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

Abstract

The present invention provides a reflective photomask which can further improve the transfer performance onto a semiconductor substrate, has good pattern processability, and is provided with an absorbing layer which can be subjected to electron beam correction etching; a reflective photomask blank used for manufacturing the reflective photomask; and a method for manufacturing a reflective photomask using the reflective photomask blank. [Solution] A reflective photomask blank 10 according to an embodiment of the present invention has a substrate 1, a reflective layer 2, and an absorbing layer 4, the absorbing layer 4 being formed from a material containing 50 atomic % or more of Pt and 5 atomic % or more but less than 50 atomic % of Ir, the film thickness of the absorbing layer 4 being in the range of 17 nm or more and 50 nm or less, the OD value of the absorbing layer 4 being 1.0 or more, and the absorbing layer 4 being formed from a material with a fast correction etching rate during electron beam correction.

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 manufacturing process of semiconductor devices, the demand for miniaturization of photolithography technology is increasing along with the miniaturization of semiconductor devices. 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 can be. For this reason, the exposure light source is being replaced from the conventional ArF excimer laser light with a wavelength of 193 nm 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 substances, so 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 laminated 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 optics that utilize the transmission of light, so the optical components of the exposure machine are reflective (mirrors) rather than lenses. This creates a problem in that the light incident on the reflective photomask (EUV mask) and the light reflected by the EUV mask cannot be designed to be on the same axis, so EUV lithography normally employs a method in which the optical axis is tilted 6 degrees from the vertical direction of the EUV mask, and the reflected light reflected at an angle of minus 6 degrees is guided to the semiconductor substrate.

[0005] As such, 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 entering 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 performing pattern transfer exposure with an EUV mask fabricated using this mask blank, there is a risk of a decrease in contrast at the shadow 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 inability to form the line width to the targeted dimension, resulting in a deterioration of transfer performance.

[0007] Therefore, reflective photomask blanks are being considered that use a material with high absorbency (extinction coefficient k) for the light absorbing layer instead of tantalum (Ta), or that use a material with high absorbency added to tantalum (Ta). For example, Patent Document 2 describes a method for making a light absorbing layer using Pt, Zn, Au, NiO, Ag, etc. 2 O, Ir, Fe, SnO 2 A reflective photomask blank made of an alloy containing at least two materials selected from the group consisting of Cr, Ni, Co, and the like is described.

[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 (produced), there is a problem that the light absorbing layer on the photomask blank cannot be patterned. In addition, many materials that are highly absorbent to EUV light 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 under the above circumstances, and aims to provide a reflective photomask for patterning transfer using light of a wavelength in the extreme ultraviolet region as a light source, which can further improve the transfer performance to a semiconductor substrate in patterning using light of a wavelength in the extreme ultraviolet region as a light source, has good pattern processability, and is provided with an absorbing layer capable of electron beam correction etching, a reflective photomask blank used for manufacturing the reflective photomask, and a manufacturing method of a reflective photomask using the 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 electron beam correction etching is possible 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 the same, and a manufacturing method of a reflective photomask using the reflective photomask blank. [Means for solving the problem]

[0011] The present disclosure has been made to solve the above-mentioned problems. 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) at 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 within 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 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 having an absorption layer pattern formed on the reflective layer to become a transfer pattern, the absorption pattern layer being 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 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 being within a 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 of a material having a fast correction etching rate during electron beam correction.

[0013] Furthermore, a manufacturing method of a reflective photomask according to one embodiment of the present disclosure is a manufacturing method of a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising the steps of forming a reflective layer including a multilayer film on a substrate, and forming an absorption pattern layer having an absorption layer pattern that becomes 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 of 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 of 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 that has a fast correction etching rate during electron beam correction. Effect of the Invention

[0014] The reflective photomask blank according to one embodiment of the present disclosure allows the creation of an absorbing layer that has good pattern processability and can be etched with electron beam correction. That is, the reflective photomask blank according to one embodiment of the present disclosure allows a fine absorbing layer pattern to be formed in the absorbing layer, and can provide a reflective photomask blank that can be etched with electron beam correction. In other words, the reflective photomask blank according to one embodiment of the present disclosure allows a fine absorbing layer pattern to be formed in the absorbing layer, and compared with the conventional technology, 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, and can provide a reflective photomask blank with an absorbing layer that can be etched with electron beam correction.

