of the absorption film from reaching the protective film.

[0075] The etching stop film can be formed by sputtering, and the sputtering is preferably performed by a magnetron sputtering method. Specifically, with respect to the etching stop film, according to the composition, it can be formed by using a target selected from a metal (such as tantalum (Ta)) constituting the etching stop film, a target of a compound of the metal constituting the etching stop film (a target containing a metal constituting the etching stop film and oxygen (O), nitrogen (N), carbon (C), etc.), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas and xenon (Xe) gas as a sputtering gas sputtering; or according to the composition, it can be formed by using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, a carbon-containing gas or other gas and a rare gas as a sputtering gas reactive sputtering. Examples of reactive gases include oxygen (O2) gas, nitrogen (N2) gas, nitrogen oxide gases such as nitrous oxide (N2O) gas, nitric oxide (NO) gas and nitrogen dioxide (NO2) gas, and carbon oxide gases such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas.

[0076] In the present invention, the first hard mask film is a film that serves as an etching mask in etching for forming a pattern of the absorption film. In the present invention, since ion beam etching or methanol etching is applied as etching for forming a pattern of the absorption film, a first hard mask film is provided on the absorption film. The first hard mask film is usually formed in contact with the absorption film. In the case where the absorption film includes a layer (reflectivity reducing layer) that assumes the function of reducing the reflectivity at the wavelength of light used in inspection such as pattern inspection at the top of the absorption film, the first hard mask film can be formed on the reflectivity reducing layer of the absorption film.

[0077] In the case where the material constituting the absorption film is a material that is less susceptible to being etched by dry etching using a chlorine-based gas or a fluorine-based gas, ion beam etching or methanol etching is preferably used as etching for forming a pattern of the absorption film. Therefore, compared with the absorption film, the first hard mask film preferably contains a material that is less susceptible to being etched by ion beam etching and methanol etching, that is, the first hard mask film preferably has a lower etching rate than the absorption film. Specifically, it is preferred that the etching selectivity of the first hard mask film to the absorption film in ion beam etching is preferably less than 1, more preferably not more than 0.9, and further more preferably not more than 0.8. It is preferred that the etching selectivity of the first hard mask film to the absorption film in methanol etching is preferably less than 1, more preferably not more than 0.9, and further more preferably not more than 0.8.

[0078] On the other hand, the first hard mask film is usually removed by etching after the pattern of the absorption film is formed. Therefore, in the case where the material constituting the absorption film is a material that is less easily etched by dry etching using a chlorine-based gas or a fluorine-based gas, the first hard mask film preferably contains a material that is easily etched by dry etching using a chlorine-based gas or a fluorine-based gas. In other words, the absorption film is relatively less easily etched by dry etching using a chlorine-based gas or a fluorine-based gas, that is, the first hard mask film preferably has a high etching rate compared to the absorption film. Specifically, the etching selectivity of the absorption film to the first hard mask film in dry etching using a chlorine-based gas or a fluorine-based gas is preferably not more than 0.3, and more preferably not more than 0.15.

[0079] The first hard mask film preferably contains tantalum (Ta) and is preferably composed of a tantalum (Ta)-containing material. The tantalum (Ta) content of the first hard mask film is preferably not less than 30 atomic %, more preferably not less than 40 atomic %. The material constituting the first hard mask film may contain oxygen (O), nitrogen (N), carbon (C), etc. In particular, the first hard mask film preferably contains nitrogen (N), and more preferably consists of tantalum (Ta) and nitrogen (N). In the case where the metal contained in the absorption film is platinum (Pt) or nickel (Ni), a first hard mask film composed of tantalum (Ta) and nitrogen (N) is particularly preferred. In the case where the first hard mask film contains tantalum (Ta) and nitrogen (N), specifically, in the case where it is composed of tantalum (Ta) and nitrogen (N), the nitrogen content of the first hard mask film is preferably not less than 10 atomic %, more preferably not less than 40 atomic %, and preferably not more than 70 atomic %, more preferably not more than 60 atomic %.

