Reflective mask blank, reflective mask, manufacturing method of reflective mask, manufacturing method of reflective mask blank

Abstract

To provide a reflective mask blank capable of producing a reflective mask having an absorber film that is excellent in hydrogen resistance and absorption characteristics. [Solution] A reflective mask blank having, in this order, a substrate, a multilayer reflective film that reflects EUV light, a protective film, and an absorber film, wherein the absorber film contains one or more first elements selected from the group consisting of aluminum, chromium, niobium, ruthenium, tantalum, tungsten, silicon, platinum, iridium, gold, and palladium, and copper, and the copper content in the absorber film is 10 to 90 atomic % relative to the total atoms in the absorber film.

Description

[Technical Field]

[0001] The present invention relates to a reflective mask used in EUV (Extreme Ultra Violet) exposure, which is used in the exposure process of semiconductor manufacturing, a method for manufacturing the same, and a reflective mask blank, which is an original plate for the reflective mask. [Background technology]

[0002] In recent years, in order to further miniaturize semiconductor devices, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been considered.

[0003] Due to the characteristics of EUV light, EUV exposure uses a reflective optical system and a reflective mask. A reflective mask has a multilayer reflective film that reflects EUV light formed on a substrate, and an absorber film that absorbs EUV light is patterned on the multilayer reflective film.

[0004] EUV light incident on a reflective mask from the illumination optical system of an exposure tool is reflected by areas without an absorber film (openings) and absorbed by areas with an absorber film (non-openings). As a result, the mask pattern is transferred as a resist pattern onto a wafer through the reduced projection optical system of the exposure tool, and subsequent processing is carried out.

[0005] As a reflective mask blank that is an original plate for the above-mentioned reflective mask, for example, Patent Document 1 discloses a reflective mask blank. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 256062 Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors conducted a performance evaluation of a reflective mask fabricated using the reflective mask blank described in Patent Document 1 and found that the absorber film of the reflective mask had poor hydrogen resistance and / or absorption characteristics (e.g., refractive index n and extinction coefficient k). Here, the absorber film having poor absorption characteristics means that the refractive index n and extinction coefficient k of the absorber film are outside the desired ranges.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a reflective mask blank that can be used to fabricate a reflective mask having an absorber film that is excellent in hydrogen resistance and absorption characteristics. Another object of the present invention is to provide a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a reflective mask blank. [Means for solving the problem]

[0009] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration. [1] A substrate; A multilayer reflective film that reflects EUV light, A protective film; an absorber film, and the absorber film contains one or more first elements selected from the group consisting of aluminum, chromium, niobium, ruthenium, tantalum, tungsten, silicon, platinum, iridium, gold, and palladium, and copper; A reflective mask blank, wherein the copper content in the absorber film is 10 to 90 atomic % relative to all atoms in the absorber film. [2] The reflective mask blank according to [1], wherein the protective film contains one or more elements selected from the group consisting of rhodium, ruthenium, silicon, and niobium. [3] The reflective mask blank according to [1] or [2], wherein the absorber film has a thickness of 20 to 65 nm. [4] The reflective mask blank according to any one of [1] to [3], wherein the protective film contains one or more elements selected from the group consisting of rhodium and ruthenium. [5] The reflective mask blank according to any one of [1] to [4], wherein the absorber film contains one or more first elements selected from the group consisting of ruthenium and tantalum, and copper. [6] A reflective mask having an absorber film pattern formed by patterning the absorber film of the reflective mask blank according to any one of [1] to [5]. [7] A method for producing a reflective mask, comprising patterning the absorber film of the reflective mask blank according to any one of [1] to [5] to form an absorber film pattern. [8] The method for manufacturing a reflective mask according to [7], wherein the patterning of the absorber film is performed by supplying a first gas containing hydrogen gas or deuterium gas. [9] The method for manufacturing a reflective mask according to [8], wherein before supplying the first gas to the absorber film, a second gas containing a gas capable of generating one or more compounds selected from the group consisting of a halogen compound of the first element, an oxide of the first element, and a halogen-oxygen compound of the first element is supplied.

[10] A method for producing a reflective mask blank according to any one of [1] to [5], forming the multilayer reflective film on the substrate; forming the protective film on the multilayer reflective film; The method for producing a reflective mask blank includes forming the absorber film on the protective film. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a reflective mask blank that can be used to fabricate a reflective mask having an absorber film that is excellent in hydrogen resistance and absorption characteristics. The present invention also provides a reflective mask, a method for manufacturing a reflective mask, and a method for manufacturing a reflective mask blank. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. [Figure 2] 1A to 1C are cross-sectional views showing an example of a manufacturing process for a reflective mask using the reflective mask blank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.

[0013] The meaning of each description in this specification is as follows. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, elements such as boron, carbon, nitrogen, oxygen, aluminum, silicon, titanium, chromium, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum may be represented by their corresponding element symbols (B, C, N, O, Al, Si, Ti, Cr, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, etc.).