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

[0016] Furthermore, the manufacturing method of the reflective photomask according to one embodiment of the present disclosure can manufacture a reflective photomask having an absorbing layer (absorbent pattern layer) that has good pattern processability and can be subjected to electron beam correction etching. That is, the manufacturing method of the reflective photomask according to one embodiment of the present disclosure can form a fine absorbing layer pattern in the absorbing layer, and can manufacture a reflective photomask that can further improve the transfer performance to a semiconductor substrate in patterning using light of a wavelength in the extreme ultraviolet region as a light source, as compared with the conventional technology, and can also be subjected to electron beam correction etching.

[0017] Thus, one aspect of the present disclosure provides a reflective photomask for patterning transfer using light with a wavelength in the extreme ultraviolet region as a light source, which 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 which has good pattern processability and is equipped with an absorption layer capable of 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 description of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view showing a structure of a reflective photomask blank according to an embodiment of the present invention. [Diagram 2]1 is a schematic cross-sectional view showing a structure of a reflective photomask according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing the optical constants of each metal material at the wavelength of EUV light. [Figure 4] 1 is a schematic cross-sectional view showing a side etch after electron beam correction etching of the absorbing pattern layer. [Diagram 5] FIG. 4 is a schematic cross-sectional view showing a structure of a reflective photomask blank according to another embodiment of the present invention. [Figure 6] FIG. 1 is a schematic cross-sectional view showing a structure of a reflective photomask blank according to an embodiment of the present invention. [Figure 7] 1A to 1C are schematic cross-sectional views showing 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 showing 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 showing 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 a 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 PREFERRED EMBODIMENTS

[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. Also, 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 comprises 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. can be used for the substrate 1 according to the embodiment of the present invention. In addition, low thermal expansion glass containing titanium can 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 the EUV light (extreme ultraviolet light) that is the 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 made of a material that is resistant to dry etching 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 made of, 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. Although not shown, a back conductive film can be formed on the surface of the substrate 1 on which the reflective layer 2 is not formed. The back conductive film is a film for fixing the reflective photomask 20 by utilizing the principle of an electrostatic chuck when the reflective photomask 20 is placed in an exposure machine.

[0025] (Absorption layer) As shown in FIG. 2, by removing a part of the absorbing layer 4 of the reflective photomask blank 10, i.e., by patterning the absorbing layer 4, an absorbing pattern (absorbing pattern layer) 41 of the reflective photomask 20 is formed. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 2, but due to a projection effect in which the absorbing pattern 41 obstructs the light path, the transfer performance onto the wafer (semiconductor substrate) may deteriorate. 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 is more absorbent 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 each metal material 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 absorption layer 4, is 0.041. If a compound material has a larger extinction coefficient k, it is possible to make the thickness of the absorption layer 4 thinner than in the past.

[0027] Materials that satisfy the above-mentioned 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 Fig. 3. However, these high extinction coefficient materials often have low volatility of the halide of the constituent element and poor (low) dry etching property, so that processing such as patterning of the absorption layer cannot be performed, or the melting point of the constituent element is low, so that they cannot withstand heat during photomask production or EUV exposure. Therefore, photomasks having an absorption layer formed from the above-mentioned high extinction coefficient materials often have poor practicality as photomasks.

[0028] In order 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 of 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 highly resistant to fluorine-based gases (e.g., CF 4 Gas and SF 6 Gas containing fluorine) or chlorine gas (Cl 2 It is known that platinum (Pt) is difficult to etch with etching gases containing chlorine, such as HCl gas or HCl gas. In this case, the dry etching rate is low, so the thickness of the resist formed on the absorbing layer 4 must be increased, and as a result, it is often difficult to form a fine absorbing layer pattern. In contrast, by mixing platinum (Pt) with iridium (Ir), 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, and as a result, the difficulty of forming the absorbing pattern layer 41, which is made of a high extinction coefficient material and has a fine absorbing layer pattern, can be reduced.

