Reflective mask blank

Abstract

To provide a reflective mask blank exhibiting high smoothness and high cleaning resistance.SOLUTION: A reflective photomask blank 10 according to one embodiment of the present disclosure comprises: a substrate 1; a reflective layer 2 that is formed on the substrate 1, has a multilayer structure, and reflects EUV light; and an absorption layer 4 that is formed on the reflective layer 2 and absorbs EUV light. The absorption layer 4 is primarily composed of indium (In), and the absorption layer 4 further contains one or more elements selected from a first group of materials. The absorption layer 4 has a surface roughness of 0.2 nm rms or less, and the absorption layer 4 has a film density of 4.0 g / cm3 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a reflective mask blank. [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 development dimension of the 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 can be. For this reason, the exposure light source in the manufacturing process of cutting-edge semiconductor devices is being replaced from the conventional 193 nm wavelength ArF excimer laser light to 13.5 nm wavelength EUV (Extreme Ultraviolet).

[0003] Since most materials have high optical absorption for EUV, conventional refractive optical systems that use the transmission of light cannot be used, and the optical components of the exposure machine are mirrors instead of lenses. Therefore, the photomask also changes from the conventional transmissive type to a reflective EUV photomask. In addition, since the incident light on the EUV photomask and the reflected light reflected by the EUV photomask cannot be designed to be on the same axis, EUV lithography usually adopts a method in which the optical axis is tilted 6 degrees from the vertical direction of the EUV photomask, and the reflected light reflected at an angle of minus 6 degrees is irradiated onto the semiconductor substrate.

[0004] However, because the optical axis is tilted, the EUV light incident on the EUV photomask casts a shadow on the EUV photomask pattern (the transfer pattern formed on the absorbing layer, the so-called absorbing layer pattern), which can cause a problem called the shadowing effect, which deteriorates the transfer performance. Therefore, the challenge is to reduce the shadowing effect and improve the transfer performance.

[0005] Current EUV photomasks use a tantalum (Ta)-based film with a thickness of 60 to 90 nm as the light absorbing layer. When this EUV photomask is used for pattern transfer exposure, line width errors and pattern position shifts on the wafer may occur depending on the line width, direction, pitch, etc. of the absorbing layer pattern, which may deteriorate the transfer quality. The impact of this projection effect becomes more pronounced as the pattern line width becomes finer.

[0006] To address this issue, a reflective photomask has been proposed that uses a material with a high extinction coefficient k for the absorption layer and forms an absorption layer pattern with a thin film thickness to reduce the projection effect [see, for example, Patent Document 1]. In addition, a reflective photomask has been proposed that has good hydrogen radical resistance and transferability by using a material in which a metal material is added to indium as the material constituting the absorption layer [see, for example, Patent Document 2]. Furthermore, depending on the material used for the absorbing layer of the reflective photomask, there may be a problem that the surface roughness of the absorbing layer becomes large (that is, the smoothness becomes poor) and the cleaning resistance becomes low. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 159785 [Patent Document 2] International Publication No. 2020 / 100632 Summary of the Invention [Problem to be solved by the invention]

[0008] The present disclosure aims to provide a reflective mask blank having an absorption layer that absorbs EUV light with small surface roughness (i.e., good smoothness) and good cleaning resistance. That is, the present disclosure aims to provide a reflective mask blank having high smoothness and high cleaning resistance. [Means for solving the problem]

[0009] The present invention has been made to solve the above-mentioned problems, and a reflective mask blank according to one embodiment of the present invention comprises a substrate, a reflective layer formed on the substrate and having a multilayer film structure for reflecting EUV light, and an absorbing layer formed on the reflective layer for absorbing EUV light, wherein the absorbing layer contains indium (In) as a main material and further contains one or more elements selected from a first material group, the absorbing layer has a surface roughness of 0.2 nmrms or less, and the absorbing layer has a film density of 4.0 g / cm 3 That's all.

[0010] Furthermore, the first material group in the reflective mask blank according to one embodiment of the present invention may be composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au). Furthermore, the first material group in the reflective mask blank according to one embodiment of the present invention may be composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti).