[0080] The material constituting the first hard mask film may contain a metal other than tantalum (Ta), preferably a metal other than both tantalum (Ta) and chromium (Cr), particularly a metal that is easily etched by dry etching using a chlorine-based gas or a fluorine-based gas. However, the metal preferably does not contain a metal contained in the absorption film, particularly platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co), and zinc (Zn).

[0081] The first hard mask film is preferably removed at the same time as the etching stopper film is removed by etching. Therefore, the first hard mask film preferably contains the same element (one or more) as the etching stopper film, in particular, the same composition ratio. In addition, the etching rate of the first hard mask film is preferably set to be approximately equal to the etching rate of the etching stopper film, and specifically, the etching selectivity of the first hard mask film to the etching stopper film is preferably not less than 0.5 and not more than 1.5.

[0082] The first hard mask film thickness is a thickness such that the first hard mask film will remain after etching in a pattern for forming an absorption film, and is preferably the same as or smaller than the thickness such that the etching stopper film remains. Specifically, the thickness of the first hard mask film is preferably not less than 2 nm, more preferably not less than 5 nm, and preferably not more than 30 nm, more preferably not more than 15 nm.

[0083] The first hard mask film can be formed by sputtering, and the sputtering is preferably performed by a magnetron sputtering method. Specifically, with respect to the first hard mask film, depending on the composition, it can be formed by sputtering using a suitable target selected from a target of a metal constituting the first hard mask film (e.g., tantalum (Ta)), a target of a compound of the metal constituting the first hard mask film (a target containing the metal constituting the first hard mask film and oxygen (O), nitrogen (N), carbon (C), etc.), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas as a sputtering gas; or, depending on the composition, it can be formed by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, a carbon-containing gas, or other gas and a rare gas as a sputtering gas. Examples of reactive gases include oxygen (O2) gas, nitrogen (N2) gas, nitrogen oxide gases such as nitrous oxide (N2O) gas, nitric oxide (NO) gas and nitrogen dioxide (NO2) gas, and carbon oxide gases such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas.

[0084] A second hard mask film may be provided on the first hard mask film away from the substrate. The second hard mask film is a film that acts as an etching mask when etching the first hard mask film and needs to have etching characteristics different from those of the first hard mask film. The second hard mask film is preferably formed in contact with the first hard mask film.

[0085] Figure 2 The sectional view is a diagram showing an example (second embodiment) of a reflective mask blank of the present invention. The reflective mask blank 12 includes: a substrate 1; and on the substrate 1, a multilayer reflective film 2 formed in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, an etching stopper film 4 formed in contact with the protective film 3, an absorption film 5 formed in contact with the etching stopper film 4, a first hard mask film 6 formed in contact with the absorption film 5, and a second hard mask film 7 formed in contact with the first hard mask film 6.

[0086] The second hard mask film preferably contains chromium (Cr) and is preferably composed of a chromium (Cr)-containing material. The chromium (Cr)-containing material has different etching characteristics from the first hard mask film when processing the first hard mask film composed of a tantalum (Ta)-containing material, and acts as an etching mask when etching the first hard mask film. Therefore, the chromium (Cr)-containing material for the second hard mask film preferably does not contain tantalum (Ta).

[0087] Examples of chromium (Cr)-containing materials include simple substances of chromium (Cr) and chromium compounds containing chromium (Cr) and at least one selected from oxygen (O), nitrogen (N) and carbon (C). In particular, chromium compounds containing chromium (Cr) and at least one selected from oxygen (O), nitrogen (N) and carbon (C) are preferred. Examples of chromium compounds include CrO, CrN, CrON, CrC, CrOC, CrNC and CrONC. In this case, the chromium compound preferably has a chromium (Cr) content of not less than 20 atomic %, more preferably not less than 30 atomic %. In addition, the chromium compound preferably has an oxygen (O) content of not more than 50 atomic %, more preferably not more than 40 atomic %, a nitrogen (N) content of not more than 40 atomic %, more preferably not more than 30 atomic %, or a carbon (C) content of not more than 20 atomic %.

