Reflective mask blank and manufacturing method of reflective mask

Abstract

SOLUTION: To provide an etching mask film containing niobium (Nb) on 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, and the absorption film, which is formed on the multilayer reflection film and absorbs the exposure light, where the absorption film is composed of a material that undergoes dry etching using a gas containing oxygen (O), and it serves as a material for a reflective mask used in EUV lithography employing EUV light as the exposure source.EFFECT: A fine pattern can be properly formed from an absorption film to be patterned by dry etching using a gas containing 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] Tantalum (Ta)-based films are generally used for absorbing films, but in order to reduce the shadowing effect during exposure using a reflective mask and to increase the accuracy of pattern transfer onto the wafer, it is necessary to lower the pattern height, which corresponds to the film thickness of the absorbing film, i.e., to make the absorbing film thinner. For this reason, chromium (Cr)-based absorbing films, which can be made thinner than tantalum (Ta)-based absorbing films, have attracted attention.

[0009] Absorbing films such as chromium (Cr)-based films are patterned by dry etching using gas containing chlorine (Cl) and oxygen (O), but if a resist film is formed on the absorbing film, a resist pattern is formed from the resist film, and dry etching is performed using the resist pattern as an etching mask, the resist pattern is also etched in dry etching using gas containing oxygen (O), so the resist pattern (resist film) needs to be thick. However, if an attempt is made to form a fine resist pattern from a thick resist film, the aspect ratio becomes high and the resist pattern collapses, making it impossible to form a fine resist pattern and thus impossible to form a fine pattern of the absorbing film.

[0010] The present invention has been made to solve the above-mentioned problems, and has an object to provide a reflective mask blank capable of satisfactorily forming a fine absorbing film pattern from an absorbing film patterned by dry etching using a gas containing oxygen (O), and a method for manufacturing a reflective mask using the reflective mask blank. [Means for solving the problem]

[0011] As a result of extensive research into solving the above problems, the inventors have found that the above problems can be solved by providing an etching mask film containing niobium (Nb) on an absorbing film made of a material that is dry etched using a gas containing oxygen (O), particularly a gas containing chlorine (Cl) and oxygen (O), and have thus completed the present invention.

[0012] 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, and an absorbing film formed on the multilayer reflective film and absorbing the exposure light, the mask blank being a material for a reflective mask used in EUV lithography using EUV light as the exposure light, the absorbing film is made of a material that can be dry etched with a gas containing oxygen (O); On the absorption film, an etching mask film containing niobium (Nb) is provided. A reflective mask blank comprising: 2. The reflective mask blank according to 1, wherein the etching mask film containing niobium (Nb) 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 absorbing film contains chromium (Cr). 4. The reflective mask blank according to 1, wherein the absorbing film contains ruthenium (Ru). 5. A method for producing a reflective mask, comprising patterning the absorbing film of the reflective mask blank according to any one of 1 to 4 by dry etching using a gas containing oxygen (O). 6. The manufacturing method according to the method 5, characterized in that the etching mask film is patterned using a resist pattern as an etching mask to form an etching mask film pattern, and the absorbing film is patterned by dry etching using a gas containing oxygen (O) using the etching mask film pattern as an etching mask. 7. The manufacturing method according to claim 6, characterized in that after forming the pattern of the absorbing film, the pattern of the etching mask film is removed with sulfuric acid / hydrogen peroxide (SPM). Effect of the Invention

[0013] According to the present invention, a fine pattern can be successfully formed from an absorbing film that is patterned by dry etching using a gas containing oxygen (O). [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a reflective mask blank of the present invention. [Diagram 2] FIG. 1 is a cross-sectional view showing an example of a reflective mask of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will now be described in further detail. The reflective mask blank of the present invention has a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate for reflecting exposure light, and an absorbing film formed on the multilayer reflective film for absorbing exposure light. The reflective mask blank of the present invention also has an etching mask film on the absorbing film.

[0016] 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.

[0017] 1 is a cross-sectional view showing an example 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, an absorbing film 3 formed in contact with the multilayer reflective film 2, and an etching mask film 4 formed in contact with the absorbing film 3.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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. Furthermore, when the absorbing film is in contact with the multilayer reflective film and contains chromium (Cr) as described below, it is preferable that the layer (uppermost layer) of the periodic stacked structure that is farthest from the substrate is a silicon (Si) layer, since this increases the etching selectivity in dry etching of the absorbing film.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 2When 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 (CO 2 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.

[0027] 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.