[0029] In general, in dry etching, the introduced gas collides with electrons in the plasma, generating active radicals and reactive ions dissociated into various forms, which causes etching. Therefore, the more volatile products with a low boiling point are formed on the etching surface, the more easily the material is etched, and the boiling point and vapor pressure of the reaction products of 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 it vaporizes, the higher the vapor pressure, and the easier it is to exhaust. In the etching of the absorbing layer 4 in producing the reflective photomask 20, "easily etched by fluorine-based gas" means that the boiling point of at least one fluorine-based compound generated by etching with fluorine-based gas is 300° C. or lower, and "hard to be etched by fluorine-based gas" means that the boiling point of a stoichiometrically possible fluoride generated by etching with fluorine-based gas is higher than 300° C. Similarly, for chlorine-based gas, "easily etched by chlorine-based gas" means that the boiling point of at least one chlorine-based compound generated by etching with chlorine-based gas is 300° C. or lower, and "hard to be etched by chlorine-based gas" means that the boiling point of a stoichiometrically possible chloride generated by etching with chlorine-based gas is higher than 300° C. Therefore, the material used for the absorbing layer 4 is preferably a material that is easily etched by a fluorine-based gas or a chlorine-based gas, that is, a substance having a low boiling point of a fluorine-based compound or a chlorine-based compound.

[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 documents (CRC Handbook of Chemistry and Ohysics, 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 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 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 included 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 described above is merely an index and is not absolute.

[0035] Even if the boiling point of the above-mentioned fluorine-based compound or chlorine-based compound is 300° C. or lower, for example, if the generated fluorine-based compound or chlorine-based compound has a property of easily re-adhering, the above-mentioned etching may not be performed. 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 with respect 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 with respect to the number of atoms constituting the entire absorbing layer 4, more preferably contains platinum (Pt) in the range of 55 atomic % or more and 90 atomic % or less, and even more preferably contains platinum (Pt) in the range of 60 atomic % or more and 80 atomic % or less with respect to the number of atoms constituting the entire absorbing layer 4.

[0037] The absorption layer 4 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 absorption layer 4. This is because, although there is a possibility that the EUV light absorbency may decrease if the absorption layer 4 contains components other than platinum (Pt), if the components other than platinum (Pt) are less than 50 atomic %, the decrease in EUV light absorbency is very slight and there is almost no decrease in performance as the absorption 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, so that a reflective photomask blank can be processed into a reflective photomask. Specifically, if the content of iridium (Ir) contained in the absorption 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 absorption layer 4, the processability of the absorption 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 is performed using fluorine-based gases such as XeF 2 While supplying an etching gas such as fluorine, the etching area is irradiated with an electron beam to promote the reactivity of the fluorine etchant and etch the absorption layer 4.

[0040] However, the etching rate of platinum (Pt) with respect to fluorine-based gas is relatively low, and etching with fluorine-based gas takes an extremely long time. Therefore, as shown in Figure 4, when platinum (Pt) is etched with fluorine-based gas, damage may occur in a direction perpendicular to the etching direction, called correction side etching BS. If the side etching is large, the line width of the part that has been corrected by electron beam etching will be significantly shifted, which is one of the reasons for the correction failure.

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

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

[0043] In addition, in this embodiment, "good pattern processability" refers to a state in which, when the absorbing 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 of the absorbing 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 number of atoms constituting the entire absorber layer 4, both the pattern processability of the absorber layer 4 by dry etching and the processability of electron beam correction etching may not be improved. If the iridium (Ir) content is 50 atomic % or more relative to the number of atoms constituting the entire absorber layer 4, the absorbency of EUV light may decrease, and it may not be possible to thin the absorber layer 4. If the iridium (Ir) content is 50 atomic % or more relative to the number of atoms constituting the entire absorber layer 4, the absorbency of EUV light may decrease, and it may not be possible to thin the absorber layer 4.

[0045] Therefore, the iridium (Ir) content is preferably in the range of 5 atomic % or more and less than 50 atomic % relative 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 ratio of the materials constituting the absorption layer 4 is calculated based on the analysis results by Rutherford backscattering spectrometry (RBS), and the content may vary depending on the analysis method. For example, a material with a platinum (Pt) content of 50 atomic % to 99 atomic % of all metal elements by Rutherford backscattering spectrometry (RBS) may be analyzed to have a platinum (Pt) content of 40 atomic % to 75 atomic % of all metal elements by X-ray photoelectron spectroscopy (XPS), or may be analyzed to have a platinum content of 45 atomic % to 100 atomic % of all metal elements by energy dispersive X-ray spectrometry (EDX).

