Method for manufacturing reflective mask blanks and reflective masks

Abstract

This invention provides a reflective mask blank that does not damage the protective film during mask processing, and a method for manufacturing a reflective mask using the reflective mask blank. [Solution] The reflective mask blank 100 of the present invention is a reflective mask blank 100 that serves as the material for a reflective mask 110 used in EUV lithography, which uses EUV light as the exposure light. The reflective mask blank 100 includes a substrate 1, a multilayer reflective film 2 that reflects exposure light formed on one main surface of the substrate 1, a protective film 3 that protects the multilayer reflective film 2 formed on the multilayer reflective film 2, an absorption film 6 that absorbs exposure light formed above the protective film 3, and interlayer films 4 and 5 provided between the protective film 3 and the absorption film 6. The interlayer films 4 and 5 include a first interlayer film 4 containing niobium (Nb) and a second interlayer film 5 provided on the side of the absorption film 6 that is closer to the first interlayer film 4, and made of a material that can be dry-etched with an oxygen-containing gas. The absorption film 6 is made of a material that can be dry-etched with a fluorine-containing gas.

Description

Technical Field

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

Background Art

[0002] In the manufacturing process of semiconductor devices (semiconductor apparatuses), photolithography technology is repeatedly used in which exposure light is irradiated onto a transfer mask, and a circuit pattern formed on the mask is transferred onto a semiconductor substrate (semiconductor wafer) through a reduction projection optical system. Conventionally, the wavelength of the exposure light has been mainly 193 nm using argon fluoride (ArF) excimer laser light, and by adopting a process called multi-patterning in which a plurality of exposure processes and processing processes are combined, ultimately, patterns having dimensions smaller than the exposure wavelength have been formed.

[0003] However, due to the continuous miniaturization of device patterns, further formation of fine patterns has been required, and thus, extreme ultraviolet (Extreme Ultraviolet, hereinafter referred to as "EUV") lithography technology using EUV light having a wavelength shorter than that of ArF excimer laser light has come to be used. EUV light is light having a wavelength of about 0.2 to 100 nm, more specifically, light having a wavelength near 13.5 nm. Since EUV light has extremely low permeability to substances and conventional transmissive projection optical systems and masks cannot be used, reflective optical elements are used. Therefore, reflective masks are also used as masks for pattern transfer.

[0004] A reflective mask is constructed by forming a multilayer reflective film that reflects EUV light on a substrate, and then forming a pattern of an absorbing film that absorbs EUV light on top of the multilayer reflective film. On the other hand, the state before the absorbing film is patterned (including the state where a resist film has been 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 that includes a substrate with low thermal expansion, 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 on top of it.

[0005] As a multilayer reflective film, a multilayer reflective film is typically used that obtains the required reflectivity for EUV light by alternately stacking molybdenum (Mo) layers and silicon (Si) layers. On the other hand, as an absorbing film, tantalum (Ta), which has a relatively large extinction coefficient for EUV light, is used (Japanese Patent Publication No. 2002-246299 (Patent Document 1)).

[0006] Furthermore, a ruthenium (Ru) film or rhodium (Rh) film, as disclosed in Japanese Patent Publication No. 2002-122981 (Patent Document 2) and Japanese Patent Publication No. 2005-516182 (Patent Document 3), is formed on the multilayer reflective film as a protective film (capping film) to protect the multilayer reflective film during cleaning of the reflective mask, etc. In addition, a hard mask film containing chromium (Cr) may be formed on the absorption film as an etching mask when forming patterns on the absorption film. On the other hand, a conductive film is formed on the other main surface of the substrate. As a conductive film, metal nitride films have been proposed for electrostatic chucking, and films mainly containing chromium (Cr) and tantalum (Ta) are examples. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-246299 [Patent Document 2] Japanese Patent Publication No. 2002-122981 [Patent Document 3] Japanese Patent Publication No. 2002-516182 [Overview of the project] [Problems that the invention aims to solve]

[0008] Conventionally, in EUV exposure masks, a Ta-based absorption film of about 70 nm or 60 nm has been used as the light-shielding film. However, there is a demand for thinner absorption films to reduce the 3D effect of the mask during EUV exposure, and various materials have been proposed. However, even if a material exhibits better optical properties than conventional Ta-based absorption films, problems have arisen such as damage to the protective film during mask processing due to the slow etching rate during mask processing.

[0009] This invention was made to solve the above problems, and aims to provide a reflective mask blank that does not damage the protective film during mask processing, and a method for manufacturing a reflective mask using the reflective mask blank.

[0010] The inventors of this invention, after diligent research to solve the above problems, have found that when using an absorption film that can be etched with a fluorine-containing gas, the above problems can be solved by providing at least two intermediate films between the protective film and the absorption film, the protective film having a layer containing niobium (Nb) and the absorption film having a layer made of a material that can be etched with an oxygen-containing gas. This led to the present invention. [Means for solving the problem]

[0011] Accordingly, the present invention provides the following reflective mask blanks and methods for manufacturing reflective masks.