[0028] The reflective mask blank of the present invention may have a protective film between the multilayer reflective film and the absorbing film for protecting the multilayer reflective film. 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 can also be provided in contact with the absorbing film or in contact with another film (such as an etching stop film described later) that is in contact with the absorbing film.

[0029] The protective film is formed of a material containing ruthenium (Ru). Examples of materials containing ruthenium (Ru) include ruthenium (Ru) alone, and alloys containing ruthenium (Ru) and a metal or metalloid 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 materials containing ruthenium (Ru), in particular, ruthenium (Ru) alone and alloys containing ruthenium (Ru) and niobium (Nb) are preferred. In addition, when an absorbing film made of a material containing chromium (Cr) is formed in contact with the protective film, it is preferable that the protective film is a film containing ruthenium (Ru) and niobium (Nb), because the etching selectivity in dry etching of the absorbing film is high. 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 other than ruthenium (Ru) in the protective film is not particularly limited, but is preferably 5 atomic % or more, and more preferably 10 atomic % or more, on average throughout the film.

[0030] 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).

[0031] 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.

[0032] In the present invention, the dry etching using a gas containing chlorine (Cl) and oxygen (O) is specifically a 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The absorbing film is made of a material that can be dry etched with a gas containing oxygen (O). The absorbing film is a film of a material that absorbs EUV light and can be patterned, and is preferably made of a material containing chromium (Cr) or a material containing ruthenium (Ru).

[0037] In the present invention, the dry etching using a gas containing oxygen (O) is 2 Dry etching using a gas containing oxygen (O 2 dry etching using a gas containing a halogen-containing gas and a gas containing oxygen (O) (specifically, oxygen (O2 Dry etching using halogen gas is preferred. Examples of halogen include chlorine (Cl) and fluorine (F). Examples of gases containing chlorine (Cl) include chlorine (Cl) and fluorine (F). 2 ) gas, hydrogen chloride (HCl) gas, etc., as gases that contain fluorine (F), carbon tetrafluoride (CF 4 ) gas, sulfur hexafluoride (SF 6 The gas containing oxygen (O) may contain a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0038] The material containing chromium (Cr) may contain oxygen (O), nitrogen (N), carbon (C), etc. Specific examples of the material containing chromium (Cr) include simple Cr and chromium (Cr) compounds such as CrO, CrN, CrON, CrC, CrCO, CrCN, and CrCON. Furthermore, the material containing chromium (Cr) may contain other elements as long as it can be dry etched with a gas containing oxygen (O). Note that the notation of the chemical formula of a metal or semimetal compound indicates the constituent elements of the compound, and does not mean the composition ratio of the elements. (The same applies below.)

[0039] The material containing ruthenium (Ru) may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Specific examples of the material containing ruthenium (Ru) include simple Ru and ruthenium (Ru) compounds such as RuO, RuN, RuON, RuC, RuCO, RuCN, RuCON, RuB, RuOB, RuNB, RuONB, RuCB, RuCOB, RuCNB, and RuCONB. Furthermore, the material containing ruthenium (Ru) may contain other elements as long as it can be dry etched with a gas containing oxygen (O).

[0040] The etching selectivity of the absorbing film to the protective film is preferably 3 or more, more preferably 5 or more. The sheet resistance of the absorbing film is preferably 1×10 6 Ω / □ or less, more preferably 1×10 5The surface roughness Sq of the absorbing film is preferably 0.8 nm or less, and more preferably 0.6 nm or less.

[0041] The absorbing film (each layer constituting the absorbing film) can be formed by sputtering, and the magnetron sputtering method is preferable. Specifically, when the absorbing film is formed from a material containing chromium (Cr), a chromium (Cr) target or a chromium (Cr) compound target (a target containing chromium (Cr) and oxygen (O), nitrogen (N), carbon (C), etc.) is used, and when the absorbing film is formed from a material containing ruthenium (Ru), a ruthenium (Ru) target or a ruthenium (Ru) compound target (a target containing ruthenium (Ru) and oxygen (O), nitrogen (N), carbon (C), boron (B), etc.) is used according to the composition. Sputtering using rare gases such as helium (He) gas, neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, and xenon (Xe) gas as the sputtering gas, or oxygen-containing gas, nitrogen-containing gas, and carbon-containing gas, specifically oxygen (O), is used. 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 fluoride (NO3) gas.

[0042] An etching mask film having etching characteristics different from those of the absorbing film is provided on the absorbing film on the side away from the substrate as a hard mask for the absorbing film. In the present invention, the etching mask film contains niobium (Nb). Niobium (Nb) forms niobium oxide (NbO) during dry etching using a gas containing oxygen (O). Niobium oxide (NbO) has resistance to dry etching using a gas containing oxygen (O).