[0088] From the viewpoint of reducing the thickness of the resist film in the pattern forming the second hard mask film, the thickness of the second hard mask film is not more than 20 nm, more preferably not more than 10 nm, and further more preferably not more than 7 nm, but is not particularly limited thereto. The thickness of the second hard mask film is usually not less than 5 nm.

[0089] The second hard mask film can be formed by sputtering, and the sputtering is preferably performed by a magnetron sputtering method. Specifically, as for the second hard mask film, according to the composition, it can be formed by sputtering using a suitable target selected from a target of a metal constituting the second hard mask film (e.g., chromium (Cr)), a target of a compound of the metal constituting the second hard mask film (a target containing the metal constituting the second hard mask film and oxygen (O), nitrogen (N), carbon (C), etc.), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas as a sputtering gas; or according to the composition, it can be formed by reactive sputtering using a reactive gas such as an oxygen-containing gas, a nitrogen-containing gas, a carbon-containing gas, or other gas and a rare gas as a sputtering gas. Examples of reactive gases include oxygen (O2) gas, nitrogen (N2) gas, nitrogen oxide gases such as nitrous oxide (N2O) gas, nitric oxide (NO) gas and nitrogen dioxide (NO2) gas, and carbon oxide gases such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas.

[0090] A back surface conductive film for electrostatically clamping the reflective mask to the exposure apparatus may be formed on the other main surface (back surface) as an opposing surface to one main surface in the substrate, preferably in contact with the other main surface.

[0091] The sheet resistance of the back surface conductive film is preferably not more than 100Ω / square, and there is no particular restriction on the material for the conductive film. Examples of materials for the back surface conductive film include, for example, materials containing tantalum (Ta) or chromium (Cr). Materials containing tantalum (Ta) or chromium (Cr) may contain oxygen (O), nitrogen (N), carbon (C), boron (B) or other elements. Examples of materials containing tantalum (Ta) include, for example, simple substances of Ta and tantalum (Ta) compounds such as TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB and TaCONB. Examples of materials containing chromium (Cr) include, for example, simple substances of Cr and chromium (Cr) compounds such as CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB, CrOB, CrNB, CrONB, CrCB, CrCNB, CrCOB and CrCONB.

[0092] The thickness of the back surface conductive film is generally about 5 to 100 nm, but is not particularly limited thereto as long as the thickness is sufficient for electrostatic clamping purposes. The back surface conductive film is preferably formed to a thickness such that after preparing a reflective mask, that is, after forming a pattern of an absorption film, the film stress between the back surface conductive film and the film (s) formed at one main surface (front surface) and the pattern (s) of the film (s) is balanced. The back surface conductive film may be formed before forming a multilayer reflective film, or after forming all films on the multilayer reflective film side of the substrate. The back surface conductive film may be formed after forming a portion of the film on the multilayer reflective film side of the substrate, and then the remaining film may be formed on the multilayer reflective film side of the substrate. The back surface conductive film can be formed by, for example, a magnetron sputtering method.

[0093] The reflective mask blank may include a resist film formed on a side farthest from the substrate. The resist film is preferably an electron beam (EB) resist.

[0094] From the reflective mask blank, for example, a reflective mask can be obtained, which includes a substrate, a multilayer reflective film formed on one main surface of the substrate, a protective film formed in contact with the multilayer reflective film, a pattern of an etching stopper film formed in contact with the protective film, and a pattern of an absorption film formed in contact with the pattern of the etching stopper film. In the reflective mask, a transfer pattern is formed by forming a reflectivity difference between a portion (circuit pattern or mask pattern) of the etching stopper film below the absorption film (substrate side) and a portion where the circuit pattern or mask pattern is not formed.

[0095] Figure 3 1 is a cross-sectional view showing an example of a reflective mask of the present invention. The reflective mask 10 includes: a substrate 1; and on the substrate 1, a multilayer reflective film 2 formed in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, a pattern 41 of an etching stopper film formed in contact with the protective film 3, and a pattern 51 of an absorption film formed in contact with the pattern 41 of the etching stopper film. In this reflective mask 10, the pattern 51 of the absorption film is formed on the protective film 3 via the pattern 41 of the etching stopper film.

