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

Abstract

The present invention provides: 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. 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 at% or more and also contains Ir within a range of 5 at% or more but less than 50 at%. The film thickness of the absorption layer (4) is within a range of 17-50 nm. 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.

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.

[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, and therefore 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 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, a reflective photomask blank is being considered in which the light absorption layer is changed from tantalum (Ta) to a material having a high absorbency (extinction coefficient k) for EUV light, or a material having a high absorbency is added to tantalum (Ta). For example, Patent Document 2 discloses a reflective photomask blank in which the light absorption layer is made of Pt, Zn, Au, NiO, Ag ２ O, Ir, Fe, SnO ２ and a reflective photomask blank made of an alloy containing at least two materials selected from the group consisting of Ni, Ni, Co, and the like.

[0008] However, some materials that are highly absorptive of EUV light are difficult to process by dry etching, and even if a photomask blank is formed (fabricated), there is a problem that the light absorbing layer provided on the photomask blank cannot be patterned.Furthermore, many materials that are highly absorptive of EUV light have an extremely slow etching rate when subjected to electron beam repair etching in the defect repair step of the photomask fabrication process, and there is a problem that it is often difficult to repair defects that occur in the light absorbing layer.

[0009] Patent No. 5418293 Special Publication No. 2019-527382

[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 provided 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.

[0011] The present disclosure has been made to solve the above-mentioned problems, and a reflective photomask blank according to one aspect 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 (Optical 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 aspect 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, the absorption pattern layer being formed from 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) in 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 being in the range of 17 nm or more and 50 nm or less; the OD value (Optical Density) of the absorption pattern layer being 1.0 or more; and the absorption pattern layer being formed from a material having a fast correction etching rate during electron beam correction.

[0013] Furthermore, a method for manufacturing a reflective photomask according to one aspect of the present disclosure is 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 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 concentration in the range of 5 atomic % to 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 to 50 nm, the OD value (Optical 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.

[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 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 aspect 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 aspect 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.

[0018] 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 graph showing the optical constants of each metal material at the wavelength of EUV light. FIG. 4 is a schematic cross-sectional view showing side etching after electron beam correction etching of an absorption pattern layer. FIG. 4 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to another 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 manufacturing process of a reflective photomask according to an example of the present invention. FIG. 9 is a schematic cross-sectional view showing the structure of a reflective photomask according to an example of the present invention. FIG. 10 is a schematic plan view showing the shape of a design pattern of a reflective photomask according to an example of the present 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 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.

[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) 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 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 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. The reflective layer 2 including a 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 about 40 periods.

[0024] (Capping Layer) The capping layer 3 according to the embodiment of the present invention is formed from a material that is resistant to the dry etching that is performed when forming a transfer pattern (mask pattern) on the absorption layer 4, and functions as an etching stopper that prevents damage to the reflective layer 2 when etching the absorption layer 4. The capping layer 3 is formed from, for example, Ru (ruthenium). Here, depending on the material of the reflective layer 2 and the etching conditions, the capping layer 3 may not be formed. 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] (Absorbing Layer) As shown in Figure 2, an absorbing pattern (absorbing pattern layer) 41 of the reflective photomask 20 is formed by removing a portion of the absorbing layer 4 of the reflective photomask blank 10, i.e., by patterning the absorbing layer 4. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 2. However, due to a projection effect in which the absorbing pattern 41 obstructs the light path, transfer performance onto the wafer (semiconductor substrate) may be deteriorated. 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.

[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), which is the main material of the conventional absorber layer 4, is 0.041. If a compound material has a larger extinction coefficient k, it will be possible to make the absorber 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 absorber layer, or have low melting points of their constituent elements, making them unable to withstand the heat during photomask fabrication or EUV exposure. For this reason, photomasks having an absorber layer formed from the above-described high extinction coefficient materials often lack practical use as photomasks.