[0014] <Reflective mask blank> The reflective mask blank of the present invention is a reflective mask blank having, in this order, a substrate, a multilayer reflective film that reflects EUV light (hereinafter, also simply referred to as a "multilayer reflective film"), a protective film, and an absorber film, the absorber film contains one or more first elements selected from the group consisting of Al, Cr, Nb, Ru, Ta, W, Si, Pt, Ir, Au, and Pd, and Cu; The content of Cu in the absorber film is 10 to 90 atomic % with respect to all atoms in the absorber film.

[0015] The reflective mask blank of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing one embodiment of a reflective mask blank of the present invention. The reflective mask blank 10 shown in Fig. 1 has a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in this order. The protective film 16 contains the first element and a predetermined amount of Cu. The reflective mask blank 10 shown in Fig. 1 may have a conductive film, which will be described later, on the side of the substrate 12 opposite to the multilayer reflective film 14 side. Furthermore, the reflective mask blank 10 shown in FIG. 1 may have an etching mask film, which will be described later, on the side of the absorber film 18 opposite to the substrate 12 side.

[0016] The mechanism by which a reflective mask having an absorber film that is excellent in hydrogen resistance and absorption characteristics can be produced in the reflective mask blank of the present invention is not entirely clear, but the present inventors speculate as follows. In the reflective mask blank of the present invention, the Cu content in the absorber film is within a specific range. For example, if the Cu content in the absorber film of the reflective mask blank is less than 10 atomic %, the Cu content in the resulting reflective mask is relatively low, so the properties of Cu cannot be fully exhibited, and the absorption properties of the absorber film are often poor. On the other hand, if the Cu content in the absorber film of the reflective mask blank is more than 90 atomic %, the Cu content in the resulting reflective mask is relatively high, so the absorption properties of the absorber film are excellent, but the hydrogen resistance of the absorber film is often poor. In contrast, in the reflective mask blank of the present invention, it is believed that by adjusting the Cu content to be within a specific range, it is possible to achieve both the absorption properties and hydrogen resistance of the absorber film.

[0017] The structure of the reflective mask blank of the present invention will be described below.

[0018] [substrate] The substrate of the reflective mask blank of the present invention preferably has a small thermal expansion coefficient, which can prevent distortion of the absorber film pattern due to heat generated during exposure to EUV light. The thermal expansion coefficient of the substrate is 0±1.0×10 at 20℃. -7 / ℃ is preferred, 0±0.3×10 -7 / °C is more preferred. Materials with a low thermal expansion coefficient include SiO2-TiO2-based glass, but are not limited to this. Substrates such as crystallized glass in which β-quartz solid solution is precipitated, quartz glass, metallic silicon, and metal can also be used. The SiO2-TiO2-based glass preferably uses silica glass containing 90-95% by mass of SiO2 and 5-10% by mass of TiO2. When the TiO2 content is 5-10% by mass, the linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. Note that the SiO2-TiO2-based glass may contain trace components other than SiO2 and TiO2.

[0019] The surface of the substrate on which the multilayer reflective film is to be laminated (hereinafter also referred to as the "first principal surface") preferably has high surface smoothness. The surface smoothness of the first principal surface can be evaluated by surface roughness. The surface roughness of the first principal surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. The surface roughness can be measured using an atomic force microscope, and will be described as the root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to have a predetermined flatness, which improves the pattern transfer accuracy and positional accuracy of a reflective mask obtained using the reflective mask blank. In a predetermined region of the first main surface (e.g., a 132 mm × 132 mm region), the substrate preferably has a flatness of 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a Fujinon flatness measuring instrument. The size and thickness of the substrate are determined appropriately depending on the design values ​​of the mask, etc. For example, the outer shape is 6 inches (152 mm) square and the thickness is 0.25 inches (6.3 mm). The substrate is often rectangular or square. Furthermore, the substrate preferably has high rigidity to prevent deformation due to film stress of films (such as multilayer reflective films and absorber films) formed on the substrate. For example, the substrate preferably has a Young's modulus of 65 GPa or more.

[0020] [Multilayer reflective film] The multilayer reflective film of the reflective mask blank of the present invention is not particularly limited as long as it has the desired properties as a reflective film for an EUV mask blank. The multilayer reflective film preferably has high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity for EUV light at a wavelength of about 13.5 nm is preferably 60% or more, more preferably 65% ​​or more.

[0021] Multilayer reflective films can achieve high reflectivity for EUV light, so multilayer reflective films are usually used that are made by alternately stacking high-refractive index layers that have a high refractive index for EUV light and low-refractive index layers that have a low refractive index for EUV light multiple times. The multilayer reflective film may be formed by stacking multiple periods, each period being a stack structure in which a high refractive index layer and a low refractive index layer are stacked in this order from the substrate side, or may be formed by stacking multiple periods, each period being a stack structure in which a low refractive index layer and a high refractive index layer are stacked in this order. The high refractive index layer can be a layer containing Si. As the Si-containing material, in addition to simple Si, a Si compound containing Si and one or more elements selected from the group consisting of B, C, N, and O can be used. By using a high refractive index layer containing Si, a reflective mask with excellent reflectance to EUV light can be obtained. The low refractive index layer may be a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof. Si is commonly used for the high-refractive index layer, and Mo is commonly used for the low-refractive index layer. That is, Mo / Si reflective multilayer films are the most common. However, the reflective multilayer film is not limited to this, and Ru / Si reflective multilayer films, Mo / Be reflective multilayer films, Mo compound / Si compound reflective multilayer films, Si / Mo / Ru reflective multilayer films, Si / Mo / Ru / Mo reflective multilayer films, Si / Ru / Mo reflective multilayer films, and Si / Ru / Mo / Ru reflective multilayer films can also be used.

