Reflective mask blank and manufacturing method of reflective mask

Abstract

SOLUTION: To provide an etching mask film containing niobium (Nb) but not containing ruthenium (Ru) between a protective film and an absorption film of a reflective mask blank including a substrate, a multilayer reflection film, which is formed on one main surface of the substrate and reflects exposure light, the protective film, which is formed on the multilayer reflection film and protects the multilayer reflection film, and the absorption film, which is formed on the protective film and absorbs the exposure light, where the protective film contains ruthenium (Ru), and it serves as a material for a reflective mask used in EUV lithography employing EUV light as the exposure source.EFFECT: The present invention provides a reflective mask blank including a protective film that is resistant to damage and can suppress a decrease in thickness, even when an absorption film formed on a protection film composed of a material containing ruthenium (Ru) is etched by dry etching using a gas containing chlorine (Cl) and oxygen (O).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask blank, which is a material for a reflective mask used in the manufacture of semiconductor devices such as LSIs, and a method for manufacturing a reflective mask from the reflective mask blank. [Background technology]

[0002] In the manufacturing process of semiconductor devices (semiconductor device), photolithography technology is repeatedly used, in which exposure light is irradiated onto a transfer mask, and the circuit pattern formed on the mask is transferred onto a semiconductor substrate (semiconductor wafer) via a reduced projection optical system. Conventionally, the wavelength of the exposure light has mainly been 193 nm using argon fluoride (ArF) excimer laser light, and a process called multi-patterning, which combines exposure processes and processing processes multiple times, has been used to ultimately form patterns with dimensions smaller than the exposure wavelength.

[0003] However, as device patterns continue to become finer, there is a need to form even finer patterns, and so EUV lithography technology, which uses extreme ultraviolet (EUV) light with an even shorter wavelength than ArF excimer laser light as exposure light, has come to be used. EUV light is light with a wavelength of about 0.2 to 100 nm, more specifically, a wavelength of about 13.5 nm. EUV light has extremely low transparency to materials, so that conventional transmission type projection optical systems and masks cannot be used, and therefore reflective optical elements are used. Therefore, reflective masks are also used for pattern transfer.

[0004] A reflective mask has a multilayer reflective film that reflects EUV light formed on a substrate, and a pattern of an absorbing film that absorbs EUV light formed on the multilayer reflective film. On the other hand, a mask in a state before the absorbing film is patterned (including a mask in a state where a resist film is formed) is called a reflective mask blank, and this is used as the material for a reflective mask. A reflective mask blank generally has a basic structure including a low thermal expansion substrate, a multilayer reflective film that reflects EUV light formed on one of the two main surfaces of the substrate, and an absorbing film that absorbs EUV light formed thereon.

[0005] The multilayer reflective film is usually made by alternately stacking molybdenum (Mo) and silicon (Si) layers to obtain the necessary reflectance for EUV light. On the other hand, the absorbing film is made of tantalum (Ta), which has a relatively large extinction coefficient for EUV light (JP Patent Publication 2002-246299 (Patent Document 1)).

[0006] Furthermore, as disclosed in JP-A-2002-122981 (Patent Document 2), a ruthenium (Ru) film is formed on the multilayer reflective film as a protective film (capping film) for protecting the multilayer reflective film during cleaning of the reflective mask. Also, a hard mask film containing chromium (Cr) may be formed on the absorbing film as an etching mask when forming a pattern on the absorbing film. Meanwhile, a conductive film is formed on the other main surface of the substrate. As the conductive film, a metal nitride film has been proposed for electrostatic chucking, and a film containing mainly chromium (Cr) or tantalum (Ta) is mentioned. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2002-246299 A [Patent Document 2] JP 2002-122981 A Summary of the Invention [Problem to be solved by the invention]

[0008] The protective film is required to have a function of protecting the multilayer reflective film, specifically, a function of protecting the multilayer reflective film from exposure to etching gas or cleaning liquid during pattern processing of the absorbing film, and a function of suppressing a decrease in reflectance with repeated exposure during exposure using a reflective mask.

[0009] In the process of manufacturing a reflective mask using a reflective mask blank as a material, when a pattern is formed in an absorbing film by dry etching, a certain degree of overetching is usually performed to control the pattern shape. By performing overetching, the protective film is exposed to the etching and is damaged. When the absorbing film is formed of a material containing tantalum (Ta), a gas containing chlorine (Cl) and not containing oxygen (O) is preferably used as the etching gas, so the protective film is required to be resistant to dry etching using a gas containing chlorine (Cl) and not containing oxygen (O).

[0010] In addition, when a hard mask film pattern obtained by forming a pattern of a hard mask film made of a material containing chromium (Cr) is used as an etching mask for forming a pattern in the absorbing film, after forming the absorbing film pattern, the hard mask film pattern is usually removed by dry etching using a gas containing chlorine (Cl) and oxygen (O), and at that time, the protective film is also exposed to dry etching using a gas containing chlorine (Cl) and oxygen (O). Therefore, the protective film is also required to be resistant to dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0011] Furthermore, cleaning with sulfuric acid / hydrogen peroxide (SPM) is performed to remove resist residues used in manufacturing the reflective mask and contamination that occurs during repeated use of the reflective mask, so the protective film must also be resistant to SPM.

[0012] If the protective film is damaged during dry etching in the manufacture of a reflective mask, and the film quality or thickness changes, problems such as the loss of the function of protecting the multilayer reflective film occur. For this reason, it has been proposed to add an additive element such as niobium (Nb) to a protective film containing ruthenium (Ru) to improve its resistance to dry etching and enhance the protective film's function of protecting the multilayer reflective film.

