Reflective mask blank, reflective mask, method for manufacturing a reflective mask

Abstract

To provide a reflective mask blank having an absorbent film with excellent etching properties and SPM resistance. [Solution] 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, and an absorber film, wherein the absorber film contains platinum and tungsten.

Description

[Technical Field]

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

[0002] In recent years, EUV lithography, which uses EUV light with a central wavelength of around 13.5 nm as a light source, has been investigated for further miniaturization of semiconductor devices.

[0003] In EUV lithography, reflective optics and reflective masks are used due to the characteristics of EUV light. In a reflective mask, a multilayer reflective film that reflects EUV light is formed on the 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 the exposure apparatus is reflected in areas without an absorber film (apertures) and absorbed in areas with an absorber film (non-apertures). As a result, the mask pattern is transferred as a resist pattern onto the wafer through the reduction projection optical system of the exposure apparatus, and subsequent processing is carried out. As a material to be used for absorber membranes, for example, Patent Document 1 discloses a material that contains at least one metallic element selected from rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), ruthenium (Ru), gold (Au), iridium (Ir), cobalt (Co), tin (Sn), nickel (Ni), rhenium (Re), molybdenum (Mo), and niobium (Nb), and the total content of the metallic element is 95 atomic percent or more. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 7475154 [Overview of the project] [Problems that the invention aims to solve]

[0006] The inventors of this invention investigated patterning using an absorbent film containing Pt as described in the above-mentioned literature and found that there is a need to improve the etching properties. Furthermore, when patterning a reflective mask blank and using it as a mask, sulfuric acid peroxide (SPM) is sometimes used as a processing solution during mask manufacturing, and the absorbent film is required to have excellent SPM resistance.

[0007] The present invention has been made in view of the above problems, and aims to provide a reflective mask blank having an absorbent film that exhibits excellent etching properties and excellent SPM resistance. Furthermore, the present invention also aims to provide a reflective mask and a method for manufacturing a reflective mask. [Means for solving the problem]

[0008] As a result of diligent research into the above-mentioned problems, the inventors of the present invention discovered that by using an absorber film containing platinum and tungsten, it is possible to achieve both etching resistance and SPM resistance, leading to the present invention.

[0009] In other words, the inventors found that the above problem could be solved by the following configuration. [1] A circuit board and A multilayer reflective film that reflects EUV light, A reflective mask blank having an absorbent membrane and in this order, The above absorbent membrane contains platinum and tungsten, and is a reflective mask blank. [2] The reflective mask blank according to [1], wherein the absorbent membrane further comprises at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon. [3] The absorbent membrane contains nitrogen, A reflective mask blank according to [1] or [2], wherein the nitrogen content in the absorbent membrane is 1 to 10 atomic percent relative to the total atoms of the absorbent membrane. 〔4〕 The content of platinum in the absorber film is 30 atomic% or more with respect to all atoms of the absorber film, and the reflective mask blank according to any one of 〔1〕 to 〔3〕. 〔5〕 The content of tungsten in the absorber film is 5 atomic% or more and 60 atomic% or less with respect to all atoms of the absorber film, and the reflective mask blank according to any one of 〔1〕 to 〔4〕. 〔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 manufacturing a reflective mask, including the step of patterning the absorber film of the reflective mask blank according to any one of 〔1〕 to 〔5〕.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a reflective mask blank having an absorber film excellent in etching properties and excellent in SPM resistance. Further, according to the present invention, it is also possible to provide a reflective mask and a method for manufacturing a reflective mask.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view showing an example of an embodiment of the reflective mask blank of the present invention. [Figure 2] It is a cross-sectional view showing an example of a manufacturing process of a reflective mask using the reflective mask blank of the present invention.

Modes for Carrying Out the Invention

[0012] The meanings of the terms in the present invention are as follows. A numerical range represented by using “~” means a range including the numerical values described before and after “~” as the lower limit value and the upper limit value. In this specification, elements such as boron, carbon, nitrogen, oxygen, silicon, titanium, chromium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum may be represented by their corresponding element symbols (such as B, C, N, O, Si, Ti, Cr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, etc.). Also, in this specification, silicon (Si) is included in the metal elements.

[0013] <Reflective mask blank> The reflective mask blank of the present invention is a reflective mask blank having a substrate, a multilayer reflective film that reflects EUV light (hereinafter, also simply referred to as "multilayer reflective film"), and an absorber film in this order, wherein the absorber film contains Pt and W.

[0014] The reflective mask blank of the present invention will be described while referring to the drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of the 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. Note that the reflective mask blank 10 shown in FIG. 1 may have a hard mask film, which will be described later, on the side opposite to the substrate 12 side of the absorber film 18. Also, the reflective mask blank 10 shown in FIG. 1 may have a conductive film, which will be described later, on the side opposite to the multilayer reflective film 14 side of the substrate 12. The reflective mask blank 10 shown in FIG. 1 has a protective film 16, but the protective film 16 may be omitted.