[0022] The thickness of each layer constituting the multilayer reflective film and the number of layer repeat units can be appropriately selected depending on the film material used and the EUV light reflectivity required for the reflective layer. Taking a Mo / Si multilayer reflective film as an example, a multilayer reflective film with a maximum EUV light reflectivity of 60% or more can be obtained by stacking a Mo film with a thickness of 2.3±0.1 nm and a Si film with a thickness of 4.5±0.1 nm so that the number of repeat units is 30 to 60. The multilayer reflective film preferably has a reflectivity of 60% or more for EUV light at an incident angle θ of 6°. The reflectivity is more preferably 65% ​​or more.

[0023] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using a known deposition method, such as DC sputtering, magnetron sputtering, or ion beam sputtering. For example, when fabricating a multilayer reflective film using ion beam sputtering, ion particles are supplied from an ion source to a target of a high refractive index material and a target of a low refractive index material. When the multilayer reflective film is a Mo / Si multilayer reflective film, for example, a Si layer with a predetermined thickness is first deposited on a substrate using an ion beam sputtering method, for example, using a Si target. Then, a Mo layer with a predetermined thickness is deposited using a Mo target. This Si layer and Mo layer constitute one cycle, and for example, 30 to 60 cycles (preferably 40 to 50 cycles) are stacked to form a Mo / Si multilayer reflective film.

[0024] [Protective film] The reflective mask blank of the present invention has a protective film between the reflective multilayer film and the absorber film. The protective film is provided for the purpose of protecting the reflective multilayer film from damage during an etching process (usually a dry etching process) to form a pattern on the absorber film. For example, it is preferable that the protective film is not etched by the first gas and the second gas described below. It is also preferable that the protective film plays a role in protecting the reflective multilayer film during removal of an etching mask film that may be included in the reflective mask blank of the present invention described below.

[0025] The protective film preferably contains one or more elements (hereinafter also referred to as "second elements") selected from the group consisting of Rh, Ru, Si, and Nb, and more preferably contains one or more elements selected from the group consisting of Rh and Ru. The protective film may also contain other elements, such as one or more elements selected from the group consisting of B, C, N, O, Ti, Zr, and Mo. The content of the second element (preferably one or more elements selected from the group consisting of Rh and Ru) in the protective film is preferably 50 atomic % or more, more preferably 70 atomic % or more, and even more preferably 90 atomic % or more, based on all atoms in the protective film. The upper limit may be 100 atomic % or less, 99 atomic % or less, or 97 atomic % or less.

[0026] The type and content of elements contained in the protective film can be obtained by the same method as the method for obtaining the type and content of elements contained in the absorber film, which will be described later.

[0027] More specifically, examples of materials for the protective film include simple Ru metal; Ru alloys containing Ru and at least one element selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Rh, Pd, Ta, and Ir; simple Rh metal; and Rh alloys containing Rh and at least one element selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Ru, Pd, Ta, and Ir. Adding Ru, Nb, Mo, Zr, Y, or Ti to Rh can reduce the extinction coefficient k while suppressing an increase in the refractive index, making it easier to improve the reflectivity to EUV light. Also, adding Ta, Ir, Pd, or Y to Rh makes it easier to improve resistance to etching processes. Furthermore, examples of materials that can achieve the above object include elemental Al metal, nitrides containing Al and N, and Al2O3. Among these, the materials that can achieve the above object are preferably Ru metal alone, Ru alloys, Rh metal alone, or Rh alloys.

[0028] The thickness of the protective film is not particularly limited as long as it can function as a protective film. In order to maintain the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 0.5 to 10.0 nm, more preferably 1.0 to 5.0 nm, even more preferably 1.0 to 3.0 nm, and particularly preferably 1.0 to 2.5 nm. The thickness of the protective film is measured, for example, by the method for measuring the thickness of the absorber film described below.

[0029] The protective film may be a film consisting of a single layer, or may be a multilayer film consisting of multiple layers. When the protective film is a multilayer film, it is preferable that at least one of the layers constituting the multilayer film is in the preferred embodiment described above. Furthermore, when the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the preferred range of the protective film thickness described above. When the protective film is a multilayer film, it is preferable that the layer of the multilayer film closest to the absorber film contains Rh. Furthermore, when the layer of the multilayer film closest to the absorber film contains Rh, it is also preferable that at least one of the other layers contains Ru.

[0030] The protective film can be formed by known film formation methods such as DC (Direct Current) sputtering, magnetron sputtering, ion beam sputtering, etc. When forming an Rh film by magnetron sputtering, it is preferable to use an Rh target as the target and Ar gas as the sputtering gas.