[0011] Moreover, the absorbing layer in the reflective mask blank according to one embodiment of the present invention may contain 50 atomic % or more of indium (In) among metal elements excluding non-metal elements among elements constituting the layer. Moreover, the absorbing layer in the reflective mask blank according to one embodiment of the present invention may contain 60 atomic % or more of indium (In) among metal elements excluding non-metal elements among elements constituting the layer. Moreover, the absorbing layer in the reflective mask blank according to one embodiment of the present invention may contain 70 atomic % or more of indium (In) among metal elements excluding non-metal elements among elements constituting the layer.

[0012] Moreover, the absorbing layer in the reflective mask blank according to one aspect of the present invention may have a surface roughness of 0.15 nmrms or less. Moreover, the absorbing layer in the reflective mask blank according to one aspect of the present invention may have a surface roughness of 0.1 nmrms or less. In addition, the absorbing layer in the reflective mask blank according to one embodiment of the present invention has a film density of 4.0 g / cm 3 It may be more than that. In addition, the absorbing layer in the reflective mask blank according to one embodiment of the present invention has a film density of 5.0 g / cm 3 It may be more than that. Moreover, the reflective mask blank according to one aspect of the present invention may include a capping layer between the reflective layer and the absorbing layer. Effect of the Invention

[0013] The reflective mask blank according to one embodiment of the present disclosure can provide sufficient cleaning resistance and can form an absorbing layer with small surface roughness. In other words, the reflective mask blank according to one embodiment of the present disclosure can provide a reflective mask blank having high smoothness and high cleaning resistance. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing the optical constants of each metal material at a wavelength of 13.5 nm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present disclosure will be described with reference to the drawings. Here, the configurations shown in the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. are different from the actual ones. In addition, the embodiments shown below are examples of configurations for embodying the technical idea of ​​the present disclosure, and the technical idea of ​​the present disclosure is not limited to the materials, shapes, structures, etc. of the components described below. The technical idea of ​​the present disclosure can be modified in various ways within the technical scope defined by the claims described in the claims.

[0016] (Configuration of reflective photomask blank and reflective photomask) Fig. 1 is a schematic cross-sectional view showing the structure of a reflective photomask blank (reflective mask blank) 10 according to an embodiment of the present invention. As shown in Fig. 1, the reflective photomask blank 10 according to the embodiment of the present invention includes a substrate 1, a reflective layer 2 formed on the substrate 1 and having a multilayer film structure for reflecting EUV light, a protective layer (capping layer) 3 formed on the reflective layer 2, and an absorbing layer 4 formed on the protective layer 3 for absorbing EUV light. The reflective photomask (reflective mask) according to the embodiment of the present invention is produced by forming a transfer pattern on the reflective layer 2 of the reflective photomask blank 10 according to the embodiment of the invention. Each layer constituting the reflective photomask blank 10 according to the embodiment of the present invention will now be described in detail.

[0017] (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. 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 produced using the reflective photomask blank 10 according to the embodiment of the present invention by utilizing the principle of an electrostatic chuck when the reflective photomask is placed on an exposure machine.

[0018] (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) as exposure light, and may be a multilayer reflective film made of a combination of materials with significantly different refractive indices for EUV light (i.e., an EUV light reflective film having a multilayer structure). 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 example, for about 40 periods.

[0019] (protective layer) The protective layer 3 according to the embodiment of the present invention is a layer that functions as an etching stopper that prevents damage to the reflective layer 2 when the absorbing layer 4 is etched in creating a photomask. Note that the protective layer 3 may not be formed depending on the material of the reflective layer 2 and the etching conditions. The protective layer 3 is formed of a material that is resistant to dry etching performed in forming a pattern of the absorbing layer 4. For example, the material of the protective layer 3 may be ruthenium (Ru).

