Reflective photomask blank, reflective photomask, and method for manufacturing reflective photomask

Abstract

The present invention provides a reflective photomask blank, a reflective photomask, and a method for manufacturing a reflective photomask, the reflective photomask blank being capable of improving transfer performance by: suppressing or reducing a projection effect of a reflective photomask for patterning transfer that uses light of a wavelength in an extreme-ultraviolet region as a light source; and suppressing drawing accuracy deterioration that may occur when electron beam drawing is performed on a resist film formed on an absorption layer, even while using a magnetic material. A reflective photomask blank (10) according to an embodiment of the present invention is for producing a reflective photomask (20) for pattern transfer that uses extreme-ultraviolet rays as a light source. The reflective photomask blank comprises a substrate (1), a reflection layer (2), and an absorption layer (4). The absorption layer (4) contains a total of 50 atomic % or more of nickel (Ni) and oxygen (O) with respect to the total number of atoms in the absorption layer (4), and the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is 0.5 or more.

Description

Reflective photomask blank, reflective photomask, and method for manufacturing reflective photomask

[0001] The present invention relates to a reflective photomask blank, a reflective photomask, and a method for manufacturing a reflective photomask, which are used in the manufacture of semiconductor devices and the like.

[0002] In the manufacturing process of semiconductor devices, the miniaturization of semiconductor devices has led to an increasing demand for miniaturization of photolithography technology. The minimum resolution dimension of a transfer pattern in photolithography is highly dependent on the wavelength of the exposure light source, and the shorter the wavelength, the smaller the minimum resolution dimension. For this reason, the exposure light source has been replaced from the conventional 193 nm wavelength ArF excimer laser light to light in the EUV (Extreme Ultra Violet) region with a wavelength of 13.5 nm.

[0003] Since light in the EUV region is absorbed at a high rate by most materials, a reflective photomask is used as a photomask for EUV exposure (EUV mask) (see, for example, Patent Document 1). Patent Document 1 discloses an EUV photomask obtained by forming a reflective layer made of a multilayer film in which molybdenum (Mo) layers and silicon (Si) layers are alternately stacked on a glass substrate, forming a light absorbing layer mainly composed of tantalum (Ta) thereon, and forming a pattern on this light absorbing layer.

[0004] Furthermore, as mentioned above, EUV lithography cannot use refractive optical systems that utilize the transmission of light, so the optical components of the exposure machine are reflective (mirrors) rather than lenses. This poses the problem that the incident light and reflected light on the reflective photomask (EUV mask) cannot be designed to be coaxial. Normally, EUV lithography employs a method in which the optical axis is tilted 6 degrees from the perpendicular direction of the EUV mask, and the reflected light reflected at an angle of minus 6 degrees is guided onto the semiconductor substrate.

[0005] In this way, in EUV lithography, the optical axis is tilted via a mirror, which can cause a problem known as the "projection effect," in which the EUV light incident on the EUV mask casts a shadow on the mask pattern (patterned light-absorbing layer) of the EUV mask.

[0006] Current EUV mask blanks use a tantalum (Ta)-based film with a thickness of 60 to 90 nm as the light absorption layer. When an EUV mask fabricated using this mask blank is used for pattern transfer exposure, there is a risk of a decrease in contrast at the shadowed edge of the mask pattern, depending on the relationship between the incident direction of the EUV light and the orientation of the mask pattern. This can lead to problems such as increased line edge roughness of the transferred pattern on the semiconductor substrate and an inability to form line widths to the targeted dimensions, resulting in a deterioration in transfer performance.

[0007] Therefore, studies have been conducted on a reflective photomask blank in which the light absorption layer is changed from tantalum (Ta) to a material having a high absorbency (extinction coefficient) for EUV light, or a material with high absorbency is added to tantalum (Ta). For example, Patent Document 1 describes a reflective photomask blank in which the light absorption layer is made of a material containing 50 atomic % (at %) or more of Ta as a main component and further containing at least one element selected from Te, Sb, Pt, I, Bi, Ir, Os, W, Re, Sn, In, Po, Fe, Au, Hg, Ga, and Al.

[0008] Furthermore, materials such as Ni and Co also have high extinction coefficients and are therefore candidates for the light absorption layer. However, Ni, Co, and Fe are magnetic materials, and there is a concern that electron beam lithography may reduce lithography accuracy when a resist film formed on the light absorption layer is lithographed.

[0009] Patent No. 4926523

[0010] The present invention aims to provide a reflective photomask blank that can suppress or reduce the projection effect of a reflective photomask for patterning transfer using light with a wavelength in the extreme ultraviolet region as a light source, and that can improve transfer performance by suppressing a decrease in drawing accuracy that can occur when electron beam drawing is performed on a resist film formed on a light absorbing layer despite the use of a magnetic material; a reflective photomask produced using the reflective photomask blank; and a method for manufacturing the reflective photomask.

[0011] In order to solve the above-mentioned problems, a reflective photomask blank according to one embodiment of the present invention is a reflective photomask blank for producing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, and comprises: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0012] The absorber layer in the reflective photomask blank according to one aspect of the present invention may contain tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in an amount within a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorber layer.

[0013] In the reflective photomask blank according to one aspect of the present invention, the absorber layer may contain tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorber layer.

[0014] In the reflective photomask blank according to one aspect of the present invention, the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) may be 1.0 or more.

[0015] In the reflective photomask blank according to one aspect of the present invention, the absorber layer may contain nickel (Ni) in an amount of 50 atomic % or more relative to the total number of atoms in the absorber layer.

[0016] The film density of the absorber layer in the reflective photomask blank according to one embodiment of the present invention is 4.0 g / cm ３ The thickness of the absorption layer may be in the range of 17 nm to 45 nm.

[0017] In the reflective photomask blank according to one aspect of the present invention, the absorbing layer may have a thickness in the range of 19 nm to 40 nm.

[0018] The reflective photomask blank according to one embodiment of the present invention may further include an etching mask layer on the absorption layer.

[0019] The reflective photomask blank according to one aspect of the present invention may further include an etching mask layer on the absorption layer, and the etching mask layer may have a film thickness of 30 nm or less.

[0020] In order to solve the above-mentioned problems, a reflective photomask according to one embodiment of the present invention is a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, and includes a substrate, a reflective layer including a multilayer film formed on the substrate, and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0021] The absorption layer in the reflective photomask according to one aspect of the present invention may contain tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in an amount within a range of 5 atomic % to 50 atomic % with respect to the total number of atoms in the absorption layer.

[0022] In the reflective photomask according to one aspect of the present invention, the absorption layer may contain tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % with respect to the total number of atoms in the absorption layer.

[0023] In the reflective photomask according to one aspect of the present invention, an atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) may be 1.0 or more.

[0024] In the reflective photomask according to one aspect of the present invention, the absorption layer may contain nickel (Ni) in an amount of 50 atomic % or more relative to the total number of atoms in the absorption layer.

[0025] In the reflective photomask according to one aspect of the present invention, the film density of the absorption layer is 4.0 g / cm ３The thickness of the absorption layer may be in the range of 17 nm to 45 nm.

[0026] In the reflective photomask according to one aspect of the present invention, the absorption layer may have a thickness in the range of 19 nm to 40 nm.