[0013] However, even if an additive element such as niobium (Nb) is added to a protective film containing ruthenium (Ru) to increase the resistance to dry etching, the thickness of the protective film decreases when the protective film is exposed to a gas containing chlorine (Cl) but not oxygen (O) during dry etching of an absorbing film formed of a material containing tantalum (Ta). In addition, when the protective film is exposed to a gas containing chlorine (Cl) and oxygen (O) during removal of the pattern of the hard mask film, the thickness of the protective film decreases. Furthermore, the thickness of the protective film decreases when cleaning is performed using sulfuric acid / hydrogen peroxide (SPM).

[0014] As such, chemical damage to the protective film is unavoidable, and physical damage will also reduce the thickness of the protective film, so it is necessary to suppress the deterioration of the function of the protective film to protect the multilayer reflective film due to the reduction in thickness.

[0015] Tantalum (Ta)-based films are generally used for absorbing films, but in order to improve the accuracy of pattern transfer onto the wafer, it is necessary to reduce the pattern height, which corresponds to the film thickness of the absorbing film, and attention has been focused on chromium (Cr)-based absorbing films, which can be made thinner than tantalum (Ta)-based absorbing films.

[0016] However, if a chromium (Cr)-based absorbing film is layered on top of a ruthenium (Ru)-based protective film, which is commonly used as a protective film for multilayer reflective films, the ruthenium (Ru)-based film will also be etched during dry etching using a gas containing chlorine (Cl) and oxygen (O), which is used for dry etching of chromium (Cr)-based films, damaging the ruthenium (Ru)-based protective film and causing it to become thinner.

[0017] The present invention has been made to solve the above-mentioned problems, and has an object to provide a reflective mask blank that is resistant to damage to a protective film and can suppress a reduction in the thickness of the protective film even when an absorbing film formed on a protective film made of a material containing ruthenium (Ru) is dry etched using a gas containing chlorine (Cl) and oxygen (O), and a method for manufacturing a reflective mask using the reflective mask blank. [Means for solving the problem]

[0018] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by providing an etching stop film containing niobium (Nb) but not ruthenium (Ru) between a protective film and an absorbing film of a reflective mask blank in which an absorbing film is formed on a protective film containing ruthenium (Ru), and have thus completed the present invention.

[0019] Accordingly, the present invention provides the following reflective mask blank and method for producing a reflective mask. 1. A reflective mask blank comprising a substrate, a multilayer reflective film formed on one main surface of the substrate and reflecting exposure light, a protective film formed on the multilayer reflective film and protecting the multilayer reflective film, and an absorbing film formed on the protective film and absorbing exposure light, the mask blank being a material for a reflective mask used in EUV lithography in which EUV light is used as the exposure light, The protective film contains ruthenium (Ru), Between the protective film and the absorbing film, there is further provided an etching stop film containing niobium (Nb) and not containing ruthenium (Ru). A reflective mask blank comprising: 2. The reflective mask blank according to 1, wherein the etching stop film is made of simple niobium (Nb) or a niobium (Nb) compound containing niobium (Nb) and oxygen (O). 3. The reflective mask blank according to 1, wherein the protective film is made of ruthenium (Ru). 4. The reflective mask blank according to 1, wherein the absorbing film contains chromium (Cr). 5. The reflective mask blank according to 1, wherein the absorbing film contains tantalum (Ta) and further comprises an etching mask film containing chromium (Cr) on the absorbing film. A method for producing a reflective mask, comprising patterning the absorbing film of the reflective mask blank according to 6.4 by dry etching using a gas containing chlorine (Cl) and oxygen (O). A method for producing a reflective mask, comprising patterning the absorbing film of the reflective mask blank described in 7.5, and then removing the etching mask film by dry etching using a gas containing chlorine (Cl) and oxygen (O). 8. A method for producing a reflective mask from the reflective mask blank according to any one of 1 to 5, comprising the steps of: A method for manufacturing a reflective mask, comprising the steps of: forming a pattern of the absorbing film; and then removing the etching stop film from a portion exposed by removing the absorbing film. 9. The manufacturing method according to claim 8, characterized in that the etching stopper film in the portion exposed after the absorbing film is removed is removed with sulfuric acid / hydrogen peroxide (SPM). Effect of the Invention

[0020] According to the present invention, it is possible to provide a reflective mask blank in which the protective film is unlikely to be damaged and a reduction in the thickness of the protective film can be suppressed even when an absorbing film formed on a protective film made of a material containing ruthenium (Ru) is dry etched using a gas containing chlorine (Cl) and oxygen (O). [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a cross-sectional view showing an example (first embodiment) of a reflective mask blank of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing one example (second embodiment) of the reflective mask blank of the present invention. [Diagram 3] FIG. 1 is a cross-sectional view showing an example of a reflective mask of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention will now be described in further detail. The reflective mask blank of the present invention comprises a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate and reflecting exposure light, a protective film formed on the multilayer reflective film, and an absorbing film formed on the protective film and absorbing exposure light. The reflective mask blank of the present invention also comprises an etching stop film between the protective film and the absorbing film.

[0023] The reflective mask blank of the present invention is suitable as a material for a reflective mask 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, and is usually light with a wavelength of about 13.5 nm. The reflective mask blank and the reflective mask using EUV light as exposure light are also called EUV mask blank and EUV mask, respectively.

