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

Abstract

To provide: a reflective photomask which makes it possible to further improve the performance of transfer onto a semiconductor substrate, and comprises an absorption layer having excellent pattern processability and enabling electron beam correction etching; a reflective photomask blank used for manufacturing the reflective photomask; and a reflective photomask manufacturing method using the reflective photomask blank.SOLUTION: A reflective photomask blank 10 according to one embodiment of the present invention has a substrate 1, a reflection layer 2, and an absorption layer 4. The absorption layer 4 is formed of a material that contains Pt in an amount of 50 atom% or more and Ir within a range of 5 atom% or more but less than 50 atom%. The film thickness of the absorption layer 4 is within the range from 17 nm to 50 nm inclusive. The OD value of the absorption layer 4 is 1.0 or more. The absorption layer 4 is formed of a material that exhibits a high correction etching rate at the time of electron beam correction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflective photomask blank, a reflective photomask, and a method for manufacturing a reflective photomask. [Background technology]

[0002] In the semiconductor device manufacturing process, the miniaturization of semiconductor devices has led to increasing demands for miniaturization of photolithography technology. The minimum resolution dimension of the transfer pattern in photolithography depends heavily on the wavelength of the exposure light source, and the shorter the wavelength, the smaller the minimum resolution dimension. For this reason, exposure light sources are being 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] Light in the EUV region is absorbed at a high rate by most materials, and therefore, 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) on top of that, and forming a pattern on this light absorbing layer.

[0004] Furthermore, as mentioned above, EUV lithography cannot use refractive optics, which 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 light incident on the reflective photomask (EUV mask) and the light reflected from the 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 pattern transfer exposure is performed using an EUV mask fabricated using this mask blank, the relationship between the incident direction of the EUV light and the orientation of the mask pattern can cause a decrease in contrast at the shadowed edge 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 of transfer performance.

[0007] Therefore, reflective photomask blanks are being considered that change the light absorption layer from tantalum (Ta) to a material with high absorbency (extinction coefficient k) for EUV light, or that add a highly absorbent material to tantalum (Ta). For example, Patent Document 2 describes a reflective photomask blank whose light absorption layer is made of an alloy containing at least two materials selected from Pt, Zn, Au, NiO, Ag2O, Ir, Fe, SnO2, Co, etc.

[0008] However, some materials that are highly absorptive of EUV light are difficult to process using dry etching, and even if a photomask blank is formed (fabricated), there is a problem in that the light-absorbing layer on the photomask blank cannot be patterned. Furthermore, many materials with high EUV light absorption have an extremely slow etching rate when subjected to electron beam repair etching in the defect repair process of the photomask manufacturing process, which often makes it difficult to repair defects that occur in the light absorption layer. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5418293 [Patent Document 2] Special Publication No. 2019-527382 Summary of the Invention [Problem to be solved by the invention]

[0010] The present disclosure has been made in light of the above circumstances, and aims to provide a reflective photomask for patterning transfer using light with a wavelength in the extreme ultraviolet region as a light source, which is capable of further improving transfer performance to a semiconductor substrate in patterning using light with a wavelength in the extreme ultraviolet region as a light source, and which has good pattern processability and is equipped with an absorbing layer that is capable of electron beam correction etching, a reflective photomask blank used for manufacturing such a reflective photomask, and a method for manufacturing a reflective photomask using such a reflective photomask blank. More specifically, the present disclosure aims to provide a reflective photomask in which a fine absorbing layer pattern is formed, the projection effect can be reduced, and furthermore, is capable of electron beam correction etching, even when a material with high light absorption is used as a constituent material of the absorbing layer of an EUV mask, a reflective photomask blank for manufacturing such a reflective photomask, and a method for manufacturing a reflective photomask using such a reflective photomask blank. [Means for solving the problem]

[0011] The present disclosure has been made to solve the above-mentioned problems, and a reflective photomask blank according to one embodiment of the present disclosure is a reflective photomask blank for producing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, the reflective photomask blank comprising: a substrate; a reflective layer including a multilayer film formed on the substrate; and an absorbing layer formed on the reflective layer, the absorbing layer being formed of a material containing platinum (Pt) at 50 atomic % or more relative to the total number of atoms in the absorbing layer, and iridium (Ir) in a range of 5 atomic % or more and less than 50 atomic % relative to the total number of atoms in the absorbing layer, the absorbing layer having a film thickness in a range of 17 nm or more and 50 nm or less, the OD value (Optica Density) of the absorbing layer being 1.0 or more, and the absorbing layer being formed of a material having a high correction etching rate during electron beam correction.

[0012] Furthermore, a reflective photomask according to one embodiment of the present disclosure is 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 absorption pattern layer on which an absorption layer pattern serving as a transfer pattern is formed, wherein the absorption pattern layer is formed of a material containing platinum (Pt) at 50 atomic % or more relative to the total number of atoms in the absorption pattern layer, and iridium (Ir) at a range of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms in the absorption pattern layer, the film thickness of the absorption pattern layer is in the range of 17 nm or more and 50 nm or less, the OD value (Optica Density) of the absorption pattern layer is 1.0 or more, and the absorption pattern layer is formed of a material with a fast correction etching rate during electron beam correction.

[0013] Furthermore, a method for manufacturing a reflective photomask according to one embodiment of the present disclosure is a method for manufacturing a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, and includes the steps of forming a reflective layer including a multilayer film on a substrate, and forming an absorption pattern layer having an absorption layer pattern that will become a transfer pattern on the reflective layer, wherein the absorption pattern layer is formed from a material that contains platinum (Pt) at 50 atomic % or more relative to the total number of atoms in the absorption pattern layer, and iridium (Ir) at a range of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms in the absorption pattern layer, the film thickness of the absorption pattern layer is in the range of 17 nm or more and 50 nm or less, the OD value (Optica Density) of the absorption pattern layer is 1.0 or more, and the absorption pattern layer is formed from a material that has a fast correction etching rate during electron beam correction. [Effects of the Invention]

[0014] A reflective photomask blank according to one embodiment of the present disclosure enables the creation of an absorber layer that has good pattern processability and is capable of electron beam correction etching. That is, a reflective photomask blank according to one embodiment of the present disclosure enables the formation of a fine absorber layer pattern in the absorber layer, and can provide a reflective photomask blank that is capable of electron beam correction etching. In other words, a reflective photomask blank according to one embodiment of the present disclosure enables the formation of a fine absorber layer pattern in the absorber layer, and can further improve the transfer performance to a semiconductor substrate in patterning using light with a wavelength in the extreme ultraviolet region as a light source compared to conventional techniques, and can provide a reflective photomask blank with an absorber layer that is capable of electron beam correction etching.

[0015] Furthermore, a reflective photomask according to an embodiment of the present disclosure can provide a reflective photomask having an absorbing layer (absorbent pattern layer) that has good pattern processability and is capable of electron beam correction etching. That is, a reflective photomask according to an embodiment of the present disclosure has a fine absorbing layer pattern formed thereon, and compared to conventional techniques, can further improve the transfer performance onto a semiconductor substrate in patterning using light in the extreme ultraviolet wavelength range as a light source, and also enables electron beam correction etching.