[0096] From the reflective mask blank of the present invention, a reflective mask can be manufactured by a method including the steps of: etching a first hard mask film; patterning an absorption film by etching; and etching an etching stopper film.

[0097] Furthermore, from the reflective mask blank including the second hard mask film, a reflective mask can be manufactured by a method including the steps of: etching the second hard mask film; etching the first hard mask film; patterning the absorption film by etching; and etching the etching stopper film.

[0098] In the case of manufacturing a reflective mask from a reflective mask blank that does not include a second hard mask film, specifically, the reflective mask can be manufactured by a method including the following steps: preparing a reflective mask blank; optionally forming a resist film on a first hard mask film; forming a resist pattern from the resist film on the first hard mask film; etching the first hard mask film by using the resist pattern as an etching mask to form a pattern of the first hard mask film; removing the resist pattern; etching the absorption film by using the pattern of the first hard mask film as an etching mask to form a pattern of the absorption film; and removing the etching stopper film and the pattern of the first hard mask film in the portion exposed by removing the absorption film by etching.

[0099] On the other hand, in the case of manufacturing a reflective mask from a reflective mask blank including a second hard mask film, specifically, the reflective mask can be manufactured by a method including the following steps: preparing a reflective mask blank; optionally forming a resist film on the second hard mask film; forming a resist pattern from the resist film on the second hard mask film; etching the second hard mask film by using the resist pattern as an etching mask to form a pattern of the second hard mask film; removing the resist pattern; etching the first hard mask film by using the pattern of the second hard mask film as an etching mask to form a pattern of the first hard mask film; removing the pattern of the second hard mask film by etching; etching the absorption film by using the pattern of the first hard mask film as an etching mask to form a pattern of the absorption film; and removing the etching stopper film and the pattern of the first hard mask film in the portion exposed by removing the absorption film by etching.

[0100] The resist film is preferably formed of an electron beam (EB) resist, and the resist pattern can be formed by drawing or exposing a pattern to the resist film using an electron beam (EB) etc. and then developing. The resist pattern can be removed by washing with a sulfuric acid-hydrogen peroxide mixture (SPM).

[0101] The etching for the absorption film is preferably ion beam etching or methanol etching. The absorption film can be etched by only one of ion beam etching and methanol etching, or by a combination of beam etching and methanol etching. In the case of a combination of the two, methanol etching is preferably performed after ion beam etching.

[0102] Ion beam etching is a method of physically etching a target to be etched by charged particles (ions) accelerated by collision. Examples of charged particles (ions) used in ion beam etching include charged particles (ions) of rare gases such as xenon (Xe) gas and argon (Ar) gas. Among them, charged particles (ions) of argon (Ar) gas are preferably used. On the other hand, methanol etching is dry etching using methanol gas.

[0103] The etching for forming the pattern of the absorption film can be performed as follows: first, ion beam etching is performed, and before the absorption film is completely etched, that is, when at least a portion, preferably a small thickness (for example, a thickness of about 1 to 5 nm) of the absorption film remains in the thickness direction, the etching is switched to methanol etching, and the remaining portion of the absorption film is etched by methanol etching until the entire absorption film is etched. In particular, this method is suitable for the case where the metal contained in the absorption film is platinum (Pt) or nickel (Ni).

[0104] The first hard mask film and its pattern are etched, the second hard mask film and its pattern are etched, and the etching of the etching stop film is preferably dry-etched using a chlorine-based gas or a fluorine-based gas. In particular, the dry etching using a chlorine-based gas for the second hard mask film and its pattern is preferably dry-etched using a chlorine-based gas containing chlorine (C) and oxygen (O). For example, a film containing tantalum (Ta) can be etched by dry etching using a fluorine-based gas. A film containing tantalum (Ta) can also be etched by dry etching using a chlorine-based gas. In the case of etching a film containing tantalum (Ta) by dry etching using a chlorine-based gas, it is preferably etched in combination with dry etching using a fluorine-based gas. On the other hand, a film containing chromium (Cr) can be etched by dry etching using a chlorine-based gas, particularly by dry etching using a chlorine-based gas containing chlorine (C) and oxygen (O). To etch the pattern of the first hard mask film, the same etch as that used to pattern the first hard mask film may be applied, and to etch the pattern of the second hard mask film, the same etch as that used to pattern the second hard mask film may be applied.