[0031] [Absorber film] The absorber film of the reflective mask blank of the present invention is required to have a high contrast between the EUV light reflected by the multilayer reflective film and the EUV light in the absorber film when the absorber film is patterned. The patterned absorber film (absorber film pattern) may function as a binary mask by absorbing EUV light, or may function as a phase shift mask by reflecting EUV light and interfering with the EUV light from the multilayer reflective film to create contrast. The absorber film pattern may be used as a binary mask (to be described later) or as a phase shift mask (to be described later), i.e., the absorber film may be a phase shift film.

[0032] The absorber film contains one or more elements (first elements) selected from the group consisting of Al, Cr, Nb, Ru, Ta, W, Si, Pt, Ir, Au, and Pd, and Cu. In other words, the absorber film contains the first element and Cu. The absorber film may also contain two or more elements as the first element.

[0033] The total Cu content in the absorber film is 10 to 90 atomic %, preferably 15 to 90 atomic %, more preferably 20 to 90 atomic %, even more preferably 30 to 85 atomic %, particularly preferably 35 to 70 atomic %, and most preferably 35 to 65 atomic %, relative to all atoms in the absorber film.

[0034] The first element preferably includes one or more elements selected from the group consisting of Al, Nb, Ru, Ta and W, and more preferably includes one or more elements selected from the group consisting of Ru and Ta. The content of the first element in the absorber film is, for example, 10 to 90 atomic % relative to all atoms in the absorber film, preferably 10 to 85 atomic %, more preferably 10 to 80 atomic %, even more preferably 20 to 75 atomic %, particularly preferably 30 to 70 atomic %, and most preferably 35 to 65 atomic %.

[0035] It is also preferable that the absorber film contains only the first element and Cu. The total content of the first element and Cu is preferably 90 atomic % or more, more preferably 99 atomic % or more, and even more preferably 99.9 atomic % or more, based on all atoms in the absorber film. The upper limit may be 100 atomic % or less.

[0036] The type and content of elements contained in the absorber film are obtained by X-ray photoelectron spectroscopy (XPS). When measuring the type and content of elements contained in the absorber film by XPS, the layer on the side of the absorber film opposite the substrate side is removed by sputtering or the like before the measurement is performed. The detailed measurement method will be explained below.

[0037] For the XPS analysis, an analytical instrument "PHI 5000 VersaProbe" manufactured by ULVAC-PHI, Inc. is used. The instrument is calibrated in accordance with JIS K 0145. First, a measurement sample of approximately 1 cm square is cut out from a reflective mask blank, and the obtained measurement sample is set in a measurement holder so that the absorber film side (or the etching mask film side if the reflective mask blank has an etching mask film) is the measurement surface. After the measurement holder is loaded into the apparatus, the absorber film is removed by half its thickness. The sputtering rate during the removal can be measured using a separately prepared sample. After removing a portion of the absorber film, the removed portion is irradiated with X-rays (monochromated AlKα rays) and analysis is performed with the photoelectron take-off angle (the angle between the surface of the measurement sample and the direction of the detector) set to 45°. During analysis, a neutralization gun is used to suppress charge build-up. The analysis involves a wide scan in the binding energy range of 1000 to 0 eV to confirm the elements present, followed by a narrow scan depending on the elements present (e.g., Cu and Ta). The narrow scan is performed with a pass energy of 58.7 eV, an energy step of 0.1 eV, a time step of 50 ms, and five accumulations. The wide scan is performed with a pass energy of 58.7 eV, an energy step of 1 eV, a time step of 50 ms, and two accumulations. The content of each element in the absorber film is analyzed using the relative sensitivity coefficient specific to each element and each orbital from the spectrum obtained by narrow scanning when XPS analysis is performed according to the above procedure. The analysis may be performed in the same manner as above using a model sample formed under the same conditions as those for forming the absorber film.

[0038] The thickness of the absorber film is preferably 30 to 75 nm, more preferably 20 to 65 nm.

[0039] When the absorber film pattern is used as a binary mask, it is preferable that the absorber film absorbs EUV light and has low reflectance for EUV light. Specifically, when EUV light is irradiated onto the surface of the absorber film, the maximum reflectance of EUV light at a wavelength of around 13.5 nm is preferably 2% or less. When the absorber film pattern is used as a binary mask, the film thickness of the absorber film is preferably 40 to 70 nm, more preferably 50 to 65 nm. The thickness of the absorber film is determined by XRR.

[0040] When the absorber film pattern is used as a phase shift mask, the reflectance of the absorber film to EUV light is preferably 2% or more. To obtain a sufficient phase shift effect, the reflectance of the absorber film is preferably 9 to 15%. Using the absorber film as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. The thickness of the absorber film (particularly when used as a phase shift mask) is preferably 30 to 75 nm, more preferably 35 to 55 nm. The thickness of the absorber film is determined by XRR.