[0020] (Absorption layer) As shown in FIG. 1, the absorbing layer 4 is a layer formed on the protective layer 3, and is a layer that absorbs EUV light, which is the exposure light. In addition, the absorbing layer 4 needs to be a film with a smooth outermost surface. This is because if the surface roughness of the absorbing layer 4 is large, it may adversely affect the line edge roughness of the absorbing pattern layer formed to process the photomask blank into a photomask, and the reflection efficiency of EUV light. Therefore, the surface roughness (RMS: root mean square roughness) of the absorbing layer 4 is preferably 0.2 nmrms or less, more preferably 0.15 nmrms or less, and even more preferably 0.1 nmrms or less. The lower limit of the surface roughness (RMS) of the absorbing layer 4 is not particularly limited, but is preferably 0.05 nmrms or more from the viewpoint of the measurement limit. The surface roughness of the absorbing layer 4 may be measured using, for example, an atomic force microscope.

[0021] The procedure for measuring surface roughness (RMS) using an atomic force microscope is described below. The surface of the absorption layer 4 is 20×20 μm, which is not affected by dust, etc. 2 Select 10 points in the range, obtain height data (Zi), and calculate the average value (Zmean). Next, subtract the average value (Zmean) from each height data Zi, and calculate the square of the difference. Divide the sum of these squares by the number of data N, and finally take the square root to obtain the RMS. This can be expressed as Equation 1 below. RMS=sqrt(Σ(Zi-Zmean)^2 / N) (Equation 1) Zi: i-th height data Zmean: Mean value of height data N: Total number of height data

[0022] The absorbing layer 4 needs to be resistant to cleaning. In general, in EUV lithography, SPM is used as a cleaning liquid for resist. SPM is a mixed solution of sulfuric acid and hydrogen peroxide. The etching rate when using an SPM at 80° C. is preferably 0.03 nm / min or less, more preferably in the range of 0.01 nm / min to 0.03 nm / min, and even more preferably in the range of 0.005 nm / min to 0.01 nm / min. If the etching rate is greater than 0.03 nm / min, it is considered that there will be a significant effect on the transfer performance when the photomask blank is processed into a photomask and exposed to light. The etching rate of the absorption layer 4 may be calculated from the results of measurement using an atomic force microscope, for example.

[0023] In the absorbing layer 4, the film density is 4.0 g / cm 3 The film density of the absorbing layer 4 is preferably 4.0 g / cm or more. 3If the film density is less than 4.0 g / cm, the bonding between the components constituting the absorbing layer 4 is unstable and minute cavities exist inside the film, so that sufficient cleaning resistance may not be obtained. On the other hand, although there is no particular upper limit to the film density of the absorbing layer 4, the higher the film density, the more difficult processing by dry etching tends to become. That is, the film density of the absorbing layer 4 is 4.0 g / cm 3 It is preferable that the content is 4.5 g / cm or more. 3 More than 13.0g / cm 3 More preferably, it is within the range of 5.0 g / cm 3 More than 10.0g / cm 3 It is more preferable that the content is within the following range: The film density of the absorbing layer 4 may be calculated from the measurement results of, for example, Rutherford backscattering spectroscopy (RBS).

[0024] The measurement conditions for calculating the RMS using Rutherford backscattering spectrometry (RBS) are shown below. Incident ion: 2.275MeV 4He++ Beam diameter: 1~2mmφ RBS detection angle: Normal angle 160 degrees :Grazing Angle ~108 degrees

[0025] The outermost surface of the absorbing layer 4 may be oxidized by natural oxidation due to reaction with oxygen in the air or by undergoing a blank preparation process such as cleaning treatment. The absorbing layer 4 may have a gradient structure in which the components change stepwise from the surface layer toward the substrate 1 side. In other words, the absorbing layer 4 may have a gradient structure in which the concentrations of the components change stepwise from the outermost surface side toward the substrate 1 side.