[0012] [Concept 1] The reflective mask blank according to the present invention is A reflective mask blank that serves as the material for a reflective mask used in EUV lithography, which uses EUV light as the exposure light, circuit board and A multilayer reflective film that reflects exposure light is formed on one of the main surfaces of the substrate, A protective film formed above the multilayer reflective film to protect the multilayer reflective film, An absorption film that absorbs exposure light is formed above the protective film, An intermediate film provided between the protective film and the absorbing film, Equipped with, The interlayer comprises a first interlayer containing niobium (Nb) and a second interlayer provided on the absorption layer side of the first interlayer and made of a material that can be dry-etched with an oxygen-containing gas. The absorption film may be formed from a material that can be dry-etched with a fluorine-containing gas.

[0013] [Concept 2] In a reflective mask blank according to Concept 1, The first interlayer film may consist of niobium (Nb) alone, a niobium (Nb) compound containing niobium (Nb) and oxygen (O), or a multilayer film of a combination thereof.

[0014] [Concept 3] In a reflective mask blank according to Concept 1 or 2, The second interlayer may contain at least one selected from ruthenium (Ru), chromium (Cr), vanadium (V), and molybdenum (Mo).

[0015] [Concept 4] In a reflective mask blank based on any one of concepts 1 to 3, The absorption film may contain at least one selected from tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), and gold (Au).

[0016] [Concept 5] In a reflective mask blank based on any one of concepts 1 to 4, The second interlayer contains ruthenium (Ru), The absorption film may contain platinum (Pt).

[0017] [Concept 6] In a reflective mask blank according to any one of Concepts 1 to 4, the second intermediate film contains chromium (Cr), the absorption film may contain platinum (Pt).

[0018] [Concept 7] In a reflective mask blank according to any one of Concepts 1 to 6, an etching mask film containing chromium (Cr) may further be provided on the absorption film.

[0019] [Concept 8] A method for manufacturing a reflective mask from a reflective mask blank according to any one of Claims 1 to 7, pattern etching the absorption film by dry etching using a gas containing fluorine, pattern etching the second intermediate film by dry etching using a gas containing oxygen, pattern etching the first intermediate film with sulfuric acid peroxide (SPM), may be provided. [Advantages of the Invention]

[0020] According to the present invention, a first intermediate film containing niobium (Nb) is provided on the side of the protective film between the absorption film and the protective film that can be dry-etched using a gas containing fluorine, and a second intermediate film that can be dry-etched using a gas containing oxygen (O) is provided on the side of the absorption film, so that when manufacturing a reflective mask, it is difficult for the protective film to be damaged, and a reflective mask blank capable of suppressing a decrease in the thickness and oxidation of the protective film can be provided. [Brief Description of the Drawings]

[0021] [Figure 1] A cross-sectional view showing an example (first aspect) of a reflective mask blank according to an embodiment of the present invention. [Figure 2]A cross-sectional view showing another example (second aspect) of a reflective mask blank according to an embodiment of the present invention. [Figure 3] A cross-sectional view showing an example of a reflective mask according to an embodiment of the present invention. [Figure 4] A cross-sectional view showing yet another example (third aspect) of a reflective mask blank according to an embodiment of the present invention. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described in more detail below.

[0023] As shown in Figure 1, the reflective mask blank 100 of this embodiment includes a substrate 1, a multilayer reflective film 2 that reflects exposure light formed on one main surface (surface) of the substrate 1, a protective film 3 formed on the multilayer reflective film 2, and an absorption film 6 that absorbs exposure light formed above the protective film 3. Furthermore, the reflective mask blank 100 of this embodiment has a first interlayer film 4 and a second interlayer film 5 between the protective film 3 and the absorption film 6.

[0024] The reflective mask blank 100 is suitable as a material for the reflective mask 110 (see Figure 3) used in EUV lithography, which uses EUV light as the exposure light. The wavelength of the EUV light used in EUV lithography is 13-14 nm, and is typically around 13.5 nm. The reflective mask blank 100 and the reflective mask 110, which use EUV light as the exposure light, are also called EUV mask blanks and EUV masks, respectively.

[0025] Figure 1 is a cross-sectional view showing an example (first aspect) of the reflective mask blank 100 of this embodiment. This reflective mask blank 100 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, and an absorbent film 6 formed above the protective film 3. A first interlayer film 4 and a second interlayer film 5 are provided between the protective film 3 and the absorbent film 6.

[0026] The substrate 1 is preferably made of materials with low thermal expansion properties for use in EUV light exposure, for example, a thermal expansion coefficient of ±2 × 10 -8 Within / ℃, preferably ±5 × 10 -9 It is preferable that the substrate 1 be made of a material within the range of / ℃. Examples of such materials include titania-doped quartz glass (SiO2-TiO2 glass). Furthermore, it is preferable that the substrate 1 be made of a material with a sufficiently flat surface, and the surface roughness of the main surface of the substrate 1 is preferably 0.5 nm or less, more preferably 0.2 nm or less, in RMS value. Such surface roughness can be obtained by polishing the substrate 1. The size of the substrate 1 is preferably 152 mm square for the main surface and 6.35 mm thick. A substrate 1 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).

[0027] The multilayer reflective film 2 is a film that reflects exposure light in the reflective mask 110 (see Figure 3). The multilayer reflective film 2 is preferably provided in contact with one main surface of the substrate 1, but other films such as an undercoat may be provided between it and one main surface of the substrate 1. As shown in Figure 4, the multilayer reflective film 2 has a periodic stacked structure in which a high refractive index layer 21 with a relatively high refractive index with respect to exposure light and a low refractive index layer 22 with a relatively low refractive index with respect to exposure light are alternately stacked.