[0024] 1 is a cross-sectional view showing one example (first embodiment) of a reflective mask blank of the present invention. This reflective mask blank 11 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, an etching stop film 4 formed in contact with the protective film 3, and an absorbing film 5 formed in contact with the etching stop film 4.

[0025] The substrate preferably has low thermal expansion characteristics for EUV light exposure, and has a thermal expansion coefficient of, for example, ±2×10 -8 / ℃, preferably within ±5×10 -9 It is preferable that the material is made of a material having a temperature within a range of 100°C / °F. Such a material is titania-doped quartz glass (SiO 2 -TiO 2 Glass-based glass, etc. It is preferable to use a substrate having a sufficiently flat surface, and the surface roughness of the main surface of the substrate is preferably 0.5 nm or less, more preferably 0.2 nm or less, in terms of RMS value. Such a surface roughness can be obtained by polishing the substrate, etc. The size of the substrate is preferably 152 mm square for the main surface and 6.35 mm thick for the thickness. A substrate of this size is a so-called 6025 substrate (a substrate with a main surface size of 6 inches square and a thickness of 0.25 inches).

[0026] The multilayer reflective film is a film that reflects exposure light in a reflective mask. The multilayer reflective film is preferably provided in contact with one main surface of the substrate, but another film such as an undercoat film may be provided between the multilayer reflective film and the one main surface of the substrate. The multilayer reflective film has a periodic laminate structure in which a high refractive index layer having a relatively high refractive index to the exposure light and a low refractive index layer having a relatively low refractive index to the exposure light are alternately laminated.

[0027] The high refractive index layer is preferably formed of a material containing silicon (Si). The high refractive index layer may contain one or more additive elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H), or may be composed of a multilayer structure of a layer containing an additive element and a layer not containing an additive element. The thickness of the high refractive index layer is preferably 3.5 nm or more, more preferably 4 nm or more, and is preferably 4.9 nm or less, more preferably 4.4 nm or less.

[0028] The low refractive index layer is preferably formed of a material containing molybdenum (Mo). The low refractive index layer can also be formed of a material containing ruthenium (Ru). The low refractive index layer may contain one or more additive elements selected from oxygen (O), nitrogen (N), carbon (C), boron (B) and hydrogen (H), and may be composed of a multilayer structure including a layer containing an additive element and a layer not containing an additive element. The thickness of the low refractive index layer is preferably 2.1 nm or more, more preferably 2.6 nm or more, and is preferably 3.5 nm or less, more preferably 3 nm or less.

[0029] The periodic stacking structure may include a high refractive index layer and a low refractive index layer, and one or more high refractive index layers and one or more low refractive index layers may be included in one period. The number of layers included in one period is two or more, and one period may be composed of, for example, one high refractive index layer and one low refractive index layer. In addition, one period may include two or more high refractive index layers having different compositions (for example, different composition ratios, different compositions depending on the presence or absence of an additive element, etc.), and may include two or more low refractive index layers having different compositions (for example, different composition ratios, different compositions depending on the presence or absence of an additive element, etc.). In this case, the number of layers included in one period is three or more, and may be four or more or five or more, but is preferably eight or less. The number of periods in the periodic stacking structure is preferably 30 or more, and is preferably 50 or less, more preferably 40 or less. When the low refractive index layer is formed of a material containing ruthenium (Ru), it is preferable that the layer (uppermost layer) farthest from the substrate in the periodic stacking structure is a high refractive index layer.

[0030] The thickness of the multilayer reflective film having a periodic stacked structure is adjusted depending on the exposure wavelength and the incidence angle of the exposure light, but is preferably 200 nm or more, more preferably 270 nm or more, and is preferably 400 nm or less, more preferably 290 nm or less.

[0031] Methods for forming a multilayer reflective film include a sputtering method in which power is supplied to a target, the atmospheric gas is turned into plasma (ionized) by the supplied power, and sputtering is performed, and an ion beam sputtering method in which an ion beam is irradiated onto a target. Sputtering methods include a DC sputtering method in which a direct current 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 formation method in which a voltage is applied to a target with a sputtering gas introduced into a chamber, the gas is ionized, and the sputtering phenomenon caused by the gas ions is utilized. In particular, the magnetron sputtering method is advantageous in terms of productivity. The power applied to the target may be DC or RF, and DC also includes pulse sputtering in which the negative bias applied to the target is reversed for a short period of time to prevent the target from charging up.

[0032] The multilayer reflective film can be formed by a sputtering method using, for example, a sputtering device capable of mounting a plurality of targets. Specifically, the target can be appropriately selected from a molybdenum (Mo) target for forming a layer containing molybdenum (Mo), a ruthenium (Ru) target for forming a layer containing ruthenium (Ru), a silicon (Si) target for forming a layer containing silicon (Si), and the like, and can be formed by using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as the sputtering gas.

[0033] In addition, when sputtering is reactive sputtering using a reactive gas, for example, when forming a film containing nitrogen (N), nitrogen (N 2 When forming a film containing oxygen (O), a nitrogen-containing gas such as oxygen (O 2 When forming a film containing nitrogen (N) and oxygen (O), nitrous oxide (N 2 O) gas, nitric oxide (NO) gas, nitrogen dioxide (NO 2 When forming a film containing carbon (C) and oxygen (O), carbon monoxide (CO) gas, carbon dioxide (CO2 When forming a film containing carbon oxide gas such as SiO2 gas, or hydrogen (H2O), 2 ) gas, and methane (CH 4 ) gas may be used in conjunction with a rare gas.