[0027] In order to solve the above-mentioned problems, a manufacturing method of a reflective photomask according to one aspect of the present invention is a manufacturing method of a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising the steps of forming a reflective layer including a multilayer film on a substrate, and forming an absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0028] In order to solve the above-mentioned problems, a manufacturing method of a reflective photomask according to one aspect of the present invention is a manufacturing method of a reflective photomask using the above-mentioned reflective photomask blank, comprising the steps of forming the reflective layer including a multilayer film on the substrate, and forming the absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0029] In order to solve the above-described problems, a method for manufacturing a reflective photomask according to one aspect of the present invention is a method for manufacturing a reflective photomask, comprising the steps of forming the reflective layer including a multilayer film on the substrate, and forming the absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0030] According to one aspect of the present invention, a reflective photomask capable of improving transfer performance to a semiconductor substrate in patterning using light with a wavelength in the extreme ultraviolet region as a light source can be provided. More specifically, a reflective photomask according to one aspect of the present invention can suppress or reduce the projection effect of a reflective photomask for patterning transfer using light with a wavelength in the extreme ultraviolet region as a light source, and can suppress a decrease in writing accuracy. Thus, one aspect of the present invention can provide a reflective photomask that can improve transfer performance by suppressing or reducing the projection effect of the reflective photomask and suppressing a decrease in writing accuracy that can occur when electron beam writing is performed on a resist film formed on an absorption layer while using a magnetic material, a reflective photomask blank for producing the reflective photomask, and a method for producing a reflective photomask.

[0031] FIG. 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the structure of a reflective photomask according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to a modified example of an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing the structure of a reflective photomask according to a modified example of an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an example of the present invention. FIG. 6 is a schematic cross-sectional view showing a manufacturing process of a reflective photomask according to an example of the present invention. FIG. 7 is a schematic cross-sectional view showing a manufacturing process of a reflective photomask according to an example of the present invention. FIG. 8 is a schematic cross-sectional view showing the structure of a reflective photomask according to an example of the present invention. FIG. 9 is a schematic plan view showing the shape of a design pattern of a reflective photomask according to an example of the present invention.

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown below. In the embodiments shown below, technically preferable limitations are imposed for carrying out the present invention, but these limitations are not essential requirements for the present invention.

[0033] Fig. 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank 10 according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing the structure of a reflective photomask 20 according to an embodiment of the present invention. Here, the reflective photomask 20 according to the embodiment of the present invention shown in Fig. 2 is formed by patterning the absorption layer 4 of the reflective photomask blank 10 according to the embodiment of the present invention shown in Fig. 1.

[0034] (Configuration of Reflective Photomask Blank and Reflective Photomask) Fig. 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank 10 according to an embodiment of the present invention. As shown in Fig. 1, the reflective photomask blank 10 according to an embodiment of the present invention comprises a substrate 1, a reflective layer 2 formed on the substrate 1 and having a multilayer film structure that reflects EUV light, a protective layer (capping layer) 3 formed on the reflective layer 2, and an absorption layer 4 formed on the protective layer 3 that absorbs EUV light.

[0035] The reflective photomask 20 according to an embodiment of the present invention is produced by forming a transfer pattern in the absorption layer 4 of the reflective photomask blank 10 according to an embodiment of the present invention. Each layer constituting the reflective photomask blank 10 and the reflective photomask 20 according to an embodiment of the present invention will be described in detail below.

[0036] (Substrate) For example, a flat Si substrate, a synthetic quartz substrate, etc. may be used for the substrate 1 according to the embodiment of the present invention. Furthermore, low thermal expansion glass containing titanium may be used for the substrate 1, but the embodiment of the present invention is not limited to these as long as the material has a small thermal expansion coefficient.

[0037] Although not shown, a back surface conductive film can be formed on the surface of the substrate 1 on which the reflective layer 2 is not formed. The back surface conductive film is a film for fixing the reflective photomask 20 produced using the reflective photomask blank 10 according to an embodiment of the present invention in place using the principle of an electrostatic chuck when the reflective photomask 20 is placed in an exposure machine.

[0038] (Reflective Layer) The reflective layer 2 according to the embodiment of the present invention may be any layer that reflects EUV light (extreme ultraviolet light), which is exposure light, and may be a multilayer reflective film made of a combination of materials that have significantly different refractive indices for EUV light (i.e., an EUV light reflective film having a multilayer film structure). The reflective layer 2 including a multilayer reflective film may be formed by repeatedly stacking layers of a combination of, for example, Mo (molybdenum) and Si (silicon), or Mo (molybdenum) and Be (beryllium), for example, for about 40 periods.

[0039] (Protective Layer) The protective layer (capping layer) 3 according to the embodiment of the present invention is a layer that functions as an etching stopper that prevents damage to the reflective layer 2 when the absorbing layer 4 is etched during photomask fabrication. Note that the protective layer 3 may not be formed depending on the material of the reflective layer 2 and the etching conditions. The protective layer 3 is formed of a material that is resistant to dry etching that is performed during pattern formation of the absorbing layer 4. For example, the material of the protective layer 3 may be ruthenium (Ru).

[0040] (Absorbing Layer) As shown in Figure 2, an absorbing pattern (absorbing pattern layer) 41 is formed by patterning the absorbing layer 4 of the reflective photomask blank 10. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 2, but the absorbing pattern 41 obstructs the light path, resulting in a projection effect, which can deteriorate the transfer performance onto the wafer (semiconductor substrate). This deterioration in transfer performance can be reduced by reducing the thickness of the absorbing layer 4 that absorbs EUV light. In order to reduce the thickness of the absorbing layer 4, it is preferable to use a material that has a higher absorbency for EUV light than conventional materials, that is, a material with a high extinction coefficient k at a wavelength of 13.5 nm.

[0041] The extinction coefficient k of tantalum (Ta), which is the main material of the conventional absorber layer 4, is 0.041. If a compound material with a higher extinction coefficient k is used, it will be possible to make the thickness of the absorber layer 4 thinner than conventional materials. Materials with a higher extinction coefficient k than tantalum (Ta) include, for example, silver (Ag), platinum (Pt), indium (In), cobalt (Co), tin (Sn), nickel (Ni), and tellurium (Te). However, some of these metal materials have the problem of low cleaning resistance and hydrogen radical resistance, which are required in environments where reflective photomasks are used.

[0042] For this reason, even if a reflective photomask blank provided with an absorption layer formed of these metal materials is produced, it may not be possible to place it in an exposure environment. Furthermore, even if the material does not have any problems in terms of durability as described above, metal materials such as nickel (Ni) and cobalt (Co) are magnetic materials, and therefore there is a concern that the magnetism of the magnetic material may cause a decrease in drawing accuracy when drawing on a resist film using an electron beam drawing apparatus.

[0043] To avoid the above-mentioned drawbacks, the absorption layer 4 of the reflective photomask blank 10 according to an embodiment of the present invention, or the absorption pattern layer 41 of the reflective photomask 20 according to an embodiment of the present invention, is formed from a material containing nickel (Ni) and oxygen (O). While Ni alone has a high extinction coefficient k of a reflective photomask and is highly resistant to hydrogen radicals, it is known to be a magnetic material. Therefore, by mixing (adding) oxygen (O) into Ni alone, the absorption layer 4 is made non-magnetic, thereby enabling improved accuracy in electron beam lithography of the resist film formed on the absorption layer 4.