[0028] The high refractive index layer 21 is preferably made of a material containing silicon (Si). The high refractive index layer 21 may also 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 of a layer containing additive elements and a layer not containing additive elements. The thickness of the high refractive index layer 21 is preferably 3.5 nm or more, more preferably 4 nm or more, and preferably 4.9 nm or less, more preferably 4.4 nm or less.

[0029] The low refractive index layer 22 is preferably formed from a material containing molybdenum (Mo). Alternatively, the low refractive index layer 22 may be formed from a material containing ruthenium (Ru). A multilayer structure of Mo and Ru is also acceptable. The low refractive index layer 22 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 of a layer containing additive elements and a layer not containing additive elements. The thickness of the low refractive index layer 22 is preferably 2.1 nm or more, more preferably 2.6 nm or more, and preferably 3.5 nm or less, more preferably 3 nm or less.

[0030] The periodic stacked structure only needs to include a high refractive index layer 21 and a low refractive index layer 22, and each period should contain one or more high refractive index layers 21 and one or more low refractive index layers 22. The number of layers included in the periodic stacked structure is two or more, and the periodic stacked structure can be composed of, for example, one high refractive index layer 21 and one low refractive index layer 22. Furthermore, it may include two or more high refractive index layers 21 with different compositions (for example, different composition ratios, different compositions due to the presence or absence of additive elements, etc.) and two or more low refractive index layers 22 with different compositions (for example, different composition ratios, different compositions due to the presence or absence of additive elements, etc.). In this case, the number of layers included in the periodic stacked structure is three or more, and may be four or more or five or more, but is preferably eight or less. The number of periods is preferably 20 or more, preferably 50 or less, and more preferably 40 or less.

[0031] The thickness of the multilayer reflective film 2 having a periodic stacked structure is adjusted according to the exposure wavelength and the angle of incidence of the exposure light, but is preferably 130 nm or more, 400 nm or less, and more preferably 290 nm or less.

[0032] Methods for forming the multilayer reflective film 2 include sputtering, which involves supplying power to a target to plasmaize (ionize) the atmospheric gas and perform sputtering, and ion beam sputtering, which involves irradiating the target with an ion beam. Sputtering methods include DC sputtering, which applies a DC voltage to the target, and RF sputtering, which applies a high-frequency voltage to the target. Sputtering is a film deposition method that utilizes the sputtering phenomenon caused by gas ions, by applying a voltage to the target while sputtering gas is introduced into a chamber, thereby ionizing the gas. Magnetron sputtering, in particular, offers advantages in terms of productivity. The power applied to the target can be DC or RF, and DC sputtering also includes pulse sputtering, where the negative bias applied to the target is briefly reversed to prevent charge-up of the target.

[0033] The multilayer reflective film 2 can be formed by sputtering, for example, using a sputtering apparatus that can be equipped with multiple targets. Specifically, the target can be appropriately selected from a molybdenum (Mo) target for forming a molybdenum (Mo) layer, a ruthenium (Ru) target for forming a ruthenium (Ru) layer, a silicon (Si) target for forming a silicon (Si) layer, etc., and the sputtering gas can be a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0034] Furthermore, when sputtering is performed as reactive sputtering using a reactive gas, for example, when forming a film containing nitrogen (N), a nitrogen-containing gas such as nitrogen (N2) gas should be used; when forming a film containing oxygen (O), an oxygen-containing gas such as oxygen (O2) gas should be used; when forming a film containing nitrogen (N) and oxygen (O), nitrogen oxide gases such as nitrous oxide (N2O), nitric oxide (NO), and nitrogen dioxide (NO2) gas should be used; when forming a film containing carbon (C) and oxygen (O), carbon oxide gases such as carbon monoxide (CO) gas and carbon dioxide (CO2) gas should be used; when forming a film containing hydrogen (H), a hydrogen-containing gas such as hydrogen (H2) gas should be used; and when forming a film containing carbon (C) and hydrogen (H), a hydrocarbon gas such as methane (CH4) gas should be used, along with a noble gas.

[0035] Furthermore, when forming a boron (B)-containing layer, boron (B)-doped molybdenum (Mo) targets (molybdenum boride (MoB) targets), boron (B)-doped silicon (Si) targets (silicon boride (SiB) targets), etc., can be used.

[0036] The protective film 3 is also called the capping film. The protective film 3 is a film that protects the multilayer reflective film 2. The protective film 3 is usually provided in contact with the multilayer reflective film 2. The protective film 3 is made of a material containing ruthenium (Ru) or rhodium (Rh).

[0037] Materials containing ruthenium (Ru) include elemental ruthenium (Ru), and alloys consisting of ruthenium (Ru) and a metal or metalloid other than ruthenium (Ru). Examples of metals or metalloids other than ruthenium (Ru) include rhodium (Rh), niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr), and silicon (Si). Among materials containing ruthenium (Ru), elemental ruthenium (Ru) is particularly preferred, and the protective film 3 is preferably made of ruthenium (Ru). The content of a metal or metalloid other than ruthenium (Ru) in the protective film 3 is preferably 50 atomic% or less, more preferably 30 atomic% or less, on average for the entire film. The lower limit of the content of a metal or metalloid other than ruthenium (Ru) in the protective film 3 is not particularly limited, but is preferably 5 atomic% or more, more preferably 10 atomic% or more.