[0047] The processability of the absorbing 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 absorbing pattern layer 41. For the above reasons, the absorbing layer 4 in this embodiment is desirably formed of an amorphous film with low crystallinity. A material with high crystallinity also has a large surface roughness due to the formation of crystal grain boundaries. Therefore, the surface roughness (RMS) of the absorbing layer 4 is preferably 0.4 nm or less, and more preferably 0.2 nm or less. Here, the "surface roughness (RMS) of the absorbing layer 4" refers to the roughness (RMS) of the surface (surface) of the absorbing layer 4 (absorbing 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) at 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, and 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 absorbing layer 4 may further contain, in addition to platinum (Pt) and tantalum (Ta), one or more elements selected from the above-mentioned group of additive elements.

[0050] For example, by adding tellurium (Te) from among the elements included in the above-mentioned group of additive elements to the absorption layer 4 (absorption pattern layer 41), the absorption property 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 among the elements included in the group of additive elements described above to the absorption layer 4 (absorption pattern layer 41), the processability of the electron beam correction etching decreases compared to the case where other elements are added, but the absorbency against 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 above-mentioned group of additive elements to the absorption layer 4 (absorption pattern layer 41), it is possible to further improve the processability of electron beam correction etching.

[0053] In addition, by adding chromium (Cr), boron (B), or hafnium (Hf) among the elements included in the above-mentioned additive element group to the absorbing layer 4 (absorbing pattern layer 41), it is possible to make the film quality of the absorbing layer 4 (absorbing pattern layer 41) more amorphous. Therefore, it is possible to improve the roughness and in-plane dimensional uniformity of the absorbing 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-mentioned additive element group may be the same as the content of iridium (Ir). That is, the absorption layer 4 and the absorption pattern layer 41 contain platinum (Pt), iridium (Ir), and one or more elements selected from the above-mentioned additive element group, and the total content of the elements included in the above-mentioned 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 above-mentioned additive element group is within a range of 0.9 times or less of the content of iridium (Ir), and even more preferably, the total content of the elements included in the above-mentioned additive element group is within a range of 0.6 times or less of the content of iridium (Ir). With the above-mentioned configuration, the absorption layer 4 can be provided with both excellent pattern processability and electron beam correction etching processability while having excellent transfer performance, and further provided with the various functions described above.

[0055] The OD value of the absorbing pattern layer 41 will be described below. The intensity of reflected light from the reflective portion, which is an area where the reflective layer 2 and the capping layer 3 are exposed after a part of the absorbing layer 4 has been removed, is defined as Rm, and the intensity of reflected light from the absorbing portion, which is an area where the absorbing layer 4 remains, is defined as Ra. The optical density (OD) value, which is an index showing the contrast in light intensity between the reflective portion and the absorbing portion, is defined by (Formula 1). The larger the OD value, the better the contrast and the higher the transferability. If the OD value is less than 1, sufficient contrast cannot be obtained and the transferability tends to decrease. For pattern transfer, it is preferable that OD>1, and more preferably 1.5 or more.

[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] The absorption layer 4 (absorption pattern layer 41) of the conventional EUV reflective photomask has been formed of a compound material mainly composed of tantalum (Ta) as described above. In this case, in order to obtain an OD value of 1 or more, the thickness of the absorption layer 4 needs to be 40 nm or more. The extinction coefficient k of the conventional material is 0.031, but by forming the absorption layer 4 with a compound material mainly composed of platinum (Pt) whose extinction coefficient k is 0.058 by itself, it is possible to thin the thickness of the absorption layer 4 to 17 nm if the OD value is 1 or more. However, the extinction coefficient k of the entire absorption layer 4 varies greatly depending on the mixture ratio of iridium (Ir) to platinum (Pt) and the crystallinity of the formed material, and if the extinction coefficient k of the entire absorption layer 4 is less than 0.049, a sufficient thinning effect cannot be expected in many cases. Therefore, in order to realize a thinner layer than before, the extinction coefficient k of the entire absorption layer 4 is preferably 0.049 or more, and more preferably 0.051 or more.

[0058] Furthermore, if the thickness of the absorption layer 4 exceeds 50 nm, the projection effect will be about the same as that of a conventional absorption layer with a thickness of 60 nm formed from a compound material mainly composed of tantalum (Ta). Also, 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, when the thickness of the absorption layer 4 is within 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 absorption layer formed of a compound material mainly composed of tantalum (Ta).