[0034] Furthermore, when forming a layer containing boron (B), a molybdenum (Mo) target with boron (B) added (molybdenum boride (MoB) target), a silicon (Si) target with boron (B) added (silicon boride (SiB) target), or the like can be used.

[0035] The protective film is also called a capping film. The protective film is a film for protecting the multilayer reflective film. The protective film is usually provided in contact with the multilayer reflective film. The protective film is made of a material containing ruthenium (Ru).

[0036] Examples of materials containing ruthenium (Ru) include ruthenium (Ru) alone, and alloys made of ruthenium (Ru) and metals or metalloids different from ruthenium (Ru). Examples of metals or metalloids different from ruthenium (Ru) include niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr), and silicon (Si). As a material containing ruthenium (Ru), ruthenium (Ru) alone is particularly preferable, and the protective film is preferably made of ruthenium (Ru). The content of metals or metalloids different from ruthenium (Ru) in the protective film is preferably 30 atomic % or less, more preferably 20 atomic % or less, on average throughout the film. The lower limit of the content of metals or metalloids different from ruthenium (Ru) in the protective film is not particularly limited, but is preferably 5 atomic % or more, more preferably 10 atomic % or more, on average throughout the film.

[0037] The protective film may be a single layer structure or a multilayer structure in which multiple layers with different compositions are combined, and each layer constituting the single layer or multiple layers may have a gradient composition structure in which the composition changes continuously in the thickness direction. In particular, one or both of the side of the protective film closest to the multilayer reflective film (in the case of a multilayer structure, the layer closest to the multilayer reflective film) and the side furthest from the multilayer reflective film (in the case of a multilayer structure, the layer furthest from the multilayer reflective film) may be made of ruthenium (Ru).

[0038] In addition, when the protective film has a multilayer structure or a gradient composition structure, it is preferable that the content of a metal or metalloid other than ruthenium (Ru) increases from the multilayer reflective film side toward the side away from the multilayer reflective film in a part or all of the thickness direction of the protective film. In particular, when niobium (Nb) is contained as a metal or metalloid other than ruthenium (Ru), the inclusion of niobium (Nb) is also effective in improving resistance to dry etching using a gas containing chlorine (Cl) and oxygen (O), so it is preferable that the content of niobium (Nb) increases from the multilayer reflective film side toward the side away from the multilayer reflective film in a part or all of the thickness direction of the protective film.

[0039] In the present invention, the dry etching using a gas containing chlorine (Cl) and oxygen (O) is specifically exemplified by chlorine (Cl 2 ) gas and oxygen (O 2 ) gas. The gas containing chlorine (Cl) and oxygen (O) may contain a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0040] The thickness of the protective film is preferably 2 nm or more, more preferably 3 nm or more, and is preferably 5 nm or less, more preferably 4 nm or less.

[0041] The protective film is formed by sputtering a target selected appropriately from a ruthenium (Ru) target, a target of a metal or semimetal different from ruthenium (Ru), specifically, 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 in which two or more selected from niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr) and silicon (Si) are mixed, and a target in which ruthenium (Ru) is mixed with one or more metals or semimetals different from ruthenium (Ru) selected from niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr) and silicon (Si), and the like, and a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas is used as a sputtering gas. The sputtering is preferably performed by magnetron sputtering.

[0042] In a reflective mask, the absorbing film is a film that absorbs exposure light and reduces reflectance. In a reflective mask, a transfer pattern is formed by the difference in reflectance between a portion where the absorbing film is formed and a portion where the absorbing film is not formed. The absorbing film may be a single layer or a multilayer, and an anti-reflection layer or the like may be formed on the surface.

[0043] The absorbing film preferably contains tantalum (Ta) or chromium (Cr). The absorbing film is a film made of a material that absorbs EUV light and can be patterned, and is preferably made of a material containing tantalum (Ta) or a material containing chromium (Cr).

[0044] Materials containing tantalum (Ta) may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Specific examples of materials containing tantalum (Ta) include elemental Ta and tantalum (Ta) compounds such as TaO, TaN, TaON, TaC, TaCO, TaCN, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCOB, TaCNB, and TaCONB. Note that the notation of a metal or semimetal compound by its chemical formula indicates the constituent elements of the compound, and does not mean the composition ratio of the elements. (The same applies below.)

[0045] When the material containing tantalum (Ta) does not contain oxygen (O), it can be etched by dry etching using a gas containing chlorine (Cl). In this case, when the material contains nitrogen (N), the etching rate of the dry etching using a gas containing chlorine (Cl) becomes high. When the material containing tantalum (Ta) contains nitrogen (N) but does not contain oxygen (O), the etching selectivity to the etching stopper film becomes high in the dry etching using a gas containing chlorine (Cl). Therefore, it is preferable that the part of the absorbing film containing tantalum (Ta) that contacts the etching stopper film does not contain oxygen (O), and it is also preferable that the part contains a large amount of nitrogen (N).

[0046] In the present invention, the dry etching using a gas containing chlorine (Cl) is specifically, 2 Examples of the dry etching include a gas containing hydrogen chloride (HCl) gas, etc. It is preferable that the gas containing chlorine (Cl) does not contain a gas containing oxygen (O). The gas containing chlorine (Cl) may contain a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0047] The material containing chromium (Cr) may contain oxygen (O), nitrogen (N), carbon (C), etc. Specific examples of the material containing chromium (Cr) include elemental Cr and chromium (Cr) compounds such as CrO, CrN, CrON, CrC, CrCO, CrCN, and CrCON.