[0026] The material constituting the absorption layer 4 includes indium (In) and one or more elements selected from a first material group described later. That is, the absorption layer 4 includes indium (In) as a main material, and includes one or more elements selected from the first material group. Here, the "main material" means an element (material) that is contained in an amount of 50 atomic % or more of all metal elements constituting the absorption layer 4. In other words, 50 atomic % or more of all metal elements constituting the absorption layer 4 are indium (In), and the content of one or more elements selected from the first material group is 50 atomic % or less. That is, the lower limit of the content of indium (In) contained in the absorption layer 4 is 50 atomic % with respect to all metal elements constituting the absorption layer 4, and the upper limit of the content of one or more elements selected from the first material group is 50 atomic % with respect to all metal elements constituting the absorption layer 4.

[0027] In this embodiment, the first material group is preferably composed of platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au), and more preferably composed of platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti). If the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au), the cleaning resistance of the absorption layer 4 can be increased compared to the case where other elements are used. Furthermore, if the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti), the cleaning resistance of the absorption layer 4 can be further improved compared to when other elements are used.

[0028] Of the elements constituting the absorption layer 4, it is preferable that the absorption layer 4 contains indium (In) at 50 atomic % or more, more preferably at 60 atomic % or more, and even more preferably at 70 atomic % or more, of metal elements excluding non-metallic elements. If the absorption layer 4 contains 50 atomic % or more of indium (In) among the metal elements excluding non-metallic elements among the elements constituting the absorption layer 4, the influence of the projection effect can be reduced compared to when other elements are used. Furthermore, if the absorption layer 4 contains 60 atomic % or more of indium (In) among the metal elements excluding non-metallic elements among the elements constituting the absorption layer 4, the influence of the projection effect can be further reduced compared to the case where other elements are used. Furthermore, if the absorption layer 4 contains 70 atomic % or more of indium (In) among the metal elements excluding non-metallic elements among the elements constituting the absorption layer 4, the influence of the projection effect can be further reduced compared to the case where other elements are used.

[0029] Furthermore, the material constituting the absorption layer 4 may contain a material (element) other than indium (In) and the elements of the first material group. The material constituting the absorption layer 4 contains, for example, beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), copper (Cu), germanium (Ge), arsenic (As), strontium (Sr), technetium (Tc), rhodium (Rh), barium (Ba), rhenium (Re), osmium (Os), boron (B), nitrogen (N), etc., which improves roughness, in-plane dimensional uniformity, and in-plane uniformity of the transferred image, and makes the material sufficiently amorphous.

[0030] Furthermore, by containing, for example, silicon (Si), zirconium (Zr), hafnium (Hf), yttrium (Y), lead (Pb), gallium (Ga), or the like, the material constituting the absorption layer 4 is less likely to react with hydrogen radicals, making it possible to obtain a material that is more resistant to hydrogen radicals. In addition, since the material constituting the absorbing layer 4 contains, for example, chromium (Cr), aluminum (Al), etc., when the absorbing layer 4 is patterned to produce a photomask, an oxide film having hydrogen radical resistance can be formed so as to cover the exposed surface of the absorbing layer 4.

[0031] Furthermore, by containing, for example, silicon nitride (SiN) or tantalum oxide (TaO) as the material constituting the absorption layer 4, the material can have high light absorption at wavelengths of 190 nm to 260 nm and can improve the contrast of the inspection light. In addition, the material constituting the absorption layer 4 contains, for example, cobalt (Co), palladium (Pd), molybdenum (Mo), silver (Ag), etc., so that the material has a refractive index n of less than 0.95 for a wavelength of 13.5 nm and can improve the phase shifting properties. Furthermore, by containing, for example, tellurium (Te), tin (Sn), or nickel (Ni) as the material constituting the absorption layer 4, the material can have a high extinction coefficient and can reduce the projection effect. Although examples of the effects of the materials that can be contained in the absorbent layer 4 have been described above, the effects of each material are not limited to the above examples, and each material may have a plurality of effects.

[0032] 2, when the composition of indium (In), which has a relatively large extinction coefficient k, is increased, the absorbing layer 4 can be made of a material capable of reducing the projection effect. In addition, by appropriately adjusting the composition of indium (In) in the absorbing layer 4 to increase the refractive index n, it is also possible to make the material have a high phase shift effect.