[0015] The absorber film in the reflective mask blank of the present invention is excellent in SPM resistance and etching properties. Although the details of the reason are unknown, the present inventor speculates as follows. Due to its resistance to oxidation, platinum (Pt) exhibits excellent SPM resistance but poor etching properties. By including both Pt, which has excellent SPM resistance, and W (which has excellent etching properties), the absorber film can achieve both SPM resistance and etching properties.

[0016] The configuration of the reflective mask blank of the present invention will be described in detail below.

[0017] [substrate] The substrate of the reflective mask blank of the present invention preferably has a small coefficient of thermal expansion. A smaller coefficient of thermal expansion of the substrate helps to suppress distortion of the absorber film pattern due to heat during exposure with EUV light. The thermal expansion coefficient of the substrate is 0 ± 1.0 × 10 at 20°C. -7 A temperature of / ℃ is preferred, and 0±0.3×10 -7 / ℃ is preferable. Materials with a low coefficient of thermal expansion include SiO2-TiO2 glass, but are not limited to this; crystallized glass with precipitated β-quartz solid solution, quartz glass, metallic silicon, and metal substrates can also be used. For SiO2-TiO2 glass, it is preferable to use quartz 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 coefficient of linear expansion at room temperature is approximately zero, and there is almost no dimensional change at room temperature. Note that SiO2-TiO2 glass may also contain trace components other than SiO2 and TiO2.

[0018] The side of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first main surface") preferably has high surface smoothness. The surface smoothness of the first main surface can be evaluated by its surface roughness. The surface roughness of the first main surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. Surface roughness can be measured with an atomic force microscope, and the surface roughness will be described as root mean square roughness Rq based on JIS-B0601. The first main surface is preferably surface-processed to achieve a predetermined flatness, which is advantageous for the pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. Specifically, the substrate has a flatness of 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less in a predetermined area of ​​the first main surface (for example, an area of ​​132 mm × 132 mm). The flatness can be measured using a flatness measuring instrument manufactured by Fujinon Corporation. The size and thickness of the substrate can be determined as appropriate by the mask design, etc. Examples of substrate dimensions include an outer diameter of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm). Circuit boards are often rectangular or square in shape. The substrate preferably has high rigidity in order to prevent deformation due to film stress in the films (multilayer reflective films and absorber films, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0019] [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 a high reflectivity of EUV light. Specifically, the maximum reflectivity of EUV light around a wavelength of 13.5 nm when EUV light is incident on the multilayer reflective film at an incident angle of 6° is preferably 60% or more, and more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0020] Because multilayer reflective films can achieve high reflectivity of EUV light, they typically use a multilayer reflective film in which a high refractive index layer, which exhibits a high refractive index for EUV light, and a low refractive index layer, which exhibits a low refractive index for EUV light, are alternately stacked multiple times. The multilayer reflective film may be constructed by stacking multiple layers in a layered structure in which a high refractive index layer and a low refractive index layer are stacked in that order from the substrate side, with each layer forming one period, or by stacking multiple layers in a layered structure in which a low refractive index layer and a high refractive index layer are stacked in that order from the substrate side, with each layer forming one period. A layer containing Si can be used as the high refractive index layer. The Si-containing material can be elemental Si, or a Si compound containing Si and at least one element selected from the group consisting of B, C, N, and O. By using a high refractive index layer containing Si, a reflective mask with high EUV light reflectivity can be obtained. As the low refractive index layer, a layer containing at least one metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof, can be used. Si is widely used in the high refractive index layer, and Mo is widely used in the low refractive index layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to these, and Ru / Si multilayer reflective films, Mo / Be multilayer reflective films, Mo compound / Si compound multilayer reflective films, Si / Mo / Ru multilayer reflective films, Si / Mo / Ru / Mo multilayer reflective films, Si / Ru / Mo multilayer reflective films, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0021] The film thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layer can be appropriately selected according to the materials used and the required EUV light reflectance of the multilayer reflective film. Taking a Mo / Si multilayer reflective film as an example, in order to obtain a multilayer reflective film with a maximum EUV light reflectance of 60% or more, a Mo film with a film thickness of 2.3 ± 0.1 nm and a Si film with a film thickness of 4.5 ± 0.1 nm should be stacked so that the number of repeating units is between 30 and 60. The reflectance of the multilayer reflective film for EUV light with an incident angle θ of 6° is preferably 60% or more, and more preferably 65% ​​or more.

[0022] Each layer constituting the multilayer reflective film can be deposited to a desired thickness using known deposition methods such as DC sputtering, magnetron sputtering, and 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 made of a high refractive index material and a target made of a low refractive index material. If the multilayer reflective film is a Mo / Si multilayer reflective film, for example, it can be fabricated by ion beam sputtering in the following way: First, a Si layer of a predetermined thickness is deposited on a substrate using a Si target. Then, a Mo layer of a predetermined thickness is deposited using a Mo target. These Si and Mo layers are stacked for, for example, 30 to 60 periods (preferably 40 to 50 periods) to form a Mo / Si multilayer reflective film.