[0105] In order to avoid damage to the protective film and further to avoid damage to the multilayer reflective film formed below the absorption film (on the substrate side), it is preferred to etch the absorption film so that after etching in the patterning of the absorption film, the etching stop film does not completely disappear, that is, at least a portion remains in the direction of the etching stop film.

[0106] The etching stopper film exposed by removing the absorption film and the pattern of the first hard mask film can be removed simultaneously by the same etching. In this case, in order to avoid damage to the protective film and further to avoid damage to the multilayer reflective film formed below the absorption film (on the substrate side), it is preferable to perform etching so that the pattern of the first hard mask film is removed before completely removing the etching stopper film exposed by removing the absorption film.

[0107] In the present invention, an etching stop film may be provided to contact both the protective film and the absorption film, and a first hard mask film may be provided on the absorption film, and a pattern of the absorption film can be formed by the following steps: forming a pattern of the first hard mask film by dry etching; patterning the absorption film by ion beam etching or ion beam etching and methanol etching using the pattern of the first hard mask film as an etching mask; and removing the etching stop film by dry etching.

[0108] In this case, a second hard mask film may also be provided on the first hard mask film; a pattern of the second hard mask film may be formed by dry etching using a gas containing chlorine (Cl) and oxygen (O); and a pattern of the first hard mask film may be formed using the pattern of the second hard mask film as an etching mask.

[0109] By providing an etching stopper film between the protective film and the absorption film, a reflective mask can be manufactured without damaging the film provided below the protective film (on the substrate side) even when the absorption film is etched by ion beam etching or methanol etching during patterning of the absorption film.

[0110] Example

[0111] In the following, examples of the invention are given by way of illustration and not by way of limitation.

[0112] Example 1

[0113] On a titanium dioxide-doped quartz substrate having a size of 152 mm square and a thickness of 6 mm, a multilayer reflective film (thickness: 280 nm, reflectivity with respect to light having a wavelength of 13.5 nm: 65%) is formed by sputtering using a molybdenum (Mo) target and a silicon (Si) target as targets and argon (Ar) gas as a sputtering gas, in which a layer of molybdenum (Mo) and a layer of silicon (Si) are periodically stacked.

[0114] Next, a protective film (thickness: 5 nm) containing ruthenium (Ru) was formed by sputtering using a ruthenium (Ru) target as a target and argon (Ar) gas as a sputtering gas.

[0115] Next, an etching stopper film (thickness: 5 nm) including tantalum nitride (TaN, Ta: 52 atomic %, N: 48 atomic %) was formed by sputtering using a tantalum (Ta) target as a target and argon (Ar) gas and nitrogen (N2) gas as sputtering gas.

[0116] Next, an absorption film (thickness: 20 nm) containing nickel (Ni) was formed by sputtering using a nickel (Ni) target as a target and argon (Ar) gas as a sputtering gas.

[0117] Next, a first hard mask film (thickness: 15 nm) containing tantalum nitride (TaN, Ta: 52 atomic %, N: 48 atomic %) is formed by sputtering using a tantalum (Ta) target as a target and argon (Ar) gas and nitrogen (N2) gas as sputtering gas.

[0118] Next, a second hard mask film (thickness: 10 nm) containing chromium nitride (CrN, Cr: 87 atomic %, N: 13 atomic %) was formed by sputtering using a chromium (Cr) target as a target and argon (Ar) gas and nitrogen (N2) gas as sputtering gas to obtain a reflective mask blank.

[0119] A reflective mask was manufactured from the obtained reflective mask blank. First, a resist pattern was formed by coating a resist film (thickness: 100 nm) on the second hard mask film, irradiating an electron beam, and developing.

[0120] Next, using the resist pattern as an etching mask, a pattern of a second hard mask film including chromium nitride (CrN) was formed by dry etching using a chlorine-based gas under the following conditions.