[0048] The sheet resistance of the absorber film is preferably 1×10 6 Ω / □ or less, more preferably 1×10 5 The surface roughness Sq of the absorbing film is preferably 0.8 nm or less, and more preferably 0.6 nm or less.

[0049] The absorbing film (each layer constituting the absorbing film) can be formed by sputtering, and the sputtering is preferably a magnetron sputtering method. Specifically, when forming the absorbing film from a material containing tantalum (Ta), a tantalum (Ta) target or a tantalum (Ta) compound target (a target containing tantalum (Ta) and oxygen (O), nitrogen (N), carbon (C), boron (B), etc.) is appropriately selected according to the composition from among tantalum (Ta) targets and tantalum (Ta) compound targets (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon (C), etc.) is appropriately selected according to the composition from among chromium (Cr) targets and chromium (Cr ... compounds (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon (C), etc.) is appropriately selected according to the composition from among chromium (Cr) targets and chromium (Cr) targets (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon (C), etc.) is appropriately selected according to the composition from among chromium (Cr) targets and chromium (Cr) targets (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon ( 2 ) gas, nitrogen (N 2 ) gas, nitrogen oxide (N 2 O, NO, NO 2 ) gas, carbon oxide (CO, CO 2 The layer can be formed by reactive sputtering using a reactive gas such as a .alpha.-nitrogen 2-sulfur oxide (N2O3) gas.

[0050] An etching mask film having etching characteristics different from those of the absorbing film can be provided on the side of the absorbing film that is away from the substrate as a hard mask for the absorbing film. This etching mask film functions as a hard mask when dry etching the absorbing film. The etching mask film is preferably provided in contact with the absorbing film. The etching mask film may be a single layer or a multilayer.

[0051] 2 is a cross-sectional view showing one example (second embodiment) of the reflective mask blank of the present invention. This reflective mask blank 12 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, an etching stop film 4 formed in contact with the protective film 3, an absorbing film 5 formed in contact with the etching stop film 4, and an etching mask film 6 formed in contact with the absorbing film 5.

[0052] When the absorbing film contains tantalum (Ta), the etching mask film preferably contains chromium (Cr), and the etching mask film is preferably formed of a material containing chromium (Cr). When processing an absorbing film formed of a material containing tantalum (Ta), the etching characteristics of the material containing chromium (Cr) are different from those of the absorbing film, and an etching mask film formed of a material containing chromium (Cr) that functions as an etching mask when dry etching the absorbing film is preferable. Therefore, the material containing chromium (Cr) of the etching mask film preferably does not contain tantalum (Ta). Examples of materials containing chromium (Cr) include simple Cr, CrO, CrN, CrON, CrC, CrOC, CrNC, and CrONC.

[0053] When the absorbing film contains chromium (Cr), the etching mask film preferably contains tantalum (Ta), and the etching mask film is preferably formed of a material containing tantalum (Ta). When processing an absorbing film formed of a material containing chromium (Cr), the etching characteristics of the material containing tantalum (Ta) are different from those of the absorbing film, and an etching mask film formed of a material containing tantalum (Ta) that functions as an etching mask when dry etching the absorbing film is preferable. Therefore, the material containing tantalum (Ta) of the etching mask film preferably does not contain chromium (Cr). Examples of materials containing tantalum (Ta) include simple Ta, TaO, TaN, TaON, TaC, TaOC, TaNC, and TaONC. The material containing tantalum (Ta) may further contain boron (B) or hydrogen (H).

[0054] After the absorbing film pattern is formed, the etching mask film may be left on the reflective mask as a reflectance reduction layer for reducing the reflectance at the wavelength of light used in inspection such as pattern inspection, or it may be removed so that it does not remain on the reflective mask.

[0055] The thickness of the etching mask film is not particularly limited, but if it is too thin, it may not function as a hard mask, and if it is too thick, processing characteristics may deteriorate. Therefore, the thickness is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 5 nm or more, and is preferably 20 nm or less, and more preferably 10 nm or less.

[0056] The etching mask film can be formed by sputtering. Specifically, when a material containing chromium (Cr) is used, a target is appropriately selected from a chromium (Cr) target or a chromium (Cr) compound target (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon (C), etc.), and when a material containing tantalum (Ta) is used, a target is appropriately selected from a tantalum (Ta) target or a tantalum (Ta) compound target (a target containing tantalum (Ta) and oxygen (O), nitrogen (N), carbon (C), boron (B), etc.), depending on the composition. Sputtering is performed using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as a sputtering gas, or a rare gas together with an oxygen-containing gas, nitrogen-containing gas, or carbon-containing gas, specifically, oxygen (O 2 ) gas, nitrogen (N 2 ) gas, nitrogen oxide (N 2 O, NO, NO 2 ) gas, carbon oxide (CO, CO 2 ) gas, hydrogen (H 2 ) gas, hydrocarbon gas (e.g., methane (CH 4 The layer can be formed by reactive sputtering using a reactive gas such as a CrN gas, etc. The sputtering is preferably performed by magnetron sputtering.

[0057] The etching stopper film is a film that protects the protective film and prevents etching of the protective film during dry etching using a gas containing chlorine (Cl) and oxygen (O). Therefore, the etching stopper film functions as an etching stopper against dry etching using a gas containing chlorine (Cl) and oxygen (O). The etching stopper film is a film that contains niobium (Nb) but does not contain ruthenium (Ru).