[0033] As described above, the present invention provides a semiconductor device that includes at least the substrate 1, the reflective layer 2 that is formed on the substrate 1 and has a multilayer film structure and reflects EUV light, and the absorbing layer 4 that is formed on the reflective layer 2 and absorbs EUV light, the absorbing layer 4 containing indium (In) as a main material and containing one or more elements selected from a first material group, the surface roughness of the absorbing layer 4 being 0.2 nmrms or less, and the film density of the absorbing layer 4 being 4.0 g / cm 3In the case of a reflective photomask blank as described above, the surface roughness of the absorbing layer 4 is small (that is, the smoothness is good) and the cleaning resistance during the production of a reflective photomask is good.

[0034] [Example] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0035] <Example 1> A synthetic quartz substrate with low thermal expansion was used as the substrate. On the substrate, 40 laminated films each consisting of a pair of silicon (Si) and molybdenum (Mo) were formed as a multilayer reflective film (reflective layer). The thickness of the multilayer reflective film was 280 nm. Next, a capping layer (protective layer) was formed on the multilayer reflective film using ruthenium (Ru) to a thickness of 3.5 nm, thereby forming a reflective portion having the multilayer reflective film and the capping layer on the substrate. On the capping layer, an absorbing layer made of indium (In) and tantalum (Ta) having an extinction coefficient k of 0.057 and a refractive index n of 0.936 at a wavelength of 13.5 nm was deposited.

[0036] Next, a back surface conductive film was formed to a thickness of 100 nm using chromium nitride (CrN) on the side of the substrate on which the multilayer reflective film was not formed. In this manner, the reflective photomask blank of Example 1 was produced. The film was formed on the substrate using a multi-target sputtering device. The composition of the absorption layer of Example 1 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Ta.

[0037] <Example 2> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.060 and a refractive index n of 0.935 at a wavelength of 13.5 nm. The reflective photomask blank of Example 2 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorption layer of Example 2 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 60 atomic % In and 40 atomic % Ta.

[0038] <Example 3> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.062 and a refractive index n of 0.934 at a wavelength of 13.5 nm. The reflective photomask blank of Example 3 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorption layer of Example 2 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 70 atomic % In and 30 atomic % Ta.

[0039] <Example 4> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.065 and a refractive index n of 0.933 at a wavelength of 13.5 nm. The reflective photomask blank of Example 4 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorption layer of Example 4 formed as described above was found to be 80 atomic % In and 20 atomic % Ta when measured by Rutherford backscattering spectroscopy (RBS).

[0040] <Example 5> An absorbing layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.068 and a refractive index n of 0.932 at a wavelength of 13.5 nm. A reflective photomask blank of Example 5 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 5 formed as described above was 90 atomic % In and 10 atomic % Ta, as determined by Rutherford backscattering spectroscopy (RBS).

[0041] <Example 6> An absorption layer made of indium (In) and platinum (Pt) was deposited, which has an extinction coefficient k of 0.066 and a refractive index n of 0.915 at a wavelength of 13.5 nm. The reflective photomask blank of Example 6 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 6 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Pt.

[0042] <Example 7> An absorption layer made of indium (In) and niobium (Nb) was deposited, which has an extinction coefficient k of 0.041 and a refractive index n of 0.932 at a wavelength of 13.5 nm. The reflective photomask blank of Example 7 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 7 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Nb.

[0043] <Example 8> An absorbing layer made of indium (In) and titanium (Ti) was deposited, which has an extinction coefficient k of 0.046 and a refractive index n of 0.940 at a wavelength of 13.5 nm. The reflective photomask blank of Example 8 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 8 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Ti.

[0044] <Example 9> An absorption layer made of indium (In) and iridium (Ir) was deposited, which has an extinction coefficient k of 0.060 and a refractive index n of 0.921 at a wavelength of 13.5 nm. The reflective photomask blank of Example 9 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 9 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Ir.