[0023] [Protective film] The reflective mask blank of the present invention may have a protective film between the multilayer reflective film and the absorber film. The protective film is provided to protect the multilayer reflective film from damage during the etching process (usually a dry etching process) when a pattern is formed on the absorber film by etching. It is also preferable that the protective film protects the multilayer reflective film when the hard mask film, which will be described later, is removed.

[0024] The protective film preferably contains at least one element selected from the group consisting of Si, Ru, and Rh. It is also preferable that the protective film contains Rh. If the protective film contains Rh, the Rh content is preferably 50 atomic% or more relative to the total atoms of the protective film. Specific examples of protective film materials include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Rh, Pd, Ta, and Ir, elemental Rh metal, and Rh alloys containing Rh and one or more metals selected from the group consisting of Si, Y, Ti, Zr, Nb, Mo, Ru, Pd, Ta, and Ir. Adding Ru, Nb, Mo, Ze, Y, or Ti to Rh can suppress the increase in refractive index while reducing the extinction coefficient, making it easier to increase the reflectivity of EUV light. Additionally, adding Ra, Ir, Pd, or Y to Rh can improve resistance to etching processes. Materials that can be used for the protective film include elemental Al metal, nitrides containing Al and N, and Al2O3, etc. In particular, Ru elemental metal, Ru alloy, Rh elemental metal, or Rh alloy are preferred as materials for the protective film.

[0025] The protective film may contain at least one element selected from the group consisting of B, C, N, and O.

[0026] The types and content of elements contained in the protective film are obtained by X-ray photoelectron spectroscopy (XPS). When measuring the types and content of elements in the protective film using XPS, the layer on the opposite side of the protective film from the substrate side is removed by sputtering or other means before measurement. The same method as for the absorber membrane can be used for detailed XPS measurements.

[0027] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In terms of maintaining the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 10.0 nm or less, more preferably 6.0 nm or less, even more preferably 5.0 nm or less, and particularly preferably 3.5 nm or less. Furthermore, from the viewpoint of etching resistance, the thickness of the protective film is preferably 1.0 nm or more, more preferably 1.5 nm or more, and even more preferably 2.0 nm or more. In particular, it is preferable that the material of the protective film is elemental Ru metal, Ru alloy, elemental Rh metal, or Rh alloy, and that the thickness of the protective film satisfies the above preferred range. The thickness of the protective film is determined by X-ray reflectivity (XRR). Rigaku's Smart Lab HTP is used for XRR measurements. CuKα rays are used as the X-ray source, with a tube voltage of 40kV and a tube current of 30mA. The accompanying software (GlobalFit) is used for analysis.

[0028] The protective film may be a single-layer film or a multilayer film consisting of multiple layers. If the protective film is a multilayer film, it is preferable that each layer constituting the multilayer film is made of the material described above. Furthermore, if the protective film is a multilayer film, it is preferable that the total film thickness of the multilayer film satisfies the preferred range described above. If the protective film is a multilayer film, it is preferable that the layer located closest to the absorber film contains Rh. Furthermore, if the layer located closest to the absorber film contains Rh, it is preferable that at least one of the other layers contains Ru.

[0029] The protective film can be deposited using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. When depositing an Rh film by magnetron sputtering, it is preferable to use an Rh target as the target and Ar gas as the sputtering gas.

[0030] [Absorbing membrane] 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 reflected by the absorber film when a pattern is formed on the absorber film. The patterned absorber film (absorber film pattern) may function as a binary mask by absorbing EUV light, or it may function as a phase-shift mask that reflects EUV light and interferes with EUV light from a multilayer reflective film to produce contrast. In other words, the absorber film may also be a phase-shift film.

[0031] The absorbent membrane contains Pt and W. The Pt content is preferably 20 atomic% or more, more preferably 30 atomic% or more, even more preferably 40 atomic% or more, and particularly preferably 50 atomic% or more, relative to the total atoms of the absorber film, in terms of superior SPM resistance. Furthermore, the Pt content is preferably 95 atomic% or less, more preferably 90 atomic% or less, even more preferably 85 atomic% or less, particularly preferably 80 atomic% or less, and most preferably 70 atomic% or less, relative to the total atoms of the absorber film, in terms of superior etching properties. The W content is preferably 5 atomic% or more, more preferably 10 atomic% or more, even more preferably 15 atomic% or more, particularly preferably 25 atomic% or more, and most preferably 30 atomic% or more, relative to the total atoms of the absorber film, in terms of superior etching properties. Furthermore, the W content is preferably 80 atomic% or less, more preferably 70 atomic% or less, even more preferably 60 atomic% or less, and particularly preferably 50 atomic% or less, relative to the total atoms of the absorber film, in terms of superior SPM resistance. The total content of Pt and W is preferably 80 atomic% or more, and more preferably 90 atomic% or more, relative to the total atoms of the absorber membrane. The upper limit may be 100 atomic%. In other words, the absorber membrane may be a membrane made of Pt and W. The total content of Pt and W is preferably 99 atomic percent or less relative to the total atoms of the absorber film, from the viewpoint of crystallinity.