[0059] The thickness of the absorbing layer 4 is more preferably in the range of 25 nm to 40 nm. If 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 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 absorbing layer. Also, 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. Also, 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] In addition, the above-mentioned oxide film 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 absorbing layer 4. The hard mask 5 according to an embodiment of the present invention, when formed on the absorbing layer 4, has the function of further enhancing the processability of the absorbing 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 when dry etching the absorbing layer 4. That is, when the material containing platinum (Pt) and iridium (Ir), which is the material forming the absorbing 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. Also, when the material containing platinum (Pt) and iridium (Ir), which is the material forming the absorbing 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 includes 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 their oxides, nitrides, borides, oxynitrides, oxyborides, and boron oxynitride compounds. That is, the absorption layer 4 may contain platinum (Pt), iridium (Ir), and one or more elements selected from the group of additive elements described above, 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 boron oxynitrides thereof.

[0064] The hard mask 5 must remain on the absorbing layer 4 until etching of the absorbing 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. 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 within a range of 2 nm to 30 nm, and more preferably within a 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 a reflective photomask blank 10 will be described with reference to FIG. First, as shown in Fig. 6, a reflective layer 2 is formed by stacking 40 layers of a laminate film, each of which is a pair of silicon (Si) and molybdenum (Mo), on a synthetic quartz substrate 1 having low thermal expansion characteristics. The thickness of the reflective layer 2 is 280 nm. Next, on the reflective layer 2, a capping layer 3 made of ruthenium (Ru) was formed as an intermediate film to a thickness of 3.5 nm. Next, an absorption layer 4 containing platinum (Pt) and iridium (Ir) was formed to a thickness of 48 nm on the capping layer 3. A 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 % and the iridium (Ir) content was 30 atomic %.

[0067] Furthermore, when the crystallinity of the absorbing 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 for depositing each film (forming a layer) on the substrate 1. The thickness of each film was controlled by the sputtering time.

[0068] Next, a method for producing the reflective photomask 20 will be described with reference to FIGS. First, as shown in FIG. 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 drawn on the resist film 7 by an electron beam lithography machine (JBX3030: manufactured by JEOL Ltd.). Then, a pre-baking process was performed at 110° C. for 10 minutes, and then a development process was performed by 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. As a result, an absorbing pattern (absorbing pattern layer) 41 was formed in the absorbing layer 4 as shown in FIG.

[0071] Next, the resist pattern 71 was peeled off in a cleaning process, and the reflective photomask 20 of this embodiment was fabricated as shown in Fig. 10. In this embodiment, the absorption pattern 41 formed on the absorption layer 4 includes a 64 nm line-and-space (LS) pattern, a 200 nm line-width LS pattern for measuring the film thickness of the absorption layer using an AFM, and a 4 mm square absorption layer removal portion for measuring the EUV reflectance on the reflective photomask 20 for transfer evaluation. In this embodiment, 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 can 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 of the absorbing layer 4 was 45 atomic % of the entire absorbing layer 4. In addition, the absorbing layer 4 was formed so that the film thickness of the absorbing layer 4 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 of the absorbing layer 4 was 10 atomic % of the entire absorbing layer 4. In addition, the absorbing layer 4 was formed so that the film thickness of the absorbing layer 4 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 have a thickness of 33 nm.

[0076] [Example 6] An absorption layer 4 containing platinum (Pt), iridium (Ir) and tungsten (W) was formed to a thickness of 40 nm on the capping layer 3. In addition, a composition analysis was performed on the formed absorption layer 4 using Rutherford backscattering spectroscopy (RBS), and the platinum (Pt) content in the entire absorption 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 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 absorbing layer 4 containing platinum (Pt), iridium (Ir) and iodine (I) was formed to a thickness of 24 nm on the capping layer 3. In addition, a composition analysis was performed on the formed absorbing layer 4 using Rutherford backscattering spectroscopy (RBS), and the platinum (Pt) content in the entire absorbing 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. In addition, a composition analysis was performed on the formed absorption layer 4 using Rutherford backscattering spectroscopy (RBS), and 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 absorbing layer 4 containing platinum (Pt), iridium (Ir) and hafnium (Hf) was formed to a thickness of 26 nm on the capping layer 3. In addition, a composition analysis was performed on the formed absorbing layer 4 using Rutherford backscattering spectroscopy (RBS), and the platinum (Pt) content in the entire absorbing 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 absorbing layer 4.