[0038] Materials containing rhodium (Rh) include elemental rhodium (Rh), and alloys consisting of rhodium (Rh) and a metal or metalloid other than rhodium (Rh). Examples of metals or metalloids other than rhodium (Rh) include ruthenium (Ru), niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr), and silicon (Si). Among materials containing rhodium (Rh), elemental rhodium (Rh) is particularly preferred, and the protective film 3 is preferably made of rhodium (Rh). The content of a metal or metalloid other than rhodium (Rh) in the protective film 3 is preferably 50 atomic% or less, more preferably 30 atomic% or less, on average for the entire film. The lower limit of the content of a metal or metalloid other than rhodium (Rh) in the protective film 3 is not particularly limited, but is preferably 5 atomic% or more, more preferably 10 atomic% or more.

[0039] The protective film 3 may be a single-layer structure or a multilayer structure combining multiple layers with different compositions, 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.

[0040] The thickness of the protective film 3 is preferably 1 nm or more, more preferably 2 nm or more, and also preferably 5 nm or less, more preferably 4 nm or less.

[0041] The protective film 3 can be formed by sputtering using a target appropriately selected from ruthenium (Ru) target, rhodium (Rh) target, or a target of a different metal or metalloid, specifically a niobium (Nb) target, rhenium (Re) target, zirconium (Zr) target, titanium (Ti) target, chromium (Cr) target, silicon (Si) target, or a target made by mixing two or more of ruthenium (Ru), niobium (Nb), rhenium (Re), zirconium (Zr), titanium (Ti), chromium (Cr), and silicon (Si), and using a rare gas such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas. Magnetron sputtering is preferred for sputtering.

[0042] The absorption film 6 is a film in the reflective mask 110 that absorbs exposure light and reduces reflectivity. In the reflective mask 110, the transfer pattern is formed by the difference in reflectivity between the areas where the absorption film 6 is formed and the areas where the absorption film 6 is not formed. The absorption film 6 may be a single layer or a multilayer, and an anti-reflective layer or the like may be formed on its surface.

[0043] The absorption film 6 is a film of a material that absorbs EUV light and, in this embodiment, can be patterned by dry etching using a fluorine-containing gas. It is preferable that the main component be one or more of tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), or gold (Au), or a mixture of two or more of these. Examples include elemental tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), and gold (Au), as well as alloys and mixtures such as platinum-ruthenium (PtRu), platinum-iridium (PtIr), and ruthenium-iridium (RuIr). In this embodiment, "main component" means the metallic or metalloid element that is present in the highest atomic percentage.

[0044] Materials containing tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), or gold (Au), or a mixture of two or more of these, may also contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc.

[0045] The absorption film 6 (each layer constituting the absorption film 6) can be formed by sputtering, and the sputtering method is preferably magnetron sputtering. Specifically, when forming with a material containing platinum (Pt), a platinum (Pt) target or a platinum (Pt) mixed target (a target containing platinum (Pt) and oxygen (O), nitrogen (N), carbon (C), boron (B), etc.) can be used. When forming with a material containing iridium (Ir), an iridium (Ir) target or an iridium (Ir) mixture target (a target containing iridium (Ir) and oxygen (O), nitrogen (N), carbon (C), boron (B), etc.) can be used. Alternatively, a gold (Au) target or a gold (Au) mixture target (a target containing gold (Au) and oxygen (O), nitrogen (N), The material can be formed by sputtering using a target containing carbon (C), boron (B), etc., with the target appropriately selected according to its composition, and using noble gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) as the sputtering gas. Alternatively, it can be formed by reactive sputtering using reactive gases such as oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases, specifically oxygen (O2), nitrogen (N2), nitrogen oxide (N2O, NO, NO2), and carbon oxide (CO, CO2) gases, along with the noble gas. The material can also be formed using a similar method when using materials containing tantalum (Ta) or rhodium (Rh).

[0046] The thickness of the absorption film 6 is not particularly limited, as the optimal thickness varies depending on the light source and pattern pitch during exposure, but it is preferably 20 nm or more, more preferably 30 nm or more, and also preferably 60 nm or less, more preferably 50 nm or less.

[0047] In this embodiment, specific examples of dry etching using a gas containing fluorine (F) include dry etching using gases containing carbon tetrafluoride (CF4), sulfur hexafluoride (SF) gas, or ethane hexafluoride (C2F6) gas. The gas containing fluorine (F) may be mixed with noble gases such as helium (He) gas, argon (Ar) gas, krypton (Kr) gas, or xenon (Xe) gas.

[0048] If an absorption film 6 that can be dry-etched with a fluorine-containing gas is directly laminated on top of a protective film 3, the protective film 3 will also be exposed to dry etching with the fluorine-containing gas when the absorption film 6 is etched. Ruthenium (Ru) and rhodium (Rh), which are commonly used as protective films 3, are etched by dry etching with a fluorine-containing gas, so the protective film 3 will be damaged during over-etching when etching the absorption film 6. To prevent this, a first interlayer 4 containing Nb is placed on the protective film 3 side (downward), and a second interlayer 5 made of a material that can be etched with an oxygen-containing gas is placed on the absorption film 6 side (upward). This allows the absorption film 6, which is etched with a fluorine-containing gas, to be etched without damaging the protective film 3.