[0032] The absorber membrane may contain elements other than Pt and W. These other elements include metallic elements other than Pt and W, and nonmetallic elements. Other metallic elements include, for example, Ir, Ru, Pd, Ag, Ni, Co, Al, Cr, Mo, Nb, Si, Sn, Ta, Ti, Zr, and V. The content of other metal elements in the absorber membrane is preferably 10 atomic percent or less, more preferably 5 atomic percent or less, and even more preferably 3 atomic percent or less, relative to the total atoms of the absorber membrane. Furthermore, it is also preferable that the content of other metal elements in the absorber membrane is 0 atomic percent, relative to the total atoms of the absorber membrane. In other words, it is preferable that it does not contain any metal elements other than Pt and W. The nonmetallic element is preferably at least one element selected from the group consisting of N, O, B, and C, with N being more preferred. The presence of the above elements in the absorber film tends to reduce the crystallinity of the absorber film. If the absorbent membrane contains nonmetallic elements, the total content of the nonmetallic elements is preferably 1 to 20 atomic percent, more preferably 1 to 10 atomic percent, and even more preferably 1 to 5 atomic percent, relative to the total atoms of the absorbent membrane. Furthermore, it is preferable that the absorbent membrane contains N, and if the absorbent membrane contains N, the N content is preferably 1 to 20 atomic percent, more preferably 1 to 10 atomic percent, and even more preferably 1 to 5 atomic percent, relative to the total atoms of the absorbent membrane. Furthermore, if the reflective mask blank of the present invention has a hard mask film as described later, it is preferable that the absorber film does not contain metal elements contained in the hard mask film.

[0033] The types and content of elements contained in the absorber film can be measured by XPS. When measuring the types and content of elements in the absorber film using XPS, the layer on the opposite side of the absorber film from the substrate side should be removed by sputtering or other means before measurement. The detailed measurement method is described below.

[0034] For XPS analysis, we use the "PHI 5000 VersaProbe" analyzer manufactured by ULVAC-PHI, Inc. This analyzer is calibrated in accordance with JIS K 0145. First, a measurement sample approximately 1 cm square is cut out from the reflective mask blank. The obtained measurement sample is then placed in the measurement holder so that the absorber membrane side (or the hard mask membrane side if the reflective mask blank has a hard mask membrane) is the measurement surface. After loading the measuring holder into the apparatus, the hard mask film is removed from the outermost surface to a thickness equal to half the thickness of the absorber film. The sputtering rate during this removal can be measured using a separately prepared sample. After removing a portion of the absorber membrane, the removed area is irradiated with X-rays (monochromatic AlKα rays), and the analysis is performed with a photoelectron extraction angle (the angle between the surface of the sample and the direction of the detector) of 45°. In addition, a neutralization gun is used to suppress charge buildup during the analysis. The analysis involves first performing a wide scan in the bond energy range of 1000 to 0 eV to identify the elements present, and then performing a narrow scan depending on the elements present (e.g., Pt and W). The narrow scan is performed with, for example, a pass energy of 58.7 eV, an energy step of 0.1 eV, a time / step of 50 ms, and 5 integrations. 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 2 integrations. The content of each element in the absorber membrane is determined by analyzing the spectrum obtained by narrow scan during XPS analysis using the procedure described above, using relative sensitivity coefficients specific to each element and each orbital. Alternatively, the analysis may be performed using a model sample formed under the same conditions as those used to form the absorbent membrane, following the same procedure as described above.

[0035] When using an absorber film pattern as a binary mask, it is preferable that the absorber film absorbs EUV light and has a low reflectivity of EUV light. Specifically, when EUV light is irradiated onto the surface of the absorber film, it is preferable that the maximum reflectivity of EUV light around 13.5 nm is 2% or less. When using an absorber membrane pattern as a binary mask, the thickness of the absorber membrane is preferably 40-70 nm, and more preferably 50-65 nm. The thickness of the absorber membrane is determined by XRR.

[0036] When using an absorber film pattern as a phase shift mask, the reflectivity of the absorber film to EUV light is preferably 2% or higher, and more preferably 9-15% in order to obtain a sufficient phase shift effect. Using an absorber film pattern as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. When using an absorber film pattern as a phase shift mask, the thickness of the absorber film is preferably 30 to 75 nm, and more preferably 35 to 55 nm. The thickness of the absorber membrane is determined by XRR.