[0045] <Example 10> An absorbing layer made of indium (In) and tungsten (W) was deposited, which has an extinction coefficient k of 0.054 and a refractive index n of 0.932 at a wavelength of 13.5 nm. A reflective photomask blank of Example 10 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 10 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % W.

[0046] <Example 11> An absorption layer made of indium (In) and iron (Fe) was deposited, which has an extinction coefficient k of 0.064 and a refractive index n of 0.934 at a wavelength of 13.5 nm. A reflective photomask blank of Example 11 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 11 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Fe.

[0047] <Example 12> An absorption layer made of indium (In) and ruthenium (Ru) was deposited, which has an extinction coefficient k of 0.050 and a refractive index n of 0.914 at a wavelength of 13.5 nm. A reflective photomask blank of Example 12 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 12 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Ru.

[0048] <Example 13> An absorbing layer made of indium (In) and gold (Au) was deposited, which has an extinction coefficient k of 0.063 and a refractive index n of 0.918 at a wavelength of 13.5 nm. A reflective photomask blank of Example 13 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 13 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 50 atomic % In and 50 atomic % Au.

[0049] <Example 14> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.034 and a refractive index n of 0.964 at a wavelength of 13.5 nm. A reflective photomask blank of Example 14 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Example 14 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 85 atomic % In and 15 atomic % Ta.

[0050] <Comparative Example 1> An absorption layer made of indium (In) having an extinction coefficient k of 0.034 and a refractive index n of 0.967 at a wavelength of 13.5 nm was formed. The reflective photomask blank of Comparative Example 1 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Comparative Example 1 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and found to be 100 atomic % In.

[0051] <Comparative Example 2> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.034 and a refractive index n of 0.965 at a wavelength of 13.5 nm. A reflective photomask blank of Comparative Example 2 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Comparative Example 2 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 90 atomic % In and 10 atomic % Ta.

[0052] <Comparative Example 3> An absorption layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.065 and a refractive index n of 0.933 at a wavelength of 13.5 nm. A reflective photomask blank of Comparative Example 3 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Comparative Example 3 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 40 atomic % In and 60 atomic % Ta.

[0053] <Comparative Example 4> An absorbing layer made of indium (In) and tantalum (Ta) was deposited, which has an extinction coefficient k of 0.069 and a refractive index n of 0.931 at a wavelength of 13.5 nm. A reflective photomask blank of Comparative Example 4 was produced in the same manner as in Example 1, except for the absorbing layer. The composition of the absorber layer of Comparative Example 4 formed as described above was measured by Rutherford backscattering spectroscopy (RBS) and was found to be 95 atomic % In and 5 atomic % Ta.

[0054] In Example 14, Comparative Example 1, and Comparative Example 2, an In target having a lower film density than the In targets used in the other examples was used.

[0055] The evaluation items for the reflective photomask blanks obtained in the examples and comparative examples will be described below.

[0056] (Surface roughness evaluation) The surface roughness was evaluated using the following four levels of "◎", "○", "△", and "×" based on the RMS calculation results using an atomic force microscope. <Evaluation criteria> ◎: Surface roughness is 0.1nmrms or less ○: Surface roughness is greater than 0.1nmrms and less than 0.15nmrms △: Surface roughness is greater than 0.15nmrms and less than 0.2nmrms ×: Surface roughness is greater than 0.2 nmrms Regarding the surface roughness, if it was rated as "△" or higher, there was no problem in using the reflective photomask blank, so it was rated as "pass."

[0057] (Washing resistance evaluation) After immersing the sample in SPM (sulfuric acid: hydrogen peroxide: water = 80:6:14) at 80°C for 10 minutes, the sample was rinsed with running water for 10 minutes. The etching rate of the absorbing layer due to immersion in the cleaning solution was then calculated by measuring the film thickness using an atomic force microscope. As a result, it became clear that there was a certain relationship between the etching rate due to cleaning of the absorbing layer and the film density of the absorbing layer, so the cleaning resistance results were evaluated in two stages, as follows: "○" and "×". Regarding the relationship between the etching rate due to cleaning of the absorbing layer and the film density of the absorbing layer, when the etching rate due to cleaning of the absorbing layer was low, the film density of the absorbing layer tended to be high.