[0044] The material constituting the absorber layer 4 according to the embodiment of the present invention must contain nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms constituting the absorber layer 4. This is because, although there is a possibility that the EUV light absorption properties will decrease if the absorber layer 4 contains components other than nickel (Ni) and oxygen (O), if the components other than nickel (Ni) and oxygen (O) are less than 50 atomic % relative to the total number of atoms constituting the absorber layer 4, the decrease in EUV light absorption properties of the absorber layer 4 is very slight, and there is almost no decrease in performance as the absorber pattern layer 41 of the reflective photomask 20.

[0045] Furthermore, as described above, nickel (Ni) alone is magnetic, which reduces the accuracy of electron beam lithography on the resist film formed on the absorber layer 4. However, by mixing (adding) oxygen (O) to nickel (Ni), the magnetism is alleviated compared to nickel (Ni) alone, thereby improving the accuracy of electron beam lithography on the resist film formed on the absorber layer 4. Specifically, the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) in the material constituting the absorber layer 4 may be 0.5 or more, and preferably 1.0 or more. When the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is equal to or greater than the above-mentioned value, the accuracy of electron beam lithography on the resist film formed on the absorber layer 4 can be improved. In particular, when the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is 1.0 or more, that is, when the oxygen (O) content is increased, the etching rate when etching the absorber layer 4 with a fluorine-based gas can be increased.

[0046] If the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is less than 0.5, the absorber layer 4 is not demagnetized, and therefore electron beam lithography may not be possible on the resist film formed on the absorber layer 4, or the degree of demagnetization may be so small that the accuracy of electron beam lithography on the resist film formed on the absorber layer 4 may be insufficient.

[0047] Although there is no particular upper limit to the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni), a ratio of 3.0 or less is preferable in the case of oxygen reactive deposition, because it is easy to prepare samples containing excess oxygen.

[0048] As described above, the material constituting the absorber layer 4 according to the embodiment of the present invention may contain 50 atomic % or more of nickel (Ni) and oxygen (O) in total relative to the total number of atoms constituting the absorber layer 4, as long as it satisfies the conditions that the atomic ratio of oxygen (O) to nickel (Ni) (O / Ni) is 0.5 or more. If the material contains 50 atomic % or more of nickel (Ni), the extinction coefficient k of the entire absorber layer 4 becomes even higher, and transfer performance can be further improved.

[0049] Furthermore, the material constituting the absorption layer 4 according to the embodiment of the present invention may contain nickel (Ni) and oxygen (O) in a total amount of 100 atomic % with respect to the total number of atoms constituting the absorption layer 4, as long as the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is 0.5 or more.

[0050] In the embodiment of the present invention, the composition ratio of the materials constituting the absorption layer 4 is calculated based on the analysis results obtained by Rutherford backscattering spectroscopy (RBS), and the contents may vary depending on the analysis method. For example, a material whose nickel (Ni) content is 50 atomic % to 100 atomic % of all elements as determined by Rutherford backscattering spectroscopy (RBS) may be analyzed using X-ray photoelectron spectroscopy (XPS) to find that the Ni content is 40 atomic % to 75 atomic % of all elements, or may be analyzed using energy dispersive X-ray spectroscopy (EDX) to find that the Ni content is 45 atomic % to 100 atomic % of all elements.

[0051] In the embodiment of the present invention, the magnetism of the absorption layer 4 is determined based on the analysis results using a vibrating sample magnetometer (VSM). More specifically, in the embodiment of the present invention, the magnetism of the absorption layer 4 is determined based on the analysis results using a vibrating sample magnetometer (VSM). －５A material with a valence of less than (emu) is considered to be a non-magnetic material. By adding oxygen (O), which has no magnetism, to nickel (Ni), which is a magnetic material, the above-mentioned absorption layer 4 can be made non-magnetic.

[0052] In the magnetic evaluation test shown in Table 1 below, the detection limit was 10 －５ If the result was less than 10 (emu), it was evaluated as "Good (pass)." －５ (emu) or more was evaluated as "× (fail)." In the embodiment of the present invention, if the evaluation is "◯," it is determined that there is no problem in the drawing process using the electron beam drawing apparatus.

[0053] The measurement conditions for the vibrating sample magnetometer (VSM) in the embodiment of the present invention are as follows: Magnetic field application direction: parallel to the surface Magnetic field range: 10 kOe

[0054] The absorption layer 4 in the embodiment of the present invention is formed from a material that contains nickel (Ni) and oxygen (O) in total at 50 atomic % or more with respect to the total number of atoms constituting the absorption layer 4, and has an atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) of 0.5 or more, and the film density of the absorption layer 4 is 4.0 g / cm ３ It is preferable that the film density of the absorbing layer 4 is 4.0 g / cm or more. ３ If the film density is less than 4.0 g / cm, the k value (value of the extinction coefficient k) will be significantly reduced. Furthermore, there may be a problem that sufficient absorption performance for EUV light cannot be obtained. On the other hand, although there is no particular upper limit set for the film density of the absorber layer 4, the higher the film density, the more difficult it becomes to obtain smoothness of the film, and the more difficult it tends to be to form the film by a sputtering method or to process it by dry etching. Therefore, the film density of the absorber layer 4 should be 4.0 g / cm or less. ３ It is preferable that the density is 5.0 g / cm or more. ３ ~12.0 g / cm ３ More preferably, it is within the range of 6.0 g / cm ３ ~10.0 g / cm ３ It is more preferable that the range is within the range of

[0055] The film density of the absorption layer 4 in the embodiment of the present invention was calculated from the measurement results of Rutherford backscattering spectroscopy (RBS).

[0056] As described above, the film density of the absorber layer 4 affects the film smoothness and the line edge roughness of the formed absorber pattern layer 41. If the surface roughness of the absorber layer 4 is large, it may affect the reflection efficiency of EUV light. Therefore, the surface roughness (RMS) of the absorber layer 4 is preferably 0.6 nm or less, and more preferably 0.4 nm or less. In an embodiment of the present invention, the surface roughness (RMS) of the absorber layer 4 is measured using, for example, an atomic force microscope (AFM).

[0057] As described above, the material constituting the absorption layer 4 may be any material that contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more with respect to the total number of atoms in the absorption layer 4 and has an atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) of 0.5 or more, and may contain, as an element other than nickel (Ni) and oxygen (O), for example, tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si). In other words, the absorption layer 4 may further contain, as an element other than nickel (Ni) and oxygen (O), one or more elements selected from the group consisting of tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), and silicon (Si).

[0058] It is more preferable that the absorption layer 4 contains, in addition to nickel (Ni) and oxygen (O), one or more elements selected from the group consisting of tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), and silicon (Si) in an amount ranging from 5 atomic % to 50 atomic % with respect to the total number of atoms constituting the absorption layer 4. It is even more preferable that the absorption layer 4 contains, in addition to nickel (Ni) and oxygen (O), tantalum (Ta) or iridium (Ir) in an amount ranging from 5 atomic % to 50 atomic % with respect to the total number of atoms constituting the absorption layer 4.