[0037] The refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.885 or higher, more preferably 0.893 or higher, even more preferably 0.895 or higher, and particularly preferably 0.904 or higher. Furthermore, when the absorber film is used as a phase-shift film, the refractive index n of the absorber film at a wavelength of 13.5 nm is preferably 0.930 or lower, more preferably 0.920 or lower, and even more preferably 0.910 or lower, as this allows for a thinner film thickness of the absorber film. The extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.035 or higher, more preferably 0.040 or higher, even more preferably 0.045 or higher, and particularly preferably 0.049 or higher, as this allows for easier adjustment of the reflectance of the absorber film. Furthermore, the extinction coefficient k of the absorber film at a wavelength of 13.5 nm is preferably 0.058 or lower, more preferably 0.056 or lower, and even more preferably 0.050 or lower, as this allows for easier adjustment of the reflectance of the absorber film. The refractive index n and extinction coefficient k mentioned above can be taken from the database of the Center for X-Ray Optics, Lawrence Berkeley National Laboratory, or from the "dependence of reflectance on the angle of incidence" described below. The incident angle θ of EUV light, the reflectance R for EUV light, the refractive index n of the film, and the extinction coefficient k of the film satisfy the following equation (1). R = |(sinθ - ((n+ik))) 2 -cos 2 θ) 1 / 2 ) / (sinθ+((n+ik) 2 -cos 2 θ) 1 / 2 )|···(1) By measuring multiple combinations of incident angle θ and reflectance R, and fitting the multiple measurement data to minimize the error between them and equation (1), the refractive index n and extinction coefficient k can be calculated.

[0038] The absorber film is preferably low in crystallinity, and more preferably amorphous. Low crystallinity of the absorber film allows for higher smoothness and flatness. High smoothness and flatness of the absorber film reduces the edge roughness of the absorber film pattern, thereby improving the dimensional accuracy of the absorber film pattern. The crystalline state of the absorber film can be confirmed by X-ray diffraction (XRD). More specifically, it can be confirmed from the X-ray diffraction chart of the absorber film measured using the out-of-plane method with CuKα rays. The Out-of-Plane method is a measurement method that uses a so-called θ / 2θ scan (also called the condensation method), and refers to a method of scanning the X-ray irradiation direction and the X-ray detection direction in a plane perpendicular to the main surface of a plate-shaped sample. Specifically, the X-ray irradiation direction and the X-ray detection direction are scanned in a plane perpendicular to the first main surface of the substrate. If peaks from other components of the reflective mask blank also appear, the diffraction chart and shape of the sample with the absorber film removed may be compared to identify the diffraction peaks originating from the absorber film. Detailed methods for obtaining X-ray diffraction charts using the out-of-plane method include the conditions described in the examples below.

[0039] The absorbent membrane may be a single layer or a multilayer membrane consisting of multiple layers. When the absorbent membrane is a single layer, the number of steps in mask blank manufacturing is reduced, resulting in superior production efficiency. If the absorber film is a multilayer film, the layer located on the side of the absorber film opposite the protective film side may be an anti-reflective film used when inspecting the absorber film pattern with inspection light (for example, wavelength 193-248 nm).

[0040] Absorber films can be formed using known film deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when forming a PtW film as an absorber film using magnetron sputtering, a Pt target and a W target are used, and sputtering is performed with Ar gas to deposit the absorber film. Alternatively, when forming a PtW film, targets containing Pt and W may be used.

[0041] [Hard mask film] The reflective mask blank of the present invention may have a hard mask film on the side opposite to the substrate side of the absorber film. When the reflective mask blank has a hard mask film, dry etching can be performed even if the minimum line width of the absorber film pattern is reduced. Therefore, it is effective for miniaturizing the absorber film pattern.

[0042] The hard mask film preferably contains one or more metallic elements selected from the group consisting of Al, Si, Ti, Cr, Y, Nb, Mo, Ta, Ru, and Hf (hereinafter also referred to as "element X"). The total content of element X in the hard mask film is preferably 30 atomic% or more, more preferably 50 atomic% or more, even more preferably 60 atomic% or more, and particularly preferably 70 atomic% or more, relative to the total atoms of the hard mask film. The upper limit may be 100 atomic%. In other words, the hard mask film may be a film made of element X alone. The total content of element X in the hard mask film may be 99 atomic percent or less, or 95 atomic percent or less.

[0043] The hard mask film may contain elements other than element X. The hard mask film may also preferably contain at least one element selected from the group consisting of B, N, C, and O.

[0044] Materials that constitute the hard mask film include element X, nitrogen oxides of element X, nitrides, oxynitrides, carbides, carbonitrides, carbonites, fluorides, and oxyfluorides. The material constituting the hard mask film may also be a composite compound (e.g., a composite oxide) containing two or more elements from element X.