[0058] <Evaluation criteria> ◯: Film density is 4.0g / cm 3 If it is more than ×: Film density is 4.0 g / cm 3 If less than Regarding the film density, if the evaluation was "good", there was no problem in using the reflective photomask blank, so it was judged to be "passed".

[0059] The evaluation results are shown in Table 1.

[0060] [Table 1]

[0061] Table 1 shows the surface roughness of the absorbing layer of each Example and Comparative Example. As mentioned above, if it is more than 0.2 nmrms, it is evaluated as "X" and is considered to be "failed", and if it is less than 0.2 nmrms, it is evaluated as "△" or higher and is considered to be "passed". From this, it is clear that the surface roughness of the reflective photomask blanks of Comparative Example 1 and Comparative Example 3 is 0.3 nmrms and 0.25 nmrms, respectively, which is considered to be "failed", and the other Examples and Comparative Examples are "passed".

[0062] Table 1 shows the etching rate and film density by SPM for the absorbing layers of each Example and Comparative Example. As mentioned above, the film density of 4.0 g / cm 3 If it is less than 4.0g / cm, it will be rated as "×" and deemed a "failure". 3 If the result is 3.50 g / cm or more, the result is evaluated as "good" and the result is deemed to be "passed." Therefore, the film density of the reflective photomask blanks of Comparative Example 1 and Comparative Example 2 is 3.50 g / cm 3 , 3.97g / cm 3 It was clear that the other examples and comparative examples were "passed." In addition, SPM etching rates of greater than 0.03 nm / min were classified as "failed" because they pose problems when using reflective photomask blanks, whereas SPM etching rates of less than 0.03 nm / min were classified as "passed" because they pose problems when using reflective photomask blanks.

[0063] The overall evaluation of the surface roughness and cleaning resistance of the absorbing layer is shown in Table 1. Reflective photomask blanks having small surface roughness, good smoothness, and good cleaning resistance are indicated with "◯" in the "Overall Evaluation" column, and reflective photomask blanks having large surface roughness, poor smoothness, or poor cleaning resistance are indicated with "×" in the "Overall Evaluation" column.

[0064] As a result, the absorption layer contains indium (In) as a main material, and further contains one or more elements selected from platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au), has a surface roughness of 0.2 nmrms or less, and a film density of 4.0 g / cm 3 The reflective photomask blanks described above had good film smoothness and good cleaning resistance.

[0065] The reflective photomask blank of the present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible without departing from the spirit and scope of the invention.