[0041] The refractive index n of the absorber film is preferably 0.885 or more. The upper limit is preferably 0.980 or less, more preferably 0.970 or less, and even more preferably 0.965 or less, in order to enable the thickness of the absorber film to be made thinner. The extinction coefficient k of the absorber film is preferably 0.070 or less, more preferably 0.060 or less, and even more preferably 0.055 or less. In terms of making it easier to adjust the reflectance of the absorber film, the extinction coefficient k of the absorber film is preferably 0.018 or more, more preferably 0.020 or more, even more preferably 0.025 or more, and particularly preferably 0.035 or more. When n is 0.94 or less, the refractive index n and the extinction coefficient k are preferably 0.015 or more and 0.070 or less, more preferably 0.0175 or more and 0.070 or less, and even more preferably 0.020 or more and 0.070 or less. Furthermore, when n exceeds 0.94, k is preferably 0.035 or more and less than 0.060, more preferably 0.040 or more and less than 0.060, and even more preferably 0.043 or more and less than 0.060. By controlling n and k within the above ranges, it is possible to obtain an appropriate phase and reflectance that are effective for exposure characteristics. The refractive index n and extinction coefficient k can be values ​​from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or values ​​calculated from the "incident angle dependence" of reflectance described below. The incident angle θ of the EUV light, the reflectance R for the EUV light, the refractive index n of the film, and the extinction coefficient k of the film satisfy the following formula (1). R=|(sinθ-((n+ik) 2 -cos 2 θ) 1 / 2 ) / (sinθ+((n+ik) 2 -cos 2 θ) 1 / 2 )|···(1) The refractive index n and extinction coefficient k can be calculated by measuring multiple combinations of the incident angle θ and the reflectance R and fitting the multiple measurement data to minimize the error between the multiple measurement data and equation (1).

[0042] The crystalline state of the absorber film may be amorphous. When the crystalline state of the absorber film is amorphous, the smoothness and flatness of the absorber film can be further improved. Furthermore, when the smoothness and flatness of the absorber film are improved, the edge roughness of the absorber film pattern is reduced, and the dimensional accuracy of the absorber film pattern can be improved.

[0043] The absorber film may be a single-layer film or a multi-layer film made up of multiple films. When the absorber film is a single-layer film, the number of steps in manufacturing the mask blank can be reduced, improving production efficiency. When the absorber film is a multi-layer film, the layer disposed on the opposite side of the absorber film from the protective film side may be an anti-reflection film used when inspecting the absorber film pattern using inspection light (for example, wavelength 193 to 248 nm).

[0044] The absorber film can be formed using known film formation methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when forming a CuTa film as the absorber film using magnetron sputtering, a Cu target and a Ta target can be used, and Ar gas can be supplied to perform sputtering to form the absorber film. Furthermore, when forming a CuTa film, a target containing Cu and Ta may be used.

[0045] [Etching mask film] The reflective mask blank of the present invention may have an etching mask film on the side of the absorber film opposite to the substrate side. The etching mask film is preferably made of a material that is highly resistant to dry etching. When an etching mask film is formed on the absorber film, dry etching can be performed even if the minimum line width of the absorber film pattern is small. Therefore, this is effective for miniaturizing the absorber film pattern.

[0046] The etching mask film preferably contains at least one element selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, Ru, and Hf. The etching mask film may further contain at least one element selected from the group consisting of B, N, C and O. Examples of materials constituting the etching mask film include at least one element selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf, as well as oxides, nitrides, oxynitrides, carbides, carbonitrides, carbonates, fluorides, and oxyfluorides thereof. Note that the material constituting the etching mask film may also be a composite compound (e.g., composite oxide) containing at least two elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, and Hf.

[0047] Examples of Cr-based materials containing Cr include materials containing Cr and at least one element selected from the group consisting of O, N, C, and H, and more specifically, CrO, CrN, and CrON. The term "CrON" refers to a material containing Cr, O, and N, and similar terms below have the same meaning. Examples of Si-based materials containing Si include Si and materials containing Si and at least one selected from the group consisting of O, N, C, and H, and more specifically, include SiO2, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON.

[0048] The thickness of the etching mask film is preferably 2 nm or more, and is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less. The thickness of the etching mask film is measured, for example, by the above-mentioned method for measuring the thickness of the absorber film.

[0049] The etching mask film can be formed by using a known film formation method such as DC sputtering, magnetron sputtering, or ion beam sputtering.

[0050] [Conductive film] The reflective mask blank of the present invention may have a conductive film on the surface (second main surface) opposite to the first main surface of the substrate. By providing the conductive film, the reflective mask blank can be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance, for example, preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The conductive film may be made of a wide range of materials, including those described in known literature. For example, the high-dielectric-constant coating described in JP-A-2003-501823, specifically a coating made of Si, Mo, Cr, CrON, or TaSi, may be used. The conductive film may also be made of a Cr compound containing Cr and one or more elements selected from the group consisting of B, N, O, and C, or a Ta compound containing Ta and one or more elements selected from the group consisting of B, N, O, and C. The thickness of the conductive film is preferably 10 to 1000 nm, more preferably 10 to 400 nm. The conductive film may also have a function of adjusting stress on the second main surface side of the reflective mask blank. That is, the conductive film can adjust the reflective mask blank to be flat by balancing the stress from various films formed on the first main surface side. The conductive film can be formed by using a known film formation method, for example, a sputtering method such as DC sputtering, magnetron sputtering, or ion beam sputtering, a CVD method, a vacuum deposition method, or an electrolytic plating method.

[0051] The reflective mask blank of the present invention can be produced, for example, by forming the multilayer reflective film on the substrate, forming the protective film on the multilayer reflective film, and forming the absorber film on the protective film. The method for forming each of the components is as described above.