[0059] If the content of elements other than nickel (Ni) and oxygen (O), i.e., the above-mentioned tantalum (Ta) or the like, exceeds 50 atomic %, the absorbency of EUV light decreases, making it impossible to achieve a thin film for the absorption layer 4. Furthermore, if the content of the above-mentioned tantalum (Ta) or the like exceeds 50 atomic %, the contrast in DUV (Deep Ultra Violet) light with a wavelength of 190 to 260 nm decreases, resulting in poor inspectability.

[0060] Furthermore, if the content of the above-mentioned tantalum (Ta) or the like is less than 5 atomic %, the resulting film will have high crystallinity and poor processability. Therefore, the content of the above-mentioned tantalum (Ta) or the like is preferably 5 atomic % or more and 50 atomic % or less, more preferably 10 atomic % or more and 45 atomic % or less, and even more preferably 20 atomic % or more and 40 atomic % or less.

[0061] The above-mentioned composition ratios of the materials constituting the absorber layer 4 are calculated based on the analysis results obtained by Rutherford backscattering spectroscopy (RBS), and the contents may vary depending on the analysis method. For example, a material containing tantalum (Ta) or the like added to the absorber layer 4 whose content is 5 atomic % to 50 atomic % in RBS analysis may be analyzed using X-ray photoelectron spectroscopy (XPS) to find that the content is 4 atomic % to 45 atomic %. Furthermore, a material containing tantalum (Ta) or the like added to the absorber layer 4 whose content is 5 atomic % to 50 atomic % in RBS analysis may be analyzed using energy dispersive X-ray spectroscopy (EDX) to find that the content is 4 atomic % to 45 atomic %.

[0062] The optical density (OD) value, which is an index representing the contrast in light intensity between the reflective portion and the absorbing layer 4, is defined by (Equation 1), where Rm is the intensity of reflected light from a reflective portion where the absorbing layer 4 is not formed (for example, an area where the protective layer 3 is exposed), and Ra is the intensity of reflected light from the absorbing layer 4 (absorbent pattern layer 41). The larger the OD value, the better the contrast and high transferability will be, and if the OD value is less than 1, sufficient contrast will not be obtained and transfer performance will tend to deteriorate. For pattern transfer, OD>1 is preferred, and 1.5 or more is even more preferred.

[0063] Therefore, the OD value of the absorbent layer 4 is preferably 1.0 or more, and more preferably 1.5 or more. OD=−log(Ra / Rm) (Equation 1)

[0064] Conventional EUV reflective photomasks have used compound materials primarily composed of tantalum (Ta) for the absorber layer. In this case, a thickness of 40 nm or greater is required to achieve an OD value of 1 or greater. While the extinction coefficient k of conventional materials is 0.031, by using a compound material primarily composed of nickel (Ni), whose extinction coefficient k is 0.074, for the absorber layer 4, it is possible to reduce the thickness of the absorber layer 4 to 17 nm as long as the OD is at least 1. However, the extinction coefficient k of the absorber layer 4 varies significantly depending on the mixing ratio of oxygen (O) to nickel (Ni) and the crystallinity of the deposited material. A k value of less than 0.049 does not provide sufficient thinning effects. Therefore, to achieve a thinner absorber layer 4 than conventional materials, an extinction coefficient k of 0.049 or greater is preferred, with an extinction coefficient k of 0.051 or greater being even more preferred.

[0065] Furthermore, if the thickness of the absorption layer 4 exceeds 45 nm, the projection effect will be about the same as that of a conventional absorption layer with a thickness of 60 nm formed from a compound material mainly composed of tantalum (Ta). Furthermore, if the thickness of the absorption layer 4 is less than 17 nm, the light absorption performance may be reduced, resulting in a deterioration in transfer performance. Therefore, the thickness of the absorption layer 4 according to the embodiment of the present invention is preferably 17 nm or more and 45 nm or less, and more preferably 19 nm or more and 40 nm or less. Furthermore, if the film density of the absorption layer 4 is 4.0 g / cm or less, the film density of the absorption layer 4 may be 4.0 g / cm or less. ３ It is more preferable that the thickness of the absorption layer 4 is 17 nm or more and 45 nm or less.

[0066] Thus, when the thickness of the absorption layer 4 is within the range of 17 nm to 45 nm, the projection effect can be sufficiently reduced and the transfer performance can be improved compared to conventional absorption layers formed from a compound material containing tantalum (Ta) as the main component. Note that the above-mentioned "compound material containing tantalum (Ta) as the main component" refers to a compound material containing tantalum (Ta) in an amount of 50 atomic % or more relative to the number of atoms in the entire absorption layer.

[0067] 3 , the reflective photomask blank 10 according to the embodiment of the present invention may have a hard mask (etching mask layer) 5 formed on the absorber layer 4. The hard mask 5 according to the embodiment of the present invention has the function of further improving the processability of the absorber layer 4 when formed on the absorber layer 4.

[0068] It is desirable that the material constituting the hard mask 5 can be dry-etched with a gas different from the gas used when dry-etching the absorber layer 4. That is, when the absorber layer 4 formed of a material containing nickel (Ni) and oxygen (O) is etched with a chlorine-based gas, it is preferable to etch the hard mask 5 with a gas other than a chlorine-based gas. Furthermore, when the absorber layer 4 formed of a material containing nickel (Ni) and oxygen (O) is etched with a fluorine-based gas, it is preferable to etch the hard mask 5 with a gas other than fluorine gas.

[0069] The material constituting the hard mask 5 is preferably one or more selected from the group consisting of, for example, Ru, Ti, Cr, Ni, Co, Bi, Fe, Ag, Hf, Ta, Al, and Si, as well as oxides, nitrides, borides, oxynitrides, oxyborides, and oxynitride boride thereof.

[0070] 4, the hard mask 5 must remain on the absorption layer 4 until etching of the absorption layer 4 is complete. However, if the thickness of the hard mask 5 exceeds 30 nm, it becomes difficult to form a fine transfer pattern, and if the thickness of the hard mask 5 is less than 2 nm, it becomes difficult to form a film with a uniform thickness. Therefore, the thickness of the hard mask 5 is preferably in the range of 2 nm to 30 nm, and more preferably in the range of 5 nm to 10 nm. Note that the processing of the absorption layer 4 according to the embodiment of the present invention is not limited to dry etching. For example, the absorption layer 4 can also be processed using atomic layer etching (ALE).

[0071] Examples of the reflective photomask blank and the reflective photomask according to the present invention will be described below.

[0072] EXAMPLES Examples of the reflective photomask blank and reflective photomask according to the embodiments of the present invention will be described below.

[0073] Example 1 First, a method for producing a reflective photomask blank 10 will be described with reference to Fig. 5. First, as shown in Fig. 5, a reflective layer 2 formed by stacking 40 laminated films each consisting of a pair of silicon (Si) and molybdenum (Mo) is formed on a synthetic quartz substrate 1 having low thermal expansion characteristics. The thickness of the reflective layer 2 was set to 280 nm.