[0016] Furthermore, the method for manufacturing a reflective photomask according to an embodiment of the present disclosure makes it possible to manufacture a reflective photomask having an absorbing layer (absorbent pattern layer) that has good pattern processability and is capable of electron beam correction etching. In other words, the method for manufacturing a reflective photomask according to an embodiment of the present disclosure makes it possible to form a fine absorbing layer pattern in the absorbing layer, and to manufacture a reflective photomask that can further improve the transfer performance onto a semiconductor substrate in patterning using light with a wavelength in the extreme ultraviolet region as a light source, as compared with conventional techniques, and that is capable of electron beam correction etching.

[0017] As described above, one aspect of the present disclosure provides a reflective photomask for patterning transfer that uses light with a wavelength in the extreme ultraviolet region as a light source, which can further improve the transfer performance onto a semiconductor substrate in patterning using light with a wavelength in the extreme ultraviolet region as a light source compared to conventional techniques, and which has good pattern processability and is equipped with an absorption layer that allows electron beam correction etching, as well as a reflective photomask blank used to manufacture the reflective photomask, and a method for manufacturing a reflective photomask using the reflective photomask blank. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an embodiment of the present invention. [Figure 2]1 is a schematic cross-sectional view showing the structure of a reflective photomask according to an embodiment of the present invention. [Figure 3] 1 is a graph showing the optical constants of various metal materials at the wavelength of EUV light. [Figure 4] 10 is a schematic cross-sectional view showing side etching after electron beam correction etching of the absorbing pattern layer. [Figure 5] FIG. 2 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to another embodiment of the present invention. [Figure 6] 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an embodiment of the present invention. [Figure 7] 1A to 1C are schematic cross-sectional views illustrating a manufacturing process of a reflective photomask according to an embodiment of the present invention. [Figure 8] 1A to 1C are schematic cross-sectional views illustrating a manufacturing process of a reflective photomask according to an embodiment of the present invention. [Figure 9] 1A to 1C are schematic cross-sectional views illustrating a manufacturing process of a reflective photomask according to an embodiment of the present invention. [Figure 10] 1 is a schematic cross-sectional view showing the structure of a reflective photomask according to an embodiment of the present invention. [Figure 11] 1 is a schematic plan view showing the shape of a design pattern of a reflective photomask according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] 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 an 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.

[0021] (Overall structure) As shown in FIG. 1, a reflective photomask blank 10 according to an embodiment of the present invention includes a substrate 1, a reflective layer 2 formed on the substrate 1, a capping layer 3 formed on the reflective layer 2, and an absorbing layer 4 formed on the capping layer 3.

[0022] (substrate) The substrate 1 according to the embodiment of the present invention may be, for example, a flat Si substrate, a synthetic quartz substrate, etc. Furthermore, low thermal expansion glass containing titanium may be used for the substrate 1, but the present invention is not limited to these as long as the material has a small thermal expansion coefficient.

[0023] (reflective layer) The reflective layer 2 according to the embodiment of the present invention may be a multilayer reflective film made of a combination of materials having significantly different refractive indices for EUV light, as long as it reflects EUV light (extreme ultraviolet light), which is exposure light. The reflective layer 2 including the multilayer reflective film may be formed by repeatedly stacking layers of a combination of Mo (molybdenum) and Si (silicon), or Mo (molybdenum) and Be (beryllium), for example, for about 40 periods.

[0024] (capping layer) The capping layer 3 according to the embodiment of the present invention is formed of a material that is resistant to dry etching that is performed when forming a transfer pattern (mask pattern) on the absorber layer 4, and functions as an etching stopper that prevents damage to the reflective layer 2 when etching the absorber layer 4. The capping layer 3 is formed of, for example, Ru (ruthenium). Here, the capping layer 3 may not be formed depending on the material of the reflective layer 2 and the etching conditions. Furthermore, 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 that uses the principle of an electrostatic chuck to fix the reflective photomask 20 when it is placed in an exposure machine.

[0025] (Absorption layer) As shown in FIG. 2, an absorption pattern (absorption pattern layer) 41 of a reflective photomask 20 is formed by removing a portion of the absorption layer 4 of a reflective photomask blank 10, i.e., by patterning the absorption layer 4. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 2. However, the absorption pattern 41 obstructs the light path, resulting in a projection effect, which can degrade transfer performance onto a wafer (semiconductor substrate). This degradation in transfer performance can be reduced by reducing the thickness of the absorption layer 4, which absorbs EUV light. To reduce the thickness of the absorption layer 4, it is preferable to use a material that is more absorbent of EUV light than conventional materials, i.e., a material with a high extinction coefficient k at a wavelength of 13.5 nm.

[0026] Figure 3 is a graph showing the optical constants of various metal materials for EUV light with a wavelength of 13.5 nm. The horizontal axis of Figure 3 represents the refractive index n, and the vertical axis represents the extinction coefficient k. The extinction coefficient k of tantalum (Ta), the main material of the conventional absorption layer 4, is 0.041. If a compound material is used that has a larger extinction coefficient k, it will be possible to make the absorption layer 4 thinner than conventional materials.

[0027] Materials satisfying the above-described extinction coefficient k (hereinafter also referred to as "high extinction coefficient materials") include, for example, silver (Ag), platinum (Pt), indium (In), cobalt (Co), tin (Sn), nickel (Ni), and tellurium (Te), as shown in Figure 3. However, these high extinction coefficient materials often have low volatility of the halide of their constituent elements and poor (low) dry etching properties, making them unable to be processed, such as patterned, into an absorbing layer, or cannot withstand the heat during photomask fabrication or EUV exposure due to the low melting points of their constituent elements. For this reason, photomasks having an absorbing layer formed from the above-described high extinction coefficient materials often lack practical use as photomasks.

[0028] To avoid the above-mentioned drawbacks, the absorber layer 4 of the reflective photomask blank 10 of this embodiment or the absorber pattern layer 41 of the reflective photomask 20 of this embodiment is formed from a material (alloy) containing platinum (Pt) and iridium (Ir). Platinum (Pt) alone is highly resistant to liquids used in cleaning photomasks and also highly resistant to hydrogen radicals. However, it is known to be resistant to etching by fluorine-based gases (fluorine-containing etching gases such as CF4 gas and SF6 gas) or chlorine-based gases (chlorine-containing etching gases such as Cl2 gas and HCl gas) commonly used in dry etching. In this case, the dry etching rate is low, so the resist film formed on the absorber layer 4 must be thick, which often makes it difficult to form a fine absorber layer pattern. In contrast, mixing iridium (Ir) with platinum (Pt) increases the etching rate while maintaining high hydrogen radical resistance and high cleaning resistance. This allows the resist film on the absorber layer 4 to be thin, thereby easing the difficulty of forming an absorber pattern layer 41 made of a high-extinction coefficient material and having a fine absorber layer pattern.