[0052] <Reflective mask manufacturing method and reflective mask> The reflective mask of the present invention is obtained by patterning the absorber film of the reflective mask blank of the present invention. One example of a method for producing a reflective mask will be described with reference to FIG.

[0053] 2(a) shows a state in which a resist pattern 40 has been formed on a reflective mask blank having a substrate 12, a multilayer reflective film 14, a protective film 16, and an absorber film 18 in this order. The resist pattern 40 can be formed by a known method, for example, by applying a resist onto the absorber film 18 of the reflective mask blank, and then exposing and developing the resist to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Thereafter, the absorber film 18 is etched and patterned using the resist pattern 40 of FIG. 2(a) as a mask, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 18pt shown in FIG. 2(b). Next, as shown in Fig. 2(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate of Fig. 2(b), and dry etching is performed using the resist pattern 41 of Fig. 2(c) as a mask. Dry etching is performed until it reaches the substrate 12. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Fig. 2(d).

[0054] The dry etching for forming the absorber film pattern 18pt is preferably performed by supplying at least a first gas containing hydrogen gas. In the reflective mask blank of the present invention, when the first gas is supplied, Cu contained in the absorber film 18 is removed.

[0055] The first gas is a gas containing hydrogen gas or deuterium gas. The first gas may contain gases other than hydrogen gas and deuterium gas, such as oxygen gas, nitrogen gas, and rare gases such as helium gas and argon gas.

[0056] The first gas may be supplied to the absorber film 18 in the form of plasma. When the first gas is turned into plasma and supplied to the absorber film 18, the pressure during the plasma treatment is, for example, 0.1 Pa to 1000 kPa. The pressure is preferably 1 Pa or more, more preferably 5 Pa or more, and even more preferably 10 Pa or more. The pressure is preferably 500 kPa or less, more preferably 200 kPa or less, and even more preferably 100 kPa or less. When the pressure is within the above range, the metal to be etched can be efficiently oxidized. Furthermore, even when the first gas is supplied to the absorber film 18 without being converted into plasma, it is preferable to supply the first gas at the above-mentioned preferred pressure.

[0057] Furthermore, before supplying the first gas to the absorber film 18, a second gas containing a gas capable of producing at least one compound selected from the group consisting of a halogen compound of the first element, an oxide of the first element, and a halogen-oxygen compound of the first element may be supplied. The halogen compound of the first element refers to a compound consisting of the first element and a halogen element. The halogen element refers to at least one element selected from the group consisting of F, Cl, Br, and I, and the halogen element preferably includes at least one element selected from the group consisting of F and Cl. Moreover, the oxide of the first element refers to a compound made of the first element and oxygen. Furthermore, the halogen-oxygen compound of the first element refers to a compound consisting of the first element, a halogen element, and oxygen. When the second gas is supplied to the absorber film 18, the compound of the first element, which is easily volatilized, is produced, and the first element contained in the absorber film 18 is removed from the system as the compound.

[0058] The second gas is not particularly limited as long as it is a gas that can generate the compound of the first element, but examples thereof include gases containing one or more selected from the group consisting of F-based gases, Cl-based gases, and oxygen-based gases. Examples of F-based gases include gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, F2, SF6, and NF3, as well as mixed gases thereof. Examples of Cl-based gases include gases such as Cl2, SiCl4, CHCl3, CCl4, and BCl3, as well as mixed gases of these. Examples of oxygen-based gases include gases such as O2, CO2, and CO, as well as mixed gases of these. The second gas may include an inert gas such as He gas, Ar gas, Kr gas, Xe gas, or nitrogen gas.

[0059] The second gas may be supplied to the absorber film 18 in the form of plasma. When the second gas is turned into plasma and supplied to the absorber film 18, the preferred range of pressure during the plasma treatment is as described above.

[0060] Furthermore, the supply of the second gas and the supply of the first gas to the absorber film 18 may be alternately and repeatedly carried out. As described above, when the second gas is supplied to the absorber film 18, the first element contained in the absorber film is removed as the compound of the first element, and further, Cu contained in the absorber film 18 is likely to remain in an activated state. More specifically, a layer of activated Cu is likely to be formed. When the first gas is supplied to the activated Cu, Cu can be efficiently removed. When the first gas is supplied after the second gas is supplied, a predetermined thickness of the absorber film 18 is removed, and therefore the above process may be repeated depending on the thickness of the removed film. The thickness of the absorber film 18 removed by supplying the second gas and the first gas is, for example, 0.5 to 10 nm. Furthermore, the second gas and the first gas may be simultaneously supplied to the absorber film 18. By simultaneously supplying the first gas and the second gas, Cu and the first element can be removed simultaneously, and throughput can also be improved.

[0061] The temperature of the reflective mask blank (substrate 12) when the second gas is supplied to the absorber film 18 is preferably 120°C or lower. The treatment temperature is preferably 100°C or lower, more preferably 80°C or lower. The treatment temperature is also preferably 20°C or higher, more preferably 40°C or higher, and even more preferably 60°C or higher.