[0028] To avoid the above-mentioned drawbacks, the absorption layer 4 of the reflective photomask blank 10 of this embodiment or the absorption 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 has high resistance to liquids used for cleaning photomasks and also has high resistance to hydrogen radicals, but it is difficult to remove it from fluorine-based gases (e.g., CF ４ Gas and SF ６ fluorine-containing etching gases such as gases) or chlorine-based gases (Cl ２ It is known that platinum (Pt) is resistant to etching by etching gases containing chlorine, such as chlorine-containing gases (etching gases such as chlorine-containing gases or HCl gas). In this case, the low dry etching rate requires that the resist film formed on the absorbing layer 4 be thickened, which often makes it difficult to form a fine absorbing layer pattern. In contrast, by mixing iridium (Ir) with platinum (Pt), the etching rate can be increased while maintaining high hydrogen radical resistance and high cleaning resistance. This allows the resist film thickness on the absorbing layer 4 to be thin, which in turn reduces the difficulty of forming an absorbing pattern layer 41 made of a high extinction coefficient material and having a fine absorbing layer pattern.

[0029] In general, dry etching involves collisions between introduced gas and electrons in plasma, generating active radicals and reactive ions dissociated into various forms, which cause etching. Therefore, the lower the boiling point of volatile products formed on the etched surface, the easier it is to etch. The boiling point and vapor pressure of the reaction products between the material to be etched and the introduced gas are indicators of this. That is, reaction products with lower boiling points are more likely to vaporize, have higher vapor pressure, and are therefore more easily exhausted. In the etching of the absorbing layer 4 during fabrication of the reflective photomask 20, "easily etched by fluorine-based gases" refers to the boiling point of at least one fluorine-based compound produced by etching with a fluorine-based gas being 300°C or lower, and "resistant to etching by fluorine-based gases" refers to the boiling point of a stoichiometrically possible fluoride produced by etching with a fluorine-based gas being higher than 300°C. Similarly, with respect to 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 chlorine-based gases is 300° C. or lower, and "resistant to etching by chlorine-based gases" means that the boiling point of a stoichiometric chloride produced by etching with chlorine-based gases is higher than 300° C. Therefore, it is desirable that the material used for the absorption layer 4 is a material that is easily etched by fluorine-based gases or chlorine-based gases, that is, a substance whose fluorine-based compound or chlorine-based compound has a low boiling point.

[0030] Table 1 shows the boiling points of halogen-based compounds of metals. The values ​​in Table 1 are a compilation of values ​​found in various literature (e.g., CRC Handbook of Chemistry and Ochemicals, 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 of the absorption layer 4 and the processability of electron beam correction etching are slightly reduced, but the value of the extinction coefficient k of the absorption layer 4 (absorption pattern layer 41) can be increased.

[0032]

[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 the two types of fluorine-based gas and chlorine-based gas. In addition to the fluorine-based gas and the 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 the possibility of etching the absorbing layer 4 (the absorbing pattern layer 41) 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 of easily re-adhering. 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 absorbing layer 4 contains platinum (Pt) at 50 atomic % or more relative to the number of atoms constituting the entire absorbing layer 4. Note that the material constituting the absorbing layer 4 preferably contains platinum (Pt) in the range of 50 atomic % or more and 95 atomic % or less relative to the number of atoms constituting the entire absorbing layer 4, more preferably in the range of 55 atomic % or more and 90 atomic % or less, and even more preferably in the range of 60 atomic % or more and 80 atomic % or less.

[0037] The absorber layer 4 also contains 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 absorber layer 4. This is because, although the EUV light absorption may be reduced if the absorber layer 4 contains components other than platinum (Pt), the reduction in EUV light absorption 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 processing by dry etching is difficult with platinum (Pt) alone, 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, thereby enabling the reflective photomask blank to be processed into a reflective photomask. Specifically, if the content of iridium (Ir) contained in the absorber layer 4 is within a range of 5 atomic % or more and less than 50 atomic % with respect 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. The electron beam correction etching is performed using, for example, a fluorine-based gas (XeF ２ ) while supplying an etching gas such as fluorine fluoride, and irradiating the portion to be etched with an electron beam to promote the reactivity of the fluorine etchant, thereby etching the absorption layer 4.

[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 subjected to electron beam repair etching will be significantly shifted, which is one of the reasons for repair failure.