[0029] In general, dry etching occurs when electrons collide with the introduced gas in the plasma, generating active radicals and reactive ions dissociated into various forms, which then cause etching. Therefore, the more volatile products with a low boiling point are formed on the etching surface, the more easily the material is etched. The boiling point and vapor pressure of the reaction products between the material to be etched and the introduced gas are indicators of this. In other words, the lower the boiling point of the reaction product, the more easily it vaporizes, the higher its vapor pressure and the easier it is to exhaust. In etching the absorber layer 4 when fabricating the reflective photomask 20, "easily etched by fluorine-based gases" means that the boiling point of at least one fluorine-based compound produced by etching with a fluorine-based gas is 300°C or lower, and "resistant to etching by fluorine-based gases" means that the boiling point of a stoichiometrically possible fluoride produced by etching with a fluorine-based gas is higher than 300°C. Similarly, for chlorine-based gases, "easily etched by chlorine-based gases" means that the boiling point of at least one chlorine-based compound produced by etching with a chlorine-based gas is 300°C or lower, and "resistant to etching by chlorine-based gases" means that the boiling point of a stoichiometrically possible chloride produced by etching with a chlorine-based gas is higher than 300°C. Therefore, it is desirable that the material used for the absorption layer 4 is one that is easily etched by fluorine-based gas or chlorine-based gas, that is, a substance with a low boiling point of a fluorine-based compound or chlorine-based compound.

[0030] Table 1 shows the boiling points of metal halogen compounds. The values ​​in Table 1 are a compilation of values ​​found in various literature (e.g., CRC Handbook of Chemistry and Hydrology, 97th Edition (2016)) and websites. As shown in Table 1, examples of mixed materials that are easily etched with fluorine-based gases include iridium (Ir), tantalum (Ta), silicon (Si), ruthenium (Ru), and rhenium (Re). Examples of mixed materials that are easily etched with chlorine-based gases include indium (In), tantalum (Ta), silicon (Si), chromium (Cr), and tungsten (W). Oxides, nitrides, oxynitrides, and boron nitrides of these mixed materials may also be used as mixed materials.

[0031] By adding the elements listed in Table 1, the pattern processability and electron beam correction etching processability of the absorption layer 4 are slightly reduced, but the value of the extinction coefficient k of the absorption layer 4 (absorption pattern layer 41) can be increased.

[0032] [Table 1]

[0033] However, the above is an example of the etching gas and its reactivity, and the etching gas in this embodiment is not limited to two types, fluorine-based gas and chlorine-based gas. In addition to fluorine-based gas and chlorine-based gas, a mixed gas of these may be used, and a non-halogen gas such as oxygen gas or hydrogen gas may be contained to promote the reaction.

[0034] The relationship between whether the absorbing layer 4 (the absorbing pattern layer 41) can be etched and the boiling point of the fluorine-based compound or chlorine-based compound is merely an index and is not absolute.

[0035] Furthermore, even if the boiling point of the above-mentioned fluorine-based compound or chlorine-based compound is 300°C or lower, the above-mentioned etching may not be possible if, for example, the generated fluorine-based compound or chlorine-based compound has a property that makes it prone to re-adhesion. Furthermore, the processing of the absorption layer 4 in this embodiment is not limited to dry etching. For example, the absorption layer 4 can also be processed using atomic layer etching (ALE).

[0036] The material constituting the absorption layer 4 contains platinum (Pt) at 50 atomic % or more relative to the number of atoms constituting the entire absorption layer 4. The material constituting the absorption layer 4 preferably contains platinum (Pt) in the range of 50 atomic % to 95 atomic % relative to the number of atoms constituting the entire absorption layer 4, more preferably in the range of 55 atomic % to 90 atomic %, and even more preferably in the range of 60 atomic % to 80 atomic %.

[0037] The absorber layer 4 also contains iridium (Ir) in a range of 5 atomic % or more and less than 50 atomic % relative to the number of atoms constituting the entire absorber layer 4. This is because, although the EUV light absorption properties may be reduced if the absorber layer 4 contains components other than platinum (Pt), the reduction in EUV light absorption properties is very slight if the components other than platinum (Pt) are less than 50 atomic %, and there is almost no reduction in performance as the absorber layer 4 of the EUV mask.

[0038] Furthermore, although platinum (Pt) alone is difficult to process by dry etching, adding iridium (Ir) to platinum (Pt) improves processability by dry etching, making dry etching using a chlorine-based gas, a fluorine-based gas, or a mixed gas possible, allowing a reflective photomask blank to be processed into a reflective photomask. Specifically, if the iridium (Ir) content in the absorber layer 4 is within a range of 5 atomic % or more and less than 50 atomic % relative to the number of atoms constituting the entire absorber layer 4, the processability of the absorber layer 4 by dry etching can be improved while maintaining hydrogen radical resistance.

[0039] Furthermore, if the absorber layer pattern formed on the absorber pattern layer 41 is not formed as designed, correction (electron beam correction etching) may be performed. Electron beam correction etching refers to etching the absorption layer 4 by supplying an etching gas such as a fluorine-based gas (XeF2) and irradiating the area to be etched with an electron beam, thereby promoting the reactivity of the fluorine etchant.

[0040] However, platinum (Pt) has a relatively low etching rate with fluorine-based gases, and etching with fluorine-based gases takes an extremely long time. Therefore, as shown in Figure 4, when platinum (Pt) is etched with fluorine-based gases, damage in a direction perpendicular to the etching direction, known as repair side etching (BS), can occur. Furthermore, if the side etching is large, the line width of the area corrected by electron beam etching will be significantly off, which is one of the reasons for repair failure.

[0041] The inventors of the present application have found that adding iridium (Ir), a material that is easily etched by fluorine-based gases (i.e., a material whose boiling point of a fluorine-based compound is 300°C or less), to the absorber layer 4 improves the electron beam correction etching rate and suppresses the correction side etching amount BW to 2 nm or less. In other words, they have found that adding iridium (Ir) to platinum (Pt) improves the success rate of electron beam correction etching.

[0042] In the embodiment of the present invention, a material whose correction side etching amount BW by a fluorine-based gas is 2 nm or less is referred to as a “material whose correction etching rate is fast.” That is, in the embodiment of the present invention, the absorption layer 4 (absorption pattern layer 41) is a layer formed of a material whose film thickness is in the range of 17 nm to 50 nm and whose correction side etching amount BW is 2 nm or less.

[0043] Furthermore, in this embodiment, "good pattern processability" refers to a state in which, when the absorption pattern layer 41 is formed, the angle formed between the surface of the reflective layer 2 or the surface of the capping layer 3 and the side surface of the absorption pattern layer 41 in the pattern formation portion, and the elevation angle (so-called sidewall angle) based on the surface of the reflective layer 2 or the surface of the capping layer 3, is 80° or more.

[0044] If the iridium (Ir) content is less than 5 atomic % relative to the total number of constituent atoms of the absorber layer 4, it may not be possible to improve both the pattern processability of the absorber layer 4 by dry etching and the processability by electron beam correction etching. If the iridium (Ir) content is 50 atomic % or more relative to the total number of constituent atoms of the absorber layer 4, the absorbency of EUV light may decrease, making it impossible to achieve a thin absorber layer 4. If the iridium (Ir) content is 50 atomic % or more relative to the total number of constituent atoms of the absorber layer 4, the absorbency of EUV light may decrease, making it impossible to achieve a thin absorber layer 4.