[0062] It is preferable that the protective film 16 contains an element that is difficult to remove even when the first gas is supplied, so that damage to the multilayer reflective film 14 can be suppressed even when the first gas is supplied with the protective film 16 exposed. Furthermore, when the second gas described above is supplied to the absorber film 18, it is also preferable that the protective film 16 contains elements that are unlikely to produce halogen compounds, oxides, or halogen-oxygen compounds of the elements contained in the protective film 16.

[0063] The resist pattern 40 or 41 may be removed by a known method, such as removal with a cleaning solution, such as sulfuric acid-hydrogen peroxide solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide solution (APM), OH radical cleaning water, or ozone water. When the reflective mask blank has an etching mask film as another film, the etching mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the etching mask film as a mask. When the reflective mask blank has an etching mask film as another film, a step of removing the etching mask film may be performed in the step of obtaining the reflective mask. Furthermore, the etching mask film may be removed simultaneously in the step of removing the resist pattern 40 or 41 described above.

[0064] A reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention can be suitably used as a reflective mask for exposure to EUV light, since damage to the multilayer reflective film is suppressed. [Example]

[0065] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples. Examples 1 to 8 and 12 to 16 described below are working examples, and Examples 9 to 11 are comparative examples.

[0066] <Example 1> First, a CuTa thin film with a thickness of 50 nm was formed on a silicon wafer by DC magnetron sputtering under the following film formation conditions. Sputtering gas: Ar gas Pressure: 4.0×10 -1 Pa Target: Cu target and Ta target ·Input power density: 5.0W / cm 2 Target-wafer distance: 45 mm ·Deposition speed: 10nm / min

[0067] Next, the surface of the obtained CuTa thin film was subjected to a plasma treatment under the following conditions: the second gas was turned into plasma and supplied to the CuTa thin film. This treatment produces one or more compounds selected from the group consisting of a halide compound of the first element, an oxide of the first element, and a halogen-oxygen compound of the first element, and the compounds are volatilized and can be removed from the CuTa thin film. Processing gas (second gas): CF4 gas (O2 gas concentration 3% by volume) Processing pressure: 10Pa Wafer temperature: 20℃ Processing time: 3 minutes

[0068] Next, hydrogen gas was supplied to the obtained CuTa thin film. That is, the first gas was supplied to the CuTa thin film. By the above process, Cu was removed from the CuTa thin film. Processing gas: H2 gas Processing pressure: 1.0Pa Wafer temperature: 20℃ Processing time: 3 minutes

[0069] The supply process of the plasmatized second gas and the supply process of the first gas were repeatedly performed to simulate etching of a CuTa thin film (absorber film) (hereinafter simply referred to as "etching process"), thereby obtaining a reflective mask having an absorber film pattern. The etching rate per cycle was calculated to be 3 nm / cycle from the thickness of the CuTa thin film measured before the etching process and the thickness of the CuTa thin film measured after a predetermined number of etching processes. The thickness of the CuTa thin film was determined by XRR.

[0070] On the other hand, instead of the CuTa thin film, a Rh thin film was formed on the silicon wafer, and the Rh thin film (protective film) was subjected to etching treatment in the same manner as the CuTa thin film. In this study, no change in the thickness of the Rh thin film was observed. In other words, when a multilayer reflective film is provided on the substrate side of the Rh thin film, damage to the multilayer reflective film is suppressed. Furthermore, when a reflective mask blank having a substrate, a multilayer reflective film, an Rh protective film, and a CuTa absorber film in this order is subjected to a dry etching process using a first gas and a second gas during the etching process, the absorber film can be patterned while suppressing damage to the multilayer reflective film.

[0071] <Example 2 to Example 16> The reflective masks of Examples 2 to 16 were obtained in the same manner as in Example 1, except that the material used for the absorber film and the processing gas used in etching were changed as shown in Table 1 below.

[0072] <Evaluation method and criteria> [Composition and thickness of each layer] The chemical composition of the absorber films was measured by XPS using an ULVAC-PHI X-ray photoelectron spectrometer (PHI 5000 VersaProbe) as described above, and the thickness of each film was measured by XRR as described above.

[0073] [Hydrogen resistance evaluation] The hydrogen resistance of the absorber film of the reflective mask obtained in each example was evaluated by observing film peeling and film thickness reduction before and after exposing the absorber film to hydrogen gas. The hydrogen exposure was carried out by cutting each reflective mask into a 2.5cm square test piece, attaching it to a Si dummy substrate, setting it in a hydrogen irradiation test device that simulates an EUV exposure device, and irradiating it with hydrogen (including hydrogen ions). "A": No peeling of the absorber film or reduction in film thickness was observed "B": Peeling off of the absorber film and a decrease in film thickness were observed.