[0066] Furthermore, for example, the present invention can have the following configuration. (1) A substrate; a reflective layer formed on the substrate and having a multilayer structure for reflecting EUV light; an absorption layer formed on the reflective layer and absorbing EUV light; The absorption layer is mainly made of indium (In), the absorbing layer further comprises one or more elements selected from a first group of materials; the absorbing layer has a surface roughness of 0.2 nmrms or less; The absorbent layer has a film density of 4.0 g / cm 3 A reflective mask blank characterized by the above. (2) The reflective mask blank according to (1) above, characterized in that the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au). (3) The reflective mask blank according to (1) above, characterized in that the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti). (4) The reflective mask blank according to any one of (1) to (3) above, characterized in that the absorption layer contains 50 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer. (5) The reflective mask blank according to any one of (1) to (3) above, characterized in that the absorption layer contains 60 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer. (6) The reflective mask blank according to any one of (1) to (3) above, characterized in that the absorption layer contains 70 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer. (7) The reflective mask blank according to any one of (1) to (6) above, wherein the absorber layer has a surface roughness of 0.15 nmrms or less. (8) The reflective mask blank according to any one of (1) to (6) above, wherein the absorber layer has a surface roughness of 0.1 nmrms or less. (9) The absorbent layer has a film density of 4.0 g / cm 3 The reflective mask blank according to any one of (1) to (8) above, characterized in that: (10) The absorbent layer has a film density of 5.0 g / cm 3 The reflective mask blank according to any one of (1) to (8) above, characterized in that: (11) The reflective mask blank according to any one of (1) to (10) above, further comprising a capping layer between the reflective layer and the absorbing layer. (12) A substrate; a reflective layer formed on the substrate and having a multilayer structure for reflecting EUV light; An absorption pattern layer formed on the reflective layer and absorbing EUV light; The absorbing pattern layer is mainly made of indium (In), The absorbing pattern layer further comprises one or more elements selected from a first material group; The absorbing pattern layer has a surface roughness of 0.2 nmrms or less; The absorbing pattern layer has a film density of 4.0 g / cm 3 A reflective mask characterized by the above. (13) The reflective mask described in (12) above, characterized in that the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au). (14) The reflective mask described in (12) above, wherein the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti). (15) The reflective mask described in any one of (12) to (14) above, characterized in that the absorption pattern layer contains 50 atomic % or more of indium (In) among the elements constituting the layer, metal elements excluding non-metal elements. (16) The reflective mask described in any one of (12) to (14) above, characterized in that the absorption pattern layer contains 60 atomic % or more of indium (In) among the elements constituting the layer, metal elements excluding non-metal elements. (17) The reflective mask described in any one of (12) to (14) above, characterized in that the absorption pattern layer contains 70 atomic % or more of indium (In) among the elements constituting the layer, metal elements excluding non-metal elements. (18) The reflective mask according to any one of (12) to (17) above, wherein the absorbing pattern layer has a surface roughness of 0.15 nmrms or less. (19) The reflective mask according to any one of (12) to (17) above, wherein the absorbing pattern layer has a surface roughness of 0.1 nmrms or less. (20) The absorbing pattern layer has a film density of 4.0 g / cm 3 The reflective mask according to any one of (12) to (19) above, characterized in that: (twenty one) The absorbing pattern layer has a film density of 5.0 g / cm 3 The reflective mask according to any one of (12) to (19) above, characterized in that: (twenty two) The reflective mask according to any one of the above (12) to (21), further comprising a capping layer between the reflective layer and the absorbing pattern layer. [Industrial Applicability]

[0067] The reflective photomask blank 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]

[0068] 1...Substrate 2...Reflection layer 3…Protective layer 4…Absorption layer 10...Reflective photomask blank

Claims

1. A substrate; a reflective layer formed on the substrate and having a multilayer structure for reflecting EUV light; an absorption layer formed on the reflective layer and configured to absorb EUV light; The absorption layer is mainly made of indium (In), the absorbing layer further comprises one or more elements selected from a first material group; the absorbing layer has a surface roughness of 0.2 nmrms or less; The absorbing layer has a film density of 4.0 g / cm ３ A reflective mask blank characterized by the above.

2. 2. The reflective mask blank according to claim 1, wherein the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), titanium (Ti), iron (Fe), ruthenium (Ru), and gold (Au).

3. 2. The reflective mask blank according to claim 1, wherein the first material group is composed of the elements platinum (Pt), niobium (Nb), tungsten (W), iridium (Ir), tantalum (Ta), and titanium (Ti).

4. The reflective mask blank according to any one of claims 1 to 3, characterized in that the absorption layer contains 50 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer.

5. The reflective mask blank according to any one of claims 1 to 3, characterized in that the absorption layer contains 60 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer.

6. The reflective mask blank according to any one of claims 1 to 3, characterized in that the absorption layer contains 70 atomic % or more of indium (In) among metal elements excluding non-metal elements among the elements constituting the layer.

7. 4. The reflective mask blank according to claim 1, wherein the absorbing layer has a surface roughness of 0.15 nmrms or less.

8. 4. The reflective mask blank according to claim 1, wherein the absorbing layer has a surface roughness of 0.1 nmrms or less.

9. The absorbing layer has a film density of 5.0 g / cm ３ The reflective mask blank according to any one of claims 1 to 3, characterized in that

10. 4. The reflective mask blank according to claim 1, further comprising a capping layer between the reflective layer and the absorbing layer.

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