[0045] Therefore, the content of iridium (Ir) is preferably in the range of 5 atomic % or more and less than 50 atomic % of the total number of constituent atoms of the absorption layer 4, more preferably in the range of 10 atomic % or more and 45 atomic % or less, and even more preferably in the range of 20 atomic % or more and 40 atomic % or less.

[0046] The above composition ratios of the materials constituting the absorption 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 whose platinum (Pt) content is 50 atomic % to 99 atomic % of all metal elements by Rutherford backscattering spectroscopy (RBS) may be found to contain 40 atomic % to 75 atomic % of all metal elements by analysis using X-ray photoelectron spectroscopy (XPS), or may be found to contain 45 atomic % to 100 atomic % of all metal elements by analysis using energy dispersive X-ray spectroscopy (EDX).

[0047] The processability of the absorption layer 4 is also affected by the crystallinity of the constituent material. Furthermore, the crystallinity also affects the smoothness of the film and the line edge roughness of the formed absorption pattern layer 41. For the reasons mentioned above, the absorption layer 4 in this embodiment is desirably formed of an amorphous film with low crystallinity. Materials with high crystallinity also have high surface roughness due to the formation of crystal grain boundaries. Therefore, the surface roughness (RMS) of the absorption layer 4 is preferably 0.4 nm or less, and more preferably 0.2 nm or less. Here, the "surface roughness (RMS) of the absorption layer 4" refers to the roughness (RMS) of the surface (surface) of the absorption layer 4 (absorption pattern layer 41) opposite the reflective layer 2 side.

[0048] In this embodiment, the surface roughness (RMS) may be measured using, for example, an atomic force microscope (AFM).

[0049] As described above, the material constituting the absorption layer 4 may contain platinum (Pt) in an amount of 50 atomic % or more and iridium (Ir) in a range of 5 atomic % or more and less than 50 atomic % with respect to the number of atoms constituting the entire absorption layer 4. The material may further contain, as a material other than platinum (Pt) and iridium (Ir), one or more elements selected from the group consisting of ruthenium (Ru), tantalum (Ta), titanium (Ti), chromium (Cr), indium (In), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), iodine (I), tellurium (Te), zinc (Zn), hafnium (Hf), tungsten (W), palladium (Pd), rhenium (Re), gallium (Ga), aluminum (Al), nitrogen (N), and boron (B) (hereinafter, for convenience, referred to as an "additive element group"). That is, the absorption layer 4 may further contain one or more elements selected from the above-mentioned group of additional elements in addition to platinum (Pt) and tantalum (Ta).

[0050] For example, by adding tellurium (Te), which is one of the elements included in the above-mentioned group of additional elements, to the absorption layer 4 (absorption pattern layer 41), the absorption properties for EUV light can be further improved and the thickness can be further reduced.

[0051] Furthermore, by adding silver (Ag), nickel (Ni), indium (In), or cobalt (Co) from the elements included in the group of added elements described above to the absorption layer 4 (absorption pattern layer 41), the processability of electron beam correction etching decreases compared to when other elements are added, but the absorption of EUV light is further improved, making it possible to further reduce the thickness.

[0052] Alternatively, by adding tantalum (Ta), silicon (Si), ruthenium (Ru), rhenium (Re), tungsten (W), bismuth (Bi), or iodine (I) from the elements included in the group of additive elements described above to the absorption layer 4 (absorption pattern layer 41), it is possible to further improve the processability of electron beam correction etching.

[0053] Furthermore, by adding chromium (Cr), boron (B), or hafnium (Hf) from among the elements included in the above-mentioned group of additive elements to the absorber layer 4 (absorber pattern layer 41), it is possible to make the film quality of the absorber layer 4 (absorber pattern layer 41) more amorphous. As a result, it is possible to improve the roughness and in-plane dimensional uniformity of the absorber layer pattern (mask pattern) after dry etching, or the in-plane uniformity of the transferred image.

[0054] The total content of the elements included in the additive element group may be the same as the content of iridium (Ir). That is, the absorber layer 4 and the absorber pattern layer 41 contain platinum (Pt), iridium (Ir), and one or more elements selected from the additive element group, and the total content of the elements included in the additive element group may be equal to or less than the content of iridium (Ir). More preferably, the total content of the elements included in the additive element group is within a range of 0.9 times or less the content of iridium (Ir), and even more preferably, the total content of the elements included in the additive element group is within a range of 0.6 times or less the content of iridium (Ir). With the above-described configuration, the absorber layer 4 can be provided with excellent transfer performance, excellent pattern processability and electron beam correction etching processability, and the various functions described above can be imparted.

[0055] The OD value of the absorbing pattern layer 41 will be described below. The optical density (OD) value, which is an index representing the contrast in light intensity between the reflective and absorbing portions, is defined by Equation 1, where Rm is the intensity of reflected light from the reflective portion, which is the region where part of the absorbing layer 4 has been removed to expose the reflective layer 2 and capping layer 3, and Ra is the intensity of reflected light from the absorbing portion, which is the region where the absorbing layer 4 remains. The higher the OD value, the better the contrast and high transferability will be. If the OD value is less than 1, sufficient contrast will not be obtained and transferability will tend to deteriorate. For pattern transfer, an OD greater than 1 is preferable, and an OD of 1.5 or greater is even more preferable.

[0056] Therefore, the OD value of the absorbent layer 4 (absorbent pattern layer 41) on which the transfer pattern is formed is preferably 1.0 or more, and more preferably 1.5 or more. OD = -log(Ra / Rm) (Equation 1)

[0057] As mentioned above, the absorber layer 4 (absorber pattern layer 41) of conventional EUV reflective photomasks has been formed from a compound material primarily composed of tantalum (Ta). 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, forming the absorber layer 4 from a compound material primarily containing platinum (Pt), whose extinction coefficient k is 0.058, enables the absorber layer 4 to be thinned to 17 nm for an OD value of 1 or greater. However, the extinction coefficient k of the entire absorber layer 4 varies significantly depending on the mixing ratio of iridium (Ir) to platinum (Pt) and the crystallinity of the deposited material. Therefore, a sufficient thinning effect is often not achieved when the extinction coefficient k of the entire absorber layer 4 is less than 0.049. Therefore, to achieve a thinner layer than conventional layers, the extinction coefficient k of the entire absorber layer 4 is preferably 0.049 or greater, and more preferably 0.051 or greater.

[0058] Furthermore, if the thickness of the absorber layer 4 exceeds 50 nm, the projection effect will be similar to that of a conventional absorber layer with a thickness of 60 nm formed from a compound material mainly composed of tantalum (Ta). Also, if the thickness of the absorber layer 4 exceeds 50 nm, the pattern processability of the absorber layer 4 and the processability of electron beam correction etching may be reduced. Therefore, the thickness of the absorber layer 4 according to this embodiment is in the range of 17 nm to 50 nm. That is, when the thickness of the absorber layer 4 is in the range of 17 nm to 50 nm, the projection effect can be sufficiently reduced and the transfer performance is improved compared to a conventional absorber layer formed of a compound material mainly containing tantalum (Ta).