[0121] <Dry Etching Conditions for Second Hard Mask Film>

[0122] Equipment: ICP (Inductively Coupled Plasma) method

[0123] Gas: Chlorine (Cl2) gas (flow rate: 185sccm), and oxygen (O2) gas (flow rate: 2sccm)

[0124] Gas pressure: 6mTorr (0.8Pa)

[0125] ICP power: 400W

[0126] Next, the resist pattern is removed by SPM cleaning.

[0127] Next, using the pattern of the second hard mask film as an etching mask, a pattern of a first hard mask film including tantalum nitride (TaN) was formed under the following conditions by dry etching using a fluorine-based gas.

[0128] <Dry Etching Conditions for First Hard Mask Film>

[0129] Equipment: ICP (Inductively Coupled Plasma) method

[0130] Gas: Sulfur hexafluoride (SF6) gas and helium (He) gas

[0131] Gas pressure: 4mTorr (0.53Pa)

[0132] ICP power: 400W

[0133] Next, the pattern of the second hard mask film including chromium nitride (CrN) is removed by dry etching using a chlorine-based gas under the above dry etching conditions of the second hard mask film.

[0134] Next, using the pattern of the first hard mask film as an etching mask, a pattern of an absorption film including nickel (Ni) was formed by ion beam etching under the following conditions.

[0135] <Ion Beam Etching Conditions for Absorption Film>

[0136] Gas: Ar (flow rate: 1.5 cm 3 / minute)

[0137] Accelerating voltage: 2kV

[0138] Beam current: 165μA

[0139] Next, by dry etching using fluorine-based gas under the above dry etching conditions for the first hard mask film, the etching stop film containing tantalum nitride (TaN) is removed from the portion exposed by removing the absorption film, thereby removing the pattern of the first hard mask film containing tantalum nitride (TaN), and the dry etching using fluorine-based gas is stopped when the pattern of the first hard mask film is completely removed.

[0140] Next, the remaining etching stopper film including tantalum nitride (TaN) was removed by dry etching using a chlorine-based gas under the following conditions to obtain a reflective mask.

[0141] <Dry Etching Conditions for Etching Stop Film>

[0142] Equipment: ICP (Inductively Coupled Plasma) method

[0143] Gas: Chlorine (Cl2) gas

[0144] Gas pressure: 3mTorr (0.40Pa)

[0145] ICP power: 350W

[0146] By inspecting the obtained reflective mask, it was found that the absorption film containing nickel (Ni) had been etched, the pattern of the absorption film had been formed in a predetermined shape, and the protective film containing ruthenium (Ru) exposed in the part where the absorption film did not exist in the reflective mask was not damaged by etching.

[0147] Example 2

[0148] A reflective mask blank was obtained in the same manner as in Example 1 except that a platinum (Pt) target was used as a target to form an absorption film (thickness: 20 nm) containing platinum (Pt).

[0149] By inspecting the obtained reflective mask, it was found that the absorption film containing platinum (Pt) had been etched, the pattern of the absorption film had been formed in a predetermined shape, and the protective film containing ruthenium (Ru) exposed in the part where the absorption film did not exist in the reflective mask was not damaged by etching.

[0150] Comparative Example 1

[0151] A reflective mask blank was obtained in the same manner as in Example 1, except that the second hard mask film and the etching stopper film were not formed and the absorption film was formed directly on the protective film.

[0152] A reflective mask was manufactured from the obtained reflective mask blank. First, a resist pattern was formed by coating a resist film (thickness: 100 nm) on the first hard mask film, irradiating an electron beam, and developing.

[0153] Next, using the resist pattern as an etching mask, a pattern of a first hard mask film including tantalum nitride (TaN) is formed under the dry etching conditions of the first hard mask film in Embodiment 1 by dry etching using a fluorine-based gas.

[0154] Next, the resist pattern is removed by SPM cleaning.

[0155] Next, using the pattern of the first hard mask film as an etching mask, a pattern of an absorption film including nickel (Ni) is formed by ion beam etching under the ion beam etching conditions for the absorption film in Example 1.

[0156] Next, the pattern of the first hard mask film including tantalum nitride (TaN) is removed by dry etching using a fluorine-based gas under the above dry etching conditions of the first hard mask film to obtain a reflective mask.