[0074] Next, a capping layer (protective layer) 3 made of ruthenium (Ru) was formed as an intermediate film on the reflective layer 2 to a thickness of 3.5 nm. Next, an absorbing layer 4 containing nickel (Ni) and oxygen (O) was formed on the capping layer 3 to a thickness of 47 nm. The atomic ratio of nickel (Ni) to oxygen (O) in the formed absorbing layer 4 was measured by EDX (energy dispersive X-ray analysis) and found to be 1:0.5. Furthermore, composition analysis was performed using Rutherford backscattering spectroscopy (RBS), and the total content of nickel (Ni) and oxygen (O) was found to be 100 atomic % of the entire absorbing layer 4. Furthermore, density calculations based on the RBS measurement results showed that the density of the absorbing layer 4 was 7.6 g / cm. ３ Furthermore, when measured by an XRD (X-ray diffraction apparatus), the absorbing layer 4 was found to be amorphous, although slight crystallinity was observed. In this example, the film thickness of the absorbing layer 4 was measured by a transmission electron microscope. In each of the examples and comparative examples described below, the film thickness of the absorbing layer 4 was also measured by a transmission electron microscope.

[0075] Next, a back surface conductive film 6 made of chromium nitride (CrN) was formed to a thickness of 100 nm on the surface of the substrate 1 on which the reflective layer 2 was not formed, thereby producing a reflective photomask blank 10 of Example 1.

[0076] A multi-target sputtering device was used to deposit each film (form each layer) on the substrate 1. The film thickness of each film was controlled by the sputtering time. The absorber layer 4 was deposited by reactive sputtering, with the O / Ni ratio (atomic ratio) being 0.5 by controlling the amount of oxygen introduced into the chamber during sputtering.

[0077] Next, a method for fabricating a reflective photomask 20 will be described with reference to FIGS. 6 to 9 . First, as shown in FIG. 6 , a positive chemically amplified resist (SEBP9012, manufactured by Shin-Etsu Chemical Co., Ltd.) was spin-coated to a thickness of 120 nm on the absorption layer 4 of the reflective photomask blank 10, and baked at 110° C. for 10 minutes to form a resist film 7. Next, a predetermined pattern was written on the resist film 7 using an electron beam lithography machine (JBX3030, manufactured by JEOL Ltd.). This was followed by a pre-baking process at 110° C. for 10 minutes, followed by a development process using a spray developer (SFG3000, manufactured by Sigma Meltec Co., Ltd.). As a result, a resist pattern 71 was formed, as shown in FIG. 7 .

[0078] Next, using the resist pattern 71 as an etching mask, the absorber layer 4 was patterned by dry etching using a chlorine-based gas. As a result, an absorber pattern (absorber pattern layer) 41 was formed in the absorber layer 4, as shown in FIG. 8 . Next, the resist pattern 71 was removed in a cleaning process, and a reflective photomask 20 according to this example was fabricated, as shown in FIG. 9 . In this example, the absorber pattern 41 formed in the absorber layer 4 included, on the reflective photomask 20 for transfer evaluation, a 64-nm line-and-space (LS) pattern, a 200-nm line-width LS pattern for measuring the absorber layer thickness using an AFM, and a 4-mm square absorber layer removal portion for measuring EUV reflectivity. In this example, the 64-nm line-width LS pattern was designed in both the x and y directions, as shown in FIG. 10 , to make it easier to see the impact of the projection effect due to EUV irradiation.

[0079] [Example 2] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1.5 and so that the film thickness was 51 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density of the absorbing layer 4 was 4.8 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 2 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0080] [Example 3] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 46 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 95 atomic % of the entire absorbing layer 4, and the remaining 5 atomic % was tungsten (W). Analysis of the absorbing layer 4 revealed that the film density was 6.8 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 3 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0081] [Example 4] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 47 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 51 atomic % of the entire absorbing layer 4, and the remaining 49 atomic % was tungsten (W). Analysis of the absorbing layer 4 revealed that the film density was 8.1 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 4 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0082] [Example 5] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.5 and so that the film thickness was 38 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 51 atomic % of the entire absorbing layer 4, and the remaining 49 atomic % was tantalum (Ta). Analysis of the absorbing layer 4 revealed that the film density was 8.0 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 5 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0083] [Example 6] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.5 and so that the film thickness was 46 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 95 atomic % of the entire absorbing layer 4, and the remaining 5 atomic % was tantalum (Ta). Analysis of the absorbing layer 4 revealed that the film density was 7.6 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 6 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0084] [Example 7] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.5 and so that the film thickness was 47 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 70 atomic % of the entire absorbing layer 4, and the remaining 30 atomic % was iridium (Ir). Analysis of the absorbing layer 4 revealed that the film density was 7.9 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 7 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0085] [Example 8] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 46 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 70 atomic % of the entire absorbing layer 4, and the remaining 30 atomic % was titanium (Ti). Analysis of the absorbing layer 4 revealed that the film density was 5.9 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 8 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0086] [Example 9] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.5 and so that the film thickness was 39 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 95 atomic % of the entire absorbing layer 4, and the remaining 5 atomic % was titanium (Ti). Analysis of the absorbing layer 4 revealed that the film density was 7.5 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 9 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0087] In this example, the absorbing layer 4 was formed to a film thickness of 17 nm. The reflective photomask blank 10 and the reflective photomask 20 of Example 10 were produced in the same manner as in Example 1, except for the film thickness.

[0088] In this example, the absorbing layer 4 was formed to a film thickness of 33 nm. The reflective photomask blank 10 and the reflective photomask 20 of Example 11 were produced in the same manner as in Example 1, except for the film thickness.

[0089] In this example, the absorbing layer 4 was formed to a film thickness of 45 nm. A reflective photomask blank 10 and a reflective photomask 20 of Example 12 were produced in the same manner as in Example 1, except for the film thickness.

[0090] [Example 13] In this example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 39 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density of the absorbing layer 4 was 6.7 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Example 13 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0091] In this example, the absorbing layer 4 was formed to a film thickness of 39 nm. The reflective photomask blank 10 and the reflective photomask 20 of Example 14 were produced in the same manner as in Example 2, except for the film thickness.

[0092] In this example, the absorbing layer 4 was formed to have a film thickness of 19 nm. The reflective photomask blank 10 and the reflective photomask 20 of Example 15 were produced in the same manner as in Example 1, except for the film thickness.