[0059] The thickness of the absorbing layer 4 is more preferably in the range of 25 nm to 40 nm. When the thickness of the absorbing layer 4 is in the range of 25 nm to 40 nm, the projection effect can be further reduced compared to conventional absorbing layers, and the transfer performance is further improved.

[0060] The above-mentioned "main component" refers to a component that is contained in an amount of 50 atomic % or more relative to the number of atoms in the entire absorption layer. An oxide film (not shown) may be formed by oxidizing at least one of the upper surface of the absorption layer 4 or the upper surface and side surface of the absorption pattern layer 41. An oxide film (not shown) may be separately formed on at least one of the upper surface of the absorption layer 4 or the upper surface and side surface of the absorption pattern layer 41. The thickness of this oxide film is not particularly limited, but is, for example, in the range of 1 nm to 5 nm.

[0061] The oxide film described above may be a natural oxide film that is formed naturally when the reflective photomask blank 10 or the reflective photomask 20 is stored or when the reflective photomask blank 10 or the reflective photomask 20 is cleaned.

[0062] (hard mask) 5, a reflective photomask blank 10 according to an embodiment of the present invention may have a hard mask 5 formed on an absorber layer 4. When formed on the absorber layer 4, the hard mask 5 according to an embodiment of the present invention has the function of further improving the processability of the absorber layer 4. The material constituting the hard mask 5 is preferably a material that can be dry-etched with a gas different from the gas used to dry-etch the absorber layer 4. That is, when a material containing platinum (Pt) and iridium (Ir), which is the material for forming the absorber layer 4, is etched with a chlorine-based gas, it is preferable to use a gas other than a chlorine-based gas as the etching gas for the hard mask 5. Furthermore, when a material containing platinum (Pt) and iridium (Ir), which is the material for forming the absorber layer 4, is etched with a fluorine-based gas, it is preferable to use a gas other than a fluorine-based gas as the etching gas for the hard mask 5.

[0063] Therefore, it is preferable that the material constituting the hard mask 5 contains one or more selected from the group consisting of, for example, ruthenium (Ru), titanium (Ti), chromium (Cr), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), hafnium (Hf), tantalum (Ta), aluminum (Al), and silicon (Si), as well as their oxides, nitrides, borides, oxynitrides, oxyborides, and oxynitride boride. That is, the absorption layer 4 may contain platinum (Pt), iridium (Ir), and one or more elements selected from the above-mentioned group of additive elements, and the hard mask 5 may contain one or more elements selected from the group consisting of ruthenium (Ru), titanium (Ti), chromium (Cr), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), hafnium (Hf), tantalum (Ta), aluminum (Al), and silicon (Si), as well as oxides, nitrides, borides, oxynitrides, oxyborides, and oxynitride boride thereof.

[0064] The hard mask 5 must remain on the absorber layer 4 until etching of the absorber layer 4 is completed. However, if the thickness of the hard mask 5 exceeds 30 nm, it may be difficult to form a fine pattern. On the other hand, if the thickness of the hard mask 5 is less than 2 nm, the hard mask 5 may be too thin and it may be difficult to form the hard mask 5 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.

[0065] Examples of the reflective photomask blank and the reflective photomask according to the present invention will be described below.

[0066] [Example 1] First, a method for producing the reflective photomask blank 10 will be described with reference to FIG. First, as shown in Fig. 6, a reflective layer 2 formed by stacking 40 layers of a laminated film, each of which is 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. Next, a capping 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 absorber layer 4 containing platinum (Pt) and iridium (Ir) was formed to a thickness of 48 nm on the capping layer 3. Composition analysis of the formed absorber layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorber layer 4 was 70 atomic % and the iridium (Ir) content was 30 atomic %.

[0067] Furthermore, when the crystallinity of the absorption layer 4 was measured by XRD (X-ray diffraction), it was found to be amorphous although slight crystallinity was observed. Next, a back 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. A 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.

[0068] Next, a method for manufacturing the reflective photomask 20 will be described with reference to FIGS. First, as shown in Figure 7, a positive chemically amplified resist (SEBP9012: manufactured by Shin-Etsu Chemical Co., Ltd.) was spin-coated onto the absorption layer 4 of the reflective photomask blank 10 to a thickness of 120 nm, and baked at 110°C for 10 minutes to form a resist film 7.

[0069] Next, a predetermined pattern was written on the resist film 7 using an electron beam lithography machine (JBX3030, manufactured by JEOL Ltd.). Thereafter, a pre-baking process was performed at 110°C for 10 minutes, and then a development process was performed using a spray developer (SFG3000, manufactured by Sigma Meltec Co., Ltd.). As a result, a resist pattern 71 was formed as shown in FIG.

[0070] Next, using the resist pattern 71 as an etching mask, the absorbing layer 4 was patterned by dry etching mainly using a chlorine-based gas, thereby forming an absorbing pattern (absorbing pattern layer) 41 in the absorbing layer 4, as shown in FIG.

[0071] Next, the resist pattern 71 was removed in a cleaning process to produce a reflective photomask 20 of this example, as shown in FIG. 10. In this example, the absorption pattern 41 formed in the absorption layer 4 includes a 64 nm line-and-space (LS) pattern on the reflective photomask 20 for transfer evaluation, a 200 nm line-and-space (LS) pattern for measuring the film thickness of the absorption layer using an AFM, and a 4 mm square absorber layer removal portion for measuring EUV reflectivity. In this example, the 64 nm line-and-space (LS) pattern was designed in both the x and y directions, as shown in FIG. 11, so that the influence of the projection effect due to EUV irradiation could be more easily seen.

[0072] [Example 2] The absorbing layer 4 was formed so that the platinum (Pt) content of the absorbing layer 4 was 55 atomic % of the entire absorbing layer 4, and the iridium (Ir) content of the absorbing layer 4 was 45 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 36 nm. 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.

[0073] [Example 3] The absorbing layer 4 was formed so that the platinum (Pt) content of the absorbing layer 4 was 90 atomic % of the entire absorbing layer 4 and the iridium (Ir) content was 10 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 27 nm. 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.

[0074] [Example 4] A reflective photomask blank 10 and a reflective photomask 20 of Example 4 were produced in the same manner as in Example 1, except that the absorbing layer 4 was formed to a thickness of 19 nm.

[0075] [Example 5] A reflective photomask blank 10 and a reflective photomask 20 of Example 5 were produced in the same manner as in Example 1, except that the absorbing layer 4 was formed to a thickness of 33 nm.

[0076] [Example 6] An absorber layer 4 containing platinum (Pt), iridium (Ir), and tungsten (W) was formed to a thickness of 40 nm on the capping layer 3. Furthermore, composition analysis of the formed absorber layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorber layer 4 was 60 atomic %, the iridium (Ir) content was 30 atomic %, and the tungsten (W) content was 10 atomic %. 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.