[0049] The first interlayer 4 is a niobium (Nb)-containing film. The niobium (Nb)-containing film is resistant to dry etching using an oxygen (O)-containing gas and functions as a protective film for the protective film 3.

[0050] The first interlayer 4 is preferably made of pure niobium (Nb) or a compound made of niobium (Nb) containing niobium (Nb) and oxygen (O), for example, it may be made of niobium oxide (NbO). The niobium (Nb) compound containing oxygen (O) preferably has niobium (Nb) and oxygen (O) as its main components, 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 for the entire film. In addition, the niobium (Nb) content is preferably 20 atomic% or more, more preferably 28 atomic% or more, and even more preferably 29 atomic% or more on average for the entire film.

[0051] The first interlayer 4 may be a single layer or multiple layers. Examples of multiple layers include combinations of layers containing niobium (Nb) with different compositions or composition ratios, such as a combination of a layer made of an oxygen (O)-containing niobium (Nb) compound and a layer made of niobium (Nb), or a combination of niobium (Nb) compound layers with different composition ratios of oxygen (O). Furthermore, each layer may be a single-composition layer or a gradient-composition layer having a gradient composition. If the first interlayer 4 contains oxygen (O), it is preferable to increase the oxygen (O) concentration on the front side (the side away from the substrate 1), or to make the front side a layer made of an oxygen (O)-containing niobium (Nb) compound and the substrate 1 side (back side) a layer made of niobium (Nb) or a layer containing niobium (Nb) but not oxygen (O).

[0052] The thickness of the first interlayer 4 should be such that it can protect the protective film 3 during dry etching of the second interlayer 5 with an oxygen-containing gas, preferably 0.5 nm or more, more preferably 1 nm or more, and also preferably 10 nm or less, more preferably 5 nm or less.

[0053] The first interlayer 4 can be formed by sputtering. The first interlayer 4 can be formed by sputtering using a niobium (Nb) target and, if necessary, a target of a different metal or metalloid from niobium (Nb), specifically a silicon (Si) target, as the target, and noble gases such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe) as the sputtering gas, or by reactive sputtering using oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases, specifically oxygen (O2), nitrogen (N2), nitrogen oxide (N2O, NO, NO2), and carbon oxide (CO, CO2) gases, along with noble gases. Magnetron sputtering is preferred for sputtering.

[0054] If the first interlayer 4 contains oxygen (O), niobium (Nb) is readily oxidized. Therefore, a film of elemental niobium (Nb) can be formed and oxidized by exposing it to an oxygen-containing atmosphere such as air to obtain an oxygen-containing niobium (Nb) compound. When oxidizing a film of elemental niobium (Nb), the film may be heat-treated.

[0055] The second interlayer 5 is made of a material that can be dry-etched with an oxygen-containing gas.

[0056] Materials that can be dry-etched with oxygen-containing gases include those containing ruthenium (Ru), chromium (Cr), vanadium (V), molybdenum (Mo), etc. Other elements may also be present; the material must be able to be dry-etched with oxygen-containing gases. Examples include Ru, RuO, RuN, RuON, Cr, CrO, CrN, CrON, V, Mo, MoO, etc.

[0057] The thickness of the second interlayer 5 is set to such a thickness that the second interlayer 5 is not completely etched when etching the absorption film 6, which can be etched with a gas containing fluorine gas.

[0058] After etching the absorption film 6 is complete, etching the second interlayer film 5 with an oxygen-containing gas causes the first interlayer film 4 to appear on the surface of the patterned area.

[0059] Since the first interlayer film 4, which is mainly composed of Nb or NbO, dissolves easily in sulfuric acid peroxide washing (SPM), when it is desired to remove the first interlayer film 4 in the patterning section and expose the protective film 3 on the surface, this can be achieved by performing SPM washing, and in this case, the mask can be manufactured without damaging the protective film 3.

[0060] As shown in Figure 4, a conductive film (conductive film) 50 may be provided on the other main surface (back surface) of the substrate 1, which is the surface opposite to one of the main surfaces, preferably in contact with the other main surface, for electrostatically chucking the reflective mask 110 to an exposure apparatus (e.g., an EUV scanner).

[0061] The conductive film 50 preferably has a sheet resistance of 100 Ω / □ or less, and there are no particular restrictions on the material. Examples of materials for the conductive film 50 include materials containing tantalum (Ta) or chromium (Cr). Furthermore, materials containing tantalum (Ta) may also contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc., and materials containing chromium (Cr) may also contain oxygen (O), nitrogen (N), carbon (C), etc. Examples of materials containing tantalum (Ta) include elemental Ta, TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, TaCONB, and other tantalum (Ta) compounds. Specific examples of materials containing chromium (Cr) include elemental Cr, CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, and other chromium (Cr) compounds.

[0062] The thickness of the conductive film 50 is not particularly limited, as long as it functions for electrostatic chucks, but is usually around 20 to 300 nm. Preferably, the thickness of the conductive film 50 is formed so that the film stress is balanced with the film and film pattern formed on one main surface (surface) side after it has been formed as a reflective mask 110, that is, after the pattern of the absorption film 6 has been formed. The conductive film 50 may be formed before forming the multilayer reflective film 2, or after all the films on the multilayer reflective film 2 side of the substrate 1 have been formed. Alternatively, the conductive film 50 may be formed after a portion of the films on the multilayer reflective film 2 side of the substrate 1 has been formed, and then the remaining films on the multilayer reflective film 2 side of the substrate 1 may be formed. The conductive film 50 can be formed, for example, by magnetron sputtering.