[0041] In this regard, the inventors of the present application have discovered 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 absorption layer 4 improves the electron beam correction etching rate and makes it possible to suppress the correction side etching amount BW to 2 nm or less. In other words, they have discovered 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 film of the 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 film of the 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 % with respect to the number of atoms constituting the entire 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 as determined by Rutherford backscattering spectroscopy (RBS) may be found to contain 40 atomic % to 75 atomic % of all metal elements as a result of analysis using X-ray photoelectron spectroscopy (XPS), or may be found to contain 45 atomic % to 100 atomic % of all metal elements as a result of 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 from an amorphous film with low crystallinity. Materials with high crystallinity also have increased 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 to 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) at 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. As a material other than platinum (Pt) and iridium (Ir), for example, 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), one of the elements included in the group of added elements described above, to the absorption layer 4 (absorption pattern layer 41), the absorption of EUV light can be further improved and the layer can be made even thinner.

[0051] Furthermore, by adding silver (Ag), nickel (Ni), indium (In), or cobalt (Co) from among 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 additional 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. This makes it 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 above-described group of additional elements may be the same as the content of iridium (Ir). That is, the absorbing layer 4 and the absorbing pattern layer 41 contain platinum (Pt), iridium (Ir), and one or more elements selected from the above-described group of additional elements, and the total content of the elements included in the above-described group of additional elements may be equal to or less than the content of iridium (Ir). More preferably, the total content of the elements included in the above-described group of additional elements 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 above-described group of additional elements is within a range of 0.6 times or less the content of iridium (Ir). With the above-described configuration, the absorbing layer 4 can be provided with excellent transfer performance, while also being endowed with both excellent pattern processability and electron beam correction etching processability, and further with the various functions described above.

[0055] The OD value of the absorbing pattern layer 41 will be explained below. 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, is defined as Rm, and the intensity of reflected light from the absorbing portion, which is the region where the absorbing layer 4 remains, is defined as Ra. The optical density (OD) value, which is an index representing the contrast in light intensity between the reflective portion and the absorbing portion, is defined by (Equation 1). The larger the OD value, the better the contrast and high transferability will be obtained. If the OD value is less than 1, sufficient contrast cannot be obtained and transfer performance tends to deteriorate. For pattern transfer, OD>1 is preferable, and 1.5 or more 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 described 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 for the absorber layer 4 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, makes it possible to reduce the thickness of the absorber layer 4 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, if the extinction coefficient k of the entire absorber layer 4 is less than 0.049, a sufficient thinning effect is often not achieved. 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 absorption layer 4 exceeds 50 nm, the projection effect will be similar to that of a conventional absorption layer with a thickness of 60 nm formed from a compound material primarily containing tantalum (Ta). Furthermore, if the thickness of the absorption layer 4 exceeds 50 nm, the pattern processability of the absorption layer 4 and the processability of electron beam correction etching may be reduced. Therefore, the thickness of the absorption layer 4 according to this embodiment is within the range of 17 nm to 50 nm. In other words, if the thickness of the absorption layer 4 is within the range of 17 nm to 50 nm, the projection effect can be sufficiently reduced compared to conventional absorption layers formed from a compound material primarily containing tantalum (Ta), and the transfer performance can be improved.

[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 can be further improved.

[0060] The "main component" mentioned above refers to a component that accounts for 50 atomic % or more of the total number of atoms in the 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 and side surfaces of the absorption pattern layer 41. An oxide film (not shown) may also be formed separately on at least one of the upper surface of the absorption layer 4 or the upper and side surfaces 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) As shown in FIG. 5 , the reflective photomask blank 10 according to an embodiment of the present invention may have a hard mask 5 formed on the 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 enhancing 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 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. That is, the absorption layer 4 may contain platinum (Pt), iridium (Ir), and one or more elements selected from the above-described 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 needs to remain on the absorber layer 4 until etching of the absorber layer 4 is completed. However, if the film thickness of the hard mask 5 exceeds 30 nm, it may be difficult to form a fine pattern. Furthermore, if the film thickness of the hard mask 5 is less than 2 nm, the film thickness of the hard mask 5 may be too thin, making it difficult to form a hard mask 5 having a uniform film thickness. Therefore, the film 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 fabricating a reflective photomask blank 10 will be described with reference to FIG. 6 . First, as shown in FIG. 6 , a reflective layer 2 was formed on a synthetic quartz substrate 1 having low thermal expansion characteristics, with 40 stacked layers each including a pair of silicon (Si) and molybdenum (Mo). The thickness of the reflective layer 2 was 280 nm. Next, a capping layer 3 made of ruthenium (Ru) was formed on the reflective layer 2 as an intermediate film to a thickness of 3.5 nm. Next, an absorbing layer 4 containing platinum (Pt) and iridium (Ir) was formed on the capping layer 3 to a thickness of 48 nm. Composition analysis of the formed absorbing layer 4 using Rutherford backscattering spectroscopy (RBS) revealed that the platinum (Pt) content of the entire absorbing 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 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 the reflective photomask blank 10 of Example 1. A sputtering device was used to form each film (layer) on the substrate 1. The film thickness of each film was controlled by the sputtering time.