[0081] [Example 11] An absorbing layer 4 containing platinum (Pt), iridium (Ir) and indium (In) was formed to a thickness of 33 nm on the capping layer 3. In addition, a composition analysis was performed on the formed absorbing layer 4 using Rutherford backscattering spectroscopy (RBS), and the platinum (Pt) content in the entire absorbing 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. In addition, the absorbing layer 4 was 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 of the absorbing layer 4 was 55 atomic % of the entire absorbing layer 4. In addition, the absorbing layer 4 was formed so that the film thickness of the absorbing layer 4 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 of the absorbing layer 4 was 70 atomic % of the entire absorbing layer 4. In addition, the absorbing layer 4 was formed so that the film thickness of the absorbing layer 4 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. As with the above-mentioned examples and comparative examples, the reflective photomask blank has a reflective layer formed by stacking 40 laminated films each consisting of a pair of silicon (Si) and molybdenum (Mo) on a synthetic quartz substrate having low thermal expansion characteristics, and a ruthenium (Ru) capping layer 3 with a thickness of 3.5 nm, and the absorption layer 4 formed on the capping layer 3 is a film of TaBO with a thickness of 2 nm formed on TaBN with a thickness of 58 nm. Moreover, similarly to the above-mentioned Examples and Comparative Examples, the absorber layer 4 was patterned and used for the evaluation. In the above-mentioned examples and comparative examples, the film thickness of the absorbing layer 4 was measured by 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 manufactured reflective photomask 20 was measured by a reflectance measuring device using 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 by a reflectance measuring device using EUV light. In this way, the OD value of the reflective photomask 20 according to the examples and comparative examples was 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 the transfer performance deteriorates. Therefore, if the OD value is 1.0 or more, there is no problem with the transfer performance, and it was rated as "pass" in this evaluation.

[0089] (processability) In the above-mentioned examples and comparative examples, analysis was performed by SEM to check whether there were any breaks 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 rated it as "pass (△)". If the formed pattern is free of abnormalities and the sidewall angle (angle of elevation based on the surface of the capping layer 3) that can be confirmed from the cross-sectional image is 80° or more, there is no problem with the processing suitability (transfer performance), and this evaluation rated it as "pass (◯)". If the formed pattern has pattern defects, there may be a problem with the processing suitability (transfer performance), and this evaluation rated it as "fail (×)". In addition, with regard to the HV bias, since it is the line width difference of the transferred pattern formed by transferring the mask pattern, transfer evaluation was not performed for those in which the pattern formation failed. Therefore, it is indicated as "-" in the table.

[0090] (Wafer exposure evaluation) Using an EUV exposure tool (NXE3300B, manufactured by ASML), the absorption patterns 41 of the reflective photomask 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 LS pattern in the x direction shown in FIG. 11 was transferred as designed. Specifically, in this exposure test, the LS pattern in the x direction shown in FIG. 11 (line width 64 nm) was exposed so that the line width on the semiconductor wafer was 16 nm. The transferred resist pattern was observed and line width was measured using an electron beam dimension measuring device, and the changes in the HV bias value were compared by simulation.

[0091] The HV bias value is the line width difference of the transfer 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 the evaluation was based on the magnitude of the HV bias value. In other words, 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, it was judged as "passed" in this evaluation. In addition, in a state where the LS pattern in the x direction was adjusted to be transferred as designed, it was judged as "failed" in this evaluation, when it 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] (Can it be modified?) A specific method for performing electron beam correction etching on the formed absorbing pattern layer 41 will now be briefly described. First, the absorption pattern layer 41, which is the outermost layer, was irradiated with an electron beam in a gas atmosphere of a mixture of fluorine gas and oxygen using an electron beam correction machine (MeRiT MG45: manufactured by Carl Zeiss) to perform electron beam correction etching. The flow rate of fluorine gas at this time was controlled by a cold trap technique controlled by temperature. Specifically, the controlled temperature during electron beam correction etching was -26°C for fluorine and -43°C for oxygen. In addition, 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), and 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 the extinction coefficient k.

[0095] [Table 2]

[0096] A comparison of the OD values ​​of each of the Examples and Comparative Examples is shown in Table 2. As described above, when the OD value is less than 1.0, sufficient contrast cannot be obtained, and the transfer performance is reduced. 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. In addition, 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 standard for "pass" in this evaluation.