[0063] As shown in Figure 2, an etching mask film 7 with different etching characteristics from the absorption film 6 can be provided on the side of the absorption film 6 that is separated from the substrate 1, as a hard mask film for etching the absorption film 6. Preferably, the etching mask film 7 is provided in contact with the absorption film 6. The etching mask film 7 may be a single layer or a multilayer film.

[0064] Figure 2 is a cross-sectional view showing an example (second embodiment) of the reflective mask blank 100 of this embodiment. This reflective mask blank 100 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, a first interlayer film 4 formed in contact with the protective film 3, a second interlayer film 5, an absorption film 6 formed in contact with the second interlayer film 5, and an etching mask film 7 formed in contact with the absorption film 6.

[0065] When the absorption film 6 is made of a material that can be dry-etched using a fluorine-containing gas, the etching mask film 7 preferably contains chromium (Cr), and it is preferable that the etching mask film 7 is made of a chromium (Cr)-containing material. Since chromium (Cr)-containing materials are difficult to etch using a fluorine-containing gas, an etching mask film 7 made of a chromium (Cr)-containing material that functions as an etching mask when dry-etching the absorption film 6 is preferred. Examples of chromium (Cr)-containing materials include elemental Cr, CrO, CrN, CrON, CrC, CrOC, CrNC, and CrONC.

[0066] After forming the pattern of the absorption film 6, the etching mask film 7 may be left on the reflective mask 110 as a reflectance reduction layer to reduce the reflectance at wavelengths of light used in inspections such as pattern inspection, or it may be removed so that it does not remain on the reflective mask 110.

[0067] The thickness of the etching mask film 7 is not particularly limited, but if it is too thin, it may not function as a hard mask, and if it is too thick, the processing characteristics may deteriorate. Therefore, it is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 5 nm or more, and also preferably 20 nm or less, more preferably 10 nm or less.

[0068] The etching mask film 7 can be formed by sputtering. Specifically, when forming with a material containing chromium (Cr), a target can be 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.) according to the composition. Sputtering can be performed using noble gases such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe) as the sputtering gas. Alternatively, reactive sputtering can be performed using reactive gases such as oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases, specifically oxygen (O2), nitrogen (N2), nitrogen oxide (N2O, NO, NO2) gas, carbon oxide (CO, CO2) gas, hydrogen (H2) gas, and hydrocarbon gases (e.g., methane (CH4) gas) along with the noble gas. Magnetron sputtering is preferred for sputtering.

[0069] As shown in Figure 4, the reflective mask blank 100 of this embodiment may have a resist film 9 formed on the side furthest from the substrate 1. The resist film 9 is preferably an electron beam (EB) resist.

[0070] From the reflective mask blank 100, for example, a reflective mask 110 can be manufactured having a substrate 1, a multilayer reflective film 2 formed on one main surface of the substrate 1, a protective film 3 formed in contact with the multilayer reflective film 2, a pattern 41 of a first interlayer film 4 formed in contact with the protective film 3, a pattern 51 of a second interlayer film 5 formed in contact with the pattern 41 of the first interlayer film 4, and a pattern (absorption film pattern) 61 of an absorption film 6 formed in contact with the pattern 51 of the second interlayer film 5 (see Figure 3). In the reflective mask 110, a transfer pattern is formed by the difference in reflectivity between the areas where the absorption film 6 is formed and the areas where the absorption film 6 is not formed.

[0071] Figure 3 is a cross-sectional view showing an example of a reflective mask 110 according to this embodiment. This reflective mask 110 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, a pattern 41 of a first interlayer film 4 formed in contact with the protective film 3, a pattern 51 of a second interlayer film 5 formed in contact with the pattern 41 of the first interlayer film 4, and a pattern 61 of an absorption film 6 formed in contact with the pattern 51 of the second interlayer film 5. In this reflective mask 110, the pattern 61 of the absorption film 6 is formed above the protective film 3 via the pattern 41 of the first interlayer film 4 and the pattern 51 of the second interlayer film 5.

[0072] The reflective mask 110 of this embodiment can be manufactured by a method that includes the steps of: preparing a reflective mask blank 100; optionally, forming a resist film 9 on an absorption film 6; forming a resist pattern from the resist film 9 on the absorption film 6; using the resist pattern as an etching mask to etch the absorption film 6 and form a pattern on the absorption film 6; removing the resist pattern; and removing the first interlayer film 4 and the second interlayer film 5 from the exposed portion after the absorption film 6 has been removed.

[0073] The absorption film 6 and the second interlayer film 5, both formed from a chromium (Cr)-containing material, can be etched by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0074] In this case, the first interlayer 4 containing niobium (Nb) is not etched by dry etching using a gas containing chlorine (Cl) and oxygen (O), thus further preventing damage to the protective film 3.