[0068] Next, a method for producing a reflective photomask 20 will be described with reference to Fig. 7 to Fig. 10. First, as shown in Fig. 7, a positive chemically amplified resist (SEBP9012, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to a thickness of 120 nm on the absorption layer 4 of the reflective photomask blank 10 by spin coating, 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 absorber layer 4 included a 64 nm line-and-space (LS) pattern on the reflective photomask 20 for transfer evaluation, a 200 nm line-width LS pattern for measuring the film thickness of the absorber layer using an AFM, and a 4 mm square absorber layer removed portion for measuring EUV reflectivity. In this example, the 64 nm line-width LS pattern was designed in each of the x and y directions, as shown in Fig. 11, so that the influence of the projection effect due to EUV irradiation could be 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 was 45 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 36 nm. A reflective photomask blank 10 and a 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. A reflective photomask blank 10 and a 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 %. A reflective photomask blank 10 and a reflective photomask 20 of Example 6 were produced in the same manner as in Example 1, except for the formation of the absorber 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 on the capping layer 3 to a thickness of 24 nm. 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 %. A reflective photomask blank 10 and a reflective photomask 20 of Example 8 were produced in the same manner as in Example 1, except for the formation of the absorber layer 4.

[0079] Example 9 An absorber layer 4 containing platinum (Pt), iridium (Ir), and tellurium (Te) was formed on the capping layer 3 to a film thickness of 27 nm. 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 tellurium (Te) content was 10 atomic %. A reflective photomask blank 10 and a reflective photomask 20 of Example 9 were produced in the same manner as in Example 1, except for the formation of the absorber layer 4.

[0080] Example 10 An absorber layer 4 containing platinum (Pt), iridium (Ir), and hafnium (Hf) was formed on the capping layer 3 to a thickness of 26 nm. 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 %. A reflective photomask blank 10 and a reflective photomask 20 of Example 10 were produced in the same manner as in Example 1, except for the formation of the absorber layer 4.

[0081] Example 11 An absorber layer 4 containing platinum (Pt), iridium (Ir), and indium (In) was formed on the capping layer 3 to a thickness of 33 nm. 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 %. A reflective photomask blank 10 and a reflective photomask 20 of Example 11 were produced in the same manner as in Example 1, except for the formation of the absorber 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 the film thickness of the absorbing layer 4 was 33 nm. A reflective photomask blank 10 and a 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 was 55 atomic % of the entire absorbing layer 4. The absorbing layer 4 was also formed so that its film thickness was 28 nm. A reflective photomask blank 10 and a 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. A reflective photomask blank 10 and a 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. Similar to 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 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 TaBO film formed on a 58 nm thick TaBN film. Also, similar to the above-mentioned Examples and Comparative Examples, a patterned absorption layer 4 was used for evaluation. In the above-mentioned Examples and Comparative Examples, the thickness of the absorption layer 4 was measured using a transmission electron microscope.

[0088] The evaluation items evaluated in this example are described below. (Reflectance) In the above-described 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 for EUV light. The reflectance Rm of the reflective portion 8 (see FIG. 11) where the absorption pattern layer 41 was not formed was also measured using a reflectance measurement device for EUV light. The OD values ​​of the reflective photomasks 20 according to the examples and comparative examples were calculated using the above-described formula 1. As described 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 evaluation was "passed" in this evaluation.