[0157] By inspecting the obtained reflective mask, it was found that the absorption film containing nickel (Ni) had been etched and the pattern of the absorption film had been formed in a predetermined shape, however, it was found that the protective film containing ruthenium (Ru) exposed in the portion where the absorption film did not exist in the reflective mask had been etched and a portion of the multilayer reflective film had been exposed.

[0158] Comparative Example 2

[0159] Without forming a second hard mask film and an etching stop film, an absorption film is formed directly on the protective film, and as the absorption film, an absorption film (thickness: 20 nm) containing chromium nitride (CrN, Cr: 87 atomic %, N: 13 atomic %) is formed by sputtering using a chromium (Cr) target as a target and argon (Ar) gas and nitrogen (N2) gas as sputtering gas. Except for this, a reflective mask blank is obtained in the same manner as in Example 1.

[0160] A reflective mask was manufactured from the obtained reflective mask blank. First, a resist pattern was formed by coating a resist film (thickness: 100 nm) on the first hard mask film, irradiating an electron beam, and developing.

[0161] Next, using the resist pattern as an etching mask, a pattern of a first hard mask film including tantalum nitride (TaN) is formed under the dry etching conditions of the first hard mask film in Embodiment 1 by dry etching using a fluorine-based gas.

[0162] Next, the resist pattern is removed by SPM cleaning.

[0163] Next, using the pattern of the first hard mask film as an etching mask, a pattern of an absorption film including chromium nitride (CrN) is formed by ion beam etching under the ion beam etching conditions for the absorption film in Example 1.

[0164] Next, the pattern of the first hard mask film including tantalum nitride (TaN) is removed by dry etching using a fluorine-based gas under the above dry etching conditions of the first hard mask film to obtain a reflective mask.

[0165] By inspecting the obtained reflective mask, it was found that the absorption film containing chromium nitride (CrN) had been etched and the pattern of the absorption film had been formed in a predetermined shape, however, it was found that the protective film containing ruthenium (Ru) exposed in the portion where the absorption film did not exist in the reflective mask had been etched and a portion of the multilayer reflective film had been exposed.

Claims

1. A reflective mask blank, which is a reflective mask material used in EUV lithography using EUV light as exposure light, comprising: substrate; a multilayer reflective film formed on one main surface of the substrate and reflecting exposure light; A protective film formed on a multilayer reflective film; and An absorption film formed on the protective film to absorb exposure light; wherein, The reflective mask blank includes an etch stopper film formed in contact with both the protective film and the absorption film, and a first hard mask film formed on the absorption film. 2 . The reflective mask blank according to claim 1 , wherein when the absorption film and the etching stopper film are ion-beam etched under the same conditions, an etching selectivity of the etching stopper film to the absorption film is less than 1. 3 . 3 . The reflective mask blank according to claim 1 , wherein when the absorption film and the etching stopper film are subjected to methanol etching under the same conditions, an etching selectivity of the etching stopper film to the absorption film is less than 1. 4 .

4. The reflective mask blank according to claim 1, wherein when the absorption film and the etching stopper film are dry-etched using a chlorine-based gas or a fluorine-based gas under the same conditions, an etching selectivity of the etching stopper film to the absorption film is greater than 1.

5. The reflective mask blank according to claim 1, wherein when the first hard mask film and the absorption film are dry-etched using a chlorine-based gas or a fluorine-based gas under the same conditions, an etching selectivity of the absorption film to the first hard mask film is not more than 0.

3.

6. The reflective mask blank according to claim 1, wherein the absorption film comprises a metal other than tantalum (Ta).

7. The reflective mask blank according to claim 6, wherein the metal other than tantalum (Ta) is at least one metal selected from the group consisting of platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co) and zinc (Zn).

8. The reflective mask blank of claim 6, wherein the etch stop film contains tantalum (Ta).

9. The reflective mask blank of claim 6, wherein the first hard mask film comprises tantalum (Ta). 10 . The reflective mask blank of claim 6 , wherein the etch stop film and the first hard mask film each contain tantalum (Ta) and nitrogen (N).