[0075] The absorption film 6, formed from 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 the tantalum (Ta)-containing absorption film 6, when etching the oxygen (O)-containing portions formed by spontaneous oxidation, dry etching using a fluorine (F)-containing gas is preferable, and when etching the portions that do not contain oxygen (O), dry etching using a chlorine (Cl)-containing gas is preferable. Therefore, it is preferable to pattern the tantalum (Ta)-containing absorption film 6 by initially using dry etching with a fluorine (F)-containing gas, and then switching to dry etching with a chlorine (Cl)-containing gas midway through the process. In this case, since the first interlayer 4 has low resistance to dry etching with a chlorine (Cl)-containing gas, it is preferable to etch in a way that leaves the first interlayer 4 intact. To etch in a way that leaves the first interlayer 4 intact, for example, an endpoint detector attached to the etching apparatus can be used.

[0077] Furthermore, the reflective mask 110 of this embodiment can be manufactured by a method that includes the steps of: preparing a reflective mask blank 100; optionally, forming a resist film 9 on an etching mask film 7; forming a resist pattern from the resist film 9 on the etching mask film 7; using the resist pattern as an etching mask to etch the etching mask film 7 and form a pattern of the etching mask film 7; using the pattern of the etching mask film 7 as an etching mask to etch the absorption film 6 and form a pattern of the absorption film 6; removing the resist pattern; removing the pattern of the etching mask film 7; and removing the first interlayer film 4 and the second interlayer film 5 from the exposed portions after the absorption film 6 has been removed.

[0078] After forming the pattern of the absorption film 6, the pattern of the etching mask film 7 can be removed by dry etching using a gas containing chlorine (Cl) or fluorine (F) if the etching mask film 7 is made of a material containing tantalum (Ta), or by dry etching using a gas containing chlorine (Cl) and oxygen (O) if the etching mask film 7 is made of a material containing chromium (Cr).

[0079] If the absorption film 6 contains tantalum (Ta), the etching mask film 7 is made of a film containing chromium (Cr), and the etching mask film 7 is patterned by dry etching using a gas containing chlorine (Cl) and oxygen (O) to form a pattern on the etching mask film 7. After patterning the absorption film 6 using the pattern on the etching mask film 7 as an etching mask, the etching mask film 7 can be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O).

[0080] In this process, the first interlayer 4 containing niobium (Nb) is not etched by dry etching using a gas containing chlorine (Cl) and oxygen (O), thus preventing damage to the protective film 3.

[0081] The resist pattern, the absorption film 6, and the second interlayer 5 have been removed, and the first interlayer 4 in the exposed portion can be removed by sulfuric acid peroxide (SPM).

[0082] Furthermore, niobium oxide (NbO) is formed on the surface of the first interlayer 4 in the portion exposed after the removal of the absorption film 6 and the second interlayer 5. Since niobium oxide (NbO) is etched with a gas containing chlorine (Cl) or a gas containing fluorine (F), etching the first interlayer with such an etching method will result in an insufficient etching selectivity ratio with the protective film, damaging the protective film. Therefore, it is preferable to remove the first interlayer 4 with sulfuric acid peroxide (SPM). In this case, the first interlayer 4 can be removed simultaneously with the removal of the resist pattern.

[0083] The pattern of the absorption film 6 and the exposed protective film 3 can be subjected to treatments that involve contact with sulfuric acid peroxide (SPM), such as cleaning with sulfuric acid peroxide (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] [Example 1] A multilayer reflective film 2 was formed by sputtering 40 pairs (periods) of alternating molybdenum (Mo) and silicon (Si) layers, with each pair (period) consisting of a 3 nm thick molybdenum (Mo) layer and a 4 nm thick silicon (Si) layer. The uppermost layer of the multilayer reflective film 2 had a molybdenum layer thickness of 1 nm. Next, a 2 nm thick ruthenium (Ru) film was deposited on the multilayer reflective film 2 as a protective film 3. The reflectivity of this multilayer reflective film 2 and protective film 3 is 66% 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 3 as the first interlayer film 4. 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 10 nm thick RuON film was formed as the second interlayer 5. The RuON film was deposited by sputtering using a Ru target and introducing Ar, O2, and N2 gases.

[0088] Next, a 34 nm thick Pt film was deposited as the absorption film 6. The film was deposited using a sputtering apparatus that can simultaneously mount and discharge both a Pt target and a Ru target.

[0089] Next, a chromium nitride (CrN) film with a thickness of 10 nm (Cr:N = 4:1 atomic ratio) was formed on the absorption film 6 as an etching mask film 7. The chromium nitride (CrN) film was formed by sputtering while applying 1000 W of power to a chromium (Cr) target and flowing argon (Ar) gas at a flow rate of 20 sccm and nitrogen (N2) gas at 10 sccm.

[0090] Furthermore, a 70 nm thick tantalum nitride (TaN) film was formed as a conductive film 50 on the other main surface of the substrate 1 by sputtering to obtain a reflective mask blank 100.

[0091] A reflective mask 110 was manufactured from the obtained reflective mask blank 100. First, an electron beam (EB) resist was applied to the etching mask film 7 to form a resist film 9. A pattern was drawn on the resist film 9 using an electron beam (EB), and the film was developed to form a resist pattern having a line-and-space (L / S) pattern with a line width of 200 nm.