[0058] A film containing niobium (Nb) is resistant to dry etching using a gas containing chlorine (Cl) and oxygen (O), which is used to etch chromium (Cr)-based films, and functions as a film that protects the protective film. Therefore, an etching stopper film containing niobium (Nb) can prevent damage to the protective film when an absorbing film containing chromium (Cr) is patterned by dry etching using a gas containing chlorine (Cl) and oxygen (O), or when an absorbing film containing tantalum (Ta) is patterned using a pattern of an etching mask film containing chromium (Cr) and then the etching mask film containing chromium (Cr) is removed by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0059] The etching stopper film is preferably made of niobium (Nb) alone, but may be made of a niobium (Nb) compound containing niobium (Nb) and oxygen (O), such as niobium oxide (NbO). The niobium (Nb) compound containing oxygen (O) is preferably mainly composed of niobium (Nb) and oxygen (O), and the total content of niobium (Nb) and oxygen (O) is preferably 70 atomic % or more, more preferably 80 atomic % or more, even more preferably 91 atomic % or more, and particularly preferably 100 atomic %, on average throughout the film. The content of niobium (Nb) is preferably 20 atomic % or more, more preferably 28 atomic % or more, and even more preferably 29 atomic % or more, on average throughout the film.

[0060] The niobium (Nb) compound containing oxygen (O) may further contain an element or compound that is etched by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F), and may contain, for example, elements such as silicon (Si), nitrogen (N), carbon (C), and their compounds. The total content of elements other than niobium (Nb) and oxygen (O) is preferably 30 atomic % or less, more preferably 20 atomic % or less, on average throughout the film. In this case, the total content of oxygen (O), nitrogen (N), and carbon (C) is preferably 72 atomic % or less, on average throughout the film.

[0061] The etching stopper film may be a single layer or multiple layers. Examples of multiple layers include a combination of layers containing niobium (Nb) with different compositions or composition ratios, such as a combination of a layer made of a niobium (Nb) compound containing oxygen (O) and a layer made of niobium (Nb), or a combination of niobium (Nb) compound layers containing oxygen (O) with different composition ratios. Each layer may be a single composition layer or a gradient composition layer having a gradient composition. When the etching stopper film contains oxygen (O), it is preferable to increase the oxygen (O) concentration on the surface side (side away from the substrate), or to make the surface side a layer made of a niobium (Nb) compound containing oxygen (O) and make the substrate side a layer made of niobium (Nb) or a layer containing niobium (Nb) and not containing oxygen (O).

[0062] In the present invention, the dry etching using a gas containing fluorine (F) is specifically, for example, carbon tetrafluoride (CF 4 ) gas and sulfur hexafluoride (SF 6 Fluorine (F)-containing gas may include rare gases such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas.

[0063] The thickness of the etching stop film is preferably 0.5 nm or more, more preferably 1 nm or more, and is preferably 10 nm or less, more preferably 5 nm or less.

[0064] The etching stopper film can be formed by sputtering. The etching stopper film can be formed by sputtering using a niobium (Nb) target and, if necessary, a metal or semimetal target other than niobium (Nb), specifically, a silicon (Si) target, as targets, and a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas as a sputtering gas, or by sputtering using an oxygen-containing gas, nitrogen-containing gas, or carbon-containing gas, specifically, oxygen (O 2 ) gas, nitrogen (N 2) gas, nitrogen oxide (N 2 O, NO, NO 2 ) gas, carbon oxide (CO, CO 2 The layer can be formed by reactive sputtering using a reactive gas such as a Cr-type gas. The sputtering is preferably performed by magnetron sputtering.

[0065] When the etching stop film contains oxygen (O), niobium (Nb) is prone to natural oxidation, so a film of simple niobium (Nb) can be formed and oxidized by exposing it to an atmosphere containing oxygen (O), such as the air, to form a niobium (Nb) compound containing oxygen (O). When a film of simple niobium (Nb) is oxidized, the film may be heat-treated.

[0066] A conductive film (conductive film) used for electrostatically chucking the reflective mask to an exposure device (e.g., an EUV scanner) may be provided on the other main surface (rear surface) of the substrate, which is the surface opposite to the one main surface, preferably in contact with the other main surface.

[0067] The conductive film preferably has a sheet resistance of 100Ω / □ or less, and there is no particular restriction on the material. Examples of the material of the conductive film include materials containing tantalum (Ta) or chromium (Cr). The material containing tantalum (Ta) may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc., and the material containing chromium (Cr) may contain oxygen (O), nitrogen (N), carbon (C), etc. Examples of the material containing tantalum (Ta) include Ta alone and tantalum (Ta) compounds such as TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, and TaCONB. Examples of the material containing chromium (Cr) include Cr alone and chromium (Cr) compounds such as CrO, CrN, CrON, CrC, CrCN, CrCO, and CrCON.

[0068] The thickness of the conductive film is not particularly limited as long as it functions as an electrostatic chuck, but is usually about 20 to 300 nm. The thickness of the conductive film is preferably set to a thickness that balances the film stress with the film and film pattern formed on one main surface (front surface) side after forming it as a reflective mask, i.e., after forming the pattern of the absorbing film. The conductive film may be formed before forming the multilayer reflective film, or after forming all the films on the multilayer reflective film side of the substrate, or may be formed after forming a part of the film on the multilayer reflective film side of the substrate, and then forming the conductive film, and then forming the remaining film on the multilayer reflective film side of the substrate. The conductive film can be formed, for example, by magnetron sputtering.