[0093] [Comparative Example 1] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio between nickel (Ni) and oxygen (O) was 1:0 and so that the film thickness was 32 nm. The absorbing layer 4 was also formed so that the content of nickel (Ni) was 100 atomic % of the entire absorbing layer 4. In other words, the absorbing layer 4 was formed using only nickel (Ni). Analysis of the absorbing layer 4 revealed that the film density was 8.9 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 1 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0094] [Comparative Example 2] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.1 and so that the film thickness was 34 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density was 8.8 g / cm ３The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 2 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0095] [Comparative Example 3] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.2 and the film thickness was 30 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density was 8.5 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 3 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0096] [Comparative Example 4] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.3 and the film thickness was 33 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density was 8.2 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 4 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0097] [Comparative Example 5] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:0.4 and the film thickness was 32 nm. Furthermore, the absorbing layer 4 was formed so that the total content of nickel (Ni) and oxygen (O) was 100 atomic % of the entire absorbing layer 4. Analysis of the absorbing layer 4 revealed that the film density was 7.9 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 5 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0098] [Comparative Example 6] In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 29 nm. Furthermore, the absorbing layer 4 was formed so that the content of tungsten (W) was 80 atomic % of the entire absorbing layer 4, and the total content of nickel (Ni) and oxygen (O) was the remaining 20 atomic %. Analysis of the absorbing layer 4 revealed that the film density was 8.5 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 6 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0099] Comparative Example 7 In this comparative example, the absorbing layer 4 was formed so that the atomic ratio of nickel (Ni) to oxygen (O) was 1:1 and so that the film thickness was 29 nm. Furthermore, the absorbing layer 4 was formed so that the content of tantalum (Ta) was 80 atomic % of the entire absorbing layer 4, and the total content of nickel (Ni) and oxygen (O) was the remaining 20 atomic %. Analysis of the absorbing layer 4 revealed that the film density was 8.3 g / cm ３ The reflective photomask blank 10 and the reflective photomask 20 of Comparative Example 7 were produced in the same manner as in Example 1, except for the formation of the absorbing layer 4.

[0100] [Reference Example] In addition to the above-mentioned examples and comparative examples, a reflective photomask having a tantalum (Ta)-based absorption pattern layer according to the prior art was also compared as a reference example. As with the above-mentioned examples and comparative examples, the reflective photomask blank had a reflective layer formed by stacking 40 laminated films each consisting of a pair of silicon (Si) and molybdenum (Mo) on a synthetic quartz substrate having low thermal expansion characteristics, and a ruthenium (Ru) capping layer 3 with a thickness of 3.5 nm. The absorption layer 4 formed on the capping layer 3 was a 2 nm thick TaBO film formed on a 58 nm thick TaBN film. As with the above-mentioned examples and comparative examples, the patterned absorption layer 4 was used for evaluation.

[0101] That is, in this reference example, a TaBO layer with a thickness of 2 nm was formed on a TaBN layer with a thickness of 58 nm, and used as the absorber layer 4. Then, a reflective photomask blank 10 and a reflective photomask 20 of the reference example were produced in the same manner as in Example 1, except for the formation of the absorber layer 4.

[0102] The evaluation items evaluated in this example will be described below. (Magnetic Properties) In each of the above-mentioned Examples and Comparative Examples, the produced reflective photomask blank 10 was cut into 1 cm square pieces, and the magnetic properties of the absorbing layer 4 provided on the reflective photomask blank 10 were measured for the cut reflective photomask blank 10 using a vibrating sample magnetometer (VSM). In this way, the magnetic susceptibility of the reflective photomask blank 10 (absorbing layer 4) according to each Example and Comparative Example was obtained.

[0103] Table 1 shows the magnetic properties (measurement results) of the reflective photomask blanks according to the examples and comparative examples. －５ If the value is less than 10 (emu), it is evaluated as "Good (passed because it has been demagnetized)." －５ (emu) or more is indicated as "x (failed because non-magneticization was not achieved)."

[0104] It was confirmed that no magnetism was detected in the absorber layer 4 made of a material containing a total of 50 atomic % or more of nickel (Ni) and oxygen (O) and having an atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) of 0.5 or more, i.e., the absorber layers 4 of Examples 1 to 15. However, when a total of 50 atomic % or more of nickel (Ni) and oxygen (O) was contained and the atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) was less than 0.5, magnetism was detected in the absorber layer 4, and it was confirmed that the absorber layer 4 had not been made non-magnetizable.

[0105] (Positional Accuracy of Electron Beam Lithography) If the absorber layer 4 is magnetic, the positional accuracy of electron beam lithography may be reduced by the magnetic field emitted from the absorber layer 4. Therefore, in each of the above-described Examples and Comparative Examples, electron beam lithography was performed on the prepared reflective photomask blank 10, and the positional accuracy was measured.

[0106] Table 1 shows the results (measurement results) of the positional accuracy of electron beam lithography for the reflective photomask blanks 10 according to each of the examples and comparative examples. In this evaluation, samples with a positional accuracy of less than 100 nm were marked "Good", and all other samples were marked "Poor". The sample with the best positional accuracy among the samples compared was marked "Excellent". As a result, it was confirmed that the samples in which magnetism was detected by a vibrating sample magnetometer (VSM) did not satisfy the standard value for positional accuracy.

[0107] (Reflectance) In each of the above-mentioned Examples and Comparative Examples, the reflectance Ra of the absorption pattern layer 41 region (see FIG. 10 ) of the fabricated reflective photomask 20 was measured using a reflectance measurement device for EUV light. Also, the reflectance Rm of the reflective portion 8 (see FIG. 10 ) where the absorption pattern layer 41 was not formed was measured using the reflectance measurement device for EUV light. In this way, the OD value of the reflective photomask 20 according to each Example and Comparative Example was calculated using the above-mentioned Equation 1.

[0108] As mentioned above, if the OD value is less than 1.0, sufficient contrast cannot be obtained and transfer performance may deteriorate. Therefore, in this evaluation, if the OD value is 1.0 or more, there is no problem with transfer performance and it is judged as "pass."

[0109] (Wafer Exposure Evaluation: Measurement of HV Bias) Using an EUV exposure apparatus (NXE3300B: manufactured by ASML), the absorption pattern 41 of the reflective photomask 20 produced in each Example and Comparative Example was transferred and exposed onto a semiconductor wafer coated with an EUV positive chemically amplified resist. At this time, the exposure dose was adjusted so that the LS pattern in the x direction shown in FIG. 10 was transferred as designed. Specifically, in this exposure test, the LS pattern in the x direction shown in FIG. 10 (line width 64 nm) was exposed so that it had a line width of 16 nm on the semiconductor wafer. The transferred resist pattern was observed and line width measured using an electron beam dimension measuring machine, and changes in the HV bias were compared by simulation.

[0110] The HV bias is the difference in line width of the transferred pattern depending on the orientation of the mask pattern, that is, the difference between the line width in the horizontal (H) direction and the line width in the vertical (V) direction. The line width in the H direction indicates the line width of the linear pattern perpendicular to the plane formed by the incident light and the reflected light (hereinafter sometimes referred to as the "incident plane"), and the line width in the V direction indicates the line width of the linear pattern parallel to the incident plane. In other words, the line width in the H direction is the length in the direction parallel to the incident plane, and the line width in the V direction is the length in the direction perpendicular to the incident plane.

[0111] The evaluation method was based on the magnitude of the HV bias compared to when an existing tantalum (Ta) mask shown in Table 1 was used as a reference example. That is, when the LS pattern in the x direction was adjusted to be transferred as designed, the LS pattern in the y direction was transferred as designed, and the HV bias was smaller than when an existing tantalum (Ta) mask was used, the result was deemed "pass." When the LS pattern in the x direction was adjusted to be transferred as designed, but was not transferred as designed (the LS pattern in the y direction was not resolved), or when the HV bias was larger than when an existing tantalum (Ta) mask was used, the result was deemed "fail."