11. The reflective mask blank according to claim 1, wherein the multilayer reflective film comprises: The high refractive index layer is composed of a material containing silicon (Si) and the low refractive index layer is composed of a material containing molybdenum (Mo).

12. The reflective mask blank of claim 1, wherein the protective film contains ruthenium (Ru).

13. The reflective mask blank of claim 1, further comprising a second hard mask film on the first hard mask film. 14 . The reflective mask blank of claim 13 , wherein the second hard mask film comprises chromium (Cr).

15. A method for manufacturing a reflective mask from the reflective mask blank according to any one of claims 1 to 12, comprising the steps of: dry etching the first hard mask film using a chlorine-based gas or a fluorine-based gas; patterning the absorber film by ion beam etching or ion beam etching and methanol etching; and The etching stopper film is dry-etched using a chlorine-based gas or a fluorine-based gas.

16. A method for manufacturing a reflective mask from the reflective mask blank of claim 13 or 14, comprising the steps of: dry etching the second hard mask film using a gas including chlorine (Cl) and oxygen (O); dry etching the first hard mask film using a chlorine-based gas or a fluorine-based gas; patterning the absorber film by ion beam etching or ion beam etching and methanol etching; and The etching stopper film is dry-etched using a chlorine-based gas or a fluorine-based gas.

17. A method of manufacturing a reflective mask from a reflective mask blank, the reflective mask blank comprising: substrate; a multilayer reflective film formed on one main surface of the substrate and reflecting exposure light; A protective film formed on a multilayer reflective film; and an absorption film for absorbing exposure light formed by patterning the absorption film on the protective film, wherein, in the reflective mask blank, an etching stopper film is provided so as to contact both the protective film and the absorption film, and a first hard mask film is provided on the absorption film, wherein the method comprises patterning the absorption film by the following steps: forming a pattern of a first hard mask film by dry etching using a chlorine-based gas or a fluorine-based gas; patterning the absorption film by ion beam etching or ion beam etching and methanol etching using the pattern of the first hard mask film as an etching mask; and The etching stopper film is removed by dry etching using a chlorine-based gas or a fluorine-based gas.

18. The method according to claim 17, wherein: In the reflective mask blank, a second hard mask film is further provided on the first hard mask film; forming a pattern of a second hard mask film by dry etching using a gas containing chlorine (Cl) and oxygen (O); as well as The pattern of the first hard mask film is formed using the pattern of the second hard mask film as an etching mask.

19. The method according to claim 17 or 18, wherein the etching selectivity of the stopper film to the absorber film in the ion beam etching is less than 1.

20. The method according to claim 17 or 18, wherein the etching selectivity of the stopper film to the absorber film in methanol etching is less than 1.

21. The method according to claim 17 or 18, wherein in the step of removing the etching stopper film, an etching selectivity of the etching stopper film to the absorption film in dry etching using a chlorine-based gas or a fluorine-based gas is greater than 1.

22. The method according to claim 17 or 18, wherein in the step of forming the pattern of the first hard mask film, an etching selectivity of the absorber film to the first hard mask film in dry etching using a chlorine-based gas or a fluorine-based gas is not more than 0.

3.

23. The method of claim 17 or 18, wherein the absorber film comprises a metal other than tantalum (Ta).

24. The method according to claim 23, wherein the metal other than tantalum (Ta) is at least one metal selected from the group consisting of platinum (Pt), nickel (Ni), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), iron (Fe), cobalt (Co) and zinc (Zn).

25. The method of claim 23, wherein the etch stop film comprises tantalum (Ta).

26. The method of claim 23, wherein the first hard mask film comprises tantalum (Ta).

27. The method of claim 23, wherein the etch stopper film and the first hard mask film each contain tantalum (Ta) and nitrogen (N).

28. The method according to claim 17 or 18, wherein the multilayer reflective film comprises: The high refractive index layer is composed of a material containing silicon (Si) and the low refractive index layer is composed of a material containing molybdenum (Mo).

29. The method according to claim 17 or 18, wherein the protective film comprises ruthenium (Ru).

Images