[0069] The reflective mask blank of the present invention may have a resist film formed on the side farthest from the substrate. The resist film is preferably an electron beam (EB) resist.

[0070] From the reflective mask blank, for example, a reflective mask having 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, an etching stop film pattern formed in contact with the protective film, and an absorbing film pattern (absorbing film pattern) formed in contact with the etching stop film pattern can be manufactured. In the reflective mask, a transfer pattern is formed due to the difference in reflectance between a portion where the absorbing film is formed and a portion where the absorbing film is not formed.

[0071] 3 is a cross-sectional view showing an example of the reflective mask of the present invention. This reflective mask 10 comprises a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, an etching stop film pattern 41 formed in contact with the protective film 3, and an absorbing film pattern 51 formed in contact with the etching stop film pattern 41. In the case of this reflective mask 10, the absorbing film pattern 51 is formed on the protective film 3 via the etching stop film pattern 41.

[0072] The reflective mask of the present invention comprises: providing a reflective mask blank; If necessary, forming a resist film on the absorbing film; forming a resist pattern from the resist film on the absorbing film; a step of etching the absorbing film using the resist pattern as an etching mask to form a pattern of the absorbing film; removing the resist pattern; removing the etching stopper film from the exposed portion after the absorbing film is removed; The method can be produced by a method comprising the steps of:

[0073] An absorbing film formed of a material containing chromium (Cr) can be etched by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0074] In this case, the etching stopper film containing niobium (Nb) is not etched by dry etching using a gas containing chlorine (Cl) and oxygen (O), so damage to the protective film can be prevented.

[0075] An absorbing film formed of a material containing tantalum (Ta) can be etched by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F).

[0076] In dry etching of an absorbing film containing tantalum (Ta), when etching a part containing oxygen (O) formed by natural oxidation, dry etching using a gas containing fluorine (F) is preferable, and when etching a part not containing oxygen (O), dry etching using a gas containing chlorine (Cl) is preferable. Therefore, it is preferable to pattern an absorbing film containing tantalum (Ta) by first dry etching using a gas containing fluorine (F) and then switching to dry etching using a gas containing chlorine (Cl) halfway through. In this case, since the etching stopper film has low resistance to dry etching using a gas containing chlorine (Cl), it is preferable to etch so that the etching stopper film remains. To etch so that the etching stopper film remains, for example, an end point detector attached to the etching device can be used.

[0077] The reflective mask of the present invention further comprises: providing a reflective mask blank; If necessary, forming a resist film on the etching mask film; forming a resist pattern from a resist film on the etching mask film; a step of etching the etching mask film using the resist pattern as an etching mask to form a pattern of the etching mask film; forming a pattern of the absorbing film by etching the absorbing film using the pattern of the etching mask film as an etching mask; removing the resist pattern; removing the pattern of the etching mask film; removing the etching stopper film from the exposed portion after the absorbing film is removed; The method can be produced by a method comprising the steps of:

[0078] After forming the absorbing film pattern, the etching mask film pattern can be removed by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F) if the etching mask film is a film formed of a material containing tantalum (Ta), and can be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O) if the etching mask film is a film formed of a material containing chromium (Cr).

[0079] In the case where the absorbing film contains tantalum (Ta), the etching mask film is a film containing chromium (Cr), and the etching mask film is patterned by dry etching using a gas containing chlorine (Cl) and oxygen (O) to form a pattern of the etching mask film. After the absorbing film is patterned using the pattern of the etching mask film as an etching mask, the etching mask film can be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0080] In this case, the etching stopper film containing niobium (Nb) is not etched by dry etching using a gas containing chlorine (Cl) and oxygen (O), so damage to the protective film can be prevented.

[0081] The resist pattern and the etch stop film exposed after the absorbing film has been removed can be removed using sulfuric acid / hydrogen peroxide (SPM).

[0082] The etching stopper film in the exposed portion after the absorbing film is removed can be removed by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F), but niobium (Nb) is oxidized when exposed to a gas containing oxygen (O) to form niobium oxide (NbO). Niobium oxide (NbO) is difficult to remove by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F), so the etching stopper film is preferably removed by sulfuric acid / hydrogen peroxide (SPM). In this case, the etching stopper film can be removed simultaneously with the removal of the resist pattern.

[0083] The absorbing film pattern and exposed protective film can be subjected to a treatment in which they come into contact with sulfuric acid / hydrogen peroxide (SPM), for example, cleaning with SPM. EXAMPLES

[0084] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0085] [Examples 1 and 2] Precision polished, titania doped SiO 2 A multilayer reflective film was formed by sputtering on one main surface of a substrate with a low thermal expansion coefficient, in which 40 pairs (periods) of molybdenum (Mo) layers and silicon (Si) layers were alternately stacked, with one pair (period) being a 3 nm thick molybdenum (Mo) layer and a 4 nm thick silicon (Si) layer. Next, a 3 nm thick ruthenium (Ru) film was formed by sputtering on the multilayer reflective film as a protective film. This multilayer reflective film and protective film have a reflectance of 64% when EUV light with a wavelength of 13.5 nm is incident at an incident angle of 6°.

[0086] Next, a 2 nm thick niobium oxide (NbO) film (Nb:O = 2:5 (atomic ratio)) was formed on the protective film as an etching stop film. The niobium oxide (NbO) film was formed by first applying 750 W of power to a niobium (Nb) target and forming a niobium (Nb) film by sputtering while flowing argon (Ar) gas at a flow rate of 12 SCCM, and then oxidizing the niobium (Nb) film by heat treatment at 150 °C for 10 minutes in air.