[0045] Examples of Cr-based materials containing Cr include materials containing Cr, and materials containing Cr and at least one element selected from the group consisting of O, N, C, and H. More specifically, these include CrO, CrN, and CrON. The notation "CrON" represents a material containing Cr, O, and N, and similar notations below have the same meaning. Furthermore, 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. More specifically, these include SiO2, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON.

[0046] The thickness of the hard mask film is preferably 2 nm or more. The thickness of the hard mask film is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 10 nm or less. The thickness of the hard mask film is determined by XRR.

[0047] Hard mask films can be formed using known deposition methods such as DC sputtering, magnetron sputtering, and ion beam sputtering. For example, when forming a Ta film as a hard mask film, a Ta target can be used, and sputtering can be performed with Ar gas to form the hard mask film. Furthermore, when forming a hard mask film containing at least one element selected from the group consisting of N and O, it is sufficient to introduce at least one of N2 gas and O2 gas into the sputtering gas. By adjusting the amount of at least one of the above N2 gas and O2 gas introduced, the amount of at least one element selected from the group consisting of N and O contained in the formed film can be adjusted.

[0048] [Conductive film] The reflective mask blank of the present invention may have a conductive film on the side of the substrate opposite to the first main surface described above (hereinafter also referred to as the "second main surface"). The presence of a conductive film allows the reflective mask blank to be handled by an electrostatic chuck. The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably 200 Ω / sq. or less, and more preferably 100 Ω / sq. or less. The constituent materials of the conductive film can be broadly selected from those described in known literature. For example, a high dielectric constant coating described in Japanese Patent Publication No. 2003-501823, specifically a coating consisting of Si, Mo, Cr, CrON, or TaSi, can be applied. Alternatively, the constituent materials of the conductive film may be 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, and more preferably 10 to 400 nm. Furthermore, the conductive film may also have a function of adjusting the 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 the various films formed on the first main surface side. The conductive film can be formed using known film deposition methods, such as sputtering methods including DC sputtering, magnetron sputtering, and ion beam sputtering, as well as CVD, vacuum deposition, and electrolytic plating.

[0049] The reflective mask blank of the present invention can be manufactured, for example, by forming the multilayer reflective film on the substrate and forming an absorbent film on the multilayer reflective film. Furthermore, if the reflective mask blank of the present invention has a protective film, it can be manufactured, for example, by forming the multilayer reflective film on the substrate, forming a protective film on the multilayer reflective film, and forming the absorbent film on the protective film. If the reflective mask blank of the present invention has a hard mask film, the invention may include a step of forming the hard mask film on the absorber film. The formation method for each layer is as described above.

[0050] <Method for manufacturing a reflective mask and the reflective mask itself> The reflective mask of the present invention is obtained by patterning the absorbent film of the reflective mask blank of the present invention. An example of a method for manufacturing a reflective mask will be described with reference to Figure 2.

[0051] Figure 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 that order. A known method can be used to form the resist pattern 40. For example, a resist can be applied to the absorber film 18 of the reflective mask blank, and then exposed and developed to form the resist pattern 40. The resist pattern 40 corresponds to a pattern formed on a wafer using a reflective mask. Subsequently, the absorber film 18 is etched and patterned using the resist pattern 40 in Figure 2(a) as a mask, and the resist pattern 40 is removed to obtain a laminate having the absorber film pattern 18pt shown in Figure 2(b). Next, as shown in Figure 2(c), a resist pattern 41 corresponding to the frame of the exposure area is formed on the laminate in Figure 2(b), and dry etching is performed using the resist pattern 41 in Figure 2(c) as a mask. Dry etching is carried out until the substrate 12 is reached. After dry etching, the resist pattern 41 is removed to obtain the reflective mask shown in Figure 2(d).

[0052] Dry etching when forming the absorber film pattern 18pt is preferably performed using a gas containing a fluorine compound (F-type gas). As described above, the absorber film 18 contained in the reflective mask blank of the present invention exhibits excellent etching properties, and in particular, excellent etching properties with a gas containing a fluorine compound. Examples of fluorine compounds include gases such as CF4, CHF3, C2F6, C3F6, C4F6, C4F8, CH2F2, CH3F, C3F8, F2, SF6, and NF3, as well as mixtures thereof. The gas containing the fluorine compound may, if necessary, be mixed with active gases such as oxygen and chlorine, and inert gases such as nitrogen, helium, and argon. Among these, the inclusion of oxygen as the active gas is preferred. The etching gas may be converted into plasma and used to etch the absorber film 18.

[0053] The resist patterns 40 and 41 can be removed by known methods, including removal with a cleaning solution. Examples of cleaning solutions include sulfuric acid-hydrogen peroxide aqueous solution (SPM), sulfuric acid, ammonia water, ammonia-hydrogen peroxide aqueous solution (APM), OH radical cleaning water, and ozonated water, with SPM being the most frequently used. Since the absorbent film of the reflective mask blank of the present invention has excellent SPM resistance, it can be suitably used in the manufacture of reflective masks using SPM.