[0077] [Example 7] A reflective photomask blank 10 and a reflective photomask 20 of Example 7 were produced in the same manner as in Example 1, except that the absorbing layer 4 was formed to a thickness of 19 nm.

[0078] [Example 8] An absorber layer 4 containing platinum (Pt), iridium (Ir), and iodine (I) was formed to a thickness of 24 nm on the capping layer 3. Furthermore, composition analysis of the formed absorber layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorber layer 4 was 60 atomic %, the iridium (Ir) content was 20 atomic %, and the iodine (I) content was 20 atomic %. 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.

[0079] [Example 9] An absorption layer 4 containing platinum (Pt), iridium (Ir), and tellurium (Te) was formed to a thickness of 27 nm on the capping layer 3. Furthermore, composition analysis of the formed absorption layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorption layer 4 was 70 atomic %, the iridium (Ir) content was 20 atomic %, and the tellurium (Te) content was 10 atomic %. 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.

[0080] [Example 10] An absorber layer 4 containing platinum (Pt), iridium (Ir), and hafnium (Hf) was formed to a thickness of 26 nm on the capping layer 3. Furthermore, composition analysis of the formed absorber layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorber layer 4 was 80 atomic %, the iridium (Ir) content was 15 atomic %, and the hafnium (Hf) content was 5 atomic %. 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 formation of the absorbing layer 4.

[0081] [Example 11] An absorber layer 4 containing platinum (Pt), iridium (Ir), and indium (In) was formed to a thickness of 33 nm on the capping layer 3. Furthermore, composition analysis of the formed absorber layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content in the entire absorber layer 4 was 70 atomic %, the iridium (Ir) content was 20 atomic %, and the hafnium (Hf) content was 10 atomic %. 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 formation of the absorbing layer 4.

[0082] [Comparative Example 1] The absorbing layer 4 was formed so that the platinum (Pt) content of the absorbing layer 4 was 100 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 33 nm. 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.

[0083] Comparative Example 2 The absorbing layer 4 was formed so that the platinum (Pt) content of the absorbing layer 4 was 45 atomic % of the entire absorbing layer 4, and the iridium (Ir) content of the absorbing layer 4 was 55 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 28 nm. The 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.

[0084] Comparative Example 3 The absorbing layer 4 was formed so that the platinum (Pt) content of the absorbing layer 4 was 30 atomic % of the entire absorbing layer 4 and the iridium (Ir) content was 70 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 36 nm. 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.

[0085] Comparative Example 4 A reflective photomask blank 10 and a reflective photomask 20 of Comparative Example 4 were produced in the same manner as in Example 1, except that the absorbing layer 4 was formed to a thickness of 15 nm.

[0086] Comparative Example 5 A reflective photomask blank 10 and a reflective photomask 20 of Comparative Example 5 were produced in the same manner as in Example 1, except that the absorbing layer 4 was formed to a thickness of 52 nm.

[0087] [Reference example (existing mask)] In addition to the above-mentioned Examples and Comparative Examples, a reflective photomask (existing mask) having an absorption pattern layer composed of TaBO / TaBN, which is a conventional tantalum (Ta)-based absorption pattern layer, 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 stacked films, each consisting of a pair of silicon (Si) and molybdenum (Mo), on a synthetic quartz substrate with 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 film of TaBO deposited on a 58 nm thick TaBN. Moreover, similarly to the above-mentioned Examples and Comparative Examples, the absorber layer 4 was patterned and used for evaluation. In the above-described examples and comparative examples, the film thickness of the absorbing layer 4 was measured using a transmission electron microscope.

[0088] The evaluation items evaluated in this example will be described below. (reflectance) In the above-mentioned examples and comparative examples, the reflectance Ra of the absorption pattern layer 41 region (see FIG. 11) of the fabricated reflective photomask 20 was measured using a reflectance measurement device with EUV light. Also, the reflectance Rm of the reflective portion 8 (see FIG. 11) where the absorption pattern layer 41 was not formed was measured using the reflectance measurement device with EUV light. In this way, the OD values ​​of the reflective photomasks 20 according to the examples and comparative examples were calculated using the above-mentioned formula 1. As mentioned above, if the OD value is less than 1.0, sufficient contrast cannot be obtained and transfer performance deteriorates. Therefore, if the OD value is 1.0 or more, there is no problem with transfer performance and the product was rated as "pass" in this evaluation.

[0089] (processability) In the above-described examples and comparative examples, analysis was performed using an SEM to check for disconnections or missing defects (so-called pattern defects) in the pattern in the absorbing pattern layer 41. In addition, the cross-sectional shape of the pattern in the absorbing pattern layer 41 was also confirmed. If the formed pattern is free of abnormalities, there is no problem with the processing suitability (transfer performance), and this evaluation is marked "pass (△)." Furthermore, if the formed pattern is free of abnormalities and the sidewall angle (the angle of elevation based on the surface of the capping layer 3) confirmed from the cross-sectional image is 80° or greater, there is no problem with the processing suitability (transfer performance), and this evaluation is marked "pass (◯)." Note that if the formed pattern has pattern defects, problems with the processing suitability (transfer performance) may occur, and this evaluation is marked "fail (×)." Regarding the HV bias, because this is the difference in line width of the transferred pattern formed by transferring the mask pattern, transfer evaluation was not performed for patterns that failed to be formed. Therefore, a "-" is indicated in the table.

[0090] (Wafer exposure evaluation) Using an EUV exposure tool (NXE3300B, manufactured by ASML), the absorption patterns 41 of the reflective photomasks 20 produced in the examples and comparative examples were transferred and exposed onto a semiconductor wafer coated with an EUV positive chemically amplified resist. The exposure dose was adjusted so that the x-direction LS pattern shown in FIG. 11 was transferred as designed. Specifically, in this exposure test, the x-direction LS pattern (line width 64 nm) shown in FIG. 11 was exposed so that it had a line width of 16 nm on the semiconductor wafer. The transferred resist patterns were observed and line widths were measured using an electron beam dimension measuring machine, and the changes in the HV bias value were compared by simulation.

[0091] The HV bias value 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.

[0092] The evaluation method was based on the HV bias value of the existing tantalum (Ta)-based photomask shown as "existing mask" in Table 2, and evaluated based on the magnitude of the HV bias value. In other words, 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 using the existing tantalum (Ta)-based photomask, the evaluation 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 the HV bias was larger than when using the existing tantalum (Ta)-based photomask, the evaluation was deemed "fail."

[0093] (Can it be corrected?) A specific method for performing electron beam correction etching on the formed absorbing pattern layer 41 will now be briefly described. First, electron beam correction etching was performed on the outermost absorption pattern layer 41 using an electron beam correction machine (MeRiT MG45, manufactured by Carl Zeiss) by irradiating it with an electron beam in a gas atmosphere containing a mixture of fluorine gas and oxygen. The fluorine gas flow rate was controlled by temperature using a cold trap technique. Specifically, the controlled temperatures during electron beam correction etching were -26°C for fluorine and -43°C for oxygen. The line width of the correction side etching BS generated during the electron beam correction etching was measured using an SEM (LWM9045, manufactured by Advantest). If the correction side etching amount BW was 1 nm or less, it was evaluated as "◎ (pass)," if it was 2 nm or less, it was evaluated as "◯ (pass)," and if it was more than 2 nm, it was evaluated as "× (fail)."