[0087] Next, a chromium nitride (CrN) film (Cr:N=4:1 (atomic ratio)) with a thickness of 45 nm was formed as an absorbing film on the etching stop film. The chromium nitride (CrN) film was formed by applying 1000 W of power to a chromium (Cr) target and supplying argon (Ar) gas at a flow rate of 20 SCCM and nitrogen (N 2 The film was formed by sputtering while flowing 10 SCCM of 1000 μm gas.

[0088] Moreover, a tantalum nitride (TaN) film having a thickness of 70 nm was formed as a conductive film on the other main surface of the substrate by sputtering to obtain a reflective mask blank.

[0089] A reflective mask was manufactured from the obtained reflective mask blank. First, an electron beam (EB) resist was applied onto the absorbing film to form a resist film, and a pattern was written on the resist film with an electron beam (EB) and developed to form a resist pattern having a line and space (L / S) pattern with a line width of 200 nm.

[0090] Next, using the resist pattern as an etching mask, chlorine (Cl 2 ) gas and oxygen (O 2 The absorbing film was patterned by dry etching using a gas containing Cl. 2 Flow rate: 185SCCM, O 2 The conditions were as follows: flow rate: 55 SCCM, He flow rate: 9.25 SCCM, pressure: 6 mTorr (0.8 Pa), ICP power: 400 W, RIE voltage: 700 V, overetching: 227 seconds (Example 1), 454 seconds (Example 2). At this stage, when the cross sections of the etched portions of the absorbing film were observed with a transmission electron microscope (TEM), the etching stop film remained at a thickness of 2 nm in both cases.

[0091] Next, the resist pattern was removed using sulfuric acid / hydrogen peroxide (SPM), and the etching stop film was also removed from the exposed area where the absorbing film had been removed, to obtain a reflective mask. When the cross section of the etched area of ​​the absorbing film was observed with a transmission electron microscope (TEM), the protective film remained undamaged, with a thickness of 3 nm in all cases. In addition, a good pattern of the absorbing film was obtained.

[0092] [Comparative Example 1] A reflective mask blank was obtained in the same manner as in Example 1, except that no etching stopper film was formed. Next, a resist pattern was formed in the same manner as in Example 1. Next, in the same manner as in Example 1, chlorine (Cl 2 ) gas and oxygen (O 2 The absorbing film was patterned by dry etching using a gas containing . The protective film was found to have disappeared when the cross section of the etched portion of the absorbing film was observed with a transmission electron microscope (TEM).

[0093] [Comparative Example 2] A reflective mask blank was obtained in the same manner as in Example 1, except that no etching stopper film was formed. Next, a resist pattern was formed in the same manner as in Example 1. Next, chlorine (Cl 2 ) gas and oxygen (O 2 The absorbing film was patterned by dry etching using a gas containing SiO 2 and SiO 2 gas to form an absorbing film pattern. When the cross section of the etched portion of the absorbing film was observed with a transmission electron microscope (TEM), it was confirmed that the absorbing film remained on the protective film in the area where the absorbing film should have been removed. In addition, because the line width dimension was not controlled by overetching, a good pattern of the absorbing film was not obtained. [Explanation of symbols]

[0094] 1 Board 10 Reflective mask 11, 12 Reflective mask blanks 2 Multilayer reflective film 3 Protective film 4. Etch stop film 41 Etch stop film pattern 5. Absorption membrane 51 Absorbing membrane pattern 6 Etching mask film

Claims

1. A reflective mask blank comprising: a substrate; a multilayer reflective film formed on one main surface of the substrate and reflecting exposure light; a protective film formed on the multilayer reflective film and protecting the multilayer reflective film; and an absorbing film formed on the protective film and absorbing exposure light, the mask blank being a material for a reflective mask used in EUV lithography in which EUV light is used as exposure light, The protective film contains ruthenium (Ru), Between the protective film and the absorbing film, there is further provided an etching stop film containing niobium (Nb) and not containing ruthenium (Ru). A reflective mask blank comprising:

2. 2. The reflective mask blank according to claim 1, wherein the etching stop film is made of niobium (Nb) alone or a niobium (Nb) compound containing niobium (Nb) and oxygen (O).

3. 2. The reflective mask blank according to claim 1, wherein the protective film is made of ruthenium (Ru).

4. 2. The reflective mask blank according to claim 1, wherein the absorbing film contains chromium (Cr).

5. 2. The reflective mask blank according to claim 1, wherein the absorbing film contains tantalum (Ta), and further comprises an etching mask film containing chromium (Cr) on the absorbing film.

6. 5. A method for producing a reflective mask, comprising the steps of: patterning the absorbing film of the reflective mask blank according to claim 4 by dry etching using a gas containing chlorine (Cl) and oxygen (O).

7. 6. A method for manufacturing a reflective mask, comprising the steps of: patterning the absorbing film of the reflective mask blank according to claim 5; and then removing the etching mask film by dry etching using a gas containing chlorine (Cl) and oxygen (O).

8. A method for producing a reflective mask from the reflective mask blank according to any one of claims 1 to 5, comprising the steps of: A method for manufacturing a reflective mask, comprising the steps of: forming a pattern of the absorbing film; and then removing the etching stop film from a portion exposed by removing the absorbing film.

9. 9. The method according to claim 8, further comprising removing the etching stopper film from the exposed portion of the absorbing film by using sulfuric acid / hydrogen peroxide (SPM).

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