[0074] [Absorption characteristics] The absorption characteristics (refractive index n, extinction coefficient k, and reflectance) were measured by the following method. For each example of the reflective mask, the phase difference between the EUV light reflected from the multilayer reflective film and the EUV light reflected from the absorber film, and the relative reflectance between the EUV light reflectance of the absorber film surface and the EUV light reflectance of the multilayer reflective film surface when the absorber film thickness was 50 nm were determined by optical simulation. The optical constants of the multilayer reflective film required for the simulation were taken from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory.The optical constants of the absorber film were taken from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory or evaluated by measuring the "angle dependence" of the reflectance in the 13.5 nm region. Specifically, the EUV reflectance, the angle of incidence of EUV light, and the optical constants are expressed by the following equations: R=|(sinθ-((n+ik)2-cos2θ)1 / 2) / (sinθ+((n+ik)2-cos2θ)1 / 2)| where θ is the incident angle of EUV light, R is the EUV reflectance at the incident angle θ, n is the refractive index of the absorber film, and k is the extinction coefficient of the absorber film. The EUV optical constants (refractive index n, extinction coefficient k) were calculated by fitting the measured reflectance at each EUV incident angle using the above equation. When n is 0.94 or less, the refractive index n and the extinction coefficient k are preferably 0.015 or more and 0.070 or less, more preferably 0.0175 or more and 0.070 or less, and even more preferably 0.020 or more and 0.070 or less. Furthermore, when n is greater than 0.94, k is preferably 0.035 or more and less than 0.060, more preferably 0.040 or more and less than 0.060, and even more preferably 0.043 or more and less than 0.060. By controlling n and k within the above ranges, it is possible to obtain an appropriate phase and reflectance that are effective for exposure characteristics. The reflectance is preferably 6% or less, more preferably 4% or less.

[0075] <Result> In Table 1, "at %" means atomic %. "CF4" in the second gas column indicates that the above CF4 gas (O2 concentration 3% by volume) is used to etch the absorber film. "O2" in the second gas column indicates that O2 gas is used to etch the absorber film. "H2" in the first gas column indicates that H2 gas is used to etch the absorber film.

[0076] [Table 1]

[0077] In Examples 1 to 8, the Cu content in the absorber film was 10 to 90 atomic %, and it was confirmed that the absorption characteristics of the refractive index n and the extinction coefficient k were excellent. Furthermore, in Examples 1 to 8, no peeling of the absorber film or reduction in film thickness was observed, and the hydrogen resistance was also excellent. Furthermore, the reflectance was low. In Examples 9 and 10, the Cu content in the absorber film was over 90 atomic %, so the absorption characteristics of the refractive index n and extinction coefficient k were excellent. Furthermore, in Examples 9 and 10, peeling of the absorber film and a decrease in film thickness were presumably observed, so the hydrogen resistance was poor. Furthermore, the reflectance was also low. In Example 11, since the absorber film did not contain Cu, the absorption characteristics of the refractive index n and the extinction coefficient k were poor. Also, in Example 11, neither peeling of the absorber film nor a decrease in film thickness was observed. Furthermore, the reflectance was high. In addition, in Examples 12 to 16, the Cu content in the absorber film was 10 to 90 atomic %, and therefore it was confirmed that the absorption characteristics of the refractive index n and the extinction coefficient k were excellent. Furthermore, in Examples 12 to 16, no peeling of the absorber film or reduction in film thickness was observed, and the hydrogen resistance was also excellent. Furthermore, the reflectance was low. [Explanation of symbols]

[0078] 10 Reflective mask blanks 12 PCB 14 Multilayer reflective film 16 Protective film 18 Absorber membrane 18pt absorber film pattern 20 Etching mask film 40,41 Resist pattern

Claims

1. A substrate; a multilayer reflective film that reflects EUV light; A protective film; an absorber film, and the absorber film contains one or more first elements selected from the group consisting of aluminum, chromium, niobium, ruthenium, tantalum, tungsten, silicon, platinum, iridium, gold, and palladium, and copper; a reflective mask blank, wherein the copper content in the absorber film is 10 to 90 atomic % relative to all atoms in the absorber film.

2. 2. The reflective mask blank according to claim 1, wherein the protective film contains one or more elements selected from the group consisting of rhodium, ruthenium, silicon, and niobium.

3. 3. The reflective mask blank according to claim 1, wherein the absorber film has a thickness of 20 to 65 nm.

4. 3. The reflective mask blank according to claim 1, wherein the protective film contains one or more elements selected from the group consisting of rhodium and ruthenium.

5. 3. The reflective mask blank according to claim 1, wherein the absorber film contains one or more first elements selected from the group consisting of ruthenium and tantalum, and copper.

6. A reflective mask having an absorber film pattern formed by patterning the absorber film of the reflective mask blank according to claim 1 or 2.

7. A method for manufacturing a reflective mask, comprising patterning the absorber film of the reflective mask blank according to claim 1 or 2 to form an absorber film pattern.

8. 8. The method for manufacturing a reflective mask according to claim 7, wherein the patterning of the absorber film is performed by supplying a first gas containing hydrogen gas or deuterium gas.

9. 9. The method for manufacturing a reflective mask according to claim 8, wherein a second gas containing a gas capable of generating one or more compounds selected from the group consisting of a halide compound of the first element, an oxide of the first element, and a halogen-oxygen compound of the first element is supplied to the absorber film before the first gas is supplied.

10. 3. A method for producing a reflective mask blank according to claim 1 or 2, comprising: forming the multilayer reflective film on the substrate; forming the protective film on the multilayer reflective film; The method for manufacturing a reflective mask blank includes forming the absorber film on the protective film.

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