[0112] The evaluation results are shown in Table 1. In addition to the evaluation results, Table 1 also shows the refractive index n and the extinction coefficient k.

[0113]

[0114] Table 1 shows a comparison of the OD values ​​of each example and each comparative example. As mentioned above, when the OD value is less than 1.0, sufficient contrast cannot be obtained and transfer performance deteriorates. Therefore, when the OD value is 1.0 or more, there is no problem with transfer performance and it is judged as "pass."

[0115] The OD value of the reflective photomask (reflection photomask of reference example) having a conventional tantalum (Ta)-based absorption pattern layer with a film thickness of 60 nm was 1.68, whereas the OD value of the reflective photomask 20 of Example 1 was 2.890, the OD value of the reflective photomask 20 of Example 2 was 1.600, the OD value of the reflective photomask 20 of Example 3 was 2.438, the OD value of the reflective photomask 20 of Example 4 was 2.071, the OD value of the reflective photomask 20 of Example 5 was 1.735, the OD value of the reflective photomask 20 of Example 6 was 3.386, and the OD value of the reflective photomask 20 of Example 7 was 1.68. The OD value of the reflective photomask 20 of Example 8 was 3.514, the OD value of the reflective photomask 20 of Example 9 was 1.843, the OD value of the reflective photomask 20 of Example 10 was 1.040, the OD value of the reflective photomask 20 of Example 11 was 1.894, the OD value of the reflective photomask 20 of Example 12 was 1.793, the OD value of the reflective photomask 20 of Example 13 was 2.045, the OD value of the reflective photomask 20 of Example 14 was 1.545, and the OD value of the reflective photomask 20 of Example 15 was 1.049. Furthermore, in the comparative examples, the OD value of the reflective photomask 20 of Comparative Example 1 was 2.673, the OD values ​​of the reflective photomasks 20 of Comparative Examples 2 to 4 were immeasurable, the OD value of the reflective photomask 20 of Comparative Example 5 was 2.180, the OD value of the reflective photomask 20 of Comparative Example 6 was 0.817, and the OD value of the reflective photomask 20 of Comparative Example 7 was 0.940. That is, the OD values ​​of Comparative Examples 2 to 4 and Comparative Examples 6 to 7 were less than 1.0 or immeasurable, and did not satisfy the criteria for "pass."

[0116] More specifically, it was confirmed that the absorber layers 4 made of materials containing a total of 50 atomic % or more of nickel (Ni) and oxygen (O) and having an atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) of 0.5 or more, i.e., the absorber layers 4 of Examples 1 to 15, had OD values ​​of 1.0 or more and satisfied the "pass" criteria.

[0117] On the other hand, it was confirmed that the OD value could not be measured for the absorber layers 4 of materials in which the atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) was less than 0.5, i.e., Comparative Examples 2 to 4. It was also confirmed that the OD value was less than 1.0 for the absorber layers 4 of materials that did not contain a total of 50 atomic % or more of nickel (Ni) and oxygen (O), i.e., Comparative Examples 6 to 7, and did not satisfy the "pass" criterion. It was confirmed that the OD value was 1.0 or more for the absorber layers 4 of Comparative Examples 1 and 5, and therefore satisfied the "pass" criterion.

[0118] Table 1 shows a comparison of the HV bias of each example and each comparative example. As described above, the evaluation method was based on the magnitude of the HV bias compared to when an existing tantalum (Ta) mask was used. That is, when the LS pattern in the x direction was adjusted to be transferred as designed, the LS pattern in the y direction was transferred as designed, and the HV bias was smaller than when an existing tantalum (Ta) mask was used, the result was deemed "pass." When the LS pattern in the x direction was adjusted to be transferred as designed, but was not transferred as designed (the LS pattern in the y direction was not resolved), or when the HV bias was larger than when an existing tantalum (Ta) mask was used, the result was deemed "fail." As a result of patterning with EUV light using a reflective photomask with a conventional tantalum (Ta)-based absorption pattern layer with a thickness of 60 nm, the HV bias was 5.20 nm. In contrast, the HV bias of Example 1 was 4.743 nm, the HV bias of Example 2 was 4.166 nm, the HV bias of Example 3 was 3.997 nm, the HV bias of Example 4 was 4.204 nm, the HV bias of Example 5 was 2.992 nm, the HV bias of Example 6 was 4.141 nm, the HV bias of Example 7 was 5.027 nm, the HV bias of Example 8 was 3.487 nm, the HV bias of Example 9 was 3.378 nm, the HV bias of Example 10 was 1.079 nm, the HV bias of Example 11 was 2.821 nm, the HV bias of Example 12 was 4.154 nm, the HV bias of Example 13 was 3.070 nm, the HV bias of Example 14 was 2.586 nm, and the HV bias of Example 15 was 1.306 nm. Furthermore, in the comparative examples, the HV bias of Comparative Example 1 was 2.877 nm, the HV bias of each of Comparative Examples 2 to 4 was unmeasurable, the HV bias of Comparative Example 5 was 2.655 nm, the HV bias of Comparative Example 6 was 1.565 nm, and the HV bias of Comparative Example 7 was 1.772 nm. That is, the HV bias of Comparative Example 1 and Comparative Examples 5 to 7 was smaller than that when an existing tantalum (Ta) mask was used, and satisfied the "pass" criteria.

[0119] In contrast, the HV bias was immeasurable in Comparative Examples 2 to 4, and the patterning using EUV light resulted in worse transferability compared to conventional Ta-based photomasks. More specifically, it was confirmed that the HV bias was smaller than that when a conventional tantalum (Ta) mask was used in the absorber layer 4 of a material containing a total of 50 atomic % or more of nickel (Ni) and oxygen (O) and having an atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) of 0.5 or more, i.e., the absorber layers 4 of Examples 1 to 15, was smaller than that when a conventional tantalum (Ta) mask was used, and satisfied the "pass" criteria.

[0120] On the other hand, it was confirmed that the HV bias could not be measured for the absorber layers 4 of materials in which the atomic ratio (O / Ni) of nickel (Ni) to oxygen (O) was less than 0.5, i.e., Comparative Examples 2 to 4. It was confirmed that the HV bias was smaller for the absorber layers 4 of Comparative Example 1 and Comparative Examples 5 to 7 than when an existing tantalum (Ta) mask was used, and that these satisfied the "pass" criteria.

[0121] Table 1 shows the overall evaluation of magnetism, writing position accuracy, OD value, and HV bias. Reflective photomasks 20 that were all judged to be "pass" in the evaluations of magnetism, writing position accuracy, OD value, and HV bias, i.e., reflective photomasks 20 that can suppress or reduce the projection effect and improve transfer performance by suppressing the decrease in writing accuracy that may occur when electron beam writing is performed on a resist film formed on an absorbing layer despite using a magnetic material, were marked with "○" in the "Overall Evaluation" column. On the other hand, reflective photomasks 20 that were judged to be "fail" in at least one of the evaluations of magnetism, writing position accuracy, OD value, and HV bias, i.e., reflective photomasks 20 that could not sufficiently suppress or reduce the projection effect or that showed a decrease in writing accuracy and insufficient transfer performance when electron beam writing was performed on a resist film formed on an absorbing layer, were marked with "×" in the "Overall Evaluation" column. Note that, since conventional Ta-based photomasks were used for comparison, they were marked with "△" in the "Overall Evaluation" column.