[0094] The evaluation results are shown in Table 1. In addition to the evaluation results, the table also shows the refractive index n and extinction coefficient k.

[0095] [Table 2]

[0096] A comparison of the OD values ​​of each example and each comparative example is shown in Table 2. As mentioned above, when the OD value is less than 1.0, sufficient contrast cannot be obtained, and transfer performance deteriorates. The OD value of a conventional reflective photomask (existing reflective photomask) having a tantalum (Ta)-based absorption pattern layer with a thickness of 60 nm was 1.69, whereas the OD value of the reflective photomask 20 of Example 1 was 2.11, the OD value of the reflective photomask 20 of Example 2 was 1.50, the OD value of the reflective photomask 20 of Example 3 was 1.66, the OD value of the reflective photomask 20 of Example 4 was 1.09, the OD value of the reflective photomask 20 of Example 5 was 1.64, the OD value of the reflective photomask 20 of Example 6 was 1.70, the OD value of the reflective photomask 20 of Example 7 was 1.14, the OD value of the reflective photomask 20 of Example 8 was 1.09, the OD value of the reflective photomask 20 of Example 9 was 1.58, the OD value of the reflective photomask 20 of Example 10 was 1.48, and the OD value of the reflective photomask 20 of Example 11 was 1.79. Furthermore, in the comparative examples, the OD value of the reflective photomask 20 of Comparative Example 1 was 1.74, the OD value of the reflective photomask 20 of Comparative Example 2 was 1.26, the OD value of the reflective photomask 20 of Comparative Example 3 was 1.39, the OD value of the reflective photomask 20 of Comparative Example 4 was 0.64, and the OD value of the reflective photomask 20 of Comparative Example 5 was 1.78. In other words, the OD value of Comparative Example 4 was less than 1.0, and did not meet the criteria for "pass" in this evaluation.

[0097] Table 2 shows a comparison of the processability of each example and each comparative example. As shown in Table 2, it is clear that each of the embodiments of Examples 1 to 11 and Comparative Examples 2 and 3 has excellent processing suitability (transfer performance).

[0098] Table 2 shows a comparison of the HV bias for each example and each comparative example. As a result of patterning with EUV light using a reflective photomask having a conventional tantalum (Ta)-based absorption pattern layer with a thickness of 60 nm, the HV bias was 1.80 nm. In contrast, the HV bias of Example 1 was 0.52 nm, the HV bias of Example 2 was 1.77 nm, the HV bias of Example 3 was 1.60 nm, the HV bias of Example 4 was 1.62 nm, the HV bias of Example 5 was 1.24 nm, the HV bias of Example 6 was 0.94 nm, the HV bias of Example 7 was 1.42 nm, the HV bias of Example 8 was 1.48 nm, the HV bias of Example 9 was 1.54 nm, the HV bias of Example 10 was 1.54 nm, and the HV bias of Example 11 was 1.15 nm.

[0099] In contrast, the HV bias of Comparative Example 2 was 2.01 nm, and as a result of patterning with EUV light, the transferability was worse than that of a conventional tantalum (Ta)-based photomask.Similarly, the HV bias of Comparative Example 3 was 1.93 nm, and as a result of patterning with EUV light, the transferability was worse than that of a conventional tantalum (Ta)-based photomask.

[0100] In Comparative Example 4, the OD value was small, the absorbing layer 4 could not be patterned, and the HV bias could not be measured. In addition, in Comparative Examples 1 and 5, pattern defects occurred in the formed patterns, and therefore the HV bias could not be measured appropriately.

[0101] Table 2 shows a comparison of whether or not each example and each comparative example can be repaired (whether or not repair by electron beam repair etching can be performed). As shown in Table 2, it can be seen that each of Examples 1 to 11 and Comparative Examples 2 to 4 has excellent suitability for electron beam repair (can be repaired by electron beam repair etching).

[0102] Table 2 shows a comprehensive evaluation of the OD value, processability (pattern processability), HV bias, and correctability (processability by electron beam corrective etching). Reflective photomasks 20 that were excellent in all of the OD value, absorber layer processability, HV bias, and electron beam corrective etching processability were marked with a "○" in the "Judgment" column. Reflective photomasks 20 that did not meet the pass criteria in any one of the OD value, absorber layer processability, HV bias, and electron beam corrective etching processability were marked with a "×" in the "Judgment" column. Since conventional tantalum (Ta)-based photomasks were used for comparison, they were marked with a "△" in the "Judgment" column.

[0103] As a result, if the absorption pattern layer 41 is formed from a material that contains platinum (Pt) at 50 atomic % or more relative to the total number of atoms in the absorption pattern layer 41 and iridium (Ir) at a concentration in the range of 5 atomic % to less than 50 atomic % relative to the total number of atoms in the absorption pattern layer 41, the film thickness of the absorption pattern layer 41 is in the range of 17 nm to 50 nm, the OD value (Optical Density) of the absorption pattern layer 41 is 1.0 or more, and the absorption pattern layer 41 is formed from a material that has a fast correction etching rate during electron beam correction, then the optical density (OD value), processability (pattern processability), HV bias, and processability by electron beam correction etching of the absorption layer 4 are all good, and therefore a transfer pattern can be reliably formed on the reflective photomask blank, the projection effect can be reduced, and transfer performance is improved.