[0043] The etching mask film functions as a hard mask when the absorbing film is dry-etched using a gas containing oxygen (O). Therefore, it is preferable that the etching mask film does not contain the metal or semimetal elements contained in the absorbing film, specifically, chromium (Cr) or ruthenium (Ru). It is preferable that the etching mask film is provided in contact with the absorbing film. The etching mask film may be a single layer or a multilayer.

[0044] The etching mask 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.

[0045] 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.

[0046] The etching mask film containing niobium (Nb) 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 mask film contains oxygen (O), it is preferable to increase the oxygen (O) concentration on the front side (side away from the substrate), or to make the front 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).

[0047] In the present invention, the dry etching using a gas containing chlorine (Cl) is specifically, 2 Dry etching using a gas containing fluorine (F) gas is specifically exemplified by carbon tetrafluoride (CF 4 ) gas and sulfur hexafluoride (SF 6 Dry etching using a gas containing chlorine (Cl) gas is an example. The gas containing chlorine (Cl) preferably does not contain a gas containing oxygen (O). The gas containing chlorine (Cl) and the gas containing fluorine (F) may contain a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0048] 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.

[0049] 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 is preferably 20 nm or less, more preferably 10 nm or less.

[0050] The etching mask film can be formed by sputtering. The etching mask film can be formed by sputtering using a niobium (Nb) target and, if necessary, a niobium (Nb) compound target (a target containing niobium (Nb) and oxygen (O), nitrogen (N), carbon (C), boron (B), or the like) 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), together with the rare gas. 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.

[0051] When the etching mask 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.

[0052] In addition, another etching mask film (second etching mask film) that functions as a hard mask in etching the etching mask film (first etching mask film) containing niobium (Nb) may be provided on the etching mask film containing niobium (Nb), preferably in contact with the etching mask film containing niobium (Nb). As the second etching mask film, an etching mask film containing chromium (Cr) may be mentioned.

[0053] The reflective mask blank of the present invention may have an etching stopper between the protective film and the absorbing film. The etching stopper is a film that protects the protective film and prevents etching of the protective film in dry etching using a gas containing oxygen (O), particularly a gas containing chlorine (Cl) and oxygen (O). Therefore, the etching stopper functions as an etching stopper against dry etching using a gas containing oxygen (O), particularly a gas containing chlorine (Cl) and oxygen (O). The etching stopper preferably contains niobium (Nb) or tantalum (Ta). An etching stopper containing niobium (Nb) or tantalum (Ta) is not etched by dry etching using a gas containing oxygen (O), particularly a gas containing chlorine (Cl) and oxygen (O), so that damage to the protective film can be prevented.

[0054] 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 (back surface) of the substrate, which is the surface opposite to the one main surface, preferably in contact with the other main surface.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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, and an absorbing film pattern (absorbing film pattern) formed in contact with the multilayer reflective film 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.

[0059] 2 is a cross-sectional view showing an example of a reflective mask of the present invention. This reflective mask 10 includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1 in contact with the substrate 1, and an absorbing film pattern 31 formed in contact with the multilayer reflective film 2.

[0060] The reflective mask of the present invention 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; A process for removing the pattern of the etching mask film. The composition can be produced by a method comprising the steps of:

[0061] An etching mask film containing niobium (Nb) can be etched by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F).

[0062] The absorbing film is patterned by dry etching using a gas containing oxygen (O). When the absorbing film is dry etched using a gas containing oxygen (O), the etching mask film containing niobium (Nb) is not etched by the gas containing oxygen (O), so the pattern of the etching mask film functions as a hard mask in the dry etching using the gas containing oxygen (O).

[0063] When a separate etching mask film (second etching mask film) that functions as a hard mask in etching an etching mask film (first etching mask film) containing niobium (Nb) is provided, the second etching mask film is etched using the resist pattern as an etching mask to form a pattern of the second etching mask film, and the first etching mask film is etched using the pattern of the second etching mask film as an etching mask to form a pattern of the first etching mask film.