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

[0098] Table 2 shows a comparison of the HV bias for each of the examples and comparative examples. As a result of patterning by 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 the transferability was worsened as a result of patterning with EUV light compared to the conventional tantalum (Ta)-based photomask. Similarly, the HV bias of Comparative Example 3 was 1.93 nm, and the transferability was worsened as a result of patterning with EUV light compared to the conventional tantalum (Ta)-based photomask.

[0100] In addition, 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 patterns formed, and therefore 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 of the examples and each of the comparative examples. As shown in Table 2, it is clear that each of the embodiments of Examples 1 to 11 and Comparative Examples 2 to 4 has excellent suitability for electron beam correction (correction by electron beam correction etching is possible).

[0102] Table 2 shows the overall evaluation of OD value, processability (pattern processability), HV bias, and correctability (processability by electron beam correction etching). Reflective photomasks 20 that are excellent in all of OD value, processability of the absorbing layer, HV bias, and processability of electron beam correction etching are marked with "○" in the "Judgment" column, and reflective photomasks 20 that do not meet the pass criteria in any one of OD value, processability of the absorbing layer, HV bias, and processability of electron beam correction etching are marked with "×" in the "Judgment" column. Conventional tantalum (Ta)-based photomasks are used for comparison, so they are marked with "△" in the "Judgment" column.

[0103] As a result, if the absorption pattern layer 41 is formed of a material that contains platinum (Pt) at 50 atomic % or more relative to the total atomic number of the absorption pattern layer 41 and iridium (Ir) at a range of 5 atomic % or more and less than 50 atomic % relative to the total atomic number of the absorption pattern layer 41, the film thickness of the absorption pattern layer 41 is in the range of 17 nm or more and 50 nm or less, the OD value (Optical Density) of the absorption pattern layer 41 is 1.0 or more, and the absorption pattern layer 41 is formed of a material with 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 the transfer performance is improved.

[0104] Furthermore, for example, the reflective photomask blank, the reflective photomask, and the 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) in an amount of 50 atomic % or more relative to the total number of atoms of the absorption layer, and containing iridium (Ir) in a range of 5 atomic % or more and less than 50 atomic % relative to the total number of atoms of 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 absorbing layer is 1.0 or more, The absorbing layer is made 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 of 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 over the absorbing layer; The reflective photomask blank according to any one of the above (1) to (3), 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 boron oxynitrides 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 having an absorbing layer pattern formed on the reflective layer to be a transfer pattern; 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 containing iridium (Ir) in a range of 5 atomic % or more and 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 during electron beam correction. (9) The reflective photomask according to (8) above, wherein the absorption pattern layer is formed of 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, having 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 the above (8) to (11), 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 the steps of: 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 containing iridium (Ir) in a range of 5 atomic % or more and 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 during electron beam correction. [Industrial Applicability]

[0105] The reflective photomask according to the present invention can be suitably used for forming 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…Back 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) in a range of 55 atomic % to 90 atomic % to a total number of atoms of the absorption layer, and containing iridium (Ir) in a range of 10 atomic % to 45 atomic % to a total number of atoms of the absorption layer, The thickness of the absorption layer is in the range of 19 nm to 48 nm, The OD value (Optical Density) of the absorbing layer is 1.0 or more, The reflective photomask blank, wherein the absorption layer is an amorphous layer 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 the range of 20 atomic % to 40 atomic %.

3. 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 hard mask over the absorbing 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 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 boron oxynitrides thereof.

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

7. The reflective photomask blank according to claim 1 or 2, 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 to be a transfer pattern is formed on the reflective layer; The absorption pattern layer is formed of a material containing platinum (Pt) in a range of 55 atomic % to 90 atomic % to the total atomic number of the absorption pattern layer, and iridium (Ir) in a range of 10 atomic % to 45 atomic % to the total atomic number of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 19 nm to 48 nm, The OD value (Optical Density) of the absorption pattern layer is 1.0 or more, The absorbing pattern layer is an amorphous layer formed of a material that has a high correction etching rate during electron beam correction.

9. 9. The reflective photomask according to claim 8, wherein the absorption pattern layer is made of 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. 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 the steps of: 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 a range of 55 atomic % to 90 atomic % to the total atomic number of the absorption pattern layer, and iridium (Ir) in a range of 10 atomic % to 45 atomic % to the total atomic number of the absorption pattern layer, The thickness of the absorption pattern layer is in the range of 19 nm to 48 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 an amorphous layer formed of a material that has a high correction etching rate during electron beam correction.

Images