[0104] Furthermore, for example, the reflective photomask blank, reflective photomask, and method for manufacturing a reflective photomask according to the present disclosure 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; an absorbing layer formed on the reflective layer, the absorption layer is formed of a material containing platinum (Pt) at 50 atomic % or more with respect to the total number of atoms in the absorption layer, and iridium (Ir) at a concentration in the range of 5 atomic % or more and less than 50 atomic % with respect to the total number of atoms in the absorption layer, the thickness of the absorption layer is in the range of 17 nm to 50 nm, the OD value (Optical Density) of the absorption layer is 1.0 or more, The reflective photomask blank, wherein the absorption layer is formed of a material that has a high correction etching rate during electron beam correction. (2) The reflective photomask blank according to (1) above, wherein the absorption layer is formed from a material containing iridium (Ir) in the range of 20 atomic % to 40 atomic %. (3) The reflective photomask blank according to (1) or (2) above, wherein the absorption layer further contains one or more elements selected from the group consisting of ruthenium (Ru), tantalum (Ta), titanium (Ti), chromium (Cr), indium (In), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), iodine (I), tellurium (Te), zinc (Zn), hafnium (Hf), tungsten (W), palladium (Pd), rhenium (Re), gallium (Ga), aluminum (Al), nitrogen (N), and boron (B). (4) a hard mask on the absorber layer; The reflective photomask blank according to any one of (1) to (3) above, wherein the hard mask has a thickness in the range of 2 nm to 30 nm. (5) The reflective photomask blank according to (4) above, wherein the hard mask is made of one or more selected from the group consisting of ruthenium (Ru), titanium (Ti), chromium (Cr), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), hafnium (Hf), tantalum (Ta), aluminum (Al), and silicon (Si), as well as oxides, nitrides, borides, oxynitrides, oxyborides, and oxynitride boride thereof. (6) The reflective photomask blank according to any one of (1) to (5) above, which has an oxide film on the absorption layer. (7) The reflective photomask blank according to any one of the above (1) to (6), wherein a capping layer is formed between the reflective layer and the absorbing layer. (8) A reflective photomask for pattern transfer using extreme ultraviolet light as a light source, A substrate; a reflective layer including a multilayer film formed on the substrate; an absorbing pattern layer on which an absorbing layer pattern serving as a transfer pattern is formed on the reflective layer, The absorption pattern layer is formed of a material containing platinum (Pt) in an amount of 50 atomic % or more relative to the total number of atoms of the absorption pattern layer, and iridium (Ir) in an amount of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 17 nm to 50 nm, The OD value (Optical Density) of the absorption pattern layer is 1.0 or more, The absorbing pattern layer is a reflective photomask formed of a material that has a high correction etching rate when corrected by an electron beam. (9) The reflective photomask according to (8) above, wherein the absorption pattern layer is formed from a material containing iridium (Ir) in the range of 20 atomic % to 40 atomic %. (10) The reflective photomask according to (8) or (9) above, wherein the absorption pattern layer further contains one or more elements selected from the group consisting of ruthenium (Ru), tantalum (Ta), titanium (Ti), chromium (Cr), indium (In), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), iodine (I), tellurium (Te), zinc (Zn), hafnium (Hf), tungsten (W), palladium (Pd), rhenium (Re), gallium (Ga), aluminum (Al), nitrogen (N), and boron (B). (11) The reflective photomask according to any one of (8) to (10) above, which has an oxide film on the absorption pattern layer and on the side surfaces of the absorption pattern layer. (12) The reflective photomask according to any one of (8) to (11) above, wherein a capping layer is formed between the reflective layer and the absorbing pattern layer. (13) 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; forming an absorbing pattern layer having an absorbing layer pattern to be a transfer pattern on the reflective layer, The absorption pattern layer is formed of a material containing platinum (Pt) in an amount of 50 atomic % or more relative to the total number of atoms of the absorption pattern layer, and iridium (Ir) in an amount of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 17 nm to 50 nm, The OD value (Optical Density) of the absorption pattern layer is 1.0 or more, A method for manufacturing a reflective photomask, wherein the absorbing pattern layer is formed of a material that has a high correction etching rate when corrected by an electron beam. [Industrial Applicability]

[0105] 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. [Explanation of symbols]

[0106] 1...Substrate 2...Reflection layer 3...Capping layer 4...Absorption layer 41...Absorption pattern (absorption pattern layer) 5...Hard mask 10...Reflective photomask blank 20...Reflective photomask 6...Backside conductive film 7...Resist film 71...Resist pattern 8…Reflection part

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; an absorbing layer formed on the reflective layer, the absorption layer is formed of a material containing platinum (Pt) at 50 atomic % or more with respect to the total number of atoms in the absorption layer, and iridium (Ir) at a concentration in the range of 5 atomic % or more and less than 50 atomic % with respect to the total number of atoms in the absorption layer, the thickness of the absorption layer is in the range of 17 nm to 50 nm, the absorbing layer has an OD value (optical density) of 1.0 or more; The reflective photomask blank, wherein the absorption layer is formed of a material that has a high correction etching rate during electron beam correction.

2. 2. The reflective photomask blank according to claim 1, wherein the absorption layer is formed from a material containing iridium (Ir) in a range of 20 atomic % to 40 atomic %.

3. 3. The reflective photomask blank according to claim 1, wherein the absorption layer further contains one or more elements selected from the group consisting of ruthenium (Ru), tantalum (Ta), titanium (Ti), chromium (Cr), indium (In), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), iodine (I), tellurium (Te), zinc (Zn), hafnium (Hf), tungsten (W), palladium (Pd), rhenium (Re), gallium (Ga), aluminum (Al), nitrogen (N), and boron (B).

4. a hard mask on the absorber layer; 3. The reflective photomask blank according to claim 1, wherein the hard mask has a thickness in the range of 2 nm to 30 nm.

5. 5. The reflective photomask blank according to claim 4, wherein the hard mask comprises one or more elements selected from the group consisting of ruthenium (Ru), titanium (Ti), chromium (Cr), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), hafnium (Hf), tantalum (Ta), aluminum (Al), and silicon (Si), as well as oxides, nitrides, borides, oxynitrides, oxyborides, and boron oxynitrides thereof.

6. The reflective photomask blank according to claim 1 or 2, further comprising an oxide film on the absorption layer.

7. 3. The reflective photomask blank according to claim 1, further comprising a capping layer formed between the reflective layer and the absorbing layer.

8. A reflective photomask for pattern transfer using extreme ultraviolet light as a light source, A substrate; a reflective layer including a multilayer film formed on the substrate; an absorbing pattern layer on which an absorbing layer pattern serving as a transfer pattern is formed on the reflective layer, The absorption pattern layer is formed of a material containing platinum (Pt) in an amount of 50 atomic % or more relative to the total number of atoms of the absorption pattern layer, and iridium (Ir) in an amount of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 17 nm to 50 nm, The OD value (Optical Density) of the absorption pattern layer is 1.0 or more, The absorbing pattern layer is a reflective photomask formed of a material that has a high correction etching rate when corrected by an electron beam.

9. 9. The reflective photomask according to claim 8, wherein the absorption pattern layer is formed from a material containing iridium (Ir) in a range of 20 atomic % to 40 atomic %.

10. 10. The reflective photomask according to claim 8, wherein the absorption pattern layer further contains one or more elements selected from the group consisting of ruthenium (Ru), tantalum (Ta), titanium (Ti), chromium (Cr), indium (In), nickel (Ni), cobalt (Co), bismuth (Bi), iron (Fe), gold (Au), silver (Ag), iodine (I), tellurium (Te), zinc (Zn), hafnium (Hf), tungsten (W), palladium (Pd), rhenium (Re), gallium (Ga), aluminum (Al), nitrogen (N), and boron (B).

11. 10. The reflective photomask according to claim 8, further comprising an oxide film on the absorbing pattern layer and on the side surfaces of the absorbing pattern layer.

12. 10. The reflective photomask according to claim 8, further comprising a capping layer formed between the reflective layer and the absorbing pattern layer.

13. 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; forming an absorbing pattern layer having an absorbing layer pattern to be a transfer pattern on the reflective layer, The absorption pattern layer is formed of a material containing platinum (Pt) in an amount of 50 atomic % or more relative to the total number of atoms of the absorption pattern layer, and iridium (Ir) in an amount of 5 atomic % or more but less than 50 atomic % relative to the total number of atoms of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 17 nm to 50 nm, The OD value (Optical Density) of the absorption pattern layer is 1.0 or more, A method for manufacturing a reflective photomask, wherein the absorbing pattern layer is formed of a material that has a high correction etching rate when corrected by an electron beam.

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