[0054] If the reflective mask blank has a hard mask film, the hard mask film may be patterned using the resist pattern 40 as a mask, and dry etching may be performed using the pattern of the hard mask film as a mask. The hard mask film patterning can be carried out by known methods, such as dry etching using an oxygen-containing gas or a chlorine-containing gas (Cl-based gas). If the reflective mask blank has a hard mask film, a step to remove the hard mask film may be performed. Alternatively, the hard mask film may be removed simultaneously in the step to remove the resist pattern 40 or 41 described above. The hard mask film can be removed, for example, by the same method as the etching of the hard mask film described above.

[0055] The reflective mask obtained by patterning the absorber film of the reflective mask blank of the present invention has the absorber film pattern described above. The reflective mask of the present invention can be suitably applied as a reflective mask used for exposure with EUV light.

Example

[0056] The present invention will be described in more detail based on the following examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below. Note that Examples 1 to 10 are examples, and Examples 11 to 13 are comparative examples.

[0057] <Example 1> First, the procedure for obtaining the reflective mask blank of Example 1 will be described.

[0058] [Substrate] First, as a substrate, a SiO2-TiO2-based glass substrate (outer shape 6 inches (152 mm) square, thickness 6.3 mm) was prepared. The thermal expansion coefficient of this glass substrate at 20 °C was 0.02 × 10 -7 / °C, the Young's modulus was 67 GPa, the Poisson's ratio was 0.17, and the specific stiffness was 3.07 × 10 7 m 2 / s 2 . The quality assurance area of the first main surface of the substrate had a root mean square roughness (Rq) of 0.15 nm or less and a flatness of 100 nm or less by polishing. A Cr film with a thickness of 100 nm was formed on the second main surface of the substrate using the magnetron sputtering method. The sheet resistance of the Cr film was 100 Ω / □.

[0059] [Multilayer reflective film] Next, a Mo / Si multilayer reflective film was formed on the first main surface of the substrate as a multilayer reflective film. The Mo / Si multilayer reflective film was obtained by repeatedly depositing a Si film (thickness 4.5 nm) and a Mo film (thickness 2.3 nm) 40 times using the ion beam sputtering method, and then depositing a Si film (thickness 4.5 nm) after the 40th Mo film was formed. The total thickness of the Mo / Si multilayer reflective film was 276.5 nm ((4.5 nm + 2.3 nm) × 40 + 4.5 nm).

[0060] [Protective film] On the multilayer reflective film formed using the above procedure, a Ru film (thickness 1.0 nm) and an Rh film (thickness 2.5 nm) were formed in that order as protective films. The Ru film and Rh film were formed by ion beam sputtering under the following conditions. Ru film deposition conditions: • Target: Ru target • Sputtering gas: Ar gas • Gas pressure: 0.027 Pa Ion acceleration voltage: 600V ·Deposition speed: 0.056nm / sec Rh film deposition conditions: • Target: Rh target • Sputtering gas: Ar gas • Gas pressure: 0.027 Pa Ion acceleration voltage: 600V ·Deposition speed: 0.077nm / sec

[0061] [Absorbing membrane] A PtW film (thickness 35 nm) was formed as an absorber film on the protective film formed by the above procedure. The PtW film was formed by DC sputtering under the following conditions. • Targets: Pt target, W target • Sputter gas: Ar gas ·Deposition speed: 0.17nm / sec • Power input density per target area: 2.0 W / cm² 2 (Pt target), 8.8 W / cm² 2 (Dual target)

[0062] <Examples 2-13> The reflective mask blanks in Examples 2-13 were obtained in the same manner as in Example 1, except that the composition of the absorber film was as shown in the table below. The absorber films of the reflective mask blanks in Examples 8-10 were deposited by introducing N2 gas into the sputtering gas.

[0063] <Evaluation Methods and Criteria> [Composition and film thickness of each layer] The chemical composition of the absorber film was measured using the XPS method described above with an ULVAC-PHI X-ray photoelectron spectrometer (PHI 5000 VersaProbe). The film thickness of each film was measured using the XRR method described above.

[0064] [Optical constants] The refractive index n and extinction coefficient k were calculated using the method described above.