[0122] As a result, if the reflective photomask 20 has an absorption pattern layer 41 containing nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorption layer 4, and the atomic ratio of oxygen (O) to nickel (Ni) (O / Ni) is 0.5 or more, the drawing position accuracy, optical density (OD value), and HV bias are all good, and therefore the projection effect can be reduced, and the drawing accuracy is sufficient, resulting in high transfer performance.

[0123] Furthermore, for example, this embodiment can have the following configurations: (1) A reflective photomask blank for producing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in total at 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio of the oxygen (O) to the nickel (Ni) (O / Ni) is 0.5 or more. (2) The reflective photomask blank according to (1) above, wherein the absorbing layer contains tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorbing layer. (3) The reflective photomask blank according to (1) above, wherein the absorption layer contains tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer. (4) The reflective photomask blank according to any one of (1) to (3) above, wherein the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 1.0 or more. (5) The reflective photomask blank according to any one of (1) to (4) above, wherein the absorption layer contains 50 atomic % or more of the nickel (Ni) relative to the total number of atoms in the absorption layer. (6) The film density of the absorption layer is 4.0 g / cm ３(9) The reflective photomask blank according to any one of (1) to (5) above, wherein the film thickness of the absorption layer is in the range of 17 nm to 45 nm. (10) The reflective photomask blank according to any one of (1) to (6) above, wherein the film thickness of the absorption layer is in the range of 19 nm to 40 nm. (11) The reflective photomask blank according to any one of (1) to (7) above, further comprising an etching mask layer on the absorption layer. (12) The reflective photomask blank according to (10) above, wherein the film thickness of the etching mask layer is 30 nm or less. (10) A reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio of the oxygen (O) to the nickel (Ni) (O / Ni) is 0.5 or more. (11) The reflective photomask according to (10), wherein the absorbing layer contains tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorbing layer. (12) The reflective photomask according to (10), wherein the absorption layer contains tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer. (13) The reflective photomask according to any one of (10) to (12), wherein the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 1.0 or more. (14) The reflective photomask according to any one of (10) to (13), wherein the absorption layer contains 50 atomic % or more of the nickel (Ni) relative to the total number of atoms in the absorption layer. (15) The film density of the absorption layer is 4.0 g / cm ３(16) The reflective photomask according to any one of (10) to (14) above, wherein the thickness of the absorption layer is in the range of 17 nm to 45 nm. (16) The reflective photomask according to any one of (10) to (15) above, wherein the thickness of the absorption layer is in the range of 19 nm to 40 nm. (17) A method for manufacturing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: forming a reflective layer including a multilayer film on a substrate; and forming an absorption layer on the reflective layer, wherein the absorption layer contains nickel (Ni) and oxygen (O) in total at 50 atomic % or more with respect to the total number of atoms in the absorption layer, and the atomic ratio of the oxygen (O) to the nickel (Ni) (O / Ni) is 0.5 or more. (18) A method for manufacturing a reflective photomask using the reflective photomask blank according to any one of (1) to (9) above, comprising the steps of: forming the reflective layer including a multilayer film on the substrate; and forming the absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more. (19) A method for manufacturing a reflective photomask according to any one of (10) to (16) above, comprising the steps of: forming the reflective layer including a multilayer film on the substrate; and forming the absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

[0124] The reflective photomask according to the present invention can be suitably used to form fine patterns by EUV exposure in the manufacturing process of semiconductor integrated circuits and the like.

[0125] DESCRIPTION OF SYMBOLS 1... Substrate 2... Reflective layer 3... Capping layer (protective layer) 4... Absorbing layer 41... Absorbing pattern (absorbent pattern layer) 5... Hard mask (etching mask layer) 10... Reflective photomask blank 20... Reflective photomask 6... Back surface conductive film 7... Resist film 71... Resist pattern 8... Reflecting portion

Claims

1. A reflective photomask blank for producing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio of the oxygen (O) to the nickel (Ni) (O / Ni) is 0.5 or more.

2. The reflective photomask blank according to claim 1, wherein the absorption layer contains tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in an amount within the range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer.

3. A reflective photomask blank according to claim 1, wherein the absorption layer contains tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer.

4. The reflective photomask blank according to claim 1, wherein the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is 1.0 or more.

5. The reflective photomask blank according to claim 1, wherein the absorption layer contains nickel (Ni) in an amount of 50 atomic % or more relative to the total number of atoms in the absorption layer.

6. The film density of the absorbent layer is 4.0 g / cm ３ The reflective photomask blank according to claim 1 , wherein the absorption layer has a thickness in the range of 17 nm to 45 nm.

7. The reflective photomask blank according to claim 1, wherein the film thickness of the absorption layer is in the range of 19 nm to 40 nm.

8. The reflective photomask blank according to claim 1, further comprising an etching mask layer on the absorbing layer.

9. The reflective photomask blank according to claim 8, wherein the etching mask layer has a thickness of 30 nm or less.

10. A reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

11. The reflective photomask according to claim 10, wherein the absorption layer contains tantalum (Ta), iridium (Ir), tungsten (W), palladium (Pd), chromium (Cr), ruthenium (Ru), molybdenum (Mo), or silicon (Si) in an amount within the range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer.

12. The reflective photomask according to claim 10, wherein the absorption layer contains tantalum (Ta) or iridium (Ir) in a range of 5 atomic % to 50 atomic % relative to the total number of atoms in the absorption layer.

13. The reflective photomask according to claim 10, wherein the atomic ratio (O / Ni) of oxygen (O) to nickel (Ni) is 1.0 or more.

14. The reflective photomask according to claim 10, wherein the absorption layer contains nickel (Ni) in an amount of 50 atomic % or more relative to the total number of atoms in the absorption layer.

15. The film density of the absorbent layer is 4.0 g / cm ３ The reflective photomask according to claim 10 , wherein the absorption layer has a thickness in the range of 17 nm to 45 nm.

16. The reflective photomask according to claim 10, wherein the thickness of the absorption layer is within the range of 19 nm to 40 nm.

17. A method for manufacturing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising the steps of: forming a reflective layer including a multilayer film on a substrate; and forming an absorbing layer on the reflective layer, wherein the absorbing layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorbing layer, and the atomic ratio of the oxygen (O) to the nickel (Ni) (O / Ni) is 0.5 or more.

18. A method for manufacturing a reflective photomask using a reflective photomask blank according to any one of claims 1 to 9, comprising the steps of: forming the reflective layer including a multilayer film on the substrate; and forming the absorption layer on the reflective layer, wherein the absorption layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorption layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

19. A method for manufacturing a reflective photomask according to any one of claims 10 to 16, comprising the steps of: forming the reflective layer including a multilayer film on the substrate; and forming the absorption layer on the reflective layer, wherein the absorption layer contains nickel (Ni) and oxygen (O) in a total amount of 50 atomic % or more relative to the total number of atoms in the absorption layer, and the atomic ratio (O / Ni) of the oxygen (O) to the nickel (Ni) is 0.5 or more.

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