[0064] When the second etching mask film is an etching mask film containing chromium (Cr), the pattern of the second etching mask film can be formed by dry etching using a gas containing chlorine (Cl) and oxygen (O). In this case, if the absorbing film is made of a material containing chromium (Cr), the pattern of the second etching mask film can be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O) at the same time as patterning the absorbing film by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0065] The absorbing film formed of a material containing chromium (Cr) can be etched by dry etching using a gas containing chlorine (Cl) and oxygen (O). The absorbing film formed of a material containing ruthenium (Ru) can be etched by dry etching using a gas containing oxygen (O). 2 The etching can be performed by dry etching using a gas containing a rare gas (N) gas and not containing any gas other than a rare gas, or by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0066] By etching the etching mask film using the resist pattern as an etching mask to form a pattern of the etching mask film, and then patterning the absorbing film by dry etching using a gas containing oxygen (O) using the pattern of the etching mask film as an etching mask to form a pattern of the absorbing film, it is possible to make the resist pattern (resist film) thinner and to form a finer pattern well, as compared with the case where the resist pattern is directly formed on the absorbing film, and then patterning the absorbing film by dry etching using a gas containing oxygen (O) using the resist pattern as an etching mask to form a pattern of the absorbing film.

[0067] Resist patterns and patterns of etching mask films containing niobium (Nb) can be removed by sulfuric acid / hydrogen peroxide (SPM).

[0068] The pattern of the etching mask film containing niobium (Nb) can also be removed by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F), but when niobium (Nb) is exposed to a gas containing oxygen (O), it is oxidized to form niobium oxide (NbO). Since niobium oxide (NbO) is difficult to remove by dry etching using a gas containing chlorine (Cl) or a gas containing fluorine (F), it is preferable to remove the pattern of the etching mask film containing niobium (Nb) with sulfuric acid / hydrogen peroxide (SPM). In that case, the pattern of the etching mask film containing niobium (Nb) can be removed continuously with the removal of the resist pattern.

[0069] 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

[0070] 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.

[0071] [Example 1] 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 a 3 nm thick molybdenum (Mo) layer and a 4 nm thick silicon (Si) layer being one pair (period), with the top layer being a 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°.

[0072] 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 protective 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.

[0073] Next, a 2 nm thick niobium oxide (NbO) film (Nb:O = 2:5 (atomic ratio)) was formed on the absorbing film as an etching mask 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.

[0074] 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.

[0075] A reflective mask was manufactured from the obtained reflective mask blank. First, an electron beam (EB) resist was applied onto the etching mask film to form a resist film with a thickness of 90 nm, 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 50 nm.

[0076] Next, the resist pattern is used as an etching mask to etch sulfur hexafluoride (SF 6 The etching mask film was patterned by dry etching using a gas containing SF 6 The experiment was carried out under the following conditions: flow rate: 18 SCCM, He flow rate: 130 SCCM, pressure: 5 mTorr (0.67 Pa), ICP power: 325 W, RIE voltage: 190 V.

[0077] Next, the etching mask film pattern is used as an etching mask to etch 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, and RIE voltage: 700 V.

[0078] Next, the remaining resist pattern and the etching mask film pattern were removed with sulfuric acid / hydrogen peroxide (SPM) to obtain a reflective mask. A fine absorbing film pattern with a line width of 50 nm was well formed on the obtained reflective mask.

[0079] [Comparative Example 1] A reflective mask blank was obtained in the same manner as in Example 1, except that no etching mask film was formed. Next, a resist pattern was formed directly on the absorbing film in the same manner as in Example 1. Next, chlorine (Cl 2 ) gas and oxygen (O 2 ) gas, an attempt was made to form a pattern of the absorbing film by patterning the absorbing film by dry etching using a gas containing a fluorine-containing gas, but the resist pattern disappeared before the pattern of the absorbing film was formed, and it was not possible to form a pattern of the absorbing film. [Explanation of symbols]

[0080] 1 Board 10 Reflective mask 11 Reflective mask blanks 2 Multilayer reflective film 3. Absorption membrane 31 Absorbing membrane pattern 4 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, and an absorbing film formed on the multilayer reflective film and absorbing the exposure light, the mask blank being a material for a reflective mask used in EUV lithography using EUV light as exposure light, the absorbing film is made of a material that can be dry etched with a gas containing oxygen (O); An etching mask film containing niobium (Nb) is provided on the absorbing film. A reflective mask blank comprising:

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

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

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

5. A method for producing a reflective mask, comprising patterning the absorbing film of the reflective mask blank according to any one of claims 1 to 4 by dry etching using a gas containing oxygen (O).

6. 6. The manufacturing method according to claim 5, further comprising the steps of: patterning the etching mask film using a resist pattern as an etching mask to form a pattern of the etching mask film; and patterning the absorbing film by dry etching using a gas containing oxygen (O) using the pattern of the etching mask film as an etching mask.

7. 7. The method according to claim 6, wherein after the absorbing film pattern is formed, the etching mask film pattern is removed with sulfuric acid / hydrogen peroxide (SPM).

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