[0065] [SPM resistance] A reflective mask blank was immersed in 100°C SPM (sulfuric acid hydrogen peroxide) for 20 minutes. The change in film thickness of the absorber film before and after immersion was measured using the XRR method, and the etching rate of the absorber film by SPM (unit: nm / min) was measured by dividing the result by the immersion time. The SPM resistance of the absorber film was evaluated from the obtained etching rate according to the evaluation criteria below. In practical terms, an evaluation of B or higher is preferable. SPM was obtained by mixing concentrated sulfuric acid and hydrogen peroxide solution in a ratio of 75% by volume:25% by volume (concentrated sulfuric acid:hydrogen peroxide solution). The concentrated sulfuric acid contained 96% by volume of sulfuric acid and 4% by volume of water. The hydrogen peroxide solution contained 30-35% by volume of hydrogen peroxide and 65-70% by volume of water. "A": Etching rate is less than 0.025 nm / min "B": Etching rate of 0.025 nm / min or higher, and less than 0.1 nm / min. "C": Etching rate of 0.1 nm / min or higher

[0066] [Etching properties] A sample for etching rate measurement was prepared by forming only the absorber film formed on a reflective mask blank onto a substrate, and the etching rate of the absorber film was measured. Specifically, plasma was generated on the above-mentioned etching rate measurement sample using an inductively coupled plasma (ICP) generator, and etching was performed by irradiating it with the plasma, and the etching rate of the absorber film was measured. The specific etching conditions are as follows. Antenna RF power output: 1200W • Bias RF power output: 50W Etching gas pressure: 0.4 Pa • Etching gas flow rate: CF4 / O2 mixed gas The film thickness before and after etching under the above conditions was measured using XRR, and the etching rate (unit: nm / min) was calculated by dividing the change in film thickness by the etching time. From the obtained etching rate, the etching performance of the absorber film was evaluated according to the evaluation criteria below. In practical terms, an evaluation of B or higher is preferable. "A": Etching rate of 20.0 nm / min or higher "B": Etching rate of 5.0 nm / min or more, and less than 20.0 nm / min. "C": Etching rate is less than 5.0 nm / min

[0067] [Crystalline] Crystallinity was confirmed by XRD using CuKα radiation. Specifically, for each example of the reflective mask blank absorber film, diffraction charts were obtained using the XRD method with an out-of-plane approach using CuKα radiation, according to the method described above. The above XRD measurements were performed using a Rigaku "Mini Flex" X-ray detector. The X-ray source was CuKα (including CuKα1 and CuKα2), with a tube voltage of 30kV and a tube current of 20mA. A one-dimensional detector was used for the measurements. Furthermore, a 1.0 mmφ microslit and a 1.0 mmφ collimator were used on the X-ray source side. The step width was 0.02°, the step time was 0.2 s / step, and measurements were performed in the range of 2θ from 20 to 80°. Crystallinity was evaluated based on the following criteria, using the full width at half maximum (FMAX) of the peak with the highest intensity in the range of 2θ from 20° to 50° obtained by the above method. "A": Half-width is 1.0° or greater "B": Half-width is less than 1.0°

[0068] <Result> The composition of the absorber membrane of each reflective mask blank and the evaluation results are shown in Table 1 below.

[0069] [Table 1]

[0070] The results shown in Table 1 confirm that when absorbent membranes containing Pt and W were used, both SPM resistance and etching properties were excellent (Examples 1 to 10). On the other hand, absorbent membranes without Pt had poor SPM resistance, absorbent membranes without W had poor etching properties, and absorbent membranes using Rh instead of Pt had poor etching properties (Examples 11 to 13). In the absorbent membrane, it was confirmed that SPM resistance was superior when the Pt content was 30 atomic percent or more relative to the total atoms of the absorbent membrane (Example 7). In the absorbent membrane, it was confirmed that SPM resistance is superior when the W content is 60 atomic percent or less relative to the total atoms of the absorbent membrane (Example 7). In absorber membranes, it was confirmed that etching properties were superior when the W content was 30 atomic percent or more relative to the total atoms of the absorber membrane (Examples 5, 6, 10). It was confirmed that the crystallinity of the absorber membrane was low when it contained nitrogen (Examples 8-10). [Explanation of Symbols]

[0071] 10 Reflective Mask Blanks 12 circuit boards 14 Multilayer reflective film 16 Protective film 18 Absorbent membrane 18pt Absorber membrane pattern 40,41 Resist Pattern

Claims

1. circuit board and A multilayer reflective film that reflects EUV light, A reflective mask blank having an absorbent membrane and in this order, A reflective mask blank in which the absorbent membrane contains platinum and tungsten.

2. The reflective mask blank according to claim 1, wherein the absorbent membrane further comprises at least one element selected from the group consisting of nitrogen, oxygen, boron, and carbon.

3. The absorbent membrane contains nitrogen, The reflective mask blank according to claim 1 or 2, wherein the nitrogen content in the absorbent membrane is 1 to 10 atomic percent relative to the total atoms of the absorbent membrane.

4. The reflective mask blank according to claim 1 or 2, wherein the platinum content in the absorbent membrane is 30 atomic percent or more relative to the total atoms of the absorbent membrane.

5. The reflective mask blank according to claim 1 or 2, wherein the tungsten content in the absorbent membrane is 5 atomic percent or more and 60 atomic percent or less with respect to the total atoms of the absorbent membrane.

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

7. A method for manufacturing a reflective mask, comprising the step of patterning the absorbent film of the reflective mask blank according to claim 1 or 2.

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