[0089] (Processability) In the above-described examples and comparative examples, SEM analysis was performed to check for the presence of disconnections or missing defects (so-called pattern defects) in the pattern in the absorption pattern layer 41. The cross-sectional shape of the pattern in the absorption pattern layer 41 was also confirmed. If the formed pattern had no abnormalities, it was deemed that there were no problems with processing suitability (transfer performance), and was evaluated as "pass (△)" in this evaluation. Furthermore, if the formed pattern had no abnormalities and the sidewall angle (the angle of elevation based on the surface of the capping layer 3) confirmed from the cross-sectional image was 80° or more, it was deemed that there were no problems with processing suitability (transfer performance), and was evaluated as "pass (◯)" in this evaluation. Note that if the formed pattern had pattern defects, problems with processing suitability (transfer performance) may occur, and this evaluation was evaluated as "fail (×)." Regarding HV bias, since this is the linewidth difference of the transferred pattern formed by transferring the mask pattern, transfer evaluation was not performed for patterns that failed formation. Therefore, "-" is indicated in the table.

[0090] (Wafer Exposure Evaluation) Using an EUV exposure apparatus (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. At this time, 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 changes in the HV bias value were compared by simulation.

[0091] The HV bias value is the line width difference of the transfer pattern that depends 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 that is 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 that is 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 the evaluation was based on the magnitude of the HV bias value. That is, in a state where 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 the existing tantalum (Ta)-based photomask was used, the evaluation was judged to be "pass." In addition, in a state where the LS pattern in the x direction was adjusted to be transferred as designed, the evaluation was judged to be "fail" when the LS pattern was not transferred as designed (the LS pattern in the y direction was not resolved), or when the HV bias was larger than when the existing tantalum (Ta)-based photomask was used.

[0093] (Repairability) A specific method for performing electron beam repair etching on the formed absorption pattern layer 41 will be briefly described. First, the outermost absorption pattern layer 41 was irradiated with an electron beam in a gas atmosphere containing a mixture of fluorine-based gas and oxygen using an electron beam repair machine (MeRiT MG45, manufactured by Carl Zeiss). The fluorine gas flow rate was controlled by a cold trap technique using temperature. Specifically, the controlled temperatures during the electron beam repair etching were −26°C for fluorine and −43°C for oxygen. Furthermore, the repair side etching BS generated during the electron beam repair etching was measured using a SEM (LWM9045, manufactured by ADVANTEST). A repair side etching amount BW of 1 nm or less was evaluated as “◎ (pass),” a side etching amount BW of 2 nm or less was evaluated as “◯ (pass),” and a side etching amount BW of more than 2 nm 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 the extinction coefficient k.

[0095]

[0096] Table 2 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. The OD value of a conventional reflective photomask (existing reflective photomask) having a tantalum (Ta)-based absorption pattern layer with a film thickness of 60 nm is 1.69, whereas the OD value of the reflective photomask 20 of Example 1 is 2.11, the OD value of the reflective photomask 20 of Example 2 is 1.50, the OD value of the reflective photomask 20 of Example 3 is 1.66, the OD value of the reflective photomask 20 of Example 4 is 1.09, and the OD value of the reflective photomask 20 of Example 5 is 1.69. The OD value of the reflective photomask 20 of Example 2 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. That is, Comparative Example 4 had an OD value of less than 1.0, and did not meet the criteria for "pass" in this evaluation.

[0097] A comparison of the processability of each example and each comparative example is shown in Table 2. As shown in Table 2, it can be seen that each of the embodiments of Examples 1 to 11 and Comparative Examples 2 and 3 has excellent processability (transfer performance).

[0098] Table 2 shows a comparison of the HV bias of each example and each comparative example. As a result of patterning with EUV light using a conventional reflective photomask with a tantalum (Ta)-based absorption pattern layer having 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, 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, transferability was worse than that of a conventional tantalum (Ta)-based photomask.

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

[0101] Table 2 shows a comparison of the repairability (repairability by electron beam repair etching) of each example and each comparative example. As shown in Table 2, it can be seen that each of the embodiments 1 to 11 and comparative examples 2 to 4 has excellent suitability for electron beam repair (repairability by electron beam repair etching is possible).