[0092] Next, using the resist pattern as an etching mask, a pattern for the etching mask film 7 was formed by dry etching using a gas containing chlorine (Cl2) gas and oxygen (O2) gas. Dry etching was performed using an inductively coupled plasma (ICP) method under the following conditions: Cl2 flow rate: 185 sccm, O2 flow rate: 55 sccm, He flow rate: 9.25 sccm, pressure: 6 mTorr (0.8 Pa), ICP power: 400 W, RIE voltage: 700 V, and over-etching: 454 seconds. Next, using the pattern of the etching mask film 7 as a mask, the absorption film 6 was etched using SF6 gas, and then the second interlayer film 5 was etched using Cl2 gas and O2 gas. At this time, the etching mask made of CrN was also peeled off simultaneously.

[0093] Next, the resist pattern was removed using sulfuric acid peroxide (SPM), and the first interlayer 4 in the exposed area after the absorption film 6 was removed was also removed to obtain a reflective mask 110.

[0094] When the cross-section of the etched portion of the absorption film 6 was observed with a transmission electron microscope (TEM), the first interlayer 4 had been removed, but the protective film 3 remained undamaged in the same form as when it was deposited. Furthermore, a good pattern consisting of the first interlayer 4, the second interlayer 5, and the absorption film 6 was obtained.

[0095] [Example 2] In the same manner as in Example 1, a multilayer reflective film 2, a protective film 3, and a first interlayer film 4 were formed. Then, a chromium nitride (CrN) film was deposited as a second interlayer film 5 with a thickness of 5 nm. In the same manner as in Example 1, an absorption film 6, an etching mask film 7, and a conductive film 50 were deposited on the other main surface of the substrate 1 to obtain a reflective mask blank 100.

[0096] Next, after forming a resist pattern in the same manner as in Example 1, the etching mask film 7, absorption film 6, second interlayer film 5, and first interlayer film 4 were patterned in the same manner as in Example 1 to form patterns for the first interlayer film 4, second interlayer film 5, and absorption film 6, thereby obtaining a reflective mask 110.

[0097] When the cross-section of the etched portion of the absorption film 6 was observed with a transmission electron microscope (TEM), the first interlayer 4 had been removed, but the protective film 3 remained undamaged in the same form as when it was deposited. Furthermore, a good pattern consisting of the first interlayer 4, the second interlayer 5, and the absorption film 6 was obtained.

[0098] [Comparative Example 1] A reflective mask blank 100 was obtained in the same manner as in Example 1, except that a first interlayer 4, which functions as an etching-blocking film, was not formed.

[0099] Next, following the same procedure as in Example 1, a resist pattern was formed, and then a pattern for the etching mask film 7 was formed.

[0100] Next, in the same manner as in Example 1, the absorption film 6 was patterned by dry etching using a gas containing SF6 gas, with the etching mask film 7 as a mask, to form a pattern for the absorption film 6.

[0101] When the cross-section of the etched portion of the absorption film 6 was observed with a transmission electron microscope (TEM), it was found that the protective film 3 had become thin and damaged, making it impossible to obtain a good reflective mask 110. [Explanation of Symbols]

[0102] 1 circuit board 2 Multilayer reflective film 3 Protective film 4. First interlayer 5. Second interlayer 6 Absorption membrane 7 Etching mask film 41 Pattern of the first interlayer 51 Pattern of the second interlayer 61 Absorption membrane patterns 100 Reflective Mask Blanks 110 Reflective Mask

Claims

1. A reflective mask blank that is used as the material for a reflective mask used in EUV lithography, which uses EUV light as the exposure light, circuit board and A multilayer reflective film that reflects exposure light is formed on one of the main surfaces of the substrate, A protective film formed above the multilayer reflective film to protect the multilayer reflective film, An absorption film that absorbs exposure light is formed above the protective film, An intermediate film provided between the protective film and the absorbing film, Equipped with, The interlayer comprises a first interlayer containing niobium (Nb) and a second interlayer provided on the absorption layer side of the first interlayer and made of a material that can be dry-etched with an oxygen-containing gas. The reflective mask blank is characterized in that the absorption film is formed of a material that can be dry-etched with a fluorine-containing gas.

2. The reflective mask blank according to claim 1, characterized in that the first interlayer film consists of niobium (Nb) alone, a niobium (Nb) compound containing niobium (Nb) and oxygen (O), or a laminated film of a combination thereof.

3. The reflective mask blank according to claim 1 or 2, characterized in that the second interlayer contains at least one selected from ruthenium (Ru), chromium (Cr), vanadium (V), and molybdenum (Mo).

4. The reflective mask blank according to claim 1 or 2, characterized in that the absorption film contains at least one selected from tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), and gold (Au).

5. The second interlayer contains ruthenium (Ru), The reflective mask blank according to claim 1 or 2, characterized in that the absorption film contains platinum (Pt).

6. The second interlayer contains chromium (Cr), The reflective mask blank according to claim 1 or 2, characterized in that the absorption film contains platinum (Pt).

7. The reflective mask blank according to claim 1 or 2, further comprising an etching mask film containing chromium (Cr) on the absorption film.

8. A method for manufacturing a reflective mask from a reflective mask blank according to claim 1 or 2, The absorption film is patterned by dry etching using a gas containing fluorine, The second interlayer is patterned by dry etching using an oxygen-containing gas, The first interlayer film is patterned with sulfuric acid peroxide (SPM), A method for manufacturing a reflective mask, characterized by comprising the following features.

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