[0102] Table 2 shows a comprehensive evaluation of the OD value, processability (pattern processability), HV bias, and whether or not the mask can be corrected (processability by electron beam correction etching). Reflective photomasks 20 that are excellent in all of the OD value, absorber layer processability, HV bias, and electron beam correction etching processability are marked with "○" in the "Judgment" column, and reflective photomasks 20 that do not meet the pass criteria in any one of the OD value, absorber layer processability, HV bias, and electron beam correction etching processability are marked with "×" in the "Judgment" column. Since conventional tantalum (Ta)-based photomasks were used for comparison, they were marked with "△" 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 configuration: (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 is formed of a material containing platinum (Pt) at 50 atomic % or more with respect to the total number of atoms in the absorbing layer and iridium (Ir) at a concentration in the range of 5 atomic % to less than 50 atomic % with respect to the total number of atoms in the absorbing layer, the film thickness of the absorbing layer is in the range of 17 nm to 50 nm, the OD value (Optical Density) of the absorbing layer is 1.0 or more, and the absorbing layer is formed of a material with a high correction etching rate during electron beam correction. (2) The reflective photomask blank according to (1) above, wherein the absorption layer is formed of a material containing iridium (Ir) in a 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) The reflective photomask blank according to any one of (1) to (3) above, further comprising a hard mask on the absorption layer, the hard mask having a thickness in the range of 2 nm to 30 nm.(5) The reflective photomask blank according to (4) above, 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 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 (1) to (6) above, wherein a capping layer is formed between the reflective layer and the absorption layer. (8) 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 having an absorption layer pattern to be a transfer pattern formed on the reflective layer, 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 5 atomic % or more but less than 50 atomic % relative to the total number of atoms in the absorption pattern layer, wherein the film thickness of the absorption pattern layer is within the range of 17 nm to 50 nm, wherein the OD value (Optical Density) of the absorption pattern layer is 1.0 or more, and wherein the absorption pattern layer is formed of a material that has a high correction etching rate during electron beam correction. (9) The reflective photomask according to (8), wherein the absorption pattern layer is formed of a material containing iridium (Ir) at 20 atomic % to 40 atomic %.(10) The reflective photomask according to (8) or (9), 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), wherein an oxide film is formed on the absorption pattern layer and on a side surface of the absorption pattern layer. (12) The reflective photomask according to any one of (8) to (11), wherein a capping layer is formed between the reflective layer and the absorption pattern layer. (13) 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 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 of 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 and 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 (Optical Density) of the absorption pattern layer is 1.0 or more, and the absorption pattern layer is formed of a material that has a high correction etching rate during electron beam correction.

[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.

[0106] REFERENCE SIGNS LIST 1 substrate 2 reflective layer 3 capping layer 4 absorbing layer 41 absorbing pattern (absorbing pattern layer) 5 hard mask 10 reflective photomask blank 20 reflective photomask 6 back surface conductive film 7 resist film 71 resist pattern 8 reflective 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 is 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) at a concentration in the range of 5 atomic % to less than 50 atomic % relative to the total number of atoms in the absorbing layer, the film thickness of the absorbing layer is in the range of 17 nm to 50 nm, the OD value (Optical Density) of the absorbing layer is 1.0 or more, and the absorbing layer is formed of a material with a high correction etching rate during electron beam correction.

2. A reflective photomask blank according to claim 1, 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 claim 1 or 2, 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 reflective photomask blank according to claim 1 or 2, which has a hard mask on the absorption layer, the film thickness of the hard mask being in the range of 2 nm to 30 nm.

5. The reflective photomask blank according to claim 4, wherein the hard mask is made of 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 products thereof.

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

7. The reflective photomask blank according to claim 1 or 2, 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, 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 to be a transfer pattern is formed on the reflective layer, 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 within the range of 17 nm or more and 50 nm or less, the OD value (Optical Density) of the absorption pattern layer is 1.0 or more, and the absorption pattern layer is formed of a material with a high correction etching rate during electron beam correction.

9. The reflective photomask according to claim 8, wherein said 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 claim 8 or 9, 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 claim 8 or 9, which has an oxide film on the top of said absorbing pattern layer and on the side surfaces of said absorbing pattern layer.

12. The reflective photomask according to claim 8 or 9, 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 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 the transfer pattern on the reflective layer, wherein the absorption pattern layer is formed from a material that contains 50 atomic % or more of platinum (Pt) relative to the total number of atoms in the absorption pattern layer, and iridium (Ir) in 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 within the range of 17 nm or more and 50 nm or less, the OD value (Optical Density) of the absorption pattern layer is 1.0 or more, and the absorption pattern layer is formed from a material that has a high correction etching rate during electron beam correction.

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